Desflurane potentiates atracurium in humans: a comparative study with isoflurane

STUDY OBJECTIVE

(1) To evaluate the neuromuscular effects of desflurane and its interactions with atracurium and (2) to compare desflurane and isoflurane in these effects.

DESIGN

Sequential entry of informed and consenting patients randomly assigned to receive desflurane (n = 25) or isoflurane (n = 25).

SETTING

Operating suite of a county-university medical center.

PATIENTS

Fifty adults, ASA physical status I, undergoing elective orthopedic surgery.

INTERVENTIONS

Following establishment of steady desflurane or isoflurane anesthesia, at 1.25 minimum alveolar concentration (MAC) exhaled for 15 minutes, a randomly predetermined dose of atracurium (0.05, 0.1, or 0.15 mg/kg) was injected intravenously (IV). At the end of surgery, neostigmine 0.04 mg/kg IV was given to reverse the residual block. The neuromuscular effects of desflurane or isoflurane alone, and the dose-response relationship, time course, and reversibility of the neuromuscular effects of atracurium with either anesthetic, were examined in detail and compared using electromyographic quantification of the response of the first dorsal interosseous muscle to train-of-four (TOF) stimulation of the ulnar nerve.

MEASUREMENTS AND MAIN RESULTS

TOF fade and depression of the first response (T1) of the TOF were measured in response to desflurane or isoflurane, atracurium, and neostigmine. Desflurane caused more TOF fade than isoflurane prior to atracurium administration. The TOF ratios were 0.91 +/- 0.02 and 0.98 +/- 0.01, respectively (p < 0.05). For other measured neuromuscular parameters, atracurium-induced depression tended to be greater in the presence of desflurane than in the presence of isoflurane, but none of the measured differences reached the statistical significance level of p < 0.05. The ED50, ED95, and 25-75% recovery index of atracurium were 0.038 mg/kg (95% confidence level; range 0.030 to 0.047 mg/kg), 0.11 mg/kg (0.095 to 0.14 mg/kg), and 31 +/- 4 minutes (means +/- SEM) with desflurane anesthesia, versus 0.043 mg/kg (0.035 to 0.052 mg/kg), 0.13 mg/kg (0.11 to 0.16 mg/kg), and 23 +/- 4 minutes with isoflurane anesthesia (p = 0.1-0.2). Continuation of either anesthetic at 1.25 MAC prevented complete recovery of neuromuscular functions spontaneously or following neostigmine 0.04 mg/kg.

CONCLUSION

In ASA physical status I adults, 9% desflurane has neuromuscular effects equal to or slightly in excess of those of 1.6% isoflurane.

Recovery of cognitive functions after anaesthesia with desflurane or isoflurane and nitrous oxide

We studied recovery in 25 adult patients, ASA I, undergoing elective orthopaedic procedures after anaesthesia with 0.65 MAC desflurane (n = 16) or isoflurane (n = 9) with 60% nitrous oxide in oxygen. Early emergence from anaesthesia was assessed in the operating room by measuring time to spontaneous movement, cough, response to painful pinch, tracheal extubation, opening of the eyes and stating correct age, name and body parts. The return of cognitive functions in the late recovery phase was assessed in the post-anaesthesia care unit (PACU) by post-anaesthesia recovery scores (PARS), the Trieger dot test (TDT), and the digit substitution test (DST). In the early recovery phase, time to tracheal extubation, opening eyes, telling correct name, age and body parts occurred significantly faster in the desflurane group than in the isoflurane group (P < 0.05). The mean "triple orientation" time (to name, age, body parts) was 10.9 (SEM 0.9) min for desflurane, compared with 18.6 (2.5) min for isoflurane (P < 0.01). In the late recovery phase, desflurane patients had significantly greater PARS, more correct responses to the DST and fewer error responses to the TDT. Recovery times were not increased by increased duration of desflurane anaesthesia. The desflurane patients showed no delirium, minimal sedation and less shivering during the entire postoperative course. We conclude that desflurane anaesthesia was superior to isoflurane anaesthesia, not only in emergence, but also in the recovery of cognitive functions.

Neuromuscular blocking effect and placental gradient of pipecuronium bromide in elective caesarean section

We studied the suitability of pipecuronium for maintenance of neuromuscular block during 20 elective Caesarean sections under light general anaesthesia with a rapid-sequence technique facilitated by i.v. suxamethonium 0.6-0.8 mg kg-1. An initial dose of 0.035 mg kg-1 or 0.05 mg kg-1 of pipecuronium provided satisfactory relaxation of similar speed of onset (3.1 +/- 0.3 vs 3.8 +/- 0.6 min, p = 0.25); however the higher dose had a significantly longer duration of action than the lower dose (from injection to recovery to 20% of baseline 13.1 +/- 1.8 vs 39.3 +/- 6.9 min, p < 0.05). A spontaneous recovery of the T1 twitch of the train-of-four to 25% of baseline (residual block 75%) assured rapid antagonism of the residual block with either edrophonium 0.5 mg kg-1 or neostigmine 0.04 mg kg-1. A residual block greater than 80% depression of T1 markedly prolonged the time taken to achieve a satisfactory reversal. Pipecuronium had negligible cardiovascular effects and placental transfer. It had no observable effect on the newborn. In spite of some advantages, we conclude that pipecuronium is a suitable alternative during Caesarean section only when used judiciously in small doses for maintenance of neuromuscular block and recommend that the initial dose be no greater than 0.035 mg kg-1.

Modification by ketamine on the neuromuscular actions of magnesium, vecuronium, pancuronium and alpha-bungarotoxin in the primate

The neuromuscular effects of ketamine, at cumulative doses of 2.5 and 10 mg.kg-1 iv, were studied by electromyographically quantifying the thumb response evoked by ulnar nerve stimulation in 25 monkeys anaesthetized with pentobarbital-N2O-O2. Ketamine alone at these doses had no neuromuscular effects. When the EMG response was maintained at 50% of control by a continuous infusion of magnesium, vecuronium, or pancuronium, ketamine depressed the responses by an additional 13 +/- 3%, 34 +/- 7% and 32.5 +/- 3.3% (mean +/- SEM), respectively, at the highest dose, P less than 0.05. In contrast, ketamine had no effect on the neuromuscular block produced by incremental doses of alpha-bungarotoxin. These results indicate that ketamine does not act on the postjunctional acetylcholine receptor. It plays a secondary role in neuromuscular block, possibly by prejunctional or postjunctional effects independent of receptor occupation.

[The antinociceptive effect of intrathecal somatostatin in monkeys]

The distribution of somatostatin (SST) throughout the nervous system suggests that this tetradecapeptide may play a physiological role in CNS in the mediation of analgesia. The present study was undertaken to evaluate the antinociceptive properties of intrathecal (IT) injection of SST in the comparison of morphine sulfate (MS) in a primate model. The study was conducted after institutional approval and adhered to the regulations of the animal research committee. Seven adult monkeys (Maccaca cyclopis Swinhoe) weighing 4-6 kg were used. In each animal a L5 laminectomy window was created to facilitate IT injection. No neurological damage from surgery was noted. With the monkey standing in a specially constructed cage, all animals randomly received the following agents at one-week interval: (1) MS 1 mg, IT; (2) SST 50 micrograms, IT; (3) SST 250 micrograms, IT; and (4) SST 250 micrograms, IT + intramuscular (IM) naloxone 400 micrograms. The measured withdrawal latency (HPWL) was converted to the maximal percentage effect (MPE %) for comparison. The HPWL was measured at predrug and 5, 15, 30, 45, 60, 90 and 120 min after injection. Venous blood sample was obtained every 15 min to determine the plasma SST level by radioimmunoassay (RIA) technique in group 3 only. The results showed that MS (1 mg, IT) produced potent antinociception (MPE 100%) for more than 2 h. Intrathecal SST 50 micrograms, however, induced mild antinociception (MPE 43%) for only a short period and a 5-fold larger dose (250 micrograms) did not significantly change the nociceptive threshold with MPE only up to 47%.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracavernosal metaraminol for treatment of intraoperative penile erection

Four patients developed penile erection when regional anaesthesia was induced with spinal block. In another patient, penile erection developed during fentanyl-induced general anaesthesia. Injection of metaraminol into corpus cavernosum successfully achieved detumescence in all these patients. The dose of metaraminol ranged from 10 to 25 micrograms, much less than that required for the treatment of vasodilator-induced priapism. Intracavernosal injection of metaraminol is a simple, effective and safe method for immediate relief of intraoperative penile erection. It is most useful when urogenital operation would be delayed by penile tumescence.

Rectal ketamine versus intranasal ketamine as premedicant in children

The effects of ketamine administered per nasus (PN) or per rectum (PR) as pre-anesthetic medication for day surgery was studied in 70 ASA class I children with age ranging from 6 months to 6 years. Before study they were divided into 3 groups. Group A (n = 25) received no premedicant, while group B (n = 25) and group C (n = 20) received ketamine 6 mg/kg PR and 3 mg/kg PN as premedicant respectively. It was demonstrated that patients in group B and group C accepted the facemask during induction of anesthesia more willingly and peacefully than those in group A. In group B and group C there was accompaniment of analgesic effect seen postoperatively. The incidence of adverse reactions (nausea, vomiting, laryngospasm, salivation, respiratory depression) was low following the use of PR or PN ketamine although the children in these two groups emerged more belatedly from anesthesia and stayed in the post-anesthetic recovery room (PARR) for a longer time than in group A.

Sacroepidural analgesia for post-operative pain relief in children

For evaluation of the practicality of epidural analgesia for alleviation of post-operative pain, 66 class I or II patients with age ranging from 6 months to 12 years undergoing elective surgical procedures below the lower abdomen were enrolled for study during the period from January to April 1989. Before termination of general anesthesia a single dose of 0.25% bupivacaine, respectively at 0.25 mL/kg (Ideal body weight), 0.5 mL/kg, 0.75 mL/kg, 1.0 mL/kg and 1.25 mL/kg was given sacroepidurally to 5 groups of patients. Our results showed that for surgery below the lower abdomen a dose at 1.0 mL/kg was sufficient to suffice the need for relief of post-operative pain. At this dosage it achieved a neural block up to T8-T6 and provided with an analgesia that could last 6.0 +/- 2.1 hours. During the entire course there were no untoward effects such as hypotension, bradycardia, vomiting and shivering to come about. Therefore, sacroepidural analgesia with 0.25% bupivacaine at fitting single dose is safe and feasible in children as far as relief of post-operative pain for procedures below the lower abdomen is concerned.

Ketamine enhances phase I and phase II neuromuscular block of succinylcholine

The effect of intravenous injection of ketamine 2, 5 and 10 mg.kg-1 on the neuromuscular blocking action of succinylcholine was studied on the indirectly stimulated adductor pollicis muscle twitch of monkeys anaesthetized with 0.5-1.0 per cent halothane in oxygen. Neuromuscular block was quantified by single twitches evoked at 0.1 Hz. The changing nature of neuromuscular block from Phase I to Phase II was monitored periodically by train-of-four fade. In the absence of succinylcholine, ketamine had no consistent neuromuscular effect of its own. In the presence of succinylcholine, ketamine in a dose-dependent manner potentiated both the Phase I and the Phase II neuromuscular blocking effect of succinylcholine. In Phase I, 2 mg.kg-1 of ketamine reduced the ED50 of succinylcholine from 0.46 +/- 0.07 mg.kg-1 to 0.33 +/- 0.06 mg.kg-1 (P less than 0.01), and increased its 25-75 per cent recovery index from 4.0 +/- 0.4 min to 5.3 +/- 0.1 min (P less than 0.01). In Phase II, ketamine in the same dose deepened a steady neuromuscular block maintained by succinylcholine infusion from 48 +/- 3 per cent block to 71 +/- 2 per cent block (P less than 0.01). We concluded that ketamine potentiates the Phase I and the Phase II neuromuscular blocks of succinylcholine.

Ketamine potentiates nondepolarizing neuromuscular relaxants in a primate

Ketamine has many neuromuscular effects in vitro. Its neuromuscular effects in vivo have been controversial and inconsistent. To systematically examine its neuromuscular effects over a wide dose range and its interaction with all popular nondepolarizing neuromuscular relaxants, the effects of ketamine 2, 5, and 10 mg/kg IV were studied on a continuous but incomplete (50%) neuromuscular block preestablished by an IV infusion of d-tubocurarine, atracurium, vecuronium, and pancuronium. Indirectly stimulated adductor pollicis muscle response of monkeys anesthetized with 0.5-1.0% halothane in oxygen were quantified. Ketamine in the absence of a neuromuscular relaxant had no effect on the thumb twitch. In a dose-dependent manner, ketamine significantly enhanced the 50% depression of the thumb twitch preestablished by a constant IV infusion of each of the four muscle relaxants studied. Ketamine 2 mg/kg potentiated the neuromuscular relaxants in the following order of magnitude: vecuronium greater than atracurium greater than d-tubocurarine greater than pancuronium. However, with a 10 mg/kg dose of ketamine, pancuronium became as potentiated as was vecuronium, i.e., pancuronium = vecuronium greater than atracurium greater than d-tubocurarine. It is concluded that in the primate, ketamine potentiates all nondepolarizing muscle relaxants in a dose-dependent manner.