We compared cerebrospinal fluid (CSF) drainage (Group D; n = 8) to
neuroanesthesia adjunct
therapy (
hyperventilation and
mannitol administration; Group N; n = 8) for the prevention of
paraplegia using a canine model of descending thoracic aortic cross-clamping (AXC; 2.5 mm distal to the left subclavian artery for 30 min). We expected no difference in neurologic outcome between groups. After surgical preparation and a 30-min stabilization period, dogs in Group D had CSF drained prior to application of the AXC. During the period of AXC, CSF was allowed to drain freely in an attempt to have cerebrospinal fluid pressure (CSFP) no greater than central venous pressure (CVP). Dogs in Group N were hyperventilated (PaCO2 28-32 mm Hg) and received 2 g/kg of
mannitol prior to AXC and then 1 g.kg-1.hr-1 during clamping. Systemic hemodynamics, CSFP, and arterial blood
gases were measured at 1) baseline, 2) 2 min after AXC, 3) 20 min after AXC, 4) 5 min after AXC release, and 5) 30 min after
resuscitation. With release of the AXC, PaCO2 was not controlled in Group D; in Group N the minute ventilation was further increased to maintain PaCO2 constant. At precisely 24 h after AXC, the animals were assessed for incidence and severity of
paraplegia, using the Tarlov score, by an observer unaware of the experimental protocol. The animals were then killed, and the entire spinal cord was removed for histologic assessment. Multiple sections of the lumbar spinal cord were processed and stained with
hematoxylin and
eosin, then examined by light microscopy for nonviable neurons in the anterior spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)