Abstract ABDELRADY S. IBRAHIM, M.D.

Transcription

1 Med. J. Cairo Univ., VoL 81, No. 2, March: , Noninvasive Cardiac Output Monitoring in Morbidly Obese Patients During Laparoscopic Bariatric Surgery: Effect of Positive End-Expiratory Pressure and Alveolar Recruitment Maneuver ABDELRADY S. IBRAHIM, M.D. The Department of Anesthesia, Faculty of Medicine, Assiut University Abstract Objective: This study was designed to evaluate the effect of positive end-expiratory pressure (PEEP) and Alveolar recruitment maneuver (ARM) used to improve gas exchange during anesthesia in laparoscopic bariatric surgery on cardiac output parameters using non-invasive thoracic electrical bioimpedance. Study Design: A randomized controlled study was conducted on 30 morbidly obese patients (ASA I and II), with BMI >40kg.m2, scheduled for laparoscopic bariatric surgery were included the study. Setting: International Medical Center (IMC) Hospital, OR department, Bariatric surgery unit, Jeddah, K.S.A. Interventions: Patients were classified into two groups after induction of anesthesia (15 in each): Group I: PEEP was maintained at 10cm H20 prior to peritoneum insufflation with CO2 until the end of the surgery. Group II: The first set of Lung recruitment was achieved prior to insufflation of peritoneum with CO2, by sequential increases in PEEP in three steps from 0 to 20 cm H20. The maneuver was repeated ten minutes after insufflation of peritoneum and lastly the maneuver was done after abdominal deflation. Measurement: Stroke volume index (SVI), cardiac index (CI), and ejection fraction (EF), using non-invasive thoracic electrical bioimpedance, together with heart rate (HR) and mean arterial blood pressure (MAP) were measured in both groups, at three points: To: Prior to, applying PEEP in group I and before starting the first set of Lung recruitment in group II. Ti: 10 minutes after applying PEEP in group I and after starting the first set of Lung recruitment in group II. T2: 10 minutes after abdominal deflation in group I and group II. Results: The patients were comparable regarding their age and BMI. HR was significantly increase in group I and group II at Ti when compared toto (p=0.01). MBP showed significant decrease at T1 inside group I (p=0.04) and group II (p=0.01) when compared to To. At T2 there were insignificant changes in HR and MBP values in both groups (p>0.05). Correspondence to: Dr. Abdelrady S. Ibrahim, The Department of Anesthesia, Faculty of Medicine, Assiut University SVI and CI showed significant decrease in group I, at Ti and T2 when compared to To, (p<0.05). In group II, SVI and CI values were decreased significantly at Ti (p<0.05) and decreased insignificantly at T2 (p>0.05) when compared to To. EF was statistically insignificant when compared Ti and T2 to To inside each group (p>0.05). In comparison between group I and group II the mean values of HR, MBP, SVI, CI and EF showed insignificant differences at To, Ti and T2. Conclusions: The use of PEEP or alveolar recruitment maneuver to improve arterial oxygenation during laparoscopic bariatric surgery in morbidly obese patients was associated with intraoperative negative hemodynamic changes. Key Words: Positive end-expiratory pressure (PEEP) Alveolar recruitment maneuver (MRM). Introduction THE rising prevalence of obesity translates into more obese patients presenting for surgery. Despite the higher risks and anesthetic challenges associated with this patient population and the additional physiologic perturbations imposed by capnopneumoperitoneum, laparoscopic procedures are increasingly performed [ii. The development of atelectasis is common during general anesthesia due to the reduction in functional residual capacity (FRC) [2]. This situation tends to be worse in morbidly obese patients since they have reduced functional residual capacity (FRC) and expiratory reserve volume (ERV) while awake, which is further aggravated in the supine position and during anesthesia [3]. Alveolar recruitment maneuver (ARM) and High Positive End-Expiratory Pressure (PEEP) levels have been proposed and used to improve gas exchange during anesthesia in bariatric surgery [4]. To keep the alveoli open in the morbidly obese patients we should use PEEP higher than that used in patients of normal body weight [5]. Because of the morbidly obese patients are susceptible for 207

2 208 Noninvasive Cardiac Output Monitoring cardiovascular diseases, the use of high PEEP level and insufflation of peritoneum with carbon dioxide (CO2) gas during laparoscopic procedure could negatively affect intraoperative hemodynamics [6,7]. The purpose of this study was to evaluate the effect of two different ventilatory strategies (Fixed PEEP level and ARM) used to improve gas exchange during anesthesia in laparoscopic bariatric surgery on noninvasive cardiac output parameters including stroke volume index (SVI), cardiac index (CI), and ejection fraction (EF). Patients and Methods After obtaining approval from Institutional Ethics Committee of International Medical Center Hospital (Jeddah, K.S.A.) and informed written consent, a randomized controlled study was completed from January 2011 to April 2012, on thirty patients (aged years), morbidly obese (BMI >40kg.m2), ASA physical status I and II, with normal pulmonary function tests or with mild abnormalities, scheduled to laparoscopic bariatric surgery (sleeve gastrectomy or gastric bybass). Patients with history of spontaneous pneumothorax, serious lung diseases, patients who required intervention by laparotomy, and those with intraoperative hemodynamic instability were excluded. In the operating room, Patients were placed in dorsal decubitus with discrete head-up tilt, a peripheral vein was cannulated with an 18G catheter and hydration was initiated with 6% HES 130/0.4 (Voluven) 15m1/kg of ideal body weight before induction of anesthesia and Ringer's lactate 10m1/ kg/h of ideal body weight after induction of anesthesia. Heart rate (HR), noninvasive arterial blood pressure (NIBP), peripheral blood oxygen saturation (Sp02), and end expiratory carbondioxide pressure (EtCO2) of patients were monitored. Noninvasive thoracic electrical bioimpedance (NCCOM3 cardiodynamic monitor) was connected to the patient using four neck and four lower thoracic electrodes. Anesthesia was initiated with 100% 02 with a face mask for 5min, followed by induction with intravenous midazolam (lmg), fentanyl (1p,g/kg of ideal body weight), Propofol (2mg/kg of ideal body weight) and Cisatracurium (0.15mg/kg of ideal body weight) to facilitate endotracheal intubation. After tracheal intubation, anesthesia was maintained with sevoflurane in 02 and air (Fi02 of 0.5), Cisatracurium (lpg/kg ideal body weight /min) and fentanyl (0.5pg/ kg ideal body weight /h) were infused. Volume-Controlled ventilation was performed in all patients and the ventilator was set to deliver tidal volume (VT) of 8 to 10mL /kg of ideal body weight, respiratory rate (RR) of 10 to 12/min, and I:E ratio was 1:2, to achieve normocarbia [ETCO mmhg], and peak inspiratory pressure (PIP) was maintained to 45cm H20 throughout the operation. Patients were classified into two groups (15 in each): Group I (PEEP group): After obtaining a steady state ventilation and prior to insufflation of peritoneum with CO2 (intra-abdominal inflation pressure=15cm H20), end expiratory pressure was maintained positive (PEEP) at 10cm H20 until the end of the surgery. Group II (Alveolar recruitment group): The first set of Lung recruitment was achieved after obtaining a steady state ventilation and prior to insufflation of peritoneum with CO2, by gradual increases in PEEP level in three steps from 0 to 10cm H20 (for 3 minutes), 10 to 15cm H20 (for 3 minutes), and 15 to 20cm H20 PEEP (for 3 minutes). After recruitment, the level of PEEP was gradually decreased by 5cm H20 down to Ocm H20. The second maneuver of Lung recruitment was repeated ten minutes after insufflation of peritoneum with CO2. The last recruitment maneuver was done after abdominal deflation at the end of surgery while maintaining anesthesia unchanged. Cisatracurium and fentanyl infusion was stopped, neuromuscular blockade was reversed, and the patient was extubated and send to postanesthesia care unit (PACU). Measurements: Stroke volume index (SVI), cardiac index (CI), and ejection fraction (EF), using non-invasive thoracic electrical bioimpedance, together with heart rate (HR) and mean arterial blood pressure (MAP) were measured in both groups, in the supine position, at three points: 10 minutes after tracheal intubation prior to, applying PEEP in group I and before starting the first set of Lung recruitment in group II (To), 10 minutes after applying PEEP in group I and after starting the first set of Lung recruitment in group II (TO, and at the end of surgery 10 minutes after abdominal deflation in group I and group II (T2). Statistical analysis: Data were collected from each patient in the two groups in separate sheet at three times (To, Ti and T2). All data were statistically analyzed using SPSS statistical package (version 16). Analysis of Variance (ANOVA) with multiple comparisons was used to compare between group I and group

3 Abdelrady S. Ibrahim 209 II and Paired t-test was used for comparison between the basal reading (TO) and the subsequent readings (T 1 and T2) inside the same group. The results were expressed as Mean ± Standard deviation (Mean±SD). p-value less than 0.05 was regarded as statistically significant. Resufts Thirty morbidly obese patients (male and female) with body mass index (BMI) 53.2±4.4kg.m2 in group I and 51.7±5.7kg.m2 in group II, were included in this study, they were comparable regarding their age, weight and height. All patients completed the study where they tmdergone laparoscopic bariatric operations either sleeve gastrectomy or gastric bypass and the mean duration of the operation was comparable in both groups as shown in Table (1). Table (1): Demographic and operative data. (Mean±SD and number). Group I Group II Age (year) 37.3± ±14.1 Sex (Male/Female) 5/10 7/8 Weight (kg) 150.7± ±13.4 Height (cm) 168.5± ±10.1 BMI (kg.m2) 53.2± ±5.7 Type of operation (Sleeve/Bypass) 9/6 11/4 Duration of operation (min) 106.1± ±26.6 There was significant increase in the mean HR values in group I and group II at T 1 after insufflation of peritoneum with CO2 when compared to the baseline value (To_); p=0.01, while at T2 there were insignificant changes in HR in both groups (p>0.05). MBP showed significant decrease at Ti inside groups I (p=0.04) and group II (p=0.01) when compared to baseline value (To). At T2 there were insignificant changes in MBP values in both groups (p>0.05). The mean values of SVI and CI in group I showed significant decrease at Ti and T2 when compared to baseline value (To), where p-value was <0.05. In group II SVI and CI values were decreased significantly at Ti (p<0.05) and decreased insignificantly at T2 (p>0.05) when compared to To. EF and Sa02 mean values were statistically insignificant when compared Ti and T2 to To inside each group (p>0.05). In comparison between group I and group II the mean values of hemodynamic parameters including HR, MBP, SVI, CI and EF plus Sa02 showed insignificant differences at all times of the study period (To, Ti and T2) as shown in Table (2). Table (2): Changes in heart rate (HR), mean arterial blood pressure (MABP), stroke volume index (SVI), cardiac index (CI), ejection fraction (EF) and arterial oxygen saturation (Sa02) at different times in the studied groups. HR (bpm) TO T1 T2 Group I Mean±SD (pi) 82.6± ±8.6* (0.012) 88.9±7.9 (0.07) Group II Mean±SD (pi) 85.4± ±6.1* (0.01) 91.4±8.7 (0.158) P TO 87.4± ± MABP (mmhg) T1 80.6±9.2* (0.04) 81.0±7.6* (0.019) T2 87.1±6.4 (0.90) 84.2±6.7 (0.186) TO 40.7± ± svi 0111/m2) T1 35.6±3.9* (0.000) 34.1±4.4* (0.000) T2 37.5±2.9* (0.017) 39.3±1.2 (0.223) TO 3.31± ± CI (L/min/m2) T1 2.76±0.43* (0.004) 2.87±0.55* (0.01) 0.44 T2 3.02±0.56* (0.000) 3.1±0.53 (0.07) TO 58.8± ± EF (%) T1 57.8±2.6 (0.443) 57.7±1.6 (0.382) T2 58.2±3.2 (0.329) 58.3±1.9 (0.868) TO 97.6± ± Sa02 (%) T1 97.9±1.19 (0.87) 97.9±0.87 (0.91) T2 98.2±1.03 (0.31) 97.7±1.19 (0.67) pi: Comparison inside the group (Paired t-test). p2: Comparison between the groups (ANOVA test). * Statistical significant differences (p<0.05). Discussion Improvement of arterial oxygenation and oxygen delivery during anesthesia can be achieved by alveolar recruitment strategy and by addition of positive end-expiratory pressure (PEEP) [8]. But, PEEP can cause a decrease in cardiac output (CO) [9] by increasing intrathoracic pressure; which lead to a decrease in right ventricular venous return Hob We found that the use of PEEP (10cm H20) and alveolar recruitment maneuver for morbidly obese patients (BMI >40 kg m2) to improve arterial oxygenation during laparoscopic bariatric surgery is accompanied by reduction in MABP, SVI and CI in both techniques and these values were returned to near baseline values in AR group but still significantly reduced in fixed PEEP group and the differences between the two groups were insignificant. The patients were well hydrated preoperative by intravenous infusion of Voluven 15m1/kg of ideal body weight and intraoperative by Ringer's lactate 10m1/kg ideal body weight/h and intraabdominal inflation pressure was maintained at 15cm H20. The ideal intraoperative ventilation strategy in obese patients remains obscure. There is some

4 210 Noninvasive Cardiac Output Monitoring evidence that RM added to PEEP compared with PEEP alone improves intraoperative oxygenation and compliance without adverse effects [111. PEEP usually does not change the heart rate, so, the decrease in cardiac output is a result of reduction in left ventricular stroke volume (SV) [12]. James and his colleagues, study the effect of incremental PEEP on right ventricular hemodynamics and they found that Cardiac index (CI) decreased from 4.4L/min/m2 at baseline to 3.5L/min/m2 at 10cm H20 (p<0.05) [13]. In this study CI was decreased from 3.3L/min/m2 to 2.7L/min/m2 in PEEP group and from 3.3L/min/m2 to 2.8L/min/m2 in AR group. There was a significant reduction in preload and cardiac output when there was intraabdominal pressure of 15mmHg in the presence of 10cm H20 of PEEP this combination of pressures may pose a contraindication to laparoscopic surgery [14]. Wiboon and colleagues (2006) documented significant changes in systemic hemodynamic variables that seem to be directly associated with the insufflation of CO2 during gynecologic intra-peritoneal laparoscopic surgery [15]. The use of alveolar recruitment may be an effective mode of improving intraoperative oxygenation in morbidly obese patients; the effect to be short lived (ended by extubation) and associated with more frequent intraoperative use of vasopressors [16]. Perilli et al. (2003), study the effect of PEEP and Reverse Trendelenburg Position in morbidly obese patients undergoing bariatric surgery on hemodynamics and pulmonary gas exchange and thy concluded that; the decrease in cardiac output may partially counteract the beneficial effects on oxygenation of these ventilatory settings [17]. In other hand Stephan et al., revealed that the use of alveolar recruitment and high PEEP level in well hydrated morbidly obese patients during laparoscopic surgery have insignificant changes in hemodynamic parameters [18]. There is some evidence that RM added to PEEP compared with PEEP alone improves intraoperative oxygenation and compliance without adverse effects on arterial pressure [19]. Pinsky in 2005 observed hemodynamic stability before and after insufflation of CO2 to the peritoneum, while using alveolar recruitment strategy or high PEEP level in intravascular volumeloaded morbidly obese patients during laparoscopic surgery [20]. The condition of vascular volume of the obese patient during bariatric surgery has an important role on the hemodynamic stability Regardless of BMI. Jellinek et al., explained the hemodynamic stability with high PEEP level while keeping CVP above lomm Hg because of reduction in transmural pressure which has an effect on the hemodynamics [21]. Also, Erlandsson and his col- leagues in 2006; did not observed any negative intraoperative hemodynamic changes in preloaded (1L fluids) morbidly obese patients using high PEEP [22]. Hyun et al., found that application of 10cm H20 PEEP during CO2 pneumoperitoneum could preserve the hemodynamic stability in patients undergoing laparoscopic cholecystectomy under propofol anesthesia [23]. Morbidly obese patients undergoing laparoscopic bariatric surgery are at risk for intraoperative complications relating to the use of CO2 pneumoperitoneum and ventilatory strategies. Anesthesiologist should understand the physiologic effect of pneumoperitoneum and PEEP in the morbidly obese and make appropriate intraoperative ventilatory adjustments and optimize intravascular volume to minimize the adverse changes on cardiac function [24]. 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