Biomedical subjects
Publications and source records attributed to J G Reves.
The effect of regional cerebral blood flow during coronary bypass surgery on performance on the Mini-Mental State Examination was studied in 14 patients. No association between lowered regional cerebral blood flow and cognitive scores was found.
Explore the source record for details and available documents.
We studied the cardiovascular effects of esmolol, a newly synthesized beta-adrenocepter antagonist, in anesthetized humans. Forty patients (four groups of 10 each) with ischemic heart disease and normal ventricular function were anesthetized with diazepam, pancuronium, and N2O in O2. Esmolol was given by continuous infusion in cumulative doses of 1100 micrograms/kg (group 1), 2000 micrograms/kg (group 2), and 2700 micrograms/kg (group 3); a control group received no esmolol. Infusion of esmolol was begun 3 min prior to and ended 4 min after tracheal intubation. All three doses of esmolol significantly (P less than 0.001) attenuated the heart rate responses to intubation. Rate-pressure products were significantly (P less than 0.001) lower in esmolol-treated patients than in controls after intubation, but ST-segment changes compatible with ischemia occurred in one patient in each group. Increases in heart rate were associated with significant increases in plasma norepinephrine levels (r = 0.45, P = 0.02) in the control group, but not in esmolol-treated patients, a demonstration that esmolol antagonizes the beta-adrenergic effects of norepinephrine. The effect of esmolol on heart rate was absent 5 min after cessation of infusion, and plasma levels of esmolol were undetectable in 26 of 30 treated patients 15 min after the termination of esmolol infusion. Esmolol has a rapid onset and short duration of effect. It can be used safely during anesthesia in patients with normal ventricular function to attenuate cardiac response to sympathetic stimulation.
Explore the source record for details and available documents.
Midazolam is an imidazobenzodiazepine with unique properties when compared with other benzodiazepines. It is water soluble in its acid formulation but is highly lipid soluble in vivo. Midazolam also has a relatively rapid onset of action and high metabolic clearance when compared with other benzodiazepines. The drug produces reliable hypnosis, amnesia, and antianxiety effects when administered orally, intramuscularly, or intravenously. There are many uses for midazolam in the perioperative period including premedication, anesthesia induction and maintenance, and sedation for diagnostic and therapeutic procedures. Midazolam is preferable to diazepam in many clinical situations because of its rapid, nonpainful induction and lack of venous irritation. Compared with thiopental, midazolam is not as rapid acting nor predictable in hypnotic effect. It will not replace thiopental as an induction agent. Advantages of midazolam over thiopental are those of the more versatile pharmacologic properties of a benzodiazepine compared with a barbiturate such as amnestic and anxiolytic properties. Midazolam should be a useful addition to the formulary.
Explore the source record for details and available documents.
This study determines whether reperfusion of the heart with elevated blood levels of epinephrine (E) and norepinephrine (NE) during cardiac surgery produces deleterious effects. The study was conducted in 60 patients undergoing coronary artery bypass surgery. Arterial catecholamine values increased significantly (p less than 0.05), from prebypass control levels of 152 +/- 29 and 327 +/- 30 pg/ml of E and NE, respectively, to 415 +/- 78 and 554 +/- 49 pg/ml, at initiation of perfusion of the heart after the aortic cross-clamp was removed. Serial measurement of arterial (A) and coronary sinus (CS) E, NE, potassium, lactate, PO2 and CK-MB revealed that during 10 minutes of reperfusion the heart extracted E (positive A-CS difference, p less than 0.05), but that the NE A-CS difference was 0. The CS effluent contained significantly (p less than 0.05) higher concentrations of potassium, lactate and CK-MB during reperfusion than before aortic occlusion. There was no significant correlation of arterial E and NE, CS E and NE or A-CS differences in E and NE with myocardial release of lactate, potassium or CK-MB. There was a weak association (r = 0.4, p less than 0.01) between coronary sinus CK-MB and aortic occlusion time. Maximal arterial E and NE values did not correlate with 10-hour postoperative (maximal) CK-MB values. These results indicate that reperfusion of the postarrested ischemic heart with high levels of endogenously released catecholamines does not worsen ischemia or contribute significantly to myocardial damage.
Over the past six years there has been a 15-fold increase in the number of patients requiring reoperation coronary artery bypass grafting (RCABG) surgery at the University of Alabama in Birmingham. To determine the perioperative risk, a retrospective chart survey of one calendar year's (1981) experience was made comparing the 58 RCABG patients with 59 cohorts undergoing primary operation. All patients were anaesthetized with diazepam, fentanyl and halothane or enflurane anaesthesia. Preoperative evaluation revealed by history that the incidence of unstable angina and digoxin use were greater (p = 0.05) in the RCABG patients. Cardiac catheterization revealed a higher incidence (26 vs 89 percent) of left main coronary disease in controls and similar indices of left ventricular function (wall abnormalities, ejection fraction and LVEDP). Operating and bypass times were longer (p less than 0.01) for RCABG patients and there was a trend for greater (p = 0.08) use of dopamine in the RCABG patients. CK-MB release was significantly (p less than 0.05) greater in RCABG patients. Serious postoperative complications (CK-MB greater than or equal to 15 IU/L, low cardiac output, and death) were significantly (p = 0.02) greater in the RCABG group. It is concluded that RCABG patients represent a greater risk of complications and that new strategies for improving myocardial protection need to be developed to reduce the risk.
In this study we examined the relationship of regional cerebral blood flow (CBF) to mean arterial pressure, systemic blood flow, partial pressure of arterial carbon dioxide (PaCO2), nasopharyngeal temperature, and hemoglobin during hypothermic nonpulsatile cardiopulmonary bypass (CPB). Regional CBF was determined by clearance of xenon 133 in 67 patients undergoing coronary bypass grafting procedures. There was a significant decrease in regional CBF (55% decrease) during CPB, with nasopharyngeal temperature and PaCO2 being the only two significant factors (p less than 0.05). In a subgroup of 10 patients, variation of pump flow between 1.0 and 2.0 L/min/m2 did not significantly affect regional CBF. We conclude that cerebral autoregulation is retained during hypothermic CPB. Under the usual conditions of CPB, variations in flow and pressure are not associated with important physiological or detrimental clinical affects.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
To determine whether adding blood to a cardioplegic solution affects myocardial preservation, a randomized prospective study was carried out in 60 patients undergoing coronary revascularization to compare the effects of crystalloid potassium cardioplegics (group C) and potassium cardioplegic solutions to which blood has been added (group B) on markers of myocardial metabolism (lactate, inorganic phosphate, base deficit release, glucose and lactate uptake, oxygen extraction), myocardial damage (creatine kinase [CK]-MB levels), and cardiac performance (cardiac index and left atrial pressure). The solution with added blood had a significantly (p less than .05) greater oxygen content, a lower pH, and higher concentrations of potassium, calcium, sodium, and glucose. In group B patients there was a suggestion (p less than .06) of greater uptake of oxygen during the beginning of the initial cardioplegic infusion. During reperfusion there was no evidence of differential release of the metabolites of anaerobiosis and myocardial oxygen extraction and glucose and lactate uptake were similarly depressed in both groups. Likewise, CK-MB release after bypass was the same in both groups. Prompt, adequate functional recovery of cardiac index and left atrial pressure was observed in both groups. It was concluded that although there may be more oxygen available from the blood-containing solution during early infusion, there is no evidence that under the conditions of this investigation adding blood to cardioplegic solution improves myocardial preservation.
The effects of fentanyl, nitrous oxide, and their combination on myocardial contractility were investigated in the papillary muscle preparation perfused by a donor dog. With a conscious donor, fentanyl infused directly into the arterial blood perfusing the papillary muscle produced a dose-related depression of developed tension. However, blood concentrations of fentanyl required to obtain the depression were in the range of 30-120 micrograms/ml. The ED50 for fentanyl for suppression of papillary muscle contractility was 89 +/- 9 micrograms/ml. When the donor dog was given nitrous oxide (N2O,80% and O2,20%), the developed tension of the papillary muscle decreased 25 +/- 5%. Fentanyl administered during nitrous oxide anesthesia caused a decrease in developed tension that was not significantly different from that obtained without N2O anesthesia (18 +/- 4% vs 13 +/- 4% for 30 micrograms/ml, and 61 +/- 5% vs 58 +/- 4% for 100 micrograms/ml). The results suggest that fentanyl produces a direct negative inotropic effect only in concentrations that are 2-3 orders of magnitude higher than its blood concentrations in fentanyl-induced anesthesia. When fentanyl and nitrous oxide are used together their interaction is not significantly different from additive.
Hearts were excised from 30 male Sprague-Dawley rats and perfused in a modified Langendorff system to examine the interactions of fentanyl and diazepam on myocardial contractility as measured by left ventricular dP/dtmax. Various concentrations of fentanyl and diazepam were added to the nonrecirculating 37 degrees C perfusate to determine ED25 and ED50 for depression of dP/dtmax. Combinations of fentanyl and diazepam at a fixed negative inotropic potency ratio of 1:1 were used to determine the ED25 and ED50 of this combination. Isobolographic analyses performed at ED25 and ED50 revealed that the negative inotropic interaction of fentanyl and diazepam is purely additive. It is unlikely that a supraadditive negative inotropic effect can explain the supraadditive hemodynamic depression reported in humans when diazepam and fentanyl are combined; perhaps systemic vascular effects of this drug combination account for the clinical drug interactions.
Explore the source record for details and available documents.
Fifteen patients with chronic renal failure (CRF) were given midazolam 0.2 mg/kg iv over 15 s. All but one lost consciousness in a time ranging from 22-100 s (mean +/- SD was 55 +/- 26 s) after drug administration. Patients regained consciousness from 6-105 min (mean 53 +/- 32) after drug administration. The calculated mean plasma level of midazolam at arousal was 81 +/- 47 ng/ml. Pharmacokinetics parameters were determined from midazolam plasma levels measured in 16 consecutive venous blood samples. The pharmacokinetic parameters in CRF patients were compared with those of healthy volunteers matched for age, sex, and body size with the CRF patients. Protein binding was determined by equilibrium dialysis. CRF patients had a significantly higher (P less than 0.005) plasma-free drug fraction (6.5% +/- 0.7) compared with the control patients (3.9% +/- 0.1). Total (bound plus unbound) kinetics differed in the two groups: volume of distribution 3.8 +/- .3 1/kg in CRF patients versus 2.2 +/- .2 1/kg in controls (P less than 0.001), and clearance 11.4 +/- 1.6 ml X min-1 X kg-1 in CRF patients versus 6.7 +/- 0.9 ml X min-1 X kg-1 in controls (P less than 0.02). When kinetic parameters were corrected for protein binding, CRF patients unbound volume of distribution (63.5 +/- 6.8 1/kg) and free drug clearance (189 +/- 29 ml X min-1 X kg-1) were not different from the control group's volume of distribution (55.6 +/- 5.7 1/kg) and free drug clearance (176 +/- 24 ml X min-1 X kg-1).(ABSTRACT TRUNCATED AT 250 WORDS)
The interaction of nifedipine and halothane was examined in 19 dogs. Nifedipine (10 micrograms/kg) was infused over 2 min in animals anesthetized with either 1% or 2% halothane. The predominant hemodynamic effect of nifedipine was a short-lived reduction (less than 15 min) in mean blood pressure accompanied by a decrease in systemic vascular resistance. During 2% halothane anesthesia hypotension mean blood pressure was greater (P less than 0.05) 15 and 30 min after nifedipine than during 1% halothane. Nifedipine hypotension was initially (2 min) associated with a 23% increase in heart rate and a 22% increase in cardiac output in animals anesthetized with 1% halothane, but during 2% halothane there was no change in heart rate. Changes in dP/dt and contractile force were minimal after nifedipine in both groups. The clinical implications of this study are that nifedipine given during halothane anesthesia may be associated with significant hypotension and that higher concentrations of halothane attenuate the reflex compensatory increase in heart rate. Doses of halothane and nifedipine must be chosen cautiously when the drugs are used together.