Anaesthesia
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We measured the pulsatility indices in the inferior collateral and posterior recurrent ulnar arteries, which supply the ulnar nerve at the elbow, in 38 conscious adults. Compared with a straight 30° abducted arm, elbow flexion to 120° reduced the mean (SD) pulsatility index in the inferior artery and increased the pulsatility index in the posterior artery: from 3.36 (0.86) to 3.04 (0.94), p = 0.001, and from 3.14 (0.81) to 3.64 (1.05), p < 0.0005, respectively. The mean (95% CI) pulsatility index in the inferior artery was unaffected by shoulder abduction to 120°, but it was decreased in the posterior artery in men, from 3.06 (2.76-3.36) to 2.64 (2.34-2.95), but not women, from 3.22 (2.94-3.50) to 3.25 (2.97-3.53), p = 0.01 for men vs women. Researchers should measure arterial pulsatility indices under general anaesthesia and associate them with measures of nerve function.
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Ropivacaine plasma levels following local infiltration analgesia for primary total hip arthroplasty.
We measured total and free plasma concentrations of ropivacaine following high-volume, high-dose local infiltration analgesia in 19 patients aged 65 years or over undergoing unilateral total hip arthroplasty. The patients received 180 ml ropivacaine 0.2% (360 mg), which was injected into the deep and peri-capsular tissues, the gluteal muscles and fascia lata, and the subcutaneous tissues and skin. Patients were monitored for clinical symptoms and signs of systemic local anaesthetic toxicity. ⋯ No samples reached the toxic threshold for venous ropivacaine concentration, although four patients exhibited mild symptoms consistent with local anaesthetic toxicity. One patient had episodes of complete heart block on ECG monitoring, but plasma ropivacaine levels were below toxic levels. We conclude that plasma levels for ropivacaine associated with toxicity in a volunteer population (total 2.2 μg.ml(-1) , free 0.15 μg.ml(-1) ) are not reached during local infiltration analgesia for hip arthroplasty in elderly patients.