Carbon dioxide monitoring during laparoscopic-assisted bariatric surgery in severely obese patients: transcutaneous versus end-tidal techniques.

Various factors including severe obesity or increases in intra-abdominal pressure during laparoscopy can lead to inaccuracies in end-tidal carbon dioxide (PETCO2) monitoring. The current study prospectively compares ET and transcutaneous (TC) CO2 monitoring in severely obese adolescents and young adults during laparoscopic-assisted bariatric surgery. Carbon dioxide was measured with both ET and TC devices during insufflation and laparoscopic bariatric surgery. The differences between each measure (PETCO2 and TC-CO2) and the PaCO2 were compared using a non-paired t test, Fisher's exact test, and a Bland-Altman analysis. The study cohort included 25 adolescents with a mean body mass index of 50.2 kg/m2 undergoing laparoscopic bariatric surgery. There was no difference in the absolute difference between the TC-CO2 and PaCO2 (3.2±3.0 mmHg) and the absolute difference between the PETCO2 and PaCO2 (3.7±2.5 mmHg). The bias and precision were 0.3 and 4.3 mmHg for TC monitoring versus PaCO2 and 3.2 and 3.2 mmHg for ET monitoring versus PaCO2. In the young severely obese population both TC and PETCO2 monitoring can be used to effectively estimate PaCO2. The correlation of PaCO2 to TC-CO2 is good, and similar to the correlation of PaCO2 to PETCO2. In this population, both of these non-invasive measures of PaCO2 can be used to monitor ventilation and minimize arterial blood gas sampling.

Ventilation during laparoscopic-assisted bariatric surgery: volume-controlled, pressure-controlled or volume-guaranteed pressure-regulated modes.

INTRODUCTION: Managing ventilation and oxygenation during laparoscopic procedures in severely obese patients undergoing weight loss surgery presents many challenges. Pressure-controlled ventilation, volume-guaranteed (PCV-VG) is a dual-control mode of ventilation and an alternative to pressure (PC) or volume (VC) controlled ventilation. PCV-VG features a user-selected tidal volume target, that is auto-regulated and pressure controlled. We hypothesized that PCV-VG ventilation would provide improved oxygenation and ventilation during laparoscopic bariatric surgery with a lower peak inflating pressure (PIP) than either PC or VC ventilation. METHODS: This was a prospective cross-over cohort trial (n = 20). In random sequence each patient received the three modes of ventilation for 20 minutes during the laparoscopic portion of the procedure. For all modes of ventilation the goal tidal volume was 6-8 mL/kg, and the respiratory rate was adjusted to achieve normocarbia. The PIP, exhaled tidal volume, respiratory rate, and oxygen saturation were recorded every five minutes. At the end of 20 minutes, an arterial blood gas was obtained. Data were analyzed using a paired t-test. RESULTS: PCV-VG and PC ventilation both resulted in significantly lower PIP (cmH2O) than VC ventilation (30.5 ± 3.0, 31.6 ± 4.9, and 36.3 ± 3.4 mmHg respectively; p < 0.01 for PCV-VG vs. VC and PC vs. VC). There was no difference in oxygenation (PaO2), ventilation (PaCO2) or hemodynamic variables between the three ventilation modes. CONCLUSIONS: In adolescents and young adults undergoing laparoscopic bariatric surgery, PCV-VG and PC were superior to VC ventilation in their ability to provide ventilation with the lowest PIP.

Accuracy of the CNAP™ monitor, a noninvasive continuous blood pressure device, in providing beat-to-beat blood pressure measurements during bariatric surgery in severely obese adolescents and young adults.

BACKGROUND: During perioperative care, the continuous measurement of blood pressure (BP) provides superior physiological monitoring compared to intermittent techniques, especially for patients with comorbid conditions such as severe obesity. The current study prospectively assesses the accuracy of a continuous, noninvasive BP device in severely obese adolescents and young adults. METHODS: The technology evaluated was the CNAP Monitor 500, developed by CNSystems AG (Graz, Austria). The study cohort was composed of severely obese adolescents (body mass index ≥ 35 kg/m(2)) undergoing a surgical weight loss procedure (robotically assisted or laparoscopic vertical sleeve gastrectomy or laparoscopic Roux-en-Y gastric bypass). Systolic (sBP), diastolic (dBP), and mean arterial (MAP) blood pressure readings were captured from an intraoperatively placed radial arterial cannula (AC) and the CNAP device at regular intervals (once per minute) during anesthetic care. RESULTS: The study cohort consisted of 18 severely obese subjects undergoing weight loss surgery. A total of 2,159 pairs each of sBP, dBP, and MAP values obtained. The correlation coefficient between the AC and the CNAP device was 0.655, 0.667, and 0.783 for the sBP, dBP, and MAP, respectively. The CNAP values (sBP, dBP, MAP) were ≤5 mmHg from the AC values in 33, 40, and 41% of the values, respectively. The difference was more than 10 mmHg (sBP, dBP, MAP) in 39, 28, and 25% of the values, respectively. Using a Bland-Altman analysis, the precision and bias for the sBP, dBP, and MAP were 0.3 ± 14.2, -1.3 ± 9.5, and -0.6 ± 8.6 mmHg, respectively. CONCLUSION: When compared to previous studies in the adult population, the accuracy of the CNAP device in a cohort of severely obese adolescents undergoing weight loss surgery was slightly less than previously reported. The current data demonstrate a clinically useful trend of the CNAP device with arterial values in this challenging patient population in whom an arterial cannula may at times be difficult.