Does choice of the anesthetic influence renal function during infrarenal aortic surgery?

Reconstructive infrarenal aortic surgery is associated with impairment of renal function owing to vasoconstriction during and after aortic cross-clamping. To assess the influence of anesthetic technique on renal hemodynamics during aortic surgery, 34 patients received one of four anesthetics: isoflurane (n = 10), halothane (n = 9), droperidol (n = 8), and flunitrazepam (n = 7). Supplemental anesthesia consisted of midazolam, fentanyl, nitrous oxide in oxygen (50%), and pancuronium. Before aortic cross-clamping, effective renal plasma flow (ERPF) (131iodohippuran clearance) and glomerular filtration rate (GFR) (99technetium-DTPA clearance) were low in the halothane and flunitrazepam groups (118.4 +/- 25.6 and 170 +/- 35 mL/min for ERPF; 19.7 +/- 5.2 and 26.9 +/- 5.8 mL/min for GFR, respectively) and better preserved in the isoflurane group (253.4 +/- 51.5 and 44.9 +/- 8.4 mL/min, respectively; P less than 0.05 between isoflurane and halothane groups) or in the droperidol group as regards GFR (75.4 +/- 9.4 mL/min, P less than 0.05). During clamping, both renal variables were not markedly affected in any group except in the droperidol group in whom GFR significantly decreased from preclamp value. The GFR was then significantly higher in the isoflurane group (49.5 +/- 9.2 mL/min) than in the halothane and flunitrazepam groups (14.8 +/- 3.7 and 26.5 +/- 10.1 mL/min, respectively; P less than 0.05). After aortic declamping, ERPF and GFR increased markedly in the halothane group, and there was no significant difference between the groups. These results suggest that renal hemodynamics are less altered with droperidol-fentanyl anesthesia during abdominal surgery but not during aortic cross-clamping.(ABSTRACT TRUNCATED AT 250 WORDS)     

Renal function and hemodynamics during prolonged isoflurane-induced hypotension in humans

The effect of isoflurane-induced hypotension on glomerular function and renal blood flow was investigated in 20 human subjects. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by inulin and para-aminohippurate (PAH) clearance, respectively. Anesthesia was maintained with fentanyl, nitrous oxide, oxygen, and isoflurane. Hypotension was induced for 236.9 +/- 15.1 min by increasing the isoflurane inspired concentration to maintain a mean arterial pressure of 59.8 +/- 0.4 mmHg. GFR and ERPF decreased with the induction of anesthesia but not significantly more during hypotension. Postoperatively, ERPF returned to preoperative values, whereas GFR was higher than preoperative values. Renal vascular resistance increased during anesthesia but decreased when hypotension was induced, allowing the maintenance of renal blood flow. We conclude that renal compensatory mechanisms are preserved during isoflurane-induced hypotension and that renal function and hemodynamics quickly return to normal when normotension is resumed.     

Halothane and Xanthine Oxidase Increase Hepatocellular Enzyme Release and Circulating Lactate after Ischemia-Reperfusion in Rabbits

Background: Multiple-organ injury often occurs after aortic occlusion-reperfusion. Oxidants derived from xanthine oxidase have been implicated as a source of injury after aortic occlusion-reperfusion. Halogenated anesthetics modify oxidant-mediated injury. The current study determined if halothane modifies hepatocellular enzyme release (e.g., alanine aminotransferase) and circulating lactate after aortic occlusion-reperfusion.

Methods: Rabbits were randomly assigned to one of four groups that underwent 40 min of thoracic aortic occlusion and 2 h of reperfusion: Two groups were given either halothane or fentanyl plus droperidol anesthesia and two groups were given either anesthetic and sodium tungstate (xanthine oxidase inactivator). Each of the four groups was then matched with a similarly treated group that did not undergo aortic occlusion.

Results: Halothane anesthesia was associated with significantly (P < 0.05) increased release of alanine aminotransferase (34 +/- 9 U/l at baseline and 539 +/- 370 U/l at 120 min of reperfusion; mean +/- SD) and increased plasma lactate concentrations (2.8 +/- 2.0 mM at baseline and 12.1 +/- 9.7 mM at 120 min of reperfusion) after aortic occlusion-reperfusion compared with fentanyl plus droperidol anesthesia (alanine aminotransferase, 33 +/- 12 U/l and 148 +/- 109 U/l; lactate, 3.4 +/- 2.0 mM and 3.8 +/- 1.2 mM at baseline and 120 min of reperfusion, respectively). Inactivation of xanthine oxidase significantly decreased the release of hepatocellular enzymes (P < 0.05) and decreased circulating lactate in animals anesthetized with halothane after aortic occlusion-reperfusion.     

The effect of infrarenal aortic reconstruction on glomerular filtration rate and effective renal plasma flow.

Compromised patients with aortic disease are vulnerable to various complications from aortic reconstruction. These complications are related to changes in systemic haemodynamics during aortic cross-clamping, which leads to cardiac stress and alteration in regional blood flow to different organs. One of the most important postoperative complications is renal failure which is associated with a high mortality rate. Circulatory alterations within the kidney must play a role in the pathogenesis of renal dysfunction that may follow infrarenal aortic cross-clamping and reconstruction. To study the effects of abdominal aortic reconstruction on renal function and perfusion, we measured prospectively the glomerular filtration rate (GFR, n = 59), effective renal plasma flow (ERPF, n = 38) and left ventricular ejection fraction (LVEF, n = 38) in patients undergoing elective infrarenal aortic reconstruction. Radionuclide techniques were used. The three parameters were measured at three time points: preoperatively, postoperatively and 6 months after surgery. The LVEF was measured in order to reflect the patient's cardiac status and pre-renal perfusion. We also measured the three parameters in two control groups of patients: a group of patients undergoing major colonic surgery and a group of patients with arterial disease under conservative management. Six months after surgery the GFR had decreased in 67% of aortic reconstruction patients. Overall GFR in the aortic reconstruction group decreased by a mean of 9 ml min-1 (p = 0.007). This was associated with a decrease in the ERPF in 48.5% of patients. The mean decrease in ERPF in the aortic reconstruction group was 74 ml min-1 (p = 0.05). The LVEF was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of cardiopulmonary bypass and cardioplegia on regional and global cardiac actions of halothane in dogs

Cardiopulmonary bypass (CPB) with aortic cross-clamping represents a controlled period of global cardiac ischemia. We hypothesized that CPB (asanguineous prime), with aortic cross-clamping and repeated cardioplegia, alters myocardial function, which would be manifested as an exaggerated myocardial depression caused by halothane after CPB. In nine dogs anesthetized with fentanyl and midazolam, halothane dose-response curves (0.0%-2.0%) were compared before and after CPB. A reduced mean arterial blood pressure (46.4 +/- 3.7 vs 85.8 +/- 5.9 mm Hg), associated with a marked hemodilution (hematocrit, 19% +/- 1% vs 41% +/- 2%), was observed after CPB. Cardiac output and systolic shortening were not significantly different after versus before CPB during fentanyl-midazolam anesthesia. Normalized to fentanyl-midazolam hemodynamics, halothane dose-response curves before and after CPB were identical for all variables except cardiac output, where halothane caused a slight but statistically significantly more pronounced decrease after CPB compared with before CPB. The effect of halothane on left ventricular function, therefore, is relatively unaffected by CPB with cardioplegia.     

Narcotics decrease heart rate during inhalational anesthesia

We determined the heart rate (HR) response to enflurane, halothane, and isoflurane and the effects of narcotics on this response in 81 healthy patients scheduled for elective surgery. Patients were randomly assigned to one of six treatment groups: one of the three anesthetics (approximately 0.9 MAC) in 60% nitrous oxide, and either 0.15 mg/kg of intramuscular morphine 30-60 min before induction or 1 microgram/kg of IV fentanyl 10 min after skin incision. All patients received diazepam, 10 mg orally, 60-90 min before anesthesia, a rapid sequence intravenous induction, and mechanically controlled ventilation. During inhalational anesthesia and the first 10 min of surgery, no significant change in HR occurred in any group (compared to the preinduction HR), although patients given morphine premedication tended to have a decreased HR and those not given morphine premedication tended to have an increased HR. These trends partially account for significant differences that emerged between groups after induction of anesthesia. Patients given morphine premedication and halothane had lower HR (64 +/- 3 SEM) than patients given isoflurane (80 +/- 3) or enflurane (84 +/- 3) and no morphine premedication. Patients anesthetized with enflurane and morphine premedication had lower HR (71 +/- 3) than patients given enflurane without morphine premedication. Administration of fentanyl 10 min after incision (these patients had received no morphine) significantly decreased HR in the presence of any of the vapors. We conclude that inhalational anesthetics used in the clinical setting we employed do not significantly increase heart rate, and that prior administration of morphine or concurrent administration of fentanyl may significantly decrease HR.     

Body mass index is associated with altered renal hemodynamics in non-obese healthy subjects

BACKGROUND: Weight excess is associated with increased renal risk. Data in overt obesity suggest a role for altered renal hemodynamics. Whether body mass index (BMI) is also relevant to renal function in non-obese subjects is unknown. METHODS: We studied the relation between BMI and renal hemodynamics in 102 healthy, non-obese (BMI <30 kg/m2) subjects [59 males, 43 females, mean age 39 (18-69) years] in a post-hoc analysis of subjects evaluated as prospective kidney donors or as healthy volunteers in renal hemodynamic studies. RESULTS: Mean (+/-SD) BMI was 24.0 +/- 2.8 kg/m2, mean arterial pressure (MAP) 93 +/- 11 mm Hg, glomerular filtration rate (GFR, iothalamate clearance) 111 +/- 19 mL/min/1.73 m2, effective renal plasma flow (ERPF, hippuran clearance) 458 +/- 108 mL/min/1.73 m2, FF (GFR/ERPF) 0.25 +/- 0.04. On univariate analysis, BMI correlated negatively with ERPF/1.73 m2 body surface area (BSA) (r=-0.46; P < 0.001), GFR/1.73 m2 BSA (r=-0.24, P= 0.013) and positively with FF (r= 0.45, P < 0.001), and age (r= 0.47, P < 0.001). On multivariate analysis both BMI and age were independent predictors of ERPF/1.73 m2 BSA (negative) and FF (positive, all P < 0.05). Age was the only predictor of GFR/1.73 m2 BSA (negative). Analyzed for renal function indexed for height (h), BMI correlated negatively with ERPF/h (r=-0.274, P= 0.005), but not with GFR/h (r= 0.13, P= 0.899). On multivariate analysis both BMI (positive) and age (negative) were independent predictors for GFR/h (both P < 0.001). Age was the only predictor for ERPF/h (negative). Predictors for FF (BMI and age, both positive) were by definition unaltered. CONCLUSION: The impact of BMI on renal function is not limited to overt obesity, as in subjects with BMI <30 kg/m2 a higher BMI is associated with higher FF, that is, a higher GFR relative to ERPF. This suggests an altered afferent/efferent balance and higher glomerular pressure (i.e., a potentially unfavorable renal hemodynamic profile) that may confer enhanced renal susceptibility when other factors, such as hypertension or diabetes are superimposed.     

Comparative study in pediatric inhalation anesthesia. Clinical characteristics and anesthetic complications with halothane and isoflurane]

OBJECTIVES. Comparative study of clinical characteristics and complications during induction, maintenance, and recovery in pediatric inhalational anesthesia between two commonly used fluoride agents (halothane and isoflurane). MATERIAL AND METHODS. We studied 66 children aged 1 month to 13 years undergoing general anesthesia for short lasting surgery who were divided into two groups of 33 patients each one: Isoflurane group and halothane group. Induction and maintenance anesthesia was performed with the corresponding inhalant agent. Parameters measured were duration of unconsciousness, time elapsed for intubation and recovery, heart rate, arterial blood pressure, and incidence of complications. RESULTS. Children anesthetized with isoflurane showed a shorter period of unconsciousness (1.55 +/- 0.11 min) than those anesthetized with halothane (1.91 +/- 0.12 min); whereas that the time required for intubation was significantly more prolonged (8.94 +/- 0.51 and 6.57 +/- 0.32 min, respectively). The incidence of complications was higher in the isoflurane group, mainly expressed as laryngeal spasm during the induction period. Both groups of patients showed a similar hemodynamic behaviour, although diastolic arterial pressure during maintenance anesthesia was significantly lower with isoflurane. Anesthesia recovery was faster and more predictable with isoflurane than with halothane. CONCLUSIONS. Anesthetic agent isoflurane is less appropriate than halothane for induction in pediatric anesthesia due to a high incidence of complications, specially laryngeal spasm.     

Treatment of proximal aortic hypertension after thoracic aortic cross-clamping in dogs. Phlebotomy versus sodium nitroprusside/isoflurane.

Thoracic aortic cross-clamping causes proximal aortic hypertension. Theoretically, the method used to treat hypertension can influence spinal cord perfusion pressure and neurologic outcome. Phlebotomy was compared to sodium nitroprusside/isoflurane in terms of ability to treat increased proximal mean aortic pressure (MAPp) after thoracic aortic cross-clamping in dogs. Dogs were assigned randomly to one of three groups depending on the method used to treat hypertension after cross clamping: 1) phlebotomy (n = 10); 2) sodium nitroprusside/isoflurane (n = 11); and 3) control (no treatment) (n = 8). In each dog, anesthesia was maintained with isoflurane in oxygen, 1.4% end-tidal. The thoracic aorta was occluded 2.5 cm distal to the left subclavian artery for 50 min and then was released. Hemodynamics, cerebrospinal fluid pressure (CSFP), and regional blood flows by the radioactive microsphere technique, were measured at 1) baseline; 2) 2 min after aortic cross-clamping; 3) after treatment of proximal aortic hypertension; 4) 5 min after aortic unclamping; and 5) 30 min after resuscitation. At 24 h, a neurologic assessment was performed. Thoracic aortic cross-clamping increased MAPp, decreased distal MAP (MAPd), and reduced lumbar spinal cord perfusion pressure (SCPPl), [SCPPl = MAPd - CSFP], in all three groups. Control of increased MAPp necessitated removal of 36 +/- 9 ml/kg of blood in the phlebotomy group. In the sodium nitroprusside/isoflurane group, sodium nitroprusside (16 micrograms.kg-1.min-1) was infused and end-tidal isoflurane concentration increased to 2.5 +/- 0.7%, restoring MAPp to baseline level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anesthesia for creation of a forearm fistula in patients with endstage renal failure

The effects of local infiltration anesthesia, brachial plexus blockade, isoflurane, or halothane anesthesia on blood flow through the brachial artery and through a newly created forearm arteriovenous fistula (AVF) were compared in 36 patients with endstage renal failure. Brachial artery blood flow was measured at two different times, before anesthesia and during anesthesia but before surgery, using a pulsed Doppler flowmeter. AVF flows were calculated from brachial, radial, and ulnar blood flows at the end of surgery, 2 h after surgery, and 3 and 10 days after the procedure. Mean arterial pressure was lower in patients receiving isoflurane or halothane than in those receiving local anesthesia or brachial plexus blockade (BPB). There was a significant increase in brachial artery blood flow following BPB (43.7 +/- 18.7 to 186.9 +/- 98.2 ml.min-1) during isoflurane anesthesia (46.2 +/- 15.9 to 153.1 +/- 80.5 ml.min-1) and during halothane anesthesia (49.9 +/- 24.1 to 97.6 +/- 62.1 ml.min-1). During anesthesia, the difference in brachial artery blood flow between patients in the BPB and halothane groups was significant. Local anesthesia failed to increase brachial artery blood flow (44.0 +/- 12.7 to 45.6 +/- 11.3 ml.min-1). In the immediate postoperative period, the AVF blood flow was lower in patients in the halothane group than in the other groups, but this difference was only significant when compared with BPB group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Significance of the renal functional reserve in reflux nephropathy: an evaluation according to the degree of glomerular damage

OBJECTIVE: In the treatment of progressive reflux nephropathy (RN), the therapeutic benefit and prognosis of the renal function in RN patients appears to be influenced by the degree of renal functional reserve. We designed this study to determine the presence and characteristics of the renal functional reserve in RN patients. MATERIALS AND METHODS: In the 35 RN patients with renal scars (19 males; mean age 16.1 years), an exogenous renal clearance test was performed to measure the glomerular filtration rate (GFR) and the effective renal plasma flow (ERPF). In the second half of this test, the renal functional reserve was estimated by measuring the GFR and ERPF during low-dose dopamine infusion. These measurements were then compared with the glomerular size, which had been previously determined by a renal biopsy. RESULTS: Among the patients with a normal glomerular size (-2SD to +2SD), the GFR markedly increased after low-dose dopamine infusion (from 112.15 +/- 52.51 to 182.07 +/- 69.95 mL/min, p < 0.0001), whereas an increase in ERPF was not significant. Among the patients with an enlarged glomerular size (+2SD to +4SD), the GFR and ERPF increased significantly over the baseline values (from 54.60 +/- 32.90 to 114.00 +/- 65.48 mL/min, p = 0.0076; from 281.01 +/- 152.54 to 622.43 +/- 392.73 mL/min, p = 0.0155, respectively). Among the patients with an extremely enlarged glomerular size (>+4SD), both the GFR and ERPF remained almost completely unchanged. CONCLUSION: The renal functional reserve was present even among progressive RN patients with a glomerular size ranging between +2SD and +4SD.     

Halothane,isoflurane, and fentanyl increase the minimally effective defibrillation threshold of an implantable cardioverter defibrillator: first report in humans

Placing an implantable cardioverter defibrillator (ICD) involves the induction of ventricular fibrillation, whereupon the minimally effective defibrillation energy threshold (DFT) is determined. We evaluated the effects of 0.7% halothane, 1% isoflurane, or 1.5 micro g/kg of IV fentanyl during N(2)O/oxygen-based general anesthesia (GA) or those of subcutaneous 1.5% lidocaine plus IV 0.35 mg/kg of propofol on the DFT during ICD implantation in humans (n = 20 per group). Thirty minutes after the first set of DFT measurements under such conditions, the inhaled anesthetics were withdrawn, and all three GA groups received fentanyl 1 microg/kg IV (second set). A third set was taken 30 min later, before the GA patients awakened and when only N(2)O/oxygen was delivered for GA. The lidocaine plus propofol patients were given the same IV propofol bolus 1 min before each fibrillation/defibrillation trial and at the same time points as the three GA groups. The first DFTs were 16.1 +/- 2.2 J (halothane), 17.7 +/- 2.7 J (isoflurane), 16.4 +/- 2.9 J (fentanyl), and 12.9 +/- 3.8 J (lidocaine plus propofol) (P = 0.01). The second set of DFTs were significantly lower than the first sets for the halothane (P = 0.01) and isoflurane (P = 0.02), but not the fentanyl or lidocaine plus propofol, regimens. The third DFTs were significantly (P < 0.01) lower than the first ones for the three GA groups, but not for the lidocaine plus propofol patients. Thus, halothane, isoflurane, and fentanyl increased DFT values during ICD implantation in humans, whereas lidocaine plus intermittent small-dose IV propofol minimized these thresholds. IMPLICATIONS: Halothane, isoflurane, and IV fentanyl added to N(2)O/oxygen-based general anesthesia similarly increase minimal defibrillation threshold energy requirements (DFT) during cardioverter defibrillator implantation in humans. Subcutaneous lidocaine plus intermittent small-dose IV propofol minimizes DFT compared with these general anesthetics while providing equal patient satisfaction.     

Captopril acutely lowers albuminuria in normotensive patients with diabetic nephropathy.

Angiotensin-converting enzyme (ACE) inhibitors decrease albuminuria in patients with diabetic nephropathy. To study the change in albuminuria in relation to changes in systemic and renal hemodynamics, nine normotensive patients with type 1 (insulin-dependent) diabetes mellitus and persistent proteinuria were given a single oral dose of 25 mg of the ACE inhibitor captopril. Blood pressure, glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and albumin excretion rate (AER) were measured in two periods of 40 minutes before and in four periods of 40 minutes after administration of captopril. A constant water diuresis was maintained. Blood pressure did not decrease significantly (130/79 +/- 4/3 v 124/74 +/- 4/3 mm Hg; mean +/- SEM), median AER decreased from 403 (interquartile range [IQR], 812) micrograms/min to 333 (707) micrograms/min (P < 0.01). GFR did not change (123 +/- 13 v 117 +/- 14 mL/min), but ERPF increased significantly from 609 +/- 56 to 714 +/- 55 mL/min (P < 0.01). Consequently, the filtration fraction (FF; quotient of GFR and ERPF) decreased from 0.20 +/- 0.014 to 0.17 +/- 0.014 (P < 0.01). A strong correlation was found between the decrease of AER and the decrease of FF (rs = 0.75; P < 0.02). No correlation was found between the decrease in AER and changes in GFR or blood pressure. In the normotensive patient with diabetic nephropathy, captopril causes an acute reduction of AER, which is probably mediated by a lowering of the intraglomerular pressure.     

A comparison of fentanyl and sufentanil in patients undergoing coronary artery bypass graft surgery

OBJECTIVE: To compare fentanyl and sufentanil, administered in equipotent concentrations by target-controlled infusion, as components of a balanced anesthetic in patients undergoing coronary artery bypass graft (CABG) surgery. DESIGN: A prospective, randomized, double-blind trial. SETTING: A university hospital. PARTICIPANTS: Twenty-one patients undergoing nonemergent, primary CABG surgery. INTERVENTIONS: Patients received fentanyl (group F, n = 10) or sufentanil (group S, n = 11) by target-controlled infusion throughout the pre-cardiopulmonary bypass (CPB) period. To ensure equipotency, the target effect-site concentrations employed (fentanyl, 8.1 ng/mL, and sufentanil, 0.68 ng/mL) were equal to the IC50 for electroencephalographic effect. Isoflurane was administered as needed to maintain pre-CPB hemodynamics near preoperative baseline values. MEASUREMENTS AND MAIN RESULTS: Hemodynamics and end-tidal isoflurane concentration were measured every 15 to 30 seconds. Serum opioid concentrations were measured 5 times between induction and CPB. Opioid cost was based on the number of ampules opened to provide the administered dose. The 2 groups were similar demographically. The pre-CPB serum opioid concentrations were constant and averaged fentanyl, 5.8 +/- 1.9 ng/mL, and sufentanil, 0.59 +/- 0.13 ng/mL. Pre-CPB hemodynamics were stable and similar in both groups. Pre-CPB end-tidal isoflurane requirements did not differ between groups and averaged 0.46 +/- 0.21% in group F and 0.56 +/- 0.24% in group S. The duration of post-operative endotracheal intubation was 9.1 +/- 5.0 hours in group F and 8.0 +/- 3.2 hours in group S (p = NS). The cost per patient of fentanyl (Canadian $6.12 +/- 1.04) was less than that of sufentanil (Canadian $17.47 +/- 4.65). CONCLUSIONS: When administered in a constant 10:1 concentration ratio, fentanyl and sufentanil do not differ in their ability to facilitate pre-CPB hemodynamic control. Although both opioids were relatively inexpensive, the acquisition cost of fentanyl was less than sufentanil. A recommendation regarding the opioid of choice for routine use in patients undergoing CABG surgery awaits more rigorous studies of recovery and cost after equipotent doses of fentanyl and sufentanil. When combined with isoflurane, effect-site opioid concentrations near the IC50 for electroencephalographic effect provide excellent pre-CPB hemodynamic control in patients undergoing CABG surgery.     

Plasma lidocaine concentrations during epidural blockade with isoflurane or halothane anesthesia.

Because isoflurane maintains hepatic blood flow at higher flows than halothane, we proposed that the elimination of lidocaine would be different between these two volatile anesthetics. The plasma lidocaine concentrations were determined in 14 female patients undergoing epidural blockade plus isoflurane anesthesia and compared with those obtained during halothane anesthesia for lower abdominal surgery. General anesthesia was maintained with isoflurane (0.46% +/- 0.04% [mean +/- SE] inspired, n = 7) or halothane (0.48% +/- 0.05% inspired, n = 7) and 67% nitrous oxide in oxygen. All patients received 2% lidocaine solution, 10 mL as a bolus dose and continuous administration at a rate of 10 mL/h, through the epidural catheter. The plasma lidocaine concentrations over 180 min after the epidural injection in patients receiving isoflurane were similar to those in patients receiving halothane. The results suggest that low inspired concentrations of isoflurane do not reduce plasma lidocaine concentrations in patients during epidural blockade, compared with halothane.     

Cerebral blood flow and metabolism in patients undergoing anesthesia for carotid endarterectomy. A comparison of isoflurane, halothane, and fentanyl

The effects of isoflurane, halothane, and fentanyl on cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) during anesthesia prior to carotid endarterectomy were compared using the intravenous method of 133-Xenon CBF determination. Patients, mean (+/- SE) age 68 +/- 2, received either isoflurane (N = 16), 0.75% in O2 and N2O, 50:50; halothane (N = 11), 0.5% in O2 and N2O, 50:50; or fentanyl (N = 10), 5-6 micrograms/kg bolus and then 1-2 micrograms.kg-1.h-1 infusion in addition to O2 and N2O, 40:60. Measurements were made immediately before carotid occlusion. Mean (+/- SE) CBF (ml.100 g-1.min-1) was 23.9 +/- 2.1 for isoflurane, 33.8 +/- 4.8 for halothane, and 19.3 +/- 2.4 for fentanyl. CMRO2 (ml.100 g-1.min-1) was available from 22 patients and was 1.51 +/- 0.28 for isoflurane (N = 7), 1.45 +/- 0.24 for halothane (N = 6), and 1.49 +/- 0.21 for fentanyl (N = 9). Although CBF was greater during halothane than during isoflurane or fentanyl anesthesia (p less than 0.05), there were no demonstrable differences in CMRO2 among the 3 agents. We conclude that choice of anesthetic agent for cerebrovascular surgery with comparable anesthetic regimens should not be made on the basis of "metabolic suppression." During relatively light levels of anesthesia, vasoactive properties of anesthetics are more important than cerebral metabolic depression with respect to effects on the cerebral circulation.     

Dose-response relation and time course of action of pipecuronium bromide in humans anesthetized with nitrous oxide and isoflurane, halothane, or droperidol and fentanyl

The dose-response of pipecuronium bromide, the time course of its neuromuscular blocking effects, and the reversibility of the residual block by neostigmine and edrophonium have been investigated in patients undergoing various types of anesthesia. The estimated doses of pipecuronium required for 95% depression of the twitch height were 44.6, 46.9, and 48.7 micrograms.kg-1 during anesthesia with nitrous oxide (65%) and isoflurane (group 1), halothane (group 2), or droperidol/fentanyl (group 3), respectively. The potentiating effects of the volatile anesthetics were reflected by the significant prolongation of the duration of both initial (50.0 +/- 4.3, 36.0 +/- 3.3, and 29.0 +/- 2.0 minutes) and maintenance doses (56.0 +/- 2.5, 49.5 +/- 3.3, and 41.2 +/- 1.6 minutes) of pipecuronium during anesthesia with nitrous oxide and isoflurane, halothane, or droperidol/fentanyl, respectively. Both edrophonium chloride (0.5 mg.kg-1) and neostigmine methylsulphate (40 micrograms.kg-1) promptly reversed the residual block induced by pipecuronium. No side effects attributable to pipecuronium were seen in this study.     

Plasma and urinary catecholamines as related to renal function in man

To assess the relationship between renal plasma flow (ERPF) or glomerular filtration rate (GFR) and the levels of norepinephrine (NE) or epinephrine (E) in plasma or urine in the presence of progressive degrees of non-oliguric renal functional impairment, these variables were assessed simultaneously in 18 normal subjects, 72 with parenchymal kidney disease and 14 with essential hypertension. ERPF and GFR were lower (P less than 0.01 to 0.001) in the groups with renal disease (mean +/- SD, 340 +/- 230 and 68 +/- 43 ml/min/1.73 m2, respectively) or essential hypertension (434 +/- 101 and 97 +/- 25 ml/min/1.73 m2) than normal subjects (597 +/- 133 and 118 +/- 14 ml/min/1.73 m2). Plasma and urinary NE and E did not differ significantly among groups and were unrelated with ERPF or GFR (range 4 to 160 ml/min/1.73 m2), except for reduced (P less than 0.001) urinary NE and E excretion in the presence of a GFR less than 20 ml/min. Subgroups with renal disease and a normal (N = 39) or high blood pressure (N = 33) also were comparable in their plasma and urinary NE and E, while ERPF and GFR tended to be lower in hypertensive patients. It is concluded that a chronic reduction in excretory kidney function may have no relevant impact on circulating levels of NE and E per se, although their urinary excretion falls distinctly at the stage of advanced renal failure. These aspects deserve consideration when pathogenetic or diagnostic studies of catecholamines are performed in normotensive or hypertensive patients with impaired kidney function.     

Isoflurane causes only minimal increases in coronary blood flow independent of oxygen demand

Studies on the coronary circulation during halothane or isoflurane anesthesia are conflicting. Also, little attention has been paid to the time course of the effect of these agents on the coronary circulation. Therefore, we investigated the direct and temporal effects of halothane and isoflurane on coronary hemodynamics in chronically instrumented dogs, in the presence and absence of autonomic nervous system blockade. On different days anesthesia was induced via inhalation with 5% halothane or isoflurane in 100% oxygen. After tracheal intubation, anesthesia was maintained at 1.0 MAC for 30 min. Hemodynamics were recorded continuously. Myocardial oxygen consumption was estimated from the pressure-work index. A total of 36 experiments (four sets of experiments) were completed using nine chronically instrumented dogs. Induction of anesthesia with halothane caused a significant (P less than 0.05) increase in coronary blood flow (from 40 +/- 6 to 68 +/- 11 ml/min), which reached a peak at 1.4 +/- 0.3 min. These changes were secondary to increases in heart rate, arterial pressure, and pressure-work index (10.2 +/- 1.4 to 15.9 +/- 0.8 ml O2.min-1.100g-1). With autonomic nervous reflexes eliminated, halothane caused no change in coronary blood flow. Inhalation of isoflurane caused a greater (P less than 0.05) increase in coronary blood flow (from 39 +/- 6 to 85 +/- 14 ml/min) than did halothane; flow reached a peak at 1.8 +/- 0.6 min. With autonomic reflexes eliminated, isoflurane continued to produce an increase (P less than 0.05) in coronary blood flow (from 39 +/- 4 to 53 +/- 5 ml/min), which reached a peak at 2.1 +/- 0.4 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemodynamic alterations and regional myocardial blood flow during supraceliac aortic occlusion in dogs with a critical coronary stenosis

The hemodynamic consequences and myocardial blood flow alterations associated with cross-clamping of the thoracic aorta were studied during pentobarbital (control), halothane (1 MAC), and isoflurane (1 MAC) anesthesia in dogs with a critical stenosis of the left circumflex coronary artery. Aortic clamping at the level of the diaphragm resulted in significant and equivalent increases in mean aortic pressure and left atrial pressure during the control clamp, halothane clamp, and isoflurane clamp periods. Likewise, aortic clamping resulted in a significant and equivalent decrease in cardiac output during control-clamp, halothane clamp, and isoflurane clamp. Myocardial contractility as assessed by dP/dt was depressed during halothane and isoflurane anesthesia when compared with control, but no further change in contractility was associated with aortic clamping. No significant alterations in regional or transmural myocardial blood flow were found with halothane or isoflurane anesthesia, or with aortic clamping during halothane or isoflurane anesthesia. It is concluded that there are significant hemodynamic consequences associated with aortic clamping, that neither halothane nor isoflurane anesthesia alters these consequences when compared with pentobarbital anesthesia alone, and that the deterioration in myocardial function observed during aortic clamping with halothane and isoflurane anesthesia cannot be attributed to any maldistribution of myocardial blood flow.