Urinary bladder/pulmonary artery temperature ratio of less than 1 and shivering in cardiac surgical patients

BACKGROUND: Temperature gradients that normally exist between body areas may be altered as a result of heat generated by shivering. METHODS AND POPULATION: Two core thermal gradients between pulmonary artery and urinary bladder were compared with shivering in 37 coronary artery bypass graft patients. Pulmonary artery and urinary temperature were measured every 15 minutes, and shivering was evaluated electromyographically. RESULTS: Shivering developed in 28 patients (76%). With shivering the pulmonary artery/urinary bladder temperature ratio was less than 1 but in the nonshivering group was greater than 1. Correlation (r value) between pulmonary artery and urinary temperature ranged from 0.93 to 0.99. Rate pressure product was higher in the shivering group than in the nonshivering group. A pulmonary artery/urinary bladder temperature ratio of less than 1 was seen with shivering in this subset of patients. CONCLUSION: Pulmonary artery and urinary bladder temperatures are readily available clinically. The combination of a ratio of less than 1 and an increase in rate pressure product should be considered suggestive of shivering in coronary artery bypass graft patients.