R. K. Mirakhur

Comparison of rocuronium and suxamethonium for use during rapid sequence induction of anaesthesia

This study was designed to compare the tracheal intubating conditions during a rapid sequence induction of anaesthesia using rocuronium 0.6 (n = 61) or 1.0 mg.kg−1 (n = 130) or suxamethonium 1.0 mg.kg−1 (n = 127) as the neuromuscular blocking drugs. Anaesthesia was induced with fentanyl 1–2 μg.kg−1 and thiopentone 5 mg.kg−1 (median dose) and intubating conditions were assessed 60 s after the administration of the neuromuscular blocking drug by an observer unaware of which drug had been given. Intubating conditions were graded on a three‐point scale as excellent, good or poor, the first two being considered clinically acceptable. The study was carried out in two parts. At the end of the first part a comparison between the two doses of rocuronium was carried out when at least 50 patients had been enrolled in each group. The results showed the intubating conditions to be significantly superior with the 1.0 mg.kg−1 dose of rocuronium (p < 0.01). Final comparison between the 1.0 mg.kg−1 doses of rocuronium and suxamethonium showed no significant difference in the incidence of acceptable intubations (96 and 97%, respectively). The incidence of excellent grade of intubations was, however, significantly higher with suxamethonium (80% vs. 65%; p = 0.02). It is concluded that rocuronium 1.0 mg.kg−1 can be used as an alternative to suxamethonium 1.0 mg.kg−1 as part of a rapid sequence induction provided there is no anticipated difficulty in intubation. The clinical duration of this dose of rocuronium is, however, 50–60 min.

Prevention of nausea and vomiting after day case gynaecological laparoscopy. A comparison of ondansetron, droperidol, metoclopramide and placebo.

We have compared the efficacy of ondansetron, metoclopramide, droperidol and placebo in the prevention of postoperative nausea and vomiting in 118 day stay patients undergoing laparoscopic gynaecological procedures. All received a standardised general anaesthetic offentanyl, propofol, nitrous oxide in oxygen and isoflurane. Three to five min before induction of anaesthesia, patients were allocated to receive ondansetron 4mg, metoclopramide 10 mg, droperidol 1 mg or placebo in a randomised, double‐blind manner. Visual analogue scores for nausea, the incidence of emetic episodes, and analgesic and antiemetic consumption were recorded for 48 h postoperatively. The scores for nausea were significantly lower in the ondansetron group (p < 0.01) compared with the other three groups at 1, 2 and 4h after operation; thereafter there was no difference. The incidence of erne sis was lower (p = 0.063) and time to first oral fluids was shorter (p < 0.05) in the ondansetron group. Oral analgesic requirements were significantly greater in the ondansetron group over the 48 h study period. Two patients, one each in the placebo and metoclopramide groups, had to remain in hospital overnight because of persistent emetic symptoms.

Reversal of rocuronium-induced neuromuscular block with sugammadex is faster than reversal of cisatracurium-induced block with neostigmine

BACKGROUND Reversal of the residual effect of rocuronium or cisatracurium by neostigmine may be slow and associated with side-effects. This randomized, safety-assessor-blinded study compared the efficacy of sugammadex, a selective relaxant binding agent for reversal of rocuronium-induced neuromuscular block, with that of neostigmine for reversal of cisatracurium-induced neuromuscular block. The safety of sugammadex and neostigmine was also evaluated. METHODS Adult surgical patients (ASA class I-III) were randomized to sugammadex 2.0 mg kg(-1) for reversal of block induced by rocuronium 0.6 mg kg(-1), or neostigmine 50 microg kg(-1) for reversal of block induced by cisatracurium 0.15 mg kg(-1). Anaesthesia was induced and maintained using i.v. propofol and remifentanil, fentanyl, or sufentanil. Neuromuscular function was monitored using acceleromyography (TOF-Watch SX). Sugammadex or neostigmine was administered at reappearance of T(2). The primary efficacy variable was time for recovery of the train-of-four (TOF) ratio to 0.9. RESULTS Eighty-four patients were randomized, 73 of whom received sugammadex (n=34) or neostigmine (n=39). Time from start of administration of reversal agent to recovery of the TOF ratio to 0.9 was 4.7 times faster with sugammadex than with neostigmine (geometric mean=1.9 vs 9.0 min, P<0.0001). Reversal of block was sustained in all patients. There were no serious adverse effects from either reversal agent and no significant changes in any measure of safety, except for similar elevations in urinary N-acetyl glucosaminidase in both groups. CONCLUSIONS Sugammadex 2.0 mg kg(-1) administered at reappearance of T(2) was significantly faster in reversing rocuronium-induced blockade than neostigmine was in reversing cisatracurium-induced block.

The TOF-Guard neuromuscular transmission monitor.: A comparison with the Myograph 2000

The TOF‐Guard neuromuscular monitor uses an accelerometer to measure the response to nerve stimulation. In this study, we have compared it to a standard mechanomyographic monitor, the Myograph 2000, for neuromuscular monitoring in 28 subjects. A train‐of‐four mode of stimulation was used in both cases. The times taken for onset of block, and for the recovery of T1 (the first response in the train of four) to 25% of control, the time from recovery of T1 from 25–75% and for the recovery of the train of four ratio to 0.7 were compared with the two monitors. There was a good correlation between the two devices for both onset and recovery times. However, differences were highlighted when the data were analysed by the method of Bland and Altman. The 95% limits of agreement for the T1 recovery to 25%, as measured by the TOF‐Guard, ranged from 5 min less to 8 min more than when measured by the Myograph 2000. For recovery of the train of four ratio to 0.7, the limits of agreement were approximately 6 min in either direction. The 95% limits for the TOF‐Guard measured train of four ratio were from 0.47 to 0.99, at the Myograph reading of 0.7. We recommend that information from the TOF‐Guard and the Myograph 2000 should not be used interchangeably. However, the TOF‐Guard is likely to improve considerably on tactile evaluation of the responses to stimulation.

Intrathecal diamorphine for analgesia after Caesarean section : A dose finding study and assessment of side-effects

Eighty women undergoing elective Caesarean section under spinal anaesthesia using hyperbaric bupivacaine 0.5% were randomly allocated to receive, in addition, intrathecal diamorphine 0.125, 0.25 or 0.375 mg or saline. Postoperative morphine requirements, measured using a patient‐controlled analgesia system, were reduced in a dose‐dependent manner by diamorphine. Pain scores were significantly lower at 2 and 6 h following the two larger doses of diamorphine. Less supplemental analgesia was required intra‐operatively if intrathecal diamorphine had been given. The incidences of vomiting and pruritus were also dose‐related. No respiratory rates of less than 14 breath.min−1 were recorded and the incidence of oxygen saturation readings less than 95% and 90% did not differ between groups. There were no adverse neonatal effects. Intrathecal diamorphine in the present study was found to be safe in doses of up to 0.375 mg following Caesarean section. However, minor side‐effects were frequently observed.

A comparison of the stress response to laryngoscopy. The Macintosh versus the McCoy blade.

The cardiovascular changes and catecholamine concentrations were compared in 20 patients before and after laryngoscopy with either the Macintosh or the McCoy laryngoscope blades. Following induction with fentanyl and thiopentone and muscle relaxation with vecuronium the vocal cords were visualised for 10 s with either the Macintosh or McCoy blade, chosen at random. Heart rate, arterial blood pressure and plasma noradrenaline and adrenaline concentrations were measured before, and at, laryngoscopy, and 1, 3 and 5 min later. There was a significant increase in both heart rate (33%) and arterial blood pressure (27%) after laryngoscopy using the Macintosh blade (p < 0.01). Use of the McCoy blade did not result in any significant change in either heart rate or arterial blood pressure. There was a slight increase (p > 0.05) in plasma noradrenaline concentrations using the Macintosh blade which persisted for 5 min after laryngoscopy. This was not observed with the McCoy blade. There was no change in plasma adrenaline concentrations with either blade during the 5 min after laryngoscopy when compared to the values before laryngoscopy. It is concluded that the stress response to laryngoscopy is less marked with the use of the McCoy blade and is probably due to a reduction in the force necessary to obtain a clear view of the larynx.

Neuromuscular effects of rocuronium bromide (Org 9426) during fentanyl and halothane anaesthesia

The neuromuscular effects of intravenous rocuronium bromide, 0.6 mg.kg−1 or 0.9 mg.kg−1, were studied in four groups of 10 patients during anaesthesia with or without halothane (0.5–0.75% inspired concentration). Neuromuscular block was monitored using mechanomyography and train‐of‐four stimulation. The mean times to onset of complete neuromuscular block were 58 and 59 s using the 0.6 mg.kg−1 dose in patients anaesthetised with fentanyl and halothane respectively. The times of 34 min and 33 min for 25% recovery of T1 (first response in the train of four), 54 min and 52 min for 90% recovery of T1, 55 min and 60 min for a train of four ratio of 0.7, and 13 and 13 min respectively for the recovery index (25–75% recovery of T1) were not significantly different in these groups. Complete block with the 0.9 mg.kg−1 dose occurred in 47 s and 44 s respectively in the fentanyl and halothane groups. T1 recovered to 25% in 51 min and 58 min, and to 90% in 77 min and 86 min respectively in the two groups. The recovery indices and the times to spontaneous recovery of the train of four ratio to 0.7 were 17 min and 19 min, and 83 min and 93 min respectively. All the parameters were significantly different between the 0.6 mg.kg−1 and 0.9 mg.kg−1 doses. Halothane in the concentrations used did not influence the neuromuscular effects. It is concluded that rocuronium is a rapidly acting non‐depolarising muscle relaxant with a duration of action similar to that of vecuronium and may be a useful alternative to suxamethonium for rapid tracheal intubation.

Muscle pains and biochemical changes following suxamethonium administration after six pretreatment regimens

The incidence of muscle pains and changes in serum concentrations of potassium, calcium and creatine kinase following suxamethonium were investigated after no pretreatment or pretreatment with intravenous tubocurarine 0.05 mg.kg−1, intravenous chlorpromazine 0.1 mg.kg−1, alphatocopherol (vitamin E) 600 mg in three divided doses orally, aspirin 600 mg orally or intravenous calcium chloride 5 mg.kg−1 in groups of 20 patients each. The incidence of myalgia was reduced significantly by tubocurarine, chlorpromazine and alphatocopherol. However, the increase in creatine kinase was attenuated only in the groups of patients who received tubocurarine and chlorpromazine. The changes in serum potassium and calcium concentrations were within acceptable limits. The intubating conditions were not as good in the patients who received tubocurarine as in the other groups. Effectiveness of chlorpromazine in preventing both the myalgia and the biochemical changes suggests the involvement of phospholipases in the pathogenesis of suxamethonium‐induced muscle damage.

A comparison of different pre-oxygenation techniques in the elderly.

The efficacy of five different techniques of pre‐oxygenation before a modified rapid intubation sequence was assessed, using oxygen saturation measurement, in patients aged over 65 years. Twenty patients in each group were pre‐oxygenated using four deep breaths or normal tidal breathing for 1, 2, 3, or 4 minutes. The acceptable period of apnoea was defined as the time taken to desaturate to 93%. The mean times (SD) taken to reach this end‐point were 3.7 (1.6), 4.1 (1.2), 5.4 (1.7), 5.4 (1.4) and 5.2 (1.7) minutes respectively. The apnoea times with 2, 3 and 4 minutes pre‐oxygenation were not significantly different from each other but were significantly longer than after four deep breaths and 1 minute. It is concluded that a pre‐oxygenation period of at least 2 minutes should be employed in the elderly before a rapid sequence induction.

Neuromuscular effects and intubating conditions following mivacurium: a comparison with suxamethonium

Mivacurium chloride has been assessed in respect of intubating conditions and neuromuscular effects. The influence of suxamethonium on the onset and duration of subsequently administered mivacurium was also studied. A dose of 0.15 mg.kg−1 of mivacurium was found to provide unacceptable intubating conditions at 2 min in 9/9 patients and further studies were conducted using 0.2 mg.kg−1. Intubating conditions with this dose were acceptable in 65% and 80% of patients at 2 min and 2.5 min respectively. In comparison, intubating conditions were acceptable in 100% of patients at 1 min following 1 mg.kg−1 of suxamethonium. The onset of block occurred in 96 s and 97 s after 0.15 mg.kg−1 and 0.2 mg.kg−1 respectively, and the durations of block in terms of recovery of the first twitch (T1) to 25% and 90% of control, and to recovery of train‐of‐four ratio to 0.7, were 16.1 and 17.9; 24.1 and 25.8; and 24.2 and 27.0 min respectively with the two doses. The time for the onset of complete block with suxamethonium 1.0 mg.kg−1 was 50 s and the times to 25% and 90% recovery were 9.8 min and 13.3 min. The differences between suxamethonium and both doses of mivacurium were significant (p < 0.05) but there were no significant differences between the two doses of mivacurium in any of the neuromuscular measurements. Prior administration of suxamethonium had no influence on the effects of mivacurium. Cutaneous flushing was observed in 30 out of 75 patients but this was associated with transient hypotension in only two patients. Our results show mivacurium to have a duration of action approximately half that of comparable doses of the intermediate acting relaxants atracurium and vecuronium.