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Biomedical subjects

D G Lappas

Publications and source records attributed to D G Lappas.

At least 19 recordsLinked to original sources
PubMed1992

Perioperative evaluation of a new mixed venous oxygen saturation catheter in cardiac surgical patients.

Fiberoptic pulmonary artery flotation catheters have gained clinical acceptance for continuous monitoring of mixed venous oxygen saturation (SvO2), especially in the management of hemodynamically unstable patients. Therefore, the performance of the oximetry system used is extremely important. The accuracy and stability of a new two-wavelength oximetry pulmonary artery catheter and SAT-2 oximeter were assessed in adult patients during and following cardiac surgery. After in vitro calibration of the system, the catheter was inserted through the right internal jugular vein and positioned in the pulmonary artery prior to induction of anesthesia. During the study period, the system was updated for hemoglobin changes of 1.8 g/dL or more. In vivo SvO2 values obtained by the oximetry catheter were compared with those determined with a reference oximeter from simultaneously drawn mixed venous blood specimens at different intervals. A total of 604 paired data points from 52 patients were analyzed, 572 (94.7%) of which were within the 95% confidence interval. Overall bias was -1.7% +/- 3.5% (SD). The results suggest that over the time course of the study, in vivo SvO2 values obtained with the two-wavelength catheter and the SAT-2 oximeter closely approximated SvO2 measured with a reference oximeter from mixed venous blood samples (r = 0.917; SEE 3.5%) in cardiac surgical patients in whom marked physiological changes occur.

Adult↗
PubMed1991

Successful surgical treatment of atrial fibrillation. Review and clinical update.

Atrial fibrillation is the most common of all sustained cardiac arrhythmias, yet it has no effective medical or surgical therapy. During the past decade, multipoint computerized electrophysiological mapping systems were used to map both experimental and human atrial fibrillation. On the basis of these studies, a new surgical procedure was developed for atrial fibrillation. Between September 25, 1987, and July 1, 1991, this procedure was applied in 22 patients with paroxysmal atrial flutter (n = 2), paroxysmal atrial fibrillation (n = 11), or chronic atrial fibrillation (n = 9) of 2 to 21 years' duration. All patients were refractory to all antiarrhythmic medications, and each patient failed to receive the desired therapeutic benefits of an average of five drugs administered preoperatively. There were no operative deaths and all perioperative morbidity resolved. All 22 patients have been successfully treated for atrial fibrillation with surgery alone. Three patients developed one late isolated episode of atrial flutter at 5, 6, and 15 months postoperatively, and each of these patient's symptoms is now controlled by a single antiarrhythmic drug. Preservation of atrial transport function has been documented in all patients postoperatively, and all have experienced marked clinical improvement.

Adult↗
PubMed1991

Operations for atrial fibrillation.

Atrial fibrillation is the most common of all sustained cardiac arrhythmias, yet it has no effective medical or surgical therapy. During the past decade, multipoint computerized electrophysiological mapping systems were used to map both experimental and human atrial fibrillation. On the basis of these studies, a new surgical procedure was developed for atrial fibrillation. Between September 25, 1987, and May 1, 1991, this procedure was applied in 22 patients with either paroxysmal atrial flutter (n = 2), paroxysmal atrial fibrillation (n = 11), or chronic atrial fibrillation (n = 9) of 2 to 21 years' duration. All patients were refractory to all antiarrhythmic medications and each patient failed an average of 5.2 drugs preoperatively. There were no operative deaths and all perioperative morbidity resolved. All 22 patients have been cured of atrial fibrillation with surgery alone. One late isolated episode of atrial flutter occurred in a patient who is now receiving encainide. Preservation of atrial transport function has been documented in all of the patients postoperatively and all have experienced marked clinical improvement.

Adult↗
PubMed1991

Regional and global myocardial circulatory and metabolic effects of isoflurane and halothane in patients with steal-prone coronary anatomy.

The use of isoflurane in patients with coronary artery disease remains controversial because of the possibility of "coronary steal". In this study, the effects of isoflurane and halothane on global and regional myocardial blood flow and metabolism were compared, and the relationship between steal-induced myocardial ischemia and the administered volatile anesthetic was investigated in 40 patients with steal-prone coronary anatomy undergoing elective coronary artery bypass operations. The patients were randomly assigned to receive either isoflurane or halothane (0.5 MAC inspired concentration) immediately after induction with fentanyl (50 micrograms/kg). Hemodynamic measurements and blood samples were obtained at preinduction, postintubation, preincision, poststernotomy, at 60 min after beginning isoflurane or halothane, and precannulation (a total of 238 study events). Throughout the study, heart rate was kept constant by atrial pacing at approximately postintubation values while arterial pressure was maintained within 10% of postintubation values with fluid administration or phenylephrine infusion. Overall, systemic hemodynamic changes observed during the study were similar in the two groups. Myocardial ischemic episodes were defined as a new electrocardiographic ST-segment shift of greater than or equal to 0.1 mV, new echocardiographic regional wall motion abnormalities (RWMA) and/or myocardial lactate production (MLP). A total of 18 new ischemic episodes were detected in 15 patients (7 episodes during isoflurane in 7 patients and 11 during halothane in 8 patients). Ten (56%) episodes were related to acute hemodynamic abnormalities, whereas 8 (44%) were random and unrelated to changes. Seven episodes were detected by echocardiography (38%), 6 by MLP (33%) and 1 by ECG (6%) only, whereas concomitant echocardiographic abnormalities and MLP were observed during 2 episodes (11%), echocardiographic and ECG during 1 (6%), and ECG and MLP during 1 other (6%). Ratios of regional to global coronary venous flow, coronary vascular resistance, myocardial oxygen content, and lactate extraction, along with hemodynamic data obtained during these episodes, do not support coronary steal for the development of myocardial ischemia. We conclude that in patients with steal-prone coronary anatomy anesthetized with fentanyl, neither isoflurane nor halothane administered at concentrations used in the current study is likely to cause myocardial ischemia by the coronary steal mechanism.

Adult↗
PubMed1979

Diazepam prevents some adverse effects of succinylcholine.

Neuromuscular, circulatory, and adverse effects of intravenous succinylcholine (SCh), mg/kg, were compared in 3 groups of 40 patients each. Group I served as control; group II received diazepam, 0.05 mg/kg, 5 min before SCh; and group III was given d-tubocurarine (d-Tc), 0.05 mg/kg, for pretreatment. Diazepam pretreatment prevented muscle fasciculations, increases in serum potassium (K+) and creatinine phosphokinase (CPK) levels, increased heart rate and arterial pressure, and postoperative myalgia associated with SCh administration. The neuromuscular blocking action of SCh was not affected. Pretreatment with d-Tc did not abolish increases in serum K+ and CPK levels, was associated with a higher incidence of postoperative myalgia, and decreased the onset and magnitude of SCh-induced muscle paralysis. Our data demonstrate that diazepam, a predominant centrally acting muscle relaxant, is more effective than d-Tc in preventing the adverse effects of SCh, a peripherally acting muscle relaxant.

Adolescent↗
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↗
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↗