118 LITERATURE REVIEW

other 25 patients were randomly assigned to receive adenosine (successive 40 ug/kg increments to maximum dose of 20 mg) or verapamil (70 kg/kg repeated to maximum dose of 15 mg). Conversion to sinus rhythm occurred in 100% of patients for adenosine versus 73% for verapamil (P = NS). Indications for crossover from verapamil to adenosine were hypotension (one patient) and treatment failure with maximum drug dose (two patients). Reinitiation of tachycardia occurred in two adenosine- treated patients; in both, sinus rhythm was restored by a second injection of the previously effective adenosine dose. Transient mild symptoms, including flushing and chest tightness, occurred in 76% of adenosine patients.

Wickey JC, Keifer JC, Larach DR, et al: Heparin resistance after interoperative platelet-rich plasma harvesting. J Thorac Cardiovasc Surg 103:1172-1176, 1992

The effect of plateletpheresis and preoperative heparin therapy on heparin dose requirements were studied by review of records of 58 patients undergoing coronary artery surgery. Compared to patients undergoing prebypass autologous whole blood harvesting or no blood withdrawal, plateletpheresis insignificantly increased the heparin dose necessary to achieve anticoagulation (ACT 480 seconds), and significantly increased the total heparin dose during cardiopulmonary bypass. Preoperative heparin therapy signifi- cantly increased heparin dose to achieve anticoagulation (338 v 273 U/kg) and total heparin dose (499 v 422 U/kg).

Yau TM, Carson S, Weisel RD, et al: The effect of warm heart surgery on postoperative bleeding. J Thorac Cardiovasc Surg 103:1155-1163,1992

One hundred forty-six patients undergoing coronary artery surgery were randomly assigned to normothermic or hypothermic (25” to 29°C) systemic perfusion and nonrandomly to receive tranexamic acid (10 gm IV, n = 63) epsilon-aminocaproic acid (15 gm IV, n = 63) or no drug (controls, n = 20). Postoperative blood loss was significantly less in warm perfused control patients at 6 and 12 hours postoperatively than in cold perfused control patients. The difference was not statistically significant at twenty-four hours. Patients receiving either antifibrinolytic agent, regardless of perfu- sion temperature, bled less after all time periods than did cold control patients. Frequency of blood transfusion was not different between perfusion temperature groups, and insignificantly reduced in antifibrinolytic agent-treated patients compared to warm and cold controls. Postoperative platelet count was reduced in the hypothermic control group compared to all other groups.

Khuri SF, Wolfe JA, Josa M, et al: Hematologic changes during and after cardiopulmonary bypass and their relationship to the bleeding time and nonsurgical blood loss. J Thorac Cardiovasc Surg 104:94-107,1992

Measurement of blood loss and bleeding time in 85 patients during and after cardiopulmonary bypass demonstrated correla- tion between postoperative bleeding time and blood loss; both parameters were directly related to duration of cardiopulmonary bypass. Postoperative bleeding time correlated with patient’s skin temperature and plasma level of D-dimer; blood loss correlated with temperature and plasma C3 levels. Improvement in bleeding

time postoperatively is associated with increases in mean platelet volume and thromboxane B2 levels in shed blood. Fibrinolytic activity and complement activation play a role in bypass-induced platelet dysfunction, which may be alleviated postoperatively by rewarming and release of larger, younger platelets into circulation.

Inverse relationship between skin temperature and bleeding time in cardiac surgical patients is also demonstrated in another article in the same journal: Valeri CR, Kahbbaz K, Kahuri SF. et al: Effect of skin temperature on platelet function in patients undergoing extracorporeal bypass. J Thorac Cardiovasc Surg 104:108-116. 1992.

Ansell J, Klassen V, Lew R, et al: Does desmopres- sin acetate prophylaxis reduce blood loss after valvu- tar heart operations? A randomized, double-blind study. J Thorac Cardiovasc Surg 104:117-123,1992

Eighty-three patients undergoing valvular heart operations were randomized to receive desmopressin (0.3 kg/kg) or placebo after cardiac bypass. There were no significant differences in 24 hour blood loss (1,064 v 844 mL), red blood cell, platelet or fresh frozen plasma transfusion. or reexploration for hemorrhage between the desmopressin or control groups. Factor VIII activity was higher in the desmopressin group immediately after operation than in placebo group. Factor VIII activity, von Willebrand factor, or von Willebrand factor multimers did not correlate with blood loss. The authors also review the previously published literature on desmo- pressin acetate in cardiac operations.

Pearson PJ, Evora PRR, Ayrancioglu K, Schaff Hv: Protamine releases endothelium-derived relaxing fac- tor from systemic arteries. A possible mechanism of hypotension during heparin neutralization. Circula- tion 86:289-294,1992

Canine coronary, femoral and renal artery rings, with and without endothelium, were exposed to increasing concentrations of protamine in vitro. Protamine caused only a modest decrease in tension in arterial segments without endothelium. Concentration- dependent relaxation occurred in all endothelialized segments. which was significantly greater than in segments without endothe- lium. Endothelium-dependent relaxation induced by protamine was inhibited by L-NMMA, an inhibitor of endothelium-derived relaxing factor synthesis.

Tuman KJ, MC Carthy RJ, March RJ, et al: Morbidity and duration of ICU stay after cardiac surgery. A model for preoperative risk assessment. Chest 102:36-44,1992

Eleven variables were identified by univariate analysis of risk factors in 3,156 operations and logistic regression as important predictors of morbidity. Correlation was found between a simpli- fied additive model for clinical use and the logistic regression model. Both models were then tested prospectively in 394 patients demonstrating increasing morbidity, greater frequency of individ- ual complications, and prolonged ICU stays with ascending scores similar to that predicted by the reference group. Preoperative variables associated with increased risk of morbidity include emergency surgery, multivalve and combined coronary valve proce- dures, age greater than 75 years, recent myocardial infarction, and renal dysfunction.