Muscle relaxants: a clinical update

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - The doses of neuromuscular blocking agents must be chosen in such a way as to allow enough spontaneous recovery to occur...     

Anaphylaxis to muscle relaxants: an audit of ten years of allergy testing at the Royal Adelaide Hospital

We audited patients with anaphylaxis to muscle relaxants during anaesthesia referred to the Department of Anaesthesia at the Royal Adelaide Hospital between the start of 2000 and the end of 2009. Of the 220 patients tested during this period, 43 had a positive intradermal test to the muscle relaxant given during their anaesthetic. The majority of these were to rocuronium and suxamethonium. Where rocuronium was the index agent, 65% of patients cross-reacted with another relaxant and 29% of patients with suxamethonium as their index agent demonstrated cross-reaction with another relaxant.     

Minimally invasive parathyroidectomy: an audit of a change in clinical practice

BACKGROUND: Minimally invasive parathyroidectomy (MIP) for primary hyperparathyroidism is gaining acceptance as a useful tool in the armamentarium of the endocrine surgeon. METHODS: We undertook an audit of 154 consecutive cases of parathyroidectomy carried out through bilateral neck exploration as well as a minimally invasive approach. RESULTS: Bilateral neck exploration had a 100% single operation cure rate. MIP had a 90% cure rate. Sestamibi localization had a positive predictive value of 99% for identifying an abnormal parathyroid gland. However, it performed poorly in the presence of multiglandular disease, resulting in these patients being at risk of having persistent hyperparathyroidism and therefore requiring a second operation. CONCLUSION: Our results with bilateral neck exploration are favourable compared with other large series. However, we have reported a 10% reoperation rate with MIP. Although not ideal, we are confident that, as a result of improvements based on this audit and with increasing experience, the cure rate will improve to reach international benchmarks. As such we feel that this strategy is a pragmatic way to offer MIP to patients in our region.     

Comparison of muscle relaxants in clinical use.

A prospective clinical comparison of d-tubocurarine, alcuronium, gallamine and pancuronium was performed in 400 surgical patients. Various parameters usually followed during clinical anaesthesia were recorded from the beginning of, to the recovery from anaesthesia. Endotracheal intubation was performed with or without suxamethonium. Intubation was always possible in 1-3 min when different muscle relaxants were used in the following initial doses: d-tubocurarine 0.4 mg/kg, alcuronium 0.3 mg/kg, gallamine 1.8 mg/kg, and suxamethonium 0.8 mg/kg. However, there was a statistically significant inferiority of the d-tubocurarine and gallamine groups. The use of suxamethonium seemed to shorten the duration of the initial dose of the nondepolarising agents and also to increase especially the dose of gallamine when calculated as mg/kg/h. It should be mentioned that the non-depolarising agents were given soon after suxamethonium without waiting for the return of spontaneous respiration. Pancuronium and alcuronium caused least changes in the cardiovascular parameters. Erythematous skin reactions were seen mostly after the use of d-tubocurarine and suxamethonium. This could depend on histamine liberating potency of these muscle relaxants.     

Assessment of the menisci and cruciate ligaments: an audit of clinical practice

The reliability of clinical assessment of the knee was evaluated in 203 patients using magnetic resonance imaging (MRI). Neither the mechanism of injury nor clinical symptoms were useful indicators of the type of pathology. Physical signs proved insufficiently sensitive in detecting abnormalities. Overall, the accuracy of clinical diagnosis was 80.8 per cent for the anterior cruciate ligament, 62.9 per cent for the medial meniscus and 74.9 per cent for the lateral meniscus. Accurate investigations allow arthroscopy to be targeted to those likely to obtain therapeutic benefit. Reliance upon clinical judgement alone would have resulted in an 89 per cent increase in arthroscopic procedures. Investigations such as MRI or arthrography are concluded to be cost-effective methods of avoiding unnecessary hospitalization, morbidity and waste of limited resources.     

Combined use of non-depolarizing muscle relaxants in clinical anesthesiology

Clinical observations in 99 patients and 74 experiments in cats enabled the authors to suggest that nondepolarizing myorelaxants when used in combination affected different portions of cholinergic receptors of the end plate of motor nerves causing greater inhibition of neuromuscular transmission. So an associated simultaneous application of such myorelaxants as tubocurarine and tercuronium as well as tercuronium and Arduan in special sub-blocking doses gives a complete relaxation of skeletal muscles without side effects which allows such methods to be recommended in surgical practice for anesthetic maintenance of operations on high risk patients.     

Muscle relaxants: past,present and future

Muscle relaxants are an irreplaceable item within the modern surgical toolkit. Their almost universal use during surgical procedures of medium-to-long duration means that it is essential that all anaesthetists must have a comprehensive knowledge of their history and the future prospects for their continued evolution. In the context of identifying the ‘ideal’ muscle relaxant, this review focuses on those areas of muscle relaxant action that are either highly desirable or highly undesirable—and discusses the extent to which any identified problems have, or have not, been overcome with the existing range of clinically available muscle relaxant compounds. Pharmacodynamic topics covered include the actions of muscle relaxants on the range of different subtypes of nicotinic acetylcholine receptors, the actions of muscle relaxants on motor nerve terminals and the major non-neuromuscular actions of muscle relaxants. From a pharmacokinetic perspective, how the pharmacological and chemical properties of muscle relaxants influence the clinical properties and uses of the compounds are discussed.     

Muscle relaxants: the classical receptor theory.

According to the classical receptor occupancy theory non-depolarizing and depolarizing muscle relaxants differ in one respect: both types of drugs possess affinity for the cholinergic receptor at the neuro-muscular function, but only the depolarizing relaxants show efficacy. The two properties, affinity and efficacy are independent from each other.