A new method of intrathecal PO2, PCO2, and pH measurements for continuous monitoring of spinal cord ischemia during thoracic aortic clamping in pigs.
BACKGROUND
Impaired spinal cord circulation during thoracic aortic clamping may result in paraplegia. Reliable and fast responding methods for intraoperative monitoring are needed to facilitate the evaluation of protective measures and efficiency of revascularization.


METHODS
In 11 pigs, a multiparameter PO2, PCO2, and pH sensor (Paratrend 7, Biomedical Sensors Ltd, United Kingdom) was introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenation during thoracic aortic cross-clamping (AXC) distal to the left subclavian artery. A laser-Doppler probe was inserted into the epidural space for simultaneous measurements of spinal cord flux. Registrations were made before and 30 minutes after clamping and 30 and 60 minutes after declamping. The same measuring points were used for systemic hemodynamic and metabolic data acquisition.


RESULTS
The mean CSF PO2 readings of 41 mm Hg (5.5 kPa) at baseline decreased within 3 minutes to 5 mm Hg (0.7 kPa) during AXC (P < .01). Spinal cord flux measurement responded immediately in the same way to AXC. Both methods indicated normalization of circulation during declamping. Significant (P < .01) changes were also observed in the CSF metabolic parameters PCO2 and pH.


CONCLUSIONS
In this experimental model of spinal ischemia by AXC, online monitoring of intrathecal PO2, PCO2, and pH showed significant changes and correlated well with epidural laser-Doppler flowmetry (P < .01).
Christiansson
L
L
Department of Anesthesiology, University Hospital, Uppsala, Sweden.
Hellberg
A
A
Koga
I
I
Thelin
S
S
Bergqvist
D
D
Wiklund
L
L
Karacagil
S
S
D000818:Animals; D001013:Aorta, Thoracic; D002245:Carbon Dioxide / Q000032:analysis*; D002555:Cerebrospinal Fluid / Q000378:metabolism*; D004824:Epidural Space; D006863:Hydrogen-Ion Concentration; D007511:Ischemia / Q000175:diagnosis*; D017078:Laser-Doppler Flowmetry; D010100:Oxygen / Q000032:analysis*; D013116:Spinal Cord / Q000098:blood supply*; D013552:Swine
D002245:Carbon Dioxide; D010100:Oxygen