| Abstract: |
Safety is the first priority in any spine surgery. The development of new onset postoperative neurological deficits needs to be reduced if at all feasible. Thus, the main aim of IONM is early detection and reversal of potential neurological injury before it became permenant neurological deficits .
Quick identification of impending spinal cord injury opens the window of opportunity to the surgeon and anesthesiologist to act before the injury becomes irreversible. Therefore , the monitoring of gross motor and sensory function in spine deformity surgery is extremely important, especially when correcting spine deformities in the pediatric population presenting with additional neurological risk: neglected rigid kyphoscoliosis, congenital spine anomalies, revision spine surgeries, marfanoid patients with lordoscoliosis, etc .
In our study thirty six patients are divided into two groups, each of 18 patients :
• Group T who received TIVA only including propofol , dexmedetomidine and fentanyl .
• Group M who received total intravenous anesthesia (TIVA) plus partial dose of rocuronium . Our primary aim was to detect the effect of rocuronium with this partial dose on neurophysiological monitoring which is very important to avoid any postoperative neurological insult but our secondery aim is to evaluate the effect of it’s usage on hemodynamics (heart rate and mean arterial pressure) , blood transfusion , surgeon satisfaction and depth of anesthesia by spectral edge frequency .
The following procedure was carried out :
All patients were premedicated with midazolam then transmitted to our operating room (OR) , standard monitoring was done including ECG, pulse oximetry , non-invasive blood pressure monitoring , temperature probe and capnography .Another wide bore cannula (18 gauge) was inserted then induction and maintenance of anesthesia was done for both groups by TIVA including propofol , dexmedetomidine and fentanyl.
For both groups (T and M) , Fentanyl (2–3 μg / kg) , propofol (2–3 mg /kg) , dexmedetomidine (1 μg / kg) over 20 minutes and xylocaine puff spray 10% were given to all patients . Then patients were maintained by: propofol infusion at 12 mg /kg/h for 10 min, then 10 mg / kg / h for next 10 min and continued at 8 mg/kg /h , dexmedetomidine (0.2-0.7 μg / kg / h) and fentanyl (1-2 μg/kg/hr). For group (M) only partial muscle blockade with rocuronium was given during induction with dose of (0.6 mg/kg) then maintenaned with (0.6 mg /kg /h) .
After ensuring adequate ventilation for both groups , endotracheal tube was inserted and secured then the patient was connected to mechanical ventilation (TV 5 ml/kg , RR 16 B/min , I:E ratio 1:2.5) , ventilator parametrs were adjusted to keep EtCO2 35-40 mmHg and vital parameters were recorded (HR , mean arterial blood pressure by non -invasive method , SpO2 , EtCO2 and urine output ) . Patient was turned to the prone position with it's precautions regarding rechecking of endotracheal tube , hemodynamics changes and pressure points . Adjustment of the infusion rate to achieve the desired clinical effect.
Neurophysiological monitoring mainly includes motor evoked potentials and somatosensory evoked potentials . We revealed that there is reduction in the amplitude of MEPs in group (M) than group (T) but without affection of monitoring . Regarding somatosensory evoked potential amplitude , there was no significant difference between the two groups . Regarding SSEPs latency , it was longer in group (M) than group (T) but without significant difference between them . Regarding Train of Four (TOF) at different follow-up periods, this study showed that TOF was significantly lower in group (M) compared to group (T) at different follow up times . Although using Rocuronium , and when TOF’s count was 2-3 , this didn’t affect our neurophysiological monitoring . So it is very safe to use muscle relaxant with specific dose with keeping neuromonitoring.
Depth of anesthesia by spectral edge frequency was significantly different between both groups as it was lower in group (M) rather than group T . Regarding hemodynamics (HR and MAP) , there was significant difference as they were lower in group (T) than group (M) , this maybe was due to the usage of higher doses of anesthetic drugs in group (T) to allow better depth of anesthesia . Regarding respiratory profile (Spo2) there was no significant difference between both groups.
Regarding need for blood transfusion , there was no significant difference between both groups despite blood loss was lower in group (M) . Regarding surgeon satisfaction , in group (M) the majority of surgeons showed excellent response (72.2%) but in group (T) the majority of them showed good response (66.7%).
Regarding recovery characteristics time to eye opening , time to follow commands and time to tracheal intubation were lower in group M specially after usage of sugammadex for reversal of rocuronium so no fear for delayed recovery from muscle relaxant or residual effect of continuous use of rocuronium .
In conclusion use of partial muscle relaxant is more favorable during adolescent idiopathic corrective surgery even with neurophysiologic monitoring as it doesn’t affect either MEPs or SSEPs.
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