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Author: Admin | 2025-04-28
OverviewThis section presents drugs that affect 3 dimensions of the cardiovascular system:•Inotropic state of the heart•Chronotropic state of the heart Clinically these drugs are used in•Acute ischemic heart disease•Acute and chronic heart failure•Shock (especially cardiogenic)EpinephrineEpinephrine hydrochloride produces beneficial effects in patients during cardiac arrest, primarily because of its α-adrenergic receptor–stimulating properties.1 The adrenergic effects of epinephrine increase myocardial and cerebral blood flow during CPR.2 The value and safety of the β-adrenergic effects of epinephrine are controversial because they may increase myocardial work and reduce subendocardial perfusion.3Although epinephrine has been used universally in resuscitation, there is a paucity of evidence to show that it improves outcome in humans. For a number of years researchers and clinicians have also questioned the optimal dose of epinephrine. The “standard” dose of epinephrine (1.0 mg) is not based on body weight. Historically a standard dose of 1 mg epinephrine was used in surgical operating rooms for intracardiac injections.4 5 6 Surgeons observed that 1 to 3 mg of intracardiac epinephrine was effective in restarting the arrested heart.6 7 When these and other experts first produced resuscitation guidelines in the 1970s, they assumed that 1 mg of IV epinephrine would work in a similar manner as 1 mg of intracardiac epinephrine. Adult patients vary greatly in weight, yet clinicians continue to inject the same 1-mg dose of epinephrine for all body weights.The dose-response curve of epinephrine was investigated in a series of animal experiments during the 1980s. This work showed that epinephrine produced its optimal response in the range of 0.045 to 0.20 mg/kg.8 9 10 11 From these studies it seemed that higher doses of epinephrine were necessary to improve hemodynamics and achieve successful resuscitation, particularly as the interval from cardiac arrest increased. This work led many clinicians to use higher doses of epinephrine in humans, and optimistic case series and retrospective studies were published in the late 1980s and early 1990s.12 13 14Results from 4 clinical trials then compared high-dose epinephrine with standard-dose epinephrine.8 15 16 17 Overall the rate of return of spontaneous circulation (ROSC) was increased with higher doses of epinephrine (0.07 to 0.20 mg/kg); however, no statistically significant improvement in the rate of survival to hospital discharge occurred. On the positive side, these trials failed to detect any significant harm from administration of higher doses of epinephrine. On the basis of this information, in 1992 the guidelines recommended that the first epinephrine dose continue to be 1 mg IV. The 1992 guidelines also recommended that the interval between subsequent doses of epinephrine be every 3 to 5 minutes rather than every 5 minutes. If the 1 mg epinephrine every 3 to 5 minutes seemed to be ineffective, the 1992 guidelines accepted the use of higher doses of epinephrine in either escalating doses (1, 3, 5 mg), intermediate doses (5 mg per dose rather than 1 mg), or high doses based on body weight (0.1 mg/kg).Both beneficial and toxic physiological effects of epinephrine administration during CPR have been shown in animal and
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