How do I recognize and manage complications of fluid therapy including overload and electrolyte derangements?

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Fluid overload is best prevented through weight-based monitoring and volume-restricted protocols, because once edema is established it is difficult to resolve and there is no definitive therapy. Recognizing fluid overload relies on frequent body weight measurement every 6–12 hours; a 10% increase from baseline indicates hypervolemia.2 Clinical signs progress from mild overhydration (increased body weight, mild or localized peripheral edema) to life-threatening fluid overload (respiratory distress, moderate to severe multifocal peripheral edema, renal, hepatic, or gastrointestinal dysfunction).2 Point-of-care ultrasound is a non-invasive tool to detect early pulmonary fluid accumulation and guide ongoing fluid decisions.16 Hypertension is not a reliable indicator of hypervolemia — it is rarely associated with hypervolemia or edema, though some patients with renal disease may develop hypertension concomitantly.2 Managing established fluid overload requires active intervention once moderate-to-severe signs are present: discontinue intravenous (IV) fluids, provide oxygen support, administer a diuretic, increase patient mobility, and remove pleural fluid via thoracentesis or ascites via abdominocentesis if present.2 Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) should be considered for discontinuation to improve glomerular filtration rate.2 Hemodialysis has a very limited therapeutic role in treating edema because movement of edema fluid into the vascular space is limited.2 For mild overhydration without systemic signs, discontinuing IV fluids and increasing patient mobility may be adequate.2 Cats and small dogs are at disproportionate risk of fluid overload given their smaller blood volumes, and even cats without underlying cardiac disease may be susceptible to fluid overload at rates that would be tolerated by healthy dogs.6 Where systemic inflammation exists, the protective mechanisms within the lung are deranged and increases