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.     

Nutrition in critical illness.

Malnutrition associated with critical illness has been unequivocally associated with increased morbidity and mortality in humans. Because malnutrition may similarly affect veterinary patients, the nutritional requirements of hospitalized critically ill animals must be properly addressed. Proper nutritional support is increasingly being recognized as an important therapeutic intervention in the care of critically ill patients. The current focus of veterinary critical care nutrition, and the major focus of this article, is on carefully selecting the patients most likely to benefit from nutritional support, deciding when to intervene, and optimizing nutritional support to individual patients.     

Measurement of plasma colloid osmotic pressure in neonatal foals under intensive care: comparison of direct and indirect methods and the association of COP with selected clinical and clinicopathologic variables

Objectives: To describe and compare admission colloid osmotic pressure (COP) measurement using both direct and indirect methods in neonatal foals under intensive care, and to evaluate for associations between COP and clinical/clinicopathologic parameters. Design: Prospective study. Setting: Intensive care unit at a veterinary medical teaching hospital. Animals: Twenty‐six critically ill neonatal foals were studied. A control group consisted of 9 clinically healthy neonatal foals. Interventions: Clinicopathologic data were collected at the time of admission. COP was measured directly using a colloid osmometer. Indirect COP was calculated using equations by both Landis–Pappenheimer (L–P) and Thomas and Brown. Measurements and main results: Measured admission COP values were 17.1±4.3 and 17.7±2.4 mmHg in critically ill and control foals, respectively, and these values were not significantly different. Critically ill foals with blood lactate concentrations >3 mmol/L had lower COP values than those with lactate ≤3 mmol/L. There was close agreement between indirect COP values calculated using the L–P equation and direct COP values measured in control foals (mean error=0.0±1.3 mmHg; R²=0.87). However, indirect values were not as predictive of direct COP in critically ill foals (mean error=0.8±3.8 mmHg; R²=0.64). As COP values increased, the indirect method tended to overestimate COP, whereas at lower values it slightly underestimated COP. Conclusion: While the L–P equation was a close approximation of direct COP in healthy foals, direct measurements of oncotic pressure cannot be replaced for monitoring of critically ill foals. Critically ill foals with higher lactate concentrations had lower COP values, suggesting a possible relationship between COP and lactate.     

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.     

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)     

Analgesia and sedation in the critically ill

Objective: To summarize the challenges to recognizing pain in critically ill patients, the rationale for treatment even in the absence of signs of pain, and the therapeutic options available in the intensive care environment. Etiology: Pain is one of many stressors challenging the critically ill patient, and may in turn be multifactorial in nature. Common causes include local and systemic inflammation, injuries, diagnostic and therapeutic procedures, immobilization, and thrombosis. Diagnosis: Critically ill animals with pain may not demonstrate overt behavioral or physiologic signs of distress. Therefore, pain must be assumed to be present for animals whose condition puts them at risk. Therapy: Currently available analgesic and sedative drugs and methods of delivery are described. Several useful analgesics and sedatives may be co‐administered as fluid additives to provide continuous therapy. Prognosis: There is growing evidence that the neuroendocrine stress response to severe injury or illness may become sufficiently intense to contribute to morbidity and mortality. Many therapeutic analgesic and sedation options provide good control of pain and stress, and in some circumstances this may improve the outcome of critical illness.     

Ionized Hypocalcemia in Critically Ill Dogs

Background: Ionized hypocalcemia (iHCa) is a common electrolyte disturbance in critically ill people, especially those with sepsis. The cause of the iHCa is not entirely understood and is likely multifactorial. Critically ill people with iHCa have longer hospital stays and higher mortality rates compared to people with normocalcemia. There are no published clinical studies evaluating the incidence and impact of iHCa in critically ill dogs.
Hypothesis: iHCa occurs in critically ill dogs, is more prevalent in dogs with systemic inflammatory response syndrome (SIRS) or sepsis, and is associated with longer hospital stays and higher mortality.
Animals: One hundred and forty-one client-owned dogs admitted to a companion animal intensive care unit (ICU) in a veterinary teaching hospital.
Methods: Prospective observational study of sequentially enrolled dogs. Blood was collected and analyzed within an hour of admission from all dogs presented to the ICU that met study inclusion criteria.
Results: The incidence of iHCa (iCa < 1.11 mmol/L) was 16%. The presence of iHCa was associated with longer ICU ( P = .038) and hospital ( P = .012) stays but not with decreased survival ( P = .60). Dogs with sepsis as defined by ≥3 SIRS criteria and a positive culture were more likely to have iHCa ( P = .050).
Conclusions and Clinical Relevance: In dogs not previously treated with fluids or blood products intravenously, the finding of iHCa upon admission to the ICU predicted a longer duration of ICU and hospital stay. Septic dogs with positive cultures were more likely to have iHCa.     

Fluid and electrolyte balance in critical patients

Recognition and appropriate management of fluid and electrolyte disorders in critical patients is extremely important. In many cases, these secondary problems are more complicated and more serious than the initiating disease process. A severely ill diabetic patient, for example, is more likely to die from dehydration, hyperosmolality, metabolic acidosis, hypokalemia or hypophosphatemia than from hyperglycemia or lack of insulin therapy. Proper fluid therapy and treatment of electrolyte abnormalities make a major difference in the survival rate of critically ill animals.     

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.     

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.     

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.     

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.     

Anesthesia of the critically ill equine patient.

There is a plethora of information regarding anesthetic management of horses; however, controlled studies of the critically ill equine patient are few.These patients should be managed like any equine anesthetic candidate but much more stringently:I. Preoperative evaluation and appropriate therapy may represent the difference between life and death during the intraoperative and recovery periods. 2. The anesthetic induction and maintenance protocol should be based on the individual situation of the veterinary facility and personnel("comfort zone"). 3. Appropriate monitoring and intraoperative supportive measures are essential. 4. The anesthetic period is a significant perturbation to homeostasis. Even if the horse seems to have done well (ie, as indicated by the cardiopulmonary values), a problem-free anesthetic period does not guarantee a successful recovery, and close monitoring should continue until the horse is ambulatory. 5. Critically ill patients are often in a negative energy balance. Supportive measures to ensure an adequate caloric intake, such as enteral or parenteral nutrition, facilitate healing and return of homeostasis.     

Serum concentrations of monocyte chemoattractant protein‐1 in healthy and critically ill dogs

Background: The chemokine monocyte chemoattractant protein‐1 (MCP‐1) is a primary regulator of monocyte mobilization from bone marrow, and increased concentrations of MCP‐1 have been associated with sepsis and other inflammatory disorders in critically ill people. The relationship between MCP‐1 and disease in dogs has not been evaluated previously. Objective: The purpose of this study was to assess serum concentrations of MCP‐1 in healthy dogs, dogs in the postoperative period, and critically ill dogs. We hypothesized that MCP‐1 concentrations would be significantly increased in critically ill dogs compared with postoperative or healthy dogs. Methods: Serum concentrations of MCP‐1 were measured in 26 healthy control dogs, 35 postoperative dogs, and 26 critically ill dogs. Critically ill dogs were further subgrouped into dogs with sepsis, parvovirus gastroenteritis, immune‐mediated hemolytic anemia, and severe trauma (n=26). MCP‐1 concentrations were determined using a commercial canine MCP‐1 ELISA. Associations between MCP‐1 concentrations and disease status were evaluated statistically. Results: MCP‐1 concentration was significantly higher in critically ill dogs (median 578 pg/mL, range 144.7–1723 pg/mL) compared with healthy dogs (median 144 pg/mL, range 4.2–266.8 pg/mL) and postoperative dogs (median 160 pg/mL, range 12.6–560.4 pg/mL) (P<.001). All subgroups of critically ill dogs had increased MCP‐1 concentrations with the highest concentrations occurring in dogs with sepsis. However, differences among the 4 subgroups were not statistically significant. Conclusion: Critically ill dogs had markedly increased serum concentrations of MCP‐1 compared with postoperative and healthy dogs. These results indicate that surgery alone is not sufficient to increase MCP‐1 concentrations; thus, measurement of MCP‐1 may be useful in assessing disease severity in critically ill dogs.     

Monitoring the critically ill equine patient.

Measurements of physiologic parameters, such as blood pressure or lactate concentration, are useful to detect occult derangements, such as tissue hypoxia and dysoxia. These tools are also useful in determining the effects of therapy. Monitoring techniques are now widely available for the intensive management of critically ill horses and foals. A number of these have evolved into noninvasive or minimally invasive devices and procedures and provide information that can be used for earlier and more dynamic therapeutic intervention. The goal of increased monitoring is to improve the level of care in the ICU; L ultimately. increased survival of critical patients is the motivation behind enhanced monitoring of physiology, with particular attention being paid to trends or alterations over time. This review highlights practical and informative monitoring tools and techniques and provides normal reference values from the literature.     

Critical care of pet birds. Procedures, therapeutics, and patient support.

Critically ill birds must be recognized, accurately assessed, and provided rapid appropriate treatment. This article presents a method of assessment and supportive care for critically ill birds. A problem-oriented approach based on clinical signs is presented, accompanied by suggested diagnostic tests. Techniques used to treat critically ill birds are also discussed.     

Complications of fluid therapy.

The intravenous administration of fluids is one of the most important aspects of patient care in hospitalized animals. Intravenous fluids are administered to replace or prevent dehydration, treat hypovolemic shock and intravascular volume depletion, correct acid-base and electrolyte abnormalities, and maintain vascular access for administration of drugs, blood product components, and parenteral nutrition. Intravenous catheterization also can provide a means of blood sample collection, thus avoiding frequent and uncomfortable venipunctures in critically ill animals. Although the benefits of intravenous catheterization and fluid administration are numerous, inherent risks are associated with the procedures, and care must be taken to avoid potential complications.     

Perspectives of clinical osmometry

Several clinical applications of osmometry have been reviewed. Questions remain concerning the clinical acceptance that osmometry will achieve in veterinary medicine. Many practices may not be able to justify the purchase of an osmometer; however, osmometers are available at most medical centers and clinical laboratories. In an era when serum chemistry profiles are being used more frequently, it may prove that serum osmolatity will be requested more frequently. Determination of osmolality is a simple, rapid, and inexpensive test that has potential in screening for disorders of body fluids. Several research laboratories utilize osmometry routinely in screening for potential fluid or electrolyte inbalances. When coupled with glucose, blood urea nitrogen, and electrolyte values, a comparison of calculated and measured osmolality allows further clinical interpretations. Differences may exist between calculated and measured osmolality. In some instances, determination of calculated osmolality alone may lead to erroneous conclusions concerning the true status of body fluids. Specialized intensive care practices should certainly consider the value of osmometry in monitoring patients undergoing extensive fluid therapy. Last, but not least, osmometry does provide the best measure of renal concentrating ability and is of particular value in evaluation of polyuric and proteinuric patients.