Today's Veterinary Practice

JAN-FEB 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 64 FLUID THERAPY Hydration status should be interpreted with the clinical status of the patient in mind. For example, hypersalivation in a nauseated patient may result in moist mucous membranes, but the patient may still have decreased skin turgor, indicating dehydration. Conversely, decreased skin turgor may be present in emaciated or older animals regardless of hydration status. In pediatric animals, skin turgor is often maintained because of increased skin elasticity, making this finding more difficult to interpret in this population. Assessment of Intravascular Volume Intravascular volume can also be assessed on physical examination. Signs of decreased intravascular volume, or hypovolemia, include increased heart rate, fair or weak pulses, coolness of the distal limbs, weakness, and pale mucous membranes. Although blood pressure can initially be normal or even high in the early stages of hypovolemic shock, a normal blood pressure in conjunction with physical examination findings consistent with hypovolemia should not dissuade clinicians from considering hypovolemia and treating appropriately because compensated shock will eventually progress to the uncompensated stage. METHOD OF DELIVERY The 4 primary means of fluid delivery are intravenous (IV), intraosseous, subcutaneous (SC), and enteral. IV fluid administration is generally preferred for hospitalized patients because the delivery rate can be controlled and changed quickly depending on patient requirements. Intraosseous catheters can be placed in neonates, exotic patients, and other small animals in which IV access cannot be obtained, but these catheters may not be tolerated for extended periods once patients have been resuscitated. SC fluids are not recommended for hospitalized patients because they are more difficult to titrate. In addition, patients with intravascular deficits require more aggressive support; SC fluids are not adequately absorbed because of peripheral vasoconstriction and so are not indicated for treating shock. Patients that are easily overloaded may receive too much fluid with no means of discontinuation once fluids are administered, resulting in fluid overload. In patients that are being discharged from the hospital, SC fluids may become a component of home care if they are well tolerated and there are ongoing excessive fluid losses. Enteral fluids are ideal in patients that can tolerate them because enteral delivery is the most physiologic method to provide water. Many hospitalized patients cannot take in adequate water for various reasons (eg, vomiting, nausea, hypotension). If a patient can tolerate FIGURE 3. Dehydrated cat on IV fluids. Note the sunken eyes. TABLE 1 Subjective Estimation of Percentage Dehydration Based on Physical Examination Parameters 5 ESTIMATED DEHYDRATION PHYSICAL EXAMINATION FINDINGS <5% Not detectable 5%–6% Tacky mucous membranes 6%–8% Decreased skin turgor Dry mucous membranes 8%–10% Retracted globes within orbits 10%–12% Persistent skin tent Dull corneas Evidence of hypovolemia >12% Hypovolemic shock Death Data adapted from reference 5. The 4 primary means of fluid delivery are intravenous (IV), intraosseous, subcutaneous (SC), and enteral. IV fluid administration is generally preferred for hospitalized patients because the delivery rate can be controlled and changed quickly depending on patient requirements.

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