Wednesday, May 13, 2009

Critical care nutrition - what to expect if your pet is hospitalized?

None of us want to consider the eventuality that our pets may develop some sort of critical illness requiring hospitalization. If it does happen, we want to be sure that the critical care being provided is the best it can be. One sign that this is the case is when the attending clinician demonstrates an eye to nutrition from the first days of hospitalization.

Active nutrition therapy is known to preserve normal immune function, attenuate the metabolic response to stress, prevent oxidative damage and may involve feeding enterally (through a tube that supplies food via the GI tract, known as enteral nutrition (EN)) or parenterally (intravenous nutrient infusion, known as parenteral nutrition or PN).

The American Society for Parenteral and Enteral Nutrition (ASPEN) has published guidelines for nutrition support for hospitalized people in critical condition. While guidelines for people cannot be applied to dogs and cats without question, the sad fact is that there is a lack of evidence to support most of their recommendations, and there is even less to support any recommendations at all for dogs and cats.

It’s the best we have, and veterinary internists, criticalists, and nutritionists will use evidence from human clinical trials in light of their knowledge about metabolic differences between the species to find the best plan for each individual patient. The recommendations are made, but provided with qualifiers so we can see the level of evidence supporting them. Those levels are A (supported by more than one controlled clinical trial) through E (uncontrolled studies or expert opinion).

So without further delay, here are relevant recommendations for nutrition support of critical patients – they are abridged, paraphrased and modified for animals here, and the grade is supplied in parentheses at the end. I present them here so that pet owners can have a conversation with their veterinarians about providing nutrition actively, and for veterinarians to have a sense of the place of nutrition in the human ICU. These recommendations should not be viewed as a standard of care, but rather as a point of discussion.

A. Regarding the Initiation of Enteral Feeding

Nutritional assessment should include a history that documents changes in weight and food intake and the functional status of the GI tract as well as the severity of the disease and other medical conditions (E). For pet owners, this means you need to be very aware of weight changes in your pet – get a diary and document this on your own at every hospital visit.

Enteral nutrition therapy should be provided in critically ill patients who cannot eat on their own (C). This means that if your pet is not eating in the hospital within a day or two, your doctor should be having a discussion with you about placing a feeding tube or starting parenteral nutrition as appropriate for the medical condition. Enteral nutrition is always the preferred route of feeding over parenteral nutrition (B)

In patients suffering from severe hemodynamic aberrations (for example, shock or blood loss), enteral nutrition should be initiated only after the patient is stable (E).

B. When to Use Parenteral Nutrition

If early enteral nutrition is not feasible for the first 7 days following admission of a patient with no evidence of malnutrition, it is not necessary to provide alternative nutrition support except to encourage voluntary food intake (C). If there is evidence of malnutrition, and enteral nutrition is not feasible, parenteral nutrition should be initiated as soon as possible (C)

C: Dosing of Enteral Feeding

If energy requirements cannot be met after 7-10 days of enteral feeding, supplemental parenteral nutrition should be provided (E). Earlier supplementation does not improve clinical outcomes. This means that your pet could be receiving nutrition from both a feeding tube and intravenously depending on their progress in the ICU.

D: Monitoring Tolerance and Adequacy of Enteral Nutrition

Ileus (lack of gut motility) is propagated by lack of food intake, so npo orders should be minimized (C). This means that if a patient is undergoing multiple anesthetic episodes for procedures, they are spending a lot of time with orders not to be fed. Doctor and pet owner should be aware of this and watch for weight loss in the hospital.

E. Selection of Appropriate Enteral Formulation

Immune modulating enteral formulas should be used for patients undergoing elective surgery, trauma, burns, head/neck cancer and patients on mechanical ventilation, but with caution in patients with sepsis. These formulas contain such supplements as arginine, glutamine, nucleic acids, omega-3 fatty acids and antioxidants. In particular, there is good evidence for these supplements in surgical ICU patients (A) and medical ICU patients (B). Other patients should receive standard enteral formulations (B).
Soluble fiber and small peptide formulas should be used if the patient develops diarrhea (E)

F: Adjunctive Therapy

Probiotic administration has shown definite benefit in post-op transplant and major surgery patients and those with severe trauma (C). Studies have shown both benefit and potential harm in conditions such as pancreatitis, so the benefit of probiotic use in other conditions is unknown (C). Combinations of antioxidants, including selenium, should be administed to all ICU patients. Enteral nutrition for burn,trauma and some other ICU patients should incorporate glutamine.

If a patient on enteral nutrition develops diarrhea, soluble fiber may be beneficial. Insoluble fiber should be avoided in critical patients. Hemodynamically unstable patients are at risk for bowel ischemia, and fiber supplementation of any sort may harm these patients (C).

G: When Indicated, Maximize Efficacy of Parenteral Nutrition

Serum glucose should be closely monitored and strictly controlled during parenteral or other nutrition therapy (E).

Periodic attempts to introduce enteral nutrition should be made while on parenteral nutrition. Parenteral nutrition should be terminated when enteral nutrition is providing ≥ 60% of target calories.

K: Acute Pancreatitis

People with acute pancreatitis should have a nasoesophageal tube placed and enteral nutrition therapy initiated as soon as hypovolemia (dehydration, low blood pressure) is corrected (C). This is currently being debated by veterinarians and veterinary nutritionists.

Patients with mild/moderate pancreatitis should not be fed unless they fail to eat on their own within 7 days or develop an unexpected complication (C).

Use of parenteral nutrition should be considered only where enteral nutrition is not feasible (C) and only after the first 5 days of hospitalization (E).

L. Nutrition Therapy in End-of-Life Situations

Nutrition therapy is not obligatory in futile care or end-of-life situations. Decision to provide nutrition care should be based on family desires and communication and realistic goals.

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