Postoperative Complications
CASE 97: loW urine output
history
As the doctor on call, you are asked to review a postoperative patient on the ward. The patient is an 86-year-old man who had a right hemicolectomy for a caecal carcinoma 2 days previously. Preoperatively, he was on antihypertensive medication, which has not been restarted. During the day, his urine output had been poor, with a total of 75 mL produced over the past 8 h. He has taken very little fluid orally during the day. His epidural was removed earlier that afternoon and he has been started on non-steroidal anti-inflammatory drugs (NSAIDs) for pain relief.
examination
He is alert and orientated in time, place and person. He is afebrile, blood pressure is 110/70 mmHg and pulse 110/min. His chest is clear and heart sounds are normal. His abdomen is tender around the incision, but otherwise soft and non-tender. He has normal bowel sounds and has opened his bowels since the operation.
INVESTIGATIONS
he had postoperative blood tests on day 1 which were normal. no blood tests were available from that day.
Questions
•What is normal minimal urine output expected in a 70-kg man?
•What are the causes of acute renal failure?
•What would be your approach to managing this patient?
•What biochemical changes would you see with acute renal failure?
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ANSWER 97
Urine production should be greater than 0.5 mL/kg/h. The aetiology of acute renal failure can be thought of in three main categories:
•Pre-renal: the glomerular filtration is reduced because of poor renal perfusion. This is usually caused by hypovolaemia as a result of acute blood loss, fluid depletion or hypotension. The patient’s tubular and glomerular function are normal, so renal function should be restored with appropriate fluid replacement.
•Renal: this is the result of damage directly to the glomerulus or tubule. The use of drugs such as NSAIDs, contrast agents or aminoglycosides all have direct nephrotoxic effects. Acute tubular necrosis can occur as a result of prolonged hypoperfusion, either perioperatively or postoperatively. Pre-existing renal disease such as diabetic nephropathy or glomerulonephritis makes patients more susceptible to further renal injury.
•Post-renal: this can be simply the result of a blocked catheter. This should always be checked as a cause for complete anuria in a previously fit patient. Calculi, blood clots, ureteric ligation and prostatic hypertrophy can also all lead to obstruction of urinary flow.
This patient is likely to be dehydrated as a result of his poor oral intake since his operation. Firstly, check the catheter by flushing it and palpate the abdomen for a distended bladder. Then calculate his fluid balance since the operation. Check for any evidence of sepsis. With his current blood pressure, his antihypertensive medication does not need to be restarted. It is important to maintain a good blood pressure to ensure adequate renal perfusion. The NSAIDs should be stopped as these have a direct nephrotoxic effect which may worsen his renal function.
Examine the patient for any evidence of fluid overload and check his history for previous renal problems or cardiovascular disease. Initially, the patient should be given a fluid challenge. A bolus infusion of 250 mL should give an improvement in urine output if the cause is pre-renal. If after two attempts no improvement is seen, the patient should be considered for transfer to a high-dependency unit and central venous pressure monitoring.
!Biochemical changes in acute renal failure
•hyponatraemia
•hyperkalaemia
•hypocalcaemia
•metabolic acidosis
KEY POINT
• urine production should be greater than 0.5 ml/kg/h.
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Postoperative Complications
CASE 98: vomiting anD abDominal DiStenSion
history
You are called to the ward at 3 a.m. to see a 20-year-old man with persistent vomiting. He had an emergency laparotomy 3 days previously. The doctor on call earlier had prescribed anti-emetics for the patient, without carrying out a full assessment. The patient is extremely distressed and the nurse in charge is concerned about his sudden deterioration. You retrieve the operation note and find the patient had undergone a ‘normal’ laparotomy for trauma. The small and large bowel were both examined carefully and no injury was found. He had made a good recovery and had been moved onto free fluids earlier in the day. There was no nasogastric tube left after the operation, and the urinary catheter had been removed.
examination
The patient is rolling around in the bed having just vomited. His blood pressure is 120/75 mmHg and pulse rate 110/min. He has a midline incision covered with a dry dressing. The abdomen is distended and tympanic. On palpation, he is tender around the incision only. There are no bowel sounds on auscultation.
INVESTIGATIONS
|
|
Normal |
haemoglobin |
12.0 g/dl |
11.5–16.0 g/dl |
mean cell volume |
82 fl |
76–96 fl |
WCC |
10.2 × 109/l |
4.0–11.0 × 109/l |
platelets |
253 × 109/l |
150–400 × 109/l |
Sodium |
132 mmol/l |
135–145 mmol/l |
potassium |
2.9 mmol/l |
3.5–5.0 mmol/l |
urea |
5.0 mmol/l |
2.5–6.7 mmol/l |
Creatinine |
54 μmol/l |
44–80 μmol/l |
an x-ray of the abdomen is shown in Figure 98.1.
Questions
• |
What is shown on the abdominal |
|
x-ray? |
• |
What are the most common causes? |
• |
What is the most likely cause in |
|
this patient? |
• |
How would you manage this patient? |
Figure 98.1 plain x-ray of the abdomen.
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100 Cases in Surgery
ANSWER 98
When assessing a postoperative patient on the ward, it is important to read the operation note as well as making a physical assessment. Unexpected findings or difficulties during the procedure should be documented, and this may aid your clinical decision making. This patient has a postoperative paralytic ileus. An ileus is a normal physiological event after abdominal surgery. It usually resolves spontaneously within 2–3 days of the procedure. Paralytic ileus is defined as ileus of the intestine persisting for more than 3 days after surgery. His bowels had not returned to normal function by day 3 and he had started free fluids that morning. This resulted in vomiting and abdominal discomfort.
A nasogastric tube should be placed to decompress the bowel, and a urinary catheter inserted to monitor his urine output.
The most common cause of an ileus is an intra-abdominal operation. Other factors can prolong an ileus and should be looked for and corrected if possible. This patient has hypokalaemia, which should be corrected.
!Causes of ileus
•Sepsis: intra-abdominal inflammation and peritonitis
•Drugs: opioids, antacids
•Metabolic: hypokalaemia, hyponatraemia, hypomagnesia, anaemia
•Myocardial infarction
•Pneumonia
•Head injury and neurosurgical procedures
•Retroperitoneal haematomas
For patients with protracted ileus, mechanical obstruction should be excluded by a smallbowel follow-through or a computerized tomography scan. Before further investigation, underlying sepsis or electrolyte abnormalities should be corrected. Medications that produce ileus (e.g. opiates) should also be stopped.
KEY POINTS
•postoperative ileus should resolve after 2–3 days.
•electrolyte abnormalities are a common cause of paralytic ileus during the postoperative period.
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