Propofol does not affect the canine cardiac conduction system under autonomic blockade

PURPOSE: To determine the effects of propofol on the cardiac conduction system in dogs with pharmacological autonomic blockade. METHODS: In eight mongrel dogs receiving 6 mg.kg-1.hr-1 propofol and vecuronium under pharmacological autonomic blockade with atropine and propranolol the infusion rates of propofol were increased from 6, (baseline), to 12, 18 and 24 mg.kg-1.hr-1 at 60-min intervals. An electrophysiological study assessed sinus rate, sinus node recovery time, corrected sinus node recovery time, intraatrial conduction time, AV nodal effective refractory period, Wenckebach cycle length and AV conduction times. Electrocardiographical variables and arterial pressures were also measured. All measurements were repeated at 30 min after the beginning of each infusion of propofol. RESULTS: Propofol did not produce direct effects on the electrophysiological or electrocardiographical variables at any infusion rates. Heart rates did not change at higher infusion rates in the presence of decreases in arterial pressures. CONCLUSION: Propofol did not affect the cardiac conduction system in the presence of autonomic blockade. Thus, the direct cardiac effects of propofol do not play a causative role in the genesis of propofol-associated bradyarrhythmias.     

Pentobarbital Plasma Concentrations and Cardiac Electrophysiology During Prolonged Pentobarbital Infusion Anaesthesia in the Dog

There is need for a prolonged stable level of anaesthesia, and we therefore investigated the cardiac electrophysiological effects of continuous pentobarbital infusion after initial pentobarbital injection to induce anaesthesia in dogs. Plasma concentrations of pentobarbital were measured by gas-liquid chromatography. Heart rate, atrial, atrioventricular (AV) nodal and His-Purkinje conduction times were measured by His bundle electrography, and atrial, AV nodal and ventricular refractoriness by programmed electrical stimulation. Over a 5-h observation period, continuous infusion of pentobarbital 3.5 mg · kg^-1 h^-1 after an initial pentobarbital injection of 25 mg · kg^-1 intravenously gave stable mean plasma concentrations of 140-135 μmol · l^-1. The cardiac electrophysiological variables studied did not change significantly during this period. We conclude that a stable experimental model for cardiac electrophysiological studies can be obtained for several hours by-continuous pentobarbital infusion.     

Does epidural sufentanil provide effective analgesia per-and postoperatively for abdominal aortic surgery?

To assess the efficacy of epidural sufentanil in providing per-and postoperative analgesia, 40 patients undergoing elective abdominal aortic surgery received either 50 μg sufentanil in 10 ml normal saline solution (n=20, ES group) or 10 ml normal saline (n=20, control group) via a thoracic epidural catheter. The study solution was given (double-blind and at random) after the patients had been anaesthetized with i.v. midazolam, sufentanil and vecuronium. Anaesthesia was maintained with 60% nitrous oxide in oxygen and halothane at a 1% inspiratory concentration. When patients showed signs of inadequate analgesia, supplementary doses of 25 μg sufentanil were given i.v. The number of patients requiring additional i.v. sufentanil differed significantly between the two groups: 5 out of 20 patients in the ES group vs 13 out of 20 patients in the control group required additional sufentanil (P<0.05). The mean dose administered i.v. did not differ significantly between the two groups: 105±109.5 μg vs 138.5±126.9 μg (mean±SD) in 5 and 13 patients, respectively. No cardiovascular changes were observed after the epidural bolus dose.
Postoperative analgesia, consisting of a continuous epidural infusion of 50 μg sufentanil in 50 ml bupivacaine 0.125% at a rate of 6–10 ml/h after a bolus dose of 10 ml of this solution, was adequate in the majority of patients, as determined by VAS-scores assessed during the epidural treatment (4.3±1.5 days).     

Sufentanil transfer in the human placenta during in vitro perfusion

Purpose

Sufentanil, a lipophilic opioid, is used to provide analgesia for labour and Caesarean section, but may cause neonatal depression. Factors affecting placental transfer of sufentanil were investigated using human placentas.

Study design

Transfer and uptake of sufentanil by the human placenta were studied using a single pass (open)in vitro perfusion model. The effects of change in sufentanil concentration (1–100 ng· ml^?1) and change in fetal pH (range 7.4–6.8) on placental transfer were studied. Placental metabolism of sufentanil and the effects of maternal protein content (fresh human plasma, albumin 4%, Media 199) on placental transfer were also investigated utilizing a closed (recirculated)in vitro perfusion system.

Results

Sufentanil transfer was 2% at five minutes and plateaued at 12% by 45 min. The clearance index (Cl =sufentanil clearance/antipyrine clearance) was 0.56 ± 0.2 for maternal to fetal (MTF) and 0.44 ± 0.2 in the fetal to maternal (FTM) directions (P=NS). The Cl was 0.5 ± 0.2 for 1 ng· ml^?1 and 0.61 ± 0.3 for 100 ng· ml^?1 sufentanil concentration (P=N.S.). The placenta contained 7.1 ± 2 and 9.8 ± 3 ng· g^?1 sufentanil following MTF and FTM perfusions for 90 min at 1 ng· ml^?1. The placenta did not metabolize sufentanil. After one hour MTF washout, placental sufentanil content was 2.3 ±.5 ng· g^?1 with 0.08 ng· ml^?1 sufentanil in the umbilical vein. Maternal plasma decreased MTF Cl from 0.41 ± 0.1 for albumin and 0.4 ± 0.1 for Media 199 to 0.17 ±.06 for plasma (P < 0.05). Decreasing fetal pH increased MTF Cl from 0.57 ±.13 at pH 7.4 to 1.6 ±.4 at pH 6.8 (P < 0.05).

Conclusion

Sufentanil crossed the placenta by passive diffusion and accumulated in placental tissue, which acted as a drug depot, slowing the initial transfer. Placental transfer was decreased by maternal plasma proteins, but not by albumin. Fetal acidosis increased placental transfer. Due to its low initial umbilical vein concentration, sufentanil may be the opioid of choice when delivery is imminent (< 45 min).     

The haemodynamic effects of rocuronium and vecuronium are different under balanced anaesthesia

Background: Rocuronium has been reported to have minimal haemodynamic effects. However, this conclusion has been drawn primarily from investigations conducted under narcotic-based anaesthesia. This study was designed to evaluate the cardiovascular effects of rocuronium under isoflurane/N20/fentanyl anaesthesia and to compare rocuronium's haemodynamic effects to those of vecuronium and pancuronium.
Methods: Anaesthesia was induced with fentanyl 2 μg/kg, thiopentone 4 mg/kg, and suxamethonium 0.5 mg/kg in 75 ASA I or II patients. After tracheal intubation, anaesthesia was maintained with isoflurane 0.5% and N₂0 50% in oxygen. Five min after intubation (baseline), patients randomly received either vecuronium 100 μg/kg, rocuronium 600 μg/kg, rocuronium 900 μg/kg, rocuronium 1200 μg/kg, or pancuronium 140 μg/kg. One min after administration of muscle relaxant, mean arterial pressure (MAP) and heart rate (HR) were recorded and were subsequently measured at 1-min intervals for the next 4 min.
Results: HR decreased significantly ( P <0.05) at all times compared to baseline in patients receiving vecuronium. HR significantly ( P < 0.05) increased in those receiving rocuronium 1200 μg/kg or pancuronium. Patients who received vecuronium had a sigruficant ( P < 0.05) decrease in MAP at all times compared to baseline. Comparing results between groups, patients who received rocuronium or pancuronium had significantly ( P < 0.05) higher MAP compared to those administered vecuronium.
Conclusion: The haemodynamic effects of rocuronium and vecuronium are different under balanced anaesthesia. Rocuronium may attenuate the fall in MAP that often occurs under balanced anaesthesia without surgical stimulation.     

Electrophysiologic effects of bupivacaine in the isolated rabbit heart

To assess the direct electrophysiologic effects of bupivacaine, we examined the spontaneous sinus rhythm and induced rapid and premature atrial and ventricular pacing in 11 isolated rabbit hearts perfused in the Langendorff apparatus with varying concentrations (designated by []) of bupivacaine (control, n = 2; 0.3 microgram/mL, n = 3; 1.5 micrograms/mL, n = 3; 3.0 micrograms/mL, n = 3). There was no change in sinus node automaticity or sinus node recovery time at any concentration and no evidence of abnormal automaticity. Depression of conduction was reflected by prolongation of the PR interval at the following concentrations: 1.5 micrograms/mL (65.0 ms before, 96.6 ms after) and 3.0 micrograms/mL (61.6 ms before, 103.3 ms after) and increase in atrial and ventricular pacing thresholds at 3.0 micrograms/mL (atrial: 0.86-8.6 mA, ventricular: 2.0-10.0 mA). No spontaneous tachyarrhythmias occurred; 2:1 spontaneous atrioventricular block (n = 1) and a decrease in maximal paced rate with 1:1 anterograde or retrograde atrioventricular conduction were noted at all concentrations of bupivacaine. Thus bupivacaine did not change automaticity but had a depressant effect on conduction at the atrial, ventricular, and atrioventricular levels, providing a basis for clinically occurring atrioventricular block and reentrant arrhythmias.     

High-dose vecuronium neuromuscular block: a comparison of arrhythmias and onset of block during sufentanil anaesthesia

This study compared the heamodynamic effects of sufentanil with those observed following concomitant sufentanil and highdose vecuronium administration to determine whether vecuronium induces bradyarrhythmias. Sixty coronary artery bypass patients were stratified into beta blocker (n = 30) or non-beta blocker (n = 30) groups and following induction with sufentanil (9 ± 3 μg · kg^?1) and midazolam (0.07 ± 0.04 mg · kg^?1), received either succinylcholine 1 mg · kg^?1 (SxCh), vecuronium 0.3 mg · kg^?1 (Vec 0.3), or vecuronium 0.5 mg · kg^?1 (Vec 0.5). Using a Holter ECG monitor, bradyarrhythmias were classified as mild (HR 46–50), moderate (HR 40–45) or severe (HR < 40). In the pre-induction period, there were no differences in the incidence of mild, moderate or severe bradyarrhythmias among the SxCh, Vec 0.3 or Vec 0.5 groups, in either the beta blocker or non-beta blocker groups. Following induction, there were similar reductions in mean heart rate and mean arterial pressure in all three muscle relaxant groups in both the beta and the non-beta blocker groups; however, there was no difference in the incidence of mild, moderate or severe bradyarrhythmias among the SxCh, Vec 0.3 or Vec 0.5 groups. The Vec 0.5 beta blocker group had a higher incidence of mild bradyarrhythmias (32 ± 36%) than the Vec 0.5 non-beta blocker group (2 ± 3% P = 0.017). Using EMG recording, the onset time of maximal neuromuscular block for the Vec 0.3 group (108 ± 17 sec) was longer (P < 0.05) than the SxCh (76 ±21 sec) and Vec 0.5 (82 ± 13 sec) groups, which were similar. We conclude: (i) vecuronium does not affect HR or the incidence of bradyarrhythmias following sufentanil administration and that the observed reduction in HR and mean arterial pressure were due to sufentanil administration, (ii) vecuronium (0.5 mg · kg^?1) provides an onset time of neuromuscular block similar to SxCh, and (iii) patients taking beta blockers preoperatively are more prone to develop bradyarrhythmias during sufentanil administration.     

Electrocautery-induced asystole in a scoliosis patient with a pacemaker

Pediatric heart condition management may include a variety of implanted cardiac devices. Monopolar electrocautery (Bovie) produces significant electromagnetic interference to these devices. This interference can alter the function of a cardiac generator resulting in a variety of complications including impaired cardiac output and asystole. We report the case of a 16 plus 2-year-old girl who presented with idiopathic scoliosis and a past medical history significant for complete congenital heart block treated with a DDD*** pacemaker. During surgery, the use monopolar electrocautery caused the patient to develop asystole and loss of pulsatile blood pressure. Electrocautery was subsequently terminated, the patient then returned to a normal sinus rhythm and blood pressure normalized.     

Electrophysiological effects of sevoflurane in comparison with propofol in children with Wolff-Parkinson-White syndrome

OBJECTIVE: To evaluate the electrophysiological effects of sevoflurane in children with Wolff-Parkinson-White (WPW) syndrome undergoing radiofrequency ablation. METHODS: We performed a prospective study of 15 patients with WPW syndrome who were scheduled for an electrophysiological study (EPS) and radiofrequency ablation. Anesthesia was induced with fentanyl (2 microg/kg), propofol (3 mg/kg), and vecuronium (0.1 mg/kg), and initially maintained using propofol (100 microg/kg), with bolus administration of fentanyl and vecuronium as required. Four intracardiac catheters were introduced for the EPSpropofol, which included measurements of sinus-node function, sinoatrial-node conduction, refractory periods (atrial, AV-node, accessory pathway anterograde and retrograde, and ventricular), and the characteristics of induced orthodromic tachycardia. The propofol was then replaced with sevoflurane (1 MAC adjusted for age) and the measurements were repeated (EPSsevoflurane). The EPSpropofol and EPSsevoflurane data were compared using the Wilcoxon signed-rank test. RESULTS: The mean (SD) age was 9.3 (6) years. After administration of sevoflurane, the duration of the antegrade effective refractory period of the accessory pathway increased (EPSpropofol, 283 (22) ms; EPSsevoflurane, 298 (25) ms; P = .004), as did the duration of the minimum pacing cycle with 1:1 atrioventricular conduction (EPSpropofol, 244 (41) ms; EPSsevoflurane, 273 (28) ms; P = .028). No significant changes were observed in the other parameters. Ablation of the accessory pathway was achieved in all patients. CONCLUSIONS: Sevoflurane partially modified the properties of the accessory pathway but did not prevent ablation.     

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)     

异氟醚和七氟醚对非体外循环冠状动脉旁路移植术患者心肌保护作用的比较

目的 比较异氟醚和七氟醚对非体外循环冠状动脉旁路移植术患者的心肌保护作用.方法 择期行非体外循环冠状动脉旁路移植术患者40例,性别不限,年龄40～55岁,体重55～94 kg,ASA分级Ⅱ或Ⅲ级,NYHA分级Ⅱ或Ⅲ级.采用随机数字表法,将患者随机分为2组(n=20):异氟醚组(Ⅰ组)和七氟醚组(S组).麻醉诱导:静脉注射咪达唑仑0.08 mg/kg、舒芬太尼2μg/kg和维库溴铵0.1 mg/kg,气管插管后行机械通气.麻醉维持:Ⅰ组吸入异氟醚,初始呼气末浓度1.2%;S组吸入七氟醚,初始呼气末浓度1.7%;两组静脉输注舒芬太尼0.04μg·kg-1·min-1和维库溴铵0.8μg·kg-1·min-1.通过调节异氟醚或七氟醚的呼气末浓度,维持BIS值40～50.分别于切皮前即刻、术毕、术后2和4 h时,采集中心静脉血样,测定血浆MB型肌酸激酶同工酶(CK-MB)的活性和心肌肌钙蛋白Ⅰ(cTnI)的浓度.记录术中心血管不良事件的发生情况.结果 与Ⅰ组比较,S组术中室性早搏、心动过速、心动过缓、室颤和S-T段抬高＞0.1 mV的发生率升高,术后血浆CK-MB活性和cTnI浓度升高(P＜0.05).结论 非体外循环冠状动脉旁路移植术患者异氟醚的心肌保护作用优于七氟醚.

Abstract：

Objective To compare the myocardial protective effects of isoflurane versus sevoflurane in patients undergoing off-pump coronary artery bypass grafting (OPCABG). Methods Forty ASA Ⅱ or Ⅲ patients (NYHA Ⅱ or Ⅲ ) of both sexes, aged 40-55 yr, weighing 55-94 kg, scheduled for elective OPCABG, were randomly divided into 2 groups ( n = 20 each): isoflurane group ( group Ⅰ) and sevoflurane group ( group S). Anesthesia was induced with midazolam, sufentanil and vecuronium. Patients were tracheal intubated and mechanically ventilated. Anesthesia was maintained with inhalation of isoflurane or sevoflurane and infusion of sufentanil and vecuronium. In group Ⅰ, the initial end-tidal concentration of isoflurane was 1.2%. In group S, the initial end-tidal concentration of sevoflurane was 1.7 %. BIS value was maintained at 40-50 by adjusting the end-tidal concentration of isoflurane or sevoflurane. The central venous blood samples were collected immediately before skin incision, at the end of surgery, 2 and 24 h after surgery for determination of plasma creatine kinase-MB (CK-MB) activity and cardiac troponin Ⅰ (cTnI) concentration. The adverse cardiovascular events were recorded. Results The incidences of ventricular premature beat, tachycardia, bradycardia, ventricular fibrillation and S-T segment elevation ( ＞0.1 mV) during surgery and the plasma CK-MB activity and cTnI concentration after surgery were significantly higher in group S than in group Ⅰ ( P ＜ 0.05). Conclusion Isoflurane has better myocardial protective effect than sevoflurane in patients undergoing OPCABG.     

Potency and maintenance requirement of atracurium and vecuronium given alone or together

A synergism exists between some competitive muscle relaxants. However, maintenance requirement of a combination of muscle relaxants has been evaluated only in paediatric patients. We studied 45 elective adult surgical patients (ASA I-II) during propofol-alfentanyl-N₂O-O₂-anaesthesia. The first 30 patients were randomized to receive either atracurium or vecuronium to create individual dose-response curves for these muscle relaxants. ED₉₅-values for atracurium and vecuronium were 260±9 and 59±3 μg · kg^-1, respectively (mean±s.e.mean). Requirements of atracurium and vecuronium to maintain an 85–95% neuromuscular blockade were 301 and 83 μg kg^-1 h^-1, respectively. An additional 15 patients received a combination of atracurium and vecuronium (cAV) in an equipotent dose ratio. An ED₉₅ of a cAV was 94± 7 μg · kg^-1 of atracurium together with 21±2 μg · kg^-1 of vecuronium, or 72±6% of one ED₉₅ dose of a parent agent. Potentiation was significant ( P =0.0001). A maintenance requirement of a cAV was 120 μg kg^-1 h^-1 of atracurium together with 27 μg kg^-1 h^-1 of vecuronium. Thus, a significant potentiation was maintained also during the course of anaesthesia. A cAV had an effect like one intermediate-acting agent. If a cAV is used instead of using atracurium or vecuronium alone, the maximal reduction of drug consumption would be approximately 30%.     

Electrophysiological effects of intravenous dantrolene on canine heart

The electrophysiological effects of an intravenous dantrolene infusion (10 mg kg-1) were evaluated in healthy, anaesthetized dogs by intracardiac electrophysiological study. Dantrolene administration resulted in a significant prolongation of the refractory periods of the right atrium and ventricle, while the functional refractory period of the AV node was not altered. A slight increase of AV nodal conduction, measured as atrial-His bundle interval, without any change in infranodal conduction, measured as His bundle-ventricular interval, was observed during sinus rhythm. Dantrolene had no significant effects on surface ECG parameters. We conclude that intravenously administered dantrolene, at the maximal recommended doses, has primary effects on electrophysiological parameters. These findings support the hypothesis that the beneficial effects of dantrolene on cardiac arrhythmias associated with malignant hyperthermia may be related to its intrinsic activity on the electrophysiological properties of the heart, but confirmation requires further investigations on induced arrhythmias in experimental models.     

Prolonged cardiac arrest unveiled silent sick sinus syndrome during general and epidural anesthesia

Patients who have silent sick sinus syndrome (SSS) can show various unexpected arrhythmias during surgery. The severity of these bradyarrythmias is affected by anesthetic methods. We report a unique case of a patient with silent SSS who developed 40 s of asystole under combined general and epidural anesthesia. A 40-year-old woman with no apparent cardiac disease underwent abdominal hysterectomy. General anesthesia was induced and maintained with propofol, fentanyl, and vecuronium combined with thoracic epidural anesthesia. During surgery, severe bradycardia, triggered by peritoneal manipulation, occurred, leading to 40 s of asystole. She was diagnosed as having SSS by a postoperative 24-h Holter electrocardiogram. We propose that the possible existence of SSS should be kept in mind even in a patient who shows no abnormalities on routine preoperative examination, especially in those in whom vagomimetic anesthetic methods are used.     

Three balanced anesthetic techniques for neuroanesthesia: infusion of thiopental sodium with sufentanil or fentanyl compared with inhalation of isoflurane.

STUDY OBJECTIVE: To compare emergence from anesthesia and the hemodynamic and respiratory depressant effects of thiopental sodium infusion plus sufentanil or fentanyl with those of isoflurane as the primary component of a balanced technique for neuroanesthesia. DESIGN: Randomized, double-blind, prospective study. SETTING: University hospital and its affiliated Veterans Affairs Medical Center. PATIENTS: Thirty patients undergoing elective craniotomy for aneurysm or tumor. INTERVENTIONS: Thiopental with infusion of sufentanil 0.1 microgram/kg/hr, thiopental with infusion of fentanyl 1 microgram/kg/hr, or inhalation of 0.25% to 2% isoflurane as the major component of a balanced anesthesia technique that included nitrous oxide (N2O) and vecuronium (potency ratio of sufentanil to fentanyl, 10:1). MEASUREMENTS AND MAIN RESULTS: Intraoperative stress response (as indicated by intraoperative hypertension) was said to be the percentage of time the patient required administration of an antihypertensive drug, measuring from the first dose of thiopental to discontinuation of N2O at the end of the procedure, excluding any period of induced hypotension. Rapidity of emergence was measured by the number of minutes from discontinuation of N2O to first opening of the eyes on command. Adequacy of spontaneous ventilation was evaluated by determining partial pressure of arterial carbon dioxide 1, 2, and 3 hours after discontinuation of N2O. Extent of vasoactive drug administration for control of intraoperative hypertension (as determined by the clinicians caring for the patients) was described by minutes of vasodilator infusion and milligrams of propranolol or labetalol administered. The frequency of postoperative hypertension was defined as the number of patients in each group who required medication for postoperative hypertension. No significant differences in variables were found for thiopental/sufentanil, thiopental/fentanyl, or isoflurane when these drugs were used with N2O and vecuronium. CONCLUSIONS: Any one of these balanced anesthetic techniques appears appropriate for craniotomy.     

The effect of epidural bupivacaine on vecuronium–induced neuromuscular blockade in children

The efTect of epidural bupivacaine on potency and duration of action of vecuronium–induced neuromuscular blockade (NMB) was evaluated in 30 general surgical paediatric patients (ASA I–II) of three to ten years of age. Premedication was midazolam 0.5 μg kg^-1 orally (max 15 mg). In addition to general anaesthesia, 15 of the children received a lumbar epidural block with 0.5% bupivacaine 2.5 mg kg^-1. Anaesthesia was induced and maintained with N₂O:o₂ (2:1), propofol and alfentanil. NMB was monitored by adductor pollicis EMG with the train–of–four stimulus every 20 sec. Thirty minutes following the epidural bupivacaine injection (mean plasma concentration 0.86 μg ml^-1) or induction of anaesthesia a cumulative dose–response curve of vecuronium was established to achieve a 95% depression of the twitch response. Thereafter, NMB was allowed to recover spontaneously. ED doses of vecuronium were 19–22% greater in the control group than in the epidural group. ED^ doses were 33.8 (s.e.mean 1.3) μg kg"¹ and 28.4 (2.2) μg kg"', respectively ( P <0.05). There were no differences in recovery times from NMB between control and epidural group, the recovery index (time of twitch height to recover from 25 to 75%) being 6.4 (0.4) min and 7.0 (0.9) min, respectively. However, a negative correlation was found between bupivacaine plasma concentration and an ED₅₀ dose of vecuronium ( P =0.01). Our results indicate that vecuronium is slightly more potent in children with bupivacaine epidural block than in children without it.     

Marked bradycardia during anesthetic induction treated with temporary cardiac pacing in a patient with latent sick sinus syndrome

A 59 year-old woman with latent sick sinus syndrome was scheduled to undergo ophthalmic surgery including phacoemulsification and aspiration, vitrectomy, photocoagulation and intraocular lens under general anesthesia. Preoperative ECG showed sinus rhythms of 77 bpm without bradycardia or a sinus pause. Total intravenous anesthesia with propofol, fentanyl, ketamine and vecuronium was employed for the induction of anesthesia immediately followed by severe bradycardia with a rate of 36-40 bpm including sinus arrest and atrio/nodal escaped beats. Intravenous atropine was ineffective to restore the heart rate and then urgent temporary pacing was successfully applied to overcome bradycardia. The patient recovered uneventfully from anesthesia. She complained of being dizzy and faint with prominent bradycardia due to sick sinus syndrome three months after the surgery. Therefore she underwent permanent cardiac pacemaker implantation successfully. Temporary pacing is mandatory when anesthesia is given to surgical patients with latent sick sinus syndrome.     

Suspected diltiazem intoxication resulting in repeated asystole after the induction of anesthesia

We present a case of diltiazem intoxication resulting in repeated asystole after the induction of anesthesia. A 39-year-old man was diagnosed as subarachnoid hemorrhage, and cerebral aneurysm clipping was scheduled on the next day. Electrocardiogram revealed normal sinus rhythm with complete right bundle branch block. Continuous intravenous administration of diltiazem, nicardipine and midazolam were started for intractable hypertension and tachycardia. In the operating room, electrocardiogram showed atrioventricular nodal rhythm. Nicardipine and midazolam were stopped and anesthesia was induced with thiamylal, fentanyl and vecuronium, and was maintained with sevoflurane. After tracheal intubation, the patient developed asystole, and cardiopulmonary resuscitation was provided immediately. Diltiazem was stopped. Cardiac rhythm was restored 8 min afterwards; however, asystole recurred six times. Temporary cardiac pacing was effective, and percutaneous cardiopulmonary support (PCPS), intraaortic balloon pumping (IABP), and continuous hemodiafiltration (CHDF) were initiated. The operation was canceled. On the next day, normal sinus rhythm was restored and the temporary pacing, PCPS, IABP, and CHDF were discontinued. Cerebral aneurysm was treated by endovascular coiling and the patient was discharged from the hospital without sequelae. This case illustrates asystole associated with diltiazem intoxication. It is necessary to consider this potential complication when diltiazem is used.     

General anesthesia for a patient with asymptomatic sick sinus syndrome

A 67-year-old man with glioblastoma was scheduled for craniotomy. Before anesthesia induction, asymptomatic bradycardia (40 beats x min(-1)) occurred, and was resistant to atropine 0.4 mg. The surgery was postponed. He was diagnosed as sick sinus syndrome (sinus arrest). He received implantation of a temporary cardiac pacemaker on the day before the rescheduled surgery. Anesthesia was induced with thiopental 400 mg, fentanyl 200 microg, vecuronium 10 mg and isoflurane 5%, and maintained with isoflurane 1-2% in oxygen 3 l x min(-1) and air 3 l x min(-1). Pacing mode was set to fixed rate asynchronous pacing in the ventricle with a rate of 50 beats x min(-1) after anesthesia induction. Surgery was completed in 8 hours and 45 minutes without any complications. The pacing wire was removed the next day. For patients with sick sinus syndrome, implantation of the pacemaker is indicated in case of bradycardia-tachycardia syndrome or with any clinical symptoms. However, a pacemaker should be implanted before general anesthesia even in a patient with no clinical symptoms because of cardiovascular instability induced by anesthesia.     

Hemodynamic effects of vecuronium in man

The cardiovascular effects of vecuronium (Organon NC 45 or Norcuron) in man were determined through different protocols using continuous recording of heart rate, arterial blood pressure and parameters obtained by a Swan-Ganz catheter. In healthy anaesthetized patients (n = 23), the effects of a dose of 0.1 mg X kg-1 pancuronium (group A) were compared to those of two doses of vecuronium: 0.1 mg X kg-1 (group B) and 0.3 mg X kg-1 (group C). Pancuronium induced an increase in heart rate (+12%), arterial pressure (+16%) and cardiac index (+8%). No change occurred with vecuronium. In patients under mechanical ventilation in an intensive care unit, we compared the effects of pancuronium 0.1 mg X kg-1 (group D; n = 10), d-tubocurarine (group E; n = 11), vecuronium 0.1 mg X kg-1 (group F; n = 9) and 0.3 mg X kg-1 (group G; n = 10). Pancuronium induced an increase in heart rate (+12%), arterial pressure (+8%) and cardiac index (+9%). d-Tubocurarine induced an increase in heart rate (+6%), a decrease in arterial pressure (-24%) and cardiac index (-17%). No change was observed after vecuronium 0.1 mg X kg-1. After vecuronium 0.3 mg X kg-1, the changes were minimal: a slight decrease in arterial pressure (-5%), a very slight (+3%) and transient (3 min) increase in heart rate were observed. The doses were approximately equipotent in groups A, B and C, whereas the dose of 0.3 mg X kg-1 in group G is about 10 times the 90% effective dose of vecuronium. In geriatric patients with per- or postoperative circulatory deficiency (group H; n = 10, mean age 83 yr), no hemodynamic side effects were observed. Vecuronium seems to be a non-depolarizing neuromuscular blocking agent devoid of cardiovascular side-effects at the generally usual doses.