title: Brain tissue pressure measurement during sodium nitroprusside infusion.
abstract: The effect of acute 25% decrease in mean arterial pressure (MAP) produced by sodium nitroprusside (SNP) infusion on mean intracerebral and cerebral perfusion pressures was examined in 7 swine with intracranial hypertension. All animals were anesthetized (alpha-chloralose), paralyzed (pancuronium bromide), orotracheally intubated and mechanically ventilated to maintain normocapnia. An epidural balloon was incrementally inflated to produce the desired brain tissue pressure (BTP) which was measured by an intracerebral microtransducer implanted contralateral to the balloon. MAP was measured from the carotid artery; cerebral perfusion pressure (CPP) was calculated as: MAP - BTP. During mildly (14 +/- 1 (SE) mm Hg) or moderately (37 +/- 3 mm Hg) increased BTP, SNP infusion increased BTP (17 +/- 1 and 44 +/- 3 mm Hg, respectively) (p less than 0.05). During severely increased BTP (70 +/- 4 mm Hg), SNP decreased BTP (53 +/- 4 mm Hg, p less than 0.05). Despite this variable BTP, CCP consistently decreased during SNP infusion. BTP and supratentorial subarachnoid cerebrospinal fluid pressure correlated closely; however, the supratentorial subarachnoid pressure consistently underestimated BTP. These findings suggest that estimation of BTP obtained from subarachnoid screw-type devices may not accurately record the pressure within cerebral tissue and the SBNP should not be administered to patients with known or suspected intracranial hypertension unless an intracranial (either BTP or subarachnoid) pressure is being monitored.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005292:Ferricyanides / Q000494:pharmacology*; D007427:Intracranial Pressure / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology*; D011559:Pseudotumor Cerebri / Q000503:physiopathology; D013552:Swine
chemical_list: D005292:Ferricyanides; D009599:Nitroprusside