By Mike McEvoy
A study published in the April 2013 issue of Circulation found both hypercapnia and hypocapnia lead to poor neurologic outcomes after cardiac arrest1. The Guidelines 2010 recommend titrating ventilation after return of spontaneous circulation (ROSC) to maintain an arterial carbon dioxide level of 40 to 45 mmHg2. Capnography is commonly used by field providers and provides similar results. Few studies have ever looked at how often ventilation is mismanaged and what consequences result for patients.
Of 393 patients studied who experienced prehospital or in-hospital cardiac arrest between 2009 and 2011, both hyperventilation leading to hypocapnia (defined as PaCO2 < 30) and hypoventilation resulting in hypercapnia (defined as PaCO2 < 50) were common, affecting 73 percent of patients. Both conditions were independently associated with poor neurological outcome at hospital discharge. In other words, patients were more 2.43 times more likely to leave the hospital with serious brain dysfunction when they had hypocapnia post arrest and had 2.20 times more serious brain dysfunction when they hypercapnic at any time post arrest. Brain function is rated using a 5-point Cerebral Performance Score (CPC) where 1 indicates good cerebral performance; 2, moderate cerebral disability; 3, severe cerebral disability; 4, coma/vegetative state; and 5, death. Serious dysfunction was defined as CPC > 3 in this study.
This is an important study highlighting the need for close attention to ventilation post cardiac arrest. It provides additional ammunition for EMS use of continuous waveform capnography in any mechanically ventilated patient.
1. Roberts BW, Kilgannon JH, Chansky ME, Mittal N, Wooden J, Trzeciak S. Association Between Postresuscitation Partial Pressure of Arterial Carbon Dioxide and Neurological Outcome in Patients With PostâCardiac Arrest Syndrome. Circulation. 2013; 127: 2107-2113.
2. Peberdy MA, Callaway CW, Neumar RW, Geocadin RG, Zimmerman JL, Donnino M, Gabrielli A, Silvers SM, Zaritsky AL, Merchant R, Vanden Hoek TL, Kronick SL. Part 9: post-cardiac arrest care: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010;122(18 suppl 3):S768âS786.
MIKE McEVOY, PhD, NRP, RN, CCRN is the EMS Coordinator for Saratoga County, NY and the Fire Engineering EMS editor. He is a professor emeritus of critical care medicine at Albany Medical College in New York and continues to practice as a clinical nurse specialist in the Cardiac Surgical ICUs at Albany Medical Center. Mike is a paramedic for Clifton Park & Halfmoon Ambulance and the Chief Medical Officer for West Crescent Fire Department. He is a Board Member of the New York State Association of Fire Chiefs and a popular speaker at Fire, EMS, and medical conference worldwide.