Nutritional requirements of the critically ill patient

The presence or development of malnutrition during critical illness has been unequivocally associated with increased morbidity and mortality in people. Recognition that malnutrition may similarly affect veterinary patients emphasizes the need to properly address the nutritional requirements of hospitalized dogs and cats. Because of a lack in veterinary studies evaluating the nutritional requirements of critically ill small animals, current recommendations for nutritional support of veterinary patients are based largely on sound clinical judgment and the best information available, including data from experimental animal models and human studies. This, however, should not discourage the veterinary practitioner from implementing nutritional support in critically ill patients. Similar to many supportive measures of critically ill patients, nutritional interventions can have a significant impact on patient morbidity and may even improve survival. The first step of nutritional support is to identify patients most likely to benefit from nutritional intervention. Careful assessment of the patient and appraisal of its nutritional needs provide the basis for a nutritional plan, which includes choosing the optimal route of nutritional support, determining the number of calories to provide, and determining the composition of the diet. Ultimately, the success of the nutritional management of critically ill dogs and cats will depend on close monitoring and frequent reassessment.     

Veterinary intensive care

The term ‘intensive care’ is becoming increasingly popular in veterinary medicine to describe those techniques employed in caring for the critically ill animal. Application of the techniques required for intensive care is not difficult and can be employed in any veterinary practice. The purpose of intensive care is the uncomplicated conversion of a dramatic disease process into an uneventful one, not the performance of life-saving heroics. Critically ill patients share several common features, particularly the need for diligent monitoring and nursing. Regardless of the primary disease, the function of many organs is frequently impaired in these patients and they require total body care. Critically ill animals may have fluid, acid-base and electrolyte imbalances, increased caloric requirements and an increased susceptibility to infection. This paper describes the equipping and staffing of an intensive care unit and the various techniques for monitoring critically ill animals. It also reviews aspects of fluid and electrolyte disturbances and therapy, and the unusual respiratory problems and nutritional requirements of these patients.     

Critical Care Nutrition for Exotic Animals

Exotic animals presented to the veterinary hospital are often malnourished, particularly when ill. Sufficient levels of energy and protein need to be provided for debilitated patients along with important amino acids and vitamin supplementation. For raptor species, a clinical condition described as refeeding syndrome also complicates medical and surgical success. It is important to understand malnutrition and nutritional support to improve treatment outcome of weakened exotic animal patients that are presented to veterinary hospitals. Many of the critical care principles described in this article are derived from mammalian studies.     

Relative adrenal insufficiency in critical illness

Objective: To review the effects of critical illness on hypothalamic–pituitary–adrenal (HPA) function in human and veterinary medicine. Data sources: Data from human and veterinary literature was reviewed. Human data synthesis: Relative adrenal insufficiency (RAI) appears to be common in critically ill human patients with sepsis or septic shock. Hypotension that is refractory to fluid therapy and requires vasopressors is the most common presentation of RAI in the human intensive care unit (ICU). Many investigators now advocate the use of a low‐dose adrenocorticotropin hormone stimulation test to diagnose RAI. It is important to evaluate for the presence of adrenal dysfunction, because current data suggest that treatment with ‘stress’ or low doses of glucocorticoids (200–300 mg hydrocortisone daily) may improve patient outcome in humans. Veterinary data synthesis: There is a paucity of controlled studies in the veterinary literature regarding the effects of critical illness on HPA function. The results of these studies are varied. However, research models of sepsis and hemorrhagic shock suggest the existence of RAI in animals. Prospective clinical studies are needed to further examine pituitary–adrenal response to severe illness in veterinary patients, and to determine if there are therapeutic options, including glucocorticoid administration, which will improve patient outcome in animals. Conclusions: RAI is well documented in critically ill human patients, yet little is known about adrenal dysfunction in veterinary critically ill patients. A small number of studies suggest that RAI may exist in certain subpopulations of veterinary patients. The syndrome of RAI could be considered as a differential diagnosis in seriously ill veterinary patients that fail to respond to appropriate therapy, especially when hypotension refractory to fluid and vasopressor therapy is encountered. This disorder may represent a previously unidentified syndrome in critically ill veterinary patients with important therapeutic implications.     

Neuromuscular Blocking Drugs and the Critical Care Patient

As the management of critically ill and emergency patients intensifies and veterinary surgical procedures become more complex, more sophisticated methods of support are becoming necessary. Emergency and critical care patients are excellent candidates for the use of neuromuscular blocking drugs. The main advantage of the current generation of neuromuscular blocking drugs compared to earlier agents is that they provide muscle relaxation with little or no cardiovascular effects. The pharmacology and physiology of neuromuscular blocking drugs are discussed, and their use is described with specific references to critical care patients. Monitoring techniques are described and reversal of neuromuscular blockade as well as potential side effects and adverse reactions arediscussed.     

Nosocomial infections and antimicrobial resistance in critical care medicine

Objective: To review the human and companion animal veterinary literature on nosocomial infections and antimicrobial drug resistance as they pertain to the critically ill patient. Data sources: Data from human and veterinary sources were reviewed using PubMed and CAB. Human data synthesis: There is a large amount of published data on nosocomially‐acquired bloodstream infections, pneumonia, urinary tract infections and surgical site infections, and strategies to minimize the frequency of these infections, in human medicine. Nosocomial infections caused by multi‐drug‐resistant (MDR) pathogens are a leading cause of increased patient morbidity and mortality, medical treatment costs, and prolonged hospital stay. Epidemiology and risk factor analyses have shown that the major risk factor for the development of antimicrobial resistance in critically ill human patients is heavy antibiotic usage. Veterinary data synthesis: There is a paucity of information on the development of antimicrobial drug resistance and nosocomially‐acquired infections in critically ill small animal veterinary patients. Mechanisms of antimicrobial drug resistance are universal, although the selection effects created by antibiotic usage may be less significant in veterinary patients. Future studies on the development of antimicrobial drug resistance in critically ill animals may benefit from research that has been conducted in humans. Conclusions: Antimicrobial use in critically ill patients selects for antimicrobial drug resistance and MDR nosocomial pathogens. The choice of antimicrobials should be prudent and based on regular surveillance studies and accurate microbiological diagnostics. Antimicrobial drug resistance is becoming an increasing problem in veterinary medicine, particularly in the critical care setting, and institution‐specific strategies should be developed to prevent the emergence of MDR infections. The collation of data from tertiary‐care veterinary hospitals may identify trends in antimicrobial drug resistance patterns in nosocomial pathogens and aid in formulating guidelines for antimicrobial use.     

Successful treatment of acute respiratory distress syndrome in 2 dogs

Acute respiratory distress syndrome (ARDS) was diagnosed in 2 dogs with acute dyspnea. Short-term positive pressure ventilation and intense critical and nursing care were provided. Both dogs improved and were discharged. Few reports describe successful recovery from ARDS. Due to advances in positive pressure ventilation and improvement in the supportive care of critically ill veterinary patients, the prognosis for ARDS may improve.     

Transfusion medicine in veterinary emergency and critical care medicine

Transfusion medicine is a vital part of veterinary emergency and critical care medicine. The goals of this article are to review blood banking and the transfusion principles surrounding care of the critically ill or injured small animal, to highlight the differences in emergency/critical care transfusions compared with standard transfusion medicine, and to discuss traumatic blood loss and sepsis as unique entities in emergency and critical medicine.     

Blood gas analysis.

Evaluation of both arterial and central venous blood can be valuable in monitoring the critically ill veterinary patient. The traditional approach, which concentrates on arterial blood analysis only, may miss important aspects of oxygen delivery to tissues, especially in patients with poor perfusion. The advances that have resulted in affordable bedside blood gas analyzers have created a clinical situation in which blood gas analysis should be an integral part of critical care monitoring. Following basic principles of interpretation, blood gas analysis, which has traditionally been viewed as a complex method of monitoring, should become more useful. Assessing both the arterial and central venous samples should result in more efficient and higher quality care for veterinary patients.     

Lactate Kinetics in veterinary Critical Care: A Review

Elevation in blood lactate concentration, with or without accompanying metabolic acidosis, is a hallmark finding in patients with circulatory compromise, and is also consistently noted in other conditions affecting critically ill or injured individuals. Little is reported in a veterinary literature regarding lactate measurement in the emergency and critical care setting, despite impressive reports of the clinical usefulness of lactate measurement in people. The purpose of this article is to review lactate kinetics and the clinical utility of lactate measurement. Limitations to lactate evaluation will also be discussed.     

Nutritional plan: matching diet to disease

Institution of appropriate, timely nutritional support in the anorexic or critically ill patient has become accepted medical practice in people and animals. This article focuses on the benefits of appropriate nutrient intake in critically ill animals, recommended nutrient requirements for dogs and cats receiving enteral feeding, and mechanics of food preparation and delivery for a variety of feeding tubes. General nutrient requirements for all patients, specific recommendations for certain illnesses such as renal failure, pancreatitis, and hepatic disease, and nutritional alterations for critical illness are reviewed. Commercial liquid diets manufactured for people and pets, and pet-food diets practical for formulation of gruel are presented. Institution of and weaning from feeding are explained.     

Controversies related to red blood cell transfusion in critically ill patients

Objective – To review the evolution of and controversies associated with allogenic blood transfusion in critically ill patients. Data sources – Veterinary and human literature review. Human Data Synthesis – RBC transfusion practices for ICU patients have come under scrutiny in the last 2 decades. Human trials have demonstrated relative tolerance to severe, euvolemic anemia and a significant outcome advantage following implementation of more restricted transfusion therapy. Investigators question the ability of RBCs stored longer than 2 weeks to improve tissue oxygenation, and theorize that both age and proinflammatory or immunomodulating effects of transfused cells may limit efficacy and contribute to increased patient morbidity and mortality. Also controversial is the ability of pre‐ and post‐storage leukoreduction of RBCs to mitigate adverse transfusion‐related events. Veterinary Data Synthesis – While there are several studies evaluating the transfusion trigger, the RBC storage lesion and transfusion‐related immunomodulation in experimental animal models, there is little research pertaining to clinical veterinary patients. Conclusions – RBC transfusion is unequivocally indicated for treatment of anemic hypoxia. However, critical hemoglobin or Hct below which all critically ill patients require transfusion has not been established and there are inherent risks associated with allogenic blood transfusion. Clinical trials designed to evaluate the effects of RBC age and leukoreduction on veterinary patient outcome are warranted. Implementation of evidence‐based transfusion guidelines and consideration of alternatives to allogenic blood transfusion are advisable.     

Hypocalcemia in a critically ill patient

Objective: To present a case of clinical hypocalcemia in a critically ill septic dog. Case summary: A 12‐year old, female spayed English sheepdog presented in septic shock 5 days following hemilaminectomy surgery. Streptococcus canis was cultured from the incision site. Seven days after surgery, muscle tremors were noted and a subsequent low serum ionized calcium level was measured and treated. Intensive monitoring, fluid therapy, and antibiotic treatment were continued because of the sepsis and hypocalcemia, but the dog was euthanized 2 weeks after surgery. New or unique information provided: Low serum ionized calcium levels are a common finding in critically ill human patients, especially in cases of sepsis, pancreatitis, and rhabdomyolysis. In veterinary patients, sepsis or streptococcal infections are not commonly thought of as a contributing factor for hypocalcemia. Potential mechanisms of low serum ionized calcium levels in critically ill patients include intracellular accumulation of calcium ions, altered sensitivity and function of the parathyroid gland, alterations in Vitamin D levels or activity, renal loss of calcium, and severe hypomagnesemia. Pro‐inflammatory cytokines and calcitonin have also been proposed to contribute to low ionized calcium in the critically ill. Many veterinarians rely on total calcium levels instead of serum ionized calcium levels to assess critical patients and may be missing the development of hypocalcemia. Serum ionized calcium levels are recommended over total calcium levels to evaluate critically ill veterinary patients.     

Peroxidative protection of parenteral admixture by D-alpha-tocopherol

High lipid:low dextrose (HL:LD) parenteral admixtures (PAs) are becoming commonplace in the nutritional support of veterinary patients. Lipid peroxidation before administration appears to be an unwanted sequela of high lipid content in PAs that can lead to oxidative injury of biologic membranes in vivo. The purpose of this in vitro study was to measure hydroperoxides in HL:LD PAs and to determine the optimal dose of d-alpha-tocopherol to minimize peroxidation in these PAs during a 24-hr period. Detectable concentrations of hydroperoxides were present in all PAs. D-alpha-tocopherol appeared to significantly minimize peroxidation of HL:LD PAs in vitro. These results have clinical implications for parenteral feeding in critically ill patients.     

Application of Airway Pressure Therapy in Veterinary Critical Care: Part I: Respiratory Mechanics and Hypoxemia

Over the past several decades, recognition of acute respiratory failure as the cause of death in patients suffering from various clinical conditions has prompted aggressiv investigation into the area of respiratory physiology and supportive respiratory care. With the evolution of emergency medicine and critical care services in both human and veterinary medicine, many patients previously considered unsalvageable due to the severity of their underlying disease are now being resuscitated and successfully supported, creating a new population of critically ill patients. Where only a decade ago these patients would have succumbed to their underlying disease, they now survive long enough to manifest the complications of shock and tissue injury in the form of acute respiratory failure. Investigation into the pathophysiology and treatment of this acute respiratory distress syndrom (ARDS) has facilitated increased clinical application of respiratory theerapy and machanical ventilation.¹ The purpose of this paper is to provide a basic review of respiratory mechanics and the pathophysiology of hypoxemia as they relate to airway pressure therapy in veterinary patients and to review the use of airway pressure therapy in veterinary patients This paper is divided into two parts; part I reviews respiratory mechanics and hypoxemia as they apply to respiratory therapy, while part II deals specifically with airway pressure therapy andits use in clinical cases.     

Diet‐associated hepatic failure and immune‐mediated hemolytic anemia in a Weimaraner

Objective: To describe the medical and nutritional management of a 4‐year‐old Weimaraner with acute hepatic failure and immune‐mediated hemolytic anemia (IMHA) associated with consuming a commercial dog food. Case summary: A 4‐year‐old male castrated Weimaraner developed signs of IMHA, hepatic failure, disseminated intravascular coagulopathy, and malnutrition after consuming a commercial dog food. During the course of hospitalization, medical management included immunosuppressive therapy and supportive care. Nutritional support consisted of both enteral and parenteral nutrition. The dog was discharged after 19 days of hospitalization and fully recovered by 6 months. An investigation by the Food and Drug Administration was not able to determine the exact cause of the acute hepatic failure and IMHA. New information provided: This is the first case report documenting the medical and nutritional management of a critically ill animal associated with ingestion of this commercial dog food.     

Nitric Oxide Response in Critically III Dogs

Alterations in nitric oxide (NO)production may play a role in critical illness. Total serum nitrate/nitrite concentrations [SNN (uM/L)], the stable metabolites of NO, have been used as an indirect measure of NO in people, with increased concentrations reported in cases of critical illness. The relationship of nitric oxide (NO) to criticalillness in dgos is unknown. We tested the hypothesis that critically ill intensive care unit (ICU) canine illness in dogs is unknown. We tested the hypothesis that critically ill intesive care unit (ICU) canine patients would have increased SNN as compared to healthy dogs and non-critically ill dogs. An organ failure index score (OFI) was assigned to dogs admitted to the ICU to evaluate trends between disease severtiy and SNN. Critically ill dogs had significantly (p < 0.05) higher SNN (median 10.53) as compared to non-critically ill dogs (median 2.3) and healthy dogs (median 1.92). Critically ill dogs with the most severe disease (as based on OFI) had higher SNN concentrations. Survival of critically ill dogs with SNN of > 15 upon ICU admission (12% survival) was significantly less than survival of critically ill dogs with SNN ≤ 15 (91%) survival).l (Vet. Emerg. & Crit. Care, 9: 195–202, 1999)     

Lactate: physiology and clinical utility

Objective: To review the physiology of lactate production and metabolism, the causes of lactic acidosis, and the current applications of lactate monitoring in humans and animals. Data sources: Human and veterinary studies. Summary: Lactate production is the result of anaerobic metabolism. Tissue hypoxia due to hypoperfusion is the most common cause of lactic acidosis. Studies in critically ill humans have shown that serial lactate monitoring can be used to assess the severity of illness and response to therapy. Several veterinary studies have also shown lactate as a useful tool to assess severity of illness. Conclusions: Lactate measurement in critically ill veterinary patients is practical and can provide information to assess severity of illness. Further veterinary studies are needed to establish the value of serial lactate measurements for prognostic and therapeutic purposes. Information regarding lactate measurement in cats is limited, and further studies are warranted.     

Intermittent and Continuous Enteral Nutrition in Critically Ill Dogs: A Prospective Randomized Trial

Background: Malnutrition is a common problem in critically ill dogs and is associated with increased morbidity and mortality in human medicine. Enteral nutrition (EN) delivery methods have been evaluated in humans to determine which is most effective in achieving caloric goals. Objectives: To compare continuous infusion and intermittent bolus feeding of EN in dogs admitted to a critical care unit. Animals: Fifty‐four dogs admitted to the critical care unit and requiring nutritional support with a nasoenteric feeding tube. Methods: Prospective randomized clinical trial. Dogs were randomized to receive either continuous infusion (Group C) or intermittent bolus feeding (Group I) of liquid EN. The percentage of prescribed nutrition delivered (PPND) was calculated every 24 hours. Frequencies of gastrointestinal (GI), mechanical, and technical complications were recorded and gastric residual volumes (GRVs) were measured. Results: PPND was significantly lower in Group C (98.4%) than Group I (100%). There was no significant difference in GI or mechanical complications, although Group C had a significantly higher rate of technical complications. GRVs did not differ significantly between Group C (3.1 mL/kg) and Group I (6.3 mL/kg) and were not correlated with the incidence of vomiting or regurgitation. Conclusions and Clinical Importance: There was a statistically significant difference in the PPND between continuously and intermittently fed dogs, but this difference is unlikely to be clinically relevant. Critically ill dogs can be successfully supported with either continuous infusion or intermittent bolus feeding of EN with few complications. Increased GRVs may not warrant termination of enteral feeding.