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.     

Causes of cardiopulmonary arrest, resuscitation management, and functional outcome in dogs and cats surviving cardiopulmonary arrest

Objective: To describe the functional outcome of canine and feline survivors of cardiopulmonary arrest (CPA) and the clinical characteristics surrounding their resuscitation. Design: Retrospective study. Setting: Veterinary teaching hospital. Animals: Client‐owned dogs (15) and cats (3) with CPA. Interventions: None. Measurements and main results: Eighteen animals were identified to have survived to discharge following CPA. Cardiopulmonary arrest was associated with anesthesia with or without pre‐existing disease in 10 animals, cardiovascular collapse in 5 animals, and chronic disease with an imposed stress in 3 animals. All CPAs were witnessed in the hospital. The most common initial rhythm at CPA was asystole (72%). Return of spontaneous circulation (ROSC) was achieved in less than 15 minutes from the onset of cardiopulmonary cerebral resuscitation (CPCR) in all animals. No animals had a recurrence of CPA after the initial CPA. Animals were of a wide range of ages (0.5–16 years) and breeds. Two animals were neurologically abnormal at discharge, one of which was normal at 2 months following CPA. Conclusions: A good functional recovery after CPCR was documented in the small number of CPA survivors presented in this study. This may be due to the reversible nature of their inciting cause of CPA, early detections of CPA (‘witnessed’), and/or the animal's underlying normal health status.     

Current developments in c ar diopulmonary resuscitation

As veterinary surgeons, we must all deal, on occasion, with an animal who has suffered a cardiac arrest. This article reviews the recent literature concerning cardiopulmonary resuscitation (CPR) and examines the suggestions recently put forward by the American Heart Association in their improved resuscitation protocol. These protocol modifications have been shown experimentally and clinically to improve cerebral and myocardial haemodynamics during closed chest cardiac massage. The ultimate goal of CPR must be not merely to resuscitate the patient in the short term, but to promote complete neurological recovery in the longer term. Prompt recognition of cardiac arrest and the immediate initiation of resuscitative measures play a major contributing role in a favourable neurological outcome. In addition to the familiar ABC system of basic cardiac life support, the use of a high dose adrenaline (0–2 mg/kg) is proposed as the best first line drug treatment in the arrested patient. This can be accompanied by abdominal wrapping and synchronous ventilation and chest compressions to optimise cerebral and myocardial blood flow. Calcium chloride and sodium bicarbonate should no longer be included in the early resuscitative efforts.     

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.     

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.     

Successful cardiopulmonary resuscitation and use of short-term mechanical ventilation following inadvertent ketamine overdose in a cat

Objective: To describe the clinical manifestations and successful outcome following an inadvertent overdose of ketamine to a cat. Case summary: A 4‐year‐old neutered male domestic shorthair cat was evaluated for a urethral obstruction. Because of an inadvertent miscalculation of ketamine, 20 times the intended dose was administered intravenously, which resulted in cardiopulmonary arrest. Cardiopulmonary‐cerebral resuscitation was successful, and short‐term mechanical ventilation, fluids and intensive monitoring were utilized to achieve full recovery and subsequent discharge of the animal. New or unique information provided: Ketamine is a common anesthetic agent used in cats that is considered to have a wide therapeutic index and minimal cardiopulmonary depressant effects at recommended doses. Successful management of inadvertent ketamine overdose has been reported in children, but not in cats. Prompt CPCR and short‐term mechanical ventilation may be necessary to treat a significant ketamine overdose. In cats, yohimbine may act as a partial antagonist of ketamine.     

Respiratory and cardiopulmonary arrest in dogs and cats: 265 cases (1986-1991).

Outcomes of cardiopulmonary arrest and resuscitation in clinically affected dogs and cats have not been adequately studied. We examined the records from 200 dogs and 65 cats that had received cardiopulmonary resuscitation for respiratory or cardiopulmonary arrest; none of the animals had been anesthetized or intubated at the time of arrest, and all had been hospitalized in a veterinary critical care facility. Cardiopulmonary arrest was found to be more common than respiratory arrest in dogs and cats. Hospital discharge rates for animals with cardiopulmonary arrest ranged from 4.1% for dogs to 9.6% for cats, and were consistent with those reported from studies of human beings with cardiopulmonary arrest. Hospital discharge rates for dogs and cats with respiratory arrest were 28% and 58.3%, respectively.     

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.     

Cardiopulmonary cerebral resuscitation in neonatal foals

Cardiovascular or pulmonary system failure in neonatal foals requires rapid recognition and initiation of cardiopulmonary cerebral resuscitation (CPCR). Foals may require resuscitation immediately after birth or after arrest from progression of a disease process such as severe sepsis or septic shock. Initial treatment is aimed at establishing an airway and providing ventilation. Circulation is provided by closed-chest compressions. Circulatory access is important to provide intravenous fluid and pharmacologic therapy for cardiovascular support. Ventricular fibrillation and pulseless ventricular tachycardia are arrhythmias not commonly recognized with arrest in foals, whereas asystole and cardiovascular collapse are frequently encountered. Training of personnel, preparation of supplies, and organization during CPCR is essential to a successful outcome.Most of the information used for CPCR in neonatal foals is derived from human medical research and clinical medicine. As new advances are made in human neonatal and pediatric CPCR, many of these treatments and techniques can be applied to foals. This article reviews currently available CPCR guidelines in foals and highlights new perspectives in human medicine that may be applicable to foals.     

ST segment depression and ventricular fibrillation in a dog after contrast agent administration

An 11-year-old Toy Poodle underwent a computed tomography examination with contrast (iohexol) enhancement under anesthesia. Heart rate and R-wave amplitude on electrocardiogram (ECG) increased 2.5 min after iohexol administration, and end-tidal carbon dioxide decreased to 12 mmHg. A progressive ST segment depression was observed on ECG. Subsequently, the ECG waveform changed to ventricular fibrillation. However, spontaneous circulation returned following cardiopulmonary resuscitation. Myocardial ischemia or anaphylactic shock was suspected in the dog, which explains the ST segment depression observed on ECG. When performing radiological examinations with a contrast agent, the ECG waveform changes, such as an increase in heart rate, R-wave amplitude, or ST segment depression, should be carefully monitored. This might enable early detection of cardiac dysfunction and the ensuing cardiac arrest in dogs.     

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 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.     

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.     

Effects of spontaneous, assisted, and controlled ventilatory modes in halothane-anesthetized geldings

Cardiopulmonary effects of spontaneous, assisted, and controlled ventilatory modes were determined with 6 young, healthy geldings anesthetized with halothane at a constant dose (1.3 minimum alveolar concentration). All horses were in lateral recumbency, and all modes of ventilation were studied at least once during each anesthetic exposure. Cardiac output did not differ between spontaneous and assisted ventilation modes, but both modes were associated with significantly (P less than 0.05) higher cardiac output than that with controlled ventilation. The PaCO2 differed significantly (P less than 0.01) between all modes of ventilation. Although controlled ventilation maintained a normal PaCO2, assisted ventilation reduced PaCO2 as compared with spontaneous ventilation with less cardiovascular depression than that with controlled ventilation. Mixed venous O2 tensions were higher with spontaneous and assisted ventilation modes than with controlled ventilation. Except for shorter inspiratory time and smaller inspiratory/expiratory ratio associated with spontaneous ventilation, there were no ventilatory mode-related effects on ventilatory variables.     

The influence of ventilation mode (spontaneous ventilation, IPPV and PEEP) on cardiopulmonary parameters in sevoflurane anaesthetized dogs

The purpose of this study was to investigate the cardiopulmonary influences of sevoflurane in oxygen at two anaesthetic concentrations (1.5 and 2 MAC) during spontaneous and controlled ventilation in dogs. After premedication with fentany-droperidol (5 microg/kg and 0.25 mg/kg intramuscularly) and induction with propofol (6 mg/kg intravenously) six dogs were anaesthetized for 3 h. Three types of ventilation were compared: spontaneous ventilation (SpV), intermittent positive pressure ventilation (IPPV), and positive end expiratory pressure ventilation (PEEP, 5 cm H2O). Heart rate, haemoglobin oxygen saturation, arterial blood pressures, right atrial and pulmonary arterial pressures, pulmonary capillary wedge pressure and cardiac output were measured. End tidal CO2%, inspiratory oxygen fraction, respiration rate and tidal volume were recorded using a multi-gas analyser and a respirometer. Acid-base and blood gas analyses were performed. Cardiac index, stroke volume, stroke index, systemic and pulmonary vascular resistance, left and right ventricular stroke work index were calculated. Increasing the MAC value during sevoflurane anaesthesia with spontaneous ventilation induced a marked cardiopulmonary depression; on the other hand, heart rate increased significantly, but the increases were not clinically relevant. The influences of artificial respiration on cardiopulmonary parameters during 1.5 MAC sevoflurane anaesthesia were minimal. In contrast, PEEP ventilation during 2 MAC concentration had more pronounced negative influences, especially on right cardiac parameters. In conclusion, at 1.5 MAC, a surgical anaesthesia level, sevoflurane can be used safely in healthy dogs during spontaneous and controlled ventilation (IPPV and PEEP of 5 cm H2O).     

Minimal Anesthetic Concentration and Cardiopulmonary Dose-Response of Halothane in Ducks

The minimal anesthetic concentration (MAC) for halothane and cardiopulmonary dose-responses at several concentrations of halothane were determined during spontaneous ventilation in nine young adult Pekin ducks. The MAC for halothane was 1.04 +/- 0.11 (mean +/- SD). There were dose-dependent decreases in ventilation, significant reductions in inspiratory and expiratory times, and prolongation of expiratory pause times. The end-tidal halothane concentration at apnea in five ducks was less than 1.53% and anesthetic index was less than 1.51. Heart rate increased significantly as the concentration of halothane was increased, but arterial blood pressure did not change. Cardiac arrhythmias developed in five ducks at end-tidal halothane concentrations as low as 1.15%, and one duck died of cardiac arrest.