|Year : 2016 | Volume
| Issue : 4 | Page : 584-592
A comparative study of propofol and isoflurane for the maintenance of anesthesia in spine surgery using the bispectral index monitor: a randomized control study
Manisha, Babita, Tarun Lall, Bhupendra Singh, Kanchan Sharma, Rajat Dadhich
Department of Anaesthesia, Sawai Man Singh Medical College and Hospital, Jaipur, Rajasthan, India
|Date of Submission||09-Oct-2015|
|Date of Acceptance||26-May-2016|
|Date of Web Publication||12-Jan-2017|
Behind Tehseel, Chamad Gali, Ward No. 6, Nagar (Tehseel), Bharatpur (dist.), Rajasthan 321205
Source of Support: None, Conflict of Interest: None
Early awakening is required in spine surgery to perform neurological examination in the early postoperative period. Bispectral index (BIS) monitoring allows reduction in the total amount of anesthetic drugs and decreases the time for emergence and recovery. Thus, BIS monitor helps in reducing the incidence of awareness. Kinetics of propofol allows both induction and continuous intravenous maintenance of anesthesia with rapid recovery of consciousness that aids in performing neurological examination in the early postoperative period. This study was conducted to compare propofol and isoflurane in the maintenance of anesthesia during spine surgery using the BIS monitor.
Patients and methods
A total of 50 patients (American Society of Anesthesiologists grades I and II) scheduled for spine surgeries were divided into two groups (25 each). Group A received an infusion of propofol 5 mg/kg/h and group B received isoflurane 1% vol. for maintenance to keep the BIS value between 40 and 60. The groups were compared as regards pulse rate, systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, surgeons’ satisfaction, time to recovery, extubation time, and side effects.
Both groups were well matched for their demographic data and preoperative vital data. There was no significant difference in hemodynamic parameter between the two groups. The mean recovery time was significantly different (P<0.001) between groups, with earlier recovery in the propofol group (8.14±0.805 min) compared with the isoflurane group (9.06±0.766 min). Values for BIS were similar between the two groups during surgery (P>0.05). Incidence of postoperative nausea and vomiting was 35% lower in group A compared with group B. The quality of surgical field was acceptable in both groups but slightly better in the propofol group. No other major complications were noted in our study.
Propofol-based anesthesia provides early and better recovery with clear headedness for early neurological assessment for spine surgery.
Keywords: awareness, bispectral index, general anesthesia, isoflurane, propofol, spine surgery
|How to cite this article:|
Manisha, Babita, Lall T, Singh B, Sharma K, Dadhich R. A comparative study of propofol and isoflurane for the maintenance of anesthesia in spine surgery using the bispectral index monitor: a randomized control study. Ain-Shams J Anaesthesiol 2016;9:584-92
|How to cite this URL:|
Manisha, Babita, Lall T, Singh B, Sharma K, Dadhich R. A comparative study of propofol and isoflurane for the maintenance of anesthesia in spine surgery using the bispectral index monitor: a randomized control study. Ain-Shams J Anaesthesiol [serial online] 2016 [cited 2017 Jun 27];9:584-92. Available from: http://www.asja.eg.net/text.asp?2016/9/4/584/198249
| Introduction|| |
Awareness can be defined as the subjective experience of external or internal stimuli and one’s own existence in space and time at any given moment . Awareness during general anesthesia (GA) is undesired, unanticipated, patient wakefulness during surgery or recall afterward. A recent review of reported cases of awareness suggested the absence of volatile agents or intravenous agents during maintenance, with overly light anesthesia as the most common cause. The major consequence of intraoperative awareness in a patient is its long-time psychological event such as post-traumatic stress disorder. Symptoms may be as severe as avoidance of medical situations .
The bispectral index (BIS) is an objective method of assessing the depth of anesthesia. In October 1996, the BIS system achieved approval from Food and Drug Administration as the first electroencephalogram (EEG)-based monitor of anesthetic effect. BIS reduces complex EEG processing to a simple number ranging from 100 to 0. BIS decreases with increasing depth of anesthesia, and an adequate level of anesthesia is achieved with BIS ranging from 40 to 60. BIS monitoring allows reduction in the total amount of anesthetic that patients are exposed to and appears to decrease time for emergence and recovery. BIS monitor helps in reducing the incidence of awareness. Recommended level of surgical anesthesia is between 40 and 60 ,,.
Awareness during spine surgery can be avoided with either inhalational agent or intravenous agent. Interest in total intravenous anesthesia has risen due to the advent of propofol, the kinetics of which allows both induction and continuous intravenous maintenance of anesthesia with rapid recovery of consciousness . Propofol has been shown to be superior to inhalational anesthesia in terms of rapid awakening and return to street fitness . Early awakening aids in performing neurological examination in the early postoperative period. The standard use of halothane or isoflurane does not allow quick assessment of these patients following their use. Moreover, the use of total intravenous anesthesia avoids local and global pollution seen with inhalational anesthetic agents . Unique to propofol are its antipruritic properties and antiemetic effects. Its antiemetic effects make it a preferred drug for outpatient anesthesia ,.
Isoflurane is a volatile anesthetic used for the maintenance of anesthesia. Isoflurane reduces cerebral metabolic oxygen requirements, and at two minimum alveolar concentration it produces an electrically silent EEG .
The aim of this study was to assess and compare hemodynamic parameters, time to recovery, surgical field, and significant side effects of propofol and isoflurane in the maintenance of anesthesia during spine surgery using BIS monitor.
| Patients and methods|| |
This prospective randomized study was conducted in SMS Medical College and Attached Hospitals, Jaipur, after approval from the Institutional Ethical Committee. Informed consent was obtained from each patient. A total of 50 American Society of Anesthesiologists I/II patients between 20 and 50 years of age with weight ranging from 40 to 80 kg who were posted for elective spine surgery under GA were included in this study. Patients having compromised renal, pulmonary, and cardiac status and known allergy to anesthetic agents were excluded from the study. The research methodology was prospectively randomized using the sealed envelope technique into two groups of 25 patients each: group A, the propofol group, and group B, the isoflurane group.
Preanesthetic assessment was carried out before the day of surgery. All patients received 0.5 mg of alprazolam as oral premedication the night before surgery. Baseline monitoring of heart rate, noninvasive blood pressure, ECG, and pulse oximeter (SpO2) was carried out. Two intravenous lines were secured. All patients were premedicated with midazolam 0.05 mg/kg, intravenous, glycopyrrolate 0.005 mg/kg, intravenous, and fentanyl 2 mcg/kg, intravenous. Induction was carried out with thiopentone 5 mg/kg, intravenous in a titrated manner until loss of eyelash reflexes and then intubated with an appropriate size endotracheal tube after adequate muscle relaxation was provided with succinylcholine 0.5 mg/kg, intravenous. End-tidal carbon dioxide monitor was connected to the endotracheal tube. A unique Zipprep electrode (Aspect Medical System, One Upland Road, Norwood, Delaware, USA) was connected to the forehead and the sensor connected to the BIS monitor, with a BIS value of 40–60 throughout the surgery. Maintenance was carried out with N2O+O2 in 60 : 40 ratio in both groups. In group A, infusion of propofol 5 mg/kg/h was administered; the infusion was tapered toward the end of the surgery and was stopped at the time of skin closure. Patients in group B received isoflurane 1% vol. for maintenance; it was tapered toward the end of the surgery and stopped at the time of skin closure.
Muscle relaxation in both groups was achieved with the injection atracurium 0.5 mg/kg, intravenous, bolus loading followed by 0.1 mg/kg for maintenance. Analgesia was achieved with fentanyl 2 mcg/kg at induction and 1 mcg/kg thereafter every 1 h until the end of the surgery. Surgery was performed in prone position. At the end of surgery, reversal was achieved with neostigmine 50 mcg/kg and glycopyrrolate 10 mcg/kg, intravenous. Intraoperative hypotension was managed with fluid bolus and mephentermine 6 mg, intravenous bolus. Hypertension was managed by increasing anesthetic depth or analgesia or both.
Recovery time was recorded from duration of infusion or inhalational agent to eye opening on command, head lift, and achievement of Aldrete score of 9 (time from stoppage of infusion or inhalation to BIS=80). Extubation time was noted from end of all infusion or inhalation to extubation.
The operating surgeon graded the quality of surgery as very good, good, and unsatisfactory. For the purpose of analysis, the first two grades were considered acceptable for surgery and the latter two were considered unacceptable. Surgeon’s satisfaction was based on blood loss, surgical field congestion, and surgeon’s opinion about operative condition.
Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and heart rate were recorded every minute, starting just before induction until surgical incision, and thereafter every 10 min throughout surgery. Both groups were compared in relation to hemodynamic changes, surgeon’s opinion about surgical field, recovery time, extubation time and quality of anesthesia, and postoperative nausea and vomiting (PONV).
Statistical analysis was performed on Excel sheet MS Office Excel 2007 (Microsoft Corporation, Redmond, WA 98052, United States of America) and analyzed statistically using SPSS (International Business Machines Corporation (IBM), America, Armonk, New York) Statistical software (ver.18.0.0) and XLStat (Microsoft Corporation, United States).
Quantitative data were expressed in terms of mean±SD. Qualitative data were summarized in the form of proportions and percentage and analyzed using the χ2-test. The difference in means between the two groups was inferred using the unpaired t-test. The difference in BIS value was inferred using the Mann–Whitney test. The levels of significance and α-error were kept 95 and 5%, respectively, for all statistical analyses.
P-values less than 0.05 were considered as significant and P-value more than 0.05 as statistically nonsignificant.
| Results|| |
All data were expressed as mean±SD. The two groups were comparable as regards patients’ characteristics with respect to age, sex, American Society of Anesthesiologists physical status, and duration of surgery ([Table 1]). The mean baseline variables were comparable in both groups ([Table 2]). There was no significant difference between groups in terms of demographic characteristics and baseline parameters (P>0.05).
Figure 1 shows the comparison of mean pulse rate. In group A, the baseline pulse rate was 92.12±6.60, and after intubation it increased to 100.24±7.99. At the start of infusion, pulse rate was 102.72±13.15, and then it decreased until end of surgery. In group B, pulse was 92.92±5.53 at baseline. After intubation, it increased to 103±7.39. At the start of infusion, pulse rate was 102.60±10.21, and then decreased until end of surgery to 81.52±8.72. No significant difference was observed among the groups as regards pulse rate at different time intervals.
|Figure 1: Comparison of mean pulse rate (per min) among the groups at different time interval.|
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Figure 2 shows the comparison of mean SBP. In group A, baseline SBP was 115.6±9.9. SBP decreased to 110.4±10.7 after induction. After intubation, it increased to 116.4±14.8. At the start of infusion, SBP was 121.8±12.3 and then decreased to 96.2±4.3 at 15 min after infusion, and it again decreased to 96.2±4.74 at 30 min after infusion. At the end of surgery, it further decreased to 99.6±4.61. In group B, baseline SBP was 112.6±9.0. SBP was 112.8±13.3 after induction. After intubation, it increased to 120.8±12.6. At the start of infusion, SBP was 118.5±11.0, and then decreased up to 75 min after infusion, and remained comparable to baseline until the end of surgery. No significant difference was observed in mean SBP (mmHg) among the groups at different time intervals (P>0.05).
|Figure 2: Comparison of mean systolic blood pressure (mmHg) among the groups at different time interval.|
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Figure 3 shows the mean DBP. In group A, the baseline DBP was 84.76±6.89. After intubation, it increased to 93.56±6.17. In group B, baseline DBP was 83.88±5.16. After intubation, it increased to 92.68±4.97. After infusion, DBP decreased further until end of surgery in both groups. No significant difference was observed in mean DBP among the two groups at different time intervals.
|Figure 3: Comparison of mean diastolic blood pressure (mmHg) among the groups at different time interval.|
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No significant difference was observed as regards MAP among the groups at different time intervals ([Figure 4]).
|Figure 4: Comparison of mean blood pressure (mmHg) among the groups at different time interval.|
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Time to recovery
Time to recovery (min) in group A was 8.14±0.805 and that in group B was 9.06±0.766. Time to recovery was significantly longer in group B compared with group A. The difference was highly significant (P<0.001) ([Table 3] and [Figure 5]).
|Table 3: Distribution of the cases according to mean time to recovery (min)|
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|Figure 5: Distribution of the cases according to mean time of recovery (min).|
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Significantly higher mean was observed in group B as compared with group A as regards mean time of recovery (min).
Bispectral index score
Figure 6 shows BIS value intraoperatively, which was in the range of 40–60. There was a nonsignificant difference between the two groups at different time intervals.
|Figure 6: Comparison of mean bispectral index score among the groups at different time interval.|
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Postoperative nausea and vomiting
Figure 7 shows the postoperative incidence of nausea and vomiting, being less in patients who received propofol (40%) compared with isoflurane (75%).
|Figure 7: Postoperative nausea and vomiting. Arrow shows the significant difference.|
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Quality of surgical field
Figure 8 shows the quality of surgical field, which was assessed by the operating surgeon and graded as very good, good, or unsatisfactory. The surgeon was blinded to the anesthetic technique used. The quality of surgical field as stated by the surgeon was acceptable in both groups, but slightly better in the propofol group, as told by the blinded operating surgeon as regards bloodless operating field and less blood loss.
|Figure 8: Comparison of surgeon’s satisfaction score between the groups.|
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There was a nonsignificant difference between the two groups in terms of surgeon’s satisfaction at different time intervals.
| Discussion|| |
This study was conducted to observe the effects of propofol and isoflurane in the maintenance of anesthesia during spine surgery using BIS monitor. In this systematic analysis of the literature, the EEG-based BIS monitor has proven to be a useful indicator of anesthetic depth . Early awakening is required in spine surgery to perform neurological examination in the early postoperative period . Studies have shown that propofol maintains cerebral and spinal cord blood flow autoregulation in experimental animals . Recent studies using the BIS as a guide to anesthetic depth have shown that a large number of patients can be ‘fast-tracked’ when anesthetic depth is monitored . Consequently, appropriate depth of anesthesia is an important factor in quick recovery. Propofol is a good drug for the maintenance of anesthetic depth, as it avoids the disadvantages of inhalational anesthetics. The pharmacokinetic profile of propofol favors its use as a continuous infusion for maintenance of anesthesia.
The anesthetic gases used for the maintenance of anesthesia have significant health hazard. Prolonged exposure to anesthetic gases lead to drowsiness and blunting of reflexes of operating room personnel. Nitrous oxide is a green house gas and can also indirectly contribute to ozone layer depletion .
In our study, there was no significant difference in hemodynamic parameter when isoflurane or propofol was used for the maintenance of anesthesia. On analysis, we found that early recovery was characterized by opening eyes and obeying commands.
Postoperative complications, specifically PONV, were significantly less frequent in the propofol group compared with the isoflurane group.
In both study groups, there was a significant fall in the mean pulse rate, SBP, DBP, and MAP below baseline after induction (P<0.05), but these increased after intubation and remained above baseline at all time points, with significant differences at all stress points − that is, just after reversal and just after extubation (P<0.05). The mean pulse rate, SBP, DBP, and MAP in group A and group B decreased during infusion, but the change was not statistically significant (P>0.05). None of the patients developed severe hypotension unresponsive to fluids. After extubation, all vitals increased to cross baseline, but the difference was not statistically significant (P>0.05).
Price et al. , Gupta et al. , and Mishra  in their studies found this fall in mean pulse rate, SBP, DBP, and MAP to be statistically significant (P<0.05). After induction, all vitals decreased further; this may be attributed to the additive hypotensive effect of propofol in group A and isoflurane in group B.
Comparison between the two groups revealed that the mean BIS value was comparable at baseline and all time points during maintenance period (P>0.05). In both groups, there was a significant fall in the mean BIS value just before intubation. Thereafter, it remained significantly below baseline at all time points (P<0.05) after intubation, to remain nearly constant until the end of the surgery, with further increase after reversal and extubation. BIS value intraoperatively remains within the range of 40–50. Price et al.  and Gupta et al.  also noted the same track in their study. In a study conducted by Mishra , BIS was comparable between two groups at all time points during the maintenance period (P>0.05).
Time from end of all infusions to BIS=80 (recovery time) and time from end of all infusions to extubation (extubation time) in group A (propofol) were found to be significantly less (P<0.05) than that in group B (isoflurane) in our study.
In our study, recovery profile and clear headedness were more rapid for propofol than for isoflurane anesthesia. Similar result was seen in the study by Doze . Gupta et al.  concluded that home discharge was significantly earlier with propofol. However, recovery profiles can also be influenced by concomitant analgesics used preoperatively and the depth of anesthesia attained toward the end of the operation. Mishra  did not find any statistical differences in recovery time for eye opening, extubation time, limb lift, and Aldrete scores between groups.
PONV were significantly more common with inhaled anesthetics compared with propofol, and the use of antiemetic was also more common with inhaled anesthetics. Tramèr et al.  in a meta-analysis found that maintenance of anesthesia with propofol is an advantage compared with other anesthetics in PONV. The incidence of PONV was 40% in the propofol group and 75% in the isoflurane group in our present analysis. Propofol appears to possess antiemetic property that contributes to a lower incidence of emetic sequel after GA. In fact, a subanesthetic dose of propofol (10–20 mg) has also been successfully used to treat nausea and vomiting in the early postoperative period . This is due to its antidopaminergic activity and depressant effect on chemoreceptor trigger zone.
Other than headache, which occurred at a higher frequency with isoflurane compared with propofol, and drowsiness, which occurred at a significantly higher frequency with isoflurane, no other significant differences were found in the incidence of postoperative complications.
The quality of surgical field as stated by the surgeon was acceptable in both groups in our study, but slightly better in the propofol group as told by the blinded operating surgeon with respect to bloodless operating field and less blood loss.
Eberhart et al. , Ahn et al. , and Pavlin et al.  also demonstrated superior surgical field with propofol in sinus surgery. This may be due to steady state plasma level of propofol achieved with continuous infusion providing relatively low blood pressure, resulting in less blood loss and lesser surgical field congestion.
Our study also is in agreement with the study by Hannaa et al. , who concluded that propofol/remifentanil intravenous anesthesia for spinal fixation surgery is beneficial, allowing properly controlled hypotension, reduced intraoperative bleeding, decreased need for blood transfusion, and improved surgical field visibility, compared with isoflurane/remifentanil anesthesia.
Limitation and future
Limitation of the present study was the use of BIS as the only mode of measuring depth of anesthesia for the patients. In addition to providing minimum information on analgesia, the interpretation of BIS may be confounded by the use of N2O. The administration of muscle relaxants was in the form of time-bound boluses and not guided by neuromuscular monitoring. To increase precision of the current topic, future studies may be undertaken using target control closed loop propofol infusion, entropy monitoring, neuromuscular monitoring, and different maintenance doses.
| Conclusion|| |
Propofol-based anesthesia provides early and better recovery with clear headedness for early neurological assessment for spine surgery. This technique is also helpful in achieving an ecofriendly environment around the operating area.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2], [Table 3]