Paradoxical response of plasma lipoprotein(a) in patients undergoing cardiopulmonary bypass.

Plasma lipid, lipoprotein and apolipoprotein levels are known to decrease after major surgery. Coronary artery bypass surgery additionally involves use of extracorporeal circulation by use of a cardiopulmonary bypass pump, which necessitates hemodilution due to saline dextrose infusion to prime the pump. To investigate changes in lipids, lipoproteins and apolipoproteins as well as changes in C-reactive protein and albumin we conducted a study on 22 patients undergoing cardiac surgery involving cardiopulmonary bypass. Timed arterial blood samples were taken before, during and after cardiopulmonary bypass. At the onset and during cardiopulmonary bypass a rapid and significant fall was observed in all lipids and lipoproteins except lipoprotein(a) with recovery to near basal levels by 72 h for cholesterol, triglycerides, high density lipoprotein cholesterol and albumin, while apolipoproteins AI and B remained below basal levels during the postoperative period up to 72 h. In contrast, lipoprotein(a) levels increased at the onset, doubled during cardiopulmonary bypass and remained elevated postoperatively. On the other hand, C-reactive protein levels fell at the onset and during cardiopulmonary bypass but they became markedly elevated postoperatively. When results were corrected for hemodilution, the response patterns remained unchanged. As lipoprotein(a) is both atherogenic and thrombogenic, its elevation during cardiopulmonary bypass may be clinically important.

Urinary bladder/pulmonary artery temperature ratio of less than 1 and shivering in cardiac surgical patients.

BACKGROUND: Temperature gradients that normally exist between body areas may be altered as a result of heat generated by shivering. METHODS AND POPULATION: Two core thermal gradients between pulmonary artery and urinary bladder were compared with shivering in 37 coronary artery bypass graft patients. Pulmonary artery and urinary temperature were measured every 15 minutes, and shivering was evaluated electromyographically. RESULTS: Shivering developed in 28 patients (76%). With shivering the pulmonary artery/urinary bladder temperature ratio was less than 1 but in the nonshivering group was greater than 1. Correlation (r value) between pulmonary artery and urinary temperature ranged from 0.93 to 0.99. Rate pressure product was higher in the shivering group than in the nonshivering group. A pulmonary artery/urinary bladder temperature ratio of less than 1 was seen with shivering in this subset of patients. CONCLUSION: Pulmonary artery and urinary bladder temperatures are readily available clinically. The combination of a ratio of less than 1 and an increase in rate pressure product should be considered suggestive of shivering in coronary artery bypass graft patients.

Relationship between urinary bladder and pulmonary artery temperatures: a preliminary study.

"Core" temperature and the proper methods for its assessment and management in cardiac surgical patients with hypothermia continues to be a concern for physicians and nurses. In this study we investigated the relationship between pulmonary artery and urinary bladder temperatures over a 6-hour period during rewarming in 14 (adult) patients in the intensive care unit after cardiopulmonary bypass. Bladder temperatures were 0.1 degree C to 0.2 degree C higher than pulmonary artery temperature with correlation coefficients of 0.94 to 0.99. This relationship continued for most of this period with significant mean differences clustering in the early and late period after admission. The significance of these small differences of temperatures and why the two temperatures reversed at certain time periods needs further investigation because the normal thermal gradients may be altered by the hypermetabolic activities consequent to shivering or iatrogenic overheating.

The benefit of the Hemonetics cell saver apparatus during cardiac surgery.

This retrospective chart review of 155 patients having coronary artery bypass graft surgery (CABG) over a two-month period determined whether the use of a cell saver apparatus (CSA) (1) reduced or increased the requirements for homologous blood; (2) increased the incidence of post-surgical bleeding; (3) was cost-effective. Two groups of patients were identified. Group 1 (n = 99) received both CSA processed red blood cells and homologous blood components. Requirement for homologous blood products was reduced in the first 24 hr after surgery (0.5 +/- 1.0 vs 1.3 +/- 1.8 units; P less than 0.05) when compared with Group 2 (n = 56) in whom only homologous blood products were utilized. More patients in Group 1 had no transfusion requirements (45 vs 8; P less than 0.05) and there was no increased risk of major haemorrhage. When the capital costs are included, utilization of the CSA was not cost-effective. We conclude that utilisation of a CSA was safe, with no increased risk of bleeding, reduced requirements for homologous blood transfusions, but added to the cost of the procedure.

Increased whole blood viscosity during coronary artery bypass surgery. Studies to evaluate the effects of soluble fibrin and poloxamer 188.

This study was designed to test the hypothesis that soluble fibrin complexes resulting from the trauma of surgery could produce elevated blood viscosity, to characterize the soluble fibrin polymers, and to evaluate in vitro the effect of a new hemorheologic agent, poloxamer 188, on viscosity in these abnormal situations. Ten patients undergoing aortocoronary bypass surgery were studied before and at various times after surgery. By 6 h after surgery, the mean hematocrit decreased by 23%, fibrinogen decreased 48%, and erythrocyte sedimentation rate decreased 33%, whole blood viscosity at a low shear rate rose on average of 69% and soluble fibrin rose 118%. Over the 6-day observation period, the concentrations of soluble fibrin paralleled the changes in viscosity, whereas the concentrations of fibrinogen varied nearly inversely with viscosity. The effects of various forms of fibrinogen and fibrin were tested by additions to normal blood. Soluble fibrin polymers, but not fibrin monomers, increased blood viscosity two to three fold. Poloxamer 188 reduced the viscosity of all patient samples to the normal range. These data support the hypothesis that increased whole blood viscosity at low shear rates is caused by hydrophobic adhesion of fibrin polymers to red cells and that poloxamer 188 normalizes viscosity by effectively disrupting the weak hydrophobic bonds.

Gentamicin solution for mediastinal irrigation: systemic absorption, bactericidal activity, and toxicity.

Local irrigation with gentamicin sulfate represents a possible substitute for neomycin sulfate, used for many years but now no longer available for use as an irrigation fluid. In this investigation, mediastinal irrigation with gentamicin was used in 12 patients who had experienced problems after a heart operation. The regimen employed for mediastinal irrigation with gentamicin was equipotent with that using neomycin. We sought to determine the degree of absorption and risk of either inadequate or toxic blood levels that might follow gentamicin absorption. Irrigation periods were short, ranging from one to four days and determined by measurements of plasma gentamicin concentration using radioimmunoassay evaluation. Systemic gentamicin absorption occurred in all patients. Toxic levels of higher than 8.0 micrograms/mL occurred and were size related, ie, correlated with smaller body weight and surface area, and sex related, ie, female sex. Larger-sized patients often had inadequate levels. Despite the potential risk from toxic blood levels, major increases in serum creatinine levels were not seen. These findings suggest that monitoring of plasma gentamicin levels during mediastinal irrigation with gentamicin is mandatory to avoid both inadequate treatment and toxicity.

Incidence of Cell-Saver contamination during cardiopulmonary bypass.

During regular bacteriological surveillance of cardiac surgical equipment and patients, the Cell Saver apparatus (CSA) was prospectively evaluated to determine if it represented an additional risk for infection. Nineteen patients were studied. After each operation, the effluent from the CSA was sterilely sealed for subsequent culture. A total of 42 aerobic and 42 anaerobic cultures were made. Postoperatively all patients were evaluated daily for four days and before discharge for clinical evidence of infection. Four patients had positive CSA cultures without evidence of postoperative clinical infection. Five patients in whom postoperative infectious complications developed had negative CSA cultures. Ten patients had negative CSA cultures and no evidence of postoperative infection. We conclude that the CSA does not appear to contribute to the risk of infection in cardiac surgical patients and that it is a safe adjunct to cardiac surgery.

Nalbuphine antagonism of fentanyl-induced ventilatory depression: a randomized trial.

The authors anesthetized 18 patients with good pulmonary and ventricular function for coronary artery bypass grafting with high doses of fentanyl. When the patients were arousable and their vital signs stable in the intensive care unit, the authors administered nalbuphine or placebo (randomly and double-blinded) until extubation criteria were met, and subsequently gave nalbuphine for analgesia. In one of ten placebo patients, tracheal extubation was accomplished without nalbuphine. This patient then retained CO2 and required nalbuphine; the other nine placebo patients could not be extubated after placebo trials and were given nalbuphine. In all other patients in both groups, tracheal extubation was successful following nalbuphine (median dose 60 micrograms/kg, range 30-180 micrograms/kg). One patient became renarcotized 4 h after tracheal extubation without an increase in plasma fentanyl concentration; he received an additional dose of nalbuphine and recovered without further incident. Nine patients required treatment with vasoactive agents or beta-blockers for hypertension or tachycardia associated with the administration of nalbuphine. Eight of 18 patients were not satisfied with nalbuphine analgesia, and required morphine for relief of their pain. Recurrent elevations of fentanyl concentrations in plasma were observed and appeared to be related to increasing motor activity. Nalbuphine is an effective opioid antagonist after fentanyl anesthesia, but its use is associated with side effects, and analgesia for the post-sternotomy patient may be unsatisfactory unless the dose is carefully titrated to the minimum required to antagonize respiratory depression.

Effect of positive end-expiratory pressure on excessive mediastinal bleeding after cardiac operations. A controlled study.

The efficacy of mechanical ventilation with positive end-expiratory pressure (PEEP) in the therapy of excessive mediastinal hemorrhage following cardiac operations remains unproved. One hundred thirty-nine patients undergoing elective myocardial revascularization were divided into two groups on the basis of preoperative hematologic evaluation: Group I, 94 patients with no history of hematologic abnormalities and a normal coagulation profile; Group II, 45 patients with a recent use of antiplatelet medications and/or a prolonged template bleeding time. Both groups were randomized to receive mechanical ventilation with 10 cm H2O of PEEP or no PEEP beginning 1 hour after operation and continuing for an 8 hour study period. Mean blood loss at 8 hours (BVt) was not significantly different between PEEP and control patients in either group. Fifty-seven patients in Groups I and II had mediastinal bleeding in excess of 180 ml/hr at the initiation of the study period. There was no significant difference in mean BVt or mean hourly chest tube output with or without PEEP in either group of this subset. In view of the lack of demonstrable efficacy in decreasing mediastinal hemorrhage and the potential of adverse hemodynamic effects, PEEP should no longer be used for therapy of excessive bleeding after cardiac operation, especially in patients with reduced cardiac reserve.

Myxoedema and open heart surgery: anaesthesia and intensive care unit experience.

Myxoedema has been considered a major anaesthetic risk which could be increased by concurrent heart disease. Thyroid ablation with the production of myxoedema has, in the past, been used to control intractable angina. Eight ablated patients (Group I) and five patients with heart disease and incidental hypothyroidism (Group II) presented for open heart surgery. Management included diazepam-narcotic anaesthesia in generally reduced doses, careful monitoring and the use of digoxin, steroids and I-thyroxin given during or after operation. All patients survived. A number of the anaesthetic considerations and potential problems with myxoedema are discussed.

Calculator assisted cardiorespiratory monitoring.

The newest card-programmable calculators are more flexible and powerful enough to process a variety of complex data, derive appropriate variables, and print the titles of the values and the results. These capabilities make the information derived from aggressive cardiorespiratory monitoring more usable, and specifically, have increased the benefits from the use of pulmonary artery catheters and techniques such as phonocardiography. A program using 800 steps and 20 memory registers and an illustration of the value of both the monitoring and calculator in ICU care are presented.

Vasodilator therapy after cardiac surgery: a review of the efficacy and toxicity of nitroglycerin and nitroprusside.

Eight-five patients who required vasodilator therapy in the postoperative period after cardiac surgery were studied to compare the haemodynamic effects of nitroglycerin and nitroprusside, to evaluate local and systemic toxicity, and to develop long-range dosage recommendations. Ninety-one per cent of the patients received the vasodilators for postoperative hypertension, while nine per cent had low output syndromes. Both drugs significantly decreased blood pressure and central venous pressure, and increased heart rate. Nitroglycerin decreased both right and left ventricular filling pressures more than nitroprusside. No local toxicity or methaemoglobinaemia was found with either drug. Elevated thiocyanate levels were detected in 44 per cent of the nitroprusside group; however, none of the patients developed progressive metabolic acidosis. For prolonged infusions we found that nitroprusside at 1 microgram.kg-1.min-1 and nitroglycerin at 0.5 microgram.kg-1.min-1 were without significant toxicity.

Intraoperative hemodialysis during cardiopulmonary bypass in chronic renal failure.

This report describes the features and the course of a patient on maintenance hemodialysis in whom infective endocarditis of the aortic valve ensued. The subsequent development of intractable congestive heart failure necessitated aortic valve replacement. Use of intraoperative hemodialysis, facilitating the intraoperative and postoperative management of the patient, is described. Following valve replacement the patient did well with no evidence of congestive heart failure.