Effect of low-dose propofol infusion on total-body oxygen consumption after coronary artery surgery

Comparison of metabolic monitors in critically ill, ventilated patients

OBJECTIVE

We compared the Deltatrac II, the M-COVX, and the Evita 4 metabolic monitoring devices under clinical conditions.

METHODS

A prospective simultaneous clinical comparison was performed in a general intensive care department of a tertiary university hospital in 43 ventilated, critically ill patients. The monitors were compared simultaneously. After 30 min of steady state, oxygen consumption per unit time, carbon dioxide consumption per unit time, resting energy expenditure, and respiratory quotient were recorded for the Deltatrac II; the same parameters in addition to end-tidal carbon dioxide and fraction of inspired oxygen were recorded for the M-COVX; and carbon dioxide consumption per unit time, end-tidal carbon dioxide, and fraction of inspired oxygen were recorded for the Evita 4. Pulmonary gas-exchange measurements from the Deltatrac II and resting energy expenditure and respiratory quotient from the M-COVX were obtained after 30 min. The other parameters were calculated from the last five measurements obtained at the end of the study period.

RESULTS

A good correlation was found between oxygen consumption per unit time and resting energy expenditure as obtained from the Deltatrac II and the M-COVX (r = 0.76 and 0.75, respectively; P < 0.001), but the correlation was lower between carbon dioxide consumption per unit time as obtained from the Deltatrac II and the M-COVX or Evita 4 (r = 0.67 and 0.48, respectively). Agreement between the different methods did not reach clinical acceptability, exceeding a 20% difference using the Bland-Altman statistical methods.

CONCLUSION

Poor agreement was found between the Deltatrac II and M-COVX or Evita 4 metabolic monitors, despite a good correlation between measurements, leading to the conclusion that the M-COVX and Evita 4 provide less accurate measurements of metabolic gas exchange in stable ventilated patients. These devices can be used for daily nutritional assessment and continuous monitoring, but the Deltatrac II remains the method of choice for metabolic measurement.

Quantitative analysis of the relationship between sedation and resting energy expenditure in postoperative patients

OBJECTIVE

To analyze quantitatively the relationship between sedation and resting energy expenditure or oxygen consumption in postoperative patients.

DESIGN

A prospective, clinical study.

SETTING

An eight-bed intensive care unit at a university hospital.

PATIENTS

Thirty-two postoperative patients undergoing either esophagectomy or surgery of malignant tumors of the head and neck who required mechanical ventilation and sedation for > or = 2 days postoperatively.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 133 metabolic measurements were performed. Ramsay sedation scale (RSS), body temperature, and the dose of midazolam were evaluated at the time of the metabolic cart study. All patients received analgesia with buprenorphine at a fixed dose of 0.625 microg x kg(-1) x hr(-1) continuously. Midazolam was used for induction and maintenance of intravenous sedation after admission to the intensive care unit. The initial dose was 0.04 mg x kg(-1) x hr(-1) and was adjusted to achieve a desired depth of sedation at 3, 4, or 5 on the RSS every 4 hrs. The degree of sedation was classified into three states: light sedation (RSS 2-3; n = 49), moderate sedation (RSS 4; n = 39), and heavy sedation (RSS 5-6; n = 45).

RESULTS

With increasing the depth of sedation, oxygen consumption index (mL x min(-1) x m(-2)), resting energy expenditure index (REEI; kcal x day(-1) x m(-2)), and REE/basal energy expenditure (BEE) decreased significantly. Oxygen consumption index (mean +/- SD), REEI, and REE/BEE were 151 +/- 18, 1032 +/- 120, and 1.29 +/- 0.17 in the light sedation, 139 +/- 22, 947 +/- 143, and 1.20 +/- 0.16 in the moderate sedation, and 125 +/- 16, 865 +/- 105, and 1.13 +/- 0.12 in the heavy sedation, respectively.

CONCLUSION

An increase in the depth of sedation progressively decreases in oxygen consumption index and REEI in postoperative patients.