Halothane, enflurane and isoflurane anaesthesia for adenoidectomy in children, using two different premedications

In 48 children subjected to adenoidectomy, comparisons of airway problems, heart rates, cardiac arrhythmias, ventilation and stress hormone reactions were studied during halothane, enflurane and isoflurane anaesthesia. Sixteen children were anaesthetized with either of the three agents and eight patients in each group received diazepam 0.25 mg kg-1 and atropine 0.015 mg kg-1 rectally (DA) as premedication and the remainder diazepam 0.5 mg kg-1, morphine 0.15 mg kg-1 and scopolamine 0.01 mg kg-1 (DMS) rectally. All children were intubated and breathing spontaneously. Equianaesthetic inspired concentrations of halothane, enflurane and isoflurane were used. Airway problems were of the same magnitude during halothane and isoflurane anaesthesia but were less frequent with both agents compared with enflurane anaesthesia. DMS reduced the number of airway reactions in all groups. Respiratory rates were uninfluenced by anaesthesia, intubation and surgery during enflurane anaesthesia. Cardiac arrhythmias were less frequent with enflurane and isoflurane than with halothane. Plasma ACTH and cortisol were similar with all three agents. During induction of anaesthesia in the DA-premedicated halothane group, however, plasma catecholamines were higher than in the group which received DMS, in contrast to the findings during enflurane and isoflurane anaesthesia. The DMS premedication decreased the response of plasma ACTH, cortisol and plasma catecholamines to surgery.     

Haemodynamic effects of propofol vs thiopental in infants: an echocardiographic study

Rapid i.v. induction of general anaesthesia is indicated in infants at risk of vomiting or regurgitation to reduce the risk of aspiration of gastric contents. Propofol is an alternative to thiopental in infants, and we have compared cardiovascular changes when propofol or thiopental was used for induction of anaesthesia in infants. Twenty infants, ASA I or II, aged 1-11 months, undergoing elective surgery were allocated randomly to receive either thiopental or propofol for i.v. induction. Cardiovascular and echocardiographic data were recorded in both groups before, during and for 5 min after induction of anaesthesia. Doses required to induce anaesthesia in each group were mean 10.3 (SD 0.9) mg kg-1 of thiopental and 6.1 (0.6) mg kg-1 of propofol. Thiopental did not alter significantly systolic or mean arterial pressure, afterload indices, rate-corrected velocity of circumferential fibre shortening or cardiac index, but decreased shortening fraction at 1 and 5 min after induction compared with awake values. Propofol did not alter heart rate, shortening fraction, rate-corrected velocity of circumferential fibre shortening or cardiac index at 1 and 5 min after i.v. induction compared with awake values. After induction, systolic and mean arterial pressures and afterload indices decreased more after induction with both agents, but did not become abnormal. Thus propofol decreased arterial pressure more than thiopental because of an effect on afterload. Cardiac output remained unchanged with both agents.      

Cardiac Arrhythmias in Non-intubated Children during Adenoidectomy. A Comparison between Enflurane and Halothane Anaesthesia

The incidence of cardiac arrhythmias, heart rate, blood pressure, capillary perfusion and end-tidal CO2 tension were studied in 167 healthy children 1-12 years of age undergoing adenoidectomy (n = 82) and myringotomy (n = 85) during enflurane and halothane anaesthesia. The incidence of cardiac arrhythmias was significantly lower during myringotomy than during adenoidectomy. In children undergoing adenoidectomy the incidence of arrhythmias was 38.9% during enflurane anaesthesia and 86.6% during halothane anaesthesia (P less than 0.001). In the halothane group ventricular arrhythmias were observed in 19 patients (41.3%) but only in one child (2.8%) in the enflurane group. The ventricular arrhythmias seen during halothane anaesthesia were unifocal in six patients and multifocal in five and classified as ventricular tachycardia in eight children. Heart rate was increased by about 40% at the onset of ventricular arrhythmias. The heart rate remained unchanged with enflurane anaesthesia during surgery, which may reflect a decreased sympathomimetic activity. It is suggested that the low incidence of ventricular arrhythmias during enflurane anaesthesia may be explained by the combination of a reduced sympathomimetic activity and a lowered susceptibility of the myocardium to the actions of endogenous catecholamines.     

Electroconvulsive therapy-induced cardiac arrhythmias during anesthesia with methohexital, thiamylal, or thiopental sodium.

STUDY OBJECTIVE: To determine the frequency of electroconvulsive therapy (ECT)-induced arrhythmias under methohexital, thiamylal, or thiopental sodium anesthesia with and without atropine premedication. DESIGN: A randomized, double-blind study, placebo-controlled for atropine. SETTING: The inpatient psychiatric unit at a university medical center. PATIENTS: Forty-nine patients scheduled for ECT. INTERVENTIONS: Atropine 0.6 mg intravenously (IV) or an equal volume of normal saline IV was given before IV induction of anesthesia with methohexital 0.5 to 1.0 mg/kg, thiamylal 1.5 to 2.5 mg/kg, or thiopental sodium 1.5 to 2.5 mg/kg. MEASUREMENTS AND MAIN RESULTS: Single-lead electrocardiogram (ECG) recordings were made for 1 minute before induction, during induction of anesthesia, and for 5 minutes after the ECT stimulus. Each ECG was evaluated for arrhythmias and evidence of ischemia in a blinded fashion. Blood pressure and ECG evidence of ischemia did not differ among the groups. Seizure duration was significantly (p less than 0.05) prolonged by a mean of 5 seconds during methohexital anesthesia compared with thiopental sodium and thiamylal (47.6 +/- 18.6 seconds, 42.7 +/- 13.2 seconds, and 42.7 +/- 15.2 seconds, respectively). The frequency of sinus bradycardia was decreased (p less than 0.05) with methohexital (8%) compared with thiopental sodium (20%) and thiamylal (20%). The frequency of premature atrial contractions was decreased (p less than 0.05) with methohexital (43%) compared with thiamylal (61%) but not with thiopental sodium (57%). The frequency of premature ventricular contractions was decreased (p less than 0.05) with methohexital (27%) compared with thiopental sodium (44%) but not with thiamylal (40%). Atropine decreased the frequency of bradycardia (9% vs. 24%) and premature atrial contractions (47% vs. 61%) and increased the frequency of sinus tachycardia (88% vs. 75%). CONCLUSIONS: These data suggest that anesthesia for ECT therapy should be induced with methohexital to minimize the possibility of potentially life-threatening cardiac arrhythmias. Atropine premedication may further decrease the frequency of premature atrial contractions and bradycardia, while increasing the frequency of tachycardia.     

Effect of i.v. Atropine on Cardiac Rhythm, Heart Rate, Blood Pressure and Airway Secretion during Isoflurane Anaesthesia

Atropine, 0.01 mg kg-^-1, was given i.v. to 30 patients before mask anaesthesia with isoflurane. Controls (n = 28) received a placebo. ECG was recorded on tape throughout anaesthesia and analysed later. There were no ventricular arrhythmias, but six patients in the atropine group and two patients in the placebo group had supraventricular arrhythmias of very short duration. Most cases occurred shortly after atropine, i.e. before anaesthesia. Heart rate increased significantly in both groups, more so after atropine (up to 60%), and remained elevated. In both groups blood pressure fell after the induction of anaesthesia but was close to control during surgery. Suction of airway secretions was necessary in three placebo patients, but excessive secretions were not met. The frequency of airway reflexes was similar in the two groups. It is concluded that due to the pronounced tachycardia the routine use of i.v. atropine can hardly be recommended before mask anaesthesia with isoflurane.     

The significance of tramadol as an intraoperative analgesic. A randomized double-blind study in comparison with placebo

Tramadol-N2O anaesthesia as recommended by Stoffregen was studied in 40 patients (ASA I-II) undergoing elective orthopaedic or lower abdominal surgery. Fentanyl and droperidol (Thalamonal)/atropine were given as i.m. premedication, induction was performed using methohexitone, succinylcholine and pancuronium, ventilation was controlled by means of a Takaoka respirator (N2O/O2 79:21, 4 breaths/min). Intraoperative analgesia was provided by a biphasic tramadol infusion. However, half the patients were given placebo infusion (0.9% NaCl) instead of tramadol in a randomized and double-blind manner in order to evaluate tramadol efficacy as one component of balanced anaesthesia. Whenever anaesthetic depth appeared to be insufficient enflurane (0,5-1.5 vol.%) was administered for short periods. Blood pressure, pulse rate as well as cumulative enflurane dose were documented; postoperative analgesic requirement and awareness of intraoperative events (tape recorder music offered via earphones) were further used to assess tramadol effects. Anaesthesia proved to be quite comparable in both groups; patients felt satisfied without exception. Relative cumulative enflurane times (vol.% . min, related to duration of anesthesia) did not differ significantly (tramadol 5.9%, placebo 4.9%). When enflurane had not been necessary (tramadol n = 13, placebo n = 10), mean percentage rises of blood pressure or pulse rate, related to preoperative values, were found to be slightly higher in the tramadol group. Postoperative analgesic requirement was reduced significantly after tramadol. Striking differences between the two groups, on the other hand, were shown with respect to intraoperative awareness: while patients receiving placebo proved to be amnaesic, 65% of tramadol patients were aware of intraoperative music.(ABSTRACT TRUNCATED AT 250 WORDS)     

QT interval and QT dispersion during the induction of anaesthesia in patients with subarachnoid haemorrhage: a comparison of thiopental and propofol

BACKGROUND AND OBJECTIVE: Thiopental prolongs the QT interval more than propofol, and the two induction agents were compared in patients with subarachnoid haemorrhage predisposed to electrocardiographic abnormalities and cardiac dysrhythmias. METHODS: Twenty-nine patients were studied randomly. Anaesthesia was induced with either thiopental or propofol and fentanyl; vecuronium was used as a neuromuscular blocking agent. The electrocardiogram and arterial blood pressure were monitored from before the induction of anaesthesia to 2 min after endotracheal intubation. RESULTS: The median QT interval was at baseline 423 ms in the thiopental group and at 432 ms in the propofol group, and it increased in the thiopental group to 446 ms and decreased in the propofol group to 425 ms (P < 0.01 between groups). After induction and endotracheal intubation, the number of patients with increased QT dispersion was greater in the propofol group (P < 0.05). The incidence of cardiac dysrhythmias was similar in the study groups. CONCLUSIONS: Thiopental and propofol are equally suitable for the induction of anaesthesia in patients with subarachnoid haemorrhage.     

Heart rate response to atropine in humans anaesthetized with five different techniques

Atropine, 0.01 mg.kg-1, was given intravenously before the start of surgery to 169 patients who were anaesthetized with one of five different techniques; halothane, enflurane, cervical epidural, lumbar epidural or narcotic anaesthesia in addition to nitrous oxide and oxygen. Atropine produced a significant increase in heart rate (HR) within 1 min in all patients studied; the HR increases in patients anaesthetized with halothane (37 +/- 11 beats.min-1, n = 37) or narcotic (34 +/- 12 beats.min-1, n = 30) were significantly greater than in those anaesthetized with enflurane (25 +/- 10 beats.min-1, n = 35; P less than 0.01) or epidural anaesthesia. Because of the presence of an acute cardiac sympathectomy, the patients who received cervical epidural anaesthesia were expected to have different responses to the atropine. However, there was no significant difference in the HR increases between the patient groups with cervical (19 +/- 12 beats.min-1, n = 32) and lumbar (22 +/- 8 beats.min-1, n = 35) epidural anaesthesia. Atropine also produced a small but significant increase in arterial pressure in all five groups of patients. These results suggest that the cardiac responses to atropine may differ depending on the individual anaesthetic agent used, and are likely dependent upon the agent's effect on autonomic nervous system activity.     

CBF and CMRo2 during craniotomy for small supratentorial cerebral tumours in enflurane anaesthesia. A dose-response study

In 14 patients with supratentorial cerebral tumours with midline shift less than or equal to 10 mm, cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were measured twice on the contralateral side of the craniotomy, using a modification of the Kety & Schmidt method. For induction of anaesthesia, thiopental, fentanyl and pancuronium were used. The anaesthesia was maintained with enflurane 1% in nitrous oxide 67%. Moderate hypocapnia to a level averaging 4.3 kPa was achieved. The patients were divided into two groups. In Group 1 (n = 7), 1% enflurane was used throughout the anaesthesia, and CBF and CMRO2 measured about 70 min after induction averaged 30.1 ml 100 g-1 min-1 and 1.98 ml O2 100 g-1 min-1, respectively. During the second CBF study 1 h later, CBF and CMRO2 were unchanged (P greater than 0.05). In Group 2 (n = 7), the inspiratory enflurane concentration was increased from 1 to 2% after the first CBF measurement. In this group a significant decrease in CMRO2 was observed, while CBF was unchanged. In six patients EEG was recorded simultaneously with the CBF measurements. In patients subjected to increasing enflurane concentration (Group 2), a suppression in the EEG activity was observed without spike waves. It is concluded that enflurane induces a dose-related decrease in CMRO2 and suppression in the EEG activity, whereas CBF was unchanged.     

CARDIOVASCULAR RESPONSES TO ENFLURANE INDUCTION FOLLOWED BY SUXAMETHONIUM IN CHILDREN

Induction of anaesthesia with enflurane 5 vol% plus 70% nitrousoxide in oxygen was followed by suxamethonium 1, 1.5 or 2mgkg^–1 i.v. and the cardiovascular changes studied in 58children. The eyelash reflex disappeared in 44 ± 1.2(SEM) s and the venepuncture could be performed 1.8 ±0.05 (SEM)min after the start of enflurane anaesthesia. Theincrease in systolic arterial pressure after tracheal intubationwas less marked after enflurane than after thiopentone (takenfrom an earlier study). Heart rate increased significantly afterall doses of suxamethonium, but no cardiac arrhythmias wereseen. The QT interval was significantly prolonged by enflurane(P< 0.001), but remained unchanged after suxamethonium.     

Glycopyrrolate vs. atropine during anaesthesia for laryngoscopy and bronchoscopy

As glycopyrrolate has been reported superior to atropine with respect to reduction of salivation, stability of cardiac rate and rhythm, and recovery, a comparison of these properties of the two drugs and placebo was made in 45 patients undergoing direct laryngoscopy and 45 patients undergoing bronchoscopy, in most cases followed by mediastinoscopy. When given i.m. 30 min before anaesthesia (midazolam, alfentanil, thiopentone, and suxamethonium), the two test drugs were found to be equally potent regarding the antisialogogic effect. The same increase in heart rate after the test drugs was seen before induction, and during anaesthesia heart rate rose to the same level in the placebo group as the test groups. During anaesthesia, blood pressure was lowest in the atropine group. No differences could be demonstrated with respect to cardiac arrhythmias, possibly due to the small size of the material. The present study gives no reason for preferring either drug, and only the efficacy of both test drugs in controlling airway secretions provides an argument for using any anticholinergic drug when laryngoscopy or bronchoscopy is performed under the conditions of the present study.     

Changes in Heart Rate and Impulse Conduction After a Single Dose of Succinylcholine

The effect of 1 and 2 mg/kg b.w. succinylcholine on changes in cardiac rate and rhythm was studied in 40 fit, adult patients undergoing non-emergency surgery. Induction of anaesthesia consisted of atropine 0.007 mg/kg b.w., pancuronium 0.015 mg/kg b.w., thiopental 5 mg/kg and succinylcholine 1 or 2 mg/kg b.w. Succinylcholine 1 mg/kg b.w. intravenously resulted in a significant decrease in heart rate after 1 min. 1 his decrease persisted after 2 min. The heart rate was unchanged 1 and 2 min after succinylcholine 2 mg/kg b.w. When the two groups were compared, no significant difference was found. No serious cardiac arrhythmias were seen. These results suggest that the larger single dose of succinylcholine is not more likely to cause severe bradycardia or asystole.     

Enflurane inhibits muscle fasciculations caused by suxamethonium in children

Eighty-three children with a mean age of 2.7 years were anaesthetized with either thiopental 5 mg/kg followed by suxamethonium 1.5 mg/kg i.v. or with enflurane 5 vol% in 70% nitrous oxide in oxygen via a face mask. In the enflurane group, venepuncture was performed when the children were unconscious, 1.8 +/- 0.05 (s.e.) min after the start of anaesthesia. After enflurane, suxamethonium 1, 1.5 or 2 mg/kg was administered i.v. for endotracheal intubation. The incidence and duration of muscle fasciculations after suxamethonium were significantly lower (P less than 0.01) in the enflurane groups than in the thiopental group. The fasciculation index was significantly lower (P less than 0.01) in the enflurane groups than in the thiopental group. In the enflurane groups, intubating conditions were better (P less than 0.05) in the children treated with suxamethonium 2 mg/kg than in those treated with suxamethonium 1 mg/kg.     

The effect of enflurane anaesthesia and operation on the sympathoadrenal and adrenocortical system (author's transl)

The effect of enflurane anaesthesia on the sympathoadrenal system, the hypothalamic-hypophyseal-adrenocortical system, and on the circulatory system was investigated in patients undergoing ophthalmic surgery. Blood concentrations of adrenaline, noradrenaline, ACTH, cortisol, and arterial blood pressure and heart rate were measured in 10 patients 30 min after premedication (I), 3-5 min after surgical incision (II), 20 or 45 min after surgical incision (III) and in 7 of 10 patients 10-15 min after extubation (IV). After conventional induction anaesthesia was maintained with enflurane (1.5-2.0%), combined with N2O/O2 2:1, and intermittent relaxation. Plasma adrenaline, ACTH, cortisol and heart rate increased significantly during operation, while plasma noradrenaline and blood pressure did not change significantly. Thus enflurane anaesthesia could not completely inhibit the increased activity of sympathoadrenal and hypothalamic-hypophyseal-adrenocortical system caused by surgical stress.     

Hypotensive anesthesia with isoflurane and enflurane during total hip replacement: a comparative study of catecholamine and renin angiotensin responses

Catecholamine and renin-angiotensin responses to enflurane- or isoflurane-hypotensive anesthesia were compared in a randomized study. Two groups of 10 patients undergoing total hip arthroplasty were premedicated with morphine hydrochloride (0.1 mg/kg). Anesthesia was induced with thiopental and the trachea intubated after pancuronium. Equal concentrations of each volatile agent (1.3 MAC) were administered until mean arterial blood pressure decreased to 50-60 mm Hg. Hemodynamic data and blood samples for measurements of plasma renin activity (PRA) and plasma epinephrine (E) and norepinephrine (NE) concentrations were collected 1) after induction and intubation but before the start of isoflurane or enflurane; 2) 15 min (T15) after the start of isoflurane or enflurane administration; and 3) 45 min (T45) after the start of isoflurane or enflurane administration. The desired level of hypotension was achieved at T15 with isoflurane and at T45 with both anesthetics. When hypotension was achieved, cardiac index and stroke index were significantly lower in the enflurane group while systemic vascular resistance index was lower in the isoflurane group. Increases in E and NE levels above baseline levels were significantly greater in the isoflurane group than in the enflurane group. Use of isoflurane to induce hypotension is associated with more rapid induction of hypotension, less depression of cardiac output, and better preservation of homeostatic responses than is use of enflurane.     

Anaesthetic induction with alfentanil: comparison with thiopental, midazolam, and etomidate

The speed, side effects and cardiovascular changes associated with anaesthetic induction and endotracheal intubation following alfentanil (20 micrograms/kg/min, IV), thiopental (84 micrograms/kg/min, IV), etomidate (5 micrograms/kg/min, IV) and midazolam (20 micrograms/kg/min, IV) prior to halothane-nitrous oxide general anaesthesia were evaluated and compared in 80 patients undergoing elective general surgical operations. Anaesthetic induction was fastest with etomidate and thiopental (approximately one minute) and slowest with midazolam (about two minutes). Systolic arterial blood pressure (SBP) was decreased at the moment of unconsciousness with thiopental but unchanged with the other compounds. Heart rate (HR) was increased at unconsciousness with midazolam and thiopental but unchanged with etomidate and alfentanil. After intubation HR was increased in all groups except those induced with alfentanil. Arrhythmias were infrequent (5 per cent or less in all groups). Rigidity during induction only occurred with alfentanil (55 per cent) and pain on injection only with etomidate (35 per cent) and alfentanil (5 per cent). Postoperative vomiting was infrequent in all groups (15 per cent) except etomidate (55 per cent). No patient remembered any aspect of laryngoscopy or the operation and all rapidly regained consciousness at the end of operation. The results of this study demonstrate that with the exception of rigidity (which is easily overcome with succinylcholine) and a slightly slower onset of action, alfentanil compares favourably as an induction agent with thiopental and is better than midazolam and etomidate. Alfentanil is superior to all three other induction agents with respect to cardiovascular stability during induction and intubation.     

不同全麻诱导药对循环及内分泌功能的影响

目的 评价三种静脉药在全麻诱导时对循环、垂体－肾上腺皮、髓抽内分泌功能的影响。方法 将择期全麻手术病人43例,随机分为三组：Ⅰ（组（异丙酚2.5mg/kg）;Ⅱ组（硫喷妥钠5mg/kg）和Ⅲ组（依托咪酯03mg/kg）各14例。行桡动脉直接测压,同时边疆监测ECG、SpO2。快速静注琥珀碱1.5-2.0mg/kg行气管插管。插管2min后静注维库溴铵4mg,5min后各组吸入安氟醚维持1.3MAC,15min后复合吸入N2O。在诱导前（T0）,窥喉插管即刻（T1）,插管后2min（T2）,5min(T3),15min(T4)取外周静脉血测定血浆去甲肾上腺素（NE）、肾上腺素（E）、皮质醇（cort）、泌乳素（PRL）、生长素（GH）、β－内啡肽（β－EP）、胰岛素和血糖的水平。结果 异丙酚诱导气管插管能抑制高血压反应,不增加心肌耗氧量,明显优于友喷妥钠和依插咪酯;三药诱导气管插管均不能抑制E和NE升高;均使腺垂体分泌PRL增加,而H、β-EP无变化;插管后15min依托咪酯使肾上腺皮质分泌cort减少;使血糖升高,胰岛素降低;说明对糖耐量呈现抑制作用。结论 异丙酚对循环和内分泌影响较小,是目前首选的全麻诱导药。     

Effect of pre-treatment with intravenous atropine or glycopyrrolate on cardiac arrhythmias during halothane anaesthesia for adenoidectomy in children

We studied the effect of anticholinergics on the incidence of cardiac arrhythmias during paediatric anaesthesia. ASA I-II children (n = 77) undergoing adenoidectomy were randomly allocated to three groups. Intravenous atropine 0.02 mg kg-1 was given in group A (n = 25), glycopyrrolate 0.004 mg kg-1 in group G (n = 27) and physiological saline in group P (n = 25) 3 min before the induction of anaesthesia. The children breathed spontaneously under halothane anaesthesia with 66% nitrous oxide in oxygen after induction with thiopentone and succinylcholine. Perioperative monitoring of the ECG (Holter recordings) and oxygen saturation was carried out. Ventricular tachycardia occurred in 16.0%, 18.5% and 12.0% of the children in groups A, G and P respectively (ns). The incidence of ventricular arrhythmias (ventricular tachycardia, ventricular bigeminy, ventricular premature beats > 10) was 20.0% in group A, 44.4% in group G and 36.0% in group P (ns). Bradycardia (< 70 beats min-1) was observed in 0.0%, 14.8% and 24.0% of patients in groups A, G and P respectively (A vs P, P < 0.05). The use of anticholinergics did not influence the incidence of ventricular arrhythmias during halothane anaesthesia in children. Bradycardia was more common in the placebo group than in the atropine group.      

Arrhythmias during Halothane Anesthesia I: The Influence of Atropine During Induction with Intubation

The changes in cardiac rhythm which occurred during induction of halothane-N₂O/O₂ anesthesia with thiopenthal and one single dose of suxamethonium for intubation were studied in two groups of patients, one (at random) of which was given atropine intravenously 0.1 mg/10 kg 2 min before induction.
There was a significantly higher incidence of arrhythmias in the atropine group ( P < 0.01) - including sinustachycardia ® 120 beats/min.
The most common arrhythmias were supra ventricular ectopies. About half of those registered in the atropine group arose in direct connection with atropine administration. There was a relative accumulation of arrhythmias in connection with intubation in both groups. Ventricular ectopies were only observed during and immediately after intubation, and most often in the atropine group. The occurrence of arrhythmias was not age-dependent.
The cardioacceleration following intubation was significantly higher in the atropine group ( P <0.01). No consistent changes in blood pressure as the result of the change in cardiac rhythm were observed in connection with the single arrhythmia episode or following atropine. On the other hand, no advantage could be seen in the use of the drug, and the cardioacceleration which is inherent in its action may be injurious to patients with a limited cardiac reserve.     

QT interval of the ECG, heart rate and arterial pressure using five non-depolarizing muscle relaxants for intubation

The QT interval, heart rate and arterial pressure were measured during anaesthetic induction in 186 patients without cardiovascular diseases or any preoperative drugs. The study was randomized and double-blind. The patients were premedicated with either pethidine 1 mg/kg + atropine 0.01 mg/kg or with only pethidine 1 mg/kg i.m. Anaesthesia was induced with thiopental. After both types of premedication, either d-tubocurarine 0.5 mg/kg, alcuronium 0.3 mg/kg, pancuronium 0.1 mg/kg, vecuronium 0.1 mg/kg or atracurium 0.5 mg/kg was injected after thiopental. Laryngoscopy was performed 4 min after the relaxant. The control values of the QT intervals (mean value 433 ms, range of the mean values 422-453 ms), were comparable. After thiopental, the mean values in the groups were no longer in the normal range (less than 440 ms). After atropine, the values at 3 min were statistically significantly prolonged in the pancuronium, atracurium and alcuronium groups, but not in the other groups, when compared with the values after thiopental. In the absence of atropine, no statistically significant prolongation of the QT interval occurred. After intubation in the absence of atropine, the values were statistically significantly prolonged in the alcuronium, pancuronium, vecuronium and atracurium groups and in the presence of atropine in the atracurium group when compared with the preceding values. The QT intervals were prolonged only in relation to the increased heart rate. At 6.5 min, the values in all groups were decreased to about the same level as before intubation. The mean control values of the heart rate were between 80 and 90 b.p.m. in the atropine-treated groups and between 70 and 80 b.p.m. in the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)