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Biomedical subjects

T J Gardner

Publications and source records attributed to T J Gardner.

At least 163 records · Page 9Linked to original sources
PubMed1979

Comparison of myocardial protection with nifedipine and potassium.

Nifedipine, a slow-channel calcium blocker, is thought to provide useful myocardial protection during prolonged total ischemia and reperfusion. An isolated, isovolumic, feline heart model was used to asses the effectiveness of nifedipine in both cardioplegic (100 microgram/10 ml) and noncardioplegic (10 microgram/10 ml) doses for providing myocardial preservation during 90 minutes of hypothermic ischemic arrest and 45 minutes of normothermic reperfusion. Use of nifedipine was compared to hypothermia (27 degrees C) alone and to hypothermia with potassium cardioplegia. Ventricular function was assessed by recovery of isovolumic left ventricular developed pressure and dP/dt. Myocardial carbon dioxide tension (PCO2) and myocardial oxygen tension (PO2) were measured by mass spectrometry. Potassium cardioplegia and the higher dose of nifedipine resulted in immediate asystole. The rates of rise of PCO were greatest in the group receiving 10 microgram nifedipine and in the control group. The rates of rise in the two cardioplegic groups were significantly lower. Recovery of ventricular function was significantly lower with low-dose nifedipine than with potassium cardioplegia. Higher dose nifedipine resulted in a return of function, which was no different than with potassium cardioplegia. Morphologic protection was better with higher dose nifedipine and potassium cardioplegia than with either low-dose cardioplegia or hypothermia alone. These results demonstrate that nifedipine in a cardioplegic dose results in preservation of myocardial structure and function that is similar to that obtained with potassium cardioplegia. In lower noncardioplegic dose, nifedipine does not appear to offer additional protection compared to hypothermia alone. Whether persistent depression of ventricular contractility will limit nifedipine's clinical usefulness as a myocardial protection agent will require further study.

Animals↗
PubMed1979

Potassium-induced cardioplegia during normothermic cardiac arrest. Morphologic study of the effect of varying concentrations of potassium on myocardial anoxic injury.

Most corrective procedures as well as myocardial revascularization require a period of cardiac arrest, and numerous methods have been proposed to protect the myocardium during this ischemic episode. Potassium-induced cardioplegia is one method that appears to be of benefit in this setting. Since it is recognized that myocardial necrosis may result at very high doses of potassium, we examined the effect of varying concentrations of potassium on myocardial anoxic injury. Using an isolated rat heart preparation, we evaluated anoxic injury occurring with cardioplegic solutions containing various concentrations of K+, ranging from 15 to 200 mEq. per liter, during a 50 minute normothermic arrest followed by 60 minutes of reperfusion. The transverse histologic sections of the left ventricular myocardium were analyzed for contraction band injury by morphometric and qualitative methods. Among the 62 animals studied the least severe anoxic injury was seen with K+ cardioplegia at concentrations of 25 and 30 mEq. per liter. At lower and higher concentrations there was little difference between the hearts exposed to anoxia with or without K+ cardioplegia. Potassium administered in very high doses, i.e., 100 or 200 mEq. of K+ per liter, led to contracture and extensive myocardial cell injury. This study suggests that potassium-induced cardioplegia is effective in reducing cell injury due to anoxia, and in this model an optimal concentration range was 25 to 30 mEq. per liter.

Animals↗
PubMed1979

Fetal Monitoring during cardiopulmonary bypass for removal of a left atrial myxoma during pregnancy.

A 26-year-old woman was discovered to have a left atrial myxoma during the second trimester of pregnancy. Because of concern about potential complications from the cardiac tumor, it was elected to operate on this patient using cardiopulmonary bypass and careful fetal heart rate monitoring. Excision of the myxoma was carried out uneventfully and a healthy male infant was born at full term 16 weeks later. Problems associated with maternal extracorporeal circulation during pregnancy are discussed. This case illustrates the feasibility and safety of performing open-heart surgery during pregnancy, utilizing a simple external fetal monitoring technique.

Adult↗
PubMed1978

Improved myocardial performance in postoperative cardiac surgical patients with sodium nitroprusside.

Myocardial performance in the immediate postoperative period was studied 49 cardiac surgical patients treated with nitroprusside alone. With a thermodilution catheter positioned in the pulmonary artery, cardiac output was calculated and cardiac index, systemic vascular resistance index, and stroke work index were derived before after treatment with nitroprusside. The drug was a administered to all patients because of elevated systemic vascular resistance index. Based on their mean arterial pressure and cardiac index before treatment, the patients fell into two groups. Group I patients (N = 25) had elevated mean arterial pressure and normal cardiac index. Group II patients (N = 24) had normal mean arterial pressure and subnormal cardiac index. Nitroprusside administration resulted in a significant reduction of systemic vascular resistance index in all patients. In Group I the mean arterial pressure was lowered significantly while cardiac index increased only slightly. In Group II there was no change in arterial pressure, but cardiac index improved significantly. The results not only confirm that nitroprusside is effective in managing postoperative hypertension, but also demonstrate that in patients with postoperative left ventricular failure, the drug can improve cardiac output by reducing systemic vascular resistance without significantly lowering arterial blood pressure.

Adult↗
PubMed1978

Effects of calcium administration during post-ischemic reperfusion on myocardial contractility, stiffness, edema, and ultrastructure.

Previous investigators have suggested that calcium may play a role in the pathogenesis of myocardial cell damage following ischemia and reperfusion. Twenty-six in-situ blood perfused isovolumic canine preparations were divided into four groups. Group I dogs were maintained normocalcemic during 45 min of reperfusion following 45 min of hypothermic (27 degrees C) ischemic arrest; Group II dogs received CaCl2 (7 mg/kg) after 15 min of reperfusion; Group III dogs received citrate solution (0.8 ml/kg citrate-phosphate-dextrose [CPD]) after 15 min of reperfusion; Group IV dogs received 7 mg/kg of CaCl2 at 5 min after receiving the same citrate dose as Group III after 15 min of reperfusion. In Group II hearts, calcium improved the left ventricular contractility (P < 0.05 vs Group I) without causing additional cellular or subcellular injury. Calcium also appeared to increase myocardial stiffness (alpha(n)) compared to Group I hearts (P < 0.01). In Group III hearts, citrate reduced contractility (P < 0.01 vs Group I) and increased myocardial edema (P < 0.005 vs Group I) without any apparent improvement in cellular or subcellular preservation. In Group IV hearts, calcium reversed the depression of contractility caused by citrate, resulted in no additional morphologic injury, increased myocardial stiffness compared to Group I or Group III (P < 0.005), and minimized myocardial edema (P < 0.005 vs Group I or III). These results suggest that calcium administered after 15 min of reperfusion improves the depression of contractility that follows hypothermic ischemic arrest without causing additional myocardial damage.

Animals↗
PubMed1978

Autotransfusion of shed mediastinal blood after cardiac surgery: a prospective study.

In a randomized prospective study of patients having cardiac surgery, autologous blood collected from mediastinal tubes was autotransfused preferentially in 63 patients (ATS), whereas 51 patients received bank blood for transfusion (control). Comparison of the two groups showed no significant difference in regard to age, sex, operations performed, or total postoperative bleeding (ATS 813 +/- 121 ml. per square meter versus control 711 +/- 93 ml. per square meter; N.S.) Although mean postoperative blood replacement was similar in the two groups (ATS 4.3 +/- 0.6 units per patient versus control 4.8 +/- 0.6 units per patient), requirements for transfusion of stored bank blood were reduced by 50 percent in the ATS group (ATS 2.4 +/- 0.3 units per patient versus control 4.8 +/- 0.6 units per patient; p less than 0.005). Coagulation studies demonstrated that this blood was defibrinogenated; yet it contains significantly more platelets and clotting factors than does bank blood. In this study, autotransfusion of shed mediastinal blood was safe and simple. It significantly reduced bank blood requirements and resulted in substantial financial savings for the patients and the hospital.

Blood Cell Count↗
PubMed1978

Effects of procaine-induced cardioplegia on myocardial ischemia, myocardial edema, and postarrest ventricular function. A comparison with potassium-induced cardioplegia and hypothermia.

The extent of myocardial protection afforded by a procaine cardioplegic solution during cardiac ischemia has been evaluated and compared with the protection seen using a potassium cardioplegic solution. An isolated cat heart model was employed, and ventricular function parameters, intramyocardial gas tensions, and postischemic myocardial edema were measured and compared following 60 minutes of induced ischemia at 37 degrees C. and 27 degrees C. There was no significant improvement in recovery of postarrest ventricular function when procaine cardioplegia was used during normothermic ischemia. When used at 27 degrees C., however, both cardioplegic solutions were associated with significantly better recovery of postarrest ventricular function, although there was less myocardial edema formation in the potassium-treated hearts. Results of this study indicate that procaine-induced cardioplegia provides myocardial protection during anoxic cardiac arrest which is additive to that afforded by hypothermia alone. In addition, procaine cardioplegia results in postarrest functional recovery which is similar to that seen with potassium cardioplegia.

Animals↗
PubMed1978

Cake kidney with abdominal aneurysm.

The authors describe a case of cake kidney occurring in association with a ruptured abdominal aneurysm with special reference to preoperative evaluation by angiography. They discuss the need to prepare these patients for possible in-vivo or ex-vivo renal manipulation during the removal of the aneurysm and the placement of the Dacron graft.

Aorta, Abdominal↗