The relationship between sedative infusion requirements and permissive hypercapnia in critically ill, mechanically ventilated patients.
OBJECTIVE
Permissive hypercapnia (PH) may result from mechanical ventilation (MV) strategies that intentionally reduce minute ventilation. Sedative doses required to tolerate PH have not been well characterized. With increased attention to lung-protective ventilation, characterization of sedative requirements with PH and determination of sedative dose changes with PH are needed.


METHODS
Retrospective analysis.


METHODS
Tertiary care university hospital.


METHODS
We evaluated 124 patients randomized in a previous study to either propofol or midazolam. PH was employed in ten of 60 patients receiving propofol and 13 of 64 patients receiving midazolam.


METHODS
We analyzed dosing of propofol and midazolam in patients undergoing PH through a retrospective analysis of an existing database on MV patients. Total sedative (propofol and midazolam) dose was recorded for the first three days of MV. Linear regression analysis (dependent variable: sedative dose) was used to analyze the following independent variables: PH, age, gender, daily sedative interruption, type of respiratory failure, presence of hepatic and/or renal failure, Acute Physiology and Chronic Health Evaluation II score, morphine dose, and Ramsay sedation score.


RESULTS
Propofol dose was higher in PH patients (42.5+/-16.2 vs. 27.0+/-15.3; p=.02); Midazolam dose did not differ between PH and non-PH patients (0.05 [0.04, 0.14] vs. 0.05 [0.03, 0.07]; p=.17). By univariate linear regression analysis, propofol dose was significantly dependent on PH, age, type of respiratory failure, morphine dose, and Ramsay score, with PH (regression coefficient, 11.7; 95% confidence interval, 1.2-22.7; p=.03) and age (regression coefficient, -0.3; 95% confidence interval -0.5 to -0.08; p=.005) remaining significant by multivariate linear regression. By univariate linear regression analysis, midazolam dose was dependent on age, morphine dose, and Ramsay score, but not PH; only morphine dose (regression coefficient, 0.44; 95% confidence interval, 0.22-0.67 for a 0.1-unit increase in morphine dose; p<.001) was significant by multivariate linear regression.


CONCLUSIONS
We conclude that higher doses of propofol but not midazolam are required to sedate patients managed with PH.
Vinayak
Ajeet G
AG
Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, IL, USA.
Gehlbach
Brian
B
Pohlman
Anne S
AS
Hall
Jesse B
JB
Kress
John P
JP
D000328:Adult; D000368:Aged; D016638:Critical Illness; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006935:Hypercapnia / Q000209:etiology / Q000517:prevention & control*; D006993:Hypnotics and Sedatives / Q000008:administration & dosage* / Q000627:therapeutic use; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial / Q000009:adverse effects*; D012131:Respiratory Insufficiency / Q000628:therapy*; D012189:Retrospective Studies; D016896:Treatment Outcome
D006993:Hypnotics and Sedatives