Postoperative Day 1: Tachycardia, Oliguria, and a Missed Insulin Dose
A 58-year-old man with type 2 diabetes is 20 hours post open cholecystectomy under general anesthesia. He is drowsy but arousable. He has a nasogastric tube on low suction, an indwelling urinary catheter, and a peripheral IV of 0.9% sodium chloride at 100 mL/hr. His usual evening insulin was withheld pre-operatively and has not been restarted because he is 'nil by mouth'. Observations: HR 118/min, BP 104/62 mmHg, RR 24/min, SpO2 95% on room air, temperature 37.9 C. Urine output over the last 6 hours is 90 mL, dark and concentrated. Capillary glucose is 18.4 mmol/L. The abdomen is distended with absent bowel sounds; the wound is dry and intact. He reports nausea and 'feeling thirsty'.
1. Prioritize the three most urgent problems and explain the bedside reasoning that makes each urgent rather than merely abnormal.
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1. Hypovolemia with oliguria (most urgent). Urine output of 90 mL over 6 hours is about 15 mL/hr, well below the 0.5 mL/kg/hr minimum. Combined with HR 118, BP 104/62 (likely down from his baseline), concentrated urine, thirst, and nausea, this is a picture of intravascular depletion rather than a primary renal problem. The NG tube on suction plus insensible losses plus only 100 mL/hr of crystalloid explain the deficit. Untreated, this progresses to acute kidney injury and shock.
2. Hyperglycemia without insulin coverage. Glucose 18.4 mmol/L in a fasting, stressed, post-operative patient with type 2 diabetes reflects the combination of surgical stress hormones and a genuine insulin gap. Withholding insulin because he is 'nil by mouth' is the error: basal insulin is needed even when not eating. Persistent hyperglycemia impairs wound healing and increases infection risk, and it worsens osmotic diuresis, feeding the dehydration above.
3. Paralytic ileus with NG decompression. Distension, absent bowel sounds, and nausea post-operatively are expected to a degree, but the NG tube is a source of ongoing fluid and electrolyte loss (especially potassium and chloride) that must be replaced.
Reasoning principle: Abnormal numbers become urgent when they are trending in a dangerous direction or when they interact. Here the dehydration, hyperglycemia, and NG losses reinforce one another, which is why they are managed together rather than in isolation.
2. The surgeon orders 0.9% sodium chloride 500 mL over 1 hour and asks you to 'sort out the sugars'. State your immediate nursing actions, including what you would clarify with the prescriber before acting, and why.
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Immediate actions:
- Recheck the capillary glucose on a fresh strip to confirm 18.4 mmol/L before any insulin decision.
- Begin the 500 mL bolus as ordered and reassess HR, BP, and urine output at 15-minute intervals during the infusion.
- Document a strict fluid balance and hourly urine output; report if output does not improve after the bolus.
- Check a point-of-care ketone measurement if available, since marked hyperglycemia with dehydration can mask early ketosis even in type 2 diabetes.
What to clarify before acting:
- Insulin regimen: The order to 'sort out the sugars' is not a prescription. I would ask for a specific regimen, typically a correction dose of rapid-acting insulin plus resumption of his basal insulin, and a defined target range and recheck interval. I cannot administer a variable-dose insulin without explicit parameters.
- Potassium: NG suction plus insulin will drive potassium intracellularly. I would request a serum potassium and glucose-potassium panel before giving repeated insulin doses, because giving insulin to a hypokalemic patient can precipitate arrhythmia.
- Fluid choice: If his sodium is low or he remains oliguric after the bolus, the prescriber may want a different fluid strategy; I would flag this rather than silently continue.
Why: Insulin is a high-alert medication. Acting on an ambiguous verbal instruction is a classic source of harm, and the correct professional move is to seek a clear, written order while continuing the interventions that are already prescribed.
3. Twelve hours later his urine output is 40 mL/hr, glucose is 9.8 mmol/L, and he is more alert but complains of abdominal cramping and has vomited twice. How does your priority change, and what monitoring do you add?
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How the priority shifts: The hypovolemia and hyperglycemia are responding (output now adequate, glucose near target), so the leading problem becomes the gastrointestinal tract - a persistent or worsening ileus with vomiting raises the risk of aspiration, further electrolyte loss, and a possible anastomotic or obstructive complication.
Actions and monitoring to add:
- Keep the NG tube patent and on the ordered suction; do not clamp it without an order, and measure and record the drainage volume and character.
- Position him semi-recumbent and keep suction and airway equipment at the bedside given the vomiting.
- Check serum electrolytes, especially potassium, sodium, and chloride, because repeated vomiting and NG losses cause hypokalemic, hypochloremic metabolic alkalosis.
- Assess the abdomen for rigidity, rebound tenderness, and change in bowel sounds, and report new focal tenderness or fever, which would suggest a surgical complication rather than simple ileus.
- Reassess glucose more frequently while he is vomiting (he is not absorbing oral intake), and confirm the insulin plan covers this period.
- Maintain fluid balance and reassess urine output hourly, since a new round of losses can re-create the original dehydration.
Reasoning principle: Priorities are dynamic. Once the first crisis is controlled, the nurse re-triages based on what is now most likely to cause harm, and adds monitoring targeted at the new risk.