Cardiopulmonary resuscitation: current recommendations

Early recognition of CPA is the key to its successful management. For resuscitation to be managed successfully, effective forward blood flow must be established at the onset of the arrest. In our clinical experience, we have found that the Doppler unit allows us to assess the effectiveness of cerebral perfusion better than any other method of blood pressure evaluation. If, by Doppler monitoring results, cerebral perfusion is found to be poor, blood flow may be mechanically improved by instituting high dose epinephrine therapy and interposed abdominal counter-pressure techniques. There is an understandable reluctance on the part of many veterinarians to enter the chest in the course of CPR. Unfortunately, this delay in performing internal compressions is often the reason that open-chest CPR is deemed ineffective by so many practitioners. If external chest CPR is not effective within 1 to 2 min (maximum) of its initiation, an emergency thoracotomy and direct cardiac massage should be performed. We know that perfusion pressure increases three to five times with open versus closed-chest CPR. This improvement in perfusion with direct cardiac massage is due, in part, to the absence of venous pressure elevations created during external chest compression. It follows that better coronary and cerebral blood flow will result in better resuscitation when direct cardiac massage is performed early. The "bottom line" in CPR is successful resuscitation of the patient with resultant good neurologic function. It is hoped that through the use of these techniques and new cytoprotective drugs, the survival rate will rise.     

Cardiopulmonary resuscitation with vasopressin in a dog

That endogenous vasopressin levels in successfully resuscitated human patients were significantly higher than in patients who died pointed to the possible benefit of administering vasopressin during cardiopulmonary resuscitation (CPR). Several CPR studies in pigs showed that vasopressin improved blood flow to vital organs, cerebral oxygen delivery, resuscitability and neurological outcome when compared with epinephrine. In a small clinical study, vasopressin significantly improved short-term survival when compared with epinephrine indicating its potential as an alternative pressor to epinephrine during CPR in human beings. As there was little clinical data available at that time, its recommended use was limited to adult human beings with shock-refractory ventricular fibrillation. In this report, we present the case of a dog in which the successful management of intraoperative asystolic cardiac arrest involved vasopressin. Unexpected cardiac arrest occurred during anaesthesia for the surgical removal of multiple mammary adenocarcinomata in a 11-year-old Yorkshire terrier. Despite an ASA physical status assignation of III, the dog was successfully resuscitated with external chest compressions, intermittent positive pressure ventilation and vasopressin (2 doses of 0.8 IU kg(-1)) and was discharged 3 days later without signs of neurological injury. We believe vasopressin contributed to restoring spontaneous circulation. It may prove increasingly useful in perioperative resuscitation in dogs.     

Controversial issues in drug treatment during cardiopulmonary resuscitation.

The goal of advanced life support in CPR must be to restore and maintain respiratory and hemodynamic effectiveness, and to correct the underlying dysrhythmia. Optimal basic life-support techniques must be continued to meet these goals. Many drugs have been suggested in the treatment of cardiac arrest, but unfortunately, drug effects are inconsistent and resuscitation rates remain low. Epinephrine, atropine, lidocaine, bretylium, and naloxone remain important drugs for consideration in CPR in most animals with cardiac arrest. The best chance of survival remains in early recognition of animals susceptible to arrest and in treatment of the underlying cause.     

The Effect of Resuscitation Technique and Pre-Arrest State of Oxygenation on Blood–Gas Values during Cardiopulmonary Resuscitation in Dogs

Large mongrel dogs were anesthetized, instrumented, and subjected to electrically induced ventricular fibrillation after breathing either 100% oxygen (O2) or 10% O2 and 90% nitrogen for 10 minutes before arrest. Four minutes after arrest, open chest cardiopulmonary resuscitation (CPR) or intermittent abdominal compression closed chest CPR was initiated and continued for 20 minutes, at which time defibrillation was attempted. Central arterial and mixed venous blood samples were collected serially for the measurement of pH, carbon dioxide partial pressure (PCO2), and O2 partial pressure (PO2), and calculation of bicarbonate concentration and base excess. Mixed venous blood was collected serially for the measurement of lactate concentration. Hemodynamically variable resuscitation techniques and pre-arrest hypoxia or hyperoxia did not significantly influence blood-gas values during CPR. Mixed venous lactate concentrations after 20 minutes of CPR were significantly higher when hypoxia preceded the arrest and when intermittent abdominal compression closed chest CPR was used for resuscitation. Mixed venous PCO2 was significantly higher than arterial PCO2 in all dogs during CPR but was not significantly different before arrest.     

Survival Following Cardiopulmonary Resuscitation in Dogs and Cats

Dogs and cats receiving cardiopulmonary resuscitation (CPR) were evaluated for factors leading to cardiac arrest and for survival following the procedure. One-hundred-thirty-five canine and forty-three feline patients seen at the University of California, Davis Veterinary Medical Teaching Hospital that received CPR between August 1987 and December 1991 were studied. Initial resuscitation attempts were unsuccessful in 72% of dogs and 58% of cats. Five dogs and one cat were still alive 3 days after CPR. Ultimately only four dogs and one cat were discharged from the hospital alive. These five patients with uniquely longer survival all had cardiac arrests associated with drug and/or anesthetic reactions.     

Application of impedance threshold devices during cardiopulmonary cerebral resuscitation

Objective – To review the use of impedance threshold devices (ITD) during CPCR, their proposed mechanism of action, and their application in veterinary medicine. Data Sources – Data sources include scientific reviews and original research publications using the PubMed search engine with the following keywords: ‘impedance threshold device’ and ‘resuscitation’ and the Veterinary Information Network search function using the keywords ‘impedance threshold device.’ Human Data Synthesis – Studies in human medicine have demonstrated that the use of an ITD during CPCR in patients during out‐of‐hospital cardiac arrest improves coronary perfusion pressure and cerebral perfusion pressure. This improvement in vital organ blood flow results in increased cardiac output and faster return of spontaneous circulation. The use of an ITD has been studied in people and currently holds a class IIb level of recommendation according to the 2010 American Heart Association Guidelines for CPR and Emergency Cardiovascular Care. This device is recommended as a way to improve hemodynamics during CPCR by enhancing venous return and avoiding hyperventilation, thereby increasing the likelihood of a successful resuscitation. Veterinary Data Synthesis – Multiple controlled studies using pigs with ventricular fibrillation induced cardiopulmonary arrest have demonstrated increased myocardial and cerebral perfusion with the use of an ITD. These studies have emphasized the importance of decreasing intrathoracic pressures during the decompression phase of CPCR and avoiding hyperventilation in order to maximize vital organ blood flow. Conclusions – Use of an ITD during CPCR in human and animal studies has demonstrated improved vital organ perfusion and faster return of spontaneous circulation. However, the majority of these studies have been carried out in people during out‐of‐hospital cardiac arrest and ventricular fibrillation cardiopulmonary arrest pig models. Further studies evaluating the use of an ITD during CPCR in the veterinary hospital setting are warranted.     

Resuscitation attempts in a foal with sudden cardiac arrest in the early recovery period

A 3‐month‐old female Warmblood foal, weighing 150 kg, was presented to the Equine Clinic of the University of Hannover with a fracture of the ulna (type 5 fracture of the olecranon). Anaesthesia was induced with midazolam and ketamine after sedation with xylazine and maintained with isoflurane. Anaesthesia was uneventful until cardiac arrest occurred in the early recovery period. Cardiopulmonary resuscitation (CPR) was performed with chest compressions and electrical defibrillation. During resuscitation palpebral reflexes and spontaneous breathing returned but ventricular fibrillation could not be converted to sinus rhythm by transthoracic defibrillation of the heart by electrical shock.     

Intraosseous injection during cardiopulmonary resuscitation in dogs

Five mixed breed dogs were used to investigate the feasibility of femoral intraosseous injection during cardiac arrest. The intraosseous route was evaluated in the anaesthetised dogs after induction of cardiac arrest. Fluorescein dye was injected through pre-placed intraosseous catheters during cardiac massage. The dye was detected at the membrana nictitans five to 12 seconds later indicating successful transfer from the femoral marrow cavity to the systemic circulation during cardiopulmonary resuscitation (CPR). The clinical value of intraosseous injection during CPR is discussed and compared with the endotracheal administration of drugs.     

Cardiopulmonary cerebral resuscitation.

Cardiopulmonary arrest (CPA) is defined as the abrupt and unexpected cessation of spontaneous and effective ventilation and circulation. CPA can be the natural ending of a normal and long life; however, when CPA is the result of a reversible problem in an animal that has a treatable medical condition, rapid recognition and treatment may make the difference between a happy ending and premature death. Cardiopulmonary resuscitation provides artificial ventilation and circulation until advanced cardiac life support can be provided and spontaneous cardiopulmonary function is restored. The term cardiopulmonary cerebral resuscitation originated in the early 1960s in recognition of the severe central nervous system complications of prolonged cardiac arrest in human beings. Although neurologic complications of CPA may not be as noticeable in companion animals, newer brain-sparing strategies that recognize the consequences of reperfusion injury and the inflammatory cascade may some day offer improved survival.     

Cardiopulmonary resuscitation

Cardiopulmonary resuscitation (CPR) is a technique used in both human and veterinary medicine. Although a number of innovative adaptations to CPR have been researched, the mainstay of CPR remains intubation, adequate ventilation, chest compressions, and basic drug therapy. The purpose of this article is to review the techniques and drugs commonly used in both closed chest and open chest CPR.     

Full recovery after cardiac arrest secondary to accidental iatrogenic venous air embolism in a cat

Objective – To describe the successful management of cardiac arrest following accidental venous air embolism (VAE) in a cat. Case Summary – A 3‐year‐old spayed female domestic shorthair cat, weighing 4 kg, was presented for continuation of its chemotherapy protocol. The cat was inadvertently administered approximately 5.5 mL of air IV during initiation of fluid therapy. Immediate cardiac arrest resulted and CPR successfully achieved return of spontaneous circulation. The cat was discharged 5 days later and is reportedly clinically normal 7 months post‐discharge. New or Unique Information Provided – VAE has been rarely reported in the veterinary literature. This is the first report of a cat surviving cardiac arrest secondary to VAE.     

The use of vasopressin for treating vasodilatory shock and cardiopulmonary arrest

Objective – To discuss 3 potential mechanisms for loss of peripheral vasomotor tone during vasodilatory shock; review vasopressin physiology; review the available animal experimental and human clinical studies of vasopressin in vasodilatory shock and cardiopulmonary arrest; and make recommendations based on review of the data for the use of vasopressin in vasodilatory shock and cardiopulmonary arrest. Data Sources – Human clinical studies, veterinary experimental studies, forum proceedings, book chapters, and American Heart Association guidelines. Human and Veterinary Data Synthesis – Septic shock is the most common form of vasodilatory shock. The exogenous administration of vasopressin in animal models of fluid‐resuscitated septic and hemorrhagic shock significantly increases mean arterial pressure and improves survival. The effect of vasopressin on return to spontaneous circulation, initial cardiac rhythm, and survival compared with epinephrine is mixed. Improved survival in human patients with ventricular fibrillation, pulseless ventricular tachycardia, and nonspecific cardiopulmonary arrest has been observed in 4 small studies of vasopressin versus epinephrine. Three large studies, though, did not find a significant difference between vasopressin and epinephrine in patients with cardiopulmonary arrest regardless of initial cardiac rhythm. No veterinary clinical trials have been performed using vasopressin in cardiopulmonary arrest. Conclusion – Vasopressin (0.01–0.04 U/min, IV) should be considered in small animal veterinary patients with vasodilatory shock that is unresponsive to fluid resuscitation and catecholamine (dobutamine, dopamine, and norepinephrine) administration. Vasopressin (0.2–0.8 U/kg, IV once) administration during cardiopulmonary resuscitation in small animal veterinary patients with pulseless electrical activity or ventricular asystole may be beneficial for myocardial and cerebral blood flow.     

Cardiopulmonary resuscitation in small animal medicine: an update

In December 2005, the American Heart Association published new guidelines for cardiopulmonary cerebral resuscitation (CPCR) in humans for the 1st time in 5 years. Many of the recommendations are based on research conducted in animal species and may be applicable to small animal veterinary patients. One important change that may impact how CPCR is performed in veterinary medicine is the recommendation to avoid administration of excessive ventilatory rates because this maneuver severely decreases myocardial and cerebral perfusion, decreasing the chance of survival. The new guidelines also emphasize the importance of providing well-executed, continuous, uninterrupted chest compressions. Interruption of chest compressions should be avoided and, if necessary, should be minimized to <10 seconds. During defibrillation, immediate resumption of chest compressions for 2 minutes after a single shock, before reassessment of the rhythm by ECG, is recommended. This recommendation replaces previous recommendations for the delivery of 3 defibrillatory shocks in rapid succession. Allowing permissive hypothermia postresuscitation has been found to be beneficial and may increase success rate. Medications utilized in cardiopulmonary resuscitation, including amiodarone, atropine, epinephrine, lidocaine, and vasopressin, along with the indications, effects, routes of administration, and dosages, are discussed. The application of the new guidelines to veterinary medicine as well as a review of cardiopulmonary resuscitation in small animals is provided.     

Effects of body position and ventilation/compression ratios during cardiopulmonary resuscitation in cats

Eighteen cats were anesthetized and were randomly assigned to 2 groups (9 cats/group). Cardiopulmonary resuscitation (CPR) was performed on each cat, with the cat in dorsal (group 1) or lateral (group 2) recumbency, by administering 5 external cardiac compressions/1 interposed (diastolic) ventilation (American Heart Association [AHA] technique; n = 3 cats/technique), simultaneous compression and ventilation (SCV; n = 3 cats/technique), or SCV with 1 interposed (diastolic) ventilation every tenth compression (SCV/DV; n = 3 cats/technique). Fourteen of the 18 cats were resuscitated. Central aortic and venous pressures were determined concurrently with lead II electrocardiography. Arterial blood samples were collected during the base-line period (after pressure fluctuations had stabilized, with the cats spontaneously breathing room air), 2.5 minutes after the onset of arrest (defined as the cessation of aortic pressure fluctuations), and after 10 minutes of CPR. Arterial blood gas values during the base-line period or during the period of arrest were not significantly different between group-1 and group-2 cats. After CPR, arterial pH and bicarbonate values were not significantly different between groups or between technique categories. The PaCO2 values were significantly lower in cats resuscitated by SCV or by SCV/DV than in cats resuscitated by AHA (P less than 0.05). The PaO2 values were significantly (P less than 0.001) higher in group-2 cats than in group-1 cats and were significantly (P less than 0.001) different between each technique category, with cats resuscitated by AHA having the lowest PaO2 and cats resuscitated by SCV/DV having the highest PaO2. Body position, CPR technique, sex, weight, or arterial blood gas values after CPR were not predictors of successful resuscitation.     

Successful resuscitation from cardiac arrest associated with extradural lidocaine in a dog

BACKGROUND: Extradural lidocaine exerts several adverse effects which are seldom fatal. While cardiac arrest following extradural lidocaine injection has been reported in human beings, it has not hitherto been reported in dogs. OBSERVATIONS: The emergency management of a dog with complete urethral obstruction is described. We intended to perform vaginoscopy and cystostomy under extradural lidocaine anaesthesia, but cardiac asystole occurred a few minutes after injection. Resuscitation was successful. About 20 minutes later cardiac arrest recurred, and was treated successfully. The dog remained hypothermic for approximately 7 hours. Complete recovery without neurological deficit occurred the next day and the dog remained normal for at least 3 months. The probable cause of the problem was cranial lidocaine dispersion causing a drop in cardiac preload and cardiac arrest. The successful neurological outcome was attributed to early diagnosis and effective treatment. Hypothermia may have conferred cerebral protection during ischemia. CONCLUSIONS: Extradural local anaesthetic administration is not without risk and the technique should be tailored to individual animals. Constant monitoring is required to detect potentially fatal complications and increase the likelihood of successful outcome.     

Successful cardiopulmonary resuscitation in an adult horse following cardiovascular collapse on recovery from general anaesthesia in the Trendelenburg position

Equine anaesthesia is associated with a high risk of perioperative morbidity and mortality, particularly in the recovery period. Cardiovascular collapse and cardiopulmonary arrest (CPA) have been reported to account for one-third of anaesthesia-related perioperative deaths in the horse. This case report describes the successful cardiopulmonary resuscitation of a healthy adult Thoroughbred mare that developed cardiovascular collapse and subsequent CPA following positioning in the recovery box after general anaesthesia in the Trendelenburg position. Cardiopulmonary resuscitation (CPR) was instigated and included thoracic compressions, intermittent positive pressure ventilation and adrenaline administered via the intravenous and intra-tracheal routes. Return of spontaneous circulation (ROSC) was detected 5 min and 50 s after the start of CPR. A stable stance was achieved approximately 100 min after ROSC. The mare was discharged from the hospital 3 days later with no known complications. To the authors’ knowledge, this is the first case report documenting CPA following general anaesthesia in the Trendelenburg position in a horse, with subsequent successful CPR. The precise cause of the CPA is unknown but a number of plausible hypothesis are discussed including hypoventilation and a Bezold-Jarisch reflex.     

Prevalence and factors associated with initial and subsequent shockable cardiac arrest rhythms and their association with patient outcomes in dogs and cats undergoing cardiopulmonary resuscitation: A RECOVER registry study

Objective

To report the prevalence of initial shockable cardiac arrest rhythms (I-SHKR), incidence of subsequent shockable cardiac arrest rhythms (S-SHKR), and factors associated with I-SHKRs and S-SHKRs and explore their association with return of spontaneous circulation (ROSC) rates in dogs and cats undergoing CPR.

Design

Multi-institutional prospective case series from 2016 to 2021, retrospectively analyzed.

Setting

Eight university and eight private practice veterinary hospitals.

Animals

A total of 457 dogs and 170 cats with recorded cardiac arrest rhythm and event outcome reported in the Reassessment Campaign on Veterinary Resuscitation CPR registry.

Measurements and Main Results

Logistic regression was used to evaluate association of animal, hospital, and arrest variables with I-SHKRs and S-SHKRs and with patient outcomes. Odds ratios (ORs) were generated, and significance was set at P < 0.05. Of 627 animals included, 28 (4%) had I-SHKRs. Odds for I-SHKRs were significantly higher in animals with a metabolic cause of arrest (OR 7.61) and that received lidocaine (OR 17.50) or amiodarone (OR 21.22) and significantly lower in animals experiencing arrest during daytime hours (OR 0.22), in the ICU (OR 0.27), in the emergency room (OR 0.13), and out of hospital (OR 0.18) and that received epinephrine (OR 0.19). Of 599 initial nonshockable rhythms, 74 (12%) developed S-SHKRs. Odds for S-SHKRs were significantly higher in animals with higher body weight (OR 1.03), hemorrhage (OR 2.85), or intracranial cause of arrest (OR 3.73) and that received epinephrine (OR 11.36) or lidocaine (OR 18.72) and significantly decreased in those arresting in ICU (OR 0.27), emergency room (OR 0.29), and out of hospital (OR 0.38). Overall, 171 (27%) animals achieved ROSC, 81 (13%) achieved sustained ROSC, and 15 (2%) survived. Neither I-SHKRs nor S-SHKRs were significantly associated with ROSC.

Conclusions

I-SHKRs and S-SHKRs occur infrequently in dogs and cats undergoing CPR and are not associated with increased ROSC rates.