Content area
Full Text
ABSTRACT
Pharmacology is integrated in all areas of nursing practice. From the most basic entry level to the most advanced clinical practice, nursing curriculums are not complete without pharmacology. The word "pharmacology " often makes nurses and other health care professionals feel uneasy. Pharmacology implies complicated words and formulas that seem foreign, recalled only from one's most distant recollections of college years. For many health care providers, courses in pharmacology are taken before they care for patients, leaving them with little practical experience from which to relate. Education involves not simply learning and doing, but also applying knowledge. A basic understanding of pharmacology is needed to break down the barriers of pharmacologic communication and put the clinician at ease with terminology so often used by the medical community. AORN J 71 (Jan 2000) 173-185.
An inotrope is an agent that affects myocardial contractility. A positive inotrope causes increased contractility (eg, dobutamine), and a negative inotrope causes decreased contracttility (eg. the beta-blocker metoprolol). A chronotrope is an agent that affects heart rate. Positive chronotropes cause an increase in heart rate (eg, epinephrine, isuprel). Negative chronotropes cause a decrease in the heart rate. Examples of negative chronotropes are beta-blockers and rate control calcium channel blockers (eg, diltiazem). A dromotrope affects atrial-ventricular (AV) node conduction. A positive dromotrope increases AV nodal conduction (eg, atropine sulfate), and a negative dromotrope slows AV nodal conduction (eg, lanoxin). A lusitrope is an agent that affects diastolic relaxation.
Many positive inotropes affect preload and afterload; therefore, these terms must be defined to facilitate understanding (Table 1). Preload is defined as the blood volume remaining in the ventricles at the end of diastole or ventricular end diastolic volume (VEDV). Preload influences the amount of end diastolic stretch on the myocardial muscle fibers. Venous blood return to the heart is influenced not only by actual blood volume in the venous system but also by venous tone or compliance, which is the relaxation and contraction in the smooth muscle walls of the veins. Preload enhancers are vasopressors and volume expanders (eg, normal saline). Preload reducers are vasodilators and diuretics.'
Afterload is the pressure that the ventricles must pump against to overcome the resistance to systolic ejection. Afterload is determined primarily by the arterial...