Remifentanil decreases sevoflurane requirements to block autonomic hyperreflexia during transurethral litholapaxy in patients with high complete spinal cord injury.

BACKGROUND: An inhaled anesthetic concentration required to block autonomic hyperreflexia (AHR) is high enough to cause severe hypotension in patients with high spinal cord injury (SCI). We determined the effects of remifentanil on the sevoflurane requirement to block AHR in SCI. METHODS: The study involved 96 patients with chronic, complete SCI scheduled to undergo transurethral litholapaxy during general anesthesia. Anesthesia was induced with thiopental, and sevoflurane concentrations in 50% nitrous oxide were adjusted to maintain a bispectral index of 40 to 50. Whether the patient develops an AHR [an increase of systolic blood pressure (SBP) >20 to 40 mm Hg] was first examined by distending the bladder with glycine solution (the first trial). Patients who developed AHR were then allocated to receive no remifentanil infusion (control, n = 31), a target-controlled plasma concentration of 1 ng/mL (n = 25), or 3 ng/mL remifentanil (n = 24). After baseline hemodynamics had recovered, the target sevoflurane and remifentanil concentrations were maintained for at least 20 minutes and the procedure was resumed (the second trial). Each target sevoflurane concentration was determined by the up-and-down method based on changes (15% increase or more) of SBP in response to the bladder distension. SBP, heart rate, and bispectral index were measured before and during the bladder distension during the trials, and plasma concentrations of catecholamines during the first trial. RESULTS: Eighty-two (85.4%) of 96 patients developed AHR during the first trial, in which 2 were excluded because of hypotension (mean arterial blood pressure <50 mm Hg) developed during target-controlled drug administration. During the second trial, the end-tidal concentrations of sevoflurane to prevent AHR were reduced to 2.6% (95% confidence interval 2.5% to 2.8%, P < 0.01) and 2.2% (2.1% to 2.4%, P < 0.0001) in the groups receiving 1 and 3 ng/mL remifentanil, respectively, in comparison with 3.1% (2.9% to 3.3%) in the control. When considering minimum anesthetic concentration (MAC) values and the contribution of 50% nitrous oxide (0.48 MAC), the combined MAC values, expressed as multiples of MAC, were 2.27, 1.98, and 1.75 in the control, 1 ng/mL remifentanil, and 3 ng/mL remifentanil groups, respectively. CONCLUSIONS: Target-controlled concentrations of 1 and 3 ng/mL remifentanil would reduce the requirement of sevoflurane combined with 50% nitrous oxide to block AHR by 16% and 29%, respectively, in SCI patients undergoing transurethral litholapaxy.

Anaesthetic requirements and stress hormone responses in acute cord-injured patients undergoing surgery of the injured spine.

BACKGROUND AND OBJECTIVE: Neuraxial anaesthesia has been shown to produce a sedative and anaesthetic-sparing effect. The purpose of the present study was to determine the effects of acute spinal cord injury on sevoflurane requirement and stress hormone responses during spinal surgery at the level of the injury. METHODS: Thirty-five patients with traumatic complete spinal cord injury undergoing spinal surgery at the level of the injury were studied. They were grouped into quadriplegics (above C7, n = 20) and paraplegics (below T1, n = 15) according to the level of injury. Patients (n = 35) with spine trauma without neurological impairment undergoing spinal surgery at the respective level served as controls. The bispectral index score was maintained at 40-50 throughout the surgery. Measurements included end-tidal sevoflurane concentrations, mean arterial pressure, heart rate, and plasma concentrations of catecholamines and arginine vasopressin. RESULTS: During the surgery, the mean arterial pressure was significantly lower in both quadriplegics and paraplegics (P < 0.05). The heart rate did not differ significantly in the quadriplegics, but was higher in the paraplegics, compared with their controls. However, end-tidal sevoflurane concentrations and bispectral index score were comparable with controls in both quadriplegics and paraplegics. Throughout the study, the plasma arginine vasopressin concentrations were not altered, although norepinephrine and epinephrine concentrations were lower in the quadriplegics. There were no significant differences in stress hormones between the groups having thoraco-lumbar surgery. CONCLUSION: Spinal cord injury neither alters the anaesthetic requirement regardless of the level of injury during spinal surgery at the level of the injury, nor enhances arginine vasopressin release. However, it blunts catecholamine responses in quadriplegics.

Bispectral index values during sevoflurane-nitrous oxide general anesthesia in women undergoing cesarean delivery: a comparison between women with and without prior labor.

BACKGROUND: An end-tidal concentration of 1% sevoflurane (1% ET(SEVO)) in 50% nitrous oxide (N(2)O) during elective cesarean delivery has been associated with bispectral index (BIS) values >60, which are associated with an increased risk of awareness. We hypothesized that BIS values during sevoflurane-N(2)O general anesthesia for cesarean delivery would be lower in women with prior labor compared with women without prior labor. METHODS: Forty patients undergoing cesarean delivery were enrolled in this observational study. One group had urgent surgery after labor (labor group, n = 20) and the other had elective surgery without labor (control group, n = 20). General anesthesia was induced with thiopental 4 mg/kg, followed by succinylcholine 1.5 mg/kg, and maintained with 1% ET(SEVO) and 50% N(2)O in oxygen. BIS values, systolic arterial blood pressure, heart rate, plasma stress hormone concentrations, Apgar scores, and postoperative analgesia variables were assessed and compared between groups. RESULTS: BIS values during the period between intubation and delivery were lower in the labor group than in the control group (P < 0.001). Plasma norepinephrine concentrations increased at delivery compared with baseline in both groups. They were higher in the labor group than in the control group both at baseline and at delivery. Systolic arterial blood pressure, heart rate, Apgar scores, surgical characteristics, and plasma concentrations of vasopressin and cortisol were not different between groups. Postoperative visual analog scale pain scores were similar between groups, while the labor group consumed less analgesics (P < 0.01) during the first 24 h after the operation. CONCLUSIONS: Prior labor was associated with lower intraoperative BIS values during sevoflurane/N(2)O general anesthesia and reduced postoperative analgesic consumption in women undergoing cesarean delivery compared with women without prior labor.