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.     

Use of pressor therapy in 34 hypotensive critically ill neonatal foals

Background Arginine vasopressin (AVP) is used in human medicine in the management of vasodilatory shock and cardiac arrest, but it is not widely used in equine neonatal intensive care because of concerns about potential side effects and suboptimal efficacy. This retrospective study reports the clinical use of AVP and norepinephrine (NE) in foals with refractory hypotension. Objectives To report the cardiovascular responses and fluid balance in critically ill, hypotensive foals receiving either NE or AVP. Design The medical records of neonatal foals (<7 days of age) from 2000 to 2007 admitted to the Marion duPont Scott Equine Medical Center were reviewed. Results The use of exogenous AVP infusion was associated with a significant increase in mean arterial pressure (MAP) and urinary output, and a significant decrease in heart rate. NE administration was also associated with a significant increase in MAP. Conclusions The findings of this first report of the clinical treatment of foals with refractory hypotension support the use of AVP and NE.     

Plasma aldosterone, vasopressin and atrial natriuretic peptide in hypovolaemia: a preliminary comparative study of neonatal and mature horses

REASON FOR PERFORMING STUDY: Neonatal foals succumb rapidly to hypovolaemic shock in comparison to mature horses; they do not consistently increase their heart rate in response to hypotension and respond differently to fluid administration. The hormonal responses to hypovolaemia in the horse and foal require investigation. HYPOTHESIS: The hormonal responses to hypovolaemia and fluid administration differ between mature and neonatal horses. METHODS: Five mature horses and 5 neonatal foals fulfilling predetermined criteria for hypovolaemia, were included in the study. A blood sample was taken at admission and after normalisation of fluid balance. These were analysed for plasma aldosterone, vasopressin (AVP) and atrial natriuretic peptide (ANP). Normally distributed variables were compared using the Student's t test and nonparametric data using the Mann-Whitney U test. RESULTS: ANP, AVP and aldosterone were higher before fluid resuscitation than after fluid resuscitation in mature horses. Aldosterone was higher before than after fluid resuscitation in foals, and was higher in foals both before and after fluid resuscitation than in mature horses. ANP was lower in mature horses after fluid resuscitation than in foals. No other comparisons were significantly different. CONCLUSIONS: The hormonal responses of the mature and neonatal horses are different during hypovolaemia and following fluid resuscitation. POTENTIAL RELEVANCE: The differences in the hormonal responses to hypovolaemia and fluid resuscitation may be important when considering fluid resuscitation of hypovolaemic horses and foals, and warrants further investigation.     

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.     

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.     

Resuscitation and emergency management for neonatal foals.

Early intervention can dramatically alter outcome in foals. Cardio-pulmonary cerebral resuscitation can be successful and clinically worthwhile when applied to foals that arrest as part of the birthing process. Readily available equipment and an ordered plan starting with addressing the respiratory system (airway and breathing) followed by the circulatory system (circulation and drugs) are the keys to success. Hypoglycemia is common in foals that are not nursing and in septic foals. Support of serum glucose can be an important emergency treatment. Respiratory support with oxygen therapy should be considered in all foals following resuscitation and dystocia. Other foals that are likely to benefit from oxygen are those that are dyspneic, cyanotic, meconium-stained after birth,or recumbent. Emergency therapies, applied correctly, are expected to result in decreased mortality and morbidity.     

Successful cardiopulmonary cerebral resuscitation incorporating defibrillation in a filly with neonatal maladjustment syndrome following a routine anaesthetic procedure

A 10-h-old 56-kg Thoroughbred filly was presented for treatment of partial failure of passive transfer of immunity and presumed neonatal maladjustment syndrome (NMS). The filly was hospitalised, and supportive care initiated. On Day 5 of hospitalisation, seizures were observed and were controlled with IV administration of diazepam. Due to progression of clinical signs of NMS, magnetic resonance imaging of the filly's brain was performed. During the early anaesthetic recovery period, the filly exhibited cardiopulmonary arrest (CPA) at which point cardiopulmonary cerebral resuscitation (CPCR) was performed for a total of 48 min. During this time, ventricular fibrillation (VF) was observed on ECG and the filly was defibrillated three times at 1–2-min intervals using 2–4 J/kg of monophasic electrical defibrillation. The filly successfully recovered from CPCR, was discharged 5 days later and was reported healthy 12 months post-discharge.     

Hypercapnic respiratory acidosis: A protective or harmful strategy for critically ill newborn foals?

This paper reviews both the beneficial and adverse effects of permissive hypercapnic respiratory acidosis in critically ill newborn foals. It has been shown that partial carbon dioxide pressure (PCO₂) above the traditional safe range (hypercapnia), has beneficial effects on the physiology of the respiratory, cardiovascular, and nervous system in neonates. In human neonatal critical care medicine permissive hypercapnic acidosis is generally well-tolerated by patients and is more beneficial to their wellbeing than normal carbon dioxide (CO₂) pressure or normocapnia. Even though adverse effects of hypercapnia have been reported, especially in patients with central nervous system pathology and/or chronic infection, critical care clinicians often artificially increase PCO₂ to take advantage of its positive effects on compromised neonate tissues. This is referred to as therapeutic hypercapnia. Hypercapnic respiratory acidosis is common in critically ill newborn foals and has traditionally been considered as not beneficial. A search of online scientific databases was conducted to survey the literature on the effects of hypercapnia in neonates, with emphasis on newborn foals. The dynamic status of safety levels of PCO₂ and data on the effectiveness of different carbon dioxide levels are not available for newborn foals and should be scientifically determined. Presently, permissive hypercapnia should be implemented or tolerated cautiously in compromised newborn foals and its use should be based on relevant data from adult horses and other species.     

Survey of academic veterinarians' clinical practice in cardiopulmonary–cerebral resuscitation

Objective: To document the clinical practice of cardiopulmonary–cerebral resuscitation (CPCR) among academic veterinarians. Design: Survey. Setting: Eight colleges of veterinary medicine in the United States. Subjects: Two hundred and one academic veterinarians. Interventions: The survey was distributed by hand by the authors into the mailboxes of small animal faculty, residents, and interns. Demographic variables, questions regarding number of cardiopulmonary arrests (CPA) supervised and number successful, do not attempt resuscitation discussions, and Likert‐style questions about client presence during CPCR, appropriateness of CPCR, and CPCR decision‐making were included. Multiple linear regression models were constructed to determine the effect of multiple questions on different target variables of interest. Measurements and main results: Numerous differences were noted based on institution, gender, specialty, and position. Most institutions did not have a standard resuscitation consent form. Most respondents believed the client, house officer, and senior clinician should determine whether to perform resuscitation or not. Quality of life was the most significant determinant of whether to resuscitate or not, followed by long‐term prognosis, then short‐term prognosis. Conclusions: Veterinarians differ in many aspects of their approach to CPA and resuscitation. Creating consensus within the veterinary profession would benefit client service and patient care.     

Arterial lactate concentration, hospital survival, sepsis and SIRS in critically ill neonatal foals

REASONS FOR PERFORMING STUDY: Blood lactate concentration has been shown to be a useful clinical indicator in human patients, but has not been formally investigated in critically ill foals. OBJECTIVE: To investigate the association of blood lactate with hospital survival, markers of cardiovascular status, metabolic acid base status, sepsis and systemic inflammatory response syndrome (SIRS). METHODS: A database containing clinical, haematological, plasma biochemical and hospital outcome data on neonatal foals referred to an intensive care unit in 2000-2001 was analysed. Seventy-two foals for which arterial lactate was measured at admission were included in the study. RESULTS: Sixty-one foals had an admission lactate concentration > 2.5 mmol/l. Admission lactate was statistically associated with hospital survival, mean arterial pressure, blood creatinine concentration, bacteraemia, anion gap, lactate concentration at 18-36 h after admission and evidence of SIRS, but not with packed cell volume or heart rate. Lactate at 18-36 h was also associated with survival and evidence of SIRS. Anion gap, base excess, base excess due to unidentified anions (BEua), simplified strong ion gap or bicarbonate correctly classified foals for presence of hyperlactaemia (> 5 mmol/l) in < or = 80% of animals. CONCLUSIONS: Admission blood lactate gives important prognostic information. Lactate should be measured rather than assumed from the anion gap, base excess, BEua, simplified strong ion gap or bicarbonate. POTENTIAL RELEVANCE: Blood lactate concentrations at admission are clinically relevant in neonatal foals and warrant further investigation. This should include the clinical value of measuring changes in lactate in response to treatment.     

Immunologic Profiles of Peripheral Blood Leukocytes and Serum Immunoglobulin G Concentrations in Perinatal Mares and Neonatal Foals (Heavy Draft Horse)

The purpose of this study was to examine sequential changes in the immunologic parameters of perinatal mares and neonatal foals of the heavy draft horse. Blood samples were collected from clinically healthy pregnant mares and their newborn foals every week from 1 month before the expected foaling date, and 1 hour, 1 day (24-48 hours), and 1, 2, 3, and 4 weeks after foaling. Peripheral blood samples were used to examine total leukocyte counts (n = 20), differential leukocyte counts (n = 20), lymphocyte subpopulations (n = 13), lymphocyte responses to mitogens (n = 10), neutrophil phagocytic function (n = 12), and serum immunoglobulin G (IgG) concentrations (n = 10). In perinatal mares, remarkable changes observed included increased neutrophils, decreased lymphocytes, decreased CD4⁺ T lymphocytes, and decreased lymphocyte responses to mitogens at delivery. These changes were speculated to be the result of physical stress associated with delivery. In neonatal foals, increase in the phagocytic function of neutrophils, and increase in serum IgG concentration after suckling colostrum and increase of lymphocytes accompanied by physiologic growth were observed. Compared to dams, foals showed lower phagocytic function of neutrophils before suckling and fewer lymphocytes and lower lymphocyte responses to mitogens within 1 day after birth. This study revealed immunologic dynamics in perinatal mares and neonatal foals. Immunologic functions are suppressed in foaling mares and are immature in neonatal foals, especially before colostral intake. We expect these data will be useful for further studies in the field of clinical immunology, and preventive medicine.     

The clinical practice of CPCR in small animals: an internet‐based survey

Objective – To characterize the provision of CPCR by small animal veterinarians in clinical practice and to assess how this practice varies among different levels of expertise. Design – Internet‐based survey. Setting – Academia, referral practice, and general practice. Subjects – Six hundred and two small animal veterinarians in clinical practice. Respondents were grouped a priori according to level of expertise: board‐certified (ACVECC, ACVA, ECVAA) specialists; general practitioners in emergency clinics; general practitioners in general practice (GPG). Interventions – Email invitations to the online questionnaire were disseminated via a veterinary internet platform and mailing list server discussion groups. Questions explored respondent characteristics, CPCR preparedness, infrastructural and personnel resources, and techniques of basic and advanced life support. Main Results – In this group of practitioners, the majority (65%) were in general practice. GPG were more likely to perform CPCR <5 times per year and to have 3 or fewer members on their resuscitation team. Most practitioners have a crash cart and drug‐dosing chart available. GPG were less likely to obtain resuscitation codes on their patients, and less likely to use end‐tidal carbon dioxide monitoring or defibrillation. Intubation, oxygen supplementation, vascular access, and external thoracic compressions were widely used, however, GPG were more likely to use lower chest compression rates. Drugs used for CPCR differed among the groups with GPG more likely to use doxapram and glucocorticoids. Conclusions – CPCR is heterogeneously performed in small animal veterinary medicine; differences exist, both among and within different types of veterinarians with varying levels of expertise, in respect to available infrastructure, personnel and CPCR techniques used.     

Serum opsonization capacity, phagocytosis, and oxidative burst activity in neonatal foals in the intensive care unit

BACKGROUND: Phagocytic activity of neonatal foals has been reported to be similar to that of adult horses, but serum opsonization capacity develops with age and may be further altered when opsonins are consumed during infection. HYPOTHESIS: Phagocytosis, oxidative burst activity, and serum opsonization capacity in neonatal foals admitted to an intensive care unit are reduced in comparison with control foals. ANIMALS: Blood samples were collected from hospitalized neonatal foals and from control foals. Hospitalized foals were characterized as sick or septic on the basis of a sepsis score and received intravenous plasma transfusion. METHODS: Phagocytosis, oxidative burst activity, and serum opsonization capacity were tested with flow cytometric analysis. Serum immunoglobulin and complement component 3 concentrations were determined with radial immunodiffusion. Serum amyloid A concentration was assayed with a commercially available solid-phase Sandwich ELISA Kit. Data were analyzed with nonparametric and regression methods. Alpha was set at P = .05. RESULTS: Phagocytic functions of septic and sick foals were lower than control foals in the initial phase of the study (P = .01). Opsonization capacity was significantly higher when bacteria were opsonized with serum from septic (P = .029) and sick (P = .006) foals than from control foals on day 1. Opsonization capacity in septic foals was comparable with control foals on days 2 and 5. This effect was not accompanied by an increase in serum complement C3 or immunoglobulin G concentrations independently. CONCLUSIONS AND CLINICAL IMPORTANCE: Our results suggest that phagocytic function could be decreased in hospitalized foals. The synergistic effect of opsonic elements provided by plasma transfusion may sustain opsonization capacity during sepsis.     

A review of equine sepsis

Sepsis is defined as an exaggerated, systemic inflammatory response to infection and is a common condition in horses. Systemic inflammatory response syndrome (SIRS) associated with bacterial infection is a hallmark of sepsis. Sepsis in neonatal foals is a common sequela of failure of passive transfer and, in addition to development of SIRS, may be characterised by bacteraemia, pneumonia, enterocolitis, omphalophlebitis, meningoencephalitis or arthritis. Sepsis in mature horses is most commonly observed secondary to gastrointestinal lesions that result in disrupted mucosa and bacterial translocation into circulation (endotoxaemia). Pleuropneumonia and metritis may also cause sepsis in mature horses. Diagnosis of sepsis is based on SIRS criteria as well as suspected or confirmed infection. Due to the relatively low sensitivity of microbial culture and the subjectivity of sepsis scoring, many sepsis biomarkers are being studied for their usefulness in diagnosis and prognostication of sepsis in horses. Treatment of sepsis requires an intensive care approach that includes antimicrobial drug administration, fluid resuscitation and pressure support, and treatment for inflammation, endotoxaemia and coagulopathy. Early recognition of sepsis and prompt antimicrobial drug treatment are critical for a successful outcome. Multiple organ dysfunction syndrome may occur in severe cases of sepsis, with common manifestations including laminitis and coagulopathies. Although prognosis for septic mature horses depends highly on the primary disease process, the overall survival rate in septic neonatal foals ranges from 26 to 86%, with most studies indicating a survival rate of 45–60%.     

Detection and effects on platelet function of anti-platelet antibody in mule foals with experimentally induced neonatal alloimmune thrombocytopenia

Horse mares carrying mule foals were immunized during the last trimester of pregnancy with whole acid-citrate-dextrose-anticoagulated donkey blood to experimentally induce neonatal alloimmune thrombocytopenia. Thrombocytopenia occurred in the neonatal mule foals born to immunized horse mares within 24 hours after ingestion of their dams' colostrum. Mule foals born to mares not immunized with donkey blood did not develop thrombocytopenia. These findings suggest that antibodies may have been directed against a donkey platelet antigen present in the mule foals but not present in their dams. The objectives of this study were to determine whether anti-platelet antibody could be detected in mule foals with experimentally induced neonatal alloimmune thrombocytopenia, to identify any platelet proteins recognized by serum antibody in these foals, and to determine if platelet function was altered by sera from these mule foals. An indirect enzyme-linked immunosorbent assay demonstrated significantly higher absorption at 1:200 of platelet-bindable immunoglobulin G in serum from thrombocytopenic mule foals, compared with nonthrombocytopenic mule foals. Sera from thrombocytopenic and nonthrombocytopenic mule foals produced similar binding patterns in western immunoblots with donkey platelet proteins separated on sodium dodecyl sulfate polyacrylamide gels. Maximal platelet aggregation and relative slope of aggregation in response to collagen were significantly inhibited after incubation with sera from thrombocytopenic mule foals. These results suggest that mule foals with induced alloimmune thrombocytopenia have serum antibodies that bind to platelets and may compete with collagen binding sites to impair platelet aggregation.     

Meconium impaction in newborn foals

Meconium impactions are one of the most common causes of colic in neonatal foals. It is recommended that foals be administered a sodium phosphate or warm soapy water enema within the first 3 hours after birth either routinely or if they have not yet passed meconium. Administration of an acetylcysteine retention enema is recommended for foals with refractory cases of meconium impaction.