Background: Current guidelines for post resuscitation care recommend targeting mean arterial pressure (MAP) above 65 mmHg, but there is limited science to support these recommendations. Some registry- and observational data indicate better outcome with higher blood pressures. However, initial resuscitation during post resuscitation care needs to balance the brains need for perfusion with the hearts need for restitution. We hypothesized that maintaining a MAP of 90 mmHg would yield improved cerebral blood flow and metabolism compared to 60 mmHg.
Methods: Swine (35 kg) were anesthetized and instrumented prior to electrical induction of ventricular fibrillation. After 10 minutes of cardiac arrest, animals were resuscitated using a heart-lung machine at 100 ml/kg/min for two minutes before defibrillation. After ROSC, animals were randomized to MAP 90 or MAP 60, and blood pressure targets were managed with vasopressin, norepinephrine or nitroprusside. After a 30 minute stabilization period, animals were observed for an additional two hours. Brain tissue pCO2, brain microdialysis (results to be analysed), carotid and intracerebral flow, intracerebral pressure, aortic pressure, right and left ventricular pressures were measured continuously. Values were extracted and analyzed for 15 minute epochs. All values listed are means ± standard deviation.
Results: Preliminary results were available for 8 and 6 planned animals in MAP 90 and 60 groups, respectively (total of 20 animals to be included). Absolute values indicate improved cerebral flow (146±44% vs. 94±24% of baseline), carotid flow (226±18 vs. 191±22 ml/min),and and lower brain tissue pCO2 (8.6±0.7 vs. 10.3±1.9 kPa) in the MAP 90 group 150 min after ROSC. There was improved cardiac function with higher cardiac output (4.4±0.3 vs. 4.0±0.2 l/min), left ventricular dp/dt max (1252±98 vs. 920±86 mmHg/sec), and mixed central venous saturation (58±4% vs. 49±6%), and lower left ventricular dp/dt min (-1243±108 vs. -830±98 mmHg/sec) and left ventricle end-diastolic pressure (6±2 vs. 10±1 mmHg) with MAP 90.
Conclusion: Preliminary results suggest targeting MAP to 90 mmHg after cardiac attest might provide better cerebral perfusion compared to 60 mmHg in a normothermic porcine model.