Analgesic effect of a single-dose of perineural dexamethasone on ultrasound-guided femoral nerve block after total knee replacement. / Eficacia analgésica de una dosis única de dexametasona perineural en el bloqueo ecoguiado del nervio femoral en cirugía de prótesis total de rodilla.

INTRODUCTION: Total knee replacement is usually a very painful procedure. A single-dose of femoral nerve block has been shown to provide similar analgesia to an epidural, with fewer side effects, but limited in time. OBJECTIVE: To compare the analgesia provided by dexamethasone used at perineural level in the femoral nerve block after total knee replacement with the one used at intravenous level, and with that of a control group. MATERIAL AND METHODS: A prospective, randomised, double-blind controlled trial was conducted on 81 patients randomly assigned to one of three groups: 1)IV dexamethasone (8mg); 2)perineural dexamethasone (8mg), and 3)placebo. All patients received 20ml of ropivacaine 0.5% for femoral nerve block. The primary outcome was the duration of the sensory-analgesic block of the femoral nerve block. The secondary outcomes included pain intensity measurements, patient satisfaction, and incidence of complications. RESULTS: Randomisation was effective. Analgesia duration was significantly higher (P<.0001) in the perineural dexamethasone group (mean 1152.2min, 95% confidence interval [95% CI]: 756.9-1547.6) in comparison with the control group (mean 186min, 95%CI: 81.2-292) and dexamethasone IV group (mean 159.4min, 95%CI: 109.8-209). Postoperative pain, complications and side effects were also lower in this group. CONCLUSIONS: Dexamethasone prolongs sensory block of single dose of femoral nerve block using ropivacaine. It also provides better analgesia and patient satisfaction, with fewer side effects.

Influence of acute unilateral vestibular lesions on the respiratory rhythm after active change of posture in human subjects.

The influence of acute unilateral vestibular lesions on respiratory rhythm after active change of posture, was evaluated by comparing responses from patients with acute vestibular neuritis, with those from normal subjects with minor injuries other than vestibular (e.g. epistaxis, headache) and patients with chronic bilateral vestibular dysfunction. Respiratory movements of the thorax-abdomen were recorded during 5 minutes in supine position, 5 minutes of back-unsupported sitting and 5 minutes of upright stance. Compared to supine position, sitting-up induced different responses in each group (p < 0.05, ANOVA). The healthy subjects showed a consistent decrease in the mean respiratory frequency related to an increase of the expiration time, which was absent in patients with vestibular neuritis. Subjects with minor injuries showed the opposite changes of expiration time and inspiration time with no change of the respiratory frequency and patients with bilateral vestibular dysfunction showed a trend to increase their respiratory frequency. Standing-up did not evoke any further changes in any group. We conclude that the vestibular system modulates the respiratory response to reorientation of the head and trunk to upright position and this influence is reduced during the acute stage of a vestibular lesion.