|Year : 2013 | Volume
| Issue : 1 | Page : 89-93
Effect of bispectral index monitoring on desflurane consumption and recovery time in morbidly obese patients undergoing laparoscopic sleeve gastrectomy
Tamer H Ibrahim, Gamal T Yousef, Ali M Ali Hasan, Hossam I Eldesuky
Department of Anesthesia and Intensive Care, Faculty of Medicine, Zagazig University, Zagazig, Egypt
|Date of Web Publication||26-Jun-2013|
Gamal T Yousef
Department of Anesthesia and Intensive Care, Faculty of Medicine, Zagazig University, Zagazig
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Morbid obesity magnifies the importance of the fat-blood solubility coefficient of the anesthetic in its relation to emergence and recovery. Using bispectral index (BIS) monitoring for the titration of the administration of inhaled anesthetics such as desflurane may permit a less consumption and more rapid recovery from desflurane anesthesia in morbidly obese patients, which enables earlier maintenance of a patent airway, better protection against aspiration, and better oxygenation.
Objective: The aim of this study was to investigate the effect of BIS monitoring on postoperative extubation and recovery times, and intraoperative desflurane consumption in morbidly obese patients undergoing laparoscopic sleeve gastrectomy under general anesthesia using desflurane for maintenance.
Patients and Methods: Forty morbidly obese patients were randomly enrolled in this study and divided into two groups of 20 patients each: Non-BIS group and BIS group. End-tidal desflurane concentration, mean blood pressure, and heart rate were regularly recorded. Recovery times (eye opening to verbal commands, time to extubation, and orientation to time, place, and person) and the time to achieve a modified Aldrete score of ≥ 9 were recorded by blinded study anesthesia nurse. Desflurane consumption was calculated in milliliters through gas usage option of Datex-Ohmeda S/5 anesthesia machine.
Results: The mean end-tidal concentrations of desflurane were significantly decreased in the BIS group compared to the non-BIS group ( P < 0.05). The mean desflurane consumption and cost were significantly lower in the BIS group (124.8 ± 5.1 ml/patient) compared to the non-BIS group (150.6 ± 6.5 ml/patient) ( P < 0.05). Recovery times were significantly shorter in the BIS group versus non-BIS group ( P < 0.05).
Conclusion: The use of BIS monitoring was effective in reducing intraoperative desflurane requirement (cost) and in shortening early recovery times after laparoscopic sleeve gastrectomy in morbidly obese patients without compromising the hemodynamic stability, adequacy of anesthesia, or patient outcome.
Keywords: Bispectral index, desflurane, laparoscopic sleeve gastrectomy, morbid obesity
|How to cite this article:|
Ibrahim TH, Yousef GT, Ali Hasan AM, Eldesuky HI. Effect of bispectral index monitoring on desflurane consumption and recovery time in morbidly obese patients undergoing laparoscopic sleeve gastrectomy. Anesth Essays Res 2013;7:89-93
|How to cite this URL:|
Ibrahim TH, Yousef GT, Ali Hasan AM, Eldesuky HI. Effect of bispectral index monitoring on desflurane consumption and recovery time in morbidly obese patients undergoing laparoscopic sleeve gastrectomy. Anesth Essays Res [serial online] 2013 [cited 2020 Jul 6];7:89-93. Available from: http://www.aeronline.org/text.asp?2013/7/1/89/114010
| Introduction|| |
Several potential problems related to anesthesia in morbidly obese patients have been identified such as difficult mask ventilation, difficult laryngoscopy, , and more frequent perioperative respiratory and cardiovascular events. , All volatile anesthetics accumulate, over time, in adipose tissue. Such accumulation may delay recovery from anesthesia. The impact of anesthetic stored in fat may be the result of a return of the anesthetic in blood perfusing the fat or of a transfer from fat to adjacent highly perfused tissues.  Obesity magnifies the importance of the fat-blood solubility coefficient of the anesthetic in its relation to emergence and recovery.  Clinical studies involving electroencephalographic-based cerebral monitors have demonstrated titration of both intravenous , and inhalational , anesthetics during general anesthesia. Titration of anesthetics using these monitors can facilitate an earlier emergence from general anesthesia. Bispectral index (BIS) monitoring has been proven to be effective in preventing awareness. Optimizing anesthesia level using BIS monitoring will probably help to shorten recovery time and reduce total anesthetic drug consumption. ,, Using BIS monitoring for the titration of the administration of inhaled anesthetics such as desflurane may permit a less consumption and more rapid recovery from desflurane anesthesia in morbidly obese patients. No studies have investigated the potential usefulness of BIS monitoring to guide the administration of desflurane in morbidly obese patients undergoing laparoscopic sleeve gastrectomy. The aim of this randomized prospective controlled single-blinded study was to investigate the effect of BIS monitoring on extubation and recovery times, and intraoperative desflurane consumption in morbidly obese patients undergoing laparoscopic sleeve gastrectomy under general anesthesia using desflurane for maintenance.
| Patients and Methods|| |
After local institutional review board approval was obtained and all patients gave informed written consent, 40 morbidly obese patients [body mass index (BMI) >35 kg/m 2 and ASA physical status II-III] undergoing laparoscopic sleeve gastrectomy were included in the study. Exclusion criteria were memory impairment, psychosis, known or suspected electroencephalograph abnormality (e.g., epilepsy, previous brain operation), chronic use of psychoactive medication, and operation time exceeding 6 h. Patients were randomly allocated into two groups (20 patients each) as follows: Group 1 (non-BIS group): Desflurane was administered according to standard clinical practice (control group) and group 2 (BIS group): Desflurane was titrated to maintain a BIS value between 40 and 60 during surgery, and then to 60-70 during 15 min before the end of surgery. All patients were pre-medicated by esomeprazole 40 mg orally at the night of surgery, and metechlopramide 10 mg and lorazepam 2 mg orally by sip of water 3 h before surgery. Anesthesia was induced with 1.5-2 mg/kg intravenous propofol and 2 μg/kg intravenous fentanyl injected over 15-30 s. Intravenous rocuronium, 0.9 mg/kg, was administered to facilitate tracheal intubation and neuromuscular blockade. All patients were mechanically ventilated on 40% oxygen mixed with air to maintain an end-tidal carbon dioxide (ETCO2) concentration of 35-40 mmHg through Datex-Ohmeda S/5 anesthesia machine. Intravenous paracetamol 1 g was given to all patients of both groups over 15 min after induction of anesthesia and local infiltration with marcaine 0.25% was given by the surgeon before all skin incisions (five small incisions). BIS monitoring (BISA-2000 software 2.21, Aspect Medical Systems, Newton, MA, USA) was initiated at induction, and smoothing time was 30 s (only in BIS group). Standard monitoring [SpO 2 , electrocardiogram, ETCO2, indirect or direct blood pressure (BP), and esophageal temperature probe] was used in all patients. Desflurane 6% in 2 l/min fresh gas flow, mixed in air and oxygen, was administered to all patients after endotracheal intubation until skin incision; then the concentration was changed every 5 min as follows: Non-BIS group (control group), the anesthesiologist adjusted the desflurane concentration purely according to the clinical signs [heart rate (HR) and BP]. However, in BIS group, the anesthesiologist adjusted the concentration of desflurane to achieve a target BIS in the range 40-60. End-tidal concentration of desflurane was also regularly recorded (by Datex-Ohmeda S/5 monitor). During the operation, the patients in both groups were observed for signs of inadequate anesthesia (increased BP and HR 20% from baseline, lacrimation). Significant hypotension or bradycardia was defined as 20% reduction of the baseline figures. Any instances of inadequate anesthesia were managed by increasing the concentration of desflurane. Rocuronium neuromuscular blockade was maintained to a single twitch of the train of four. During the last 15 min of surgery, in the BIS group, the BIS value was gradually titrated to 60-70 by decreasing the inhaled anesthetic concentration. After skin closure and application of surgical dressing, neuromuscular blockade was reversed with neostigmine (0.07 mg/kg) and glycopyrrolate (0.015 mg/kg), desflurane was discontinued, and fresh gas flows were increased to 10 l/min. Mechanical ventilation (10 ml/kg ideal body weight) was continued until the first spontaneous respiration began, followed by assisted manual ventilation. A verbal command (open your eyes) was given every 1 min. After a train-of-four ratio higher than 0.9, a 5-s head lift was performed and patients were extubated. Times from discontinuation of the desflurane to eye opening and extubation were recorded. Recovery times (eye opening on verbal commands, and orientation to time, place, and person) were assessed at 1-min intervals. The time to extubation and also the time to achieve a modified Aldrete score (Appendix) of ≥ 9 were recorded. All recovery times, end-tidal desflurane concentration, and desflurane consumption per patient were recorded by blinded study anesthesia nurse. After extubation, patients were transferred fully awake on oxygen mask 4 l/min to the post-anesthetic care unit (PACU). All patients were observed in PACU for 3 h. Postoperative pain was evaluated at 5-min intervals using a 5-point verbal rating scale (0: No pain; 1: Light pain; 2: Moderate pain; 3: Intense pain; 4: Severe pain). Pain scores were treated with intravenous meperidine up to 1 mg/kg according to ideal body weight. All patients were discharged from the PACU after they fulfilled discharge criteria (stable hemodynamics, fully conscious, pain free with no nausea or emesis). At the time of discharge from the recovery room and 24 h after surgery, patients were asked whether they had bad dreams or recalled any intraoperative events. Desflurane consumption was calculated in milliliters through gas usage option of Datex-Ohmeda S/5 anesthesia machine.
Power analysis suggested that group sizes of 17 should be adequate to detect a significant difference (>25%) in the percentage of patients able to respond to initial command with α =0.05 and β =0.80. So, we enrolled 20 patients in each group. All data were analyzed using SPSS 15.0 for windows (SPSS Inc., Chicago, IL, USA). One-way repeated-measures analysis of variance (ANOVA) with post hoc Bonferroni correction was used to assess differences in mean between groups in respect of specific intraoperative events. The two-sample unpaired Student's t-tests were used to compare continuous variables: HR, mean arterial pressure (MAP), duration of anesthesia, recovery times, desflurane end-tidal concentration and consumption. Data were expressed as mean values ± SD unless otherwise stated. P values < 0.05 were considered statistically significant.
| Results|| |
Forty morbidly obese patients were enrolled in the present study (n0 = 20 in each group). There were no significant differences between the two groups regarding demographic data (age, height, weight; BMI) or duration of anesthesia and surgery [Table 1].
There were no statistical differences in intraoperative mean arterial BP [Figure 1] and mean HR [Figure 2] in both groups. The mean end-tidal concentrations of desflurane were significantly decreased in the BIS group compared to the non-BIS group (P < 0.05) [Figure 3].
|Figure 1: Intraoperative mean arterial blood pressure in the two groups. (Before = before induction, After = after induction)|
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|Figure 2: Intraoperative heart rate in the two groups (Before = before induction, After = after induction)|
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|Figure 3: Mean end‑tidal desflurane concentration (%) (After = after induction, ET = end‑tidal)|
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The mean desflurane consumption was significantly lower in the BIS group (124.8 ± 5.1 ml/patient) compared to the non-BIS group (150.6 ± 6.5 ml/patient) (P < 0.05) [Table 2]. Mean recovery times (time to eye opening to verbal command, extubation time, and orientation in time, place, and person) were significantly shorter in the BIS group (5.4 ± 1.15, 6.4 ± 1.4, and 10.1 ± 1.06 min, respectively) as compared to the non-BIS group (7.2 ± 2.1, 8.2 ± 3.1, and 13.2 ± 3.3 min, respectively) (P < 0.05) [Table 2]. There were no significant differences observed between the two groups regarding the time to obtain an Aldrete score of ≥ 9 [Table 2]. No nausea or vomiting was reported in the PACU. All patients were completely awake and discharged after 3 h from PACU without complications. There was no recall of intraoperative events in all patients of both groups. There were bad dreams in five patients (three in the non-BIS group and two in the BIS group) 24 h after surgery.
| Discussion|| |
The present study had demonstrated that using BIS monitoring not only led to rapid and improved quality of postoperative recovery of morbidly obese patients undergoing laparoscopic sleeve gastrectomy, but also decreased intraoperative desflurane consumption.
This study was designed to be a prospective randomized controlled single-blinded study as desflurane was titrated intraoperatively against objective measures such as BIS, HR, MAP, and end-tidal desflurane concentration. Early recovery times in the operating room (eye opening to verbal commands, extubation time, and orientation to time, place, and person) were also recorded by a blinded study anesthesia nurse, which may not constitute an investigator-associated bias. Also, in the PACU, the nursing staff did not have any idea about the study.
There was a significant difference in recovery times when comparing BIS-guided and non-BIS-guided anesthesia. These results are comparable to those reported in other studies that assessed titration of propofol, , desflurane, or sevoflurane , by using BIS monitoring, but not in morbidly obese patients. Song and other authors , had concluded that BIS monitoring allows reduction in the total amount of intraoperative anesthetic consumption and appears to decrease emergency and recovery times.
There were significant differences in the times of eye opening to verbal commands, extubation time, and orientation to time, place, and person between BIS and non-BIS groups; however, there were no significant differences between the two groups in obtaining Aldrete score of ≥ 9. Similar results were also reported by Guignard et al. Pavlin et al. also concluded that routine application of BIS monitoring is associated with a modest reduction in end-tidal anesthetic concentration and a similar reduction (11%) in recovery duration. Heavner et al. had demonstrated that use of BIS monitoring had improved recovery profiles in elderly patients anesthetized by desflurane and nitrous oxide. Other BIS-guided studies demonstrated that recovery time is reduced, compared with previous non-BIS-guided studies where the desflurane or sevoflurane dosages were based on MAC and hemodynamic response, whether mixed with nitrous oxide  or not. 
Song et al. failed to detect differences in total recovery duration and the duration of stay in the recovery unit between BIS-monitored and control groups.  In our study, patient stay in the PACU was determined by 3 h.
Significant reduction of the end-tidal desflurane concentration and desflurane consumption in the BIS group compared to the non-BIS group coincides with other studies , which reported that practitioners use lower concentrations of volatile anesthetics when they use information provided by cerebral monitors such as BIS and auditory evoked potential (AEP). Also, White et al. found that AEP and BIS monitoring can decrease the end-tidal desflurane concentration during anesthesia maintenance and can also decrease the discharge times after the end of anesthesia during laparoscopic ambulatory surgery. Recart et al. found that AEP monitoring can reduce the desflurane requirement by 26%.
The present study showed that the use of BIS monitoring in morbidly obese patients had reduced total desflurane consumption by 17.13% (124.8 ± 5.1 ml vs. 150.6 ± 6.5 ml in the non-BIS group) with consequent reduction in the total cost of the anesthetic.
It has been also shown in this study that excessive costs can be minimized without compromising clinical outcome and patient satisfaction. Anesthesia costs during surgery constituted only 5.6% of the total hospital costs and many opportunities may be found to reduce costs in operating suits. , Yll-Hankala et al. found that the sevoflurane saving was 40% in gynecological surgery patients who also received opioids. Guignard et al. reported 12% saving in isoflurane consumption when using BIS, which was explained as a result of the use of sufentanil and nitrous oxide. Pavlin et al. found, in a study of junior residents who had different durations of training, that a modest reduction of anesthetic used was reported with more senior residents (13%), so experience is an important factor in evaluating BIS values.
Use of cerebral monitors to minimize the intraoperative anesthetic drug consumption and improve the recovery process had raised concerns regarding the potentially deleterious effects of increased autonomic activity (e.g. myocardial ischemia) as well as the possibility of intraoperative awareness.  However, in the present study, intraoperative hemodynamic variables were not significantly different despite the fact that the BIS-guided group received 17.13% less desflurane. Furthermore, there were no significant differences in the adverse events during or after surgery, or in the incidence of bad dreams between the two groups, and none of the patients recalled intraoperative events. This was in accordance with White et al. who reported no recall of intraoperative events despite that patient in the AEP and BIS-guided groups received 28% less desflurane compared with the control group.
| Conclusion|| |
The use of BIS monitoring was effective in reducing intraoperative desflurane requirement (cost) and in shortening early recovery times after laparoscopic sleeve gastrectomy in morbidly obese patients without compromising the hemodynamic stability, adequacy of anesthesia, or patient outcome.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]