Introduction and background
Thirst is described as the “longing for fluids” and is a conscious and subjective experience [1]. It plays a critical role in maintaining the body’s fluid and electrolyte balance. This sensation is not simply a response to dryness in the mouth or throat, but the result of a complex physiological process. Specifically, thirst is regulated by an intricate system of neurohormonal and ionic signaling that monitors changes in the body’s water and sodium levels. When these levels become unbalanced - for example, due to dehydration or elevated sodium concentration - the brain activates the sensation of thirst to prompt fluid intake and restore homeostasis [2]. Those receiving mechanical ventilation are particularly affected, as endotracheal tubes prevent lip closure, contributing to oral dryness and making thirst a prominent, distressing symptom [3]. The magnitude of this issue is supported by data showing that over 70% of critically ill adult ICU patients with high illness severity (APACHE II score ≥20) experience thirst [4]. This finding was observed in patients who had been admitted to the ICU for at least three days with severe conditions such as cardiac/respiratory failure, liver cirrhosis, sepsis with multiple organ dysfunction, or malignancy-associated organ failure. Thirst is also reported by ICU patients to be one of the most frequent and intense symptoms, alongside pain [5], and is recalled by ICU survivors as the most distressing experience during their ICU stay [6].
In 2024, a scoping review of thirst in ICU patients was published [7]. This review summarizes the potential causes, risk factors, diagnostic and measurement tools, potential co-occurrence with other distressing symptoms, and management of thirst in ICU patients. However, the scoping review only included studies that directly measured thirst in ICU patients, excluding those that broadly evaluated stress or discomfort. Therefore, studies that evaluated thirst as a secondary outcome or unexpected finding were not included in the scoping review. Additionally, the scoping review limited its search to publications in English, Norwegian, Swedish, Danish, and Dutch. However, there are numerous reports on thirst published in languages such as Chinese, which indicates that the search may not have been comprehensive. In addition, the scoping review included both thirst as a subjective symptom and objective dry mouth, such as the wetness tester [7]. However, previous research has demonstrated distinct differences between ratings of thirst and dry mouth before and after oral care in intensive care patients [8]. Therefore, our review specifically focused on the concept of thirst, deliberately excluding literature solely addressing dry mouth.
Furthermore, a systematic review of interventions to alleviate thirst reported various strategies, including cooling sprays, cotton swabs, lip moisturizers with menthol, and the use of humidifiers [9]. However, the search did not include various interventions, such as the use of virtual reality. Furthermore, the systematic review covered only intervention studies conducted up to 2020. Although randomized controlled trials addressing thirst have been conducted [10,11], no subsequent systematic review has incorporated this newer evidence. Due to the considerable heterogeneity and lack of consensus in the literature on thirst among ICU patients, we chose to conduct a scoping review. This approach allows for a comprehensive overview of the current body of knowledge, clarifying key themes and evidence gaps that require further investigation.
Therefore, an updated and comprehensive scoping review that includes a broader spectrum of interventions and critically ill patient populations is warranted to identify current gaps between research evidence and clinical practice. In this scoping review, we systematically explored and synthesized the literature on the prevalence of thirst, associated risk factors, assessment tools, intervention strategies, and their reported effects in ICU patients, while also highlighting areas where further research is needed.
Review
Methods
Design and Protocol Registration
This scoping review was conducted following the methods outlined by Arksey and O'Malley [12], the revised recommendations by Levac et al. [13] and Colquhoun et al. [14], and the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) Scoping Review Extension guidelines [15]. The protocol for this study was registered on the Open Science Framework and can be accessed at https://osf.io/czw3n (last registered date: October 23, 2024). The analysis method was considered based on the search results, and the protocol was registered in October during the search.
Research Questions
The research questions were as follows: “What are the characteristics of patients who experience thirst (e.g., demographic, treatment, and physiological factors)?”, “What are the methods to measure thirst?”, “What is the prevalence of thirst during ICU admission?”, “Is there any relationship between the symptom rate and the clinical course of the patients after admission to the ICU?”, “What are the factors of thirst exacerbation and relief?”, and “What interventions are effective for relieving thirst?”
Search Strategy
PubMed, CINAHL, CENTRAL, and Igaku Chuo Zasshi (Ichushi-Web) databases were searched for studies published from their inception to August 2, 2024. The keywords used were thirst, intensive care, and their synonyms. The search strategy is presented in Appendix A.
Eligibility Criteria
The concept of interest was thirst, and literature on dry mouth alone was not included. Because some reports have indicated that dry mouth does not correlate with thirst [8], the present study focused on thirst as a subjective symptom in patients. The inclusion and exclusion criteria are shown in Table 1.
Table 1
Inclusion and exclusion criteria for the scoping review
Inclusion | Exclusion |
(1) Patients: Critically ill adults | (1) Studies describing only dry mouth, without reporting information on thirst |
(2) Concept: Thirst (including causes, risk factors, diagnosis, measurement, symptom intensity, prevalence, interaction, and management) | (2) Publication type: Reviews, case reports, opinion pieces, qualitative studies, books, letters, oral presentations, posters, and studies with only an abstract available |
(3) Context: ICU | |
(4) Study type: Any article discussing thirst and its risk factors, assessment methods, or interventions to alleviate thirst in ICU patients | |
(5) No language limitations | |
(6) No date of publication limitations |
Study Selection and Data Extraction
Citations were uploaded to Rayyan (http://rayyan.qcri.org), and duplicates were removed. The titles and abstracts were independently reviewed by two reviewers during primary screening. For secondary screening, the full text was uploaded to Rayyan, and two reviewers independently evaluated the full text based on the inclusion and exclusion criteria. Any conflicts were discussed and resolved until a consensus was reached. If necessary, a third reviewer was involved for arbitration. Data extraction was standardized, and the study characteristics (author, year of publication, country, language, ICU setting, participants, ventilator management status, study design, study objectives, intervention method, intervention timing, and intervention duration) and main outcomes (symptom rate, thirst intensity, thirst distress, intervention effect, and risk factors) were extracted from each study. Since scoping reviews typically do not include a formal risk of bias assessment [15], we did not perform one in this study.
Data Synthesis
The search results are presented using a PRISMA flow chart. Quantitative data were integrated using descriptive and inferential statistics and are presented in tabular form. The data are summarized in graphical and tabular formats (numerical summaries) and narrative formats (descriptive summaries). Multiple studies were analyzed and synthesized according to the research questions, and the results were summarized. Descriptive statistics for symptom rates and intensity are reported as means (standard errors) and medians (interquartile ranges). Symptom rates were analyzed using the Stata software (version 18; Stata Corp, College Station, TX, USA). The pooled prevalence and 95% CIs were estimated based on the number of events in each group. Heterogeneity between studies was quantified using visual inspection of forest plots, Cochran’s Q statistic (p < 0.05), and the I² statistic. The I² statistic estimates the percentage of observed variability between studies owing to heterogeneity rather than chance, ranging from 0% to 100% (with values of 25%, 50%, and 75% indicating low, moderate, and high heterogeneity, respectively). In this review, I² values exceeding 75% were considered indicative of significant heterogeneity, and a random-effects model was used to adjust for observed variability [16,17].
Results
Study Selection
The search identified 3,150 articles. After screening the titles and abstracts, 89 articles were shortlisted, of which two were not accessible. Thus, 87 full-text publications were assessed for eligibility through a secondary screening. Finally, 53 studies were included in this review. A flowchart of the study selection process is shown in Figure 1.
Figure 1
PRISMA flow diagram of the study selection
CINAHL, Cumulative Index to Nursing and Allied Health Literature; PRISMA, Preferred Reporting Items for Systematic reviews and Meta-Analyses
Study Characteristics
The characteristics of the included studies are presented in Table 2 and Table 3. Twenty studies were conducted in Asia [8,10,11,18-34], 11 in North America [4,6,35-43], one in South America [44], and 21 in Europe [5,45-64]. Thirty-seven of the 53 studies included patients who received mechanical ventilation [4-6,8,19,21-26,29,33,36-39,41-54,56,57,59,60,62,63]. A total of 29 non-intervention studies were included (Table 2) [4-6,8,18-23,35-39,44-57]. A total of 24 studies focused primarily on thirst [8,10,11,18,22,24-31,33,34,37,40,42,43,45,58,59,61,64], 25 studies addressed discomfort and stress in the ICU [4-6,19,20,23,32,35,36,38,39,44,46-53,56,57,59,62,63], and four studies focused on other topics such as delirium [21,54,55,60]. A total of 24 intervention studies were included (Table 3) [10,11,24-34,40-43,58-64]. The types and methods of interventions showed significant heterogeneity. Among the intervention studies, 15 were randomized controlled trials [10,11,24-29,40,41,58-62], and seven were non-randomized trials [30,31,32,34,43,63,64]. One study was a quality improvement project report [42], and the other was a bench study [33].
Table 2
Characteristics of noninterventional studies
ARICU, anesthesiology and reanimation ICU; CAM-ICU, Confusion Assessment Method for the Intensive Care Unit; ECMO, extracorporeal membrane oxygenation; EICU, electronic ICU; GEE, generalized estimating equation; HFNC, high-flow nasal cannula; ICUESS, ICU Environmental Stressor Scale; ICU-SEQ, ICU stressful experience questionnaire; IMV/NIV, invasive mechanical ventilation/noninvasive mechanical ventilation; IPREA, Inconforts des Patients de REAnimation; MICU, medical ICU; MV, mechanical ventilation; NRS, Numeric Rating Scale; RASS, Richmond Agitation Sedation Scale; SICU, surgical ICU; TDS-HF, Thirst Distress Scale for patients with heart failure; VAS, Visual Analog Scale; VV-ECMO/VA-ECMO, veno-venous ECMO/veno-arterial ECMO
First author, year, and country | Study design | Setting | Sample (N) | Inclusion criteria | Research objective | Measurement method and timing | Key results |
Saltnes-Lillegård, 2023, Norway [5] | Observational multicenter study | Six SICUs and MICUs at two facilities | 353 (first day: 195) | Age ≥18, patients who need MV, need for continuous vasoactive therapy, or ICU stay >24 hours | Describe the prevalence, intensity, and distress of five symptoms in ICU patients and investigate possible predictive factors associated with symptom intensity | Symptom intensity: 11-point Likert Scale (NRS), symptom distress: 11-point Likert Scale (NRS), measured daily during ICU stay (seven days) | First day at ICU: 66% reported thirst as the most common symptom and the highest mean intensity score (6.13). Thirst was the most common (64%) and strongest symptom (mean score of 6.05) during the seven days in the ICU. Multivariate GEE analysis showed that analgesic administration (B = 0.88, 95% CI: 0.18-1.59) and sepsis diagnosis (B = 1.71, 95% CI: 0.58-2.84) were associated with increased thirst intensity over a seven-day period. |
Negro, 2022, Italy [45] | Observational study | Mixed ICU, cardiac ICU, and neurosurgery ICU | 220 | Age ≥18, GCS ≥9, spontaneous breathing with tracheal intubation or tracheostomy | Determine the incidence and intensity of thirst in patients admitted to the ICU and its association with airway devices, airway humidification, patients’ characteristics, and therapy | Thirst Intensity: NRS, measured daily during ICU stay | Thirst was seen in 76.1% of observations, with an average of 5.37 in strength. NRS ≥8 was 26.5%, NRS ≥5 was 52.2%, and NRS = 0 was 24.1%. Thirst intensity was predicted by high doses of diuretics (> 100 mg/day), increasing serum sodium concentration, absence of oral hydration, and the presence of xerostomia. |
Doi, 2021, Japan [8] | Observational study | Mixed ICU | 86 | Age ≥20, no disorientation/delirium | Investigate the impact of oral care on thirst perception and dry mouth assessments | Thirst intensity: NRS, measured before and after oral care and every hour until four hours after oral care | Thirst decreased post-oral care but lasted one hour; NRS (thirst intensity) did not correlate with oral moisture or the modified revised oral assessment guide |
Gültekin, 2018, Turkey [46] | Observational study | SICU and ARICU | 98 | Age ≥18, ICU stay ≥24 hours | Describe environmental and psychological stressors affecting ICU patients and determine their priorities | Turkish ICU Environmental Stressor Scale Assessment, Stress: 4-point Likert scale | Thirst was the largest stressor among all patients (average: 2.44). Thirst (mean: 2.61) was also the biggest stressor in postoperative patients. Patients with internal diseases cited thirst as the biggest stressor. |
Saltnes-Lillegård, 2024, Norway [47] | Prospective cohort study | Six mixed ICUs | 353 | Age ≥18, need for IMV/NIV, need for continuous angio-agonists, or need for ICU stay ≥24 hours | Identify and compare subgroups of ICU patients | Five of the 10 symptoms of ESAS, including thirst, were evaluated, measured once daily (up to seven days) | Three symptom classes were identified, and thirst was a common symptom in all classes. Middle-class patients (n = 177, 50.1%) had a high prevalence of thirst and fatigue. |
Sato, 2023, Japan [18] | Prospective cohort study | Mixed ICU | 100 | Age ≥20, GCS ≥14, post-extubation ICU stay ≥24 hours | Assess the effect of post-extubation HFNC on thirst | Thirst Intensity: NRS, measured four and 24 hours after extubation | After adjustment, HFNC was significantly associated with a decrease in thirst intensity at 24 hours after extubation (adjusted OR: 0.14, 95% Cl: 0.04-0.49, p = 0.002) and a decrease in thirst intensity at four hours after extubation (adjusted OR: 0.19, 95% Cl: 0.06-0.60, p = 0.005). |
Kalfon, 2010, France [48] | Prospective cohort study | MICU and SICU | 868 | Adult ICU survivors | Develop and validate the IPREA questionnaire for the assessment of discomfort related to ICU stay | Evaluated for 16 symptoms of IPREA, discomfort: VAS, measured on the day of ICU discharge | Thirst was the fourth highest-scoring discomfort (mean ± SD: 32 ± 34); 17.9% of patients complained of thirst discomfort with a VAS score of ≥ 70. |
Gunnels, 2024, United States [35] | Descriptive cross-sectional study | SICU, EICU, cardiac ICU, and transplant ICU | 180 | Age ≥18, RASS 0, CAM-ICU negative, ICU stay ≥24 hours | Assess patient-reported discomfort among critically ill patients | 18-item IPREA rating, symptom discomfort: 11-point Likert Scale (NRS), single measurement at study enrollment | Of the 18 items, thirst discomfort scores were the third highest (mean: 3.3), which was equivalent to pain. |
Peterson, 2023, United States [36] | Descriptive cross-sectional study | SICU, MICU, transplant ICU, and multispecialty ICU | 114 | Age ≥18, RASS -1 to +1, CAM-ICU negative, use of NIV in the previous 24 hours | Identify the presence, intensity, and distress of symptoms in patients receiving NIV in the ICU using MESAS | MESAS: Yes/no, symptom intensity: 3-point Likert scale, symptomatic distress: 3 -3-point Likert scale, single measurement at study enrollment | Thirst was the most frequently reported (75.4%). Among participants who reported thirst, 47% rated its intensity as severe, and 45% rated its distress as severe. |
Karaer, 2021, Turkey [49] | Descriptive cross-sectional study | SICU | 120 | Age ≥18, ICU stay: 24-72 hours | Determine environmental stressors perceived and their level of satisfaction with nursing care | 4-point Likert Scale with ICUESS, measured after ICU discharge | Thirst was the second highest stressor (mean: 2.79). |
Zengin, 2019, Turkey [50] | Descriptive cross-sectional study | General ICU | 116 | Age ≥18, ICU stay ≥24 hours, GCS assessment orientation: normal | Examine the relationship between stressors and patients’ experiences in the ICU | Intensive Care Experience Scale, stress distress: 5-point Likert scale, measured before ICU discharge | Of the respondents who reported experiencing extreme stress, 50.9% said that it was caused by thirst, which was the most common cause. There was a moderate positive relation between the stressors, noise (r = 0.534; P). |
Takashima, 2017, Japan [19] | Descriptive cross-sectional study | SICU | 96 | Age ≥20, CAM-ICU negative, MV management ≥ 12 hours | Clarify the actual state of stress experience and related factors in ICU patients who have been mechanically ventilated for >12 hours | ICU-SEQ, stress level: 6-point Likert scale, measured before ICU discharge | The combined percentage of patients with moderate to extreme thirst was 76%. The only factor associated with thirst was CRP level at the time of discharge from the ICU (r = 0.23, p = 0.026). |
Stotts, 2015, United States [37] | Descriptive cross-sectional study | MICU, cardiac ICU, and neurosurgery ICU | 353 | Age ≥18, ICU stay ≥ 24 hours, RASS -1 to +1, CAM-ICU negative | Identify predictors of the presence, intensity, and distress of thirst in ICU patients | Thirst intensity: NRS, thirst pain: NRS, measured once at study enrollment | Thirst was predicted by high doses of opioids, high doses of furosemide, selective serotonin reuptake inhibitors, and low ionized calcium. Predictors of thirst intensity: lack of oral fluid intake and diagnosis of digestive disorders; predictors of thirst distress: MV, negative fluid balance, antihypertensive drugs, and gastrointestinal or “other” diagnosis. |
Rose, 2014, Canada [6] | Descriptive cross-sectional study | General ICU | 27 | MV use for >21 days in ICU | Compare ICU and weaning center memories, and examine the link between delusional memories and psychological outcomes | ICU Memory Tool, ICU-SEQ evaluation, measured after discharge from the hospital | Of the 23 people who had memories of both the ICU and the specialized withdrawal center, 16 (70%) remembered feeling thirst in the ICU. Of those 16 (88%), 14 had memories of thirst discomfort. |
Hweidi, 2007, Jordan [20] | Descriptive cross-sectional study | Three cardiac ICUs | 165 | ICU stay ≥24 hours | Identify the principal physical and psychological stressors as perceived in ICUs | ICUESS Assessment, Distress: 4-point Likert scale, measured on the second to third day after ICU discharge | Thirst was the fourth largest factor in stress (mean ± SD: 3.31 ± 0.79). |
Ayllón Garrido, 2007, Spain [51] | Descriptive cross-sectional study | General ICU | 91 | Age ≥18, ICU stay ≥ 3 days | Describe the stressful environmental events | Ballard’s Environmental Stressors Scale, Stress: 4-point Likert scale, measured three days after ICU discharge | Thirst was the most stressful factor, felt by 62.6%. |
Cazorla, 2007, France [52] | Descriptive cross-sectional study | General ICU | 70 | Ventilator management ≥24 hours | Analyze patients’ assessment of the quality of care in the ICU | A nine-item, 20-question questionnaire, questionnaire was sent post-discharge | 54% remembered mechanical ventilation; thirst was the second most common factor that plagued patients in the ICU environment (39%). |
Jelen, 1979, Germany [53] | Descriptive cross-sectional study | SICU and EICU | 30 | ICU stay ≥5 days | Investigate psychological experiences in the ICU | Interview based on questionnaire, measured six to 24 months after ICU discharge | More than 25% of patients experienced strong thirst during ICU stay. |
Krupa, 2021, Poland [54] | Cross-sectional pilot study | Cardiac ICU | 32 | Age ≥18, equipped with VV-ECMO/VA-ECMO | Show the incidence of delirium in patients after ECMO therapy and factors affecting the occurrence of delirium | Thirst intensity: Thirst Intensity Scale (0 points: no thirst, 10 points: unbearable thirst), measured before and after ingestion of ice | There was no association between delirium and thirst during ECMO. The intensity of thirst before administration of the ice piece was 8.34 ± 1.36 (median: 8) and was significantly reduced (p < 0.008) to 7.16 ± 2.05 after the administration of the ice piece. |
Sato, 2019, Japan [21] | Retrospective cross-sectional study | Mixed ICU | 401 | Age ≥18, RASS -1 to +1 | Investigate the association between thirst and delirium | Thirst intensity: NRS (NRS ≥8 is defined as strong thirst), measured at least twice a day | 40.6% of patients experienced strong thirst during their stay in the ICU. Logistic regression analysis showed that patients with persistent strong thirst had a higher risk of delirium than patients without persistent strong thirst (OR = 4.95, 95% CI: 2.58-9.48, p < 0.001). |
Lin, 2023, China [22] | Prospective descriptive study | SICU, EICU, MICU, and cardiac ICU | 301 | Age ≥18, RASS -1 to +1, ICU stay ≥24 hours | Investigate the symptomatic rate of thirst and associated risk factors | Thirst Intensity: NRS, 3-point Likert scale in patients with NRS ≥ 3, one measurement at 6 pm after 24 hours of ICU stay | Thirst was reported by 69.8% patients; Risk factors for thirst: nil per os order (OR = 4.10, 95% CI: 1.44-11.69), surgery (OR = 2.96, 95% CI: 1.11-7.93), high glucose (OR = 3.36, 95% CI: 1.01-11.17), greater disease severity (OR = 1.13, 95% CI: 1.02-1.24). |
Puntillo, 2010, United States [4] | Prospective descriptive study | Two general ICUs | 171 | Age ≥18, ICU stay ≥3 days | Provide a focused, detailed assessment of the symptom experiences of ICU patients at high risk of dying, and evaluate the relationship between delirium and patients' symptom reports | ESAS (10 symptoms): Yes/no, symptom intensity: 3-point Likert scale, Symptomatic distress: 3-point Likert scale, measured up to 14 days, up to seven times every other day | Thirst was the second most common symptom (70.8%) and the strongest symptom (mean intensity: 2.16, SE: 0.087). |
Dessotte, 2016, Brazil [44] | Prospective correlational study | General ICU | 105 | Age ≥18, postoperative patients who underwent coronary artery bypass grafting or mitral valve surgery | Investigate stressors perceived by patients in the immediate postoperative period of cardiac surgery and their association with sociodemographic and clinical characteristics | Portuguese Environmental Stressor Questionnaire Assessment, Stress: 5-point Likert scale, measured within 48 hours after discharge from the ICU | The item “being thirsty” was evaluated as the most stressful (mean ± SD: 2.6 ± 1.0). Thirst was not stressed: 19.0%, moderately stressed: 24.8%, very stressed: 32.4%, extreme stress: 23.8%. |
Siami, 2013, France [55] | Prospective interventional study | ICU | 30 | Septic shock patients | Investigate whether AVP response changes in patients recovering from septic shock | Thirst intensity: VAS, measured before and after osmotic loading | Physiological saline load was performed. Non-responders were defined as those with a slope of the relation between AVP and plasma sodium levels <0.5 ng/mEq, and thirst perception was significantly diminished in non-responders. |
Flim, 2022, Netherlands [56] | Validation study | Mixed ICU | 56 | Age ≥18, RASS -1 to +1, CAM-ICU negative, ICU stay ≥ 24 hours | Determine the validity and reliability of the “TDS-HF” for thirst distress in ICU patients | Thirst intensity: NRS, thirst distress: TDS-HF/NRS, single measurement | Content validity was low, with an item content validity index between 0.25 and 0.75. The simultaneous validity was high, with Spearman’s correlation coefficient between TDS-HF and NRS for thirst distress of 0.71. |
Wang, 2015, China [23] | Retrospective study | Cardiac ICU | 800 | Age ≥18, MV time ≥4 hours | Analyze major complaints from patients during mechanical ventilation after cardiac surgery | Degree of discomfort: VAS, measured within 24 hours of ICU admission | Thirst and dry mouth were among the independent factors that caused discomfort in patients during MV management after cardiac surgery. |
Baumstarck, 2019, France [57] | Secondary analysis | Mixed ICU, SICU, and MICU | 994 | Age ≥18 years, ICU stay ≥3 days | Validate the 18-item version of the IPREA questionnaire | 18-item IPREA rating, Discomfort: VAS, measured on the day of ICU departure | Thirst was one of the three items with the strongest discomfort among the 18 items (mean ± SD: 31 ± 35.04). |
Li, 2006, United States [38] | Pilot study | SICU and EICU | 15 | Age 21-80, orientation: normal, MV ≥ 12 hours | Document the prevalence and intensity of nine symptoms and examine the relationships among these symptoms | Measures of nine symptoms, symptom intensity: NRS, measured daily | Thirst was the strongest of the nine symptoms (mean ± SD: 5.7 ± 3.7); 80% felt thirst, and 40% felt severe (NRS ≥ 7) thirst. |
Nelson, 2001, United States [39] | Prospective study | MICU | 100 | Adult critically ill cancer patients | Characterize the symptom experience of a cohort of ICU patients at high risk for hospital death | ESAS assessment, thirst intensity: 4-point Likert scale | 71% of ESAS respondents reported experiencing moderate-severe unsatisfied thirst. |
Table 3
Characteristics and effectiveness of intervention studies on thirst
↓ = improvement; ↑ = worsening; → = no significant change
ANP, Anesthesiological Questionnaire for patients after anesthesia; COHG, conventional oral hydration; EOH, early oral hydration; HFNO, high-flow nasal oxygen; JCS, Japan Coma Scale; NA, not applicable; RCT, randomized controlled trial; SEDAICU, Stress Factors in Intensive Care Unit Questionnaire; SOFA, Sequential Organ Failure Assessment
First author, year, and country | Study design | Setting | Sample (N) | Inclusion criteria | Research objective | Measurement method | Intervention methods | Intervention frequency and timing | Duration of the intervention | Effect of thirst intensity | Effect of thirst distress |
Gungor, 2024, Turkey [58] | RCT | SICU | 110 (Experimental group: 55/Control group: 55) | Age 18-65, post-abdominal surgery, fasting ≥6 hours, Thirst Intensity NRS ≥ 3 | Investigate the effects of intraoral cold water spray in patients having abdominal surgery | Thirst intensity: NRS; measured at 1, 4, 8, and 16 hours after surgery | Spraying cold water (4°C) (three times per hour) | NRS ≥3 at 1, 4, 8, and 16 hours postoperatively | Postoperative 16 hours | ↓ | NA |
Lian, 2024, China [10] | RCT | SICU | 56 (Experimental group: 28/Control group: 28) | Age 18-80, ICU stay ≥6 hours, fasting after extubation | Assess the effect of ice-cold water spray applied for postoperative thirst and to establish a framework for mitigating thirst in ICU patients | Thirst intensity: NRS, Oral comfort: NRS, measured at 0.5 hours before and after each intervention | After spraying with ice water (0-6°C), moisturize the lips with a cotton swab dipped in paraffin oil | Four times during six hours after extubation | Six hours | ↓ | ↓ |
Wu, 2024, Taiwan [24] | RCT | MICU | 36 (cold saline spray group: 18/cold distilled water spray group: 18) | Age ≥20, RASS -1 to +1, during tracheal intubation, MV ≥ 24 hours, thirst intensity NRS ≥ 3 | Compare the effectiveness of cold saline spray and cold distilled water spray in relieving thirst in patients with endotracheal tubes placed in the ICU | Thirst intensity: NRS, measured before and after three interventions | Each intervention is 15 minutes. Cold saline group: spray cold saline (2-8°C), Cold distilled water group: spray cold distilled water (2-8°C) | Three times between 20:00 and 22:30, with an interval of 30 minutes | Three days | ↓ | NA |
Luo, 2023, China [25] | RCT | Mixed ICU | 113 (Group A: 38/Group B: 39/Group C: 36) | Age 18-80, RASS -1 to +1, oral tracheal intubation time ≥24 hours, Thirst intensity NRS ≥3 | Investigate the effect of different doses of ice water spray on thirst degree and complications in ICU patients with MV | Thirst intensity: NRS, thirst distress: Thirst Distress Scale (0: no pain to 10: very painful), measured every four hours during the intervention time (post-intervention) | Group A: infusion of 1.5 mL of room temperature drinking water into the oral cavity, Group B: spray 1.5 mL ice water (0-4°C) into the oral cavity, Group C: spray 0.5 mL ice water (0-4°C) into the oral cavity | Every two hours, between 7:00 and 23:00 | Until extubation (two to three days) | ↓ | ↓ |
Ding, 2023, China [26] | RCT | SICU | 80 (Intervention group: 40/Control group: 40) | Post-surgery, ICU stay ≥48 hours, oral tracheal intubation, thirst intensity NRS ≥3 | Determine the clinical efficacy of an intervention using a combination of wiping and spraying with peppermint alcohol solution for ICU patients | Thirst intensity: NRS, thirst distress: Thirst Distress Scale, measured before and 24 hours after intervention | Oral care with cold peppermint alcohol solution, oral spraying of cold menthol solution, application of menthol lip balm on the lips | Oral care: every six hours, start spraying and lip moisturizing after extubation (seven times/day) | 48 hours | ↓ | ↓ |
Lin, 2022, China [27] | RCT | Cardiac ICU | 145 (Group A: 47/Group B: 47/Control group: 49) | Patients who underwent cardiac surgery and received MV | Evaluate the safety, feasibility, and effects of a spray-based oropharyngeal moisturizing program for cardiac surgery patients following endotracheal extubation | Thirst intensity: NRS, thirst discomfort: numerical rating from 0 to 14; measured before intervention, three hours after extubation, and six hours after extubation | Group A: low-temperature cooling spraying, Group B: low to normal temperature spraying (both Group A and Group B sprayed twice an hour), control group: if the patient complained of thirst, oral moisturizer was applied with a moistened cotton swab. | Intervention starts between zero and six hours after extubation. Intervention two times/hour, then at the patient’s request | During the first six hours of intervention | ↓ | ↓ |
Liang, 2022, China [28] | RCT | Cardiac ICU | 84 (EOH group: 39/COH group: 41) | Age ≥18, postoperative cardiac surgery | Investigate the effect of oral rehydration one hour after extubation in patients undergoing cardiac surgery | Thirst intensity: NRS, measured before intervention and every hour after extubation (four hours) | EOH group: 30 mL of warm water one hour after extubation, followed by drinking 50 mL of warm water per hour for four hours, COH group: no oral intake for four hours after extubation | One to four hours after extubation | Four hours after extubation | ↓ | NA |
Zhang, 2022, China [11] | RCT | Mixed ICU | 61 (Experimental group: 31 people/Control group: 30 people) | Age ≥18, ICU stay ≥24 hours, during fasting management, thirst intensity NRS ≥ 3 | Demonstrate the effectiveness of an intervention bundle to relieve thirst and dry mouth | Thirst intensity: NRS, measured at 8:00 am before intervention and at 6:00 pm after intervention (three days) | Experimental group: intervention bundle, vitamin C spray, mouthwash with 40°C peppermint water, lip moisturizer (main ingredient: glycerin); control group: placebo group, saline spray, mouthwash with 40°C mouthwash, lip moisturizer with water | Spray: every hour, mouthwash: once at 2 pm, lip moisturizer: every two hours | Three days (8 am to 6 pm) | ↓ | NA |
Merliot-Gailhoustet, 2022, France [59] | Crossover RCT | SICU | 60 (50 completed all relaxations) | Age ≥18, RASS ≥0, CAM-ICU negative, SOFA score ≥3 | Assess the impact of different electronic relaxation devices on common stressful patient symptoms experienced in the ICU | Thirst intensity: NRS, measured before and after each intervention | Four relaxation sessions in a crossover design: standard relaxation (TV/radio), music therapy, real video images (VR system), and synthetic video images (VR system) | At least one hour washout time between each session | 15 minutes for each session | → | NA |
Zhang, 2021, China [29] | RCT | Mixed ICU | 60 (Observation group: 30/Control group: 30) | Age 18-80, RASS -1 to +1, Oral tracheal intubation ≥24 hours, thirst intensity NRS ≥3 | Investigate the effect of ice water spray on thirst in patients undergoing transoral intubation | Thirst intensity: NRS, measured daily after seven interventions | Observation group: spray of ice-sterilized water (0-6°C), Control group: lip moisturizer with a swab soaked in water | Seven times/day and at the patient’s request | Until extubation | ↓ | NA |
Ford, 2020, United States [40] | RCT | Cardiac ICU | 149 (Early oral hydration group: 75/Usual group: 74) | Postoperative cardiothoracic surgery | Determine the effect of early oral hydration on adverse events and thirst in patients after cardiothoracic surgery | Thirst intensity: NRS; measured immediately after extubation, six hours after extubation and 12 hours after extubation | Early oral fluid intake group: patients who meet criteria ingest ice chips two hours after extubation, are evaluated using a swallowing protocol three hours after extubation, and begin drinking if possible, Usual care group: fasting for six hours after extubation | Started two hours after extubation | Post-extubation to six hours post-extubation | ↓ | NA |
Şavluk, 2017, Turkey [60] | RCT | Cardiac ICU | 152 (Intervention group 1: 38/Intervention group 2: 37/Intervention group 3: 38/Control group: 39) | Patients who received a coronary artery bypass graft at scheduled surgery | Determine the impact of oral intake of carbohydrate-rich beverages before surgery in patients undergoing coronary artery bypass surgery | Thirst intensity: VAS; measured preoperatively, after preoperative induction, after postoperative ICU admission, six hours after ICU admission, and on postoperative day 1 | Consumption of carbohydrate-rich beverages, Intervention group 1: 800 mL eight hours before surgery, 400 mL two hours before surgery; Intervention group 2: 400 mL eight hours before surgery; Intervention group 3: 400 mL two hours before surgery | Eight to 12 hours before surgery | Preoperative period | ↓ | NA |
Lemiale, 2015, France [61] | RCT | 4 ICUs | 100 (HFNO group: 52/Venturi mask group: 48) | Age ≥18, patients with hypoxic acute respiratory failure and immunosuppression | Compare HFNO and Venturi mask oxygen in immunocompromised patients with acute respiratory failure | Thirst intensity: VAS; measured one and two hours after the start of oxygen therapy | HFNO group: oxygen administration with HFNO using a humidifier Venturi mask group: oxygen administration without humidification | Started at the beginning of oxygen therapy | Start of oxygen therapy two hours after | → | NA |
Puntillo, 2014, United States [41] | RCT | SICU, cardiac ICU, neurological ICU | 252 (intervention group: 127/Control group: 125) | RASS -1 to +1, ICU stay ≥24 hours, thirst intensity or thirst distress NRS ≥3 | Test an intervention bundle for thirst intensity, thirst distress, and dry mouth in ICU patients | Thirst intensity: NRS, thirst distress: NRS, measured before and after intervention | Bundle for 15 minutes (3-4°C cold water swabs, cold water spray, mentholated moisturizer on lips) | Three times between 10:00 and 18:00 | One to two days | ↓ | ↓ |
Iblher, 2011, Germany [62] | RCT | Cardiac ICU | 126 (Intervention Group 1: 25/Intervention Group 2: 25/Intervention Group 3: 24/Intervention Group 4: 27/Control group: 25) | After scheduled open chest surgery, on MV, sedation with propofol | Examine the influence of music intervention in the early postoperative period on patients undergoing open heart surgery | Thirst intensity: the ANP, measured on the third postoperative day | Intervention Group 1: 60 minutes of music with headphones immediately after ICU admission, Intervention Group 2: no music with headphones immediately after ICU admission, Intervention Group 3: 60 minutes of music on headphones immediately after sedation was discontinued, Intervention Group 4: no music with headphones immediately after discontinuation of sedation | Intervention group 1/2: start after ICU admission, Intervention group 3/4: start after sedation is discontinued | 60 minutes | ↑ | NA |
Feng, 2021, China [30] | Quasi-experimental study | SICU | 183 (Observation 1 group: 61/Observation 2 group: 61/Control group: 61) | Postoperative gastrointestinal surgery, patients who were aware and able to communicate | Investigate the efficacy and feasibility of intermittent oxygen-driven humidification for the relief of thirst in postoperative gastrointestinal patients in the ICU | Thirst intensity: NRS; measured immediately after ICU admission, 10 minutes after admission, and four, eight, and 12 hours after admission | 0.45% sodium chloride heated, 5 mL extracted, added to a spray inhaler mask, and humidified oxygen inhalation for 15 minutes (oxygen flow rate 6-8 L/min) | Group 1: immediately after admission and four hours later, Group 2: immediately after admission and four, eight, and 12 hours later | 12 hours from ICU admission | ↓ | NA |
Sharma, 2020, India [31] | Quasi-experimental study | Mixed ICU | 40 (Experimental group: 20/Control group: 20) | Critically ill patients with thirst and dry mouth | Validate the effectiveness of the Thirst Bundle on thirst and dry mouth among patients admitted to the ICU | Thirst intensity: categorical Thirst Intensity Scale, measured before and after intervention | Intervention group: sterile cold water swab, sterile ice cold water, sterile menthol water spray | 10 minutes for three consecutive days | Three days | ↓ | NA |
Leemhuis, 2019, United States [42] | Prospective quality improvement project | SICU | 136 (nurse intervention: 123/family intervention: 13) | ― | Implement a research-based thirst intervention performed by ICU nurses and patients’ family members | Thirst intensity: NRS or Word Scale (0 to 3) or Yes/No, measured immediately before and after intervention | Bundle (repeated mouth swabs and sprays of ice-cold water and the application of a moisturizer containing spearmint, including menthol, to the lips and tongue) | Alternated the thirst intervention and the usual oral care | ― | ↓ | NA |
VonStein, 2019, United States [43] | Quasi-experimental study | Two MICUs | 103 patient analysis (Intervention group: 62/Control group: 41) | ICU stay ≥ 12 hours, RASS -1 to +1, Thirst intensity or Thirst distress NRS ≥ 3, Assignment by unit | Evaluate the effectiveness of the scheduled use of ice water oral swabs and lip moisturizer with menthol compared with unscheduled use | Thirst intensity: NRS, thirst distress: NRS, measured seven hours after intervention | Intervention group (planned intervention): wiping with ice water oral swabs and applying mentholated moisturizing lip balm to lips, control group (unplanned intervention): unplanned implementation upon patient request | Every hour between 10:00 and 17:00 | Seven hours | ↓ | ↓ |
Noda, 2019, Japan [32] | Quasi-experimental study | SICU | 38 (Intervention group: 28/Control group: 10) | Scheduled surgery, GCS: E4V5 | Verify whether providing information about ICU environment to patients who are scheduled to be admitted to ICU in advance, using leaflets, will reduce their anxiety and environmental stress after admission | Original questionnaire about environmental stress, Stress level: 4-point Likert scale, measured in the general ward after discharge from ICU | Explain ICU (environment, lights out time, pain time, etc.) using leaflets with pictures and illustrations | Before surgery | Before surgery | NA | ↓ |
Pagnucci, 2019, Italy [63] | Non-controlled pre-post study | SICU, EICU, and MICU | 74 | GCS ≥ 13, ICU stay ≥2 nights, Ramsay sedation score ≥2 | Identify if complementary interventions affected conscious intensive care patients’ perception of stress factors and quality of sleep | Measured by SEDAICU, Degree of stress: 4-point Likert scale, Frequency of stressors: 3-point Likert scale, Measured on the first and second night | 20 minutes of combined aromatherapy and massage care, and music or nature sounds throughout the night | Music or nature sounds: all night long, massage and aromatherapy: 20 minutes | All night long | NA | → |
Oto, 2011, Japan [33] | Bench study | Mixed ICU | 23 (NIV Heated Humidifier Setting Max group: 11/Med group: 12) | Age ≥20, patients with acute respiratory failure, NIV ≥24 hours | Investigate factors related to humidification during NIV | Thirst intensity: NRS, measured at the start of NIV, 12 and 24 hours later, and 12 and 24 hours after discontinuation of NIV | Max group: NIV heated humidifier set to maximum setting (Level 9 setting), Med group (Control group): Set to level 5 | At the start of NIV use | NIV started - NIV stopped | → (Med group:↑) | NA |
Roca, 2010, Spain [64] | Prospective comparative study | Mixed ICU | 20 | Patients with acute respiratory failure, GCS:15 | Compare the comfort of oxygen therapy via high-flow nasal cannula versus via conventional face mask in patients with acute respiratory failure | Thirst intensity: VAS, measured after each 30-minute intervention | Change to oxygen administration via high-flow nasal cannula after oxygen administration via face mask | SpO2 96% or higher with humidified oxygen administered by face mask | 1 hour (0.5 hours each) | ↓ | NA |
Nagashima, 2008, Japan [34] | Quasi-experimental study | Mixed ICU | 22 (Method 1: 9/Method 2: 13) | Postoperative cardiovascular surgery, Patients with JCS single digits | Test the efficacy of salivary gland stimulation with a sponge brush as a method of relieving thirst in patients after cardiovascular surgery | Thirst intensity: 4-point Likert scale, measured after ICU discharge | Method 1: gargle with ice water, Method 2: stimulate salivary glands with care and moisturizing gel on lips | Method 1: when thirsty, Method 2: when regular and thirsty | Extubation: the start of drinking water | ↓ | NA |
Prevalence of Thirst
The prevalence of thirst was reported in 11 studies [5,6,19,22,36,38,44,50-53] and synthesized (Figure 2). Overall, the prevalence of thirst was 66% (95% CI: 56-76). The prevalence of thirst among ventilated patients was 77% (95% CI: 69-84). The prevalence of thirst within 24 hours of ICU admission was 68% (95% CI: 64-72), and during ICU stay was 63% (95% CI: 47-78).
Figure 2
Prevalence of thirst symptoms in ICU patients
Causes and Risk Factors for Thirst
Four studies [5,22,37,45] identified the risk factors for thirst using multivariable analysis. The reported risk factors were classified as patient/disease, treatment, and biochemical factors (Table 4).
Table 4
Risk factors for thirst reported in the included studies
Category | Risk factors for thirst (reference numbers) |
Patient/disease factors | Sepsis diagnosis [5] |
Greater disease severity [22] | |
Gastrointestinal diseases [37] | |
Xerostomia [45] | |
Treatment factors | Analgesic administration [5] |
Surgery [22] | |
Diuretics (such as high furosemide doses) [37,45] | |
Selective serotonin reuptake inhibitors [37] | |
Antihypertensive medications [37] | |
High opioid doses [37] | |
Negative fluid balance [37] | |
Prohibition of oral intake [22,37,45] | |
Mechanical ventilation [37] | |
Use of a humidified Venturi mask [45] (compared with a nasal cannula) | |
Biochemical factors | High glucose [22] |
Low ionized calcium [37] | |
Increasing serum sodium concentration [45] |
Measurement Tools for Thirst and Its Intensity and Distress Level
The values measured in non-intervention studies are listed in Table 5. Thirty-six studies measured thirst intensity [4,5,8,10,11,18,21,22,24-31,33,34,36-43,45,54-56,58-62,64]. Using the Numerical Rating Scale (NRS), thirst intensity ranged from 5.37 to 8.34 (Table 5). Twenty-five studies [5,8,10,11,18,21,22,24-30,33,37,38,40-43,45,56,58,59] used the NRS to measure thirst intensity. Four studies [55,60,61,64] used the Visual Analog Scale (VAS). Other scales used included the Likert scale [4,34,35,39,62], word scale [42], and Thirst Intensity scale [31,54]. Two studies [22,42] used two or more scales to measure the thirst intensity. Twenty-four studies measured thirst distress and stress [4,5,10,19,20,23,25-27,32,35-37,41,43,44,46,48-51,56,57,63]. Using the NRS, thirst distress ranged from 3 to 6 (Table 5). Five studies [10,37,41,43,56] used the NRS, and three studies [23,48,57] used the VAS. Fourteen studies [4,5,19,20,27,32,35,36,44,46,49,50,51,63] used 3 to 14-point Likert scales. Other tools included the Thirst Distress Scale (TDS), which was used in two studies [25,26], and the TDS for patients with heart failure (TDS-HF), which was used in one study [56]. The TDS-HF consists of eight items rated on a 5-point Likert scale. One study [56] examined the correlation between NRS and TDS-HF using both scales.
Table 5
Measurement tools and values of thirst intensity and thirst distress and stress reported in the included studies
Category | First author (year) | Measurement tool | Value |
Thirst intensity | Saltnes-Lillegård (2023) [5] | NRS, mean (95% CI) | 6.13 (5.70-6.56) |
Flim (2022) [56] | NRS, median (IQR) | 6 (3.0-8.0) | |
Negro (2022) [45] | NRS, mean ± SD | 5.37 ± 3.8 | |
Doi (2021) [8] | NRS, median (IQR) | 6 (5-8) | |
Krupa (2021) [54] | NRS, mean ± SD, median | 8.34 ± 1.36, 8 | |
Puntillo (2010) [4] | 3-point Likert scale, mean ± SE | 2.16 ± 0.87 | |
Li (2006) [38] | NRS, mean ± SD | 5.7 ± 3.7 | |
Thirst distress and stress | Gunnels (2024) [35] | NRS, mean ± SD | 3 ± 3.3 |
Saltnes-Lillegård (2023) [5] | NRS, mean (95% CI) | 4.98 (4.29-5.67) | |
Film (2022) [56] | NRS, median (IQR) | 6 (4.5-8.0) | |
Karaer,(2021) [49] | 4-point Likert scale, mean ± SD | 2.79 ± 1.32 | |
Baumstarck (2019) [57] | VAS (0-100), mean ± SD | 31 ± 35.04 | |
Takashima (2017) [19] | 6-point Likert scale, mean ± SD | 3.67 ± 1.4 | |
Dessotte (2016) [44] | 5-point Likert scale, mean ± SD | 2.6 ± 1 | |
Wang (2015) [23] | VAS (0-10), mean ± SE | 5.789 ± 0.022 | |
Puntillo (2010) [4] | 3-point Likert scale, mean ± SE | 1.9 ± 0.80 | |
Kalfon (2010) [48] | VAS (0-100), mean ± SD, median | 32 ± 34, 20 | |
Hweidi (2007) [20] | 4-point Likert scale, mean ± SD | 3.31 ± 0.79 |
Interventions for Thirst
The effects of each intervention are shown in Table 3. The interventions and number of studies conducted for each method are illustrated in Figure 3. Seven studies implemented bundle [11,31,41,42] or package [10,26,43] interventions. These interventions mainly combined oral moisturization with sprays, swabs, and lip moisturization. Sprays included cold water [10,24,25,27,29,31,41,42,58], mint [26], and vitamin C [11]. Some studies compared the contents and temperatures of sprays [11,24,25,27]. Lip moisturizers include menthol [26,41,43], mint [42], and glycerin [11]. The timing of interventions varied; interventions were regularly scheduled in seven studies [10,11,25,31,41,42,43] and included both regular and as-needed interventions for thirst in others [27,29,34]. The intervention frequency varied from studies that intervened every 30 minutes over a three-hour period to those that intervened three times a day. Other interventions included early oral intake [28,40], humidification [30,33,61,64], preconditioning before surgery [32,60], and relaxation interventions [59,62,63]. Most interventions were effective in reducing thirst intensity and distress. However, music interventions [62], combined music and aroma interventions [63], and virtual reality [59] did not improve thirst. The high-flow nasal cannula oxygen therapy group showed no significant difference with respect to thirst compared with the Venturi mask group [61]. However, an observational study comparing face masks reported a reduction in thirst intensity [64].
Figure 3
Graph of the type of intervention performed and the number of studies
The total exceeds the number of studies, as each study included multiple interventions [10,11,24-34,40-43,58-64].
NIV, noninvasive mechanical ventilation
Discussion
In this scoping review, we collected evidence on thirst in adult ICU patients. We included studies on the broad concepts of discomfort and stress among ICU patients, regardless of ICU stay duration or cause. Therefore, the evidence covers the overall state of thirst in ICU patients.
Prevalence and Impact of Thirst
The overall prevalence was 66%. It was high during mechanical ventilation, within 24 hours of ICU admission, and throughout the ICU stay. Studies conducted after 2010 have shown increased prevalence rates, possibly owing to increased recognition of thirst as a significant symptom and a shift to light sedation management. Thirst intensity was moderate to high in all studies and was reported to be the most distressing symptom among the common ICU symptoms (pain, thirst, anxiety, fatigue, and shortness of breath). Over 50% of respondents who experienced extreme ICU stress attributed this stress to thirst.
Measurement Tools and Methods for Thirst
Many studies have utilized the NRS, while others have used the VAS, Likert scale, and Thirst Intensity scale. These methods are effective for patients who can express their symptoms, but may overlook those who cannot. Most of the research has primarily focused on patients with Richmond Agitation and Sedation Scale scores ranging from -1 to +1 and those assessed as confusion-negative using the Confusion Assessment Method for the ICU. However, since many patients in the ICU are sedated or unconscious, there is a need to develop objective methods to assess the subjective thirst felt by patients. While oral dryness evaluation is one such method, it may miss patients’ perceived thirst because oral dryness does not always correlate with subjective thirst [8]. Additionally, conditions such as hypernatremia and elevated plasma osmolality have been associated with subjective experiences of thirst [2,65]. This indicates a need for further exploration of biochemical markers and the development of non-verbal measurement tools, which could significantly enhance the assessment of thirst in patients, particularly those who are unable to communicate their needs effectively. In addition, the assessment timing and frequency varied, with some studies evaluating registration, discharge, or daily care. Standardization of the timing, intervals, and frequency of assessments is required. Additionally, the criteria for when to intervene based on the NRS, VAS, or Likert scale scores have not yet been established. Recognizing the high prevalence of thirst among patients requires the development of standardized assessment protocols, measurement tools, and consistent timing.
Risk Factors for Thirst
The risk factors for thirst have been examined; however, direct intervention studies are few and unverified. These factors include patient/disease, treatment, and biochemical factors, which are related to ICU admission, diseases, and treatments [5,22,37,45]. Although patient/disease factors are unmodifiable, treatment and biochemical factors can be managed. Interventions such as avoiding hyperglycemia and correcting hypernatremia are relatively simple. Most interventions studied thus far are direct methods, such as ice water sprays. However, systemic management, addressing electrolyte imbalances and medication tapering, is also needed.
Intervention Methods and Effectiveness for Thirst
The effectiveness and sustained outcomes of interventions for managing thirst in ICU patients, including their optimal timing and frequency, remain largely ambiguous. This scoping review has identified that while various intervention methods exist, such as oral and lip moisturization through sprays and swabs with cold water, often implemented in bundles [11,31,41,42] or packages [10,26,43], the variability in methods, timing, and intervals complicates our understanding of their impact. ICU patients frequently cannot take oral fluids, restricting the amount of moisture applied. Some studies have indicated effectiveness with adjustments in water temperature [10,24,25,27,29,31,34,41,42,43,58] and the use of vitamin C water [11] or peppermint water [26]. Most studies included various interventions, but the effects and duration of a single intervention remain unclear. The duration of the intervention effects was investigated in only one study [8]. Thus, recognizing the absence of conclusive evidence for effective and lasting intervention methods highlights the critical need for further research. Additionally, there are numerous alternative interventions, such as preoperative measures [32,60], humidification adjustments of oxygen equipment [30,33,61,64], and relaxation techniques [59,62,63], each requiring further validation to confirm their efficacy.
Limitations
This study has several limitations. First, it focused on studies in which the primary concern was the patients’ perceived thirst, excluding studies that only examined dry mouth. Additionally, qualitative studies and gray literature were not included in our search, which may have affected the interpretation of prevalence rates and risk factors. Second, among the included studies, only four conducted multivariable analyses, which represents a significant limitation. This small number of studies with adjusted analyses limits our ability to draw definitive conclusions about independent risk factors and affects the generalizability of our findings. A larger study would increase the reliability of conclusions regarding risk factors. Furthermore, this scoping review did not assess the quality of the evidence. Therefore, the results and implications derived from the included studies should be interpreted with caution [16]. Despite these limitations, this scoping review provides valuable insights into the current state of thirst among ICU patients and identifies areas for future research development.
Conclusions
Thirst is highly prevalent among ICU patients and is a significant cause of distress. However, standardized methods for evaluating thirst intensity and distress remain unclear, particularly for patients who are unable to self-report, because no objective measurement tools have been established. Additionally, there are no defined thresholds for initiating thirst intervention. Although various interventions such as cold or mint water sprays or swabs have been explored, evidence on the most effective and sustained approaches, including their timing, frequency, and removal of risk factors, remains insufficient. Future studies should focus on validating assessment methods, including the development of objective measurement tools, and optimal intervention methods, including the removal of the risk factors for thirst identified in this study.
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Abstract
Thirst is one of the most frequently experienced symptoms among patients in intensive care units. Previous reviews of thirst in ICU patients and interventions to alleviate thirst had certain limitations. Therefore, we aimed to systematically explore and map the literature on the prevalence, risk factors, specific measurement methods, and intervention strategies for thirst in ICU patients and to identify areas where further research is needed. A scoping review was conducted to limit the search to studies published by August 2, 2024. A literature search was performed using PubMed, CINAHL, CENTRAL, and Igaku Chuo Zasshi databases. Two reviewers independently screened the literature according to the inclusion and exclusion criteria and extracted data from the selected studies. A total of 53 studies met the eligibility criteria. The combined prevalence of thirst, reported in 11 studies, was 66% (95% CI: 56-76). Four studies reported the risk factors for thirst, including sepsis, gastrointestinal disease, analgesics, diuretics, hyperglycemia, and elevated serum sodium levels, through multivariable analysis. The intensity of thirst and degree of distress were measured using the Numerical Rating Scale, the Visual Analog Scale, and the Likert scale in many studies. The interventions primarily consisted of oral and lip moisturization via sprays and swabs with cold water, many of which were bundled or packaged. The frequency of moisturization interventions for thirst varied from every 30 minutes over a three-hour period to three times a day, and it remained unclear which intervention frequency was the most effective. Other interventions included early oral intake, humidification, and use of music and virtual reality. None of the studies included interventions, such as medication adjustments or electrolyte correction, despite these being recognized as potential risk factors. Future studies should validate the measurement methods and develop objective measurement tools. The intervention types and frequencies that are most effective for treating thirst in ICU patients are unclear. Therefore, further research is required to evaluate the type, timing, and frequency of interventions while considering the identified risk factors.
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Details
1 Department of Nursing, Hospital of the University of Occupational and Environmental Health, Kitakyushu, JPN
2 Division of Faculty Development and Nursing, Kindai University, Osaka, JPN
3 Department of Nursing, Hokkaido University of Science, Sapporo, JPN
4 Department of Critical Care and Disaster Nursing, Japanese Red Cross Kyushu International College of Nursing, Munakata, JPN
5 Faculty of Nursing, Shimonoseki City University, Shimonoseki, JPN
6 Department of Nursing, Japanese Red Cross Fukuoka Hospital, Fukuoka, JPN
7 Department of Nursing, Fukuoka Tokushukai Hospital, Kasuga, JPN
8 Department of Nursing, Kurume University Hospital, Kurume, JPN
9 Department of Nursing, National Hospital Organization Kumamoto Medical Center, Kumamoto, JPN