BIS response to tamponade and dobutamine in swine varies with hypnotic/opiate ratio.

OBJECTIVES: This study in swine assessed BIS stability in response to decreases and increases in cardiac output under two propofol/remifentanil dosage combinations, both producing the same depth of surgical anaesthesia. METHODS: Eight anaesthetized-paralyzed ventilated adult swine were studied using a random-order cross-over design. Four received a P low/R high combination (P, 8.4+/-0.9 mg/kg/h; and R, 0.54+/-0.02 microg/kg/min) and then a P high/R low combination (P, 26.7+/-2.1mg/kg/h; and R, 0.34+/-0.01 microg/kg/min). The other four had these two combinations in the reverse order. Under each P/R combination, and after a 60-minutes steady state, a 15-minute stable cardiac tamponade was induced by intrapericardial gelatine infusion. Then, after returning to pre tamponade condition, a 15 minutes period with dobutamine was allowed. RESULTS: Tamponade induced falls in average mean arterial pressure (MAP) (from 79+/-18 to 47+/-9 mm Hg; p<0.05) and cardiac output (Qc) (from 1.90+/-0.46 l/min to 1.20+/-0.38 l/min, p<0.05). Conversely, dobutamine increased both MAP and Qc (p<0.05). During each type of hemodynamic challenges, changes in anaesthesia depth as assessed by BIS differed dramatically between the two drug combinations, despite observing the same percent change in P and R effect-site concentration. With P high/R low and tamponade, BIS fell from 65+/-5 to 29+/-10 (p<0.05); dobutamine produced opposite effects. With P low/R high, in contrast, BIS was not influenced by either of the hemodynamic challenges. CONCLUSION: Conversely to a high propofol/low remifentanil combination, a low propofol/high remifentanil combination allows constant anaesthetic depth in the face of haemodynamic challenges.

[Importance of plasma (histamine and tryptase) and urinary (methylhistamine) in peri-anesthetic anaphylactic and/or anaphylactoid reactions]. / Intérêt des médiateurs plasmatiques (histamine et tryptase) et urinaire (méthylhistamine) lors des réactions anaphylactiques et/ou anaphylactoïdes peranesthésiques.

Histamine and tryptase, released during anaphylactoid reactions in anaesthesia, can be measured out by radioimmunoassay, provided that their own pharmacokinetic is respected. For two years, we have used sample kits in order to realize the measuring out of these mediators. The aim of this study was to evaluate the interest of these mediators within investigational procedures for anaphylactoid reactions. Eleven anaphylactoid reactions were observed (0,03%). The early blood samples (the first ten minutes following onset of the reaction) were made only in 36% of the cases. Within the serious reactions (grade III), the raising of tryptase indicates the involvement of mast-cell activation. Within minor clinical reactions (grade I), plasma histamine and urinary methylhistamine were the only mediators detected. In an anaphylactic reaction of grade II, which happened after the administering of vecuronium, tryptase was not detected. Therefore, these mediators give the anaesthetists the possibility to prove quickly the severity of the reactions and to direct the investigations very early towards the right way.