Suxamethonium infusion rate and observed fasciculations. A dose-response study

Intravenous rocuronium 0.3 mg/kg improves the conditions for tracheal intubation in cats: a randomized, placebo-controlled trial

OBJECTIVES

We evaluated the use of rocuronium 0.3 mg/kg intravenously (IV) to facilitate tracheal intubation in cats anesthetized for elective ovariohysterectomy.

METHODS

Thirty female cats were randomly allocated to receive rocuronium 0.3 mg/kg IV or an equal volume of normal saline, following induction of anesthesia with ketamine and midazolam. Thirty seconds after induction, a single investigator, unaware of treatment allocation, attempted tracheal intubation. The number of attempts and the time to complete intubation were measured. Intubating conditions were assessed as acceptable or unacceptable based on a composite score consisting of five different components. Duration of apnea after induction was measured and cases of hemoglobin desaturation (SpO2 <90%) were identified.

RESULTS

Intubation was completed faster (rocuronium 12 s [range 8-75 s]; saline 60 s [range 9-120 s]) and with fewer attempts (rocuronium 1 [range 1-2]; saline 2 [range 1-3], both P = 0.006) in cats receiving rocuronium. Unacceptable intubating conditions on the first attempt occurred in 3/15 cats with rocuronium and in 10/15 with saline ( P = 0.01). Apnea lasted 4 ± 1.6 mins with rocuronium and 2.3 ± 0.5 mins with saline ( P = 0.0007). No cases of desaturation were observed.

CONCLUSIONS AND RELEVANCE

Rocuronium 0.3 mg/kg IV improves intubating conditions compared with saline, and reduces the time and number of attempts to intubate with only a short period of apnea in cats.

Rapid-sequence intubation of head trauma patients: prevention of fasciculations with pancuronium versus minidose succinylcholine

INTRODUCTION

Fasciculations during rapid-sequence intubation may lead to increased intracranial pressure and emesis with aspiration. Standard rapid-sequence intubation requires a nondepolarizing blocking agent before succinylcholine administration.

HYPOTHESIS

Prevention of fasciculations during rapid-sequence intubation of head trauma patients can be accomplished as safely and effectively with minidose succinylcholine as with a defasciculating dose of pancuronium.

DESIGN

A prospective, randomized, double-blind study.

SETTING

An inner-city county trauma center with 70,000 patient visits per year.

PARTICIPANTS

Sequential adult head trauma patients requiring rapid-sequence intubation who had no contraindications to succinylcholine or pancuronium.

INTERVENTIONS

Each head trauma patient requiring rapid-sequence intubation who met the inclusion criteria received standard rapid-sequence intubation maneuvers and lidocaine (1 mg/kg) IV. Patients were randomized to receive either minidose succinylcholine (0.1 mg/kg) or pancuronium (0.03 mg/kg) IV one minute prior to the full paralytic dose of succinylcholine (1.5 mg/kg) IV. Fasciculations were recorded using a graded visual scale.

RESULTS

Of 46 patients, eight of 19 (42%) in the pancuronium group and six of 27 (22%) in the succinylcholine group experienced fasciculations. No statistically significant difference in fasciculations was detected between the two groups using chi 2 analysis. Complete relaxation of the cords was present in all but two patients, one in each group. No patient in either group experienced emesis or significant dysrhythmias.

CONCLUSION

Pretreatment with minidose succinylcholine causes no greater incidence of fasciculations than pancuronium in rapid-sequence intubation of head trauma patients in an ED setting. Thus succinylcholine may be used as the sole paralytic agent in rapid-sequence intubation of head trauma patients.

Clinical pharmacology of the neuromuscular blocking agents

Neuromuscular blocking agents are among the most commonly used drugs during general anesthesia. They compete with acetylcholine and interfere with the transmission of nerve impulses resulting in skeletal muscle relaxation. Based on their mechanism of action, neuromuscular blocking agents are classified as either depolarizing or nondepolarizing. Succinylcholine is a short-acting depolarizing agent. Commonly used nondepolarizing agents are curare (long-acting), pancuronium (long-acting), atracurium (intermediate-acting), and vecuronium (intermediate-acting). Neuromuscular blocking agents are used clinically to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery. This article provides an overview of the physiology of the neuromuscular transmission and summarizes our current knowledge on the use of these agents during general anesthesia.

Suxamethonium--the relation between dose and response

In a study which involved 120 adult patients, the ED95 of suxamethonium was shown to be 0.51 mg/kg, using an electromyographic technique. Marked individual variation in response was noted, for example a dose of 0.3 mg/kg produced a range of blockade from 4%-90%. Body surface area was shown to be more significantly related to blockade than lean body mass or total body weight.

Alfentanil as an adjuvant of balanced anaesthesia for tonsillectomy in adults

In a double-blind study, 80 adult patients, undergoing tonsillectomy, were randomly allocated to one of the four groups: d-tubocurarine (d-Tc) 50 micrograms/kg+alfentanil (Alf) 20 micrograms/kg, d-Tc 50 micrograms/kg+Alf 50 micrograms/kg, Alf 10 micrograms/kg+Alf 20 micrograms/kg, Alf 10 micrograms/kg+Alf 50 micrograms/kg. The first drug was given 2 min before thiopental and the second drug 1 min before inserting the mouth gag. Intubation was facilitated with suxamethonium. Anaesthesia was maintained with 70% nitrous oxide in oxygen and peripheral muscle relaxation during operation with vecuronium. For analysis of the induction characteristics, both d-Tc-pretreatment groups were treated together and compared with the results of the Alf-pretreatment groups. Muscle fasciculations occurred in 20% in the d-Tc group and in 70% in the Alf group. Neither d-tubocurarine nor alfentanil prevented the cardiovascular intubation response. Cardiovascular responses to the placement of the mouth gag occurred only in the lower-dose alfentanil groups. ECG changes during operation occurred in 25-45% of the patients. The most common ECG change was junctional rhythm. The operating conditions were good in 65-80% of the patients. The mean recovery score (0-10) ranged from 9.3 to 9.7 between the groups. The incidence of nausea ranged from 20-30% and that of vomiting from 10-25% between the groups. Bleeding from the operation site occurred in 20-30% of the patients. None of the patients needed sutures to stop the bleeding.

The influence of thiopentone and alfathesin on succinylcholine-induced fasciculations and myalgias

Thiopentone doses corresponding to 5.238 mg x kg-1, that is 2UD95 (UD95:unconsciousness dose 95) inhibit the intensity of succinylcholine-induced fasciculations compared with UD95. Alfathesin doses corresponding to 0.570 mg x kg-1, also 2UD95 (calculated as alphaxalone at a concentration of 9 mg/ml in alfathesin), do not have any greater effect on the degree of fasciculations compared to UD95. Furthermore, neither induction agent influences the incidence, distribution and duration of succinylcholine-induced myalgias. The inhibition of the degree of fasciculations caused by thiopentone is believed to be a consequence of a postsynaptic depressant effect of thiopentone at the neuromuscular junction. The evaluation of the degree of succinylcholine-induced fasciculations must take into consideration the dose of thiopentone administered at induction of anaesthesia.