The aim of this study was to assess the effect of rapid or delayed surgical evacuation on the physiological consequence and
brain edema formation in a rat model of
acute subdural hematoma (SDH) coupled with either
diffuse brain injury (
DBI) or
hypoxemia. The SDH was made by an autologous blood injection, while
DBI was induced using the impact acceleration model (mild, 450 g/1 m; severe, 450 g/2 m). Physiological parameters measured included intracranial pressure (ICP), mean arterial blood pressure (MABP), cerebral blood flow (CBF), and brain tissue water content. At 1 h (rapid evacuation) or 4 h (delayed evacuation) after the SDH induction, surgical evacuation following a
craniotomy was performed using saline irrigation and
forceps. The study consisted of three different series, including 400 microL of SDH alone (Series 1), SDH400 + mild
DBI (Series 2), and SDH300 + severe
DBI + 20 min
hypoxemia (Series 3). The
hypoxemia was added in Group 3 to produce a steadily increasing ICP. In Series 1 and 2, all rats were randomized into the three following groups: non-, rapid, and delayed evacuation; Series 3 had two groups: non- and rapid evacuation. In Series 1, the surgical evacuation showed no beneficial effects on the
brain edema formation assessed at 5 h post-injury. In Series 2, the rapid, but not delayed, evacuation significantly reduced both the increased ICP level and brain water content. The additional insult of
hypoxemia (Series 3) resulted in a progressive ICP elevation, persistently depressed CBF, and severe
brain swelling. Under this situation, the rapid evacuation exacerbated
brain edema. These results have clinical implications for the management of severe traumatic SDH, especially its operative indication and timing.