Thermal suit in preventing unintentional intraoperative hypothermia during general anaesthesia: a randomized controlled trial.

BACKGROUND: Unintentional perioperative hypothermia causes serious adverse effects to surgical patients. Thermal suit (T-Balance® ) is an option for passive warming perioperatively. We hypothesized that the thermal suit will not maintain normothermia more efficiently than conventional cotton clothes when also other preventive procedures against unintentional hypothermia are used. METHODS: One hundred patients were recruited to this prospective, randomized trial. They were allocated to the Thermal Suit group or a Control group wearing conventional hospital cotton clothes. All patients received our institution's standard treatment against unintentional hypothermia including a warming mattress, a forced-air upper body warming blanket and a warming device for intravenous fluids. Eardrum temperature was measured pre-operatively. In the operating room and post-anaesthesia care unit temperatures were measured from four locations: oesophagus, left axilla, dorsal surface of the left middle finger and dorsum of the left foot. The primary outcome measure was temperature change during robotic-assisted laparoscopic radical prostatectomy. RESULTS: The temperatures of 96 patients were analysed. There was no difference in mean core temperatures, axillary temperatures or skin temperatures on the finger between the groups. Only foot dorsum temperatures were significantly lower in the Thermal Suit group. Intraoperative temperature changes were similar in both groups. In the post-anaesthesia care unit temperature changes were minimal and they did not differ between the groups. CONCLUSION: Provided that standard preventive procedures in maintaining normothermia are effective the thermal suit does not provide any additional benefit over conventional cotton clothes during robotic-assisted laparoscopic radical prostatectomy.

Propofol versus alfentanil to prevent movement responses during uterine curettage.

BACKGROUND: Propofol anaesthesia is frequently associated with movement responses in non-paralysed patients. Opioids decrease the probability of movement during noxious stimulation. Heart rate variability and frontal electromyography (EMG), which are related to subcortical functions, may be more closely related than surface electroencephalography (EEG) to movement responses to noxious stimulation. METHODS: Eighty-two patients scheduled for uterine dilatation and curettage were randomized to receive at the first intra-operative movement either a supplemental alfentanil bolus, 0.5 mg intravenously, or a supplemental propofol bolus, 0.7 mg/kg intravenously. The incidences of recurring movement during the procedure were compared between the two groups. The associations of a measure of heart rate variability (Anemon index), heart rate, EMG and two EEG variables with movement responses were evaluated. RESULTS: The incidences of recurring movement were 73% and 38% in the alfentanil and propofol groups, respectively [difference, 35%; 95% confidence interval, 9-56%; P= 0.014 between the groups). The Anemon index, heart rate, EMG and surface EEG variables displayed mainly reactive associations with movement responses. CONCLUSION: During uterine curettage under propofol-alfentanil-nitrous oxide anaesthesia, a propofol bolus of 0.7 mg/kg was more effective in preventing the recurrence of movement responses than an alfentanil bolus of 0.5 mg. Several physiological variables may be used to track significant arousal reactions, but not to predict them.

EEG spectral entropy, heart rate, photoplethysmography and motor responses to skin incision during sevoflurane anaesthesia.

BACKGROUND: Analgesia is a part of balanced anaesthesia, but direct indicators of nociception do not exist. We examined the relationship between motor reactions and physiological variables during skin incision in sevoflurane anaesthesia and hypothesized that nociception could be detected and graded by significant changes in these variables. METHODS: Thirty-one women scheduled for abdominal hysterectomy participated in the study. Anaesthesia was induced with fentanyl (1 microg kg(-1)), propofol (1 mg kg(-1)) and sevoflurane. Skin incision was performed 14 min after induction during 1.6% end-tidal sevoflurane anaesthesia without neuromuscular blockade. Electrocardiography (ECG), photoplethysmography (PPG) and electroencephalography (EEG) were registered, and a range of variables was computed from these signals. The postincision values, normalized with respect to their preincision values, of movers vs. non-movers were compared. The variables showing significant differences between movers and non-movers were used to develop a logistic regression equation for the classification of patients into movers or non-movers. RESULTS: Twenty-six patients were eligible for analysis, and 12 (46%) displayed a motor reaction to skin incision (movers). Many ECG, PPG and EEG-related variables showed significant differences between the pre- and postincision periods. The best classification performance, assessed by leave-one-out cross-validation, between movers and non-movers was achieved with the combination of response entropy of EEG, RR-interval and PPG notch amplitude. The corresponding equation yielded 96% correct classification with 90% sensitivity and 100% specificity. The classification performance of any single variable alone was considerably worse. CONCLUSION: Combination of information from different sources may be required for monitoring the adequacy of analgesia during anaesthesia.

Sevoflurane titration using bispectral index decreases postoperative vomiting in phase II recovery after ambulatory surgery.

UNLABELLED: We tested the hypothesis that titration of sevoflurane using bispectral index (BIS) of the electroencephalogram decreases postoperative nausea and vomiting and improves recovery after outpatient gynecologic laparoscopy. After propofol induction, anesthesia was maintained in all patients with sevoflurane in 65% nitrous oxide and oxygen. In the BIS-Titrated group (n = 32), sevoflurane was titrated to maintain the BIS between 50 and 60 during surgery. In the Control group (n = 30), sevoflurane was adjusted to keep hemodynamic variables within 25% of control values. The severity of pain, postoperative nausea and vomiting, and recovery variables were recorded. In the Control group, 30% of the patients had BIS <40 during surgery (versus 0 in the BIS-Titrated group). Orientation and ability to drink were achieved earlier in the BIS group (P < 0.05). At 30 min after cessation of nitrous oxide, patients in the BIS group performed better in the psychomotor recovery test (P < 0.01). In Phase II recovery room, these patients had significantly less vomiting than the patients in the Control group (16% versus 40% of the patients, respectively, P < 0.05). No differences were found in times to achieve home readiness. IMPLICATIONS: In patients undergoing outpatient gynecologic laparoscopy, the monitoring of bispectral index decreases vomiting in Phase II recovery room, but it has no effect on the time to achieve home readiness.

Transient hyperdynamic response associated with controlled hypocapneic hyperventilation during sevoflurane-nitrous oxide mask induction in adults.

UNLABELLED: We assessed hemodynamic variables during sevoflurane face mask anesthetic induction in female ASA physical status I or II patients. Anesthesia was induced with a single-breath inhalation method with 8% sevoflurane in 50% nitrous oxide in oxygen. Thirty patients were randomized either to breathe spontaneously (SB group, n = 15) or to receive controlled ventilation (CV group, n = 15) for 6 min after the loss of consciousness. Noninvasive blood pressure and heart rate (HR) were recorded at 1-min intervals. Mean +/- SD HR increased from 83+/-18 to 112+/-24 bpm at 4 min in the CV group (P < 0.001 between groups and within group compared with baseline). Mean arterial pressure increased from 97+/-9 to 106+/-26 mm Hg at 4 min in the CV group, which was significantly higher than that in the SB group (P < 0.01). In the SB group, mean arterial pressure decreased significantly, from 96+/-8 to 78+/-13 mmHg, at 6 min (P < 0.001), and HR remained unchanged. Therefore, hyperventilation should be avoided during the induction of sevoflurane anesthesia via a mask. IMPLICATIONS: In this randomized, prospective study, we found that controlled hypocapneic hyperventilation delivered manually during sevoflurane/ N2O/O2 mask induction was associated with a significant transient hyperdynamic response. This kind of hemodynamic arousal can be detrimental to many patients and can be avoided by conducting sevoflurane mask induction with unassisted spontaneous breathing.

The effect of skin incision followed by alfentanil on catecholamine levels and on the T-wave amplitude of ECG during isoflurane anaesthesia.

Haemodynamic, ECG T-wave amplitude and plasma potassium changes and plasma catecholamine responses to skin incision followed by alfentanil were studied in 24 ASA I patients. Propofol and vecuronium were used without anticholinergics for induction of anaesthesia followed by isoflurane in 02/air. End-tidal isoflurane concentration was kept constant (0.7%) for 30 min before the skin incision. Five min after the skin incision alfentanil 30 mu g kg-1 was given. Blood samples for catecholamines and plasma potassium concentrations were drawn from right ventricle of the heart one minute before and after the skin incision and two minutes after alfentanil. Heart rate, systolic and diastolic arterial pressures increased after the skin incision (P < 0.001), and decreased after alfentanil (P < 0.001). Plasma adrenaline and noradrenaline concentrations increased slightly after the skin incision (P < 0.05 and P < 0.01, respectively). Noradrenaline levels continued to increase after alfentanil (P < 0.001) despite totally abolished haemodynamic responses to the skin incision. ECG T-wave amplitude changes, measured as R/T ratio, did not correlate to the changes in plasma catecholamine levels: both rapid increases and decreases in R/T ratio were seen. No plasma potassium changes were seen during the trial. T-wave changes, occurring in seconds after the skin incision, are probably produced by a direct catecholamine release from cardiac sympathetic nerve endings.

The effect of atropine on the T-wave amplitude of ECG during isoflurane anaesthesia.

The effect of bolus dose of atropine (20 micrograms kg-1) on the R/T-wave amplitude ratio of electrocardiogram was studied in 12 patients during isoflurane anaesthesia at electroencephalogram burst suppression level (mean ET of isoflurane 1.8 vol-%). The amplitude ratio was measured before, 1, 2, 5 and 10 min after atropine. Change was measured as decibels and 95% confidence intervals were calculated. The amplitude of T-wave flattened significantly after atropine. It is concluded, that the ECG T-wave amplitude reflects the balance of sympathetic and parasympathetic nervous activity during isoflurane anaesthesia. The use of the decibel transformation and confidence intervals seems to be a relevant method to interpret changes in physiologic measures during anaesthesia.