Myocardial electrical impedance correlates with ischemic ECG ST-segment changes in humans.

Electrocardiogram (ECG) ST-segment changes are commonly used to diagnose myocardial ischemia. In this study we compared ST-segment changes with changes in myocardial electrical impedance (MEI)--an electrical parameter that also responses to ischemia--during off-pump coronary artery bypass graft (OPCABG) surgery of the left anterior descending coronary artery (LADa). We recorded MEI and ST-segment changes in eight patients during OPCABG surgery and compared the change in MEI that occurred when the LADa was occluded just prior to the beginning of the revascularization procedure with the ST-segment changes during the same period. Myocardial electrical impedance changes were directly and significantly correlated with ST-segment changes in our patient population. Our results indicate that MEI is equivalent to ST-segment changes as a measure of myocardial ischemia.

A randomized double-blinded multicenter comparison of remifentanil versus fentanyl when combined with isoflurane/propofol for early extubation in coronary artery bypass graft surgery.

UNLABELLED: We compared a fentanyl/isoflurane/propofol regimen with a remifentanil/isoflurane/propofol regimen for fast-track cardiac anesthesia in a prospective, randomized, double-blinded study on patients undergoing elective coronary artery bypass graft surgery. Anesthesia was induced with a 1-min infusion of 0.5 mg/kg propofol followed by 10-mg boluses of propofol every 30 s until loss of consciousness. After 0.2 mg/kg cisatracurium, a blinded continuous infusion of remifentanil at 1 microg. kg(-1). min(-1) or the equivalent volume rate of normal saline was then started. In addition, a blinded bolus syringe of 1 microg/kg remifentanil or 10 microg/kg fentanyl, respectively, was given over 3 min. Blinded remifentanil, 1 microg. kg(-1). min(-1) (or the equivalent volume rate of normal saline), together with 0.5% isoflurane, were used to maintain anesthesia. Significantly more patients (P < 0.01) in the fentanyl regimen experienced hypertension during skin incision and maximum sternal spread compared with patients in the remifentanil regimen. There were no differences between the groups in time until extubation, discharge from the surgical intensive care unit, ST segment and other electrocardiogram changes, catecholamine levels, or cardiac enzymes. The remifentanil-based anesthetic (consisting of a bolus followed by a continuous infusion) resulted in significantly less response to surgical stimulation and less need for anesthetic interventions compared with the fentanyl regimen (consisting of an initial bolus, and followed by subsequent boluses only to treat hemodynamic responses) with both drug regimens allowing early extubation. IMPLICATIONS: Both fentanyl and the newer opioid remifentanil, when each is combined with isoflurane and propofol, allowed for fast-track cardiac anesthesia. The remifentanil regimen used in this study resulted in significantly less hemodynamic response to surgical stimulation.

The efficacy and resource utilization of remifentanil and fentanyl in fast-track coronary artery bypass graft surgery: a prospective randomized, double-blinded controlled, multi-center trial.

UNLABELLED: We compared (a) the perioperative complications; (b) times to eligibility for, and actual time of the following: extubation, less intense monitoring, intensive care unit (ICU), and hospital discharge; and (c) resource utilization of nursing ratio for patients receiving either a typical fentanyl/isoflurane/propofol regimen or a remifentanil/isoflurane/propofol regimen for fast-track cardiac anesthesia in 304 adults by using a prospective randomized, double-blinded, double-dummy trial. There were no differences in demographic data, or perioperative mortality and morbidity between the two study groups. The mini-mental status examination at postoperative Days 1 to 3 were similar between the two groups. The eligible and actual times for extubation, less intense monitoring, ICU discharge, and hospital discharge were not significantly different. Further analyses revealed no differences in times for extubation and resource utilization after stratification by preoperative risk scores, age, and country. The nurse/patient ratio was similar between the remifentanil/isoflurane/propofol and fentanyl/isoflu-rane/propofol groups during the initial ICU phase and less intense monitoring phase. Increasing preoperative risk scores and older age (>70 yr) were associated with longer times until extubation (eligible), ICU discharge (eligible and actual), and hospital discharge (eligible and actual). Times until extubation (eligible and actual) and less intense monitoring (eligible) were significantly shorter in Canadian patients than United States' patients. However, there was no difference in hospital length of stay in Canadian and United States' patients. We conclude that both anesthesia techniques permit early and similar times until tracheal extubation, less intense monitoring, ICU and hospital discharge, and reduced resource utilization after coronary artery bypass graft surgery. IMPLICATIONS: An ultra-short opioid technique was compared with a standard fast-track small-dose opioid technique in coronary artery bypass graft patients in a prospective randomized, double-blinded controlled study. The postoperative recovery and resource utilization, including stratification of preoperative risk score, age, and country, were analyzed.

An evaluation of a new two-electrode myocardial electrical impedance monitor for detecting myocardial ischemia.

The objective of this study was to determine the efficacy of a two-electrode myocardial electrical impedance (MEI) monitor in reproducibly detecting induced myocardial ischemia by comparing MEI changes with hemodynamic changes, including sonomicrometric changes. With institutional approval, 80 dogs were anesthetized with sodium thiamylal, intubated, ventilated, and had venous, arterial, and pulmonary artery catheters placed. Medial sternotomy was performed to facilitate myocardial exposure and allow the left anterior descending coronary artery (LAD) to be isolated. Two pacing electrodes were attached to the myocardium to measure MEI with a monitor. Seventy dogs were randomly assigned to the 15, 30, 45, 60, or 120 min LAD occlusion group. Sonomicrometric transducers were attached to the myocardium of the ten remaining dogs and their LAD was occluded for 36 min. MEI increased immediately after LAD occlusion to a level significantly more (P < 0.05) than baseline and returned to the baseline level upon reperfusion. Twenty dogs developed ventricular fibrillation with no attempts at resuscitation. MEI changes paralleled the sonomicrometric changes expected with ischemia. No significant cardiovascular hemodynamic changes were found with less than 45 min of LAD occlusion. Sixty and 120 min LAD occlusion resulted in significant decreases in cardiac output. The results of these experiments demonstrate that the two-electrode MEI monitor reproducibly changes in response to myocardial ischemia.

Comparative effects of oral clonidine and intravenous esmolol in attenuating the hemodynamic response to epinephrine injection.

STUDY OBJECTIVE: To evaluate oral clonidine and intravenous esmolol in blunting hemodynamic changes associated with intranasal injection of an epinephrine-containing local anesthetic solution during general anesthesia. DESIGN: Prospective, randomized, double-blind, placebo-controlled study. SETTING: University Medical Center. PATIENTS: 61 consenting ASA physical status I and II outpatients undergoing endoscopic sinus and septoplasty surgery with general anesthesia. INTERVENTIONS: All patients were assigned to receive either a placebo (P) tablet or a similar-appearing tablet containing either clonidine 0.2 mg (C2) or 0.4 mg (C4) orally 1 hour prior to entering the operating room. Prior to the intranasal injection of epinephrine, patients were administered either saline, 0.03 ml.kg-1 followed by an infusion of 0.016 ml.kg-1.min-1, or esmolol (E) 300 micrograms.kg-1 followed by a continuous infusion of 160 micrograms.kg-1.min-1. MEASUREMENTS AND MAIN RESULTS: Arterial blood pressure and heart rate (HR) values were recorded preoperatively, immediately before induction of anesthesia, and at 1-minute intervals after induction of anesthesia until 15 minutes after injection of an epinephrine-containing solution. Level of sedation was assessed using a linear visual analog scale (VAS) prior to oral premedication, immediately before induction of anesthesia, and 30 minutes after anesthesia. There were no significant differences in sedation scores among the four treatment groups. HR following injection of epinephrine-containing solution was significantly less in the C2, C4, and E groups than the placebo group. Compared to P and E treatment groups, MAP values were significantly lower in the C4 treatment group. CONCLUSION: In this healthy, young, nonsmoking outpatient population, premedication with oral clonidine, 0.2 to 0.4 mg, was effective in blunting the acute hemodynamic changes associated with injection of an epinephrine-containing local anesthetic solution during endoscopic sinus or septoplasty surgery.

Correction of the copper transport defect of Menkes patient fibroblasts by expression of the Menkes and Wilson ATPases.

Menkes' disease is a fatal, X-linked, copper deficiency disorder that results from defective copper efflux from intestinal cells and inadequate copper delivery to other tissues, leading to deficiencies of critical copper-dependent enzymes. Wilson's disease is an autosomally inherited, copper toxicosis disorder resulting from defective biliary excretion of copper, which leads to copper accumulation in the liver. The ATP7A and ATP7B genes that are defective in patients with Menkes' and Wilson's diseases, respectively, encode transmembrane, P-type ATPase proteins (ATP7A or MNK and ATP7B or WND, respectively) that function to translocate copper across cellular membranes. In this study, the cDNAs derived from a normal human ATP7A gene and the murine ATP7B homologue, Atp7b, were separately transfected into an immortalized fibroblast cell line obtained from a Menkes' disease patient. Both MNK and WND expressed from plasmid constructs were able to correct the copper accumulation and copper retention phenotype of these cells. However, the two proteins responded differently to elevated extracellular copper levels. Although MNK showed copper-induced trafficking from the trans-Golgi network to the plasma membrane, in the same cell line the intracellular location of WND did not appear to be affected by elevated copper.

Desflurane and isoflurane produce similar alterations in systemic and pulmonary hemodynamics and arterial oxygenation in patients undergoing one-lung ventilation during thoracotomy.

UNLABELLED: We tested the hypothesis that desflurane (DES) and isoflurane (ISO) produce similar effects on systemic and pulmonary hemodynamics and arterial oxygenation before, during, and after one-lung ventilation (OLV) in patients undergoing thoracotomy. After obtaining informed consent, anesthesia was induced with sodium thiopental or thiamylal, fentanyl, and vecuronium in 61 ASA physical status II-IV patients. Patients were randomly assigned to receive either DES (n = 30) or ISO (n = 31) in 100% O2 in separate groups. Hemodynamic data (radial and pulmonary artery [PA] catheters) were recorded, and blood gas values were obtained before and after induction; at selected intervals before, during, and after OLV; and before emergence. DES significantly (P < 0.05) increased heart rate (HR) and decreased mean arterial pressure (MAP) and cardiac output (CO). PA pressures and pulmonary vascular resistance (PVR) increased; systemic vascular resistance (SVR) was unchanged. Increases in HR and CO and decreases in MAP and SVR occurred during OLV and DES. Reductions in PaO2 (411 +/- 88 to 271 +/- 131 mm Hg 5 min after beginning OLV; mean +/- SD) and content (CaO2) and increases in shunt fraction (Qs/Qt; 0.25 +/- 0.12 to 0.40 +/- 0.19 at 5 min after beginning OLV) were also observed. ISO increased HR and PA pressures but did not alter MAP, CO, and PVR, in contrast to the findings with DES. Reductions in MAP and SVR and increases in CO and PA pressures were observed during OLV in the presence of ISO. Similar to the findings during DES, decreases in PaO2 and CaO2 and increases in Qs/Qt occurred during OLV and ISO. We conclude that DES and ISO produce very similar alterations in systemic and pulmonary hemodynamics and arterial oxygenation in patients undergoing OLV during thoracotomy. IMPLICATIONS: Desflurane and isoflurane produce similar cardiovascular and pulmonary effects before, during, and after one-lung ventilation in patients undergoing lung surgery.

The effects of verapamil and diltiazem pretreatment on potassium release in dogs after the administration of succinylcholine.

UNLABELLED: Verapamil exacerbates the increase in serum potassium after a large-dose potassium infusion or after the IV administration of succinylcholine. We conducted a study in 12 canines conditioned for 30 days acting as their own controls. The canines had chronic tracheotomies and carotid loops performed 2 wk before the experiment. Control canines were given 1 mg/kg succinylcholine at Time 0. Blood samples were analyzed for potassium at 0, 1, 3, 5, 10, 15, 30, and 60 min. One week later, the dogs received 0.15 mg/kg of either verapamil or diltiazem, followed by a 5.6-microg x kg(-1) x min(-1) 10-min infusion of the same drug. The animals were then given a bolus dose of succinylcholine 1 mg/kg, and the blood potassium was analyzed as before. There was no significant difference in the potassium concentration before the succinylcholine injection (Time 0) between the study groups. The canines pretreated with verapamil had a significantly greater increase (24% +/- 8%) in potassium concentration than the control canines (14% +/- 6%) 15 min after succinylcholine administration. There was no difference between the potassium concentrations of the diltiazem-pretreated canines and the control group at any time point. Therefore, diltiazem pretreatment does not significantly influence potassium regulation after a succinylcholine injection, whereas verapamil pretreatment has measurable hyperkalemic effects. IMPLICATIONS: Succinylcholine is a drug that causes blood potassium to increase. Potassium influences heart rhythm. Verapamil and diltiazem are drugs used for angina heart pain. We used dogs to determine the effect of verapamil or diltiazem on the blood's potassium after an injection of succinylcholine and found that verapamil had the greatest effect.

A comparison of isoflurane versus fentanyl as primary anesthetics for mitral valve surgery.

We conducted a randomize study of fentanyl compared to isoflurane anesthesia in patients with pulmonary hypertension undergoing mitral valve surgery. Patients were premedicated and randomly assigned to one of two groups: 21 patients had anesthesia induced with thiopental and maintained with isoflurane; 23 patients had anesthesia induced with a fentanyl bolus and maintained with a fentanyl infusion. Adjustments of fentanyl infusion and isoflurane concentration, as well as fentanyl boluses and vasoactive/positive inotropic medication, were administered to maintain preoperative arterial blood pressure. Both groups exhibited similar demographics, similar duration of cardiopulmonary bypass (CPB) surgery, anesthesia, and time from entrance into the surgical intensive care unit (SICU) to endotracheal extubation. However, the time from entrance into the SICU to awake was significantly (P < 0.05) shorter in patients given isoflurane anesthesia. Hemodynamic variables were recorded at baseline and 12 surgical events and compared between and within groups. Significant changes from baseline were demonstrated in both groups upon institution and discontinuation of CPB. Patients receiving isoflurane anesthesia exhibited cardiovascular depression as compared to their baseline. There were no deaths in either patient group. Adequate hemodynamic profiles were achieved in both groups with comparable use of inotropic and vasoactive medication, with the exception of norepinephrine that was administered intraoperatively to significantly (P < 0.05) more patients in the isoflurane-based anesthesia group. Neither technique was associated with acute improvement of right heart performance or pulmonary hypertension, in large part because of morphologic changes of the pulmonary arterial bed, occurring with long-standing mitral valve disease. We conclude that isoflurane-based anesthesia is adequate for this type of surgery, although there is a higher anesthetic algorithm failure rate than with fentanyl-based anesthetic technique.

Effect of oral clonidine premedication on anesthetic requirement, hormonal response, hemodynamics, and recovery in coronary artery bypass graft surgery patients.

STUDY OBJECTIVE: To examine how premedication with clonidine affects opioid use, hemodynamic effects, hormonal responses, and recovery effects. DESIGN: Double blind, placebo-controlled study. SETTING: Operating room and surgical intensive care unit of a university medical center. PATIENTS: 54 patients undergoing elective coronary artery bypass graft (CABG) surgery. INTERVENTIONS: Patients received approximately 5 micrograms/kg of oral clonidine or a placebo together with 40 micrograms/kg lorazepam 90 minutes prior to titrated sufentanil induction of anesthesia. Thirty minutes prior to cardiopulmonary bypass, a second dose of either approximately 5 micrograms/kg clonidine or placebo was given as a slurry via a nasogastric tube. MEASUREMENTS AND MAIN RESULTS: Opioid use, hemodynamic effects, hormonal responses, and recovery effects were recorded. Values for ten hemodynamic variables were compiled on the evening prior to surgery, prior to induction, and during seven additional events and compared. Catecholamines and beta-endorphins were measured prior to induction, after intubation, and after sternotomy. The amount of sufentanil used for induction, maintenance, and total opioid were compared. The times to awakening and response to verbal commands were compared. The two groups exhibited similar patient demographics, cardiopulmonary bypass time, and duration of surgery. Patients receiving clonidine required significantly (p < 0.04) less sufentanil for induction (clonidine: 2.19 +/- 0.95 micrograms/kg vs. placebo: 2.93 +/- 1.07 micrograms/kg) and total amount of sufentanil (clonidine: 9.1 +/- 3.9 micrograms/kg vs. placebo: 11.7 +/- 4.6 micrograms/kg). Patients receiving clonidine required significantly (p < 0.01) less isoflurane (9.7 +/- 6.8 MAC min vs. 19.7 +/- 9.9 MAC min) to maintain heart rate (HR) and mean arterial pressure (MAP) to within 15% of baseline without significant differences in other vasoactive drugs. Catecholamine concentrations were significantly (p < 0.02) lower in patients receiving clonidine without any difference in beta-endorphin concentrations. Patients receiving clonidine had significantly (p < 0.02) lower HR, systolic arterial pressure, MAP, and systemic vascular resistance prior to induction than patients receiving placebo without differences in other hemodynamic variables. CONCLUSION: Clonidine decreases opioid use and lowers hormonal response while maintaining stable hemodynamics in patients undergoing CABG with sufentanil anesthesia.

A comparison of pentamorphone and fentanyl in balanced anaesthesia during general surgery.

The purpose of our randomized, double-blind study of 64 unpremedicated healthy patients undergoing surgical procedures with a duration of at least 60 min was to compare 0.75 micrograms.kg-1 and 1 microgram.kg-1 pentamorphone with 5 micrograms.kg-1 and 7.5 micrograms.kg-1 fentanyl to determine which dose of opioid would reduce the requirement for isoflurane supplementation needed to maintain haemodynamic stability. At 21 points during the procedure, the haemodynamic variables of heart rate and systolic, diastolic, and mean arterial pressures were recorded. The use of isoflurane was quantified; the number of patients requiring inhaled anaesthetic, concentration peaks, MAC minutes, and duration of isoflurane use were noted. The number of equal-volume supplemental opioid analgesic doses, postoperative analgesics, occurrence of postoperative nausea, emesis, and antiemetic doses were compared. The four groups exhibited similar patient demographics, total dose of muscle relaxants, types of surgical procedures, and duration of surgery or anaesthesia. Haemodynamic variables were stable with no difference among the four study groups. The patients given pentamorphone demonstrated both delayed requirement (P < 0.05) and shorter duration (P < 0.05) of isoflurane supplementation. Patients given either 5 micrograms.kg-1 or 7.5 micrograms.kg-1 fentanyl needed isoflurane supplementation within 12 +/- 16 min and 12 +/- 17 min from induction respectively; while patients given either 0.75 micrograms.kg-1 or 1 microgram.kg-1 pentamorphone did not require isoflurane supplementation for 37 +/- 10 min and 43 +/- 26 min respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative and postoperative effects of vancomycin administration in cardiac surgery patients: a prospective, double-blind, randomized trial.

OBJECTIVES: In response to an increased frequency of Staphylococcus epidermidis infections in postoperative cardiac surgery patients, antibiotic prophylaxis was changed to include both vancomycin and cefazolin pre- and intraoperatively. Subsequent to the addition of vancomycin prophylaxis, clinical impression and retrospective analysis supported a correlation between vancomycin administration and post-cardiopulmonary bypass norepinephrine use. DESIGN: A prospective, double-blind, randomized study. SETTING: Tertiary care center in a university hospital. PATIENTS: A total of 58 patients undergoing elective coronary artery bypass surgery under high-dose fentanyl anesthesia. INTERVENTIONS: Patients were randomized to receive cefazolin and either vancomycin or normal saline pre-, intra-, and postoperatively in a double-blinded protocol. MEASUREMENTS AND MAIN RESULTS: Hemodynamic profiles and doses of administered vasoactive agents were calculated and recorded for all patients for both intra- and postoperative time periods. Hypotension consistent with vasodilation was treated with a norepinephrine infusion. The rate and frequency of norepinephrine infusions were tabulated for both groups. Hemodynamic profiles that were obtained after the administration of the initial dose of vancomycin or normal saline and before the induction of general anesthesia and those profiles obtained after the induction of general anesthesia until the initiation of cardiopulmonary bypass showed no difference between groups and no evidence of vasodilation secondary to vancomycin administration. However, subsequent doses of vancomycin in the intra- and postoperative periods were associated with a significantly greater frequency of norepinephrine infusions to maintain normal hemodynamic indices. In the vancomycin group, 50% of patients received a norepinephrine infusion in the intra- and/or postoperative period as compared with 14% in the normal saline group (p < .01). Furthermore, the group of patients who received vancomycin and subsequently required a norepinephrine infusion had significantly lower mean systolic arterial pressure, mean arterial pressure, and systemic vascular resistance as compared with all other groups. There were no differences between groups in the use of vasopressors (other than norepinephrine) or fluid balance. CONCLUSIONS: The results show that a significantly greater number of patients who received vancomycin required a norepinephrine infusion and that, despite norepinephrine infusion therapy, systemic vascular resistance was not normalized in this group of patients. The study supports the conclusion that perioperative administration of vancomycin in cardiac surgery patients may result in hypotension requiring the use of a vasopressor in an attempt to normalize hemodynamic indices.

Defining the dose range for esmolol used in electroconvulsive therapy hemodynamic attenuation.

We evaluated the clinical effectiveness of esmolol, an ultra-short-acting, beta-adrenergic receptor blocking drug, to control the sinus tachycardia and increase in arterial blood pressure induced by electroconvulsive therapy (ECT). Each of 20 patients, ASA physical status I-III, participated in a double-blind, randomized Latin-Square study involving two matched-pair trials (placebo versus esmolol given as a 500-micrograms/kg bolus followed by either 300 micrograms.kg-1.min-1 [high dose], 200 micrograms.kg-1.min-1 [medium dose], or 100 micrograms.kg-1.min-1 [low dose] infusion of esmolol) during ECT. Each patient acted as his or her own control (total number of ECT procedures were 160). We administered a 1-min bolus of placebo (normal saline) or esmolol at the rate of 500 micrograms.kg-1.min-1 followed by either high-, medium-, or low-dose esmolol or placebo for an additional 3 min. We then induced anesthesia with methohexital (1 mg/kg) and succinylcholine (0.5 mg/kg) IV. Ninety seconds after the administration of succinylcholine, the electrical stimulus was applied to induce seizure. The infusion of placebo or esmolol was discontinued 3 min after the electrical stimulus. Significant decreases were found in mean heart rate from minute 3 until minute 7 and in the maximum heart rate. The mean of each patient's maximum heart rate after seizure changed from 147 +/- 18 bpm in placebo patients to 112 +/- 20 bpm in high-dose esmolol patients; to 121 +/- 23 bpm in medium-dose esmolol patients; and to 124 +/- 20 bpm in low-dose esmolol patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative course after sufentanil or fentanyl anesthesia for coronary artery surgery.

Postoperative hemodynamic effects were compared in 50 patients randomly selected to receive either sufentanil, 25 micrograms/kg, or fentanyl, 100 micrograms/kg, anesthesia for coronary artery bypass grafting. The two groups exhibited similar patient demographics; dose of premedicants and muscle relaxants; and use of inhalation agents. Values for 15 hemodynamic variables were recorded at baseline and at six postoperative times. The times to awakening, response to verbal commands, and extubation were also noted. Patients who received sufentanil had a more stable course, with higher cardiac outputs, lower systemic vascular resistances, and a lower incidence of hypertension. Postoperatively, the two groups had similar values for time to awakening, response to verbal commands, and extubation. Elimination half-lives differed significantly: 554 +/- 91 minutes (fentanyl) versus 277 +/- 60 minutes (sufentanil). Serum concentrations of both decreased linearly. The added advantages of postoperative hemodynamic stability could be important in the choice of anesthetic.

Esmolol reduces autonomic hypersensitivity and length of seizures induced by electroconvulsive therapy.

We evaluated the clinical effectiveness of esmolol, an ultra-short-acting beta 1-adrenergic receptor blocking drug, to control the sinus tachycardia and increase in arterial blood pressures induced by electroconvulsive therapy (ECT). Each of 20 patients, ASA physical status I-III, participated in a double-blind, randomized study, involving four match-pair trials (placebo versus esmolol) during ECT. Each patient acted as his or her own control (total number of ECT procedures, 160). We administered a 4-min infusion of either placebo or esmolol at the rate of 500 micrograms.kg-1.min-1. We then induced anesthesia with methohexital and succinylcholine. After administration of electrical stimulation for ECT, the rate of infusion decreased to 300 micrograms.kg-1.min-1 for three additional minutes and was then discontinued. Statistically significant reductions in mean heart rate from minute 2 until minute 15 and in maximum heart rate (the mean of each patient's maximum heart rate after seizure changed from 152 +/- 23 to 115 +/- 24 beats/min) occurred in patients given esmolol. During and immediately after infusion, arterial blood pressure also decreased. Finally, the length of seizures decreased, as manifested clinically from 48 +/- 18 to 39 +/- 14 s and on electroencephalogram from 86 +/- 41 to 67 +/- 28 s. We conclude that esmolol effectively controls the hyperdynamic response to ECT and reduces the length of seizures. The significance of the latter to the overall effectiveness of ECT is not known.

A comparison of enflurane with alfentanil anaesthesia for gynaecological surgery.

Forty patients undergoing gynaecological surgery were randomly assigned to receive either alfentanil and thiopentone for induction of anaesthesia, followed by alfentanil-N2O/O2 (60%/40%) for maintenance of anaesthesia, or low-dose fentanyl and thiopentone, followed by enflurane-N2O/O2 (60%/40%). More patients given enflurane developed a tachycardia (P less than 0.03) and 20% decreases in systolic and diastolic blood pressure. Times to recovery were significantly shorter after alfentanil than after enflurane. Plasma concentrations of alfentanil during induction suggested that haemodynamic and catecholamine responses were either less than, or did not differ from, baseline levels when the plasma concentration of the drug exceeded 150 ng ml-1. At extubation and the beginning of spontaneous breathing, the plasma concentration was 278 +/- 129 ng ml-1. Values for pharmacokinetic parameters of alfentanil were as follows: clearance, 5.2 +/- 2.0 ml kg-1 min-1; volume of distribution, 0.63 +/- 0.20 1 kg-1; and elimination half-life, 96.9 +/- 52.5 min. Two patients who had extended surgery had significantly lower plasma clearance of alfentanil and increased half-life. The authors conclude that the alfentanil technique was preferable to maintenance with enflurane.