Laryngeal tube versus laryngeal mask airway in anaesthetised non-paralysed patientsA comparison of handling and postoperative morbidity

BACKGROUND: The purpose of this study was to compare the classical laryngeal mask airway (LMA) with the laryngeal tube (LT) in anaesthetised non-paralysed patients. PATIENTS AND METHODS: A total of 100 patients scheduled for minor elective surgery were included. After standardised induction and maintenance of anaesthesia with propofol and remifentanil, patients were randomly allocated to receive either a LMA or LT; muscle relaxants / relaxant were not applied. Selection of the appropriate size and the initial inflation volume were chosen according to the manufacturers instructions. Ease of insertion, initial intra-cuff pressure, oropharyngeal leak pressure at an intra-cuff pressure of 60 cm H(2)O and incidence and severity of complications during and after anaesthesia were compared. RESULTS: The LT was inserted significantly quicker than the LMA (35.1+/-15.9 s vs. 56.6+/-42.5 s; mean+/-SD). Insertion of the LT was successful within 1 attempt in 90% and within 2 or 3 attempts in another 4% of patients for the LT compared with 68% and 20% of patients for the LMA, respectively. For the LT the initial cuff pressure was significantly lower (75.1+/-16.2 cm H(2)O) and the oropharyngeal leak pressure after adjustment of the intra-cuff pressure to 60 cm H(2)O was significantly higher (27.2+/-6.9 mbar) compared with the LMA (109.5+/-25.7 cm H(2)O and 19.9+/-4.0 mbar, respectively). Incidence of postoperative laryngeal complications in the LT group (31%) was lower compared with the LMA group (54%). CONCLUSION: In anaesthetised non-paralysed patients the LT compares favourably to the LMA in terms of ease of insertion and postoperative morbidity.

Determination of interstitial rocuronium concentrations in the muscle tissue of anesthetized dogs by microdialysis.

INTRODUCTION: The objective was to establish and validate a microdialysis technique for the quantification of interstitial concentrations of the neuromuscular blocker, rocuronium, in the muscle tissue of dogs under steady-state conditions. METHODS: The standard and combined retrodialysis approaches were used for in vivo microdialysis probe calibration. After induction of anesthesia with pentobarbital (30 mg/kg), the left femoral vein was cannulated and blood drawn for protein binding determination. Microdialysis probes were inserted in the muscle and calibrated in vivo, using vecuronium as the calibrator. Each dog received a short 2-min infusion followed by a 120-min infusion of rocuronium via the right jugular vein and three microdialysis samples were collected at steady-state during a 2-h period. Samples were stored at -70 degrees C until HPLC analysis. RESULTS: Using combined retrodialysis, rocuronium unbound interstitial (C(ISFu)) and venous plasma (C(pssuv)) concentrations are in good agreement; with a ratio C(ISFu)/C(pssuv) of 100+/-11%. Using standard retrodialysis, this ratio was 47+/-7%. CONCLUSIONS: Combined retrodialysis is a more reliable and accurate technique for quantitative assessment of rocuronium interstitial concentrations especially for lengthy anesthetic procedures. These findings have potential implications, as drug concentrations in the site of action would be more relevant for concentration-effect relation of muscle relaxants.

An improvement in segregation of human butyrylcholinesterase phenotypes having the fluoride-resistant variants.

Correct recognition of butyrylcholinesterase (BChE; EC 3.1.1.8) variants in human serum is essential if patients susceptible to a prolonged reaction following treatment with short acting muscle relaxants, like suxamethonium, are to be reliably identified. The dimethylcarbamate Ro 02-0683 is used in standard procedures for identification of BChE variant by measuring residual activity after two hours of inhibition. Such a long inhibition time distinguishes well between the usual (U) and atypical (A), but less successfully the fluoride-resistant (F) variant. In this paper, inhibition rate constants were determined from the initial time course of inhibition of homozygous (FF) and heterozygous (UF and AF) BChE phenotypes by Ro 02-0683; 1.6 x 10(6), 2.7 x 10(6) and 6.2 x 10(6) dm3 mol-1 min-1 for AF, FF and UF, respectively. After only 30 min of inhibition the resolution between the phenotypes was even better than after two hours. Hence, determination of the residual activity after 30 min inhibition is recommended for the segregation of the suxamethonium sensitive fluoride-resistant variants.

Ryanodine receptors in peritoneal mast cells: possible role in the modulation of exocytotic activity.

Previous studies have shown that ryanodine in low concentrations and caffeine increase intracellular [Ca(2+)] in the absence of external Ca(2+), suggesting Ca(2+) release from intracellular stores through ryanodine receptors (RyR). In the present study we employed amperometry to examine the effect of RyR agonists and antagonists on serotonin release elicited with compound 48/80 (10 micro g/ml). Ryanodine (1 micro M) or, similarly, 20 mM caffeine, in the absence of external Ca(2+), enhanced the amperometric response to compound 48/80 and all the individual amperometric spike parameters. Ryanodine (50 micro M), dantrolene (20 micro M) and tetracaine (50 micro M), putative antagonists of the RyR, attenuated the amperometric response significantly, decreasing the number and frequency of events as well as their amplitude. This is the first demonstration that Ca(2+) availability from RyR-operated Ca(2+) sources may contribute to the modulation of secretory activity in mast cells, affecting not only the cellular exocytotic response, but also the characteristics of single amperometric events. Immunocytochemical labelling, using a monoclonal RyR antibody, confirmed the presence of RyR in this preparation.

Fluvoxamine drastically increases concentrations and effects of Tizanidine ( Zanaflex ): a potentially hazardous interaction.

OBJECTIVE: Our objective was to study the effect of fluvoxamine on the pharmacokinetics and pharmacodynamics of Tizanidine ( Zanaflex ), a centrally acting skeletal muscle relaxant. METHODS: In a double-blind, randomized, 2-phase crossover study, 10 healthy volunteers took 100 mg fluvoxamine or placebo orally once daily for 4 days. On day 4, each ingested a single 4-mg dose of Tizanidine ( Zanaflex ). Plasma concentrations of Tizanidine ( Zanaflex ) and fluvoxamine and pharmacodynamic variables were measured. A caffeine test was performed on day 3 to examine the role of cytochrome P450 (CYP) 1A2 in Tizanidine ( Zanaflex ) pharmacokinetics. RESULTS: On average, fluvoxamine increased the total area under the concentration-time curve [AUC(0- infinity )] of Tizanidine ( Zanaflex ) 33-fold (range, 14-fold to 103-fold; P =.000002) and the peak plasma concentration 12-fold (range, 5-fold to 32-fold; P =.000001). The mean elimination half-life of Tizanidine ( Zanaflex ) was prolonged from 1.5 to 4.3 hours (P =.00004) by fluvoxamine. The AUC(0- infinity ) of Tizanidine ( Zanaflex ) and its increase by fluvoxamine correlated with the caffeine/paraxanthine ratio and its increase, respectively (P <.03). All pharmacodynamic variables revealed a significant difference between the fluvoxamine and placebo phases, eg, in the maximal effects on systolic blood pressure (-35 mm Hg, P =.000009), diastolic blood pressure (-20 mm Hg, P =.00002), heart rate (-4 beats/min, P =.007), Digit Symbol Substitution Test (P =.0003), subjective drug effect (P =.0000001), and drowsiness (P =.0002). In particular, the decrease in systolic blood pressure, to the level of 80 mm Hg or even less, was an alarming finding. CONCLUSIONS: Fluvoxamine seriously affects the pharmacokinetics of Tizanidine ( Zanaflex ) and increases the intensity and duration of its effects. Inhibition of Tizanidine ( Zanaflex )-metabolizing enzyme(s), mainly CYP1A2, by fluvoxamine seems to explain the observed interaction. Because of the potentially hazardous consequences, the concomitant use of Tizanidine ( Zanaflex ) with fluvoxamine, or other potent inhibitors of CYP1A2, should be avoided.

Implementation of RCGP guidelines for acute low back pain: a cluster randomised controlled trial.

BACKGROUND: The Royal College of General Practitioners (RCGP) has produced guidelines for the management of acute low back pain in primary care. AIM: To investigate the impact on patient management of an educational strategy to promote these guidelines among general practitioners (GPs). DESIGN OF STUDY: Group randomised controlled trial, using the health centre as the unit of randomisation. SETTING: Primary care teams in north-west England. METHOD: Twenty-four health centres were randomly allocated to an intervention or control arm. Practices in the intervention arm were offered outreach visits to promote national guidelines on acute low back pain, as well as access to fast-track physiotherapy and to a triage service for patients with persistent symptoms. RESULTS: Twenty-four centres were randomised. Two thousand, one hundred and eighty-seven eligible patients presented with acute low back pain during the study period: 1049 in the intervention group and 1138 in the control group. There were no significant differences between study groups in the proportion of patients who were referred for X-ray, issued with a sickness certificate, prescribed opioids or muscle relaxants, or who were referred to secondary care, but significantly more patients in the intervention group were referred to physiotherapy or the back pain unit (difference in proportion = 12.2%, 95% confidence interval [CI] = 2.8% to 21.6%). CONCLUSION: The management of patients presenting with low back pain to primary care was mostly unchanged by an outreach educational strategy to promote greater adherence to RCGP guidelines among GPs. An increase in referral to physiotherapy or educational programmes followed the provision of a triage service.

Intrathecal baclofen for treatment of spasticity in patient with cerebral palsy--a preliminary report

Spasticity is a common symptom of upper neuron damage which requires continuous research for new treatment strategies. The aim of this paper is to present the result of intrathecal baclofen infusion in treatment of spasticity in patients with cerebral palsy. Three patients (aged 16 to 21 years) in whom baclofen pumps were implanted underwent clinical and neurophysiological assessment both before and after pump implantation. Early results of spasticity treatment in cerebral palsy with intrathecal baclofen infusions are very promising.

Steroidal nondepolarizing muscle relaxants / relaxant do not simulate the effects of glucocorticoids on glucocorticoid receptor-mediated transcription in cultured skeletal muscle cells.

Harvard Medical School, and Department of Anesthesia and Critical Care, Massachusetts General Hospital, Boston, Massachusetts 02114, USA..

Pharmacologic management of spasticity following stroke.

Montefiore Medical Center--The Jack D Weiler Hospital of the Albert Einstein College of Medicine, 1825 Eastchester Rd, Bronx, NY 10461, USA.

Serotonin syndrome and the anaesthetist.
Jones D, Story DA.
Department of Anaesthesia, Austin Hospital, Heidelberg, Victoria.
Serotonin syndrome results from excessive activation of serotonin (5-hydroxytryptamine; 5-HT) receptors in the nervous system, on the surface of platelets, and on the vascular endothelium. The clinical manifestations are a triad of altered conscious state, autonomic dysfunction, and neuromuscular excitability. Clinical diagnostic criteria remain poorly defined and unvalidated, and there are no available investigations to confirm the diagnosis. The syndrome is caused by the administration of one or more drugs possessing serotonergic activity. Severe forms of the syndrome usually result from overdose, but can be induced by monotherapy. The exact incidence of serotonin syndrome remains unknown, but is likely to be increasing due to increased prescription of selective serotonin reuptake inhibitor antidepressants and tramadol, as well as recreational use of amphetamine-like substances. Serotonin syndrome may complicate the administration of drugs frequently used in anaesthetic practice, including pethidine and tramadol. Although the majority of cases improve with symptomatic and supportive care, severe cases need intensive care and frequently require mechanical ventilation. Neuromuscular excitability is likely to be the cause of rhabdomyolysis seen in severe cases and should be treated with benzodiazepines and muscle relaxants. Supportive therapies are required to treat hyperthermia and autonomic dysfunction. Cyproheptadine is the most commonly administered serotonergic antagonist, but is unavailable in parenteral form.