Oesophageal temperature monitoring during general anaesthesia

Abstract EN

This study aimed to demonstrate the oesophageal temperature changes with the time during general anaesthesia for the routine surgical work, and to see the effects of patient’s gender or age, and the effects of neuromuscular blockade on these changes, also to compare oesophageal temperature changes with mean skin temperature changes during general anaesthesia, and to assess the problem of unintentional intraoperative hypothermia with its complications in the postanaesthetic recovery room.

Fifty three ASA (I-II) unpremedicated randomly selected patients (26 males and 27 females) undergoing different routine elective surgical operations under general anaesthesia in the University Hospital Medical College in Baghdad between August -September 2001.

Anaesthesia was induced by intravenous (iv) thiopentone 4-5 mg / kg and fentanyl 1-2 g / kg, and maintained with either 2-3 % halothane in oxygen without neuromuscular blockade in spontaneously ventilated by mask (4 patients)or manually assisted ventilation through a tube in 17 patients, while it was maintained by 0.

5-1% halothane in oxygen and the muscle paralysis was done by either suxamethonium 1 mg / kg bolus iv followed by infusion of 4-10mg\min.

of 0.

1% suxamethonium solution to 16 patients, or by iv pancuronium 0.

1 mg /kg (16patients), then endotracheal intubation was done and ventilation was mechanically controlled.

Neostigmine 40 g / kg and atropine 20 g / kg were given iv at the ends of operation to reverse residual blockade of pancuronium where it was given.

Monitoring of the oesophageal and skin temperatures was started ten minutes after induction of anaesthesia as a baseline, repeated every ten minutes until the end of halothane administration and the last measurements were taken just before discharging the patient from the recovery room, other vital signs were also monitored like noninvasive blood pressure, ECG, and pulse oximetry at the perioperative periods.

The means for the ambient temperature and the relative humidity of the operating theatre were also recorded.

Postanaesthetic shivering when observed, was scored (0-3), pulse oximetry was used to assess oxygenation status.

The postanaesthetic recovery time was measured from the moment of closing the halothane vaporizer at the end of the operation until the patient got 10 degrees according to Aldrete &Kronlik postanaesthetic recovery score.

Oesophageal temperature increase above the baseline occurred in 7.

54 % (4 / 53) of the patients with mean increase was 1.035°C ± 0.797 (SD) range was 0.2-3.

4°C, while the temperature decrease below the baseline occurred in 92.

45 % ( 49 / 53) of the patients, with mean decrease was 1.7 °C ± 0.

67 (SD), the range was 1 - 3.4 °C .The decrease became significant ( P < 0.

05) at 20-150 minutes after induction in oesophageal temperature and at 30-140 minutes in mean skin temperature.

At all time periods after induction the oesophageal temperature readings were significantly (P < 0.

05) above those of the mean skin temperature.

Changes in oesophageal temperature showed no significant difference between males and females, but there was significant (P < 0.

05) difference between different age groups up to 90 minutes after induction, however significant differences were seen between patients who had spontaneous or assisted ventilation with 2-3 % halothane in oxygen, and those who received muscle relaxants in addition to 0.

5-1% halothane in oxygen with controlled ventilation The incidence of unintentional intraoperative hypothermia (decrease 1-3 °C in core temperature) was 43.

39 % (23 / 53), and from the total hypothermic patients; females formed 69.

56 % (16 / 23), males were 30.

43 % ( 7 / 23) .

Hypothermia was more frequent 39.13 % (9/23) in the age group 15 years and below.

Postanaesthetic shivering was seen in 37.

73 % (20 / 53) from total patients, and from total shivering patients; females formed 55% (11/20) , males were 45 % ( 9 / 20).

The highest percentage of shivering was 40 % (8 / 20) and seen within the age 16-25 years, while the lowest was 5 % (1 / 20), and found within the age group above 40 years.

From the total shivering patients 50 % (10/20) had ENT operations, 30% (6/20) who had orthopaedic operations, and 20 %(4 / 20) who had general surgery operations.

Severe shivering grade 3 occurred in 55% (11 / 20) of all the shivering patients causing hypoxaemia (SaO2 < 90 %) diagnosed by pulse oximetry in 40% (8 / 20) of the total shivering patients.

Irritable patients were seen in 60% (12/20) of these shivering where hypoxaemia occurred in 58.3% (7 / 12) of the irritable patients.

The mean postanaesthetic recovery time in hypothermic patients was 31.47 minutes 15.

41(SD), which was significantly (P < 0.

01) more than that in the nonhypothermic patients which was 18.

76 minutes 9.16 (SD).

In conclusion, monitoring of oesophageal temperature during routine practice of general anaesthesia can early detect the body core temperature changes especially the intraoperative unintentional hypothermia, which should be prevented to avoid its complications