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.
Yoo
Kyung Y
KY
Department of Anesthesiology and Pain Medicine, Chonnam National University Medical School, 8 Hak-dong, Gwangju 501-757, South Korea. kyyoo@jnu.ac.kr
Jeong
Cheol W
CW
Kim
Seok J
SJ
Jeong
Seong T
ST
Kim
Woong M
WM
Lee
Hyung K
HK
Oh
Kyung J
KJ
Lee
Jong Un
JU
Shin
Min H
MH
Chung
Sung S
SS
D000328:Adult; D020211:Autonomic Dysreflexia / Q000188:drug therapy* / Q000503:physiopathology / Q000628:therapy; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008096:Lithotripsy / Q000379:methods*; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage*; D008875:Middle Aged; D010880:Piperidines / Q000008:administration & dosage*; D000077208:Remifentanil; D000077149:Sevoflurane; D013119:Spinal Cord Injuries / Q000188:drug therapy / Q000503:physiopathology / Q000628:therapy; D013904:Thoracic Vertebrae; D014521:Urethra / Q000187:drug effects
D008738:Methyl Ethers; D010880:Piperidines; D000077149:Sevoflurane; D000077208:Remifentanil