title: Anesthetic requirements and stress hormone responses in chronic spinal cord-injured patients undergoing surgery below the level of injury: nitrous oxide vs remifentanil.
abstract: BACKGROUND
  Nitrous oxide (N2O) and remifentanil both have anesthetic-reducing and antinociceptive effects. We aimed to determine the anesthetic requirements and stress hormone responses in spinal cord-injured (SCI) patients undergoing surgery under sevoflurane anesthesia with or without pharmacodynamically equivalent doses of N2O or remifentanil.
  
  
  METHODS
  Forty-five chronic, complete SCI patients undergoing surgery below the level of injury were randomly allocated to receive sevoflurane alone (control, n = 15), or in combination with 67% N2O (n = 15) or target-controlled infusion of 1.37 ng/ml remifentanil (n = 15). Sevoflurane concentrations were titrated to maintain a Bispectral Index (BIS) value between 40 and 50. Measurements included end-tidal sevoflurane concentrations, mean arterial blood pressure (MAP), heart rate (HR), and plasma catecholamine and cortisol concentrations.
  
  
  RESULTS
  During surgery, MAP, HR, and BIS did not differ among the groups. Sevoflurane concentrations were lower in the N2O group (0.94 ± 0.30%) and the remifentanil group (1.06 ± 0.29%) than in the control group (1.55 ± 0.34%) (P < 0.001, both). Plasma concentrations of norepinephrine remained unchanged compared to baseline values in each group, with no significant differences among groups throughout the study. Cortisol levels decreased during surgery as compared to baseline values, and returned to levels higher than baseline at 1 h after surgery (P < 0.05) without inter-group differences.
  
  
  CONCLUSIONS
  Remifentanil (1.37 ng/ml) and N2O (67%) reduced the sevoflurane requirements similarly by 31-39%, with no significant differences in hemodynamic and neuroendocrine responses. Either remifentanil or N2O can be used as an anesthetic adjuvant during sevoflurane anesthesia in SCI patients undergoing surgery below the level of injury.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonnam Natioal University Medical School, Chonnam National University, Gwangju, Korea.
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Kang
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonnam Natioal University Medical School, Chonnam National University, Gwangju, Korea.
authors.forename: Seong-Heon
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonnam Natioal University Medical School, Chonnam National University, Gwangju, Korea.
authors.forename: Seok Jai
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonnam Natioal University Medical School, Chonnam National University, Gwangju, Korea.
authors.forename: Jeong-Il
authors.initials: JI
authors.lastname: Choi
authors.affiliation: Department of Anesthesiology and Pain Medicine, School of Dentistry, Chonnam National University, Gwangju, Korea.
authors.forename: Cheol-Won
authors.initials: CW
authors.lastname: Jeong
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonnam Natioal University Medical School, Chonnam National University, Gwangju, Korea.
authors.forename: Seong Wook
authors.initials: SW
authors.lastname: Jeong
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonnam Natioal University Medical School, Chonnam National University, Gwangju, Korea.
authors.forename: Kyung Yeon
authors.initials: KY
authors.lastname: Yoo
keywords: Catecholamines; Nitrous oxide; Remifentanil; Sevoflurane; Spinal cord injuries