Bedside Monitoring of Cerebral Energy State During the Peri-cardiac Arrest Period - Blood Pressure Targets in Post Resuscitation Care

Microdialysis assessment of cerebral energy state during cardiac arrest and cardiopulmonary resuscitation in humans

In comatose patients resuscitated from out of hospital cardiac arrest (OHCA), neurological injuries remain the leading cause of death. The in-hospital mortality is reported at 30-50%, and the total mortality, although improved substantially over the last decade, remain to be significant, in most countries at up to 90%. The brain of a patient resuscitated after cardiac arrest (CA) may have suffered ischemia and when spontaneous circulation is re-established, the subsequent reperfusion may cause further damage. Brain ischemia and the reperfusion injury lead to tissue degeneration and loss of neurological function, the extent dependent on duration and density of the insult. Temperature control and Targeted Temperature Management (TTM) targeting 33-36°C may mitigate this damage and is recommended in current international guidelines. However, managing post cardiac arrest patients are much more complicated than TTM alone, and blood pressure measurements and mechanical ventilation as part of post resuscitation care is emphasized. An adequate blood pressure must be maintained in the post-cardiac arrest patient. Episodes of hypotension can cause secondary injury, in addition to any initial insult incurred during the arrest by the brain and other organs. Mean arterial blood pressure (MAP) should be above 65 mmHg to reverse the acute shock state, and may preferably 80 to 100 mmHg to optimize cerebral perfusion. When determining blood pressure goals, clinicians must balance the metabolic needs of an ischemic brain with the potential for overstressing a decompensated heart. Cerebral autoregulation is often impaired after cardiac arrest, and brain perfusion declines when the MAP falls below 80 to 100 mmHg. Thus, maintaining an adequate MAP helps to avoid further brain injury. However, blood pressure goals have not been investigated in prospective clinical trials, and remain to be based on observational data and extrapolation from experimental data. While experimental studies suggest that high mean blood pressure targets are needed for maintaining cerebral blood flow, registries on consecutive clinical cases undergoing post resuscitation care suggest that lower blood pressure targets are used in clinical practice. But data RCT´s addressing specific targets in post resuscitation care have not been performed. The current trial addresses these strategies for neuroprotection in using design of two different target blood pressure levels. Intervention: 1:1 randomization:

"Normal MAP" (approximately 65 mmHg) vs. "high MAP" (approximately 75 mmHg) Markers measuring global cerebral ischemia caused by cardiac arrest and consecutive resuscitation, and reflecting the metabolic changes after successful resuscitation are urgently needed to enable a more personalized resuscitation and post resuscitation care.

It is technically simple and feasible to place a microdialysis catheter in the jugular bulb and monitor biochemical variables related to cerebral energy metabolism bedside. The LP ratio obtained from microdialysis of cerebral venous blood may be a sensitive indicator of impending cerebral damage and might play a critical role in detecting the early responses of post resuscitation care. Aim of this study is to investigate the global cerebral metabolic changes during CA and post-resuscitation care.

Aim: The study aim to (I) investigate whether the LP ratio obtained by microdialysis (MD) of the cerebral venous outflow reflects a derangement of global cerebral energy state during the peri-cardiac arrest period and (II) investigate the correlation between LP ratio and neurological outcome among patients with cardiac arrest and (III) investigate the correlation between LP ratio and the randomized blood pressure targets.