Thermogenesis after surgery: effect of perioperative heat conservation and epidural anesthesia

Comparative Study of the Effect of Warming at Various Temperatures on Biochemical, Hematologic, and Hemodynamic Parameters During Spinal Fusion Surgery Under Intravenous Anesthesia

BACKGROUND

Perioperative inadvertent hypothermia (PIH) commonly occurs after major surgical procedures under local or general anesthesia and increases the risk of complications such as organ failure, hypoperfusion, and peripheral vasoconstriction, as well as adverse postoperative outcomes, such as wound infection and increased surgical bleeding.

OBJECTIVES

We hypothesized that the intra-operative warming may affect these complications and thus, we aimed to compare the most appropriate temperature of the warmer to decrease patients' complications.

METHODS

The present randomized clinical trial investigated 90 patients undergoing total intravenous anesthesia in posterior spinal fusion surgery, randomly divided into two groups of 45. The warmer was set at 38°C for group "A" during surgery and at 40°C for group "B." Patient's demographic characteristics, the serum level of hemoglobin, hematocrit, and platelet counts, mean core temperature, systolic blood pressure (BP), heart rate, and respiratory rate were recorded before and after the surgery. Variables were compared between the two groups at three time intervals (during induction, during operation, and during recovery).

RESULTS

The mean temperature was not different between the two groups at the three time intervals. Other laboratory serum tests, vital signs, and oxygen consumption were maintained within the normal range although they did not improve significantly in two groups at the three time intervals.

CONCLUSIONS

There was no significant difference in warming of the patients during operation at 38 or 40°C to prevent hypothermia-induced complications during induction, operation, and recovery.

Postanaesthetic shivering: epidemiology, pathophysiology, and approaches to prevention and management

Along with nausea and vomiting, postanaesthetic shivering is one of the leading causes of discomfort for patients recovering from general anaesthesia. The distinguishing factor during electromyogram recordings between patients with postanaesthetic shivering and shivering in fully awake patients is the existence of clonus similar to that recorded in patients with spinal cord transection. Clonus coexists with the classic waxing and waning signals associated with cutaneous vasoconstriction (thermoregulatory shivering). The primary cause of postanaesthetic shivering is peroperative hypothermia, which sets in because of anaesthetic-induced inhibition of thermoregulation. However, shivering associated with cutaneous vasodilatation (non-thermoregulatory shivering) also occurs, one of the origins of which is postoperative pain. Apart from causing discomfort and aggravation of pain, postanaesthetic shivering increases metabolic demand proportionally to the solicited muscle mass and the cardiac capacity of the patient. No link has been demonstrated between the occurrence of shivering and an increase in cardiac morbidity, but it is preferable to avoid postanaesthetic shivering because it is oxygen draining. Prevention mainly entails preventing peroperative hypothermia by actively rewarming the patient. Postoperative skin surface rewarming is a rapid way of obtaining the threshold shivering temperature while raising the skin temperature and improving the comfort of the patient. However, it is less efficient than certain drugs such as meperidine, clonidine or tramadol, which act by reducing the shivering threshold temperature.

Uncoupling protein-2 and -3 messenger ribonucleic acids in adipose tissue and skeletal muscle of healthy males: variability, factors affecting expression, and relation to measures of metabolic rate

Mitochondrial uncoupling protein-2 and -3 (UCP2 and UCP3) may be involved in the modulation of resting metabolic rate and energy balance. To investigate their variability, the influence of this on the variability of energy expenditure, and potential regulatory factors of the expression of the corresponding genes, we measured their messenger ribonucleic acids (mRNAs) in muscle and white adipose tissue of lean, healthy men and correlated the abundance of these mRNAs (attomoles per microg total RNA) with measures of resting metabolic rate, hormone levels (thyroid hormones, insulin, glucagon, leptin, and catecholamines), and fuels potentially involved in energy balance regulation. We also investigated whether the thiazolidinedione, troglitazone, stimulates UCP2 and UCP3 mRNA levels to follow up on the observation that this antidiabetic drug increases the levels of expression in cultured cells. We found UCP2 and UCP3 mRNA levels to be highly variable and poorly correlated with measures of energy expenditure and with most factors affecting energy balance. Only nocturnal urinary norepinephrine excretion could explain a significant fraction of the variability in both UCP2 and UCP3 expression in muscle, but not adipose tissue. Thyroid hormone and norepinephrine excretion were found to contribute to the variability of resting metabolic rate, but this could not be explained by an effect on UCP mRNAs. Troglitazone affected neither the expression of UCPs nor the hormones or the measures of metabolic rate investigated. In conclusion, our results show that the expression of UCP2 and UCP3 genes is quite variable in healthy males and that this variability does not explain that in resting energy expenditure, and suggest that sympathetic activity is an important potential regulator of the expression of these proteins in skeletal muscle. However, the data do not support the concept that regulation of the expression of these genes is the most important level of control of UCP3 and UCP2 functions, and other levels of control have to be invoked.