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(Using a Central Venous Catheter) and Measured by Indirect Calorimetry J Anesth (2008) 22:163–166 DOI 10.1007/s00540-007-0588-9 Clinical reports Comparison of oxygen consumption calculated by Fick’s principle (using a central venous catheter) and measured by indirect calorimetry 1,2 1 1 1 1 CHIAKI INADOMI , YOSHIAKI TERAO , KAZUNORI YAMASHITA , MAKOTO FUKUSAKI , MASAFUMI TAKADA , 2 and KOJI SUMIKAWA 1 Department of Anesthesia, Nagasaki Rosai Hospital, Sasebo, Japan 2 Division of Anesthesiology, Department of Translational Medical Science, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan Abstract suggested the possibility of direct complications using We investigated the clinical usefulness of the Fick method a PAC [5–8]. It was also reported that there was a cv using central venous oxygen saturation (S O2) and cardiac higher rate of pulmonary embolism in a group with a output (CO) measured by pulse dye. densitometry (PDD) for PAC compared with a group undergoing standard ther- monitoring oxygen consumption (V ). This prospective clini- O2 apies including the use of a central venous catheter cal study was performed in 28 mechanically ventilated. post- (CVC) [8]. operative patients after major abdominal surgery. V was O2 Reinhart et al. [9] suggested that central venous determined by two methods, i.e., the Fick method and indirect oxygen saturation (Scv ) with a CVC was clinically calorimetry. The Fick method was employed using CO O2 measured by PDD and Scv obtained from a central venous interchangeable with the mixed venous oxygen satura- . O2 tion (SvO ) obtained with a PAC. CVCs are more fre- catheter (CVC). VO2 measured by indirect calorimetry was 2 quently and easily available in all clinical settings averaged .for 15 min. Fifty-six sets of measurements were per- formed. V values determined by the Fick method were sig- compared with PACs. Although indirect calorimetry is O2 . nifi cantly lower than those measured by indirect calorimetry a precise method to determine V , portable metabolic − − O2 (110 ± 29 vs 148 ± 28 ml·min 1·m 2; P < 0.01). Bland and Altman carts are not routinely available for all postoperative analysis showed that the mean bias and precision were patients because of the high cost. −1 −2 −1 −2 33 ml·min ·m and 32 ml·min ·m , respectively.. The correla- We assessed the clinical usefulness and equivalence tion between the two measurements of V was weak . O2 of V determined by the Fick method (using a combi- (r2 = 0.145; P = 0.0038), indicating that the Fick method using O2 nation of Scv with CVC and pulse dye densitometry PDD and Scv is not clinically acceptable for the monitoring O2 . O2 of V . [PDD]) in comparison with indirect calorimetry in O2 mechanically ventilated postoperative patients. Key words Oxygen consumption · Fick method · Indirect calorimetry · Central venous oxygen saturation Patients, materials, and methods This study was approved by the Institutional Ethics Introduction Committee, and informed written consent was obtained from each patient. We studied 28 patients (18 men . The measurement of oxygen consumption (V ) in and 10 women) who required mechanical ventilation O2 critically ill patients is important for the assessment of overnight postoperatively. The study’s inclusion criteria therapeutic management. Some previous studies have were as follows: (a) elective major abdominal surgery; (b) American Society of Anesthesiologists physical compared indirect calorimetry. and the Fick method for the measurement of V [1–4]. Samples obtained status I to III; and (c) age more than 20 years. The exclu- O2 with a pulmonary artery catheter (PAC) were used to sion criteria were: (a) fractional inspired oxygen (FI ) . O2 calculate V by the Fick method, whereas some studies more than 0.6; (b) air leaks from the endotracheal tube; O2 and (c) renal failure. Each patient had a CVC (Micro- needle Seldinger kit, double-lumen catheter, 0.4 ml in Address correspondence to: C. Inadomi This work was presented, in part, at the 13th World Congress the proximal lumen (17 G) and 0.6 ml in the distal lumen of Anesthesia, Paris, France, April 17–23, 2004. (14 G); Argyle; Nippon Sherwood Medical Industries, Received: January 4, 2007 / Accepted: October 29, 2007 Tokyo, Japan) inserted via the right subclavian vein for 164 C. Inadomi et al.: Fick method using central venous catheter the measurement of central venous pressure and for were used to examine the relationship. We considered receiving total parenteral nutrition. The CVC position P < 0.05 to be signifi cant. Sample size was determined was confi rmed by a chest radiograph. on the basis of a previous work [3], which indicated that, All patients were transported from the operating with 28 patients, there. was a power of 80% to detect a room to the intensive care unit (ICU). They were 75% difference in V between the two methods at a O2 intubated and received intravenous buprenorphine at a signifi cance level of 5%. rate of 0.625 μg·kg−1·h−1 continuously [10]. Intravenous midazolam was also administered after their admission to the ICU, and was adjusted every 2 h to achieve Results the desired depth of sedation, i.e., 3–5 on the Ramsay sedation scale. Patients were ventilated by synchron- The mean values for age, height, weight, and body ous intermittent mandatory ventilation or continuous surface area in the 28 patients were: 69 ± 11 years (range, positive airway pressure. All patients received con- 50–81 years), 158 ± 12 cm (range, 136–176 cm), 56 ± ventional intensive care therapy according to clinical 12 kg (range, 32–78 kg), and 1.6 ± 0.2 m2 (range 1.1– requirements. 1.9 m2), respectively. Nine patients underwent pancre- Indocyanine green (ICG) was injected into a periph- atoduodenectomy; 4, total gastrectomy; 2, low anterior eral vein, and the cardiac output (CO) and cardiac index resection; and 13, other operative procedures. A total. (CI) were determined by PDD (DDG-Analyzer; Nihon- of 56 simultaneous measurements were performed. V O2 Kohden, Tokyo, Japan). The sensor was attached to determined by indirect calorimetry was signifi cantly the patient’s nose. Obtained values were averaged higher than that determined by the Fick method (142 ± −1 −2 ± −1 −2 < from three consecutive ICG administrations. Values for 28 ml·min ·m vs 110 29 ml·min ·m ; P 0.01).. arterial oxygen saturation (Sa ), Scv , arterial oxygen The correlation between the two measurements of V O2 O2 O2 tension (Pa ), central venous oxygen tension (Pcv ), was weak (r2 = 0.145; P = 0.0038; Fig. 1). Bland and O2 O2 and hemoglobin concentration (Hb), obtained by Altman plots showed the mean bias (33 ml·min−1·m−2), −1 −2 blood gas analysis (ABL520; Radiometer,. Copenhagen, upper precision (65 ml·min ·m ), and lower precision Denmark), were used to calculate V by the Fick (1 ml·min−1·m−2; Fig. 2). The upper limit of agreement O2 method, using the following equation: was 97 ml·min−1·m−2 and the lower limit of agreement . was −31 ml·min−1·m−2. V = CI × {[Hb × 1.39 × (Sa − Scv )] + 0.0031 O2 O2 O2 × (Pa − Pcv )} × 10 O2 O2 We obtained the blood sample from a proximal port of Discussion the. CVC. V was measured by indirect calorimetry (Puritan- To monitor V in the ICU, the Fick method is a stan- O2 O2 . Bennett 7250 Metabolic Monitor, Puritan-Bennett, dard formula for calculating V , but PAC insertion is O2 Carlsbad, CA, USA), which had been integrated with a required. Some previous reports indicated the compli- 7200 Puritan-Bennett ventilator. A 45-min warmup cations and high cost of PAC [5–8]. Although indirect period was observed before each monitoring session, calorimetry. is a more accurate method for the measure- followed by sensor calibration with a known gas mixture ment of V , it is not routinely available. Thus, conve- O2 consisting of 5% carbon dioxide and 95% oxygen. Met- nient, safe, . and relatively inexpensive methods to abolic parameters were calculated by the metabolic determine V are needed for postoperative patients. O2 monitor. V measured by the 7250 Metabolic Monitor Rivers et al. [12] demonstrated that early goal-directed O2 was averaged for 15 min. therapy using Scv provided benefi ts with respect to the . O2 Simultaneous measurements of V by the Fick outcome in patients with severe sepsis and those with O2 method and by indirect calorimetry were made 1–2 h septic shock. Continuous Scv monitoring with CVC O2 after the patients’ admission to the ICU when the hemo- has become commercially available in recent years. dynamic state, respiratory state, and body temperature Because Reinhart et al. [9] reported that Scv was clini- O2 . were stable. Second measurements were performed the cally interchangeable with Sv , we compared V deter- O2 O2 next morning. Thus, a total of 56 sets of measurements mined by the Fick method. (using a PDD and CVC were performed in the 28 patients. without a PAC) with V determined by indirect calo- O2 The Wilcoxon test was performed to analyze the dif- rimetry in this study. ferences between methods. Concordance between the The results showed that V determined by the Fick O2 . two methods was determined by means of bias (mean method using a PDD and CVC underestimated the V O2 difference between the two methods) and precision (SD measured by indirect calorimetry. Because Bland and of the mean difference between the two methods), using Altman plots showed that the bias and precision of our Bland and Altman analysis [11]. Linear regression plots data were too wide and the correlation between the two C. Inadomi et al.: Fick method using central venous catheter 165 Fig. 1. Correlation coeffi cient between measurements. of oxygen consumption.
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