Abstract WMP27: Cerebral Blood Velocity Changes During Dobutamine Administration for Experimental Subarachnoid Hemorrhage in Mice

Introduction: Hyperdynamic therapy with dobutamine (DOB) administration on patients with subarachnoid hemorrhage (SAH) is a useful strategy for treating cerebral vasospasm and neurological deterioration. Even some reports have suggested that DOB administration caused the cerebral blood flow (CBF) augmentation by increasing cardiac output, microcirculatory behavior in brain remains unclear. Hypothesis: Red blood cell (RBC) velocity should be increased under DOB administration. To investigate the cortical microcirculation, two-photon laser scanning microscopy with successive line-scans was used for red blood cell (RBC) velocity estimation. Methods: SAH was induced in ten male wild-type C57BL/6 mice (23 - 25g) using endovascular perforation technique. Five days after SAH, a cranial window was prepared for optical access to the cortical vasculature. Then we observed two-photon microscopy with intravenously injected rhodamine-dextran. The RBC velocity was visualized as dark objects against the fluorescent plasma background. The velocity was estimated from dark objects angle in successive line-scans analyzed by Radon function based algorithm. DOB was administrated intravenously at the dose of 6 and 12 μg/kg/min. Results: RBC velocity was increased in 8 mice after the DOB administration and 2 mice were reduced. The RBC velocity in increased mice of baseline , 6 , and 12 μg/kg/min was 1.29±0.40, 1.70±0.74 and 1.37±0.53 mm/sec, respectively. In the reduced mice, the RBC velocity was dropped almost half value of baseline at the DOB administration. Conclusions: DOB administration was increased RBC velocity in cortical microcirculation. It indicates DOB hyperdynamic therapy on patients with SAH is effective in the viewpoint of cortical microcirculatory control.

Abstract T P355: Dobutamine versus Mirlinone for Intensive Hemodynamic Augmentation to Relieve Clinical Delayed Cerebral Ischemia after Subarachnoid Hemorrhage

Intensive hemodynamic augmentation by increasing cardiac output (CO) is a valuable method of elevating cerebral blood flow and oxygenation in the dysautoregulated vascular territories after subarachnoid hemorrhage (SAH). We prospectively assessed the effect of hyperdynamic therapy with dobutamine (DOB) or milrinone (MIL) on regional cerebral oxygenation (rSO 2 ) for reversing clinical deterioration induced by delayed cerebral ischemia, using an integrative monitoring with uncalibrated pulse contour CO analysis and multi-channel near-infrared spectroscopy. One-hundred ten SAH patients diagnosed to have clinical deterioration due to delayed cerebral ischemia were assigned to receive hemodynamic augmentation with DOB or MIL (n=56 per each group). For hyperdynamic therapy, each inotrope was initiated at low dose (DOB: 3μg/kg/min; MIL 0.15μg/kg/min) and then increased in each dose increment until resolution of the symptoms unless any adverse effects occur during the therapy, based on our predefined hemodynamic regimen to induce similar dose-related increase in CO. Real-time CO and rSO 2 changes in conjunction with the assessment of neurological improvements were compared. A total of 425 dose increment challenges (DOB, n=197; MIL, n=228) were performed. In spasm-affected territories, decreased and/or fluctuating rSO 2 was detected compared with recordings in other brain region. Patients who exhibited rapid elevation of CO by each challenge had subsequent uptake and stabilization of rSO 2 . The responses (total number and degree of neurological improvements) were more significant in patients treated with DOB than those treated with MIL ( P < 0.05), although tachycardia that may affect stroke volume depression during the DOB therapy was more evident (DOB 28% vs. MIL 9%). Area under the ROC curve to predict rSO 2 elevation or neurological improvement for both drug groups were significant ( P < 0.0001) and the values were significantly greater in DOB than in MIL ( P < 0.05). In conclusion, DOB can provide more effective hemodynamic augmentation in relieving focal cerebral ischemia in patients after SAH. MIL is also effective in the hyperdynamic therapy but may be used as a second line in a patient subgroup when DOB was contraindicated.

Persistent Autoregulatory Disturbance after Angioplasty for Cerebral Vasospasm

Hyperdynamic therapy, consisting of hypervolemia, haemodilution, and hypertension, is an established treatment for cerebral vasospasm following subarachnoid haemorrhage. Angioplasty has emerged as an additional, effective treatment for symptomatic vasospasm. Loss of autoregulation, however, can occur despite effective angioplasty, underscoring the need for treatment with hyperdynamic therapy in combination with angioplasty. A 43-year-old woman underwent endovascular coiling of a ruptured left posterior communicating artery aneurysm. The patient went on to develop symptomatic vasospasm and was treated with hyperdynamic therapy and angioplasty. Autoregulation was assessed with xenon CT cerebral blood flow (CBF) measurement. An initial CBF study was obtained when the patient received dopamine and dobutamine infusions to maintain systolic blood pressure at 160 mmHg. The vasopressor drips were then temporarily held for twenty minutes, allowing the patient's systolic blood pressure to drop to 140 mmHg, and a repeat CBF study was obtained. Several days after angioplasty, CBF decreased significantly when the patient was taken off vasopressors, indicating impaired autoregulation. Hyperdynamic therapy was continued, and another CBF study one week later showed a return of autoregulation and normalization of CBF without induced hypertension. Autoregulation is disturbed during vasospasm. Although angioplasty can improve large artery blood flow during vasospasm, hyperdynamic therapy is also needed to maintain cerebral perfusion, particularly in the face of impaired autoregulation. Quantitative CBF measurement permits the maintenance of optimal CBF and monitoring of response to therapy.