Predictors of pain during invasive medical procedures.

This study explored whether cardiovascular response and heart rate response to surgical stress were related to pain during percutaneous transcatheter diagnostic and therapeutic peripheral vascular and renal interventions. One hundred twenty-nine patients, 61 men and 68 women, provided repeated measures of pain on a 0 to 10 scale every 15 minutes during and at the end of the procedure. We tested 2 hypotheses: (1) baseline blood pressure and heart rate predict pain report and (2) initial procedural changes in blood pressure and heart rate predict pain report. Results of regression analysis showed that heart rate response is a significant independent predictor of pain regardless of whether pain is defined as the maximum level during the procedure or as the pain level at the end. Baseline pain, anxiety, and heart rate were significantly correlated to maximum pain report but did not enter the final model as significant independent predictors. We also found that patients whose heart rate increased during surgery from their baseline level had significantly lower pain report than those who did not show an increase. Neither baseline blood pressure nor blood pressure changes were significant predictors of pain level. Thus, we concluded that heart rate response is a powerful negative predictor of procedural pain even after controlling for baseline variables, type of procedure, and units of pain medication.