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Thorough physical examination is essential to the establishment of an adequate resuscitation plan. Hemodynamic stability should be assessed, which is reflected in pulse quality, mucous membrane color, heart rate, level of consciousness, and body temperature, as well as difference in temperature between the trunk and the extremities. Blood pressure and lactate measurement are useful bedside tests that aid in assessment of perfusion. If a patient is assessed as hypoperfused and no obvious contraindications to fluid therapy exist, a fluid bolus of isotonic crystalloid at approximately 10–20 ml/kg can be administered intravenously. Perfusion parameters should be reassessed after the bolus is delivered and fluid therapy altered as needed.

If the patient is hemodynamically stable but is dehydrated, body weight, percent dehydration, and continuing losses should dictate the intravenous fluid rate. Dehydration should be corrected quickly (over one to four hours) to optimize the patient as an anesthetic candidate (Figure 6.4).

At the time of intravenous catheter placement, blood may be collected for initial evaluation, and should at a minimum include a packed red blood cell volume, total solids, and blood glucose. Ideally, venous blood gas, electrolytes, and blood lactate level should be sampled. At that time, blood can also be collected and submitted for a complete blood count and serum chemistry. Intravenous fluid choice can then be tailored to the individual patient's needs, and, if any acid–base or electrolyte abnormalities are present, they can be appropriately addressed prior to and during the surgical procedure. For example, if metabolic alkalosis is present due to vomiting and chloride sequestration in the gastrointestinal (GI) tract, the fluid of choice should be physiologic (0.9%) saline to provide chloride necessary to excrete bicarbonate and reestablish normal acid–base balance. Careful attention should be paid to sodium levels, as sodium has frequently been reported to be low in animals with intussusceptions [5–7]. If hyponatremia is present and the patient requires a fluid bolus, a fluid most isotonic to the patient should be administered to minimize sudden fluid shifts and deleterious neurologic sequelae of rapidly correcting hyponatremia. Unless a normal sodium level has been reported in the patient within 48 hours of presentation, it should be assumed that hyponatremia is chronic, and care should be taken not to raise the sodium level more than 8–10 mEq in 24 hours to avoid central pontine myelinolysis [17].

Figure 6.4 Algorithm for fluid resuscitation in patients with intussusception. IV, intravenous; GI, gastrointestinal; BW, body weight; pRBCs, packed red blood cells; FFP, fresh frozen plasma.

Many animals presenting with intussusceptions will have moderate to severe abdominal discomfort and nausea. Nausea may be addressed with injectable antiemetics, such as the neurokinin‐1 antagonist maropitant, or 5‐HT3 serotonin receptor antagonists like dolasetron or ondansetron. Metoclopramide administration is not recommended, as its prokinetic properties may contribute to exacerbation of intussusception.

Level of comfort via pain scoring should be determined to develop an optimal analgesic plan. Opioid analgesics are an excellent choice, and may be selected based on availability, degree of pain and likelihood of adverse effects, such as vomiting and respiratory depression. For example, for mild to moderate abdominal pain, an agonist–antagonist opioid such as buprenorphine may be chosen, whereas for severe discomfort, a more potent analgesic such as methadone may be administered.

Patients with devitalized segments of intestine secondary to intussusception are at risk and may develop septic peritonitis secondary to necrosis and breakdown of the GI tract. These patients will frequently present with signs consistent with shock and sepsis, such as a fever, injected mucous membranes, brisk capillary refill time, and bounding pulses, and will require aggressive resuscitation and supportive care. If septic peritonitis is suspected, broad‐spectrum antibiotic therapy should be instituted as soon as possible, as it has been shown to improve outcome in patients with sepsis (see Chapter 11; Peritonitis) [18]. Antibiotics are also recommended if aspiration pneumonia is identified on thoracic radiographs.