Selective unilateral spinal anaesthesia for outpatient knee arthroscopy using real-time monitoring of lower limb sympathetic tone.

Selective unilateral spinal anaesthesia is a useful approach for ambulatory lower limb surgery because it allows more rapid home discharge compared to bilateral block. Infrequent use is due to the fact that obtaining selective unilateral block can be difficult, requiring attention to technique. We present a method with a high success rate that uses real-time monitoring of the sympathetic activity of the legs. In this prospective study, 56 patients scheduled for ambulatory knee arthroscopy had spinal anaesthesia in the lateral recumbent position, with hyperbaric bupivacaine 0.5% injected at 0.33 ml/min up to a maximum dose of 5 mg. Sympathetic tone of the legs was monitored by plantar electrical dermal resistance. The clinical effect was assessed by loss of sensation and muscle strength. The haemodynamic course and adverse events were monitored. The motor block was strictly unilateral in 55 patients (98%) and the sensory block was strictly unilateral in 53 patients (94%). The median decrease in systolic blood pressure was 6 mmHg. The time from subarachnoid puncture to arrival in the recovery room was 73±23 minutes; the duration of stay in the recovery room was 70±30 minutes. Three patients with a well-established block of adequate extent required conversion to general anaesthesia because of tourniquet pain. Urinary retention only occurred in the sole patient with bilateral block. This method of performing selective unilateral spinal anaesthesia using real-time monitoring of sympathetic tone of the legs has a high success rate and is associated with rapid eligibility for home discharge.

Surgical pleth index-guided remifentanil administration reduces remifentanil and propofol consumption and shortens recovery times in outpatient anaesthesia.

BACKGROUND: The surgical pleth index (SPI) is an index based on changes in plethysmographic characteristics that correlate with the balance between the sympathetic and parasympathetic nervous system. It has been proposed as a measure of the balance between nociception and anti-nociception. The goal of this study was to test whether it could be used to titrate remifentanil in day-case anaesthesia. METHODS: A total of 170 outpatients were given total i.v. anaesthesia with propofol and remifentanil. The patients were randomized to have the remifentanil dose either adjusted according to the SPI (SPI group) or to clinical parameters (control group). The propofol dose was adjusted according to entropy in both groups. The consumption of anaesthetic drugs, recovery times, and complications were compared. RESULTS: The mean [standard deviation (SD)] remifentanil and propofol infusion rates in the SPI and control groups were 0.06 (0.04) vs 0.08 (0.05) µg kg(-1) min(-1) and 6.0 (2.1) vs 7.5 (2.2) mg kg(-1) h(-1), respectively (both P<0.05). The mean (SD) times to eye opening were -0.08 (4.4) and 3.5 (4.3) min and to extubation were 1.2 (4.4) and 4.4 (4.5) min in the SPI and control groups, respectively (both P<0.05). There was no difference between the groups with regard to satisfaction with the anaesthetic or intensity of postoperative pain. No patient reported intraoperative awareness. CONCLUSIONS: Adjusting the remifentanil dosage according to the SPI in outpatient anaesthesia reduced the consumption of both remifentanil and propofol and resulted in faster recovery.