Effect of interscalene brachial plexus block on heart rate variability / 대한마취과학회지

BACKGROUND: Interscalene brachial plexus block (ISB) may be followed by cardiovascular instability. Until date, there is no clear picture available about the underlying mechanisms of ISB. In this study, we aimed to determine the changes in heart rate variability (HRV) parameters after ISB and the differences between right- and left-sided ISBs. METHODS: We prospectively studied 24 patients operated for shoulder surgery in sitting position and divided them into two respective groups: R (right-sided block = 14 pts) and L (left-sided block = 10 pts). HRV data were taken before and 30 min after the block. Ropivacaine without ephedrine was used for the ISB through an insulated block needle connected to a nerve stimulator. Statistical analysis implemented chi-square, Student's and t-paired tests. Skewed distributions were analyzed after logarithmic transformation. RESULTS: All the studied patients had successful blocks. Horner's syndrome signs were observed in 33.3% of the patients (R = 5/14, L = 3/10; [P = 0.769]). There were no significant differences in pre-block HRV between the groups. The application of ISB had differential effect on HRV variables: R-blocks increased QRS and QTc durations and InPNN50, while a statistical decrease was seen in InLF. L-blocks did not show any significant changes. These changes indicate a reduced sympathetic and an increased parasympathetic influence on the heart's autonomic flow after R-block. CONCLUSIONS: Based on the obtained results we conclude that ISB, possibly through extension of block to the ipsilateral stellate ganglion, alters the autonomic outflow to the central circulatory system in a way depending on the block's side.

Peripheral nerve blockade as an exclusive approach to obturator nerve block in anterior cruciate ligament reconstructive surgery / 대한마취과학회지

BACKGROUND: Obturator nerve block plays an additive role on the quality of analgesia for knee surgery. Since the use of dual guidance increases the success rate of nerve blocks, we investigated the feasibility of performing anterior cruciate ligament reconstruction under dual-guided blockade of obturator with femoral and sciatic nerves. Furthermore, we propose a novel method for the assessment of obturator nerve block. METHODS: Fifty-seven patients undergoing anterior cruciate ligament repair were studied. Neurostimulating needles were guided out-of-plane by ultrasound. To induce the obturator nerve block, 10 ml of ropivacaine 0.5% were injected after eliciting contractions of adductor longus, brevis and magnus followed by block assessment for 30 minutes by examining the patient lift and left down the leg. RESULTS: The sonographic recognition of obturator nerve was easy and quick in all cases. Time for applying the block was 119.9 +/- 79.2 sec. Assessing this block with lifting-leaving down the leg gave satisfactory results in 24.0 +/- 5.07 min. After performing femoral-sciatic blocks, the inflation of tourniquet resulted in VAS score of > 0 in 2/57 patients and operation in 12/57. Total dose of fentanyl was 120.1 +/- 64.6 microg and of midazolam 1.86 +/- 0.8 mg. In 6 patients propofol was administered for sedation and 1 of them required ventilation with laryngeal mask airway, converting the anesthesia technique to general anesthesia. CONCLUSIONS: Our data suggest that anterior cruciate ligament reconstruction can be performed under obturator-femoral-sciatic blocks. Identification of obturator nerve with ultrasound is easy and the block can be assessed by observing how the patient lifts and leaves down the leg.