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Biomedical subjects

D G Lappas

Publications and source records attributed to D G Lappas.

69 records · Page 4Linked to original sources
PubMed1978

The effect of hemodilution with albumin or Ringer's lactate on water balance and blood use in open-heart surgery.

To determine the effect of intraoperative albumin administration on blood use, water balance, and postoperative clinical course, we studied two groups of adult cardiac surgical patients. Group I (30 patients) received 25 gm of albumin during withdrawal of 2 units of blood prior to cardiopulmonary bypass (CPB) and 50 gm of albumin in the oxygenator prime. Group II (32 patients) received no albumin prior to the end of CPB. No difference in clinical course could be identified, nor was there a significant difference in blood use. Group I patients had lower hematocrit values intraoperatively from the time of blood withdrawal until the conclusion of operation. Coronary artery bypass operations were associated with greater positive water balance than were heat valve operations. Forty-three percent of the patients having coronary artery bypass grafting had a positive water balance greater than 5 liters, whereas 50% of those undergoing valve procedures had a balance less than 3 liters. We conclude that the principal effect of withholding albumin under these circumstances is to increase net positive water balance. The greater positive water balance does not appear to be detrimental.

Adult↗
PubMed1978

Systemic and pulmonary effects of nitroprusside during mitral valve replacement in patients with mitral regurgitation.

The effects of sodium nitroprusside on the systemic and pulmonary circulation were assessed in 17 patients with severe mitral regurgitation (MR) during mitral valve replacement. In nine patients, MR was related to rheumatic heart disease, in six resulted from acute myocardial infarction, and in two was due to subacute bacterial endocarditis. Nitroprusside was administered intraoperatively at an infusion rate of 10 to 65 mcg/min. During vasodilation therapy, forward stroke volume increased from 34 +/- 2.8 to 46 +/- 4.8 ml, while left ventricular filling pressure decreased from 28.7 +/- 1.9 to 20.6 < or = 1.8 mm Hg. There was a significant decrease in systemic vascular resistance (from 2379 +/- 204 to 1646 +/- 161 dynes.sec.cm-5) and mean arterial pressure (from 89.8 +/- 4 to 78.1 +/- 5 mm Hg). Similarly, a significant decrease was observed in both pulmonary vascular resistance (from 414 +/- 45 to 208 +/- 31 dynes.sec.cm-5) and mean pulmonary arterial pressure (from 42.5 +/- 2.5 to 29.7 +/- 2.5 mm Hg) with nitroprusside. In all patients there was a decrease in the magnitude of the peak V wave of the pulmonary capillary wedge pressure (from 45.2 +/- 3.9 to 26.1 +/- 3.1 mm Hg). These findings suggest that judicious intraoperative administration of nitroprusside improves right and left ventricular function in patients with MR undergoing mitral valve replacement, by increasing forward stroke volume while decreasing ventricular filling pressures and vascular resistance (preload and afterload).

Blood Pressure↗
PubMed1976

Kinetics of high-dose intravenous morphine in cardiac surgery patients.

Ten patients received 1.0 mg/kg of morphine sulfate by constant-rate intravenous infusion at 5 mg/min over 9 to 27 min. Multiple arterial blood samples were drawn during the first 30 to 151 min after termination of the infusion, prior to institution of cardiopulmonary bypass. Postinfusion plasma concentrations were fitted by computer to biexponential functions consistent with a 2-compartment open pharmacokinetic model. Mean (+/- SE) pharmacokinetic parameters were: volume of central compartment, 0.09 +/- 0.03 L/kg; total apparent volume of distribution, 1.02 +/- 0.09 L/kg; distribution T 1/2, 0.90 +/- 0.09 min; apparent elimination T 1/2, 137 +/- 14 min; total clearance, 378 +/- 63 ml/min. Thus distribution of morphine is very rapid, but the apparent volume of distribution is only slightly larger than body weight, suggesting limited tissue uptake. Since apparent elimination T 1/2s are similar to those reported after smaller doses, evidence of saturable or capacity-linked elimination is lacking. Total clearances, representing mainly hepatic clearance, averaged about 25% of hepatic blood flow, suggesting clinically important first-pass metabolism of oral morphine.

Adult↗
PubMed1976

Pulmonary vasomotor tone during general anesthesia and deliberate hypotension in man.

Pulmonary and systemic hemodynamic responses to administration of pentolinium (0.3 mg/kg) were studied in eight patients undergoing total hip replacement during N2O-halothane anesthesia with PaCO2 maintained at 35-40 mm Hg. Measurements were made prior to induction of anesthesia; 20 minutes after induction; 45 minutes after induction but prior to pentolinium administration; 10, 20, and 60 minutes after administration of pentolinium; 15 minutes after AP recovered to within 10 per cent of baseline values. The reduction in AP produced by pentolinium was associated with significant decreases in both SVR and LVFP (estimated by measuring PA0 via a Swan-Ganz catheter). The profound and significant reductions in calculated PVR were more pronounced than those in SVR. Since PVR decreased in the face of reductions in both pulmonary arterial and left atrial pressures despite a significant increase (at 10 minutes) or no change (at 20 and 60 minutes) in pulmonary blood flow, the results suggest an active decrease in pulmonary vascular tone, presumably due to autonomic inhibition by pentolinium. Both LVSWI and RVSWI decreased significantly following injection of pentolinium. HR X SAP, an indirect index of MV02, decreased significantly following an initial increase at 10 minutes. Presumably these effects of pentolinium were conspicuous because N2O-halothane anesthesia altered the baseline of pulmonary vascular tone.

Adolescent↗
PubMed1976

Myocardial ischemia due to infrarenal aortic cross-clamping during aortic surgery in patients with severe coronary artery disease.

Hemodynamic measurements were performed and ECG recorded before and shortly after infrarenal aortic cross-clamping during operation for abdominal aortic aneurysm in five patients without evidence of heart disease (group I) and in ten patients with severe coronary artery disease (group II). All patients sustained an increase in systemic arterial pressure. Group I demonstrated a decrease in pulmonary artery, pulmonary capillary wedge (PCW), and central venous pressures when the aorta was clamped, whereas group II demonstrated an increase. The difference in response of the groups is significant (P less than 0.05). All three patients who responded to cross-clamping with increases of 7 mm Hg or greater in PCW demonstrated myocardial ischemia during cross-clamping. None of the values measured prior to cross-clamping predicted with certainty the response to cross-clamping. Sodium nitroprusside reversed the elevation of left ventricular filling pressure in all three patients, and in two patients, relieved evidence of myocardial ischemia concurrently. In the third patient, ventricular irritability was abolished by lidocaine and did not recur. We conclude that infrarenal aortic cross-clamping may cause myocardial ischemia in patients with severe coronary artery disease. This ischemia may be predicted by a rise in PCW at the time of cross-clamping, and vasodilator therapy is indicated in such patients.

Aged↗
PubMed1976

Hemodynamic effects of nitroprusside infusion during coronary artery operation in man.

The hemodynamic response to vasodilator therapy with sodium nitroprusside has been assessed in 33 patients with severe coronary artery disease (CAD) during coronary artery operation. The patients were divided into three groups; Group 1 included seven patients with CAD and normal left ventricular filling pressure (LVFP less than 12 mm Hg); Group 2 included 18 patients with CAD and chronic left ventricular (LV) dysfunction (LVFP greater than 12 mm Hg) and Group 3 included eight patients with CAD and acute LV dysfunction (LVFP greater than 12 mm Hg) associated with an intraoperative hypertensive episode. Nitroprusside was administered intraoperatively at an initial infusion rate of 10-15 mcg/min and the rate was gradually increased thereafter until the criteria for effective therapy were satisfied. The effective dose ranged from 10-120 mcg/min with an average of 52 +/- 4 (SEM) mcg/min. In all three groups, pulmonary and systemic arterial pressure, right and left ventricular filling pressure, and pulmonary and systemic vascular resistance decreased significantly with nitroprusside infusion. Heart rate increased significantly in Group 1 and remained unchanged in Group 2 and 3. Heart rate X systolic arterial pressure decreased significantly in Group 1 and 3 and did not change in Group 2. Stroke index increased significantly in both groups of patients with elevated control LVFP (Group 2 and 3) and remained unchanged in patients with normal left ventricular function (Group 1). Left ventricular stroke work index decreased in Group 1, increased in Group 2, and remained unchanged in Group 3. Right ventricular stroke work index decreased significantly in all groups. These findings suggest that judicious intraoperative administration of sodium nitroprusside improves left ventricular function in patients with acute or chronic elevation of LVFP and LV dysfunction associated with severe CAD. Furthermore, nitroprusside is an effective drug for control of intraoperative hypertensive episodes in such patients.

Adult↗
PubMed1975

Filling pressures of the heart and pulmonary circulation of the patient with coronary-artery disease after large intravenous doses of morphine.

Filling pressures of the heart and hemodynamic responses were studied before, during, and after administration of morphine, 2 mg/kg, intravenously (5 mg per minute) in eight patients with coronary-artery disease and normal ventricular contractility requiring myocardial revascularization. Left-heart filling pressure (LHFP) was estimated by measuring balloon-occluded pulmonary arterial pressure via a Swan-Ganz catheter, and right-heart filling pressure (RHFP) by right atrial pressure measurements. LHFP and RHFP were unchanged until 1.5 mg/kg morphine had been administered; after 2 mg/kg, LHFP had risen from a control level of 6.9 plus or minus 0.8 to 10.6 plus or minus 1.1 mm Hg (P less than .01) and RHFP from 2.9 plus or minus 0.4 to 4.9 plus or minus 0.8 mm Hg (P less than .05). Heart rate (P less than .02) and rate-pressure product (P less than .05), an indirect index of myocardial oxygen consumption, decreased throughout the study period. Systemic arterial pressure, cardiac index, and left ventricular stroke work decreased significantly only at the 0.5 mg/kg dose level, while systemic vascular resistance and stroke index remained unchanged. Mean pulmonary arterial pressure increased (P less than .05) after 1.5 mg/kg morphine, but pulmonary vascular resistance was unchanged. PaC02, pH, base excess, and hematocrit were constant throughout the study period. These data indicate that doses of morphine to 2 mg/kg, iv, are well tolerated by, and, presumably, decrease the myocardial oxygen consumption of, patients with coronary-artery disease. The hemodynamic response resembles that seen in man without hear or lung disease.

Blood Pressure↗
PubMed1975

Left ventricular performance and pulmonary circulation following addition of nitrous oxide to morphine during coronary-artery surgery.

The effects of nitrous oxide on ventricular performance and pulmonary circulation were studied in 12 patients with angiographically demonstrated coronary-artery disease and normal ventricular contractility who had received 2 mg/kg morphine intravenously. Seventeen studies were performed intraoperatively, five before and 12 after cardiopulmonary bypass and myocardial revascularization. Recordings were obtained during oxygen breathing and during nitrous oxide administration. Fifty per cent nitrous oxide significantly decreased mean arterial pressure (P less than 0.05), cardiac index (P less than 0.01), stroke index (P less than 0.01), left ventricular stroke work index (P less than 0.01), peak left ventricular dP/dt (P less than 0.05) and dP/dt/P (P less than 0.01), and heart rate-systolic arterial pressure product (P less than 0.01). Mean pulmonary arterial pressure (P less than 0.05), pulmonary artery occluded pressure (P less than 0.01), left ventricular end-diastolic pressure (P less than 0.01) and pulmonary vascular resistance (P less than 0.05) increased. Heart rate, right atrial pressure and systemic vascular resistance remained unchanged. When nitrous oxide was discontinued, all variables returned to control except mean pulmonary arterial pressure and pulmonary vascular resistance. Responses were similar before and after cardiopulmonary bypass and myocardial revascularization. These findings suggest that nitrous oxide depresses left ventricular performance when administered intraoperatively to patients who have received large doses of morphine for coronary-artery surgery. Nitrous oxide also increases pulmonary vascular resistance, possibly via alpha-adrenergic stimulation.

Anesthesia, Inhalation↗
PubMedDate not supplied

Systemic and pulmonary hemodynamic changes immediately following mitral valve replacement in man.

The immediate hemodynamic effects of mitral valve replacement were studied in patients with and without severe pulmonary arterial hypertension (systolic pressure greater than 50 mm Hg). In patients with severe pulmonary hypertension, mitral valve replacement resulted in significantly decreased pulmonary arterial pressure, pulmonary vascular resistance and pulmonary capillary wedge pressure. Cardiac index increased significantly while heart rate remained unchanged. These data support the hypothesis that a reflexly induced reversible component is often responsible for the disproportionate pulmonary hypertension encountered in patients with mitral valve disease. "Fixed" or irreversible pulmonary hypertension was not encountered in this series.

Adult↗