Ultrasound-guided approach to nerves (direct vs. tangential) and the incidence of intraneural injection: a cadaveric study.

This study evaluated the incidence of nerve puncture and intraneural injection based on the needle approach to the nerve (direct vs. tangential). Two expert operators in regional anaesthesia performed in-plane ultrasound-guided nerve blocks (n = 158) at different levels of the brachial plexus in cadavers, aiming either directly for the nerve (n = 77) or tangentially inferior to the nerve (n = 81). After reaching the outer limit of the nerve, the needle was intentionally advanced approximately 1 mm in both approaches, and 0.2-0.5 ml of saline was injected. Each operator classified (in real time) the needle tip and injectate as intraneural or not. Video clips showing the final position of the needle and the injection were evaluated in the same manner by seven independent expert observers who were blinded to the aims of this study. In addition, 20 injections were performed with ink for histological evaluation. Intraneural injections of saline were observed by the operator in 58% (45/77) of cases using the direct approach and 12% (10/81) of cases using the tangential approach (p < 0.001). The independent observers agreed with the operator in a substantial number of cases (Cohen's kappa index 0.65). Histological studies showed intraneural spread in 83% (5/6) of cases using the direct approach and in 14% (2/14) of cases using the tangential approach (p = 0.007). No intrafascicular injections were observed. There was good agreement between the operators' assessment and subsequent histological evaluation (Cohen's kappa = 0.89). Simulation of an unintentional/accidental advancement of the needle 'beyond the edge' of the nerve suggests significantly increased risk of epineural perforation and intraneural injection when a direct approach to the nerve is used, compared with a tangential approach.

Intrathecal chloroprocaine vs. lidocaine in day-case surgery: recovery, discharge and effect of pre-hydration on micturition.

BACKGROUND: This randomised, double blind prospective study compares intrathecal lidocaine with chloroprocaine in day-case surgery and the influence of a 500 ml pre-load intravenously. We tested the hypothesis that chloroprocaine provides faster recovery and discharge in day-case surgery. Secondary we studied the influence of a preload compared with fluid restriction on discharge time and micturition problems. METHODS: One hundred patients undergoing day-case arthroscopy were randomised to receive either lidocaine (L) 60 mg or chloroprocaine (CP) 40 mg intrathecally and this with (L+, CP+) or without (L−, CP−) a 500 ml pre-load of crystalloid. Block characteristics, micturition and discharge times were registered. Bladder volumes were monitored by ultrasound. Micturition problems received a micturition score. RESULTS: Onset and quality of the block were comparable between groups. Time to regain Bromage 1 and L2 regression were shorter for the CP group compared with the L group. Voiding (168 ± 44 min) and discharge (178 ± 52 min) were approximately 40 min faster for the CP group compared with the L group. Pre-load provided faster bladder filling but there were no differences in voiding time within the CP or L group. The CP+ group (166 ± 36 min) was discharged faster than both L groups (226 ± 57 min, 227 ± 59 min). More serious micturition problems occurred in the L+ group compared with both CP groups. CONCLUSION: Chloroprocaine is suitable for day-case surgery because of faster block regression and discharge than lidocaine. A 500 ml pre-load may not affect discharge but did not increase micturition problems for chloroprocaine.

The effects of beta-adrenergic stimulation on the length-dependent regulation of myocardial function in coronary surgery patients.

UNLABELLED: Increasing cardiac load by leg elevation identifies patients with load-dependent impairment of left ventricular (LV) function. This impairment is related to a deficient length-dependent regulation of LV function. We investigated the effects of dobutamine on length-dependent regulation of LV function in coronary surgery patients (n = 25). High-fidelity LV pressure tracings were obtained at end-expiration, while hearts were paced at a fixed rate of 90 bpm. Effects of leg elevation on contraction and relaxation were compared before and during dobutamine 5 microg x kg(-1) x min(-1). Effects on contraction were evaluated by analysis of changes in dP/dtmax. Effects on relaxation were assessed by analysis of R (slope of the relation between the time constant of isovolumic relaxation and end-systolic pressure). Correlations were calculated with linear regression analysis using Pearson's coefficient r. The effects of leg elevation on variables of contraction and relaxation were coupled. We found a close relationship between changes in dP/dtmax and individual values of R (r = 0.84; P < 0.001). Dobutamine improved myocardial function and accelerated LV pressure decrease. Under dobutamine, the increase in dP/dtmax with leg elevation was larger (P < 0.001) and load dependence of LV relaxation was reduced (P = 0.001). Dobutamine improved the effects of leg elevation on LV function, reflecting improved length-dependent regulation of LV function. IMPLICATIONS: This study demonstrated that beta-adrenoreceptor stimulation with dobutamine improved length-dependent regulation of myocardial function assessed during leg elevation in cardiac surgical patients.

Effects of nicardipine and urapidil on length-dependent regulation of myocardial function in coronary artery surgery patients.

OBJECTIVE: To assess effects of a decrease in left ventricular (LV) afterload (pharmacologically induced by nicardipine and urapidil) on myocardial contraction and relaxation, with emphasis on the effects on load dependence of myocardial function. DESIGN: Prospective, blinded study. SETTING: University hospital. PARTICIPANTS: Coronary artery surgery patients. INTERVENTIONS: Alterations of systolic load were effected by leg elevation in control conditions and after administration of either nicardipine or urapidil before and after cardiopulmonary bypass. MEASUREMENTS AND MAIN RESULTS: High-fidelity LV pressure tracings were obtained at end-expiration while hearts were paced at a fixed rate of 90 beats/min. Hemodynamic effects of leg elevation were compared before and after nicardipine, 7 microg/kg (n = 15), and before and after urapidil, 0.4 mg/kg (n = 15). The effects of leg elevation on parameters of contraction and relaxation were coupled. Both nicardipine and urapidil similarly decreased systolic pressures and peripheral resistance. Nicardipine decreased rate of pressure development (dP/dtmax) and slowed LV pressure fall, whereas load dependence of LV relaxation was not altered. Urapidil did not alter dP/dtmax, rate of LV pressure fall, or load dependence of relaxation. Similar results were observed after cardiopulmonary bypass. CONCLUSIONS: The results of the present study indicate that a pharmacologically induced moderate reduction in LV afterload with nicardipine or urapidil did not alter the length-dependent regulation of myocardial function.