Although consciousness during cardiopulmonary resuscitation (CPR) is not a new phenomenon, the variables necessary to sustain consciousness during CPR have not been quantified. Despite case reports dating back several decades, as well as a recent emphasis on higher rates of external chest compressions during CPR, there is no objective benchmark that defines the hemodynamic profile necessary to maintain end-organ perfusion.
We report the case of a 62-yr-old man who was admitted for evaluation of heart failure after cardiac transplantation for dilated cardiomyopathy. The patient had been well approximately 10 min before he was found to be in pulseless electrical activity. Advanced cardiac life support was initiated and CPR was administered with palpable femoral pulses. The patient, at this point, appeared to take agonal respirations. When CPR was halted for a pulse check, however, his respiratory effort stopped. After resumption of CPR, the patient again made inspiratory efforts, moved his head, and was able to slightly open his eyes.
An epinephrine drip at 0.1 μg · kg−1 · min−1, as well as a vasopressin drip at 0.04 U/min, was initiated, and abnormal laboratory values were corrected. As chest compressions continued at a rate of approximately 100 per minute, the patient’s mental status improved to the point where he reached for the endotracheal tube. When chest compressions were held to check for a pulse, however, the patient no longer made purposeful movements.
Upon resumption of chest compressions, the patient again reached for the endotracheal tube. He was told that he was receiving life-sustaining chest compressions after his heart had stopped and that he had been intubated to assist with ventilation. The patient appeared to understand this and refrained from reaching for the endotracheal tube again. He was now able to wiggle his toes and give a “thumbs up” to command. Throughout the emergency, the patient was told what was happening in a reassuring manner by the team member at the head of the bed.
A femoral arterial line was placed, and the patient was found to have a mean arterial blood pressure (MAP) of 50 mm Hg with chest compressions at a rate of 100 per minute. He was able to follow commands with this hemodynamic profile but was unresponsive if the MAP decreased to less than approximately 50 mm Hg or if the rate decreased to <100 per minute (Table 1).
An automatic chest compression pneumatic sleeve (AutoPulse LifeBand, Revivant Corp., Sunnyvale, CA) was obtained from the emergency department but did not provide effective chest compressions. Chest compressions continued with a rotation of medical personnel. Cardiac anesthesia and cardiac surgery were emergently consulted for transfer to the operating room and initiation of cardiopulmonary bypass (CPB). As this was being discussed, the patient was transferred to the intensive care unit. Ultimately, expert consultation advised against CPB, given the lack of a realistic end point in a patient who had already had a heart transplant. Intraaortic balloon counter-pulsation was considered but thought to be insufficient to maintain the MAP of 50 mm Hg that the patient required. The patient indicated that he did not wish to continue and agreed to cease resuscitative efforts. After approximately 2 h, chest compressions were stopped and the patient died.
Consciousness during CPR is not a new phenomenon and has been reported in the literature. Coughing forcibly,1 CPR sufficient to produce a large right atrial systolic to aortic pressure gradient,2 and active compression-decompression devices3 have all been reported to support consciousness during CPR.
The importance of providing hard, fast CPR, however, is illustrated in our case. We observed that basic life support measures performed to a hemodynamic profile of 100 bpm and MAP of 50 mm Hg produced adequate forward flow to maintain cerebral perfusion. This supports the recent emphasis on chest compressions in CPR, an emphasis that has resulted in a change in the guidelines from a 15:2 compression/ventilation ratio to a 30:2 ratio.4
During nearly 2 h of CPR, a number of techniques were used to resuscitate this patient. There is a great deal of literature that examines the use of a variety of CPR devices including intrathoracic pressure regulators,5,6 inspiratory impedance threshold devices,7 and other techniques aimed at improving outcomes. Although these devices can improve organ perfusion in animals, and in limited human studies, their use is not standard.
We attempted to use an automated CPR device during this resuscitation. Porcine models using a similar automated load-distributing band device in CPR have been shown to improve coronary perfusion and myocardial flow and to improve cerebral blood flow when used with epinephrine.8 In our case, however, the device was not effective at producing compressions that maintained consciousness in our patient.
The decision to not take the patient to the operating room for initiation of CPB was based on the opinion that he was not a retransplant candidate. Interestingly, a study using CPB as a primary treatment modality (rather than a bridge to surgery) in dogs after cardiac arrest found that all had a return of spontaneous circulation.9 CPB was further found to be able to reverse normothermic ventricular fibrillation arrest of up to 15-min duration.
In our case, we used epinephrine and vasopressin infusions for vasopressor support in addition to standard basic and advanced cardiac life support. Researchers administering vasopressin in a swine model found that coronary perfusion pressure was higher and defibrillation was more often successful.10 In the end, however, as in our case, outcomes were not significantly improved. Interestingly, vasopressin is also now included in the American Heart Association Advanced Cardiac Life Support guidelines11 as a first-line medication in ventricular fibrillation arrest.
This case report quantifies MAP and rate of external chest compressions as they relate to consciousness during CPR. Basic life support generating a MAP more than 50 mm Hg, when combined with external chest compression rates more than 100 per minute, maintained end-organ perfusion sufficient to support consciousness, illustrating the need for careful attention to fast, hard CPR. The presence of an arterial catheter in a large, central artery (femoral) provided reliable documentation of the actual physiologic pressure achieved with CPR.12 This helps to validate the recent emphasis on faster rates and “harder” compression during CPR. Future evidence-based investigations in emergency cardiac care and resuscitation could benefit from an objective benchmark by which the effectiveness of CPR can be evaluated.
1. Criley JM, Blaufuss AH, Kissel GL. Cough-induced cardiac compression. JAMA 1976;236:1246–50
2. Lewinter JR, Carden DL, Nowak RM, Enriquez E, Martin GB. CPR-dependent consciousness: evidence for cardiac compression causing forward flow. Ann Emerg Med 1989;18:1111–5
3. Quinn JV, Hebert PC, Stiell IG. Need for sedation in a patient undergoing active compression-decompression cardiopulmonary resuscitation. Acad Emerg Med 1994;1:463–6
4. Yannopoulos D, Aufderheide TP, Gabrielli A, Beiser DG, McKnite SH, Pirrallo RG, Wigginton J, Becker L, Hoek TV, Tang W, Nadkarni VM, Klein JP, Idris AH, Lurie KG. Clinical and hemodynamic comparison of 15:2 and 30:2 compression-to-ventilation ratios for cardiopulmonary resuscitation. Crit Care Med 2006;34:1444–9
5. Yannopoulos D, Aufderheide TP, McKnite S, Kotsifas K, Charris R, Nadkarni V, Lurie KG. Hemodynamic and respiratory effects of negative tracheal pressure during CPR in pigs. Resuscitation 2006;69:487–94
6. Yannopoulos D, Nadkarni VM, McKnite SH, Rao A, Kruger K, Metzger A, Benditt DG, Lurie KG. Intrathoracic pressure regulator during continuous-chest-compression advanced cardiac resuscitation improves vital organ perfusion pressures in a porcine model of cardiac arrest. Circulation 2005;112:803–11
7. Pirrallo RG, Aufderheide TP, Provo TA, Lurie KG. Effect of an inspiratory impedance threshold device on hemodynamics during conventional manual cardiopulmonary resuscitation. Resuscitation 2005;66:13–20
8. Halperin HR, Paradis N, Ornato JP, Zviman M, Lacorte J, Lardo A, Kern KB. Cardiopulmonary resuscitation with a novel chest compression device in a porcine model of cardiac arrest: improved hemodynamics and mechanisms. J Am Coll Cardiol 2004;44:2214–20
9. Safar P, Abramson NS, Angelos M, Cantadore R, Leonov Y, Levine R, Pretto E, Reich H, Sterz F, Stezoski SW. Emergency cardiopulmonary bypass for resuscitation from prolonged cardiac arrest. Am J Emerg Med 1990;8:55–67
10. Babar SI, Berg RA, Hilwig RW, Kern KB, Ewy GA. Vasopressin versus epinephrine during cardiopulmonary resuscitation: a randomized swine outcome study. Resuscitation 1999;41:185–92
11. Kern KB, Halperin HR, Field J. New guidelines for cardiopulmonary resuscitation and emergency cardiac care. JAMA 2001;285:1267–9
12. Dorman T, Breslow MJ, Lipsett PA, Rosenberg JM, Balser JR, Almog Y, Rosenfeld BA. Radial artery pressure monitoring underestimates central arterial pressure during vasopressor therapy in critically ill surgical patients. Crit Care Med 1998;26:1623–4