Concerns while monitoring patients during awake craniotomy with intraoperative magnetic resonance imaging

摘要

Gandhe and Bhave suggested some importantconsiderations for awake craniotomy underintraoperative magnetic resonance imaging (iMRI).[1]We would like to add that capnography, the concomitantmonitoring of end.tidal carbon dioxide (EtCO2) andrespiratory rate (RR), is essential because directvisualisation of chest movement and immediate accessto the patient’s airway are restricted when an awakepatient is in the iMRI gantry.[2] While pulse oximetryis useful for monitoring oxygenation, desaturation lagssignificantly behind hypoventilation, especially whenpatients receive supplemental oxygen. Moreover,neurosurgical intervention may decrease the level ofconsciousness, which sometimes causes respiratorydeterioration.[3] A review of 356 consecutive awakecraniotomies at our institution revealed poorrecording of the intraoperative respiratory conditionof unsecured airway patients: RR was monitored inonly 30.2% of all iMRI sequences (through changes inEtCO2 level), whereas oxygen saturation was recordedin 95.9% of cases.[2] While the use of capnographyfor non.intubated patients is still uncommon,an absolute change from baseline of greater than10 mmHg or loss of EtCO2 waveform may indicatethat the patient is at risk of significant respiratorydepression.[4] All the respiratory arrests among ourpatients were detected based on gradually decreasingRR by capnography.[2] Careful patient observation isalso important; our unwrapped draping techniqueenhances patient visibility [Figure 1]. Compared withhigh magnetic field iMRI scanners, low magneticfields with a gap at the side of the scanner may reducethe frequency of transfer.related accidents and enablea quick response to a patient’s declining status.