Whole blood vs saline for MAP restoration in anesthetized piglets after non-traumatic hemorrhagic shock: an experimental study

Abstract

In the management of hemorrhagic shock (HS), the restoration of adequate mean arterial pressure (MAP) while minimizing complications is critical. Whole blood (WB) has demonstrated physiological advantages over crystalloids such as normal saline (NS), yet direct comparisons in non-traumatic HS remain scarce. This study sought to evaluate the volume and hemodynamic efficacy of WB compared to NS in achieving a MAP of 60 mmHg in a porcine model of non-traumatic HS. The WB requirement and the NS volume necessary to restore MAP were 12 [10–14] and 23 [20–24] mL·kg^-1, respectively (p < 0.01). One hour after resuscitation, mean arterial pressure (MAP) in the WB group was 69 [66–73] mmHg, and MAP in the NS group was 57 [55–64] mmHg (p < 0.05). Immediately after resuscitation, a median change of 1.4 [0.8–2.0] mmol·L^-1 and -0.4 [-1.0–0.3] mmol·L^-1 was observed in the WB and NS groups for base excess, respectively (p < 0.05). One hour after resuscitation, lactate levels decreased in median by -3.5 [-4.5 to -2.3] and -1.3 [-2.0 to -0.9] mmol·L^-1 in the WB and NS groups, respectively (p < 0.05). Cardiac output and Syndecan-1 levels did not differ significantly between the groups. In this model of non-traumatic HS, WB showed greater efficacy in restoring MAP with a reduced infusion volume (1:2 WB:NS), exhibiting enhanced markers of metabolic recovery. Despite the comparable endothelial response, as indicated by Syndecan-1 levels, WB yielded more protracted hemodynamic benefits. These findings support the potential use of WB in early HS resuscitation and highlight the need for further investigation in non-trauma HS.

Introduction

In emergency medicine, the primary goal of hemorrhagic shock (HS) resuscitation is to restore adequate mean arterial pressure (MAP) while minimizing secondary complications such as coagulopathy, acidosis, and endothelial dysfunction¹. Blood transfusion is the gold standard for the treatment of HS due to its ability to rapidly restore oxygen delivery and intravascular volume. Trauma-induced HS is a complex pathology involving coagulopathy and inflammation². Most recommendations of HS resuscitation focus on traumatic HS^{3, 4–5}. The treatment of non-traumatic HS is based on studies of traumatic HS, although the pathophysiology is different^{6, 7–8}.

Whole blood (WB) offers physiological advantages by providing hemostatic and volume-expanding effects in a single transfusion⁹. WB is used by several teams in the initial management of trauma and non-trauma HS¹⁰. However, blood availability may be limited, necessitating the initial use of crystalloids—such as normal saline (NS) or Ringer’s lactate—as an immediate alternative^{3, 4–5}. While crystalloids can temporarily restore circulating volume and MAP, their hemodynamic efficacy is limited by rapid redistribution, dilutional coagulopathy, and endothelial glycocalyx degradation, which can exacerbate vascular leakage and tissue hypoxia¹¹. Empirical guidelines recommend limiting crystalloid administration to 1,000 mL to prevent fluid overload and mitigate adverse effects^{3, 4–5}.

Previous studies suggest that RBC transfusion is more effective than crystalloids in restoring MAP after acute blood loss, but there are limited data directly comparing RBC to NS in terms of resuscitation volume requirements and hemodynamic response^12,13. The aim of this study was to evaluate the hemodynamic efficacy of WB versus NS in achieving a MAP of 60 mmHg in a controlled non-traumatic HS model using anesthetized and mechanically ventilated piglets. We hypothesized that WB would restore MAP with a lower volume requirement than NS due to its superior oxygen carrying capacity and oncotic properties. In addition, we assessed levels of syndecan-1, a glycocalyx degradation marker, to investigate whether fluid type plays a role in endothelial integrity and vascular function in non-traumatic hemorrhage¹⁴.

By providing a comparative analysis of WB and NS in terms of fluid volume requirements and hemodynamic effects, our findings may help to refine resuscitation strategies and optimize fluid management in the initial treatment of HS.

Methods

This study was designed as a prospective, randomized, unblinded study in an anesthetized and mechanically ventilated piglet model. The protocol was approved by the Animal Care and Use Committee of Languedoc–Roussillon (CEEA- LR n°36, APAFIS#29,341–2,021,012,709,128,801), and all experiments were performed in an authorized animal research laboratory. The piglets were Large White of 2–3 months of age, reared in an appropriate farm (Gaec Maruejols Le Bès, Sauveterre de rouergue, France) before transport at least 3 days before the experiments. Of the 16 piglets, 9 (56%) were female. This study was conducted in accordance with the European Directive and Guidelines 2010/63/EC, which regulate the use of animals in science. All facilities and transport complied with the current legal requirements. This study complied with the Animal Research: Reporting of In Vivo Experiments 2.0 (ARRIVE 2.0) guidelines¹⁵.

Study objectives

The primary objective of the study was to compare the volumes of WB and NS required to restore a MAP of 60 mmHg. This value was chosen because piglets have a lower MAP in than humans and to minimize the need for WB transfusion beyond the initial blood withdrawal¹⁹. Even though its harmful effects on resuscitation from hemorrhagic shock are well known, NS was chosen because it remains widely used in emergency settings. As a secondary objective, we aimed to show superiority in MAP at immediately after resuscitation (T3) and one hour after resuscitation (T4) for WB compared to NS. We also aimed to compare the within-subject changes in physiological and laboratory parameters (base excess (BE), hemoglobin, lactate, cardiac output (CO), pH, partial pressure of carbon dioxide (pCO2) and partial pressure of dioxygen (pO2)) between the two groups at predefined time intervals (between the shock phase and immediately after resuscitation [T2–T3], between the shock phase and the end of the stabilization period [T2–T4], and between the beginning and the end of the stabilization phase [T3–T4]). Finally, Syndecan-1 levels were measured at experimentation beginning (T0), after shock phase (T2) and after stabilization phase (T4) to assess the presence of endotheliopathy.

Experimental protocol

This pressure-controlled experimental protocol, shown in Fig. 1, was slightly modified from our previous studies^16,17. Briefly, three-month-old piglets were premedicated with an intramuscular injection of ketamine (10 mg.kg⁻¹), atropine (0.05 mg.kg⁻¹), and midazolam (1 mg.kg⁻¹). Anesthesia was induced with a bolus dose of propofol (4 mg·kg⁻¹), sufentanil (10 µg), and cisatracurium (0.25 mg.kg⁻¹) administered via a peripheral ear vein and maintained with propofol (8 mg.kg⁻¹.h⁻¹). The piglets were ventilated after orotracheal intubation with an inspired oxygen fraction adjusted based on the first arterial blood sample, a tidal volume of 8 mL.kg⁻¹, and a positive end-expiratory pressure of 5 cmH₂O. Once the piglets were anesthetized, a 7-Fr triple lumen catheter was inserted with ultrasound guidance through the internal jugular vein and the right cardiac atrium. The central venous line was used to monitor the central venous pressure and inject cold water boluses for transpulmonary thermodilution. A 5-Fr arterial catheter with an integrated thermistor tip was inserted through the right femoral artery (PiCCO Plus; Pulsion Medical Systems, Munich, Germany) to monitor continuous arterial pressure, calibrate cardiac output (CO) by thermodilution, calculate continuous pulse pressure variation (PPV), and sample arterial blood. The right femoral vein was also cannulated with an 8.5-Fr catheter (Arrow; Arrow International, Inc, Cleveland, USA) for blood withdrawal and for resuscitation fluid administration. All pressure-measuring catheters were connected to transducers (PiCCO Plus; Pulsion Medical Systems, Munich, Germany) to continuously record systemic arterial pressure and heart rate (HR).

[See PDF for image]

Fig. 1

Experimental protocol schema. NS: normal saline, WB: whole blood, MAP: mean arterial pressure.

T0 marked the beginning of the experiment. Bleeding was performed by withdrawing venous blood through the right femoral venous catheter in increments of 2 mL.Kg⁻¹.min⁻¹ until an MAP of 40 mm Hg was reached, which defined T1. The MAP was then maintained between 35 and 45 mmHg with blood withdrawal or fluid filling for 30 min (T2). Piglets were randomized into the NS or WB group prior to the experiment using a computer-generated randomization sequence to ensure balanced group allocation. They received repeated boluses (10 mL.Kg⁻¹.min⁻¹) of the randomized fluid until a MAP of 60 mmHg was reached (T3). If the MAP dropped by more than 5 mmHg below the target of 60 mmHg, an additional 1 mL.kg⁻¹ bolus of the allocated fluid was administered. This was repeated as many times as necessary to restore the 60 mmHg MAP. No additional withdrawal was performed if the MAP increased. This stabilization phase lasted 1 h (T4). All animals were euthanized using a bolus of 60 mg.Kg⁻¹ of pentobarbital via the ear vein at the end of the protocol.

Main measurements

Several measurements were performed at T0: hemodynamic parameters (systolic and diastolic arterial pressure, MAP, HR, CO, PPV), arterial blood biological parameters [lactate, hemoglobin, BE, pH, pCO2 pO2], and Syndecan-1 where measured. The measurement of the same hemodynamic parameters was performed at each 5 mL·Kg⁻¹ of blood withdrawal (T0a, T0b, T0c, … to T1). In addition, arterial biological parameters were measured at T1. All parameters were measured at T2, including Syndecan-1. Hemodynamic parameters were recorded at every 10 mL·kg⁻¹ of fluid filling (T2a, T2b, …) until the value of 60 mmHg MAP was reached (T3). Arterial blood biological and hemodynamic data were collected at T3. Finally, hemodynamics parameters were measured at 30 min (T3a), and all parameters were measured at T4, including Syndecan-1. Syndecan-1 levels were assessed at T0 (baseline), T2 (expected maximum endothelial damage), and T4 (comparison between NS and WB one-hour after resuscitation).

WB transfusion

The blood used for transfusion was freshly collected autologous blood, anticoagulated with low-molecular-weight heparin. In brief, WB was collected in a urine bag and anticoagulated with 2,500 UI of low-molecular-weight heparin, equivalent to the preventive anticoagulation for a 30 kg human. Blood was drawn as usual with a flush of 10 mL of NS to avoid clotting in the tubing. WB was infused at the same speed as NS during resuscitation phase (10 mL.Kg⁻¹.min⁻¹).

Biological measurement

At each major time point of the experiment, 2 mL of blood was withdrawn through the arterial line. Common blood biological parameters were analyzed in real time using a portable blood analyzer (Epoc Vet, Siemens Healthineers, Erlangen, Germany). For Syndecan-1 measurement, 5 mL blood aliquots were collected at T0, T2, and T4, in ethylenediaminetetraacetic acid anticoagulated tubes. The blood samples were centrifuged and frozen at −80 °C. Measurements were performed 3 months after the experiment, using a porcine Syndecan-1/CD138 enzyme-linked immunosorbent assay kit (MBS749086-96, CliniSciences S.A.S, Nanterre, France), with a sensitivity of 0.1 ng.mL⁻¹.

Statistical analysis

Missing values for standard biological parameters were imputed using a logistic regression method that accounted for the CO and MAP for the entire population if the number of missing values did not exceed 10% of the total sample. Conversely, no imputation was performed if the missing values exceeded 10%. No imputation was performed for Syndecan-1 and missing values were considered as they were.

Qualitative variables were expressed as absolute numbers and percentages. Quantitative variables were expressed as medians with first and third quartiles and compared between the two groups using the Mann–Whitney U test. For the primary objective and the first secondary objective, the tests were performed unilaterally, indicating superiority for WB over to NS. To assess whether the changes in BE, hemoglobin, lactate, CO, pH, pCO2 and pO2 differed between measurement intervals (T2-T3, T2-T4 and T3-T4) according to the study group, we first computed the individual differences for each subject and each interval. Because the analysis focused on between-group comparisons of individual within-subject changes over time, unpaired tests were used on calculated temporal differences, rather than paired tests between time points. This analysis was conducted bilaterally.

No adjustment for multiple testing was made for secondary objectives. The sample size was not calculated before the start of the study. Based on feasibility considerations and similar previous experiments using this model, it was decided that a sample size of eight piglets per group would be sufficient. Post hoc power analysis was performed by considering the calculated effect size, the number of subjects per group, and the 5% alpha level. All data were analyzed using R software, version 4.3.2 (R, The R Foundation for Statistical Computing, Vienna, Austria).

Results

A total of 16 piglets were included, with a median weight of 33.6 [30.4–37] Kg, of which 9 (56%) were female. One piglet from the NS group was euthanized after T3 due to a technical problem.

The median volume of depletion to reach T1 was 40 [39–45] mL.Kg⁻¹ (46 [44–47] mL.Kg-1 for NS group and 40 [35–43] mL.Kg-¹ for WB group, p = 0.14). The characteristics of biological and hemodynamic parameters per group for the whole study are presented in Table 1.

Table 1. Characteristics of hemodynamics and biological parameters of the piglets at baseline (T0), at shock beginning (T1),30 min after shock beginning (T2), immediately after resuscitation with a mean arterial pressure objective of 60 mmHg (T3) and one-hour after resuscitation (T4).

	T0		T1		T2		T3		T4
	WB n = 8	NS n = 8	WB n = 8	NS n = 8	WB n = 8	NS n = 8	WB n = 8	NS n = 8	WB n = 7	NS n = 8
Hemodynamics parameters
Mean arterial pressure, median [Q1-Q3], mmHg	75 [65–84]	77 [70–85]	39 [35–40]	39 [36–40]	37 [34–44]	39 [37–40]	70 [64–82]	63 [60–67]	69 [66–73]	57 [55–64]
Heart rate, median [Q1-Q3], bpm	72 [66–79]	100 [75–110]	185 [169–198]	190 [174–194]	192 [178–205]	180 [171–193]	173 [165–183]	181 [164–189]	187 [178–201]	195 [182–203]
Cardiac output, median [Q1-Q3], L.min−1	2.5 [2.4–3.2]	3.3 [2.5–4.6]	1.5 [1.3–1.6]	1.6 [1.2–1.8]	1.7 [1.5–1.9]	1.9 [1.6–2.2]	2.8 [2.6–3.1]	2.9 [2.5–3.4]	2.7 [2.6–2.8]	2.7 [2.0–3.2]
Missing	-		-		1 (6.3)		-		-
Biological parameters
Lactate, median [Q1-Q3], mmol.L−1	2.7 [2.4–2.9]	2.8 [2.5–3.3]	5.7 [5.0–6.7]	5.3 [4.5–7.4]	9.3 [7.5–11.3]	8.5 [6.3–9.5]	9.6 [7.6–12.0]	9,1 [5.8–9.7]	6.3 [5.1–8.1]	6.4 [3.7–8.8]
Base excess, median [Q1-Q3], mmol.L−1	2.3 [1.1–3.8]	3.6 [1.6–5]	−0.9 [−1.5 – −0.2]	1.3 [−0.2 – 2.6]	−3.55 [−4.8 – −3.1]	−2.6 [−5.8 – −0.7]	−3.2 [−4.1 – −0.6]	−4.0 [−6.2 – −2.0]	−0.3 [−1.3 – 0.6]	−0.4 [−2.9 – 0.00]
Hemoglobin, median [Q1-Q3], g.dL−1	9.5 [9.3–9.8]	9.2 [8.6–9.9]	8.3 [8.1–8.8]	7.6 [7.4–7.9]	8.7 [8.3–9.2]	7.10 [7.2–7.3]	9.8 [9.5–10.0]	6.5 [6.3–7.0]	10.2 [9.7–10.6]	7.10 [6.6–7.3]
pH, median [Q1-Q3]	7.39 [7.38–7.40]	7.39 [7.35–7.41]	7.36 [7.35–7.38]	7.33 [7.24–7.37]	7.28 [7.23–7.32]	7.23 [7.18–7.29]	7.25 [7.17–7.28]	7.23 [7.15–7.26]	7.34 [7.32–7.38]	7.31 [7.27–7.38]
pCO2 (mmHg)	47 [45–49]	46 [45–50]	43 [42–48]	43 [39–50]	48 [44–53]	47 [35–58]	63 [50–69]	59 [51–72]	44 [41–52]	48 [45–65]
pO2 (mmHg)	84 [81–87]	80 [77–82]	80 [77–85]	71 [63–84]	71 [67–82]	60 [55 −80]	61 [55–76]	59 [53–68]	85 [78–90]	70 [60–86]
Missing	-		2 (12.5)		1 (6.3)

Primary objective results

Median volumes of fluid filling at T3 were 23 [20–24] mL.Kg⁻¹ for the NS group and 12 [10–14] mL.Kg⁻¹ for the WB group (p < 0.01, median difference = 10; 95% CI = [5 – + ∞]). This corresponds to 0.5 [0.44–0.59] and 0.33 [0.24–0.36] times the volume of blood expelled for NS and WB, respectively. Figure 2 shows the evolution of filling volume over time for both groups per piglet. The effect size was estimated to be d = 2.18, with 99% power for the primary outcome measure.

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Fig. 2

Volume of fluid infused to piglets at each resuscitation time. WB: whole blood, NS: normal saline.

Secondary objective results

There was no difference in MAP at T3 (NS: 63 [60–67] mmHg, WB: 70 [64–82] mmHg, p = 0.07). At T4, the MAP was higher in WB group (NS: 57 [55; 64] mmHg, WB: 69 [66–73], p < 0.05).

The evolution of BE, hemoglobin, lactate, CO, pH, pCO2 and pO2 over time and the corresponding between-group differences are summarized in Fig. 3, with individual changes shown for each interval and group. BE increased in the WB group compared to NS between T2 and T3 (1.4 [0.8–2.0] mmol.L⁻¹ vs. −0.4 [−0.98 – 0.33] mmol.L⁻¹, p < 0.05). Lactate decreased between T3 and T4 with WB compared to NS (−3.5 [−4.5 – −2.3] mmol.L⁻¹ vs. −1.3 [−2.0 – −0.9] mmol.L⁻¹, p < 0.05). No difference was found for other parameters.

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Fig. 3

Median difference of base excess, cardiac output, hemoglobin, lactate, arterial CO2 partial pressure, pH and arterial O2 partial pressure between T2 and T3, T2 and T4 and T2 and T3. NS: Normal saline, WB: whole blood, pCO2: arterial CO2 partial pressure, pO2: arterial O2 partial pressure.

Syndecan-1 median levels were 35.9 [30.4–48.6] ng.mL⁻¹, 30.5 [28.4–34.2] ng.mL⁻¹, and 26.4 [23.6–32.4] pg.mL⁻¹. There was no difference between the groups at T0, T2, and T4 (Fig. 4).

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Fig. 4

Results of Syndecan-1 levels at baseline (T0), late shock phase (T2), and late resuscitation phase (T4). Syndecan-1 was measured in 16 (100%), 14 (88%), and 14 (88%) piglets at T0, T2, and T4. NS: Normal saline, WB: whole blood.

Discussion

The results of this experimental study showed that the volume of WB required to resuscitate non-traumatic HS was lower than that of NS, with a median difference of 10 (95% CI = [5 – + ∞]) mL.Kg⁻¹. WB was non-inferior to NS for hemodynamic and biological parameters at T3 and T4, except for hemoglobin. Syndecan-1 levels at T4 were not different between the NS and WB groups.

The volume infused to achieve a MAP of 60 mmHg is much lower with WB than with NS. Notably, 1 h after the HS resuscitation, MAP was higher than that with NS, suggesting a better initial maintenance of arterial pressure. Therefore, WB resuscitation may improve patient resuscitation by reducing the risk of coagulopathy, as previously demonstrated¹⁸, but may also improve hemodynamics on a sustained basis. The MAP target of 65 mmHg in humans is a compromise between organ perfusion and a reduced risk of rebleeding¹. However, this strategy is questioned, especially in the prehospital setting and for non-traumatic HS, and a higher MAP target might be beneficial¹⁹. Chen et al. found that in a rat polytrauma model, the administration of half volume of withdrawn WB allowed more accurate restoration of hemodynamics than the same quantity of Ringer’s lactate¹². Similarly, in a piglet model, Roger et al. found that a retransfusion of half of the withdrawn blood allowed restoration of the baseline MAP²⁰. However, they did not they observed restoration of CO with WB compared to other fluids, such as hydroxyethyl starch. In the present study, the lack of CO improvement is interesting because a low WB volume seems to have the same effect as the NS volume. This could be due to the rheological properties of WB²¹, as CO is correlated with blood viscosity²². Otherwise, the expansion volume of WB is likely to be greater than that of NS²⁰. Therefore, WB resuscitation may limit post-resuscitation fluid overload⁵. Although our model is experimental and non-traumatic, it provides quantitative support for emerging prehospital strategies that prioritize the use of WB and limit crystalloids, consistent with the principles of damage control resuscitation and low-volume resuscitation derived from clinical experience.

BE increased in the WB group compared to NS between T2 and T3, but no difference was observed between T3 and T4. In contrast, lactate was no different between T2 and T3 and decreased between T3 and T4 with WB compared to NS. Improvement in BE and lactate clearance are well-established biomarkers of effective resuscitation³ and are associated with survival in traumatic and non-traumatic HS^23,24. Acidosis in HS is associated with arterial stress and tissular injury and is exacerbated by intensive fluid resuscitation in the initial phase of HS resuscitation¹¹. Previous studies in a polytrauma monkey model also found an improvement in acid–base statues with WB resuscitation¹⁸. WB may first reduce acidosis and then improve cellular oxygenation. Regarding the hemoglobin level, our results were not surprising, because we immediately transfused the piglets with their own blood. However, despite this difference in hemoglobin levels, there was no difference in pO2 and pCO2. These results need to be specifically investigated in other studies, particularly by measuring tissue concentrations of O2 and CO2, to determine if these results remain valid at the tissue level. Investigation of coagulation was of interest, although probably no change would have been shown². Finally, a MAP target is not sufficient to assess a good resuscitation in HS, especially when NS is used.

Interestingly, Syndecan-1 levels decreased during the experiment, in agreement with other studies on early HS resuscitation with NS²⁵. Although this may seem surprising, it may be due to the non-traumatic nature of the HS model, the small volume used for resuscitation, and the precocity of the measurements. Previous studies showing increase in Syndecan-1 focused on patients with major trauma^26,27. A study by Zeinnedin found no change in Syndecan-1 level was found in patients with minimal injury²⁷. The lack of difference in Syndecan-1 measurement between groups at T4 may be due to the lack of glycocalyx shedding²⁸ and the poor alteration of microcirculation in non-traumatic HS²⁹. These findings suggest that Syndecan-1 may not be a sensitive marker of early endotheliopathy in non-traumatic hemorrhagic shock, and encourage exploration of alternative biomarkers such as hyaluronic acid or heparan sulfate³⁰. Microcirculation-guided therapeutics may be useless in non-traumatic or minimally injurious HS, because hemodynamic coherence is initially poorly affected³¹. Specific studies should focus on the specificity of both mechanisms.

Limitations

Our study has certain limitations that need to be emphasized. Although the results of this study are not surprising³², to our knowledge, this is the first study to directly compare the hemodynamic differences between NS and WB in non-traumatic HS resuscitation as a primary objective. The team was highly experienced with this model, which was specifically designed for hemodynamic measurements^{16,17,20,33, 34–35}, which gives our results strong internal validity.

However, this experimental study requires caution when extrapolating to human conditions. A notable limitation is the lack of blinding. Although objective criteria were monitored in real time, this limitation may introduce a potential performance bias. In addition, the rate of fluid administration used in our experimental model, although standardized for comparability, may differ significantly from clinical practice, which may limit the direct translation of these findings to the human setting. Additional studies using more clinically relevant administration rates are needed. The ratio of WB to NS observed in this study (approximately 1:2) requires validation in humans due to inherent differences in cardiovascular physiology between species.

Several randomized trials have evaluated the use of early prehospital transfusion in trauma patients, yielding conflicting results. The PAMPer trial demonstrated a survival benefit with plasma transfusion during prolonged air transport³⁶. In contrast, COMBAT, which was conducted in an urban setting with shorter transport times, found no benefit³⁷. More recent trials using red cells with lyophilized plasma or plasma alone, such as RePHILL and PREHO-PLYO, also failed to demonstrate improved survival or hemostatic correction^38,39. In contrast, our porcine model allowed for controlled hemorrhaging and precise hemodynamic monitoring, showing rapid MAP restoration with WB. These findings suggest that the early administration of a physiologically complete product may provide hemodynamic benefits, especially in situations requiring rapid circulatory support.

Coagulation parameters were intentionally not measured, given the non-traumatic model chosen, although we recognize their importance in trauma-induced HS. The quality of the fresh anticoagulated autologous WB was not assessed, and the components may differ from WB used in humans. Low-molecular-weight heparin was used for anticoagulation of autologous blood. While practical in the animal model, this differs from the standard citrate anticoagulation in human transfusion protocols and may affect endothelial and coagulation responses⁹. The limited sample size and broad confidence intervals further restrict the generalizability of the findings, despite the 99% power for the primary outcome. This deficiency in statistical power might also be a contributing factor to the absence of significant differences observed in some secondary outcomes. Given the absence of any adjustment for multiple testing, the interpretation of secondary results must be conducted with caution. The duration of the shock phase may have been insufficient to induce severe endotheliopathy and the follow-up may have been too short to detect an inflammatory response and endothelial dysfunction. Further studies should include a longer shock phase and longer follow-up to determine if and when non-traumatic hemorrhage causes endothelial lesions. Syndecan-1 may lack sensitivity as a biomarker for early stage endotheliopathy; other biomarkers may give different results. Finally, our study underscores a critical issue in HS research: there appear to be at least two distinct phenotypes of HS—one associated with major trauma and the other with low or no trauma. This observation underscores the necessity for distinct investigative and therapeutic approaches, tailored to address the differing physiopathologies.

Conclusion

In this experimental study on controlled HS in piglets, the infused volume of WB to restore a mean arterial pressure (MAP) of 60 mmHg was lower than that of NS. Furthermore, the WB group exhibited prolonged arterial pressure improvements following resuscitation. Significant changes were observed in the WB group compared to the NS group, particularly in the early phase post-resuscitation and one hour after resuscitation, as indicated by BE and lactate levels, respectively. Further studies could compare the hemodynamic effects of WB therapy and component therapy.

Acknowledgements

The authors thank Jack Fountain and Yassine Kraouch for the preparation of the animals.

Author contributions

FC, DT, LGM, TS, MB, TM and XB: investigation and data curation; FC: formal analysis; FC: figures preparations; FC, FA, LGM and XB: conceptualization and methodology; FC, AG, LGM and TS: Writing—Original Draft; DT, FA, MB, JYL, TM and XB : Writing—Review & Editing; JYL and XB: supervision and project administration, MB and JYL: resources, JYL: funding acquisition.

Funding

This study was funded by IMAGINE (Montpellier University and Nîmes University Hospital).

Data availability

The datasets generated and analyzed during the current study are not publicly available due to privacy restrictions but are available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.

Ethics approval and consent to participate

CEEA- LR n°36 approved the protocol APAFIS#29341–2021012709128801. Being an experimental study, no consent to participate was needed.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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