Definition of Hemodynamic Thresholds in Out-of-Hospital Cardiac Arrest

Cardiopulmonary resuscitation (CPR) in patients suffering from cardiac arrest out of hospitals is based on strict clinical practice guidelines. However, the evidence base for these treatment recommendation is insufficient in many respects. While knowledge about basic interventions, that are capable of restoring spontaneous circulation and improving neurologically intact survival - chest compressions, application of oxygen and early defibrillation -, has increased over the last decade, advanced treatment options - advanced airway management, vascular access, application of vasoactive drugs - are still recommended, although clinical trials of varying quality failed to demonstrate any benefit in patient related outcomes.

This study seeks to establish hemodynamic threshold values that are able to discriminate between patients that achieve return of spontaneous circulation (survivors) and those that fail to do so (non-survivors). These cutoff values could act as targets for interventions during CPR (i.e. application of vasoactive drugs, use of mechanical compression devices, …) in further trials and may potentially influence clinical practice later on. Furthermore, reliable cutoff values could act as additional prognostic factors during CPR, enabling prehospital care providers to base their decisions to continue or terminate ongoing CPR efforts on a more solid basis.

To achieve this goal, 22 patients with out-of-hospital cardiac arrest (OHCA) treated by physicians of the prehospital physician response system located at the Medical University of Graz shall be included into this trial. All patients will receive Advanced Life Support (ALS) interventions according to current guidelines issued by the European Resuscitation Council (ERC). In addition, arterial lines will be placed and arterial blood pressure will be measured continuously. This intervention is already considered standard of care at this prehospital physician response system and performed routinely as part of the local ALS algorithm.

Relevant parameters - systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP) etc. - will be documented electronically using both the electronic documentation system already used by the prehospital physician response system and the monitor/defibrillator device. Median values will be compared between survivors and non-survivors and possible threshold values will be calculated. Cutoff values that would be best suited to act as targets in future research and clinical practice will be identified by receiver operating characteristics (ROC).