Estimation of pulmonary oxygen consumption in the early postoperative period after thoracic surgery

Abstract

SummaryLung injury, including pneumonia, can occur in the early postoperative period following thoracic surgery. Pulmonary oxygen consumption is thought to increase in patients with pulmonary infection. This study measured oxygen consumption in relationship to lung injury in the early postoperative period after thoracic surgery. Thirty-five patients who underwent thoracoabdominal oesophagectomy for oesophageal cancer were studied. Measured oxygen-consumption was obtained by indirect calorimetry and calculated oxygen-consumption was simultaneously determined by the reverse Fick method. The difference in oxygen consumption was attributed to pulmonary oxygen consumption. The difference in oxygen consumption increased to 23.1 ml.min .m )2 on postoperative day 2. In patients with pneumonia the difference in oxygen consumption increased significantly to 39.0 ml.min )1 .m )2 the day before clinical onset of pneumonia, and it increased further to 65.7 ml.min )1 .m )2 on the day that pneumonia became clinically apparent. These findings suggest that the difference in oxygen consumption may be useful for estimating the extent of lung injury and for predicting pulmonary complications in the postoperative period. In recent years, there has been increasing interest in the measurement of oxygen consumption (VO 2 ) in critically ill patients as VO 2 is related to the clinical outcome of this population. VO 2 can be measured either by indirect calorimetry, using analysis of respiratory gas exchange, or with the reverse Fick method, as the product of thermodilution cardiac output and arterial-venous oxygen content difference. Lung tissue and a considerable part of the bronchial tree are metabolically active and consume oxygen. Theoretically, the difference in oxygen content between arterial and venous blood does not include the effect of pulmonary tissue and bronchial tree oxygen uptake. Thus lung VO 2 (VO 2pulm : including that from part of the bronchial tree) should be reflected as a difference between VO 2 measured by gas exchange (VO 2meas ) and that derived using Fick's principle (VO 2Fick ). Despite this sound theoretical basis, methodological limitations can make this small difference undetectable under clinical conditions. Under carefully controlled experimental conditions, however, a constant difference between VO 2meas and VO 2Fick has been demonstrated. In previous studies [1][2][3][4][5], the difference was widely variable and some of the measurements indicated greater values with reverse Fick than with indirect calorimetry. Errors and variation of gas exchange, thermodilution cardiac output, haemoglobin and saturation measurements may accumulate, and the difference between VO 2meas and VO 2Fick may be less than the cumulative methodological error. Previous studies have demonstrated that the difference between VO 2meas and VO 2Fick , taken to represent VO 2pulm , increases once pneumonia develops [1,2,[5][6][7][8][9][10]. Accordingly, VO 2pulm might be one of the indices reflecting the extent of lung injury.In the ear...

Perioperative changes in oxygen consumption: estimations from minimal-invasive cardiac output and a-cvO2difference parallel to indirect calorimetry

“…As expected, this estimation method had poor agreement concerning absolute values when compared to indirect calorimetry, but approximate to previous studies using pulmonary artery catheters. (11,(19)(20)(21) Importantly, the estimations based on routine haemodynamic monitoring for major surgery, were shown to change in parallel with the metabolic measurements in the perioperative period. We suggest that this or similar methods could be evaluated in larger samples and related to clinical outcomes.…”

“…Time effects and repeated measurements in the same subject under changing conditions are important statistical challenges in studies involving perioperative patients. Previous studies have often used simple linear regression or correlation(9, 10, 22, 24) or Bland-Altman analysis(25) without correction for repeated measurements(11, 22, 26, 27) except for some. (21, 28) Only a few addressed the relationship between measurements over time.…”

“…Oxygen consumption calculated by the reverse Fick equation is consistently reported lower than simultaneous measurements by analysis of respiratory gas exchange. (7, 9-11, 19, 24, 26, 28, 29, 33-36) This difference or bias has been attributed to the pulmonary oxygen consumption. (35, 37, 38) However, variability of Fick-derived measurements(34, 36)and wide limits of agreement(21) has made it difficult to estimate a systematic methodological bias.…”

“…(8) The lack of absolute agreement between calorimetric and Fick-based methods has been reported previously, the latter do not include pulmonary oxygen consumption and global oxygen consumption values are usually reported around 20-40 ml min -1 m -2 lower compared to those obtained from breathing gas analysis. (9)(10)(11) Yet, if this bias remains unchanged in the intraand postoperative period, such estimations could be studied in larger samples and related to other clinical parameters and outcomes.…”

Risk prediction tool for use and predictors of duration of postoperative oxygen therapy in children undergoing non-cardiac surgery: a case-control study

“…The high risk group (score ≥ 12) included those who had thoracic surgery or had desaturation perioperatively. Children undergoing thoracic surgery (score of 11) usually need to be intubated with an endotracheal tube (score of 4) and are at high risk for postoperative oxygen therapy because they have a decrease of pulmonary functional residual capacity and high disturbance of cardiopulmonary function [ 14 – 16 ]. Provision of oxygen supplementation at the PACU and at a ward is necessary to prevent pulmonary complications.…”