3.4 Pre-Existing Conditions, Fluids, Electrolytes, and Temperature

Endocrine stress responses

Surgery and anesthesia activate the stress response. Catecholamines, cortisol, and glucagon increase insulin resistance and hepatic glucose production. A patient with diabetes can be hyperglycemic after surgery despite fasting, while another patient can become hypoglycemic from insulin or oral agents combined with delayed intake.

CAPA questions may ask what to monitor rather than what diagnosis to memorize. For diabetes, monitor blood glucose, mental status, wound risk, hydration, nausea, and ability to resume intake and medications safely. Hyperglycemia can impair wound healing and increase infection risk. Hypoglycemia can appear as sweating, confusion, tachycardia, tremor, headache, or seizure.

Adrenal and thyroid disorders are less common but high risk. A patient with adrenal insufficiency may be unable to mount a cortisol response and can develop hypotension, weakness, confusion, hyponatremia, and hyperkalemia. A patient with uncontrolled hyperthyroidism may develop thyroid storm with fever, severe tachycardia, altered mental status, and cardiovascular collapse. Both require rapid escalation.

Renal and hepatic physiology

The kidneys regulate fluid volume, potassium, acid-base balance, and elimination of many drugs or active metabolites. Chronic kidney disease can contribute to delayed emergence, respiratory depression from metabolite accumulation, hyperkalemia, acidosis, anemia, hypertension, and fluid overload. Assessment should include mental status, respiratory pattern, edema, lung sounds, rhythm changes, recent labs when available, and urine output if measured.

The liver metabolizes many medications and produces albumin and clotting factors. Cirrhosis can reduce albumin, increasing the free active fraction of highly protein-bound drugs. It can also impair metabolism and coagulation. The clinical result may be exaggerated sedation, bleeding tendency, hypoglycemia, or delayed recovery.

Fluid and electrolyte warning signs

Trousseau sign is tested by inflating a blood pressure cuff above systolic pressure long enough to provoke carpopedal spasm in susceptible patients. In practice, the nurse does not rely on one sign alone; symptoms, history, labs, and patient condition determine urgency.

Hematologic and immune concerns

Anemia reduces oxygen-carrying capacity even when the oxygen saturation appears acceptable. A patient can have adequate saturation of a low hemoglobin concentration and still deliver insufficient oxygen to tissues. Tachycardia, dizziness, pallor, dyspnea, chest discomfort, hypotension, or excessive drainage should prompt concern for bleeding or poor oxygen delivery.

Sickle cell disease is a high-yield example of physiology-based prevention. Hypoxia, dehydration, hypothermia, and acidosis promote red blood cell sickling. Maintaining oxygenation, hydration, normothermia, and acid-base stability reduces risk of painful crisis and acute chest syndrome.

Immune risks include infection, allergic reaction, and anaphylaxis. A latex allergy is not just a chart label; the environment, supplies, medication vial stoppers if relevant, and handoff communication must support avoidance. Anaphylaxis requires immediate help, airway and oxygen support, epinephrine per emergency protocol, IV access, fluids, and removal of the trigger when possible.

Temperature regulation and shivering

Perianesthesia patients become hypothermic because anesthetics impair thermoregulation, vasodilation redistributes core heat, skin is exposed, irrigation fluids may be cool, and ambulatory areas often move quickly. Pediatric, geriatric, thin, hypothyroid, trauma, burn, and long-procedure patients are especially vulnerable.

Shivering is an attempt to produce heat through involuntary muscle activity, but it can increase oxygen consumption and carbon dioxide production substantially. That matters in patients with coronary artery disease, heart failure, lung disease, anemia, or limited reserve. The nurse should assess temperature, oxygenation, pain, and hemodynamics, then use active warming, warmed blankets or forced-air warming as available, warmed fluids when ordered, and provider-directed medications when appropriate.

Hyperthermia is a different concern. Fever after a short ambulatory procedure may reflect infection, inflammatory response, warming overshoot, transfusion reaction, thyroid storm, or malignant hyperthermia depending on timing and associated findings. Muscle rigidity, rapidly rising carbon dioxide, tachycardia, acidosis, hyperkalemia, and hyperthermia after triggering agents should prompt emergency response according to facility protocol.

Discharge readiness depends on physiology

Ambulatory discharge is not based on time alone. The patient should have stable respiratory status, hemodynamics near acceptable baseline, adequate mentation, manageable pain and nausea, controlled bleeding, acceptable temperature, safe mobility, and an individualized plan for pre-existing conditions. When physiology is not stable, discharge teaching cannot compensate for an unsafe discharge.