Selective cerebral perfusion at 28 degrees C--is the spinal cord safe?
OBJECTIVE
To shorten cooling/rewarming associated with hypothermic neuroprotection strategies during complex aortic arch surgery, selective cerebral perfusion (SCP) at 28 degrees C has recently been advocated, although its safe limits - especially with regard to the ischaemic tolerance of the spinal cord - have not been systematically examined.


METHODS
Twenty juvenile Yorkshire pigs (30.3+/-2.8kg) were randomly allocated to undergo circulatory arrest and SCP at 28 degrees C for 90 min (group A; N=12) or 120 min (group B; N=8) at 50 mmHg using alpha-stat pH management. Spinal cord blood flow (SCBF) was assessed using fluorescent microspheres at baseline (prior to SCP); at 5 and 80 min during SCP, and at 1, 5 and 48 h after cardiopulmonary bypass (CPB). A modified Tarlov score was used to evaluate neurobehavioural recovery in all survivors blindly from videotapes for 5 days postoperatively. Histological ischaemic spinal cord injury was scored after sacrifice.


RESULTS
All pigs could be weaned from CPB and ventilation, but seven pigs (58%) in group A and five (63%) in group B developed multi-organ failure and died within 24h. SCBF diminished immediately after initiation of SCP and was absent throughout SCP in all segments below T8/9, recovering to baseline 1h after SCP at all cord levels. All survivors suffered moderate-to-severe histological lumbar spinal cord damage, more severe in group B (p< or =0.049). Three of five group A pigs recovered normal function, but two suffered paraparesis. Group B survivors had a worse neurologic outcome (p<0.0001): all suffered paraplegia (one immediate, and two on day 2, after initial recovery).


CONCLUSIONS
SCP provides insufficient SCBF below T8/9 to sustain cord viability. At 28 degrees C, the ischaemic tolerance of the cord may be exceeded enough by 90 min to impair function; by 120 min, SCP at 28 degrees C invariably results in paraplegia.
Etz
Christian D
CD
Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, One Gustave L. Levy Place, PO Box 1028, New York, NY 10029, USA. christian.etz@mountsinai.org
Luehr
Maximilian
M
Kari
Fabian A
FA
Lin
Hung Mo
HM
Kleinman
George
G
Zoli
Stefano
S
Plestis
Konstadinos A
KA
Griepp
Randall B
RB
D000818:Animals; D001013:Aorta, Thoracic / Q000601:surgery*; D001831:Body Temperature; D002315:Cardiopulmonary Bypass / Q000379:methods; D002560:Cerebrovascular Circulation; D005260:Female; D006324:Heart Arrest, Induced / Q000009:adverse effects / Q000379:methods; D007036:Hypothermia, Induced / Q000009:adverse effects / Q000379:methods*; D010264:Paraplegia / Q000209:etiology; D010477:Perfusion / Q000379:methods; D011183:Postoperative Complications / Q000473:pathology / Q000517:prevention & control*; D011897:Random Allocation; D012039:Regional Blood Flow; D012720:Severity of Illness Index; D013116:Spinal Cord / Q000098:blood supply; D020760:Spinal Cord Ischemia / Q000473:pathology / Q000517:prevention & control*; D034421:Sus scrofa