Critical coronary artery obstruction.
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Body Temperature↗
Biomedical subjects
R W Landymore
Publications and source records attributed to R W Landymore.
Importance of topical hypothermia to ensure uniform myocardial cooling during coronary artery bypass.
Recent reports have suggested that the delivery of cardioplegia to regional myocardium is impaired in patients with severe coronary artery disease. This study was designed to determine whether or not topical hypothermia is a necessary adjunct to systemic hypothermia and potassium cardioplegia to provide adequate cooling in regional myocardium supplied by stenotic or occluded coronary arteries. Twenty-two patients ranging in age from 47 to 68 years were included in the study. Patients were placed on bypass and cooled to 28 degrees C. Temperature was measured over the right and left coronary artery distributions. The aorta was then cross-clamped and 1,000 cc of potassium blood cardioplegia, 5.7 degrees to 11 degrees C (mean 8.7 degrees), was infused into the aortic root at a mean pressure of 99 mmHg. Temperature was measured and 6 L of cold electrolyte (Plasma-lyte) solution, 2.3 degrees to 5.1 degrees C (mean 3.5) was poured over the heart into the pericardial well. The temperature measurements were then repeated. Myocardial temperature in regional myocardium supplied by normal coronary arteries after the injection of cardioplegia was less than 15 degrees C. However myocardium distal to a severe stenosis or complete occlusion was significantly warmer (p less than 0.001). Topical hypothermia reduced myocardial temperature to less than 15 degrees C in regional myocardium supplied by severely diseased vessels (p less than 0.001). These data demonstrate that the combination of systemic hypothermia and potassium cardioplegia alone does not provide adequate myocardial cooling in patients with severe coronary artery disease and emphasize the need for intraoperative myocardial temperature monitoring to ensure optimal protection during the ischemic period.
Aged↗
Suppression of renin production in patients undergoing coronary artery bypass.
Twenty patients undergoing elective myocardial revascularization for coronary insufficiency were divided into two equal groups. In 10 patients, propranolol was discontinued 24 hours before operation while the remaining patients received propranolol until the day of operation. Plasma renin was elevated in the intensive care unit in the control group (p < 0.05) whereas patients receiving propranolol did not demonstrate significant elevation of plasma renin. Systemic vascular resistance was elevated in both groups in the intensive care unit (p < 0.05) and was associated with hypertension as defined by a blood pressure of greater than or equal to 160/100 mm Hg in 80% of the control patients and 70% of patients receiving propranolol. We conclude from this study that renin metabolism does not contribute significantly to the production of hypertension following coronary artery operation.
Adult↗
Hypertension following myocardial revascularization: its prevalence and etiology.
Of 11 patients who underwent elective aortocoronary bypass operation using nonpulsatile flow with moderate hypothermia (28 degrees C), 8 had hypertension defined as blood pressure of 160/100 mm Hg or greater. The plasma renin level was not elevated during bypass by postoperatively in the intensive care unit it became significant (P < 0.05) elevated. An increase in the release of renin was associated with a rise in systemic vascular resistance and coincided with the onset of hypertension. Although the values of plasma catecholamines were elevated during bypass and in the intensive care unit, they did not appear to contribute appreciably to increases in systemic resistance. The authors conclude that an increase in the release of renin is associated with increased vascular resistance and elevated blood pressure following myocardial revascularization.
Adult↗
Does vascular steal occur following femorofemoral bypass grafting?
Vascular steal has been reported following aortoiliac and crossover femoral vascular reconstruction. Although the steal phenomenon has been described in clinical situations some have denied its existence. The authors attempted to determine whether or not vascular steal occurs after femorofemoral bypass operation. Fifteen adult mongrel dogs underwent femorofemoral bypass grafting. Stenosis of the iliac artery was simulated with a specially designed device. Blood flow was measured with the femoral graft open and closed in combination with superficial femoral and deep femoral artery obstruction in the donor and recipient circulations. There was no statistically significant decrease in flow to the donor leg in any situation. Thus the authors conclude that vascular steal does not occur following femorofemoral bypass operation.
Animals↗
Does pulsatile flow influence the incidence of postoperative hypertension?
Twenty patients undergoing primary elective aorta--coronary artery bypass were divided into two equal groups, both receiving identical premedication, anesthetic, and pump primes. The control patients received hypothermic nonpulsatile flow and the study patients received hypothermic pulsatile flow. Hypertension, defined as a pressure of 160/100 mm Hg or higher, was observed in 80% of the control patients and 20% of the patients receiving pulsatile flow (p less than 0.05). Serial renin measurements demonstrated maximum values in the intensive care unit and coincided with the onset of postoperative hypertension in the control patients. Those patients who had received pulsatile flow did not demonstrate notable renin stimulation. Catecholamines were markedly elevated during bypass and in the intensive care unit, but there was no significant difference between the two groups. Peripheral vascular resistance was not significantly lower with pulsatile flow, except in the first study performed in the intensive care unit. We conclude that catecholamines and the renin-angiotensin system contribute to the production of postoperative hypertension and that pulsatile flow diminishes renin stimulation. Pulsatile flow results in a decreased incidence of postoperative hypertension.
Cardiopulmonary Bypass↗
Effect of cardiopulmonary bypass and hypothermia on pancreatic endocrine function and peripheral utilization of glucose.
Extracorporeal circulation has been reported to produce abnormalities of glucose, metabolism. Pancreatic endocrine function and peripheral glucose utilisation were studied in 11 nondiabetic patients who underwent myocardial revascularization. Nonpulsatile flow with hemodilution and moderate hypothermia to 28 degrees C were used in each case. Following the onset of cardiopulmonary bypass, serum glucose values rose rapidly to a mean of 972 mg/dl (54.0 mmol/l) and were associated with high circulating concentrations of insulin in the range of 216 microU/ml [1549.8 pmol/l]. High circulating concentrations for both insulin and glucose were maintained throughout the bypass period. These returned to normal postoperatively when the patient was in the recovery room. The results of this study indicate that both the pancreatic endocrine response and the peripheral utilization of glucose are impaired during cardiopulmonary bypass with hemodilution and moderate hypothermia to 28 degrees C.
Adult↗
Inaccuracy of serum lipid measurements after open heart operations.
Serum lipids were measured in 20 patients before and within one week following coronary artery bypass. The total serum cholesterol was decreased by 45%, while low density lipoprotein cholesterol and high density lipoprotein cholesterol were reduced by 50% and 30%, respectively. Hemodilution for cardiopulmonary bypass temporarily lowers serum lipids, indicating that screening procedures for hyperlipidemia should not be performed immediately following cardiac operations.
Adult↗
Correlation between the effects of aspirin and dipyridamole on platelet function and prevention of intimal hyperplasia in autologous vein grafts.
Fifty-four adult mongrel dogs receiving a lipid-supplemented diet were used to determine the effects of aspirin and dipyridamole on vein graft intimal hyperplasia. Twenty-one animals received the diet alone, 17 animals received a combination of dipyridamole and aspirin, while a further 16 animals received dipyridamole. Segments of undistended external jugular vein were anastomosed to bilaterally-divided femoral arteries. The vein grafts were harvested at six weeks and intimal thickness was measured with a Zeiss computerized microscope. Serum cholesterol, prothrombin time, partial thromboplastin time and clotting time was measured before the diet and at two, four and six weeks after operation. Plasma thromboxane B2 (TXB2) and the metabolite of prostacyclin I2 (6-keto PGF1 alpha) were determined by radioimmunoassay before and four weeks following operation. A similar and significant increase in serum cholesterol was observed in all animals receiving lipid supplementation. Platelet counts were significantly decreased in those animals receiving a combination of aspirin and dipyridamole while all other hematological parameters remained unchanged. Plasma TXB2 and 6-keto PGF1 alpha were unaffected by dipyridamole but were significantly decreased in those animals receiving the combined drug regimen. Intimal thickness measured 59 +/- 6 micron at six weeks in the controls. Dipyridamole reduced intimal thickness to 26 +/- 2 micron while aspirin and dipyridamole decreased intimal thickness to 28 +/- 2 micron. The data indicate that dipyridamole was as effective in reducing smooth muscle cell proliferation as the combination of aspirin and dipyridamole. Furthermore, the data suggest that antiplatelet drug regimens may reduce intimal thickening in autologous vein grafts by a mechanism other than affecting the thromboxane:prostacyclin ratio.
6-Ketoprostaglandin F1 alpha↗
Does pulsatile flow improve glucose tolerance during extracorporeal circulation.
The present study was designed to determine the effect of pulsatile glow on glucose tolerance during cardiac surgery. Twenty patients were divided into two equal groups; ten patients receiving non-pulsatile bypass and the remaining patients receiving pulsatile flow. Patients receiving pulsatile flow had significantly lower systemic resistance in the intensive care unit. Glucose tolerance, however, was similar in both patient groups. Insulin secretion was impaired and serum glucose remained elevated throughout the period of extracorporeal circulation. We conclude from this study that glucose tolerance is unaffected by pulsatile flow.
Blood Glucose↗