Factors affecting pain assessment scores in patients on mechanical ventilation

To determine how respiratory status and other aspects of the patients' condition affect pain assessments.

Pain was assessed in 20 patients aged ≥20 years who underwent cardiovascular surgery, and required postoperative mechanical ventilation in an intensive care unit using the Behavioral Pain Scale (BPS). A BPS score of ≥6 (pain) versus <6 (no pain) was the dependent variable for determining the effect on pain.

Multiple logistic regression analysis showed that in 99 observations made at rest, pre- and post-turning and pre- and post-tracheal suctioning, the BPS score was significantly affected by gender, the Acute Physiology and Chronic Health Evaluation (APACHE) II score, Richmond Agitation-Sedation Scale score, PaCO₂, and HCO₃^-. The associations between BPS scores and APACHE II scores and HCO₃^- demonstrated that pain results from biological responses to invasion. Increases in PaCO₂ affecting only the total BPS score suggests that PaCO₂ is associated with other pain responses, regardless of respiratory status.

The BPS score was significantly associated with disease severity and ventilatory capacity, demonstrating a need to examine pain assessment methods tailored to the severity of underlying disease, degree of respiratory failure and other aspects of individual patient's condition for effective pain management.