Risk factors for shivering during caesarean section under spinal anaesthesia. A prospective observational study

Shivering during caesarean section (CS) under spinal anaesthesia is a common phenomenon. It could not only alter patient's physiology by increasing oxygen consumption but also affect the parturient's experience of childbirth. Shivering is thought to be associated with intraoperative hypothermia, but the risk factors and exact mechanism remain unclear.

We conducted a prospective, observational study to examine the potential risk factors for intraoperative shivering, including anxiety levels. Two hundred patients undergoing elective CS under spinal anaesthesia were recruited. Parturient anxiety levels were evaluated using the State-Trait Anxiety Inventory (STAI) questionnaire. Age, weight, height, BMI, anxiety level, number of previous deliveries, sensory block level, level of education, temperature difference during surgery and American Society of Anesthesiologists score were investigated as potential risk factors. Stepwise logistic regression was used to assess the predictors for shivering.

Data from 155 parturients were analysed. Shivering incidence was 21.9% (34 parturients). The statistical model predicted 8.5% of a shivering incidence variability (R-square Nagelkerke = 0.085). Out of all measured variables, only the number of previous deliveries [(W) = 4.295 Exp(B) = 0.562 P < .05] and STAI-X1 [(W) = 4.127 Exp(B) = 1.052 P < .05] were significant. In our model, the risk of shivering decreased by 44% with every previous delivery and increased by 5.2% with each 1-point increase in STAI-X1.

We failed to prove a strong correlation between the measured variables and shivering. Our findings, however, support the hypothesis, that to a limited extent, anxiety promotes shivering during CS.