Managing the critical care patient can be challenging, and successful outcomes require careful attention to both the medical and nutritional aspects of patient care. The goal of this presentation is to review principles underlying optimal treatment for critically ill dogs and cats in a case-based approach.
Medical Management
Triage
The triage exam is an abbreviated, repeatable systematic exam of the following key body systems: pulmonary, cardiovascular, and neurologic. It is designed to rapidly assess the stability of the patient, determine if immediate lifesaving interventions are necessary, and prioritize the need for medical attention. Often there will be an overlap between the triage examination, emergency diagnostics, and resuscitative therapies depending on the state of the animal.
Serial triage examinations are important to ensure the animal remains stable. The frequency of repeat examinations will depend on the initial triage findings, reason for presentation, and the risk for deterioration. For example, a dog that presents as a hit-by-car that is initially stable should have the triage exam repeated every 20–30 minutes until a complete thorough examination can be performed, or sooner if a change in condition is noted.
Following stabilization, the patient should be examined more thoroughly and monitoring continued in order to detect further injuries, assess response to initial therapy, alert the clinician to a possible change or deterioration in the patient's status.
Minimum Emergency Data Base (MEDB)
Deciding which emergency point of care tests to perform in the first 5 minutes of patient arrival can have a very big impact on the chances of survival. However, do not transport unstable patients out of the treatment area/ICU. Bring the diagnostics and therapies to the patient if at all possible!
Although variation exists regarding what should be included in the MEDB, it should at least include the haematocrit, total solids, blood urea nitrogen, glucose, and often lactate. Additional emergency point of care tests should be performed depending on the initial triage exam and results of the MEDB, and may include any of the following: ECG, blood pressure, pulse oximetry, arterial blood gas, emergency point of care ultrasound (AFAST and TFAST exams), blood smear, slide agglutination, urine dipstick, and urine specific gravity.
Serial MEDB readings often provide more information than a single measurement.
Treatment Priorities in Emergency and Critical Care Patients
Stabilization therapies and emergency diagnostics should be initiated the second the patient arrives in the ICU! Barring the arrested patient, there is no "cookbook recipe" for emergency and critical care patients, and every patient must be evaluated individually. The decision of what therapies to institute will vary depending on the condition of the animal, underlying cause, and the willingness and financial status of the owner.
The following, however, is a general list of important factors to consider in unstable emergency patients. Often these interventions are implemented simultaneously or may be altered slightly depending on the initial triage exam findings and patient status.
1. Immediately transport unstable patients to an ICU/emergency stabilization area.
2. Unless the animal is in extreme respiratory distress (stress or restraint will kill the patient), an intravenous catheter is a priority.
3. Use minimum emergency data base and other emergency point of care diagnostics/tests (do not transport patient away from the treatment/ICU area) to help guide stabilization/initial therapy.
4. Consider pre-fluid sampling of blood and urine if possible (do not unduly stress the patient and stabilization take priority)!
5. Unstable patients should be administered oxygen until the underlying cause can be determined or the oxygen saturation/pressure can be evaluated.
6. Fluid resuscitation: Hypovolemia/hypoperfusion should be treated aggressively unless there is cardiogenic shock, pulmonary edema, neurologic edema or acute anuric renal failure. This may require transfusion products as well as crystalloids and synthetic colloids.
7. Analgesia: Many emergency patients present with very painful conditions, and analgesia is a critical component of their management.
Once the patient is stable, there are a number of factors that should be assessed to help optimize daily patient care and outcome (Dr Kirby's rule of 20).
1. Fluid balance: What are the fluid losses? Consider all ins and outs. What is the balance over 24 h (What should it be)?
2. Oncotic pull: What are the consequences of decreased oncotic pressure? How do we identify it in our patients and how do we treat it?
3. Glucose: What is the significance of hyper- and hypoglycemia? Should it be corrected if high?
4. Electrolytes (calcium, sodium, chloride, potassium, phosphorus, magnesium): When are they a concern? How are they treated if high or low?
5. Oxygenation and ventilation: What is the difference, why is it important, how do we assess them, and when do we treat?
6. Level of consciousness and mentation: How should level of consciousness be assessed? What emergency interventions can be considered?
7. Blood pressure: How is this measured? What are the normal values? How are they corrected if low or high?
8. Heart rate, rhythm and contractility: How is this assessed clinically? What are the concerns with tachycardia, bradycardia and how are arrhythmias addressed?
9. Albumin: What is the role of albumin, and what are the considerations to correct it?
10. Coagulation: How does one look for coagulopathies (hypo or hyper)? What are the options for therapy?
11. Red blood cell/hemoglobin concentration: What are the indications for transfusion?
12. Renal function: What is considered normal and how should it be monitored?
13. Immune status, antibiotic dosage and selection, WBC count: How does illness effect immune function and when are antibiotics indicated? What is the significance of a change in WBC count?
14. GI motility and mucosal integrity: How might this be assessed? What are the treatment options? What impact does it have on patient outcome if any?
15. Drug dosage and metabolism: What factors of illness will impact dosage and metabolism of drugs?
16. Nutrition: See section Nutritional Management below
17. Pain control: How do you know it is adequate?
18. Nursing care and patient mobilization: Why is this important?
19. Wound/bandage care: How often and what is being assessed?
20. Tender loving care
Serial patient assessments over time often provide more information than a single assessment.
Nutritional Management
Why Feed the Hospitalized Patient?
Adequate intake of calories and other nutrients is critical for the optimal care of hospitalized patients. A healthy animal that does not get enough calories will lose primarily fat if not provided with sufficient calories. In contrast, a sick or injured animal will lose lean body mass when it is not given adequate calories. This loss of lean body mass impairs the animal's strength, immune function, wound healing, and overall survival. When oral intake is not sufficient, nutritional support techniques are then needed to provide some or all of the nutrient requirements. The optimal feeding route depends upon a number of patient-dependent issues, including the function of the GI tract, the patient's ability to tolerate tube placement, and risk of aspiration, as well as non-patient issues such as cost and technical expertise and support.
Assessing the Patient
A nutritional assessment should be performed in every patient. Not only does this assessment help to identify whether the usual diet is optimal for ongoing management of the patient, it also helps to identify issues that could be contributing to the underlying disease (e.g., a nutritionally unbalanced diet, a contaminated raw meat diet, dietary supplement side effects, or diet-induced toxicities [e.g., as in acute kidney injury caused by chicken jerky treats]). It also can identify an individual animal's food preferences, which can be helpful for feeding them during hospitalization.
The World Small Animal Veterinary Association (WSAVA) has developed nutritional assessment guidelines, as well as a nutrition toolkit to facilitate this assessment. An assessment is comprised of a short screening, and if any concerns are identified, a more thorough nutritional assessment is indicated. The basic components of the screening are body weight, body condition score, muscle condition score, and diet history (which includes the pet food, treats, table food, rawhides, dietary supplements, and foods used to administer medications).
Developing the Plan
Who to Feed
Patients should be hemodynamically stable before nutritional intervention is initiated. Every patient in whom feeding is not contraindicated needs precise written feeding orders, which should include route, diet, amount, and frequency (e.g., Feed Diet X orally - ½ can TID).
When to Feed
Assisted feeding techniques should be instituted in patients that have had inadequate food intake for longer than 3–5 days. Remember that this 3–5 day timeline includes the duration of inadequate food intake at home before admission to the hospital. Also, if an animal is going to be anesthetized for diagnostic or therapeutic procedures, take the opportunity to place a feeding tube if there is any indication that one may be needed.
Where to Feed
The optimal feeding route depends upon a number of patient-dependent issues, including the function of the GI tract, the patient's ability to tolerate tube placement, and risk of aspiration, as well as non-patient issues, such as cost and technical expertise (see WSAVA Feeding Guide for Hospitalized Dogs and Cats). Whenever possible, the enteral route should be used, because it is the safest, most convenient, most physiologically sound, and least expensive method of nutritional support. Nasogastric/nasoesophageal tubes for short-term use or gastrostomy or esophagostomy or gastrostomy tubes (for long-term use) are excellent options for animals unable or unwilling to eat adequate amounts voluntarily. When patients are unable to tolerate enteral feeding, parenteral (intravenous) nutrition should be considered.
What to Feed
Diet choice depends on patient factors such as concurrent medical conditions which impact the desired nutrient profile, and non-patient factors such as the type of tube in place, diet availability, and cost. Nasogastric and jejunostomy tubes require veterinary liquid diets (e.g., CliniCare). Esophagostomy and gastrostomy tubes, because of their larger size, allow use of a wider variety of diets although veterinary "critical care" diets are typically used as the first choice for most animals with these large tubes (e.g., Iams canine/feline Maximum Calorie [High Calorie], Hill's a/d, Royal Canine Recovery RS). Animals with specialized needs (e.g., a low fat or reduced protein diet) can be fed with blenderized veterinary therapeutic pet foods.
How Much to Feed
Resting energy requirement (RER) should be the initial caloric goal for hospitalized patients. RER can be calculated with the following formulas:
70 x (weight in kg)0.75 or
For patients between 3–25 kg: (30 x weight in kg) + 70
A chart listing RER for different body weight can be a useful tool for quick and easy reference for hospitalized patients (see WSAVA Nutrition Toolkit).
Patient Monitoring
Daily patient assessment is a critical component of the overall nutrition plan. The prior day's feeding orders should be reviewed to determine if the caloric goal was met. The route of nutrient delivery should be reviewed to determine if this needs adjustment. For example, if a patient has not consumed adequate food via coax feeding, is it time to place a feeding tube? Look for trends in body weight and monitor appropriate laboratory tests based on disease condition. Note any adverse events associated with eating, including gastrointestinal issues, metabolic changes such as electrolyte shifts, or mechanical issues associated with a feeding tube. Based on the patient's tolerance of the past feeding orders and the changing status of the disease condition, new feeding orders can be written for the coming day.
References
1. Chan DL, Freeman LM. Parenteral nutrition. In: Dibartola SP, ed. Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. 4th ed. St. Louis, MO: Elsevier; 2012:605–622.
2. Larsen JA. Enteral nutrition and tube feeding. In: Fascetti AJ, Delaney SJ, eds. Applied Veterinary Clinical Nutrition. West Sussex, UK: Wiley-Blackwell; 2012:329–352.
3. Marks SL. Nasoesophageal, esophagostomy, gastrostomy, and jejunal tube placement techniques. In: Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine. 7th ed. St. Louis, MO: Saunders; 2010:333–340.
4. WSAVA Global Nutrition Committee. WSAVA nutrition toolkit: www.wsava.org/nutrition-toolkit (body and muscle condition score charts, feeding guidelines, effective internet use for owners, diet history forms, calorie requirements for dogs and cats, in-hospital feeding plans, recommendations for selecting a pet food, etc.).
5. Andrew Linklater. Rule of 20. In: Aiello, Moses, eds. The Merck Veterinary Manual. www.merckmanuals.com/vet/emergency_medicine_and_critical_care/monitoring_the_critically_ill_animal/the_rule_of_20.html.
6. Pachtinger G. Monitoring of the emergent small animal patient. Vet Clin North Am Small Anim Pract. 2013;43:705–720.
7. Butler AL. Goal-directed therapy in small animal critical illness. Vet Clin North Am Small Anim Pract. 2011;41:817–838.