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NEUROSURGICAL ANESTHESIOLOGY

Planning for Early Emergence in Neurosurgical Patients: A Randomized Prospective Trial of Low-Dose Anesthetics

From the Department of Neuroanesthesiology, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, India.

Address correspondence to Dr. Hari Hara Dash, Professor and Head, Department of Neuroanesthesiology, Chief of Neurosciences Centre, Room no 709-A, CN Centre, AIIMS, New Delhi 110029, India. Address e-mail to dr.harihardash{at}gmail.com.

Abstract

BACKGROUND: For early detection of a cerebral complication, rapid awakening from anesthesia is essential after craniotomy. Systemic hypertension is a major drawback associated with fast tracking, which may predispose to formation of intracranial hematoma. Although various drugs have been widely evaluated, there are limited data with regards to use of anesthetics to blunt emergence hypertension. We hypothesized that use of low-dose anesthetics during craniotomy closure facilitates early emergence with a decrease in hemodynamic consequences.

METHODS: Three emergent techniques were evaluated in 150 normotensive adult patients operated for supratentorial tumors under standard isoflurane anesthesia. At the time of dural closure, the patients were randomized to receive low-dose propofol (3 mg · kg^–1 · h^–1), fentanyl (1.5 µg · kg^–1 · h^–1) or isoflurane (end-tidal concentration of 0.2%) until the beginning of skin closure. Nitrous oxide was discontinued after head dressing.

RESULTS: Median time to emergence was 6 min with propofol, 4 min with fentanyl, and 5 min with isoflurane (P = 0.008). More patients had hypertension in the pre-extubation compared with extubation or postextubation phase (P = 0.009). Comparing the three groups, fewer patients required esmolol with fentanyl use overall, and in the pre-extubation phase (P = 0.01). Significant midline shift in the preoperative cerebral imaging scans was found to be an independent risk factor for emergence hypertension.

CONCLUSIONS: Pain during surgical closure may be an important cause of sympathetic stimulation leading to emergence hypertension. The use of low-doses of fentanyl during craniotomy closure is more advantageous than propofol or isoflurane for early emergence in neurosurgical patients and is the most effective technique for preventing early postoperative hypertension.

Predictable and early emergence from anesthesia is a major concern in neurosurgical patients. A feared complication after intracranial surgery is the development of postoperative hematoma, the incidence being 0.8%–2.2%.1 Rapid emergence after craniotomy is a common practice, the goal of which is to permit early neurological examination.2 Nevertheless, fast-tracking has its own pitfalls. For example, systemic hypertension often accompanies rapid emergence and may predispose to formation of intracranial hematoma.3 The occurrence of hypertension during emergence has been reported to be more than 90% in neurosurgical patients.4,5

Various nonanesthetic drugs; β-blockers, combined -β-blockers, calcium channel blockers, and lidocaine have been tried successfully to blunt the hemodynamic response to emergence and extubation.5–7 These drugs have disadvantages of their own.5,8–10 It is probably more convenient and easier for the anesthesiologist to titrate low-dose anesthetics at the end of surgery to control hemodynamic changes. Among the anesthetics, propofol has been shown to be effective in attenuating the sympathetic response to tracheal extubation in cardiac patients.11,12 A narcotic infusion seems a logical choice because several studies have demonstrated that opioids could blunt the hemodynamic response to extubation.13,14 Early emergence with good hemodynamic control requires meticulous planning. Although an awakening sequence has been suggested in neurosurgical patients,1 there has been no trial to address this issue.

In our center, we encounter hypertension during emergence in more than 80% of our patients when no specific measures for prevention are taken during craniotomy closure. This led us to hypothesize that treatment with low-dose propofol, fentanyl, and isoflurane during craniotomy closure might be helpful in achieving the clinical end-points of this study (i) an early emergence, and (ii) prevention of the associated hypertensive response.

METHODS

The study was conducted on 150 adult patients of either sex, aged 20–60 yr with full preoperative Glasgow Coma Score (GCS) undergoing elective craniotomy for supratentorial tumors. The human ethics and research committee of All India Institute of Medical Sciences, New Delhi, India, approved the study protocol. Written informed consent was obtained from all patients. The tumor characteristics were noted from the preoperative computed tomographic and magnetic resonance imaging scans. Randomization to one of the three equally distributed groups was done after induction of anesthesia by picking a sealed envelope.

Patients with ischemic and/or congestive heart disease, hypertension, chronic obstructive pulmonary disease, diabetes mellitus, and hepatic and renal dysfunction were not included in the study. After admission into the study, patients were excluded if the continuation of the designed protocol was not possible (for example, as in one case of severe intraoperative brain bulge) or when postoperative ventilation was required.

Anesthesia
All chronic patient medications were continued (e.g., dexamethasone, anticonvulsants) until the morning of surgery. Oral diazepam 10 mg was administered to all patients on the night before surgery, and all patients received IM glycopyrrolate 0.2 mg as premedication before being moved to the operation room. Preinduction monitoring (Datex Engstrom AS/3 anesthesia monitor, Helsinki, Finland) consisted of 5-lead electrocardiography, heart rate, arterial (radial) blood pressure, and pulse oximetry. Three recordings of heart rate and mean arterial blood pressure (MABP) were taken at 1-min intervals. The mean of the three recordings was registered as the baseline heart rate and MABP.

Induction was achieved with fentanyl 2 µg/kg, followed by thiopental 4–6 mg/kg. Tracheal intubation was facilitated with rocuronium 1 mg/kg. Thiopental 1–2 mg/kg was administered immediately before the Mayfield head holder was applied. Additional postinduction monitoring consisted of nasopharyngeal temperature, neuromuscular monitoring, and central venous pressure, whenever necessary. Ventilation was adjusted so as to achieve an end-tidal carbon dioxide tension of around 30 mm Hg (Datex Ohmeda Aestiva/5, Madison, USA). Until the beginning of the study, anesthesia was maintained with nitrous oxide in oxygen (2:1), 0.5%–0.6% end-tidal isoflurane, and intermittent boluses of fentanyl. Vecuronium was administered until the beginning of skin sutures according to the need to maintain a maximum of single twitch on neurostimulation. The conduct of study protocol and recordings were done by two different anesthesiologists who were not blinded to the study groups.

Normal body temperature was maintained using a forced-air warming blanket. After completion of head dressing, the neuromuscular blockade was reversed with neostigmine 0.05 mg/kg and glycopyrrolate 0.01 mg/kg. The trachea was extubated after (a) adequate reversal of neuromuscular blockade, (b) return of spontaneous respiration, (c) maintenance of adequate oxygen saturation on the pulse oximeter, and (d) when the patient followed commands. Thereafter, the patients were moved to the neurosurgical intensive care unit (NSICU). Intraoperative use of IV fluids, blood loss, and urine output were recorded. Pain score, nausea and/or vomiting, convulsions, hemodynamics, and respiration were monitored and recorded in the NSICU by a staff nurse who was unaware of the study group.

Study Protocol
Before commencing the study, a two-staged pilot study was conducted. During the first stage, individual drugs (propofol/fentanyl/isoflurane) were used in varied doses to study their effects on hemodynamics and emergence. In the second stage of the pilot study, the doses of individual anesthetic drugs were optimized to the lowest possible to enable early emergence with the least hemodynamic disturbances. Once the optimal dose was achieved, the study protocol was formulated.

At the beginning of dural closure, the patients were dispensed the anesthetic regimen to which they were randomized. They were divided equally into three groups of 50 each. The first group consisted of low-dose propofol infusion, whereas in the second and third groups the effects of fentanyl and isoflurane, respectively, were assessed. The study period extended from the beginning of dural closure to 1 hr after tracheal extubation. Each group had an anesthetic plan (Table 1).

Hemodynamics
Heart rate and MABP were monitored continually throughout the duration of anesthesia and for 1 hr after tracheal extubation. The study period was segregated into three phases: pre-extubation (beginning of dural closure to 1 min before extubation), extubation (1 min before and a minute after extubation of trachea) and postextubation phase (rest of the study duration). The recordings were made every 5 min from the time of commencement of study until extubation. For postextubation, the recordings were done every minute for the first 5 min and then every 15 min until completion of the study. Hypertension (defined as an increase of MABP >20% of baseline value and sustained for more than 1 min) was treated with a bolus of esmolol 1 mg/kg and thereafter 0.5 mg/kg, whenever deemed necessary. Esmolol is a short-acting β-adrenergic blocking drug (t_1/2 = 9 min), which effectively blunts hypertension in patients after craniotomy.5 If hypertension was not amenable to esmolol, nitroglycerine or nitroprusside infusion was to be considered. Hypotension (defined as a decrease of MABP <70 mm Hg for more than a minute) was managed with fast infusion of crystalloids. If this was not effective, a vasopressor (mephentermine/ephedrine) was used.

Emergence and Recovery
Emergence from anesthesia was defined as the interval between completion of head dressing (when nitrous oxide was discontinued) and extubation. The patients who could be extubated within 15 min after completion of dressing were considered to have had early emergence. Emergence, recovery (GCS), and respiration were assessed for 1 h after extubation. GCS and respiratory variables were recorded at 5, 15, 30, 45, and 60 min postextubation. The total dose of fentanyl used during surgery was calculated and compared among the groups. Any episode of respiratory insufficiency (hypoventilation) was noted. Pain was assessed using a verbal rating scale (0–10), 0 being no pain, 1–3 mild, 4–6 moderate, and 7 or more as severe pain. Rescue analgesic (score 5) consisted of IM ketorolac 30 mg.

Any incidence of postoperative nausea and vomiting was recorded and treated with IV metoclopramide 10 mg. All patients were interviewed on the second postoperative day for awareness during anesthesia using the modified Brice interview.15

Statistical Analysis
The parametric data were compared among groups using one-way analysis of variance, whereas the post hoc analysis for the same data was performed using a Bonferroni correction. Nonparametric data were compared using Pearson’s ² or Kruskal–Wallis test. Categorical data were analyzed with the Fisher’s exact test. Post hoc analysis for the nonparametric data was performed with Mann–Whitney test by adjusting the level of significance with the number of treatment groups. Heart rate and MABP were compared using repeated measure analysis of variance. Multiple logistic regression analysis was used to identify risk factors for emergence hypertension. A P value <0.05 was considered statistically significant.

RESULTS

One hundred and fifty patients were enrolled in the study. Fourteen patients (3 in the propofol group, 5 in the fentanyl, and 6 in the isoflurane group) were excluded because of the need for postoperative ventilation because of surgical reasons. Hence, the data were compared for 47 propofol group patients, 45 fentanyl, and 44 isoflurane. The demographic profiles were comparable among the three groups (P > 0.05), except for age (P = 0.008; Table 2).

Throughout the various periods, intraoperative fluid requirements were comparable among the three groups. Fentanyl use was significantly higher in the second group (Table 3). The intergroup temperatures were similar at the time of tracheal extubation (Table 3).

Heart rates were comparable among the three groups at baseline and at most times during the study period (Fig. 1B). Propofol use was associated with less tachycardia during extubation compared with the fentanyl group (P = 0.01).

View larger version (21K): [in this window] [in a new window]   Figure 1. Data for the three groups at different stages of study period. (A) Mean arterial blood pressure (MABP); (B) Heart rate (HR). Values are mean. Error bars represent standard deviation of mean vales. #P < 0.05, comparing the three study groups at various time points.

Baseline MABP was not comparable among the three groups. Therefore, the baseline MABP was adjusted as a covariate for intergroup comparison at various time points (Fig. 1A). Significant hypotension (P = 0.03) was observed in the propofol group at the time of dural closure, when compared with the isoflurane group (Fig. 1A). A vasopressor was required in 30 patients in the propofol group, whereas only six patients in the fentanyl group and 10 patients in the isoflurane group required a vasopressor (P < 0.001). The increase in MABP was not different among the three groups at the time of extubation (Fig. 1A). In the postoperative period, MABP was better controlled in the fentanyl group when compared with the propofol and isoflurane groups (P < 0.05; Fig. 1A).

Comparing the three groups for the entire study period (pre-extubation, extubation, and postextubation periods), 17 (36%) patients had hypertension in the propofol group, whereas the fentanyl and isoflurane groups had 11 (24%) and 24 (55%), respectively (P = 0.01, Fig. 2). Post hoc analysis for the overall study period revealed a significant difference only in the fentanyl and isoflurane groups (P = 0.003; Fig. 2). In the pre-extubation period, 8 (18%) patients had hypertension in the fentanyl group compared with 12 (25%) in the propofol and 20 (45%) in the isoflurane group (P = 0.01, Fig. 2). Post hoc analysis of the pre-extubation data found a significant difference only between the fentanyl and isoflurane groups (P = 0.005; Fig. 2). In the extubation and postextubation period, there was no intergroup difference in the number of patients who had hypertension (Figs. 2 and 3).

View larger version (11K): [in this window] [in a new window]   Figure 2. The number of patients who had hypertension in each group.

View larger version (11K): [in this window] [in a new window]   Figure 3. Hemodynamic characteristics: The percentage rise in MABP during extubation when compared with baseline (P > 0.05, comparing the three groups).

Multiple logistic regression analysis was done using various independent variables to identify the risk factors for emergence hypertension (Table 6). Emergence hypertension was the dependent variable and the treatment groups were also included. The results indicate that the patients who had a shift of midline structures of more than 5 mm in the preoperative computed tomographic or magnetic resonance imaging scans were 2.39 times at higher risk (95% confidence interval = 1.18–4.68) for emergence hypertension than those who had midline shift of 5 mm or less (P = 0.016).

DISCUSSION

The present study highlights two important observations. Fentanyl use was associated with early emergence when compared with propofol, but not with isoflurane. Second, the use of fentanyl infusion was effective in preventing emergence hypertension when compared with isoflurane but not propofol. However, propofol was associated with more hypotension. Comparing the three regimens for emergence, it seems reasonable to infer that fentanyl infusion is the most effective technique for achieving the two clinical end-points of the study, i.e., early awakening after craniotomy and prevention of emergence hypertension.

It is important to limit the hemodynamic consequences during fast-tracking in neurosurgical patients to prevent cerebral complications such as worsening of cerebral edema, intracranial hemorrhage, and postoperative delirium.3,16 Therefore, the anesthetic technique should result in quick awakening with minimal hemodynamic perturbations. In the study by Todd et al., the emergence from anesthesia was early (5 min), but the incidence of hypertension was very high (87%–98%).4 In the study by Gauthier et al., although fewer patients (25%) required antihypertensive therapy, the time to emergence was longer (15 min).17 The data from these studies suggest that the dual benefits of early awakening and hemodynamic control are difficult to achieve.

In two different studies, fentanyl use had a similar emergence time as in the present study, but with more frequent hypertension.4,18 During patients’ recovery from anesthesia, Bilotta et al. observed hypertension in only 14% of their patients with the use of sufentanil along with propofol.19 However, the mean time to tracheal extubation was 19 min in their patients. The dose and the timing of discontinuing an opioid infusion may be important in determining recovery and the associated hypertension.

Use of propofol infusion in the present study did not provide earlier emergence, an observation similar to that of Talke et al., where sequential administration of isoflurane and propofol was not associated with early recovery when compared with isoflurane alone.20 There were 12 patients in the propofol group, whereas 10 and 7 patients in the fentanyl and isoflurane groups, respectively, who did not gain a full GCS during the study period. Most of these patients did not have spontaneous eye opening but responded to verbal commands. However, all of them recovered. There were concerns in the past over the use of opioids towards the end of the surgery as it may delay emergence. Recent studies, including ours, indicate that this is not the case with current drugs.

Overall, emergence hypertension was observed in 38% of our patients. The results are comparable to those observed by Bilotta et al. where use of remifentanil/sufentanil along with propofol resulted in hypertension after craniotomy in only 37% of patients.19 Talke et al. reported hypertensive episodes in 50% of their patients, whereas Magni et al. observed hypertension during recovery from intracranial surgery in 29% of their patients.20,21 Prophylactic administration of labetalol at the end of surgery likely resulted in less frequent episodes of hypertension in the latter study.

The pathophysiology of emergence hypertension is complex. To simplify our analysis of this phenomenon, we segregated the study period into three phases: pre-extubation, extubation, and postextubation. Significantly more patients had hypertension in the pre-extubation period compared with the extubation and postextubation periods. This could probably be related to pain during surgical closure leading to sympathetic stimulation and an increase in MABP. The need for antihypertensive therapy was significantly less with fentanyl infusion during this period. During extubation, the increase of MABP and use of esmolol were similar among the three groups. Forty-five percent of patients had an increase in MABP over 20% of baseline during extubation. Of these, only 34% required antihypertensive therapy because increase in MABP lasted less than 1 min. These findings suggest that the stress of extubation is transient, and that treatment may not be required in most patients. In the postextubation period, though there was an overall difference in the number of patients who required treatment for hypertension, post hoc analysis did not reveal any significant difference among the groups (P > 0.05, Fig. 2). However, when MABP was compared among the three groups during the postextubation period, the values were significantly lower in the fentanyl group at various time points (P < 0.05, Fig. 1A). There was no intergroup difference in the pain scores and analgesic requirement. We statistically analyzed the relationship between the relative change in MABP during the recovery period (compared with baseline values) with pain scores and analgesic requirement. However, no such relationship could be found. From the above observations, it may be deduced that pain during surgical closure, rather than during the postoperative period, is an important trigger for sympathetic stimulation. When the anesthetics are discontinued towards the end stage of surgery, there is stress caused by arousal, and this is compounded by the presence of an endotracheal tube.22 The use of low-doses of short-acting opioids appears to be more appropriate in limiting the sympathetic responses during craniotomy closure.

The postoperative complications and the stay in the NSICU were comparable among the groups. Although the incidence of postoperative nausea and vomiting was higher in the fentanyl group (51%), it was not statistically different from the other groups and is comparable to the reported incidence in craniotomy patients.2 Although there was no statistical difference among the groups, the incidence was numerically lower in the propofol group, which is consistent with the antiemetic properties of propofol.

A shift of midline structures for more than 5 mm in the preoperative cerebral imaging scans was an independent risk factor for emergence hypertension. The cut-off value of 5 mm for midline shift was obtained from the area under the curve by taking hypertension as a dependent variable, which also has clinical significance. This observation indicates that patients who had a mean value of midline shift more than 5 mm were more prone to emergence hypertension than those who had a mean value <5 mm. In each group, the relationship between midline shift and hypertension was studied using the ² test, and no significant effect was found (P > 0.05). Although the risk remains, midline shift does not appear to influence the clinical interpretation of the anesthetic techniques of our study on emergence hypertension.

There are a number of methodological issues that deserve mention. The use of only one dose of each drug and the absence of an assessment of anesthetic depth is a drawback of this study, but the doses used are consistent with common clinical practice. Although the difference in the age among the groups could be a confounding factor, we did a univariate analysis and found that there was no influence of age on outcome of our study. An additional shortcoming was that this study was partially blinded. The anesthesiologists were not blinded to the different groups in the operation room, which may be a source of potential bias due to different handling of the treatment groups. However, we minimized the bias by blinding the observers in the NSICU and the data analysis was performed by individuals blinded to patient identity. Lack of a control group where no specific measures are undertaken was another drawback of this study.

Based on the incidence of hypertension in our center and having done the pilot trial, the sample size needed for a definitive study would be more than 2000 patients per group to have a power of 90% with a 5% level of significance. Hence, we are presenting this as a preliminary study. We decided upon a sample size of 150 patients to address this issue. We did a power analysis for the primary end-points of the study, i.e., emergence time and emergence hypertension. For emergence time, the study has 74% power to detect a difference between the propofol and fentanyl groups, 35% for fentanyl and isoflurane groups, and 13% for propofol and isoflurane groups ( = 5% level of significance). Similarly, for emergence hypertension the power of the study to detect a difference between propofol and fentanyl groups is 19%, 40% for propofol and isoflurane groups, and 86% between fentanyl and isoflurane groups ( = 5% level of significance). The findings suggest that the study has sufficient power to detect differences between propofol and fentanyl groups for emergence time, and between fentanyl and isoflurane groups for emergence hypertension.

We have conducted a trial to identify a technique for early awakening after craniotomy and in limiting emergence hypertension in patients with supratentorial tumors. We found that the use of low-dose fentanyl during craniotomy closure has clear advantages over propofol and isoflurane for optimal awakening and in limiting emergence hypertension. The presence of a significant midline shift in the preoperative cerebral imaging scans was identified as a risk factor for emergence hypertension.

ACKNOWLEDGMENTS

We are grateful to the Senior Residents of the Department of Neuroanesthesiology and Neurosurgery for their help during the course of this study. Our heartfelt thanks to the nursing staff of Neurosurgical Intensive Care Unit for their participation in this study. Mr. Alok Kumar Dwivedi deserves special thanks for statistical assistance.

Footnotes

Accepted for publication May 1, 2008.

Address reprint requests to Dr. Hemant Bhagat, Room No 709A, Department of Neuroanesthesiology, CN Centre, AIIMS, New Delhi 110029, India. Address e-mail to drhemantbhagat{at}rediffmail.com.

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bhagat, H. Articles by Pandia, M. P. Search for Related Content PubMed PubMed Citation Articles by Bhagat, H. Articles by Pandia, M. P. Related Collections Neuroanesthesia Anesthetic Techniques