L. Saarnivaara

Tracheal intubation without the use of muscle relaxants: remifentanil or alfentanil in combination with propofol

Background: Alfentanil‐propofol combination provides adequate conditions for tracheal intubation without neuromuscular blocking drugs in most patients. Providing an option for intense opioid effect without compromising recovery after short operations, remifentanil might offer benefits over alfentanil, especially in ambulatory surgery. In this study intubating conditions after remifentanil‐propofol were compared to those after alfentanil‐propofol.

QT interval of the ECG, heart rate and arterial pressure using propofol, methohexital or midazolam for induction of anaesthesia

The effects of propofol 2 mg/kg, methohexital 2 mg/kg or midazolam 0.3 mg/kg were studied on the QT interval of the ECG corrected by the heart rate (QTc), heart rate and arterial pressure during induction of anaesthesia in 87 ASA class I‐(II)‐patients. The patients were randomly allocated to one of the three anaesthetic groups. The incidence of the patients with a prolonged QTc interval (= more than 440 ms) ranged from 29 to 41% between the groups. In each group these patients were treated separately. After all anaesthetics, the QTc interval was significantly prolonged in the patients with a normal control QTc interval, whereas in the patients with a prolonged control QTc interval, it tended to be shortened both after propofol and methohexital and it was significantly shortened after midazolam. After injection of suxamethonium, no significant QTc interval changes occurred in the patients with a normal control QTc interval in either the propofol or the methohexital groups, whereas in the patients with a prolonged control QTc interval treated with propofol the QTc interval decreased significantly 60 s after suxamethonium when compared with the corresponding preceding values. The mean values in the propofol group in the patients with a normal control QTc interval were always below the upper limit of the normal range. In the patients with a normal control QTc interval treated with midazolam, the QTc interval was significantly prolonged 60 s after suxamethonium and after intubation and in the patients with a prolonged control QTc interval treated with midazolam the QTc interval was significantly decreased after midazolam and increased 30 s after suxamethonium when compared with the corresponding preceding values. Only after methohexital did the heart rate increase significantly. A cardiovascular intubation response occurred in all groups. The incidence of ECG changes ranged from 0 to 17% between the groups. There was no correlation between the incidence of ECG changes and prolongation of the QTc interval. On the basis of the present results, in the patients with a normal control QTc interval propofol and methohexital are superior to midazolam in situations in which prolongation of the QTc interval should be avoided. On the other hand, in the patients with a prolonged control QTc interval, midazolam is superior or at least equal to the other drugs. Due to a considerable increase of the heart rate, methohexital is inferior to propofol and midazolam.

Attenuation of the Cardiovascular Intubation Response with N2O, Halothane or Enflurane

The circulatory intubation response was studied in 75 normotensive, otolaryngological patients after a thiopentone‐suxamethonium induction followed by 2 min artificial ventilation with 100% oxygen (control), 70% nitrous oxide in oxygen (N2O), halothane 2% with N2O, enflurane 3% with N2O or enflurane 5% in oxygen. The above study groups (n = 15) were chosen after preliminary experiments performed in 25 different patients with halothane 2% (n = 8) or enflurane 3% (n = 6) in oxygen, which did not prevent the increase of arterial pressure after intubation, or with halothane 3% (n = 11) which attenuated the pressor response but caused cardiac arrhythmias in 55% of patients. Enflurane 5% in oxygen attenuated the increase of systolic arterial pressure by 53%, enflurane 3% with N2O by 34% and halothane 2% with N2O by 31 %. The increase in heart rate after intubation was lowest in the halothane 2% with N2O group, but there were no statistically significant differences between the groups. Cardiac arrhythmias were commonest in the enflurane 3% with N2O group (20%) and they did not occur in the halothane 2% with N2O group. Considering the total effect on arterial pressure, heart rate and rate‐pressure product, we recommend the combination of halothane 2% with N2O.

Effects of four anticholinesterase-anticholinergic combinations and tracheal extubation on QTc interval of the ECG, heart rate and arterial pressure

Background: Imbalance in cardiac sympathetic tone causes prolongation of the QTc interval of the ECG. On the other hand, impairment of the parasympathetic control of the heart rate caused by anticholinesterase‐anticholinergic combinations might also affect the cardiac sympathetic tone and hence the QTc interval of the ECG. The main purpose of the present study was to compare the effects of four anticholinesterase‐anticholinergic combinations used for the antagonism of the neuromuscular block on the QTc interval of the ECG, heart rate and arterial pressure.

Modification of the haemodynamic responses to induction of anaesthesia and tracheal intubation with alfentanil, esmolol and their combination

The purpose of this double-blind randomized work was to study the effect of alfentanil and esmolol and their half-dose combination on the increases of heart rate and arterial pressure and on the prolongation of the QTc interval of the ECG occurring during anaesthetic induction. Sixty ASA class I– II patients with mean age ranging from 26 to 32 yr among the groups. Patients were allocated to one of four equal groups to receive saline, esmolol 2 mg · kg− 1, alfentanil 0.03 mg · kg− 1 and alfentanil 0.015 mg · kg− 1 + esmolol 1 mg · kg− 1. Anaesthesia was induced with thiopentone. Succinylcholine was used to facilitate tracheal intubation. Haemodynamic variables were measured non-invasively and the QTc interval with the aid of a microcomputer. Comparisons between the groups were performed using two-way analysis of variance with repeated measures. Both alfentanil and alfentanil-esmolol prevented the increase of heart rate and arterial pressure caused by intubation whereas esmolol prevented only the increase of the heart rate. None of the treatments prevented prolongation of the QTc interval after intubation and only alfentanil prevented that after succinylcholine. The present results suggest that in the prevention of the haemodynamic responses to tracheal intubation, the half-dose combination of alfentanil and esmolol is as effective as alfentanil and superior to esmolol. The combination is preferable to relatively large doses of either drug in circumstances where side effects, such as respiratory depression due to alfentanil or bradycardia due to both drugs should be minimized.RésuméCe travail randomisé en double-aveugle avail pour but l’étude des effets de l’association de l’alfentanil avec l’esmolol à demidoses sur l’augmentation de la fréquence cardiaque et de la pression artérielle, et sur la prolongation de l’intervalle QTc de l’ECG pendant l’induction de l’anesthésie. Soixante patients ASA I et II dont la moyenne d’âge variait entre 25 et 32 ans ont fait partie de l’étude. Ces patients ont été répartis en quatre groupes pour recevoir respectivement: du soluté physiologique, de l’esmolol 2 mg · kg− 1, de l’alfentanil 0,03 mg · kg− 1, et de l’alfentanil 0,015 mg · kg− 1 + esmolol 1 mg · kg− 1. L’anesthésie a été induite au thiopentone. La succinylcholine a été utilisée pour l’intubation. Les paramètres hémodynamiques ont été enregistrés par voie non effractive et l’intervalle QTc grâce à un microordinateur. Les comparaisons ont été établies sur des mesures répétées par analyse de variance. L’alfentanil et l’alfentanil + esmolol ont empêché l’augmentation de la fréquence cardiaque et de la pression artérielle causée par l’intubation alors que l’esmolol n’a été efficace sur l’augmentation de la fréquence cardiaque. Aucun des traitements n’a été efficace pour la prévention de la prolongation de l’intervalle QTc après l’intubation et seul l’alfentanil l’a été après la succinylcholine. Ces résultats suggèrent que pour prévenir les effets hémodynamiques de l’intubation, une demidose d’esmolol avec alfentanil est aussi efficace que l’alfentanil et supérieure à l’esmolol. Cette association est préférable à des doses relativement plus fortes de chacune des drogues dans les circonstances au cours desquelles les effets secondaires comme la dépression respiratoire due à l’alfentanil ou la bradycardie due awe deux drogues doivent être réduites au minimum.

QT interval of the ECG, heart rate and arterial pressure during anaesthetic induction : comparative effects of alfentanil and esmolol

In a double‐blind study the effect of esmolol and alfentanil on the QT interval of the ECG corrected by the heart rate (QTc), heart rate and arterial pressure during anaesthetic induction was studied in 59 oxycodone‐ and atropine‐premedicated ASA class I‐(II) patients with a mean age of 26 yr (range 15–50 yr). The patients were randomly allocated to one of the four groups: saline, esmolol 2 mg · kg‐1, esmolol 3 mg · kg‐1 or alfentanil 0.03 mg·kg‐1. Both doses of esmolol prevented the prolongation of the QTc interval after thiopental and suxamethonium, but not after laryngoscopy and intubation. Alfentanil prevented the prolongation of the QTc interval following thiopental, suxamethonium and laryngoscopy but not after intubation. Esmolol did not prevent the increase in the heart rate and arterial pressure in response to laryngoscopy and intubation. No cardiovascular responses to laryngoscopy and intubation occurred in the patients treated with alfentanil. No cardiac arrhythmias occurred in the esmolol 3 mg·kg‐1 group, whereas the frequency of ventricular ectopic beats was 40% in the saline group and 13–20% m the other groups.

Comparison of Adrenaline and Phenylephrine in Out-of-Hospital Cardiopulmonary Resuscitation: A Double-Blind Study

Phenylephrine, a strong alpha‐adrenergic receptor‐stimulating agent, was compared with adrenaline in 65 patients with out‐of‐hospital cardiac arrest, in a double‐blind study. The resuscitation was performed by the physician‐staffed Prehospital Emergency Care Unit of Helsinki University Central Hospital. The patients received either 1.0 mg of phenylephrine or 0.5 mg of adrenaline i. v. in the treatment of fine ventricular fibrillation, asystole or electromechanical dissociation. If two doses of either drug did not restore circulation, 0.5 mg of known 0.01% adrenaline was given i. v., maximally twice. In the adrenaline group, which consisted of 36 patients with a mean age of 61 years, 10 patients (28%) were successfully resuscitated. The phenylephrine group consisted of 29 patients with a mean age of 62 years. In this group nine patients (31%) were successfully resuscitated. The two groups were comparable regarding their apnoea‐times, and there was no difference in the need for extra adrenaline between the groups. No adverse effects, such as hypertension or bradycardia, were noted in the patients treated with either adrenaline or phenylephrine, nor did the overall rate of successful resuscitation fall during the test period. It is concluded that phenylephrine seems as effective as adrenaline in the treatment of cardiac arrest, but further studies seem warranted.

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 (<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. Before laryngoscopy, neither heart rate nor arterial pressure changed significantly in any of the groups. In all groups, a cardiovascular intubation response occurred. The incidence of cardiac arrhythmias ranged from 19% to 22% in the atracurium, pancuronium and vecuronium groups and from 0% to 3% in the other groups. Atropine did not affect the incidence of arrhythmias.

Haemodynamic responses and prolongation of QT interval of ECG after suxamethonium‐facilitated intubation during anaesthetic induction in children: a dose‐related attenuation by alfentanil

The haemodynamic response to endotracheal intubation and changes in the QT interval of ECG during anaesthetic induction were studied in 68 healthy children (5.5 years). The children were pretreated double‐blindly with either alfentanil 10 μg/kg (A10), 25 μg/kg (A25), 50 μg/kg (A50) or saline (control) (17 children in each group) i.v. 1 min before thiopentone 5 mg/kg. The trachea was intubated after suxamethonium 1.5 mg/kg. Central nervous system excitation was seen in four of 17 and in one of 17 children after alfentanil 50 and 25 μg/kg, respectively. After intubation, heart rate increased significantly in the control group, remained at initial levels in the A10 and A25 groups and decreased in the A50 group. A pressor response to intubation was seen in the control and A10 groups. The QT interval was significantly prolonged after suxamethonium in the control and A10 groups, but remained at baseline levels in the A25 and A50 groups. Ventricular ectopic beats were only seen in 2/17 children in the control group. In conclusion, alfentanil 25 μg/kg is ideal for preventing the haemodynamic response to endotracheal intubation and prolongation of the QT interval, a sign of sympathoadrenal activation, before induction of intravenous anaesthesia in children.

Comparison of subhypnotic doses of thiopentone vs propofol on the incidence of postoperative nausea and vomiting following middle ear surgery

Background: Middle ear surgery is associated with a high incidence of emetic sequelae and propofol has been reported to have antiemetic activity in subhypnotic doses.