Background: Respiratory depression is the most feared opioid-related side-effect yet research on the topic is sparse. We evaluated changes in respiratory parameters during parenteral opioid titration for cancer pain to determine if opioid titration was associated with evidence of hypoventilation. The primary outcome measure was to measure changes in end-tidal CO(2) (ET-CO(2)) during opioid titration to pain control.
Methods: Subjects with severe cancer pain admitted for parenteral opioid titration for poorly controlled pain were eligible. Those who were oxygen dependent were excluded. ET-CO(2), O(2) saturation, respiratory rate (RR), and vital signs were monitored daily until pain control was achieved.
Results: 30 patients completed the study of which 29 are reported. The mean ET-CO(2) at initial evaluation was 33.39 -/+ 5.0 and 34.79 -/+ 5.7 mmHg at pain control (P =0.14, 95% CI -0.5 to 3.3). None had an ET-CO(2) > or =50 mmHg. All maintained O(2) saturation > or = 92%. RR dropped transiently below 10/minute in two subjects.
Conclusions: Parenteral opioid titration for relief of cancer pain was not associated with respiratory depression as demonstrated by significant changes in ET-CO(2) or oxygen saturation in non-oxygen dependent cancer patients.