Energy Metabolism of Thoracic Surgical Patients in the Early Postoperative Period: Effect of Posture

Study objective To determine the effect of elective thoracic surgery on energy metabolism and gas exchange and to evaluate whether the 30° sitting position would affect these variables. Design Prospective, unblinded, controlled study. Setting Surgical ICU in a university hospital. Patients Twenty-two adult patients undergoing elective pulmonary resection. Interventions Posture change from supine to 30° sitting position. Measurements and results Oxygen consumption (Vo 2 ), carbon dioxide production (VCO 2 ), respiratory quotient (RQ), and energy expenditure (EE) were measured by means of computerized indirect calorimetry before and after surgery. Heart rate and respiratory frequency were measured continuously during gas exchange measurement. Blood gases were analyzed with an automated blood gas analyzer. Preoperatively, altering position did not affect energy metabolism, gas exchange, and cardiopulmonary variables. Postoperatively, the measured EE was 116% of the expected value. Mean EE and V ˙ o 2 values for each position were higher than the preoperative values for the corresponding postures (p 2 increased only in the supine position (p<0.05). Mean percent increases in EE, V ˙ o 2 , and VCO 2 were significantly lower in the 30° sitting position than in the supine position (EE: 7.9 ± 2.7% vs 14.4 ± 2.3%; p<0.001; V ˙ o 2 : 9.0 ± 3.0% vs 16.4 ± 2.6%; p 2 :3.2 ± 2.1% vs 6.5 ± 1.4%; p Conclusions The early postoperative period of patients undergoing elective thoracic surgery is characterized by a condition of impaired gas exchange and by a hypermetabolic state. Hypermetabolism can be partly mitigated by assuming the 30° sitting position.