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Cardiopulmonary Resuscitation

Nathan Peterson, DVM, DACVECC

VCA West Los Angeles Animal Hospital, Los Angeles, CA, USA

Approximately 330,000 people die of acute cardiac arrest patients will exhibit loss of consciousness, absence of
in the United States annually. The incidence of unex- spontaneous ventilation, absence of heart sounds during
pected cardiopulmonary arrest (CPA) in veterinary auscultation, and absence of palpable pulses.
patients is currently unknown. What is known is that The importance of recognizing CPA quickly is under-
survival rates for dogs and cats that receive cardiopul- scored when the hemodynamic impact is considered.
monary resuscitation (CPR) range from 2.6% to 25%. Following the onset of CPA, the aortic blood pressure
The reported survival rates for people experiencing CPR drops precipitously, with intrathoracic aortic pressure
are equally dismal, with overall survival rates following dropping from a normal of approximately 120 mmHg to
in‐hospital arrest ranging from 3% to 27%. The reason 20 mmHg within 30 seconds. Additionally, carotid blood
for the wide range in outcomes is due in part to the vari- flow decreases from an average of 190 mL/min to 15 mL/
ance in the nature or cause of cardiopulmonary arrest. min within 15 seconds and to 0 mL/min within four min-
What the literature generally agrees on is that the chance utes. Coronary perfusion pressure likewise drops from
of a patient surviving to discharge after CPA is small. The 60 mmHg to 15 mmHg within 15 seconds and to 0 mmHg
likelihood of survival increases if CPA was due to an within four minutes.
anesthetic event rather than the culmination of a chronic Although the underlying cause of CPA may not be
or traumatic disease process. While the survival statis- immediately apparent to the clinician, the nature or
tics are dismal, the long‐term neurologic outcomes of cause of the arrest can have an impact on the expected
patients surviving CPA are generally good to excellent, outcome and should be ascertained as soon as possible.
making CPR a worthy endeavor. If a patient is known to have suffered respiratory arrest
In 2010, veterinary‐specific CPR guidelines were devel- prior to cardiac arrest, the likelihood of resuscitation
oped using an evidence‐based approach modeled on the may be diminished due to the continued depletion of
American Heart Association’s CPR guidelines. The result oxygen from circulating blood resulting in severe hypox-
of this effort was the publication of the Reassessment emia at the onset of cardiac failure and institution of
Campaign on Veterinary Resuscitation (RECOVER) in CPR. Conversely, if an animal suffers sudden cardiac
2011. The RECOVER initiative (http://onlinelibrary.wiley. arrest, the blood oxygen content would be expected to be
com/doi/10.1111/vec.2012.22.issue‐s1/issuetoc) has pro- high at the onset of CPA and subsequent CPR, possibly
vided veterinarians for the first time with evidence‐based making successful resuscitation more likely than in the
clinical guidelines for performance of CPR. previous instance.
The progression from severe illness to cardiopulmo-
nary arrest in the veterinary patient is complex. Diseases
that can lead to CPA in veterinary medicine include but Principles of CPR
are not limited to sepsis, pulmonary failure, neoplasia,
polytrauma, head trauma, and cardiac failure. Although Cardiopulmonary resuscitation is intended to provide
not all animals progressing toward CPA follow the same blood flow to the heart and brain, preserving them until
clinical course, some physical exam findings that may return of spontaneous circulation (ROSC) is achieved.
indicate impending CPA include decreasing level of con- Subsequently, the quality of chest compressions is of
sciousness, hypothermia, bradycardia, hypotension, and the utmost importance, since this is the mechanism by
changes in respiratory patterns. Once CPA occurs, all which circulation is generated. Whatever the technique,

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical