Early Inflammatory Response in the Brain and Anesthesia Recovery Time Evaluation After Experimental Subarachnoid Hemorrhage

Abstract

The main objective was to evaluate, whether the subarachnoid hemorrhage (SAH)-associated early inflammatory response has focal or global character, i.e., whether areas distant to hematoma may be affected by an early inflammatory response. The second objective was to evaluate the association of anesthesia recovery time for basic reflexes/neurological functions with severity of SAH. SAH was induced in rats using an endovascular perforation model. Anesthesia recovery time was evaluated for pain reaction recovery time (spinal level), spontaneous ventilation recovery time (brain stem level), and consciousness recovery time (neocortical level). mRNA expressions of TNFα, IL-1β, IL-6, ICAM-1, and VCAM-1 in areas adjacent and distant to hematoma were evaluated between 2 and 8 h after SAH. Serum levels of TNFα, IL-1β, and IL-6 were assessed at 4 and 8 h after SAH. Anesthesia recovery time of all selected parameters was associated with severity of SAH. The consciousness recovery time test had the best predictive value, while the spontaneous ventilation recovery time test was able to bring information in the shortest time. The mRNA expressions of pro-inflammatory cytokines were significantly increased in severe SAH groups in both adjacent and distant areas. The inflammatory response in mild/moderate SAH groups was less strong, peaking at 4 h after SAH. Serum levels of pro-inflammatory cytokines were ambiguous. Anesthesia recovery time may be useful for bleeding severity prediction in the SAH model; however, further validation is needed. Severe subarachnoid hemorrhage is associated with the strong early inflammatory response, which has a global character, while mild subarachnoid hemorrhage is accompanied by a weaker inflammation.

Keywords: Anesthesia recovery time; Early brain injury; Inflammation; Subarachnoid hemorrhage.