ICP and MABP following traumatic subarachnoid hemorrhage in the rat

Traumatic subarachnoidal hemorrhage (t-SAH) is a common finding in head-injured patients occurring with a frequency of 39% according to data of the Traumatic Coma Data Bank. The present study is the first description of a t-SAH-model with particular emphasis on patterns of intracranial pressure (ICP) changes and mean arterial blood pressure (MABP) response. Diffuse brain injury was produced in intubated and ventilated adult Sprague-Dawley rats (N = 24) using a brass weight (500 gm) free falling from a predetermined height (1.5 m) on a steel disc glued to the skull of the rat. Before induction of the injury, heparin was administered intra-arterially (i.a.) and antagonised after injury by protamine. MABP-recordings and ICP-recordings were performed continuously. Histopathology was undertaken. Following injury MABP decreased from 138 +/- 14 mmHg to 89 +/- 22 mmHg. During 5 to 15 min ICP increased up to 89.4 +/- 50.4 mmHg, decreasing slowly within 60 min in surviving animals. The mortality rate was 41.6%. All brains showed a severe subarachnoid hemorrhage in the basal cisterns and cell-loss within the brainstem. Experimental t-SAH is possible. Following t-SAH there is a subacute increase of ICP due to the actual bleeding. The model may provide deeper understanding in the basic physiological patterns of t-SAH.