Neurol Med Chir (Tokyo) 46, 219¿225, 2006 Cardiopulmonary Hemodynamic Changes During Acute Subdural Hematoma Evacuation Tomonori TAMAKI,YojiNODE,YasuhiroYAMAMOTO*,andAkiraTERAMOTO Departments of Neurosurgery and *Critical Care Medicine and Emergency, Nippon Medical School, Tokyo Abstract The aim of this study was to clarify the mechanism of hemodynamic changes leading to intraoperative hypotension during evacuation of acute subdural hematoma. To our knowledge, little data is available about the mechanism of hemodynamic changes during surgical interventions to decrease intracranial pressure after severe head injury. The influence of preoperative hypotension on intraoperative hypotension was examined. Hemodynamic studies (pulmonary artery catheterization) were carried out in 15 patients before and after acute subdural hematoma evacuation. All patients were assessed for hemodynamic parameters, evacuated hematoma volume, and intracranial pressure measurements. Comparison between just before and after evacuation of the hematoma showed that the mean arterial pressure, pulmonary arterial pressure, systemic vascular resistance, pulmonary vascular resistance, central venous pressure, and pulmonary capillary wedge pressure all decreased after hematoma evacuation. However, the cardiac index was unchanged after hematoma evacuation. Mean arterial blood pressure is dependent on the cardiac index and vascular resistance, so the decrease in arterial blood pressure during hematoma evacuation was the result of a decline in vascular resistance. The influence of preoperative blood pressure on intraoperative hemodynamic changes was analyzed by dividing the patients into two groups, the preoperative hypotension group and preoperative non- hypotension group. The decrease in mean arterial blood pressure was more marked in the preoperative hypotension group than in the preoperative nonhypotension group. Intraoperative hypotension during evacuation of acute subdural hematoma is caused by a decrease in vascular resistance. Preoperative hypotension is a also risk factor for intraoperative hypotension. Key words: severe head injury, pulmonary artery catheter, systemic vascular resistance, cardiac index, acute subdural hematoma Introduction decrease in oxygen delivery because of the high metabolic rate and absence of substrate storage.11,16) Patients with severe head injury often require early The effect of prehospital hypotension on the long- surgical intervention which carries the risk of term outcome after head injury is well documented, developing hypoxia or hypotension.12,17,18) Evidence but the importance of intraoperative hypotension is of secondary ischemic brain damage was found in unclear.5,21) Cerebral perfusion pressure (CPP) is 66% of the patients who died of head injury, important to maintain in patients with head injuries suggesting that ischemia may be very common in the intensive care unit, so a similar policy in the during hospital treatment.18) Intraoperative hypoten- operating room would seem prudent.14) Accord- sion occurs in 32% of patients with severe head ingly, the hemodynamic mechanism of intraopera- trauma initially without hypotension, and intraoper- tive hypotension is important to understand. In ative hypotension is inversely correlated with the certain physiological states, mean arterial blood Glasgow Outcome Scale.10) Hypotension reduces the pressure (MABP) is dependent on the cardiac index delivery of substrates (oxygen and glucose) to the and systemic vascular resistance.4) Therefore, the brain tissue, which is especially vulnerable to a decrease in MABP during surgical intervention for Received March 7, 2005; Accepted December 2, 2005 Author's present address: T. Tamaki, M.D., Department of Neurosurgery, Nippon Medical School Nagayama Hospital, Tama, Tokyo, Japan. 219 220 T. Tamaki et al. severe head injury may be related to these left ventricular stroke work index, right ventricular parameters. stroke work index, and CPP using standard formu- The present study investigated the hemodynamic lae. changes which occurred during evacuation of acute The hemodynamic parameters and ICP were subdural hematoma by pulmonary artery catheteri- measured immediately before hematoma evacua- zation in patients with and without preoperative tion, defined as pre-evacuation data, and immedi- hypotension. ately after hematoma evacuation, defined as post- evacuation data. ICP monitoring and pulmonary Material and Methods artery catheter measurements were carried out at the same time. Intraoperative hypotension was This study included 15 patients with severe head defined as a decrease in MABP by more than 10 injury (Glasgow Coma Scale º8) admitted to our mmHg during surgery (post-evacuation MABP － institution within 60 minutes of injury between pre-evacuation MABP). Preoperative hypotension January and June 1997. On admission, all patients was defined as a pre-evacuation systolic blood pres- hadisolatedheadinjurywithnoevidenceof sure of less than 90 mmHg. The influence of pulmonary contusion or aspiration of gastric con- preoperative MABP on intraoperative hemodynam- tents. All patients underwent endotracheal intuba- ic changes was analyzed by classifying the patients tion and mechanical ventilation was continued into the preoperative hypotension group and during evaluation in the Emergency Department. preoperative nonhypotension group. Data were Arterial blood gas analysis was performed regularly analyzed statistically using Student's paired t-test and mean PaCO2 was maintained at 32.8 ± 0.8 and significance was accepted at p º 0.05. Correla- mmHg. All patients were given acetated Ringers tions were determined by calculating Pearson's solution at 0.01–0.03 ml/mg/hr immediately after correlation coefficients. Regression used the least admission. If the systolic blood pressure was less squares method. than 90 mmHg 20 minutes after starting infusion, dopamine was administered at 0.005 ml/mg/min. Results The definitive intracranial diagnosis was estab- lished based on computed tomography findings The clinical characteristics of the patients are given evaluated using traumatic coma data bank catego- in Table 1. The mean time from injury to hematoma ries. All patients had acute subdural hematoma in evacuation was 115 ± 32 minutes. Ten of the 15 the traumatic coma data bank category of mass patients experienced intraoperative hypotension. lesion.8) All patients underwent immediate surgery However, there was almost no intraoperative bleed- with burr holes under local anesthesia. A fiberoptic ing in all patients. Eight patients received dopamine subdural intracranial pressure (ICP) monitor support because of the marked decrease in systolic (Camino ICP monitoring system; Integra Neu- blood pressure. Hemodynamic data obtained during roScience, Andover, England) was inserted. Then a hematoma evacuation are shown in Table 2. The silicone drain tube was positioned and the acute mean time between pre-evacuation and post-evacua- subdural hematoma was evacuated slowly.20) The tion measurement of parameters was 14.3 minutes. evacuated hematoma volume was measured. In the preoperative hypotension group, the MABP, The radial artery and pulmonary artery pressures, mean pulmonary artery blood pressure, systemic central venous pressure, and pulmonary capillary vascular resistance, pulmonary vascular resistance, wedge pressure were obtained directly from pres- central venous pressure, pulmonary capillary wedge sure transducers connected to arterial catheters and pressure, and ICP all significantly decreased after a pulmonary artery catheter, which was positioned evacuation. In the preoperative nonhypotension by the Seldinger technique. Cardiac output was group, only central venous pressure showed a sig- measured in triplicate using a cardiac output nificant decrease during surgery (Fig. 1). There was computer (COM-1 9310; Baxter Edwers Critical a weak correlation between the intraoperative Care, Santa Ana, Calif., U.S.A.) after a 5-ml bolus of change in MABP and the intraoperative hematoma 5% dextrose (º109C) was injected into the right evacuation volume (r ＝ 0.29, p ＝ 0.037), but there ventricle at the end-expiratory phase of the respira- was no correlation between the intraoperative tory cycle. The heart rate was monitored from the changes in MABP and ICP (r ＝ 0.036, p ＝ 0.501) R-wave of the electrocardiogram. From the meas- (Fig. 2). ured data, we calculated the MABP, mean pulmona- ry artery blood pressure, cardiac index, systemic vascular resistance, pulmonary vascular resistance, Neurol Med Chir (Tokyo) 46, May, 2006 Hemodynamic Changes During Hematoma Evacuation 221 Table 1 Clinical characteristics of the patients Intraopera- Intraopera- Intraopera- Evacuated Case Age Initial Initial tive MABP Intraopera- tive ICP tive CPP hematoma No. (yrs) Sex SBP GCS CT findings change tive change change volume Course (mmHg) score (mmHg) hypotension (mmHg) (mmHg) (ml) 172F 1555 ASDH,CC, －11.3 ＋－13.0 1.7 55 dead SAH 253M 1504 ASDH,CC 5.0 －－16.0 21.0 40 alive 323M 1673 ASDH,CC, 3.0 －－20.0 23.0 40 alive SAH 458F 1865 ASDH,AEDH, －30.3 ＋－13.0 －16.7 95 dead CC, SAH 524M 1205 ASDH,CC, －19.3 ＋－6.0 －13.3 30 dead SAH 6 46 F 156 3 ASDH, SAH －14.0 ＋－13.0 －1.0 55 alive 7 64 M 95 5 ASDH, SAH －14.3 ＋－9.0 －4.7 65 alive 838F 656 ASDH,AEDH, －23.3 ＋－9.0 －12.4 85 dead CC, SAH 945M 563 ASDH －23.0 ＋－8.0 －15.0 75 dead 10 66 F 45 7 ASDH, SAH －9.0 －－14.0 5.0 95 dead 11 43 M 67 5 ASDH, CC, 0 －－9.0 9.0 50 dead SAH 12 44 F 80 6 ASDH, CC, －18.7 ＋－19.0 －0.3 65 alive SAH 13 35 F 67 4 ASDH, CC －22.0