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Biomedical subjects

R W Dunbar

Publications and source records attributed to R W Dunbar.

At least 19 recordsLinked to original sources
PubMed1977

Autologous blood transfusion during cardiac surgery. A re-evaluation of three methods.

The use of autologous blood transfusion to decrease blood bank requirements and improve coagulation parameters during cardiac surgery is still controversial. This study was undertaken to re-evaluate three methods of autologous blood transfusion. Before bypass, 13 to 15 percent of the patient's estimated blood volume was removed and stored with either CPD or heparin at room temperature and returned via a peripheral vein after bypass. All patients had significant abnormalities in their PTT, PT, and platelet counts after bypass. Heparinized autologous blood removed from the vena cava cannula was the only technique which significantly improved the PTT and platelet count. Total blood bank requirements were significantly less for the autologous blood groups than for controls. There was a saving of 18 percent in banked blood requirements. Fresh frozen plasma and platelets were not found to be routinely needed during cardiac surgery.

Blood Cell Count↗
PubMed1976

Nitroglycerin infusion during coronary-artery surgery.

The effects of an intravenous infusion of nitroglycerin were studied in 20 acutely hypertensive patients during coronary-artery surgery. Eight patients had histories of essential hypertension and six had been treated for it. They were anesthetized with morphine, diazepam, N2O, O2, pancuronium, and enflurane. Control measurements were obtained after sternotomy. Nitroglycerin was then administered until the blood pressure returned to normal, and the measurements then repeated. The mean dose of nitroglycerin was 80.0 +/- 4.7 mug/min, or 0.96 mug/kg/min. This produced significant decreases (P less than .05) in systolic, diastolic, and mean arterial blood pressures, central venous pressure, pulmonary capillary wedge pressure, systemic vascular resistance, and left ventricular stroke work index. Cardiac index, stroke index, and heart rate were unchanged. Two indices of myocardial oxygen demand (rate-pressure product and tension-time index) were significantly decreased by nitroglycerin (P less than .005). Fifty per cent of the patients had improvement in ST-segment depression on the electrocardiogram. These findings demonstrate that nitroglycerin can be safely administered intravenously during operation, and suggest that nitroglycerin decreases myocardial oxygen demand and relieves myocardial ischemia.

Adult↗
PubMed1976

The perioperative management of pericardial tamponade.

A case report of a patient with acute pericardial tamponade is presented. The etiology, pathophysiology, and management of cardiac tamponade is discussed. Preoperative management includes volume expansion, administration of catecholamines, and pericardiocentesis. Intraoperatively, monitoring should include continuous measurement of arterial and central venous pressures. Ketamine has been found to be very useful in these patients.

Anesthesia, General↗
PubMed1976

Anesthetic technic using profound hypothermia for correction of congenital heart defects in infants and small children.

Profound hypothermia can be a useful adjunct in the intraoperative management of infants and small children undergoing surgical correction of congenital heart defects. A case description of a 5 1/2-month-old male infant with total anomalous pulmonary venous drainage who had successful repair using surface cooling, cardiopulmonary bypass, and pump cooling to 20 C with intermittent periods of low systemic blood flow illustrates the technic. Discussed are the value of surface cooling before cooling on cardiopulmonary bypass, physiologic changes affecting the intraoperative and postoperative course, and the major risks and advantages of the technic.

Arrhythmias, Cardiac↗
PubMed1975

Chromosomal identification of eight species of the subgenus Edwardsellum near and including Simulium (Edwardsellum) damnosum Theobald (Deptera: Simuliidae).

Examinations of the banding pattern of polytene chromsomes from larval salivary glands of the population in west Africa once thought to be a single species, Simulium (Edwardsellum) damnosum, revealed eight species all within the Nile subgroup of the complex. The following names were proposed: S. (E.) squamosum Enderlein, S. (E.) yahense n.sp., S. (E.) soubrense n.sp., S. (E.) sanctipauli n.sp., S. (E.) dieguerense n.sp., S. (E.) damnosum Theobald, S. (E.) sirbanum n.sp. and S. (E.) sudanense n.sp. Micromorphological characters by which there species are distinguished include interspecific inversions, different sets of intraspecific inversions, different sets of sex chromosomes and a few micromorphological features other than the banding pattern. By following the logical sequential development of interspecific inversions both a key to the species and a phylogenetic chart have been drawn up. Analysis of the proportions of alternate sequences for random distribution or not with ther Hardy-Weinberg equation have confirmed the existance of distinct populations, uncovered an example of incipient speciation and showed the existance of a genetic variant of S. damnosum which could possible colonize below dams.

Africa, Western↗
PubMedDate not supplied

Propranolol and cardiac surgery: a problem for the anesthesiologist?

Propranolol therapy has been implicated as a cause of myocardial depression and increased morbidity and mortality in patients undergoing coronary artery surgery. The authors reviewed 169 consecutive patients undergoing cardiac surgery, of whom 143 had been taking propranolol, with regard to preoperative administration of propranolol and intraoperative or postoperative complications. Patients taking propranolol until 24 hours before surgery showed no increased incidence of hypotension or bradycardia before cardiopulmonary bypass. Hypotension after bypass was no more common in patients off propranolol 12 to 48 hours than in patients who either discontinued the drug over 48 hours before operation or had never taken the drug. Myocardial contractility as measured by systolic time intervals was normal 24 to 48 hours after stopping propranolol therapy. Five patients had preoperative myocardial infarctions within 48 hours of discontinuing the drug. The operative mortality rate was 4 percent in patients taking propranolol within 48 hours of surgery and 6 percent in all other patients. Seven risk factors, other than propranolol, were identified in those patients requiring inotropic support. The authors conclude that propranolol can be given safely within 24 to 48 hours of coronary artery surgery provided the patient is a satisfactory candidate for myocardial revascularization.

Angina Pectoris↗
PubMedDate not supplied

Propranolol and surgical anesthesia.

The potential danger of anesthetizing a patient on beta-adrenergic blockade therapy has long been recognized. The cases of 73 patients taking propranolol and anesthetized for non-cardiac operations were reviewed with regard to preoperative administration of propranolol and intraoperative and postoperative complications. Of these patients, 72 percent took propranolol to within 24 hours of operation and 85 percent took it to within 48 hours. The mean dose of propranolol was 77 mg/day (range, 10 to 320 mg/day). Anesthetic technics and agents included enflurane, halothane, N2O-narcotic-relaxant, and spinal anesthesia. There were only three episodes of hypotension, all of which responded to a decreased depth of general anesthesia, IV fluid administration, and, in one patient, a small dose of a vasopressor. There were no intraoperative or postoperative deaths. It is concluded that if propranolol is indicated for medical control of the patient's symptoms, it need not be discontinued before surgical anesthesia.

Anesthesia↗