I-gel saves the day: Bradycardia and apnea in a patient undergoing burr hole and evacuation for a subdural hematoma under scalp block.

Awake craniotomy is generally performed in scalped block, although it is safe, but this procedure can sometimes produce severe hemodynamic disturbances. Here, we reported a case of 32-year-old male, who came for burr hole and during the craniotomy performed under scalped block developed bradycardia and became apneic as manifested by the absence of ETCO2 and no chest excursions. An I-gel was inserted rather than intubating the patient and the case was managed very well and which showed the importance of supraglottic airway devices in our day to day practice.

INTRODUCTION

Scalp nerve block is a commonly performed procedure for awake craniotomy. Though relatively safe, this procedure can sometimes produce severe hemodynamic disturbances.[1] Here, we have highlighted such a complication and its possible explanation.[2] I-gel is a supraglottic airway device of second generation. Due to normal tracheal intubation, there is increased pressor response resulting in an increase in heart rate, blood pressure, and finally increased intracranial pressure. However, the use of I-gel can result in minimum changes in these responses. Systemic and cerebral hemodynamic changes caused by extubation and emergence from anesthesia may endanger neurosurgical patients and increase the risk of postoperative intracranial hemorrhage and cerebral edema and may even result in the requirement of reoperation.[3]

CASE REPORT

A 30-year-old male patient reported to neurosurgery out-patient department with complaints of headache and altered behavior for the past 15 days, being brought by relatives. He had sustained a fall about 15 days ago, while intoxicated with alcohol. The patient had a Glasgow coma scale of E4 V4 M5 (13/15) and computed tomography scan showed a left parietal subdural hematoma (SDH) with midline shift. Routine investigations were done and were found to be within acceptable limits. Patient was posted for burr hole and evacuation of the SDH.

After an overnight fast and obtaining consent, patient was taken to the operating room. Patient was planned to be given a unilateral scalp block along with minimal sedation. Appropriate monitors, such as electrocardiography, noninvasive blood pressure, SpO2, and ETCO2 (tape under the O2 mask) were applied. A 20 gauge intravenous catheter was inserted and an infusion of 0.9% normal saline was started. Oxygen was supplement by a Hudson mask, 4 L/min. As the patient was not fully cooperative and oriented, we could not explain the procedure to him, despite our best intentions. In order to do the scalp block, we gave minimal sedation to the patient to make him more amenable, in the form of intravenous midazolam 0.5 mg followed by 50 μg of fentanyl. This calmed the patient and thereby allowing the team to give scalp block. Scalp block of the left side, was performed by an experienced operator with a 24 gauge needle and total 12 ml of local anesthetic were instilled (6 ml of 2% lignocaine with 1:200,000 adrenalin and 6 ml of 0.5% bupivacaine) at appropriate sites to cover the target nerves. Sufficient time was given to allow the block to be effective and after 10 min when pin-prick of the left hemi-scalp did not elicit any pain, the go ahead was given to the surgeons.

Care was taken to make sure that all the monitors were not disturbed during painting and draping of the scalp. A mayo stand was placed sufficiently above the head of the patient and this was draped as usual practice for neurosurgery cases. Before the timed incision for the burr hole, another bolus of 25 mcg of fentanyl was given to the patient in order to get an immobile patient, in view of his continued restlessness. Despite this, the patient was not still and hence 20 mg of propofol was also given, followed by another 20 mg. This made the patient still and the surgeon began the procedure. While the surgeon began drilling for the burr hole, it was noticed that there was sudden bradycardia and the heart rate fell to 35 bpm min before glycopyrrolate 0.2 mg was given. At the same time, the patient became apneic as manifested by the absence of ETCO2 and no chest excursions. As this occurred, we alerted the surgeon, who stopped the procedure and flooded the site with saline, considering the possibility of an air embolism. As the patient was apneic but maintaining saturation and now the heart rate was in the 80s, we had time and thought to insert a size 4 I-gel instead of intubating which would interfere with the surgical field. Reaching underneath the drapes and below the mayo stand, the oxygen mask was removed and the I-gel was inserted smoothly and connected to the breathing circuit. The ventilation was confirmed by the presence of ETCO2 and diaphragmatic movements. As the patient was throughout stable, the surgeon was given the go-ahead to restart the procedure. Anesthesia was maintained with isoflurane in oxygen and nitrous oxide mixture, titrated to depth of anesthesia. Patient began spontaneous breathing after 3–4 min later and was then assisted by the anesthesia resident. The burr hole was done and SDH evacuated, which took about 45 min. After applying the head bandage, all anesthetic agents were stopped and the patient was allowed to breathe on 100% oxygen till he woke up. When the patient woke up, the I-gel was removed after gentle suction. Patient was shifted to the postanesthesia care unit and monitored. There were further no issues and patient had a smooth postoperative period.

DISCUSSION

There is a single report of bradycardia following scalp block, which was due to trigeminocardiac reflex (TCR). However, this was within minutes of the block. In our case, the bradycardia occurred much later and cannot be attributed to TCR.[45] The other possible mechanism may be Vasovagal, which can be provoked during any sharp noxious stimuli or emotional stress.[4] However, there were no episodes of loss of consciousness and dizziness during these hemodynamic changes. Seizure episodes can also mimic these types of cardiovascular perturbations; however, there were no associated abnormal body movements.[6] It was felt that the boluses of fentanyl followed by boluses of propofol, produced the bradycardia, then apnea in a patient who had already been sedated by a benzodiazepine (cumulative effect). Both agents are known to produce bradycardia through different mechanisms. Fentanyl is thought to produce through sympatholytic mechanism, and is potentially dangerous when combined with vecuronium.[7] Propofol produces hypotension and bradycardia through its action on the cardiovascular system.

Taking the whole situation into account the whole team acted well, by giving glycopyrrolate instead of atropine, which causes too much undue tachycardia. Inserting an I-gel was a better idea than using a laryngeal mask airway, which has its problems or intubation which we thought to avoid for a short procedure.

Usually, the burr hole evacuation of SDHs, are carried out in elderly subgroup of patients. The procedure being short (<45 min) and the patient being an elderly person, local anesthesia along with monitored anesthesia care (MAC), and minimal sedation is usually preferred by both the anesthetist and surgeon. However, this is done at the cost of having an unsecured airway in an inaccessible area, which is taken up by the surgeon.

CONCLUSION

This case report shows that having a PLAN B, is a good thing. Although burr hole evacuation is a relatively short case and may be done in local anesthesia or MAC with or without regional anesthesia, it is done at the cost of the airway security. Because the head end is draped and inaccessible, the anesthetist is always in a predicament, and although we may get away with it many times, there will be days when we are in a fix. This did happen to us, but however we were prepared and smooth and timely insertion of I-gel managed to save the anesthesiologist, the patient, and our respect.