Intraoperative awakening for early recognition of possible neurologic sequelae during Harrington-rod spinal fusion

A preliminary study of volatile agents or total intravenous anesthesia for neurophysiological monitoring during posterior spinal fusion in adolescents with idiopathic scoliosis

STUDY DESIGN

A prospective randomized controlled trial.

OBJECTIVE

The purpose of this study was to prospectively compare the efficacy of neurophysiological monitoring during general anesthesia with either a total intravenous technique or with the volatile anesthetic agent, desflurane.

SUMMARY OF BACKGROUND DATA

A total intravenous anesthetic technique is generally chosen when neurophysiological monitoring is used as it has been shown to facilitate such monitoring. Despite this, with prolonged infusions of propofol, prolonged awakening times may be seen, which may impact the time required for postoperative neurological assessment or more importantly result in significant delays, should a wake-up test become necessary. To date, there are no prospective trials comparing intravenous techniques with a volatile agent-based anesthetic technique and its effects on neurophysiological monitoring.

METHODS

This prospective study compares somatosensory evoked potential and motor evoked potential monitoring during posterior spinal fusion in 30 adolescents. The patients were randomized to receive a total intravenous technique with propofol-remifentanil or a volatile agent-based technique with desflurane-remifentanil.

RESULTS

The groups were similar with regard to age, weight, height, body mass index, Cobb angle, and distribution of Lenke classifications. No differences were noted in anesthesia time, surgery time, intraoperative fluids, or estimated blood loss between the 2 groups. Time to eye opening, time to following commands, and time to tracheal extubation were shorter in the volatile anesthesia group than the total intravenous anesthesia group. No clinically significant difference was noted in the amplitude or latency of somatosensory evoked potential monitoring. Although statistically significantly greater voltage amplitude was required to generate a motor evoked potential, the voltage amount was within a clinically acceptable range.

CONCLUSION

Our data demonstrate that a volatile agent-based anesthetic regimen is feasible even during neurophysiological monitoring. Advantages include a more rapid awakening and the feasibility of a rapid wake-up test (<5 min) in the event that irreversible changes in neurophysiological monitoring are noted.

LEVEL OF EVIDENCE

2.

Effect of the intraoperative wake-up test in sevoflurane-sufentanil combined anesthesia during adolescent idiopathic scoliosis surgery: a randomized study

STUDY OBJECTIVE

To investigate the effect of the intraoperative wake-up test on sevoflurane-sufentanil anesthesia for adolescent idiopathic scoliosis (AIS) surgery.

DESIGN

Randomized, double-blind, parallel trial.

SETTING

Operating room.

PATIENTS

30 ASA physical status 1 patients, aged 13 to 20 years, scheduled for AIS surgery.

INTERVENTIONS

Patients were randomized to two groups: Group W patients received sevoflurane-sufentanil combined anesthesia and underwent the intraoperative wake-up test; Group NW received sevoflurane-sufentanil combined anesthesia without the wake-up test. Anesthesia was induced with an intravenous (IV) injection of midazolam, propofol, and sufentanil and maintained with sevoflurane inhalation, a target-controlled infusion (TCI) of sufentanil, and IV infusion of cisatracurium besylate.

MEASUREMENTS

The primary outcome was postoperative delirium. Secondary outcomes were duration of surgery, duration of anesthesia, intraoperative blood loss and transfusion, exposure of drugs administered, time to eye opening, extubation, and consciousness.

MAIN RESULTS

Postoperative delirium occurred in one patient from each group (P > 0.05). There were no significant differences between the two groups in duration of surgery (322 ± 65 min vs 336 ± 72 min), duration of anesthesia (356 ± 76 min vs 368 ± 81 min), intraoperative blood loss (1847 ± 423 mL vs 1901 ± 451 mL) and transfusion (1663 ± 398 mL vs 1649 ± 382 mL), average exposure of drugs (72 ± 13 mg vs 75 ± 15 mg for propofol, 116 ± 28 μg vs 109 ± 25 μg for sufentanil, and 22 ± 5 vs 23 ± 4 mg for cisatracurium), time to eye opening (4.7 ± 1.5 min vs 4.8 ± 1.4 min), extubation (7.5 ± 2.0 min vs 7.3 ± 2.2 min), and consciousness (8.9 ± 1.8 min vs 9.1 ± 2.1 min) (all P > 0.05).

CONCLUSIONS

Sevoflurane-sufentanil combined anesthesia provides hemodynamic stability and rapid recovery from AIS surgery. There is no correlation between the intraoperative wake-up test and postoperative delirium after sevoflurane-sufentanil combined anesthesia.

Effects of dexmedetomidine on propofol and remifentanil infusion rates during total intravenous anesthesia for spine surgery in adolescents

INTRODUCTION

Total intravenous anesthesia with propofol and a synthetic opioid is a frequently chosen anesthetic technique for posterior spinal fusion. Despite its utility, adverse effects may occur with high or prolonged propofol dosing regimens including delayed awakening. The current study investigated the propofol-sparing effects of the concomitant administration of the alpha(2)-adrenergic agonist, dexmedetomidine, during spinal fusion surgery in adolescents.

METHODS

The surgical database of the department of orthopedic surgery was searched and patients (12-21 years of age) were identified who had undergone spinal fusion for either idiopathic or neuromuscular scoliosis during the past 24 months. Patients were assigned to two groups. Group 1 included patients anesthetized with propofol and remifentanil and group 2 included patients anesthetized with dexmedetomidine, propofol, and remifentanil. In the latter group, dexmedetomidine was administered as a continuous infusion of 0.5 microg.kg(-1).h(-1) started after the induction of anesthesia without a loading dose. Propofol was adjusted to maintain the bispectral index (BIS) number at 40-50 and remifentanil was adjusted to maintain the mean arterial pressure (MAP) at 50-65 mmHg. Labetolol or hydralazine was used if the MAP could not be maintained at 50-65 mmHg with remifentanil up to a maximum dose of 0.6 microg/kg/min. Statistical analysis included a nonpaired t-test for parametric data (age, weight, remifentanil/propofol infusion requirements, and heart rate/blood pressure values). A nonparametric statistical analysis (Dunn) was used to compare BIS numbers. Parametric data are presented as the mean +/- SD while nonparametric data are presented as the median and the 95th percentile confidence intervals.

RESULTS

Twelve patients received propofol-remifentanil-dexmedetomidine and 24 received propofol-remifentanil. There were no differences in the demographic data, BIS numbers or hemodynamic parameters between the two groups. There was a reduction in the propofol infusion requirements in patients who also received dexmedetomidine (71 +/- 11 microg.kg(-1).min(-1)) compared with those receiving only propofol-remifentanil (101 +/- 33 microg.kg(-1).min(-1), P = 0.0045). No difference was noted in the remifentanil infusion requirements or the use of supplemental agents (hydralazine and labetolol) to maintain controlled hypotension.

CONCLUSION

The concomitant use of dexmedetomidine in patients undergoing spinal fusion reduces propofol infusion requirements when compared with those patients receiving only propofol and remifentanil.

Effects of dexmedetomidine on intraoperative motor and somatosensory evoked potential monitoring during spinal surgery in adolescents

BACKGROUND

Dexmedetomidine may be a useful agent as an adjunct to an opioid-propofol total intravenous anesthesia (TIVA) technique during posterior spinal fusion (PSF) surgery. There are limited data regarding its effects on somatosensory (SSEPs) and motor evoked potentials (MEPs).

METHODS

The data presented represent a retrospective review of prospectively collected quality assurance data. When the decision was made to incorporate dexmedetomidine into the anesthetic regimen for intraoperative care of patients undergoing PSF, a prospective evaluation of its effects on SSEPs and MEPs was undertaken. SSEPs and MEPs were measured before and after the administration of dexmedetomidine in a cohort of pediatric patients undergoing PSF. Dexmedetomidine (1 microg x kg(-1) over 20 min followed by an infusion of 0.5 microg x kg(-1) x h(-1)) was administered at the completion of the surgical procedure, but prior to wound closure as an adjunct to TIVA which included propofol and remifentanil, adjusted to maintain a constant depth of anesthesia as measured by a BIS of 45-60.

RESULTS

The cohort for the study included nine patients, ranging in age from 12 to 17 years, anesthetized with remifentanil and propofol. In the first patient, dexmedetomidine was administered in conjunction with propofol at 110 microg x kg(-1) x min(-1) which resulted in a decrease in the bispectral index from 58 to 31. Although no significant effect was noted on the SSEPs (amplitude or latency) or the MEP duration, there was a decrease in the MEP amplitude. The protocol was modified so that the propofol infusion was incrementally decreased during the dexmedetomidine infusion to achieve the same depth of anesthesia. In the remaining eight patients, the bispectral index was 52 +/- 6 at the start of the dexmedetomidine loading dose and 49 +/- 4 at its completion (P = NS). There was no statistically significant difference in the MEPs and SSEPs obtained before and at completion of the dexmedetomidine loading dose.

CONCLUSION

Using the above-mentioned protocol, dexmedetomidine can be used as a component of TIVA during PSF without affecting neurophysiological monitoring.

Propofol–alfentanil vs propofol–remifentanil for posterior spinal fusion including wake-up test

BACKGROUND

Wake-up test can be used during posterior spinal fusion (PSF) to ensure that spinal function remains intact. This study aims at assessing the characteristics of the wake-up test during propofol-alfentanil (PA) vs propofol-remifentanil (PR) infusions for PSF surgery.

METHODS

Sixty patients with scoliosis and candidates for PSF surgery were randomly allocated in either alfentanil (PA) or remifentanil (PR) group. After an i.v. bolus of alfentanil 30 microg kg(-1) in the PA group or remifentanil 1 microg kg(-1) in the PR group, anaesthesia was induced with thiopental and atracurium. During maintenance, opioid infusion consisted of alfentanil 1 microg kg(-1) min(-1) or remifentanil 0.2 microg kg(-1) min(-1), in the PA group and the PR group, respectively. All patients received propofol 50 microg kg(-1) min(-1). Atracurium was given to maintain the required surgical relaxation. At the surgeon's request, all infusions were discontinued. Patients were asked to move their hands and feet. Time from anaesthetic discontinuation to spontaneous ventilation (T(1)), and from then until movement of the hands and feet (T(2)), and its quality were recorded.

RESULTS

The average T(1) and T(2) were significantly shorter in the PR group [3.6 (2.5) and 4.1 (2) min] than the PA group [6.1 (4) and 7.5 (4.5) min]. Quality of wake-up test, however, did not show significant difference between the two groups studied.

CONCLUSION

Wake-up test can be conducted faster with remifentanil compared with alfentanil infusion during PSF surgery.

Desflurane accelerates patient response during the wake-up test for scoliosis surgery

PURPOSE

To evaluate if desflurane possesses a shorter wake-up onset time and less incidence of recall than fentanyl-based anesthesia.

METHODS

Forty ASA class I-II adolescents, were enrolled into either a desflurane (DES) group, or a fentanyl (FEN) group for scoliosis surgery. Bispectral index (BIS) was monitored continuously in all patients throughout the procedure; the relationship between the wake-up time and BIS value was evaluated.

RESULTS

Patients in the DES group had a significantly shorter wake-up onset than patients in the FEN group (4.1 +/- 0.6 vs 8.9 +/- 2.1 min, P < 0.01). No recall occurred during the wake-up test in the DES group, while five patients had recall in the FEN group, including two patients who recalled a given colour. Extubation time was significantly shorter in the DES group than in the FEN group (7.2 +/- 0.6 vs 16 +/- 11.9 min, P < 0.01). BIS values were significantly higher in the FEN group than in the DES group during anesthesia. (62 +/- 4.5 vs 42 +/- 5.3, P < 0.05) BIS after the wake-up test was similar in both groups (90 +/- 2.9 vs 93.8 +/- 2.5). There was a latency period (3.3 +/- 1.2 min) between the maximal BIS value and wake-up time in the FEN group but not in the DES group.

CONCLUSIONS

DES provides a significantly shorter onset time during the wake-up test and a rapid emergence after scoliosis surgery. BIS monitoring during the wake-up test was more informative when anesthesia was maintained with DES compared to FEN infusion.

The bispectral index and explicit recall during the intraoperative wake-up test for scoliosis surgery

In this prospective study, we evaluated the bispectral index (BIS) and postoperative recall during the intraoperative wake-up examination in 34 children and adolescents undergoing scoliosis surgery. Each anesthesiologist was blinded to BIS values throughout surgery and the wake-up test. The BIS, mean arterial blood pressure, and heart rate were compared at: before starting the wake-up test, patient movement to command, and after the patient was reanesthetized. The anesthetic technique for Group 1 was small-dose isoflurane, nitrous oxide, fentanyl, and midazolam and for Group 2 was nitrous oxide, fentanyl, and midazolam. Controlled hypotension was used for all cases. At patient movement to command, the patients were told a specific color to remember (teal) and on the second postoperative day were interviewed for explicit recall of the color and other intraoperative events. A total of 37 wake-up tests were performed in 34 patients. There was a significant increase in both groups of BIS (P < 0.001), mean arterial blood pressure (P < 0.001), and heart rate (P < 0.01) at the time of purposeful patient movement followed by a significant decline in BIS after reintroduction of anesthesia (P < 0.01). No patient recalled intraoperative pain, one patient recalled the wake-up test but not the color, and five patients recalled the specified color. We conclude that BIS may be a useful clinical monitor for predicting patient movement to command during the intraoperative wake-up test, particularly when controlled hypotension is used and hemodynamic responses to emergence of anesthesia are blunted.

IMPLICATIONS

The relationship between bispectral index (BIS) and purposeful intraoperative patient movement is consistent with previous BIS utility studies. We conclude that BIS may be a useful clinical monitor for predicting patient movement to command during the intraoperative wake-up test, particularly when controlled hypotension is used and hemodynamic responses to emergence of anesthesia are blunted.

Neuroanesthesia. Innovative techniques and monitoring

Advances in neuromonitoring have provided insights into neurologic function during anesthesia. Despite the limitations and necessary caution when using intraoperative monitors to interpret neural function, these technologies have been definite steps in the right direction for assessing neural integrity and level of consciousness during anesthesia. The techniques discussed minimize the adverse sequelae of a variety of neurosurgical and orthopedic procedures, reducing the morbidity rates/risks in the perioperative period. Furthermore, it is likely that such monitoring will become a standard of care, similar to other monitoring standards such as pulse oximetry and capnography. Accurate and reliable monitoring is essential, and on-going large prospective studies comparing the processed EEG or evoked potential with definable end points in both adult and pediatric populations will be necessary. The use of monitoring, such as the BIS, may improve cost efficiency by reducing the total amount of drug used to maintain anesthesia, as well as enhance recovery. A danger in this process, however, is the potential for public opinion, outside regulatory bodies, or medico-legal implications to drive change and enforce standards of care before appropriate data are available.

Intermittent distracting rod for correction of high neurologic risk congenital scoliosis

STUDY DESIGN

Report of three cases of severe congenital scoliosis corrected by a new device.

OBJECTIVES

To show a new, safe alternative for treatment to achieve and maintain correction of the most severe spinal deformity.

SUMMARY OF BACKGROUND DATA

Because of neurologic risk, severe congenital scoliosis is usually not instrumented. Gradual correction seems to be safer for the spinal cord and to produce more efficient results because of the viscoelastic properties of the spine.

METHODS

A new device was used in three patients with congenital scoliosis. This device is placed by a posterior approach and permits correction of the scoliosis by slow, intermittent distraction. The gear of the elongation mechanism is activated by an extender placed subcutaneously. The correction takes place in the conscious patient, under rigorous neurologic control.

RESULTS

At the end of the distraction procedure, corrections of the scolioses in the three patients were from 118 degrees to 45 degrees, 104 degrees to 47 degrees, and 137 degrees to 71 degrees, respectively

CONCLUSIONS

The new device has proved useful for correcting, efficiently and without neurologic damage, severe scoliosis in three patients, and may be helpful in those curves with high neurologic risk.

Flumazenil facilitates intraoperative arousal during scoliosis surgery: a randomized, double-blind, placebo-controlled study

Intraoperative arousal was evaluated in 24 patients (median age 16.5 years), undergoing spondylodesis with Cotrel-Dubousset or Harrington-Luque instrumentation. Flumazenil and placebo groups of 12 patients each were similar with respect to age, body weight, dosage of anaesthetic drugs and surgery times. Premedication consisted of diazepam 0.2-0.3 mg kg-1 orally. Anaesthesia was induced with thiopentone 5-7 mg kg-1, and maintained with 66% nitrous oxide in oxygen, and repeated doses of fentanyl, midazolam and atracurium. After placement and fixation of the metal rods, N2O was switched off, and either flumazenil or placebo was given in refracted doses until the patient responded to command. Intraoperative motor response times (medians with ranges), defined as the time from the injection of the first dose until the patient responded to command, were 2.5 min (1.0-5.2 min) after flumazenil, and 8.0 min (1.7-28.5 min) after placebo (P = 0.02). Five patients in the placebo group did not wake up within 10 min and received naloxone. The quality of awakening was similar in both groups. Two patients (one in each group) woke up violently and needed physical restraint. Postoperatively, motor responses were assessed after 12.0 min (5-42 min) in the flumazenil group, and after 15.2 min (4-40 min) in the placebo group (NS). Recovery from anaesthesia took 27.5 min (7-415 min) in the flumazenil group, and 25.0 min (8-160 min) in the placebo group (NS). One patient given flumazenil and one patient given placebo remembered moving their feet, but neither of them could recall anything unpleasant.(ABSTRACT TRUNCATED AT 250 WORDS)

[Flumazenil and peroperative awakening in surgery of scoliosis]

Motor and sensory function must be assessed during surgery of scoliosis so as to avoid possible damage to the spinal cord. The intraoperative awakening by a specific benzodiazepine antagonist, flumazenil, was studied prospectively in 20 patients (mean age 17 years) undergoing surgery for severe scoliosis. Premedication consisted in 0.02 mg.kg-1 atropine and 0.15 mg.kg-1 midazolam. Anaesthesia was induced with a mean dose of 0.42 +/- 0.1 mg.kg-1 midazolam, 1.6 +/- 0.6 micrograms.kg-1 fentanyl and 0.1 mg.kg-1 pancuronium. Maintenance was obtained with a continuous infusion of 0.22 +/- 0.1 mg.kg-1.h-1 midazolam, 66% nitrous oxide in oxygen, and fentanyl (1.6 +/- 0.5 micrograms.kg-1.h-1). Nitrous oxide and midazolam were respectively stopped 10 and 1 min before giving the antagonist (5 micrograms.kg-1 flumazenil) if required (17 out of the 20 patients). Eye opening occurred a mean 42 +/- 32 s after giving the antagonist. At this time, there was a significant increase in mean arterial blood pressure (+ 11 mmHg) and heart rate (+ 7 b.min-1). Thiopentone, 66% nitrous oxide in oxygen and 0.5% halothane were given to re-induce and maintain anaesthesia for completion of the procedure. The day following surgery, 19 patients were unable to remember the period of intraoperative awakening. One patient, although remembering the episode, did not experience any pain or any other disagreement in relation to it. Two patients were given a second dose of flumazenil at extubation so as to improve the quality of their recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

The 'wake-up test'. A new approach using drug infusions

A case is presented in which there was a need for a 'wake-up test'. A technique is described, employing alfentanil and vecuronium given by infusion, and the problems of anaesthetic management are discussed.

Deliberate hypotension for spinal fusion: prospective randomized study with evoked potential monitoring

Twenty-four patients requiring spinal fusion with Harrington rod instrumentation were studied prospectively to determine the effects of moderate hypotension on blood loss, operating conditions, operating time and spinal cord function. Hypotension reduced blood loss and improved operating conditions but did not shorten operating time. Five patients had alterations in somatosensory cortical evoked potentials after straightening of the spine that prompted us to reverse hypotension (when present) and haemodilution, and then to do wake-up tests. All wake-up tests were normal and all evoked potential alterations resolved during operation. Hypotension seems unlikely to increase the risk of neurological damage if spinal cord function is monitored. Our findings suggest that patients subjected to spinal fusion need not be awakened during operation for testing of cord function provided somatosensory evoked potentials are monitored and remain stable.

Intra-operative awakening during scoliosis surgery

A method of intra-operative awakening which allows assessment of spinal cord function during Harrington rod spinal fusion for scoliosis is described. The anaesthetic technique is based on a standard muscle relaxant, N2O anaesthetic sequence supplemented with intravenous morphine 0.1 mg/kg at the commencement of surgery and 0.2 mg/kg intramuscular premedication. This relatively large total dose of morphine may reduce intra-operative awareness, and may also provide substantial pain relief during the initial 24 h postoperative period. It has been used successfully in 20 patients aged between 6 and 16 yr. Five patients remembered being woken, but did not regard it as unpleasant. In one patient, this technique allowed intra-operative detection and correction of impaired motor function of the legs.

Awareness, muscle relaxants and balanced anaesthesia

The incidence of awareness during insufficient anaesthesia is reported to be one per cent. It is usually due to the use of muscle relaxants, a balanced technique and the lightest possible depth of anaesthesia. Increased incidences were noted in open-heart surgery, during intubation-endoscopy procedures and in caesarean delivery patients. Experiences of awareness are disturbing to patients, who are usually benefited by a sympathetic and forthright explanation of the event. Fourteen representative cases of the problem are reported. Since no adequate sign or test exists for detection of awareness during very light anaesthesia or with associated paralysis, more meticulous attention is required in using relaxants or the balanced technique. Greater anaesthetic supplementation and reduction in the use of relaxants are recommended to halt the recurrence of this most serious anaesthetic problem.