Intraneural Ultrasound-guided Sciatic Nerve Block: Minimum Effective Volume and Electrophysiologic Effects.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Both extra- and intraneural sciatic injection resulted in significant axonal nerve damage. This study aimed to establish the minimum effective volume of intraneural ropivacaine 1% for complete sensory-motor sciatic nerve block in 90% of patients, and related electrophysiologic variations. METHODS: Forty-seven consecutive American Society of Anesthesiologists physical status I-II patients received an ultrasound-guided popliteal intraneural nerve block following the up-and-down biased coin design. The starting volume was 15 ml. Baseline, 5-week, and 6-month electrophysiologic tests were performed. Amplitude, latency, and velocity were evaluated. A follow-up telephone call at 6 months was also performed. RESULTS: The minimum effective volume of ropivacaine 1% in 90% of patients for complete sensory-motor sciatic nerve block resulted in 6.6 ml (95% CI, 6.4 to 6.7) with an onset time of 19 ± 12 min. Success rate was 98%. Baseline amplitude of action potential (mV) at ankle, fibula, malleolus, and popliteus were 8.4 ± 2.3, 7.1 ± 2.0, 15.4 ± 6.5, and 11.7 ± 5.1 respectively. They were significantly reduced at the fifth week (4.3 ± 2.1, 3.5 ± 1.8, 6.9 ± 3.7, and 5.2 ± 3.0) and at the sixth month (5.9 ± 2.3, 5.1 ± 2.1, 10.3 ± 4.0, and 7.5 ± 2.7) (P < 0.001 in all cases). Latency and velocity did not change from the baseline. No patient reported neurologic symptoms at 6-month follow-up. CONCLUSIONS: The intraneural ultrasound-guided popliteal local anesthetic injection significantly reduces the local anesthetic dose to achieve an effective sensory-motor block, decreasing the risk of systemic toxicity. Persistent electrophysiologic changes suggest possible axonal damage that will require further investigation.

Effects of the Intraneural and Subparaneural Ultrasound-Guided Popliteal Sciatic Nerve Block: A Prospective, Randomized, Double-Blind Clinical and Electrophysiological Comparison.

BACKGROUND AND OBJECTIVES: This prospective, randomized, double-blind study compared the effects of the ultrasound-guided popliteal sciatic nerve block performed by either intraneural or subparaneural approach followed by an electrophysiological evaluation. We hypothesized that intraneural injection provides a faster onset with a better success rate compared with the subparaneural approach. METHODS: Eighty-eight patients were enrolled and randomized to receive an ultrasound-guided popliteal sciatic nerve block injecting 15 mL ropivacaine 1% according to an intraneural injection (group INTRA = 44) or a subparaneural injection (group SUBPARA = 44). The primary end point was the onset time of sensory and motor block, whereas secondary end points were successful, duration of the block, and the variation of the electrophysiological assessment after 5 weeks. The study was registered prior to patient enrollment (clinicaltrials.gov identifier NCT01987128). RESULTS: The median onset time for successful sciatic nerve block in the INTRA group was 10 (5-15 [5-30]) minutes versus 25 (15-35 [5-45]) minutes in the SUBPARA group (P < 0.001), with a rate of 41/43 (95.3%) compared with 25/40 (62.5%) in the SUBPARA group (P < 0.001). No difference was found regardless of the duration of the block. Fifty-three patients also performed the electrophysiological assessment at 5 weeks, showing a subclinical, significant reduction in amplitude of the action potentials with no difference between groups. No patients reported any clinical neurological complications after 6 months. CONCLUSIONS: In ultrasound-guided popliteal sciatic nerve block, intraneural injection provided a faster onset and better success rate compared with subparaneural. Both techniques resulted in a similar subclinical reduction in amplitude of the sciatic action potentials at 5 weeks after surgery. These findings should not be extended to other approaches.

Bispectral index evaluation of the sedative effect of acupuncture in healthy volunteers.

OBJECTIVE: To evaluate the sedative effect of acupuncture in healthy volunteers by means of the BIS monitor. Secondary end-points were the evaluation of subjective sedative sensation induced by acupuncture and possible lasting of the sedative effect post needles removal. METHODS: We performed a cross-over, single-blinded study on 10 healthy volunteers to evaluate objective and subjective sedative effect of acupuncture compared to sham acupuncture. We recorded heart rate, pulse-oxymetry, BIS at baseline, during a 20-min. stimulation period, and for the following 20 minutes after needles removal. Besides, we asked volunteers to score their subjective state by VAS at baseline, after the stimulation period (20th minute) and 20 minutes after needles removal. RESULTS: BIS values were not significantly different between true and sham acupuncture. A suggestive but not statistically significant difference was evident in VAS score, with true- better than sham acupuncture. There was no difference in the incidence of sleep during the experimental phases, nor in the incidence of insomnia or somnolence in the following 24 hours. HR and SpO2 remained always in a normal range. CONCLUSIONS: The sedative effect of true acupuncture was not different from that of sham acupuncture in healthy volunteers. We suggest that acupuncture could have a mild sedative action that can be demonstrated only treating anxious patients and not calm volunteers. In our opinion, the low potency of this technique can be an advantage allowing acupuncture safe application in a wide range of settings.

ECG changes after CABG: the role of the surgical technique.

OBJECTIVE: The purpose of this study was to determine whether coronary artery bypass grafting (CABG) surgery on the beating heart (BH) is associated with reduction of R-wave potentials on the precordial leads on the surface electrocardiogram (ECG) as previously shown for CABG with cardiopulmonary bypass. METHODS: Fifty-four patients undergoing CABG surgery at a single tertiary care university hospital were analyzed. Patients suffering a postoperative cardiac event (myocardial infarction) or nonspecific ECG changes were excluded. ECG results were recorded at arrival in the intensive care unit, after 4 and 18 hours postoperatively; simultaneously, myocardial cell damage biomarkers (CK-MB and cTnI) were assayed. A control group of 31 patients undergoing mitral valve repair was also evaluated. RESULTS: Patients operated with the BH (OPCABG) technique did not show any decrease of R-wave amplitude at 0, 4, and 18 hours postoperatively; whereas those operated with CPB, both for coronary artery surgery and for mitral repair, had a similar extent and pattern of R-wave reduction. The release of myocardial necrosis markers was significantly lower in coronary artery patients operated with BH than in those operated with CPB; however, no statistically significant correlation between the ECG changes and release of myocardial cell damage markers was observed in any of the groups. CONCLUSIONS: The findings indicate, for the first time, that CABG surgery on the BH is not followed by any reduction of R-wave amplitude on precordial leads and confirms that the BH technique is associated with a lower release of myocardial cell damage markers.

Cardiac biomarker release after CABG with different surgical techniques.

OBJECTIVE: To investigate the release of cardiac biomarkers (troponin I and CK-MB) in patients undergoing coronary artery bypass graft (CABG) with or without cardiopulmonary bypass (CPB). DESIGN: Prospective study. SETTING: University tertiary hospital. PARTICIPANTS: Sixty-five consecutive patients undergoing coronary artery bypass grafting (>or=2 vessel disease, ejection fraction >or=0.35%, elective procedure). INTERVENTIONS: Cardiac biomarkers were measured before surgery, at intensive care unit arrival, 4 and 18 hours after the end of the procedure. MEASUREMENTS AND MAIN RESULTS: Cardiac biomarker release was higher in on-pump than in off-pump patients at every time point. On multivariate analysis, CPB (p < 0.0001), number of distal grafts (p = 0.005), and hypertension treatment (p = 0.03) were the only independent predictors of peak cardiac troponin release. CONCLUSIONS: Cardiac troponin I release after multivessel CABG is associated with the technique. Different values for the normal range should be considered. OPCABG is minimally invasive for the heart as far as myocardial marker release is concerned.