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Acid-base and electrolyte interpretation in vomiting dogs | VETgirl Veterinary Continuing Education Videos

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January 2017

In this VETgirl online veterinary continuing education video, we discuss the importance of acid/base status and electrolytes in our veterinary patients. This is an 11-year-old, male neutered, Scottish Terrier who presented for a 2-day history of hematemesis and melena after getting into a bag of dog treats. On presentation, the dog was critically ill, laterally recumbent, tachycardiac, hypotensive (based on poor pulse quality), and had muscle tremors and a painful abdomen. Due to clinical signs of hypovolemic shock, a 30 mL/kg isotonic crystalloid bolus was given, after which his vitals normalized. Diagnostic workup of this dog included chest and abdominal radiographs and clinicopathologic testing. Radiographs revealed aspiration pneumonia and an unremarkable abdomen. Clinicopathologic testing revealed a severe metabolic alkalosis with secondary respiratory acidosis, along with severe electrolyte derangements. The sodium, potassium, chloride and ionized calcium levels were severely low (with the latter likely resulting in the clinical signs of muscle tremors). Based on the history, clinical signs, and diagnostic workup, a presumptive diagnosis of severe pancreatitis or gastrointestinal disease (e.g., foreign body, etc.) was suspected.

One of the most common causes of metabolic alkalosis in veterinary medicine is due to gastrointestinal loss of chloride through vomiting. This is often due to an upper gastrointestinal obstruction. The loss of the anion, chloride, contributes towards the metabolic alkalosis, as bicarbonate (another anion) must be absorbed with sodium in lieu of an absent or low chloride level. As a result, a metabolic alkalosis develops (as diagnosed on a venous blood gas based on a positive base excess, an elevated bicarbonate, and a pH > 7.45). In this patient, hyponatremia with hypovolemia was seen, likely due to the body’s attempt to maintain volume at the expense of tonicity.

This dog was volume resuscitated and rehydrated with a maintenance crystalloid (with potassium chloride supplementation, once stable), calcium supplementation (to stop the twitching), anti-emetic therapy, supportive care, and electrolyte monitoring. While hospitalized, the patient’s stomach became progressively more distended with large volumes of gastric fluid, so a nasogastric (NG) tube as placed to evacuate the stomach and minimize the risk of regurgitation and further aspiration. Due to the patient’s continued metabolic alkalosis, electrolyte abnormalities, and persistent ileus, an abdominal ultrasound was performed. Despite initial unremarkable abdominal radiographs, ultrasound revealed a duodenal foreign body. The patient was taken to surgery and a walnut-appearing object was removed from the duodenum. Post-operatively, the patient recovered quite well and his electrolytes completely normalized, as did his metabolic alkalosis. So, remember to monitor the acid-base status and electrolytes in your vomiting patients, as it can be a tell-tale sign of a foreign body.

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  1. Ivia Alfonso says:

    Hello.
    I would like to know what is the general guideline to administer potassium to fluids when you do not have the option to monitoring serum potassium levels, but the patient is showing signs of hypokalemia like weakness and vomiting or dilutional hypokalemia is a risk.
    Thanks

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