Lionel Dumont

Dexamethasone and Risk of Nausea and Vomiting and Postoperative Bleeding After Tonsillectomy in Children: A Randomized Trial

CONTEXT Dexamethasone is widely used to prevent postoperative nausea and vomiting (PONV) in pediatric tonsillectomy. OBJECTIVE To assess whether dexamethasone dose-dependently reduces the risk of PONV at 24 hours after tonsillectomy. DESIGN, SETTING, AND PATIENTS Randomized placebo-controlled trial conducted among 215 children undergoing elective tonsillectomy at a major public teaching hospital in Switzerland from February 2005 to December 2007. INTERVENTIONS Children were randomly assigned to receive dexamethasone (0.05, 0.15, or 0.5 mg/kg) or placebo intravenously after induction of anesthesia. Acetaminophen-codeine and ibuprofen were given as postoperative analgesia. Follow-up continued until the 10th postoperative day. MAIN OUTCOME MEASURES The primary end point was prevention of PONV at 24 hours; secondary end points were decrease in the need for ibuprofen at 24 hours and evaluation of adverse effects. RESULTS At 24 hours, 24 of 54 participants who received placebo (44%; 95% confidence interval [CI], 31%-59%) had experienced PONV compared with 20 of 53 (38%; 95% CI, 25%-52%), 13 of 54 (24%; 95% CI, 13%-38%), and 6 of 52 (12%; 95% CI, 4%-23%) who received dexamethasone at 0.05, 0.15, and 0.5 mg/kg, respectively (P<.001 for linear trend). Children who received dexamethasone received significantly less ibuprofen. There were 26 postoperative bleeding episodes in 22 children. Two of 53 (4%; 95% CI, 0.5%-13%) children who received placebo had bleeding compared with 6 of 53 (11%; 95% CI, 4%-23%), 2 of 51 (4%; 95% CI, 0.5%-13%), and 12 of 50 (24%; 95% CI, 13%-38%) who received dexamethasone at 0.05, 0.15, and 0.5 mg/kg, respectively (P = .003). Dexamethasone, 0.5 mg/kg, was associated with the highest bleeding risk (adjusted relative risk, 6.80; 95% CI, 1.77-16.5). Eight children had to undergo emergency reoperation because of bleeding, all of whom had received dexamethasone. The trial was stopped early for safety reasons. CONCLUSION In this study of children undergoing tonsillectomy, dexamethasone decreased the risk of PONV dose dependently but was associated with an increased risk of postoperative bleeding. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00403806.

Fetal bradycardia due to intrathecal opioids for labour analgesia: a systematic review

Objective To evaluate fetal and maternal adverse effects of intrathecal opioid analgesia during labour.

The role of nicotinic acetylcholine receptors in the mechanisms of anesthesia

Nicotinic acetylcholine receptors are members of the ligand-gated ion channel superfamily, that includes also gamma-amino-butiric-acid(A), glycine, and 5-hydroxytryptamine(3) receptors. Functional nicotinic acetylcholine receptors result from the association of five subunits each contributing to the pore lining. The major neuronal nicotinic acetylcholine receptors are heterologous pentamers of alpha4beta2 subunits (brain), or alpha3beta4 subunits (autonomic ganglia). Another class of neuronal receptors that are found both in the central and peripheral nervous system is the homomeric alpha7 receptor. The muscle receptor subtypes comprise of alphabetadeltagamma (embryonal) or alphabetadeltaepsilon (adult) subunits. Although nicotinic acetylcholine receptors are not directly involved in the hypnotic component of anesthesia, it is possible that modulation of central nicotinic transmission by volatile agents contributes to analgesia. The main effect of anesthetic agents on nicotinic acetylcholine receptors is inhibitory. Volatile anesthetics and ketamine are the most potent inhibitors both at alpha4beta2 and alpha3beta4 receptors with clinically relevant IC(50) values. Neuronal nicotinic acetylcholine receptors are more sensitive to anesthetics than their muscle counterparts, with the exception of the alpha7 receptor. Several intravenous anesthetics such as barbiturates, etomidate, and propofol exert also an inhibitory effect on the nicotinic acetylcholine receptors, but only at concentrations higher than those necessary for anesthesia. Usual clinical concentrations of curare cause competitive inhibition of muscle nicotinic acetylcholine receptors while higher concentrations may induce open channel blockade. Neuronal nAChRs like alpha4beta2 and alpha3beta4 are inhibited by atracurium, a curare derivative, but at low concentrations the alpha4beta2 receptor is activated. Inhibition of sympathetic transmission by clinically relevant concentrations of some anesthetic agents is probably one of the factors involved in arterial hypotension during anesthesia.

Magnesium as an Adjuvant to Postoperative Analgesia: A Systematic Review of Randomized Trials

BACKGROUND:Randomized trials have reached different conclusions as to whether magnesium is a useful adjuvant to postoperative analgesia. METHODS:We performed a comprehensive search (electronic databases, bibliographies, all languages, to 4.2006) for randomized comparisons of magnesium and placebo in the surgical setting. Information on postoperative pain intensity and analgesic requirements was extracted from the trials and compared qualitatively. Dichotomous data on adverse effects were combined using classic methods of meta-analysis. RESULTS:Fourteen randomized trials (778 patients, 404 received magnesium) tested magnesium laevulinate, gluconate or sulfate. With magnesium, postoperative pain intensity was significantly decreased in four (29%) trials, was no different from placebo in seven (50%), and was increased in one (7%); two trials (14%) did not report on pain intensity. With magnesium, postoperative analgesic requirements were significantly reduced in eight (57%) trials, were no different from placebo in five (36%), and were increased in one (7%). Magnesium-treated patients had less postoperative shivering (relative risk 0.38, 95% confidence interval 0.17–0.88, number-needed-to-treat 14). Seven trials reported on magnesium serum levels. In all, serum levels were increased in patients who received magnesium; in six, serum levels were decreased in those who received placebo. CONCLUSIONS:These trials do not provide convincing evidence that perioperative magnesium may have favorable effects on postoperative pain intensity and analgesic requirements. Perioperative magnesium supplementation prevents postoperative hypomagnesemia and decreases the incidence of postoperative shivering. It may be worthwhile to further study the role of magnesium as a supplement to postoperative analgesia, since this relatively harmless molecule is inexpensive, and the biological basis for its potential antinociceptive effect is promising.

Quality of recovery in children: sevoflurane versus propofol.

Background: Sevoflurane, with its low pungency and low blood and tissue solubility, is an attractive anaesthetic in paediatric outpatient surgery. Propofol‐anaesthesia is recognised for its rapid and clear‐headed emergence. This study was designed to compare emergence and recovery characteristics of sevoflurane and propofol anaesthesia for tonsillectomy in children.

Changes in pulmonary mechanics during laparoscopic gastroplasty in morbidly obese patients

Background: Obesity is an important respiratory risk factor after abdominal surgery. Laparoscopic surgical techniques seem beneficial in obese patients in terms of respiratory morbidity, with a faster return to normal respiratory function. However, there is little information about intraoperative respiratory mechanics and about patient tolerance to abdominal insufflation in the morbidly obese.

Sensory block extension during combined spinal and epidural.

Background and Objectives. During a combined spinal and epidural technique, extension of sensory block by epidural injection of saline or bupivacaine has been demonstrated and attributed to a volume effect or to the combination of a volume effect with a local anesthetic effect. This two‐part study was designed to evaluate the time dependency of the volume effect and the local anesthetic effect on the mechanism of spinal block extension. Methods. We performed two prospective studies. Thirty patients were randomized in each study. A combined spinal and epidural was performed in a sitting position in all groups. The patients in the first study received 15 mg hyperbaric bupivacaine intrathecally and were placed supine 2 minutes after spinal injection. They received 10 mL epidural saline either 5 minutes after spinal (group A) or 20 minutes after spinal (group B) compared to a control group (group C). The patients in the second study received 12.5 mg hyperbaric bupivacaine intrathecally and were placed supine 5 minutes after spinal injection. They then received epidurally either 10 mL saline 7 minutes after spinal (group D) or 10 mL bupivacaine 7 minutes after spinal (group E) or nothing (group F). Sensory block levels were assessed by a loss of sensation to cold using ether. Results. In the first portion of this study, in group A, area under the curve of sensory block levels by time from 10 to 40 minutes after spinal injection, and maximum sensory block levels were significantly higher (P < .05) compared to groups B and C. In the second portion of the study, sensory block levels were comparable at all times in the three groups. Conclusions. During a combined spinal and epidural technique with the use of hyperbaric bupivacaine, the volume effect is time dependent and is seen when epidural top up is done soon after spinal injection. This volume effect is abolished when patients are left seated for 5 minutes after spinal injection. The local anesthetic effect is not demonstrated when high sensory block levels are achieved by spinal injection.

Bispectral and spectral entropy indices at propofol-induced loss of consciousness in young and elderly patients

BACKGROUND Bispectral (BIS) and state/response entropy (SE/RE) indices have been widely used to estimate depth of anaesthesia and sedation. In adults, independent of age, adequate and safe depth of anaesthesia for surgery is usually assumed when these indices are between 40 and 60. Since the EEG is changing with increasing age, we investigated the impact of advanced age on BIS, SE, and RE indices during induction. METHODS BIS and SE/RE indices were recorded continuously in elderly (> or =65 yr) and young (< or =40 yr) surgical patients who received propofol until loss of consciousness (LOC) using stepwise increasing effect-site concentrations. LOC was defined as an observer assessment of alertness/sedation score <2, corresponding to the absence of response to mild prodding or shaking. RESULTS We analysed 35 elderly [average age, 78 yr (range, 67-96)] and 34 young [35 (19-40)] patients. At LOC, all indices were significantly higher in elderly compared with young patients: BIS(LOC), median 70 (range, 58-91) vs 58 (40-70); SE(LOC), 71 (31-88) vs 55.5 (23-79); and RE(LOC), 79 (35-96) vs 59 (25-80) (P<0.001 for all comparisons). With all three monitors, only a minority of elderly patients lost consciousness within a 40-60 index range: two (5.7%) with BIS and RE each, and seven (20%) with SE. In young patients, the respective numbers were 20 (58.8%) for BIS, 13 (38.2%) for SE, and nine (26.5%) for RE. CONCLUSIONS In adults undergoing propofol induction, BIS, SE, and RE indices at LOC are significantly affected by age.

Reappraisal of Acetazolamide for the Prevention of Acute Mountain Sickness: A Systematic Review and Meta-Analysis

Acetazolamide is used to prevent acute mountain sickness (AMS). We assessed efficacy and harm of acetazolamide for the prevention of AMS, and tested for dose-responsiveness. We systematically searched electronic databases (until April 2011) for randomized trials comparing acetazolamide with placebo for the prevention of AMS. For each dose, risk ratios were aggregated using a Mantel-Haenszel fixed effect model. Numbers needed to treat (NNT) to benefit one subject with each dose were calculated for different baseline risks. Modes of ascent were taken as proxies of baseline risks. Twenty-four trials were included; 1011 subjects received acetazolamide 250, 500, or 750 mg day⁻¹; 854 received placebo. When climbing, median speed of ascent was 14 m/h, average AMS rate in controls was 34%, and NNT to prevent AMS with acetazolamide 250, 500, and 750 mg/day compared with placebo was 6.5, 5.9, and 5.3. When ascending by transport and subsequent climbing (speed of ascent 133 m/h) or by transport alone (491 m/h), average AMS rate in controls was 60%, and NNT with acetazolamide 250, 500, and 750 mg/day was 3.7, 3.3, and 3.0. In hypobaric chambers, median speed of ascent was 4438 m/h, average AMS rate in controls was 86%, and NNT with acetazolamide 250, 500, and 750 mg/day was 2.6, 2.3, and 2.1. The risk of paresthesia was increased with all doses. The risk of polyuria and taste disturbance was increased with 500 and 750 mg/day. The degree of efficacy of acetazolamide for the prevention of AMS is limited when the baseline risk is low, and there is some evidence of dose-responsiveness.

Hemodynamic changes during laparoscopic gastroplasty in morbidly obese patients

Background: In nonobese patients, peritoneal insufflation has consistently been shown to influence parameters of preload and afterload as well as cardiac output. Obese patients have an abnormal and particular cardiovascular status. The aim of this study was to investigate the hemodynamic changes induced by an increase of intra-abdominal pressure in morbidly obese patients (MOP). Methods: Standard general anesthetia was administered to 15 informed MOP (body mass index > 40 kg/m2) scheduled for laparoscopic gastroplasty. Hemodynamic parameters were measured by thermodilution through a pulmonary artery catheter and through invasive blood pressure monitoring. Results: CO2 insufflation with an intra-abdominal pressure of 17 mmHg caused a significant increase of mean arterial pressure (MAP) (33%, P = 0.005), mean pulmonary arterial pressure (MPAP) (40%, P = 0.001), pulmonary capillary wedge pressure (PCWP) (41%, P = 0.001), and central venous pressure (CVP) (55%, P = 0.001). The increase in diastolic filling pressures could be due to an increase in the filling volume or to a decrease in diastolic compliance. Ventricular volumes were not measured but we speculate that the rise in CVP, PCWP and MPAP is due to an increase in intrathoracic pressure as judged by the increase of pulmonary airway pressure. Stroke volume fell slightly (11%, P = 0.008), because of a reduction in transmural pressure and a fall ineffective preload. Cardiac output rose slightly (16%, P = 0.005) because of an increase in heart rate (15%, P = 0.014) probably induced by sympathetic stimulation, which only became fully operative after 15 minutes. Conclusions: When compared to nonobese patients our obese patients tolerated the pneumoperitoneum surprisingly well, without experiencing fall in cardiac output. The hemodynamic consequences of peritoneal insufflation seem to be different in obese and nonobese patients.