Effect of positive end expiratory pressure on thermo-regulatory function during general anesthesia in patients addicted to smoking

Abstract

Objective To investigate the effect of positive end expiratory pressure (PEEP) on thermo-regulatory function during general anesthesia in patients addicted to smoking. Methods Twenty adult male ASA Ⅰ or Ⅱ patients who had been smoking more than or equal to 10 cigarettes per day for more than or equal to 6 years were studied. The patients underwent intra-abdominal surgery under general anesthesia and were randomly divided into 2 groups ( n = 10 each): control group (group C) and PEEP group (group P). Anesthesia was induced with propofol, fentanyl and vecuronium and maintained with inhalation of 1%-2% isoflurane and continuous iv infusion of remifentanil and vecuronium. The patients were mechanically ventilated after tracheal intubation. In group P PEEP of 10 cm H2O was added. Temperature probe was inserted into the lower segment of esophagus and placed on the anterior chest wall, medial surface of thigh anterior surface of forearm and palmar surface of the tip of index finger. Mean skin temperature (TMSK) was calculated according to Roberts. MAP, HR, TES, TMSK and the difference between TES and TMSK (TES-MSK) were recorded before induction of anesthesia (T0 ,baseline) and every 30 min after tracheal intubation. Esophageal temperature was taken as threshold of thermo-regulatory peripheral vasoconstriction when the difference between forearm and finger tip temperature = 0 ℃. The gain in the threshold was calculated according to Sessler. Results TES and TES-MSK significantly decreased,while TMsK increased after tracheal intubation in both groups ( P ＜ 0.05). There was no signifieant difference in TES, TMSK, TES-MSK, MAP, HR, the threshold of vasoconstriction and gain between the 2 gronps ( P ＞ 0.05). Conclusion PEEP cannot improve thermo-regulatory function during general anesthesia in smoking-addicted patients. Key words: Respiration, artificial; Body temperature regulation; Smoking; Anesthesia,general