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Biomedical subjects

D G Lappas

Publications and source records attributed to D G Lappas.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1989

Quantitative relationships between plasma beta-endorphin immunoactivity and hemodynamic performance in preoperative cardiac surgical patients.

To quantitate the importance of cardiac dysfunction as a stimulus for plasma immunoactive beta-endorphin (iBE) secretion, we measured iBE and hemodynamic indices in 65 patients prior to anesthetic induction for coronary artery bypass grafting or valve replacement. Linear regression analysis for the group as a whole showed significant correlations between iBE and stroke index (SI), pulmonary artery wedge pressure (PCW), and right atrial pressure (RAP), but not mean arterial pressure (MAP). Two patient subgroups were identified (P less than 0.001 by F-test): those with low SI and high iBE, or those with high SI and low iBE (cutoffs at 40 ml/m2 and 35 pg/ml, respectively). Correlations between hemodynamics and iBE were always stronger within the low-SI than the high-SI subgroups. These correlations were greater for patients with coronary artery than with valvular heart disease. Cardiac output (CO) and cardiac index (CI) correlated with iBE in valve-replacement and coronary-grafting groups. These findings were not an artifact of impaired iBE clearance due to renal dysfunction. Our results quantitate the importance of hemodynamic dysfunction for iBE secretion, and indicate that this relationship is particularly strong when stroke index declines below 40 ml/m2.

Adult↗
PubMed1987

Myocardial circulatory and metabolic effects of isoflurane and sufentanil during coronary artery surgery.

The global and regional coronary hemodynamic and myocardial metabolic effects of isoflurane administered intraoperatively as an adjunct to sufentanil were studied in seven of nine patients who experienced increased systemic arterial pressure while undergoing elective coronary artery bypass grafting. All patients were premedicated and maintained on their preoperative medications (beta-blockers, nitrates, Ca++ entry blockers) up to and including the morning of surgery. Systemic and pulmonary hemodynamics and global (coronary sinus, CS) and regional (great cardiac vein, GCV) coronary blood flows were measured, and blood samples were obtained for systemic and myocardial metabolic parameters: after induction with 30 mcg/kg of sufentanil and 0.12 mg/kg vecuronium (FIO2 1.0), but prior to incision (control); 5 min after sternotomy; and during ventilation with isoflurane-oxygen. Heart rate, cardiac output, stroke volume, and GCV/CS flow ratio did not change throughout the study. Neither global nor regional myocardial lactate production was detected in any patient at any time, and the electrocardiogram (lead II, V5) remained unchanged. In response to sternotomy, seven of nine patients experienced an increase in mean systemic arterial pressure of 20% or more (27 +/- 3% from control values), due to an elevation in systemic vascular resistance (30 +/- 5%). Coronary sinus (CS) and great cardiac vein (GCV) flows, as well as CS and GCV lactate extractions, were unchanged 5 min after sternotomy. Both global and regional myocardial oxygen extraction increased, while coronary venous oxygen content decreased. Isoflurane was administered in a dose that restored systemic arterial pressure to baseline values (inspired concentration 0.75-1.0%).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Continuous monitoring of oxygen tension with a transcutaneous sensor during hypotensive anesthesia.

Transcutaneous oxygen tension (TCPO2) is a useful noninvasive technique for monitoring arterial oxygen tension under stable circulatory conditions. This study was undertaken to determine if TCPO2 is also reliable during sodium nitroprusside-induced hypotension under general anesthesia. Arterial blood gases and TCPO2 were measured prior to inducing hypotension (baseline), at 20-min intervals during hypotension, and when systemic arterial pressure had returned to within 10% of the control (pre-hypotension) value. With induced hypotension, PaO2 and TCPO2 decreased significantly (P less than 0.05), and were well correlated by linear regression (r greater than 0.85); however, regressions were strongly dependent on the individual patient. The mean regression line for all patients as a group was given by TCPO2 = 0.69 PaO2 + 20.7 mmHg (r = 0.93, P less than 0.01); significantly different regressions were obtained for each patient (P less than 0.0001). Comparing changes in TCPO2 versus those in PaO2 (relative change from baseline values) did not substantially reduce the variability among patients. It is concluded that TCPO2 reliably reflects changes in arterial oxygen tension during controlled hypotension under general anesthesia, but that a separate calibration of TCPO2 vs. PaO2, obtained prior to inducing hypotension, may be required for each individual patient.

Adult↗
PubMed1986

Interpretation of pulmonary artery wedge pressure and pullback blood gas determinations during positive end-expiratory pressure ventilation and after exclusion of the bronchial circulation in the dog.

Left atrial pressure (LAP) and pulmonary artery wedge pressure (PWP) were measured at different heights during graded increases in positive end-expiratory pressure (PEEP). Six healthy anesthetized dogs were placed in lateral decubitus positions with a balloon-tipped pulmonary artery catheter inserted in each lung. PWP in the gravitationally superior lung overestimated LAP at 15 and at 20 cm H2O PEEP (p less than 0.05). PWP in the dependent lung was virtually identical to LAP at all degrees of PEEP. Wedge blood could be aspirated through the distal lumen of the pulmonary artery catheters during balloon inflation at all degrees of PEEP except for 3 attempts. PCO2 in wedge blood in both the nondependent and dependent lungs at all degrees of PEEP was consistently lower than PCO2 in arterial blood (p less than 0.05). Wedge blood was arterialized, i.e., oxygen saturation greater than 95%, in all but 4 specimens. Surgical elimination of the bronchial artery supply to the lung in 3 dogs did not affect PWP or blood gas measurements. We conclude that in this animal model: (1) the tip of a pulmonary artery catheter must be below the level of the left atrium, Zone III location, to accurately reflect LAP at high degrees of PEEP; (2) arterialization of wedge blood samples does not guarantee that PWP reflects LAP; (3) bronchial artery blood supply does not affect PWP or wedge blood gas measurements, even at high degrees of PEEP.

Animals↗
PubMed1984

Propranolol prevents hemodynamic and humoral events after abrupt withdrawal of nitroprusside.

Hemodynamic and humoral events after intraoperative discontinuation of nitroprusside were studied in subjects without and with pretreatment with intravenous propranolol, 0.1 mg X kg-1. Nitroprusside-induced hypotension was associated with increases in heart rate, cardiac output, plasma renin activity (PRA), and catecholamine levels; these changes were prevented by propranolol. In subjects pretreated with propranolol, dose requirements of nitroprusside for hypotension of comparable degree and duration decreased 40%. On discontinuation of nitroprusside, mean systemic pressure rose to 100.2 mm Hg--a level higher than prehypotension and awake values--because of increased systemic vascular resistance. Hemodynamic events were associated with persistent elevations of PRA and catecholamine levels. These rebound changes were maximal 15 min after nitroprusside withdrawal and returned to control levels 30 to 60 min later. Pretreatment with propranolol completely prevented rebound hemodynamic events after nitroprusside. Persistent elevations of PRA and catecholamine levels after nitroprusside action subsided were responsible for the effects of withdrawal.

Adolescent↗
PubMed1982

Hypothermic ischemic arrest versus hypothermic potassium cardioplegia in human beings.

To determine if the addition of potassium enhances the myocardial protective effect of intracoronary perfusion hypothermia during aortic cross-clamping, 50 patients undergoing aortocoronary bypass grafting were studied in a randomized, prospective, double-blind fashion. Twenty-six patients received a cold crystalloid solution infused with a handheld syringe into the root of the cross-clamped aorta every 20 minutes, and 24 patients received the same solution but with 25 mEq/L of potassium chloride added, infused in a similar manner. Both groups were analyzed by mortality, rate of perioperative myocardial infarction (electrocardiographic changes, MB-CPK enzyme release, and preoperative and postoperative gated cardiac blood pool scans), intraoperative hemodynamic changes, intraoperative lactate determinations, postoperative arrhythmias, and requirement for pressor or intraaortic balloon pump support. One patient in the potassium cardioplegia group died (massive pulmonary embolism), and none in the hypothermic perfusion group died. Possible perioperative myocardial infarction was diagnosed by more than one marker in 4 of 26 patients in the hypothermic perfusion group and 5 of 24 patients in the potassium group (p = 0.61). There were no differences between the two groups in terms of hemodynamic changes, lactate production, postoperative arrhythmias, or the need for postoperative hemodynamic support. This study in human beings could not demonstrate a specific protective effect of potassium, beyond that afforded by myocardial perfusion hypothermia and wash-out. The data suggest that myocardial hypothermia, achieved through cold intracoronary arterial perfusion, may be the most important beneficial component of so-called cardioplegia for attaining effective intraoperative myocardial preservation in human beings.

Arrhythmias, Cardiac↗
PubMed1982

Acute oliguria after cardiopulmonary bypass: renal functional improvement with low-dose dopamine infusion.

Hemodynamic and renal function response to low-dose (100 and 200 micrograms/min) dopamine infusion was studied in 15 adult cardiac surgical patients who manifested combined oliguria and left ventricular dysfunction postoperatively. Patients were studied an average of 6.6 h after ICU admission, at normothermia and after 2 consecutive hourly urine output determinations of less than 0.5 ml/kg . h in the presence of a left atrial or pulmonary artery occlusion pressure over 12 mm Hg. Dopamine infusion at 100 micrograms/min produced improvement in creatinine, osmolar and free water clearances (70 +/- 10 to 115 +/- 13, 37 +/- 4 to 93 +/- 16 and --15 +/- 2 to --37 +/- 10 ml/min, respectively), and urinary sodium concentration (15 +/- 5 to 29 +/- 10 mEq/L). Urine flow improved overall from 22 +/- 2 to 54 +/- 9 ml/h; however, in 9 of 15 patients, flow was less than 0.5 ml/kg . h (33 +/- 5 to 50 +/- 6 ml/h). In each of these 9 patients, dopamine infusion at 20 micrograms/min further improved urine flow as well as measured renal function. Plasma renin activity measured in 9 of the 15 patients before and during the 100 micrograms/min dopamine infusion was decreased from 1.95 +/- 0.57 to 0.73 +/- 0.39 ng/ml . h. The hemodynamic effect of both dopamine doses was increased cardiac output coupled with decreased systemic (SVRI) and pulmonary vascular resistance index (PVRI). In these 15 patients, low-dose dopamine infusion produced significant improvement in renal function, with resolution of oliguria in every case, and with no deleterious hemodynamic effect.

Adult↗
PubMed1980

Preservation of normal gas exchange with hemodilution in patients with pulmonary hypertension.

The relationship between the plasma colloid osmotic pressure/pulmonary capillary wedge pressure difference (PCOP-PCWP) and the development of gas exchange abnormalities was examined prior to, during, and after cardiac operations in 13 patients with pulmonary hypertension owing to mitral and/or aortic valvular disease. Alveolar-arterial oxygen tension gradient [P(A-a)DO2] and pulmonary shunt fraction (Qs/Qt) were used as indices of gas exchange impairment owing to accumulated lung water. During the baseline period, PCOP-PCWP was -8.5 +/- 2.6 mm Hg; P(A-a)DO2, 352.5 +/- 30.1 mm Hg; and Qs/Qt, 17.0% +/- 1.5%. There were no significant correlations between PCOP-PCWP and P(A-a)DO2 or Qs/Qt at any time during the study. Thus PCOP-PCWP does not predict susceptibility to lung water accumulation reliably in patients with pulmonary hypertension, and other protective factors may contribute to unimpaired gas exchange, even in the setting of profound hemodilution and low PCOP.

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↗