A comparison of the effect of rocuronium and vecuronium on heart rate during gynaecological laparoscopy

The effect on intra-operative heart rate of two nondepolarising muscle relaxants, rocuronium and vecuronium, was compared in 116 fit out-patients undergoing gynaecological laparoscopic procedures. Both groups received an anaesthetic technique which differed only in the choice of muscle relaxant. Intra-operatively it was noted that patients given rocuronium (20 mg) had significantly fewer episodes of bradycardia (heart rate < 50 beat.min-1) than patients given vecuronium 4 mg (p < 0.05). Profound bradycardias (heart rate < 30 beat.min-1) did not occur in any of the patients in the rocuronium study group, whereas 5% of patients receiving vecuronium had a period of transient asystole. We conclude that, at the doses stated, rocuronium results in significantly fewer episodes of bradycardia than vecuronium when used as a muscle relaxant for laparoscopic gynaecological procedures.     

Effects of precurarisation on suxamethonium induced postoperative myalgia during the first trimester of pregnancy

Two hundred and fifty women undergoing termination of pregnancy during the first trimester under general anaesthesia were studied to determine the effects of precurarisation on suxamethonium-induced postoperative myalgia and on the need for postoperative analgesics after suxamethonium. Either alcuronium (0.03 mg/kg), atracurium (0.04 mg/kg), tubocurarine (0.05 mg/kg), vecuronium (0.01 mg/kg) or saline was administered in a double-blind manner 4 min before giving suxamethonium. An additional 50 patients were studied who received isoflurane rather than precurarisation and suxamethonium. Every pretreatment prevented fasciculations better than did saline (P less than 0.001). In the saline group, 92% of patients had fasciculations and in the other groups this ranged from 8 to 32%, respectively. On the first postoperative day, 76% of the patients in the saline group had myalgia while myalgia was manifested in 28, 54 and 34% of patients given alcuronium, tubocurarine or vecuronium, respectively (P less than 0.05). Atracurium failed in this effect with 62% having myalgia. In the isoflurane group, none of the patients complained of myalgia on the first postoperative morning. The need for analgesics was less (P less than 0.005) in the isoflurane group (8%) and in the pretreatment groups (18-27%) than in the saline group (42%). It is concluded that precurarisation with tubocurarine, vecuronium or, most effectively, with alcuronium but not with atracurium decreases suxamethonium-induced postoperative myalgia and seems to be necessary also during the first trimester of pregnancy.     

Myalgia and biochemical changes following intermittent suxamethonium administration

One hundred gynaecological patients for laparoscopy divided into five groups were studied to determine the effects of a number of pretreatments on serum myoglobin, creatinine kinase and myalgia following intermittent suxamethonium administration. One group acted as controls, while the other groups were given intravenous pretreatments of alcuronium 2 mg, midazolam 0.15 mg/kg, lignocaine 1.5 mg/kg and suxamethonium 7 mg. Serum myoglobin was determined by radio-immunoassay. The mean increases in the control group were 167 micrograms/litre myoglobin at 20 minutes and 196 IU creatinine kinase at 24 hours; 13 out of 20 patients responded with a marked increase of serum myoglobin at 20 minutes and of creatinine kinase at 24 hours. Only alcuronium pretreatment prevented myoglobin increase at 20 minutes, abolished creatinine kinase increase at 24 hours and reduced 24-hour myalgia. The other pretreatments slightly reduced myoglobin increase at 20 minutes and 24-hour creatinine kinase but did not reduce myalgia. Only one patient in the whole study had markedly elevated serum myoglobin at 24 hours. We conclude that only non-depolarising relaxant pretreatment is effective in the reduction of some of the adverse effects of suxamethonium administration.     

Anaphylactoid reaction to vecuronium followed by systemic reaction to skin testing

An unusual case is presented of a systemic anaphylactoid reaction to tubocurarine and subsequently to vecuronium. Intradermal testing with vecuronium following the latter response was negative at recommended test dose levels but at a higher concentration it initiated a hazardous systemic response. The laboratory investigations and possible mechanisms involved in this unusual case are discussed in detail since they may relate to other patients who experience anaphylactoid responses to anaesthetic drugs and who then undergo intradermal testing.     

Comparison of high and low doses of suxamethonium

In a double-blind study, 67 young adult patients undergoing anaesthesia for dental extractions were allocated at random to receive either 0.5 mg/kg or 1.5 mg/kg suxamethonium. A greater increase in arterial pressure was seen following induction in the 1.5 mg/kg group, although overall intubating conditions were similar in the two groups. Suxamethonium-associated muscle pains were significantly more common in the group which received the larger dose (p less than 0.05).     

Bronchospasm following the use of vecuronium

A case history is presented which records bronchospasm due to vecuronium. Immunological investigations, including basophil degranulation tests, indicated that the bronchospasm was not caused by direct histamine release and was not IgE mediated. It was of interest that intradermal testing gave a positive wheal response against neuromuscular agents other than those involved in the anaesthetic procedure under investigation. A positive reaction to vecuronium was only obtained when given in a high concentration and accords with the general belief that vecuronium has extremely low potential for histamine release.     

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.     

Bradycardia in patients receiving atracurium or vecuronium in conditions of low vagal stimulation

Four groups of 20 patients each received either vecuronium or atracurium together with either glycopyrronium or saline, and underwent anaesthesia free of vagolytic drugs, and surgery devoid of vagal activity. Determinations of plasma histamine concentrations were made to examine the possible correlation between these levels and changes in heart rate and blood pressure as well as a possible relationship with skin reactions after the administration of the relaxants. Patients who received vecuronium without the anticholinergic drug, glycopyrronium, showed a greater tendency towards bradycardia (though not statistically significant) than those given atracurium. More cutaneous reactions were observed with patients who received atracurium than in those with vecuronium, but there was no correlation with plasma histamine concentrations of either relaxant group. There was no correlation either between histamine concentrations and heart rate or blood pressure associated with atracurium. The incidence of bradycardia with either relaxant is low if the anaesthetic technique and the surgery are devoid of vagal activity.     

Effect of milrinone on vecuronium-induced neuromuscular block

We examined the effect of milrinone, a phosphodiesterase III inhibitor, on neuromuscular block induced by vecuronium. Thirty adult patients were randomly assigned to one of two equal groups: the milrinone group and the control group. Subjects in the milrinone group received an intravenous loading dose of milrinone 5 microg x kg-1x min-1 for 10 min, followed by an infusion at a rate of 0.5 microg x kg-1x min-1. Subjects in the control group received normal saline at a rate of 0.1 ml x kg-1 x h-1. Thirty minutes after the beginning of the infusion of milrinone, anaesthesia was induced with intravenous thiopental 4 mg x kg-1 and fentanyl 2 microg x kg-1, and was maintained with isoflurane in oxygen and nitrous oxide. Neuromuscular blockade was monitored electromyographically at the adductor pollicis muscle. The times from the administration of vecuronium 0.1 mg.kg-1 to the onset of neuromuscular block and the return of the first, second, third, and fourth response of the train-of-four were compared between the two groups. Times to the recovery of the ratio of the first twitch to the control twitch to 25%, 50% and 75%, and times to the recovery of train-of-four ratio to 25%, 50% and 75% were also compared between the two groups. The onset of neuromuscular block in the milrinone group was significantly slower than in the control group. The times to the returns of the four twitches of the train-of-four, times to recovery of the ratio of the first twitch to the control twitch to 25% and 50%, and the times to the recovery of the train-of-four ratio to 25% and 50% were significantly shorter in the milrinone group than in the control group. We conclude that milrinone delays the onset of neuromuscular blockade but hastens its recovery in anaesthetised patients receiving vecuronium.     

Effect of vecuronium on atropine-induced changes in heart rate

The effect of vecuronium on the heart rate response to atropine has been studied by comparing dose-response relationships in two groups of patients who underwent extracorporeal shock wave lithotripsy. One group received vecuronium (0.1 mg/kg) and the other acted as control. Incremental doses of atropine (1.8, 1.8, 3.6, 7.2 and 14.4 micrograms/kg) were administered and changes in heart rate recorded. No significant differences were observed between the two groups following each incremental dose of atropine.     

Reversal of vecuronium with neostigmine in patients with diabetes mellitus

Reversal of vecuronium-induced neuromuscular blockade with neostigmine was compared in two groups of 16 subjects: patients with Type 2 diabetes mellitus and normal controls. When the first twitch of the train-of-four had returned to 25% of the control value, neostigmine 40 microg x kg(-1) and atropine 20 microg x kg(-1) were given to reverse the neuromuscular blockade. The train-of-four ratio was lower at 3 min, 6 min, 9 min, 12 min and 15 min after reversal in the diabetic group than in the control group but the differences did not reach statistical significance. Fifteen minutes after reversal, the number of patients in whom recovery from neuromuscular blockade was judged insufficient to guarantee good respiratory function (train-of-four ratio < 0.74) did not differ between the groups. However, 15 min after reversal, the number of patients with a train-of-four ratio < 0.9 was significantly higher in the Diabetic Group than in the Control Group (15 vs. 10, p = 0.033).     

Suxamethonium induced myalgia and the effect of pre-operative administration of oral aspirin

Eighty-four fit, unpremedicated patients who presented for routine surgery and received a standard anaesthetic technique were allocated randomly to three equal groups. Group 1 received tubocurarine 0.05 mg/kg before induction of anaesthesia. Group 2 received soluble aspirin 600 mg orally one hour before surgery, while Group 3 received no pretreatment. Aspirin prophylaxis produced a significant reduction in the incidence of subsequent suxamethonium-induced myalgia and the improvement was similar to that achieved with tubocurarine pretreatment. Pre-operative oral administration of aspirin effectively reduces muscle pains and avoids many of the complications associated with pretreatment with non-depolarising agents.     

Response to suxamethonium in a myasthenic patient during remission

A cumulative dose followed by an infusion was used to determine the dose response to suxamethonium in a patient with diagnosed myasthenia gravis who was in true remission (asymptomatic while receiving no therapy). The ED50 and ED90 values for suxamethonium were 0.08 mg/kg and 0.20 mg/kg, and an infusion rate of 3.2 mg/kg/hour was required to maintain a 90-95% depression of the single twitch response as monitored by integrated electromyography. These values are within the range for normal patients, and we conclude that myasthenic patients during a true remission may not demonstrate resistance to suxamethonium.     

Hypercholinesterasaemia and suxamethonium resistance

A case is reported of resistance to the muscle relaxing action of suxamethonium due to the rare inherited condition of hypercholinesterasaemia. Family studies suggest dominant inheritance. It is suggested the condition should be considered whenever there is unexpected resistance to the muscle relaxing action of suxamethonium.     

Duration of action of an equipotent dose of vecuronium in infants and in children

During general anaesthesia without any volatile anaesthetic agents, ten infants and ten children received incremental doses of vecuronium to achieve a 95% neuromuscular block. Thereafter, the thenar electromyographic response was allowed to recover spontaneously. Total dose of vecuronium to establish a 95.0 ± 0.5% (mean ± SEM) neuromuscular block was 66% greater for children than for infants (73 ± 4 vs. 44 ± 4 μg·kg^?1, P < 0.0001). However, recovery index and time to complete recovery of the neuromuscular function were 88 and 89% longer, respectively, in infants than in children (P < 0.0001). These results of the effect of an equipotent dose of vecuronium in infants and in children confirm that vecuronium is a long acting neuromuscular blocking agent in infants.