Comparison of recovery criteria in morbidly obese patients undergoing laparoscopic gastric sleeve resection following use of sevoflurane and isoflurane.

CONTEXT: The favorable kinetic properties of sevoflurane could be advantageous in obese patients undergoing bariatric surgery, improving recovery from general anesthesia (GA). AIMS: To compare the recovery criteria following anesthesia with sevoflurane and isoflurane in morbidly obese patients undergoing laparoscopic gastric sleeve resection. SETTINGS AND
DESIGN: This was a prospective randomized controlled study conducted in 50 patients undergoing laparoscopic sleeve gastrectomy.
MATERIALS AND METHODS: Following awake fiberoptic intubation, GA was induced and maintained with sevoflurane in Group A and isoflurane in Group B. 2% sevoflurane and 1.2% isoflurane were used and concentration varied to maintain a mean arterial pressure (MAP) of >75 mm of Hg, maximum concentration being 3% for sevoflurane and 2% for isoflurane. Inhalational agent was terminated at time of skin suturing and patients were extubated when completely awake. Recovery criteria followed were eye opening on call, voluntary head raising on command for 5 s and orientation assessed by answering name and location. STATISTICAL ANALYSIS USED: Student's t-test was used to test statistical significance of difference in mean values between the groups, analysis of covariance was used to test diastolic blood pressure (DBP) changes and Chi-square test to assess association between categorical variables.
RESULTS: There was no significant variability in heart rate, systolic blood pressure, DBP and MAP between 2 groups up to 210 min. Group A patients had significantly faster eye opening compared to Group B (4.4 ± 1.6 vs. 9.2 ± 2.18 min), were significantly faster in obeying commands (6.08 ± 1.6 vs. 10.08 ± 2.02 min), had a significantly shorter extubation time (7.08 ± 1.6 vs. 11.16 ± 2.18 min) and significantly faster orientation in time as compared to Group B (9.24 ± 1.7 vs. 12.32 ± 2.42 min).
CONCLUSION: Sevoflurane has a better recovery profile based on eye opening, obeying commands, time for extubation and orientation, than isoflurane in morbidly obese patients undergoing laparoscopic sleeve gastrectomy.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Bariatric surgery is one of the most commonly performed surgical weight loss modality to treat morbid obesity, a major health problem with clearly established health implications. Though all major organ systems are affected in obesity, the respiratory and cardiovascular involvements worry the anesthesiologists the most. Cardiovascular aberrations include increased blood volume, ischemic heart diseases, systemic and pulmonary hypertension eventually leading to congestive cardiac failure. Respiratory effects comprise of increased work of breathing, increased oxygen consumption, reduced functional residual capacity (FRC), ventilation perfusion mismatches and atelectasis. Anesthesia for laparoscopic gastric sleeve resection becomes more challenging as the adverse physiological effects of morbid obesity get compounded with the adverse pulmonary and cardiovascular effects of laparoscopy and general anesthesia (GA) itself. A variety of different anesthetic techniques in morbidly obese have been recommended, but no single method has been shown to have a proven advantage over others. The favorable kinetic properties of sevoflurane could be advantageous in obese patients, improving recovery from GA, which may lead to a reduction in the immediate postoperative complications.

The aim of the present study was to compare the recovery criteria following anesthesia with sevoflurane and isoflurane in morbidly obese patients undergoing laparoscopic gastric sleeve resection.

MATERIALS AND METHODS

The present study was done during the period of September 2010 to December 2012, after obtaining approval from Institution Ethical Committee and consent from the operating surgeons as well as patients.

Based on the available figures for the various study parameters[1] and with 95% confidence and 80% power minimum sample size for obeying the commands was calculated as 35 in each group. However due to lack of availability of the required number of cases, 50 morbidly patients undergoing laparoscopic sleeve gastrectomy, aged between 25 to 45 years, belonging to ASA physical status II-III were randomized by closed envelope method to two equal groups of 25 each. Group A patients were maintained with sevoflurane intra operatively, whereas Group B with isoflurane.

Patients with severe cardiac, hepatic or renal dysfunction and ASA physical status IV and above were excluded. All patients were pre-medicated orally with ranitidine 150 mg and metoclopramide 10 mg on night prior to surgery and repeated in the morning of surgery. The patients were kept fasting for 8 h.

On the day of surgery, in the theatre a wide bore intravenous catheter was inserted under local anesthesia and Ringer lactate infusion was started. Pre-induction monitors like noninvasive blood pressure (BP) monitor, electrocardiography and pulse oxymeter were attached. Arterial cannulation was performed on left radial artery with a 20 gauge cannula under local anesthesia before induction of anesthesia. Invasive BP monitoring was chosen, though arterial cannulation could be difficult in morbidly obese, as it was more accurate, continuous monitoring was possible and taking arterial blood gas samples were easy.

All patients received premedication with injection glycopyrolate 0.2 mg and injection fentanyl 2 μg/kg body weight intravenously. The airway was anesthetized by applying 2% lidocaine jelly into the nasal cavity, spraying 10% lidocaine into oropharynx and by giving a transtracheal injection of 4 ml of 4% lidocaine. Then awake fiber-optic intubation was performed as mask holding, mask ventilation, laryngoscopy and intubation could be difficult in the morbidly obese. Once the endotracheal tube position was confirmed by capnogram and auscultation, patients were induced with injection propofol 2 mg/kg body weight intravenously. Injection atracurium 0.5 mg/kg body weight was given intravenously for muscle relaxation and 5 mg was repeated every 20-30 min.

Intra operatively anesthesia was maintained with sevoflurane in Group A and isoflurane in Group B in 60% air and oxygen at flow rate of 2 L/min using a closed circuit. The volatile agent was administered at approximately one MAC i.e. by setting 2% for sevoflurane and 1.2% for isoflurane on the vaporizer dial. Concentration of inhalational agent was varied according to variation of mean arterial pressure (MAP), so as to maintain a MAP of more than 75 mm of Hg. Fentanyl was supplemented as per the surgical response on heart rate (HR). It was repeated at a dose of 20 μg as bolus intravenously if HR and/or MAP were more than 20% of baseline value after increasing the volatile agent concentration to 3% in case of sevoflurane and 2% in case of isoflurane for 3-5 min. Additional analgesia was given with inj. paracetamol 1 g intravenously over 20 min after the first 500 ml of intravenous fluid.

After induction, end tidal carbon dioxide analyzer and temperature probe were connected to the patient. Urinary catheter was inserted and output was monitored. Central venous pressure monitoring was done with a central venous catheter (7 French) inserted either through internal jugular vein or subclavian vein.

10 ml of 0.25% bupivacaine was given as local infiltration before suturing at the site of incision. Inhalational anesthetic was terminated at the time of skin suturing. Tracheal extubation was done when the patient was completely awake and the protective airway reflexes had returned.

Hemodynamic variables like HR, systolic blood pressure (SBP), diastolic blood pressure (DBP) and MAP were recorded. Baseline values were noted when the patient was received in the theatre. After induction, though continuous monitoring of HR and BP were done intraoperatively, data collection for study was done only ½ hourly till the end of surgery. Recovery criteria followed in the study were eye opening on call, voluntary head raising on command for 5 s and orientation assessed by answering name and location. Moreover, the time between the suspension of volatile agent and the tracheal extubation (time to extubate) was also documented.

RESULTS

To test the statistical significance of the difference in the mean values of various measurable parameters between the two groups, Student's t-test was applied. Since mean baseline DBP significantly varied between the groups, the data was assessed using analysis of covariance (ANCOVA). Chi-square test was used to test statistical significance of the association between categorical variables. Data was analyzed using Statistical Package for Social Scientists (SPSS version 20, IBM). The level of statistical significance (P value) was fixed at 5%.

Distribution of patients in both groups were similar with respect to demographics, ASA distribution and duration of surgery. Statistically there was not much of significant variability in HR between the 2 groups from baseline value up to 210 min. After 120 min only some of the cases continued as majority of the cases were over by 120 min [Table 1, Figure 1]. The baseline mean SBP in Group A and B didn’t show any significant difference between groups (P 0.59). Likewise at 30, 60, 120, 150 and 180 min also there was no significant difference. The P value for 210 min was significant, but the number of cases which went on till 210 min was only 7 [Table 2, Figure 2].

Table 1

Comparison of HR between the groups at various time intervals

Figure 1

Graphical representation of mean heart rates in both groups

Table 2

Comparison of SBP between groups at various time intervals

Figure 2

Graphical representation of mean systolic blood pressures in both groups

DBP was analyzed using ANCOVA, because there was a significant variation in the baseline mean in both groups. So an adjusted mean was computed so as to make the values comparable. The comparison of mean DBP between groups in different time period did not show any statistically significant difference [Table 3, Figure 3]. Mean values for MAP in both groups at baseline were found to be comparable. All the values except 210 min were also comparable as the P value at all the time periods were above 0.05 [Table 4, Figure 4].

Table 3

Comparison of mean DBP between groups at various time intervals

Figure 3

Graphical representation of mean diastolic blood pressures in both groups

Table 4

Comparison of MAP between groups at various time intervals

Figure 4

Graphical representation of mean arterial pressures in both groups

In Group A the mean eye opening time was 4.4 ± 1.6 min whereas in Group B it was 9.2 ± 2.18. When compared it was shown that Group A patients were significantly faster in eye opening compared to Group B (P < 0.001) [Table 5, Figure 5]. Mean obeying commands time was 6.08 ± 1.6 min in Group A whereas in Group B it was 10.08 ± 2.02 and patients in Group A proved to be significantly faster in obeying commands (P < 0.001) [Table 5, Figure 6].

Table 5

Comparison of recovery criteria between groups

Figure 5

Eye opening time among the groups

Figure 6

Obeying commands time

While comparing mean extubation time, it was seen that Group A patients were extubated significantly earlier compared to Group B (7.08 ± 1.6 vs. 11.16 ± 2.18 min, P < 0.001) [Table 5, Figure 7]. Likewise Group A patients were significantly faster in attaining orientation in time also, as compared to Group B (9.24 ± 1.7 vs. 12.32 ± 2.42 min, P < 0.001) [Table 5, Figure 8].

Figure 7

Extubation time

Figure 8

Orientation time

DISCUSSION

Obesity affects almost all organ systems in the body. It has a proven link to increased risk of development of stroke in both men and women[234567] and results in deranged pulmonary functions and diminished exercise capacity.[8] This group of patients are at risk of aspiration pneumonia, pulmonary thromboembolism and respiratory failure. Likewise obstructive sleep apnea and obesity hypoventilation syndrome are associated with substantial morbidity and increased mortality.[8]

Laparoscopic surgery itself results in derangements in both cardiovascular and pulmonary functions. The adverse pulmonary effects are mainly due to pneumoperitonium itself which push the diaphragm upwards. There are reductions in FRC and thoracopulmonay compliance. Hypercarbia resulting from absorption of CO2 can lead on to respiratory acidosis. Pneumothorax, subcutaneous emphysema and gas embolism are other adverse events. The hemodynamic disturbances are also because of pneumoperitonium causing a reduced venous return due to compression of inferior vena cava and an increased resistance in venous circulation. There is a subsequent fall in cardiac output, increased systemic vascular resistance due to release of catacholamines and appearance of dysrrhthmias. In obese patients these adverse cardiopulmonary effects will be exaggerated as these systems are already in compromised states.

Body mass index (BMI) >25 kg/m2 was found to be an independent risk factor for postoperative pulmonary complications[9] and BMI >27 kg/m2 was one of six independent factors for pulmonary complications.[10] Such patients are at risk for airway complications, sleep apnea and hypoxia during the early recovery period. The specific problems associated with obesity should taken into consideration while planning the anesthetic management, and before bariatric surgery these patients should be optimized.[11]

Differences in solubility of volatile anesthetic agents in blood has got important implications in awakening following GA. Awakening and extubation times were found to be significantly less following sevoflurane anesthesia[12] as these patients manifest significantly shorter recovery parameters compared to those who received isoflurane,[13] since sevoflurane is less soluble in blood than isoflurane. In obese patients after upper abdominal surgery, a 45% incidence of atelectasis has been reported.[14] Faster emergence, early extubation with a secure airway and maintenance of spontaneous ventilation lead to reduced risk of development of postoperative complications and improve patient comfort. Reduction in time spent in operation theatre will obviously lead to quicker patient turnover and will prove to be more economical also.

Limitations of the study

A larger sample size should have been recruited. Inhalational agents were delivered as per dial concentration. Gasman analysis could have been used as we could actually measure the quantity of agent used.

CONCLUSION

We conclude that sevoflurane has a better recovery profile based on eye opening, obeying commands, time for extubation and orientation, than isoflurane in morbidly obese patients undergoing laparoscopic sleeve gastrectomy.