Mivacurium-induced neuromuscular blockade following single bolus doses and with continuous infusion during either balanced or enflurane anesthesia

Mivacurium chloride (BW B1090U) was administered to 72 patients during their elective surgery. The eight groups (nine subjects per cell) in the 2 x 2 x 2 study design differed in three factors: the size of the mivacurium bolus dose administered, whether or not this dose was followed by an infusion of mivacurium, and in the technique used for the maintenance of anesthesia. Four groups received a single bolus dose of mivacurium, 0.15 mg/kg, and the remaining four groups received mivacurium, 0.25 mg/kg, administered iv in 15 s. Precisely 2 min later, tracheal intubation was attempted. Conditions were judged to be good or excellent on most occasions, but intubation was not possible for two of the patients in the low-dose and one in the high-dose groups. Four groups, two at each bolus dose, received no additional mivacurium: there was a dose-dependent decrease in the rate of spontaneous recovery following the bolus dose. The other subdivision of groups was the use of either barbiturate-nitrous oxide-narcotic (balanced) anesthesia, or enflurane-nitrous oxide anesthesia; the anesthetic technique did not affect the pattern of spontaneous recovery from either bolus dose. Four groups, again two at each bolus dose, subsequently received an infusion of mivacurium, adjusted to depress the twitch response by approximately 95%. Infusion rates averaged 6.0 micrograms.kg-1.min-1 in the groups receiving balanced anesthesia and 4.2 micrograms.kg-1.min-1 for those receiving enflurane anesthesia. Recovery following administration by infusion was slower than that observed following a bolus dose of mivacurium, 0.15 mg/kg but did not differ between the anesthetic groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-response relationships of doxacurium chloride in humans during anesthesia with nitrous oxide and fentanyl, enflurane, isoflurane, or halothane

In a two-part study, the dose-response relationships of doxacurium chloride (BW A938U) were evaluated during general anesthesia maintained with commonly used anesthetic techniques. In part 1, cumulative dose-response methodology was used to establish the ED95 of doxacurium in 36 patients receiving 70% nitrous oxide and fentanyl, or 50% nitrous oxide and either 1.26% enflurane, 0.84% isoflurane, or 0.57% halothane anesthesia. Mechanomyographic response to train-of-four stimulation was used to monitor neuromuscular blockade. The peak effect of doxacurium following each 5 micrograms/kg incremental dose was noted and a log-probit dose-response curve was constructed for each individual patient. The median ED50s were 11 micrograms/kg, 6 micrograms/kg, 8 micrograms/kg, and 8 micrograms/kg for patients receiving fentanyl, enflurane, isoflurane, or halothane anesthesia, respectively. The median ED95s were 24 micrograms/kg, 14 micrograms/kg, 16 micrograms/kg, and 19 micrograms/kg for patients receiving fentanyl, enflurane, isoflurane, and halothane anesthesia, respectively. In part 2, 72 additional patients received a rapid single injection of the ED95 (n = 36) or 2 X ED95 (n = 36) of doxacurium appropriate for the administered anesthetic as estimated from part one of the study. Peak effects of the ED95 given as single injections correlated well with the results in part 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of vecuronium administered by bolus and infusion during halothane or balanced anesthesia

Vecuronium was administered to two patient groups as a single intravenous dose, 60 micrograms/kg, combined with an infusion, 1 microgram/min/kg. Anesthesia was maintained for the first group with a halothane-nitrous oxide technique; the second group received fentanyl-barbiturate-tranquilizer-nitrous oxide. As the infusion ended, plasma vecuronium concentrations were 0.34 (+/- 0.10) microgram/ml for the halothane group and 0.32 (+/- 0.07) microgram/ml for the fentanyl group, associated with 93% (+/- 8) and 88% (+/- 10) twitch depression, respectively. Vecuronium plasma concentration-time data were combined with the simultaneous intensities of neuromuscular blockade to model the kinetic-dynamic values for each patient. For the halothane group the steady-state volume was 0.21 (+/- 0.04) L/kg, the clearance was 2.9 (+/- 0.1) ml/min/kg, and the elimination half-life was 100 (+/- 36) minutes; for the fentanyl group these were 0.20 (+/- 0.08) L/kg, 3.2 (+/- 0.1) ml/min/kg, and 84 (+/- 43) minutes, respectively. Plasma concentrations associated with 50% blockade averaged 0.2 microgram/ml for both groups. Neither the pharmacokinetics nor the pharmacodynamics of vecuronium in humans differed between these two patient groups.

Ketorolac tromethamine as compared with morphine sulfate for treatment of postoperative pain

Ketorolac tromethamine, a nonnarcotic, prostaglandin synthesis-inhibiting analgesic, was compared with morphine sulfate for relief of moderate to severe postoperative pain. The 155 patient participants received single intramuscular doses of either ketorolac, 10, 30, or 90 mg, or morphine, 6 or 12 mg, administered in a double-blind, randomized fashion. Pain scores (verbal and visual analog) were recorded at baseline and assessed at 30 minutes and then hourly to 6 hours. Pain relief was rated at the same times. Ketorolac, 90 and 30 mg, was rated significantly better than morphine, 6 mg, at each assessment interval after 1 hour. Ketorolac, 90 and 30 mg, was rated similarly to morphine, 12 mg, for the first 3 hours and better than morphine, 12 mg, 4 hours after injection. There were no serious side effects reported. The only side effect reported in more than 3% of patients was 8% somnolence with morphine. This study shows ketorolac to be a safe and effective analgesic for relief of postoperative pain.

Dose-finding and pharmacokinetic study of intramuscular midazolam

Ten healthy male volunteers received intramuscular (IM) doses of 0.050, 0.075, and 0.100 mg/kg midazolam hydrochloride or its vehicle (placebo) in a double-blind manner until a dose producing adequate preanesthetic sedation was administered. Level of sedation, degree of impairment of psychomotor function, existence of antegrade amnesia, and incidence of side effects were evaluated after each dose. An adequate level of sedation (awake/drowsy or asleep/easily responds to verbal command for at least one hour after drug administration) was produced, beginning shortly after drug administration, in eight of the volunteers by 0.075 mg/kg; the dose producing the same effect (the optimal dose) was 0.050 mg/kg for the oldest volunteer, and the other volunteer required 0.100 mg/kg. Sedation lasted no more than four hours after administration of the optimal dose. The optimal dose in each volunteer produced an impairment of psychomotor function that lasted no more than six hours and antegrade amnesia that lasted no more than two hours. Mild erythema at the injection site occurred infrequently. The pharmacokinetic variables describing the absorption and disposition of midazolam were determined in five of the volunteers. Pharmacokinetic studies indicated that midazolam hydrochloride is absorbed rapidly from IM injection sites; this consistent with the observation of a rapid onset of sedation. The relatively high elimination clearance of midazolam after IM administration is similar to that reported after intravenous administration. The results of this study suggest that midazolam hydrochloride 0.075 mg/kg IM provides sedation and amnesia that is satisfactory for preanesthetic medication but does not last too long into the recovery period.

Comparison of visual and measured train-of-four recovery after vecuronium-induced neuromuscular blockade using two anaesthetic techniques

This study evaluated train-of-four recovery after the administration of vecuronium, comparing measured with visually observed responses. Responses to supramaximal stimuli of the ulnar nerves were measured by a force transducer, and compared with visually observed movements of the contralateral thumb. For the 10 patients anaesthetized with nitrous oxide and enflurane, the second, third and fourth twitches visually reappeared at 84 (+/- 10)%, 76 (+/- 11)%, and 70 (+/- 12)% measured blockade, respectively. For the other 10 patients, anaesthetized with a narcotic-barbiturate technique, the second, third and fourth twitches reappeared at 81 (+/- 8)%, 68 (+/- 9)%, and 59 (+/- 11)%. These results were not different for the two anaesthetic techniques.

Reappearance of the train-of-four after neuromuscular blockade induced with tubocurarine, vecuronium or atracurium

The characteristics of train-of-four recovery after atracurium or vecuronium were studied, under enflurane anaesthesia, and compared with those associated with tubocurarine-induced blockade. Ten patients each received vecuronium 0.1 mg kg-1, atracurium 0.5 mg kg-1 or tubocurarine 0.5 mg kg-1. Neuromuscular blockade was calculated as the percent depression of the first twitch, and was determined at the time of reappearance of the second, third and fourth twitches of the train-of-four. The pattern during recovery from blockade induced by the three neuromuscular blocking agents was similar, with T2, T3 and T4 reappearing at approximately 93%, 89% and 86% residual blockade, respectively. These results are different from those previously reported by Lee (1975) indicating that, under enflurane anaesthesia, the train-of-four count may give an incorrect estimate of the degree of neuromuscular blockade.

Midazolam: pharmacology and uses

Midazolam is an imidazobenzodiazepine with unique properties when compared with other benzodiazepines. It is water soluble in its acid formulation but is highly lipid soluble in vivo. Midazolam also has a relatively rapid onset of action and high metabolic clearance when compared with other benzodiazepines. The drug produces reliable hypnosis, amnesia, and antianxiety effects when administered orally, intramuscularly, or intravenously. There are many uses for midazolam in the perioperative period including premedication, anesthesia induction and maintenance, and sedation for diagnostic and therapeutic procedures. Midazolam is preferable to diazepam in many clinical situations because of its rapid, nonpainful induction and lack of venous irritation. Compared with thiopental, midazolam is not as rapid acting nor predictable in hypnotic effect. It will not replace thiopental as an induction agent. Advantages of midazolam over thiopental are those of the more versatile pharmacologic properties of a benzodiazepine compared with a barbiturate such as amnestic and anxiolytic properties. Midazolam should be a useful addition to the formulary.

Effects of etomidate on hormonal responses to surgical stress

The hormonal responses to surgical stress were examined in 10 patients scheduled for elective gynecologic laparotomy. Anesthesia was induced with either thiopental, 4 mg/kg, or etomidate, 0.35 mg/kg, and maintained with nitrous oxide and enflurane. Plasma cortisol, aldosterone, ACTH, and catecholamines were measured during the 24 h after the induction of anesthesia. The catecholamine responses of the patients whose anesthesia was induced with either drug were similar. The plasma ACTH concentrations for the etomidate group were greater than baseline values and the concentrations in the thiopental group (P less than 0.05) in the fourth and fifth hours. In the patients receiving thiopental, both cortisol and aldosterone concentrations were greater than the baseline value (P less than 0.05) in the second to fourth hours after induction. In the etomidate group, the plasma concentrations of cortisol were less than baseline values (P less than 0.05) in the first and second hours after induction of anesthesia and both cortisol and aldosterone were lower than those in the thiopental group (P less than 0.05) in the half to fourth hours after induction. These results confirm an earlier report of the suppression of cortisol after etomidate administration and, because aldosterone also was suppressed, suggests that etomidate exerts its effect by inhibiting early stages of steroidogenesis in the adrenal cortex.

[Double-blind testing of alfentanyl and fentanyl in total intravenous anesthesia]

Fentanyl or alfentanil (at a dose ten times that of fentanyl) was administered to fifty healthy patients undergoing elective surgery. They were given in a double-blind manner for analgesia in a total intravenous anaesthesia technique to see if differences existed in their respiratory depressant, analgesic or sedative effects. They were combined in the same syringe with etomidate and given by intravenous bolus injection followed by a continuous intravenous infusion. Analgesia was generally adequate for the operations in this study. Respiratory depression (respiratory rate less than ten) lasted about ten minutes after drug administration, ceased in all patients. The return of respiratory rate, consciousness, and psychomotor performance to control was similar in the groups receiving fentanyl or alfentanil. This study showed that alfentanil and fentanyl have equivalent potency and duration of action when used in a ten to one ratio. Furthermore, the technique provided good operating conditions but there was a high incidence of postoperative drowsiness, nausea and vomiting.

Placental transfer of midazolam and its metabolite 1-hydroxymethylmidazolam in the pregnant ewe

Plasma concentrations of midazolam and its metabolites were measured in maternal and fetal blood after intravenous administration of 90 mg of midazolam to seven pregnant ewes in whom sampling catheters had been chronically implanted. Midazolam and its metabolite 1-hydroxymethylmidazolam crossed the placenta of the pregnant ewe. The fetal/maternal plasma concentration ratio of midazolam and the metabolite was 0.15. The distribution and elimination half-lives of midazolam and the metabolite were identical in both maternal and fetal circulations. The major compound found in the urine was the metabolite 1-hydroxymethylmidazolam glucuronide.

Neuromuscular recovery after laparoscopy

Vecuronium bromide, 0.045 mg X kg-1, was compared with pancuronium, 0.07 mg X kg-1, when used to provide muscle relaxation for tracheal intubation and abdominal relaxation for outpatient gynecologic laparoscopy. Both drugs provided adequate intubating conditions within 5 min and satisfactory abdominal relaxation. Because spontaneous recovery from vecuronium was more rapid, either with inhalational or nitrous oxide-narcotic techniques, pharmacological reversal with edrophonium and atropine was either not necessary or more easily accomplished after vecuronium, as shown by the train-of-four. All patients receiving pancuronium required reversal of the blockade, and in a few patients reversal was difficult. Tests of muscle power and coordination performed 30 and 60 min postoperatively showed no difference between the drugs. There were no postoperative complications related to muscle relaxants and all patients met our discharge criteria the day of surgery. Given the conditions observed at the end of the procedure, we would choose vecuronium for muscular relaxation in laparoscopic surgery.

High-performance liquid chromatographic assay for etomidate in human plasma: results of preliminary clinical studies using etomidate for hypnosis in total intravenous anesthesia

A sensitive and specific high-performance liquid chromatographic assay was developed for the measurement of etomidate in human plasma following extraction of the drug and the internal standard. Using 0.5-ml aliquots of plasma, the assay was linear in the concentration range of 20-2000 ng of etomidate/ml of plasma. This method was used to evaluate a preliminary clinical study of an etomidate infusion regimen for hypnosis in a total intravenous anesthesia protocol in 23 patients. The average duration of the infusion was 30 min, and awakening and alertness occurred 20 and 36 min after the termination of the infusion, respectively, at the respective plasma concentrations of 297 and 214 ng/ml. These results and this assay will be used to design and evaluate an improved etomidate infusion regimen.

Pharmacokinetics of the infusion of alfentanil in man

The pharmacokinetics of alfentanil under the conditions of an empirically derived 1-h continuous infusion of 3 micrograms kg-1 min-1, with a bolus of 80 micrograms kg-1, both i.v., were determined in five patients. The distribution half-life (mean +/- SD) (7.4 +/- 3.1 min), elimination half-life (86.7 +/- 15.8 min), apparent volume of distribution, Varea (0.44 +/- 0.15 litre kg-1) and elimination clearance (3.33 +/- 0.75 ml kg-1 min-1) were similar to those previously reported for a single bolus of alfentanil. These values for apparent volume of distribution and clearance can be used to calculate correct bolus and infusion doses to maintain any desired steady state plasma concentration using standard formulae: for example, to maintain a steady state plasma concentration of 400 ng ml-1, a bolus dose of 176 micrograms kg-1 and an infusion of 1.3 micrograms kg-1 min1 would be required.

Midazolam kinetics in women of two age groups

Midazolam kinetics were determined in 11 younger (22 to 30 yr) and 11 older (50 to 60 yr) women to determine age-related differences in the kinetics of this water-soluble benzodiazepine. Midazolam, 0.2 mg/kg, was injected intravenously over 30 sec for induction of anesthesia that was maintained with 67% nitrous oxide in oxygen and intravenous fentanyl doses. There were no differences between the groups with respect to awakening times or plasma concentrations. Midazolam kinetics were described by a three-compartment open mamillary model. The only differences were small increases in the slow and total volumes of distribution in the older women. The kinetics we determined, including the steady-state volume of distribution of 1.23 l/kg and the elimination clearance of 419 ml/min, are in excellent agreement with those reported by others. Our data suggest that midazolam has advantages over other benzodiazepines, not only because of its water solubility and shorter elimination t1/2, but also because of little change in its kinetics with age.

Some effects of diisopropyl phenol (ICI 35 868) on the pharmacodynamics of atracurium and vecuronium in anaesthetized man

The effects of a bolus injection of diisopropyl phenol 2 mg kg-1 i.v. and an infusion (150 micrograms kg-1 min-1 for 30 min and 75 micrograms kg-1 min-1 thereafter) on the pharmacodynamics and dose-response curves of atracurium and vecuronium were studied in 52 healthy (ASA I or II) patients. Under anaesthesia with diisopropyl phenol, the cumulative dose-response curves of both myoneural blocking drugs were shifted to the left when compared with previously reported results. However, there was no clinically significant change in the pharmacodynamics of either drug after the bolus injection of the blocking drug. Diisopropyl phenol 2 mg kg-1 i.v. administered during steady-state infusions of vecuronium and atracurium increased the depth of the constant neuromuscular blockade. When diisopropyl phenol alone was given to four patients there was no change in the twitch height. These results show that diisopropyl phenol, given according to the regimen in this study, potentiates both of the neuromuscular blockers studied but does not prolong the duration of action of either drug. During the infusion of diisopropyl phenol, vecuronium was found to be five times more potent, to have a more rapid onset time, and to be shorter acting than an equipotent dose of atracurium.

A pharmacokinetically designed etomidate infusion regimen for hypnosis

An etomidate infusion regimen for hypnosis as part of balanced, totally intravenous anesthesia was designed to maintain plasma etomidate concentrations above the awakening concentration of 300 ng/ml while avoiding dose-related side effects. The etomidate infusion regimen of 0.1 mg/kg/min for 3 min, 0.02 mg/kg/min for 27 min, and 0.01 mg/kg/min for the remainder of the anesthesia was used together with intravenous bolus doses of fentanyl, droperidol, and pancuronium. This was evaluated in 11 patients and the kinetics of etomidate were reexamined. The anesthetic technique seemed clinically satisfactory for the infusion periods of 30-109 min. The average time and plasma concentration at the end of the infusion was 59.5 min and 583 ng/ml, at awakening was 9.3 min and 307 ng/ml, and at alertness was 19.5 min and 227 ng/ml. The main difference between the kinetics observed in the present study and those of previous studies is in the elimination clearance. The average plasma elimination clearance of the present study was 1210 ml/min and the whole-blood clearance was estimated to be 1357 ml/min, giving an apparent hepatic extraction ratio of approximately 0.90. The negative correlation of patient mass and elimination clearance normalized for body mass suggests that the terminal infusion should not be adjusted to body mass.

Intradermal histamine release by 3 muscle relaxants

The induration and redness caused by intradermal injections of equipotent doses of atracurium, vecuronium and d-tubocurarine were measured in six healthy, male volunteers. Atracurium and d-tubocurarine were almost indistinguishable in their reactions. Vecuronium caused a significantly smaller response than both atracurium and d-tubocurarine. We therefore suggest that of these three drugs, vecuronium may cause the least histamine release and is, perhaps, the drug of choice in patients with a history of asthma or allergy.

Interactions of diisopropyl phenol (ICI 35868) with suxamethonium, vecuronium and pancuronium in vitro

In vitro studies were performed using the rat phrenic nerve-hemidiaphragm preparation to investigate possible interactions between diisopropyl phenol and its solvent, cremophor, with three neuromuscular blocking drugs. Cumulative concentration curves were constructed for the neuromuscular blockers and linear regression analyses performed. Differences in the calculated effective concentration to produce a 50% decrease in twitch height (EC50) and slope showed that diisopropyl phenol potentiated the action of suxamethonium, vecuronium (Org NC 45) and pancuronium. Cremophor potentiated the action of suxamethonium but antagonized the action of the non-depolarizing neuromuscular blockers. The possible mechanisms of action are discussed.

Intramuscularly administered ciramadol for management of postoperative pain: a comparative study

Efficacy and safety of the analgesic ciramadol in the management of postoperative pain was evaluated in 139 healthy patients given single, double-blind, intramuscular injections of either 30 mg ciramadol, 60 mg ciramadol, 10 mg morphine or 0.9% saline on the first or second postoperative day. Differences in pain intensity and relief of pain, changes from baseline on a pain analog scale, percentage of patients with moderate or greater pain relief, and cumulative treatment failures were measured for 6 hours after injection. Morphine proved to be superior to all other treatments. Neither dose of ciramadol could be statistically differentiated from placebo. During the first hour after administration, some measurements showed that 30 mg ciramadol was superior to 60 mg ciramadol. Patients experienced little or no drowsiness in any of the four groups, and other side effects were transient and required no specific therapy. Some patients experienced an acute increase in pain intensity after administration of 60 mg ciramadol; this possibly represents antagonism of the residual effect of the previous narcotic. This study must be interpreted with the knowledge that ciramadol, an agonist-antagonist analgesic, was administered to patients who had been receiving narcotic analgesics before entering the study. Future studies of ciramadol given as the sole analgesic may more clearly define its efficacy in the management of postoperative pain.