BACKGROUBD: Hypercarbia and raised intraabdominal pressure during pneumoperitoneum (PP) can adversely effect ventilatory function. We evaluated intraoperative respiratory mechanics in morbidly obese patients during laparoscopic and open gastric bypass (GBP).
METHODS: Fifty-eight patients with a body mass index (BMI) of 40-60 kg/m2 were randomnly allocated to laparoscopic (n=31) or open (n=27) GBP. Pulmonary compliance (CL), end-tidal CO2 (ETCO2), arterial PCO2 (PaCO2), peak inspiratory pressure (PIP), CO2 production (VCO2), and standard hemodynamics were recorded at baseline and at 30-min intervals. During laparosocic GBP, ventilatory settings were adjusted to maintain a higher respiratory rate than during open GBP to keep the ETCO2 levels within an acceptable range and to maintain a lower tidal volume due to higher PIP.
RESULTS: The two groups were similar in age, gender, and BMI. Compared to open GBP, laparoscopic GBP significantly increased ETCO2, PaCO2, PIP, VCO2, and decreased CL (p<0.05). There was no significant difference between groups in heart rate (HR), mean arterial pressure (MAP), number of intraoperative episodes of hypotension (MAP<60), bradycardia (HR<60), or desaturation (SaO2<90%).
CONCLUSIONS: Laparoscopic GBP adversely alters intraoperative respiratory mechanics. However, when proper ventilatory adjustments were maintained to keep levels of ETCO2 and PIP within acceptable ranges, no adverse changes in intraoperative hemodynamics were observed.
Respiratory Mechanics during Laparoscopic and Open GBP
Parameters GBP Baseline 1 hour 2 hour 2.5 hour
CL Lap 31.0 ± 8.8 18.6 ± 4.8* 17.5 ± 5.7* 18.9 ± 5.2*
(mL/cm) Open 34.6 ± 7.6 26.6 ± 6.5 26.5 ± 7.1 25.2 ± 7.1
PIP Lap 29.8 ± 5.3 33.1 ± 5.0* 33.9 ± 4.5* 33.8 ± 5.2 *
(mmHg) Open 28.8 ± 5.1 27.6 ± 3.9 26.8 ± 3.1 28.2 ± 3.3
PaCO2 Lap 38.5 ± 4.3 40.6 ± 3.8* 41.4 ± 4.7* 41.9 ± 4.4*
(mmHg) Open 37.6 ± 4.5 36.1 ± 2.7 36.7 ± 3.2 36.9 ± 3.4
* p<0.05 vs open GBP (Fisher PLSD).
