Anesthetic Management For Neurosurgery Using Intraoperative Magnetic Resonance Imaging

Neurosurgical techniques have made great advancement with the use of intraoperative magnetic resonance imaging (iMRI), but it made perioperative managements different according to the special environment and procedure of iMRI.This study was focus on observing special considerations and managements of anesthesia related to this kind of neurosurgery.Part I Special considerations to intraoperative magnetic resonance imaging for neurosurgeryObjective To observe the special considerations related to intraoperative magnetic resonance imaging (iMRI) for neurosurgery. Methods Clinical observation included two phases.PhaseⅠ,120 neurosurgery patients underwent MRI scanning in iMRI operation room(iMRI-OR) preoperatively, intraoperatively, and 13 patients underwent MRI scanning in diagnostic room(iMRI-DR) postoperatively were observed. patients finished MRI scanning and surgery with general anesthesia, and with the support of MRI-compatible machines. All patients received MRI safety screening preoperative and safety examination intraoperative, patients'basic information, results of MRI safety screening and examination, the cause for MRI, frequence for MRI and special issues related to scanning were recorded. PhaseⅡ12 neurosurgical adult patients with normal ECG received intracranial tumor resection via intraoperative high-field MRI scanning were observed, routine monitors were carried, blood pressure(BP), pulse rate (PR) and ECG waves (lead II) at different time points: before MRI scanner moved to operation room, scanner moved to patients(static MRI field), different MRI sequences T1, T2, Diffusion Tension Imaging(DTI) were recorded. Results Phase I, There were 39 patients with abnormal ECG and metallic foreign body in MRI safety screening, and 20 cases with wrong locations of objects and 3 cases with door unlocking in MRI safety eximination. The reasons for MRI were uncooperation of patients, changing in operation position, correctting neuronavigation, tumor residual and excluding complications. The total number of MRI was 230, including 217 times in iMRI-OR (13 times preoperatively,204 times intraoperatively) and 13 times in iMRI-DR postoperatively. There were 5 special issues related to MRI. PhaseⅡDuring MRI, BP and PR were stable. There were remarkably strong interferences on ECG in static MRI field, such as ECG baseline changing, ST-segment alterations, during T1, T2 sequences the interferences were enlarged and high frequency artifacts occurred, during DTI sequence, ECG was multiphasic, P and QRS waves were difficult to recognize, but all return to normal after scanner exit. Conclusions During iMRI the safety screening preoperative and safety examination intraoperative were important, and ECG waves were interfered extremely. It is necessary to set up strict rules of safety screening and examination, and use interference-free monitor parameters to guarantee patients'safety.Part II The influence of neurosurgery using intraoperative magnetic resonance imaging on anesthesia Objective To evaluate the influcences of neurosurgery using intraoperative magnetic resonance imaging on anesthesia. Methods 60 patients with glioma were observed. they were divided into two groups(30 in each), patients in iMRI group underwent craniotomy with intraoperative magnetic resonance imaging and functional neuro-navigation, patients in N group with functional neuro-navigation. patients' basic information, anesthesia duration, preparation time for surgery, duration of surgery, blood lose, fluid administration, the need for transfusion, preoperative and postoperative hemoglobin, body temperature postoperative, the dosage of muscle relaxant and incidents related to anesthesia were recorded. In group iMRI, informations of frequence for MRI, duration for MRI, MRI related time (from preparation of MRI to surgery restarting), time prolonged by MRI, body temperature during MRI and complete resection ratio of glioma were recorded. Results There were no significant differences of patients'basic information, anesthesia duration, blood lose, fluid administration, the need for transfusion, preoperative and postoperative hemoglobin, body temperature between two groups, but in iMRI group preparation time for surgery, duration of surgery were longer, the dosage of muscle relaxant was larger than that in N group, there was no incident related to anesthesia happened in both groups. In iMRI group, all patients underwent 57 MRI (average 1.9), duration for MRI was 29.24±10.10min, MRI related time was 43.83±10.23min, time prolonged by MRI was 92.63±28.31min, body temperature was significant higher at 2h after MRI than that at induction moment. Complete resection ratio of glioma was 83.3% by using iMRI。Conclusions The application of iMRI in neurosurgery was helpful for increasing complete resection ratio of glioma, but resulted in longer duration of surgery, other characters related to this kind of surgery were similar to traditional surgery. Besides the basic rules for neurosurgery anesthetic management, we should focus on anesthetic modulation of long duration surgery.Part III Anesthetic management during the stage of intraoperative magnetic resonance imaging for neurosurgeryObjective To investigate the anesthetic management during the stage of intraoperative magnetic resonance imaging (iMRI) for neurosuergery. Methods 25 patients received intracranial tumor resection via iMRI scanning and iMRI guiding system with general anesthesia. Patients were inducted with amnesia analgesia slow induction method, and anesthetized with sevoflurane(keep the end tidal concentration at 0.95%～1.05%), rocuronium was used to maintain muscle relaxation, anesthetic depth was maintained by adjusting the concentration of remifentanil (every time 0.02μg·kg-1·min-1 regulation after the primary concentration of 0.2μg·kg-1·min-1 at the beginning of the surgery) according to the fluctuation of mean arterial pressure(MAP), point of accommodation of MAP was-10%～+5% of baseline, and to maintain MAP with-20%～+10% of baseline, pulse rate(PR) less than 100bpm. Vasoactive agents were used as needed. The concentration of remifentanil, PR, MAP and temperature were recorded at different stages of surgery:during skull opening(skull drilling, after skull removing, dural opening), intracranial procedure(30min and 1h), MRI scanning (before MRI, performing MRI, after MRI, surgery restarting), dural closing.Results The concentration of remifentanil decreased at the stages of 1h in intracranial procedure, but was similar during the period of iMRI scanning compared with intracranial procedure. All patients'vital signs were stable during surgery. PR during MRI was higher than in the stage of 1h in intracranial procedure. There were no difference in temperature among each stage.Conclusions During iMRI scanning, thoμgh without the stimulation of surgery, the anesthetic depth was just similar to intracranial procedure. Whether it related to high noise or open wound surface needs more investigation.