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Abstract #27317 Published in IGR 12-4
The changes in visual-evoked potentials and intraocular pressure during prone spine surgery
Hasuwa K; Segawa Y; Kawaguchi M; Kumano H; Nishiwada MJournal of Neurosurgical-Anesthesiology 2010; 22: 421
Introduction: Postoperative ophthalmological complication is a rare, butdevastating complication after spine surgery. Prone positioning duringspine surgery is considered one of the risk factors for postoperativeophthalmological complication, because it increases traocular pressure(IOP), which may decrease perfusion pressure to the optic nerve. Visualevokedpotentials (VEP(s)) can be applicable to assess functional integrityof the optic pathways during surgery. However, the data regarding theVEP monitoring during spine surgery is limited. The present study wasconducted to investigate the changes of VEPs and IOP in patientsundergoing relatively short interval of spine surgery under proneposition. Methods: After institutional approval and written informed consent wereobtained, 10 patients (ASA11=42) undergoing spine surgery were enrolledin the study. None had preoperative glaucoma. Anesthesia wasmaintained with propofol, fentanyl, and rocuronium. For VEPmonitoring, the light-stimulating device, which consists of 9 white LED(s)embedded in a soft silicone disc, was placed on left eyelid. The VEPelectrodes were placed at Oz (international 10 to 20 methods) and at theA1 and A2 (reference). A signal processor (MEB2216, Neuropack,Nihonkoden) was used to record the VEP. For VEP ssment(amplitudes and latency), the largest positive peak that appeared120 msec after stimulus onset was used. IOP was measured in right eyeusing the Tonopen handheld tonometer (Tonopen XL, Reichert). VEP(s)and IOP(s) were recorded at the following 4 points; 15 minutes (T1;control), 60 minutes (T2), and 120 minutes (T3) after prone positioning,and before the return to supine position (T4). Physiological variablesincluding mean arterial pressure, heart rate, oxygen saturation, EtCO(2)and body temperature were also recorded at the same time points.Statistical analysis was performed using ANOVA with repeatedmeasures and Fisher PLSD post hoc test. Result: Physiological variables remained unchanged during the studyperiod. There were no significant changes in amplitude and latency of VEPs (amplitude, 3.2 (plus or minus) 1.7 mcV at T1, 3.3 (plus or minus) 1.6 mcV at T4; latency120 (plus or minus) 16ms at T1, 124 (plus or minus) 1 9ms at T4). IOP values significantlyincreased during the study period (24.3 (plus or minus) 5.0mm Hg at T1, 6.4 (plus or minus) 6.9mm Hg at T4, P < 0.0001). Interval for T4 after prone positioningwas 219 (plus or minus) 77 minutes.Conclusions: The results in the present study indicated that VEPremained unchanged, while a significant increase in IOP was observed,in patients undergoing relatively short interval of spine surgery underprone position. Further study would be required in patients undergoinglonger interval of spine surgery.
K. Hasuwa. Tenri Hospital, Japan.
Classification:
6.7 Electro-ophthalmodiagnosis (Part of: 6 Clinical examination methods)
6.1.3 Factors affecting IOP (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)
9.4.15 Glaucoma in relation to systemic disease (Part of: 9 Clinical forms of glaucomas > 9.4 Glaucomas associated with other ocular and systemic disorders)
