A Methodology to Explore Ventilatory Chemosensitivity and Opioid-Induced Respiratory Depression Risk.

PURPOSE Reported incidence of postoperative opioid-induced respiratory depression (OIRD) range from 0.5 to 41% and is not reliably predicted by traditional risk factors. This study tests a new methodology to investigate ventilatory chemosensitivity as a new potential risk factor and explore OIRD distribution across sleep and wakefulness. METHODS Preoperative patient ventilatory chemosensitivity was quantified by hypercapnic ventilatory responses with (HCVRREMI, effect site concentration 0.7 or 2.0 ng/ml) and without (HCVRBL) remifentanil during hyperoxia and hypoxia. Postoperative opioid consumption was recorded during hospital stays. OIRD frequency was the primary outcome of the study, detected as incidences of respiratory rate 50 mmHg, and central and obstructive apnea/hypopnea. Sleep stages were recorded until the first postoperative morning to determine the OIRD sleep distribution as the secondary outcome. RESULTS The methodology was feasible in implementation and posed no obstacles to standard care. In the nine patients studied (2 females, mean age 65 ± 7.5 years), remifentanil depressed HCVR to a highly variable degree. High OIRD frequency was generally observed with lower HCVRREMI. OIRD predominantly occurred during light sleep. CONCLUSION This study supports ventilatory chemosensitivity as an important predictor of OIRD, lending a new perspective to classify risk for OIRD and detailing a methodology in which to pursue this investigation for future studies. (ClinicalTrials.gov number NCT04047550).