Effect of standard-dose versus high-dose epinephrine on myocardial high-energy phosphates during ventricular fibrillation and closed-chest CPR.

STUDY OBJECTIVE: To evaluate the effects of standard-dose versus high-dose epinephrine on myocardial high-energy phosphate metabolism during resuscitation from cardiac arrest. DESIGN: Prospective, nonrandomized, controlled study using a swine model of cardiac arrest and resuscitation. INTERVENTIONS: After anesthesia, intravascular pressure instrumentation, and ten minutes of ventricular fibrillation arrest, closed-chest CPR was begun. After three minutes of CPR, animals were allocated to receive either 0.02 mg/kg i.v. standard-dose epinephrine (eight) or 0.2 mg/kg i.v. high-dose epinephrine (nine). The animals underwent thoracotomy and rapid-freezing transmural myocardial core biopsy for high-energy phosphate analysis 3.5 minutes after epinephrine administration. High-energy phosphate values were blindly determined using high-pressure liquid chromatography. RESULTS: Intravascular pressure (mm Hg) and high-energy phosphate (nmol/mg protein) results for standard-dose epinephrine versus high-dose epinephrine are, respectively, coronary perfusion pressure, 15.3 +/- 7.8 versus 23.7 +/- 5.5 (P = .0009); phosphocreatine, 0.4 +/- 0.8 versus 6.2 +/- 4.4 (P = .0003); adenosine triphosphate, 9.8 +/- 4.8 versus 12.7 +/- 5.7 (P = .30); adenosine diphosphate, 5.4 +/- 2.1 versus 6.1 +/- 1.3 (P = .41); and adenylate charge, 0.68 +/- 0.12 versus 0.72 +/- 0.12 (P = .87). CONCLUSION: High-dose epinephrine does not deplete myocardial high-energy phosphate when given in this model of prolonged ventricular fibrillation. High-dose epinephrine increases coronary perfusion pressure compared with standard-dose epinephrine. High-dose epinephrine administration repletes phosphocreatine during closed-chest CPR, thereby increasing myocardial energy stores.

Effects of splenectomy on hemodynamic performance in fixed volume canine hemorrhagic shock.

Studies of canine hemorrhagic shock commonly use a splenectomized fixed-pressure model. Splenectomy is recommended in this model to avoid variable degrees of autotransfusion that reduce the reliability of mortality estimates and blood volume measurements. The effects of splenectomy on a non-lethal fixed-volume canine hemorrhage have not been established. The purpose of this study was to investigate cardiovascular and biochemical effects of splenectomy in fixed-volume canine hemorrhagic shock. Nineteen beagles of uniform size and weight were bled 50% of their estimated blood volumes over 1 hr and then left without therapeutic intervention for a 90 min stabilization period. Arterial blood pressure (MAP), central venous pressure, pulmonary artery pressure, heart rate (HR), cardiac output, glucose, lactate, arterial and mixed venous blood gases, and hematocrit (HCT) were measured at regular intervals. Cardiac index (CI), stroke volume, and oxygen saturation (O2SAT), delivery (O2DEL) and consumption (O2CON) were calculated at these intervals. Results from ten control animals were compared to those from nine animals that had been splenectomized 2 wk prior to hemorrhage. During the hemorrhage period, there were no significant differences observed between groups for HR, MAP, or O2DEL. CI remained higher (P less than 0.025) and HCT lower (28.9 +/- 4.7 vs 39.8 +/- 4.5) (P less than 0.001) in splenectomized animals. Immediately following hemorrhage there were no significant differences in the mean values for HR, CI, MAP, or serum lactate. O2DEL however, was significantly higher in control animals (P less than 0.05). During stabilization MAP, CI, and O2DEL rose while HCT fell in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)