Optimisation de l’administration des agents anesthésiques inhalés : débit de gaz frais ou fraction délivrée ?

Introduction

During volatile closed-circuit anaesthesia, a chosen end-tidal fraction (Fet) could be achieved by setting either delivered fraction (Fd) or fresh gas flow (FGF). This study compared the efficacy of both strategies and the resulting drug consumption.

Patients and methods

Sixty patients (10 per group) were administered, after intravenous induction and intubation, desflurane, sevoflurane or isoflurane + 50% N₂O, to achieve a target Fet equal to one minimal alveolar concentration (MAC), according to one strategy: high FGF (HFGF) Fd fixed 20% above target Fet, FGF 10 l/min then 1 l/min after achieving the target, FGF opened at 10 l/min at the end of surgery; low FGF (LFGF) FGF fixed at 1 l/min, Fd at the maximal value on the vaporizer, then set at target Fet + 20% after achieving Fet equal to one MAC, FGF maintained at 1 l/min until extubation.

Results

The target Fet was achieved in all patients in LFGF within 2.1 ± 0.9 min followed by 15% (isoflurane) to 57% (sevoflurane) overdosage, but only in nine patients out of 30 after 10 min in HFGF. Delays were similar between desflurane and sevoflurane. Volatile consumption was decreased by 75% in LFGF. Fifty percent decrement and extubation times were shorter with HFGF, similarly for the three agents.

Conclusion

Massive overdosage of Fd is the fastest, reproducible and cheapest strategy to achieve (or to increase) a chosen Fet. High FGF is the fastest to decrease Fet during or at the end of anaesthesia. Combining Fd and FGF adjustments in order to maximize Fd/Fet gradients overwrites pharmacokinetic differences between desflurane and sevoflurane and reduces differences with isoflurane. Automatic adjustments based on volatile pharmacockinetics would be helpful to achieve a target Fet without overdosage.     

Removal of an iliosacral screw entrapping the L5 nerve root after failed posterior pelvic ring fixation: a case report

We present a case of a pelvic ring fracture that was originally treated with anterior symphyseal plating and a misplaced percutaneous iliosacral screw. The anterior extraosseus portion of the misplaced 7.3-mm cannulated screw irritated the L5 nerve root, resulting in a radiculopathy. Subsequent surgery involved and mandated removing the bent screw after open identification and protection of the L5 nerve root to avoid further nerve damage; the sacroiliac joint was subsequently debrided and fused. This case represents a complication of acute percutaneous iliosacral screw fixation of pelvic ring injuries and the subsequent strategy for successful salvage.     

The effects of biphasic waveform design on post-resuscitation myocardial function

OBJECTIVES: This study examined the effects of biphasic truncated exponential waveform design on survival and post-resuscitation myocardial function after prolonged ventricular fibrillation (VF). BACKGROUND: Biphasic waveforms are more effective than monophasic waveforms for successful defibrillation, but optimization of energy and current levels to minimize post-resuscitation myocardial dysfunction has been largely unexplored. We examined a low-capacitance waveform typical of low-energy application (low-energy biphasic truncated exponential [BTEL]; 100 microF, < or =200 J) and a high-capacitance waveform typical of high-energy application (high-energy biphasic truncated exponential [BTEH]; 200 microF, > or =200 J). METHODS: Four groups of anesthetized 40- to 45-kg pigs were investigated. After 7 min of electrically induced VF, a 15-min resuscitation attempt was made using sequences of up to three defibrillation shocks followed by 1 min of cardiopulmonary resuscitation. Animals were randomized to BTEL at 150 J or 200 J or to BTEH at 200 J or 360 J. RESULTS: Resuscitation was unsuccessful in three of the five animals treated with BTEH at 200 J. All other attempts were successful. Significant therapy effects were observed for survival (p = 0.035), left ventricular ejection fraction (p < 0.001), stroke volume (p < 0.001), fractional area change (p < 0.001), cardiac output (p = 0.044), and mean aortic pressure (p < 0.001). Hemodynamic outcomes were negatively associated with energy and average current but positively associated with peak current. Peak current was the only significant predictor of survival (p < 0.001). CONCLUSIONS: Maximum survival and minimum myocardial dysfunction were observed with the low-capacitance 150-J waveform, which delivered higher peak current while minimizing energy and average current.     

Role of Established Type 2 Diabetes–Susceptibility Genetic Variants in a High Prevalence American Indian Population

Several single nucleotide polymorphisms (SNPs) associated with type 2 diabetes mellitus (T2DM) have been identified, but there is little information on their role in populations at high risk for T2DM. We genotyped SNPs at 63 T2DM loci in 3,421 individuals from a high-risk American Indian population. Nominally significant (P < 0.05) associations were observed at nine SNPs in a direction consistent with the established association. A genetic risk score derived from all loci was strongly associated with T2DM (odds ratio 1.05 per risk allele, P = 6.2 × 10⁻⁶) and, in 292 nondiabetic individuals, with lower insulin secretion (by 4% per copy, P = 4.1 × 10⁻⁶). Genetic distances between American Indians and HapMap populations at T2DM markers did not differ significantly from genomic expectations. Analysis of U.S. national survey data suggested that 66% of the difference in T2DM prevalence between African Americans and European Americans, but none of the difference between American Indians and European Americans, was attributable to allele frequency differences at these loci. These analyses suggest that, in general, established T2DM loci influence T2DM in American Indians and that risk is mediated in part through an effect on insulin secretion. However, differences in allele frequencies do not account for the high population prevalence of T2DM.