ANSWER 42
This patient has postoperative acute renal failure due to a combination of intra-abdominal
sepsis and aminoglycoside nephrotoxicity. Her sepsis is due to an anastomotic leak with a
localized peritonitis which has been partially controlled with antibiotics. Her sepsis syndrome
is manifested by fever, tachycardia, hypotension, hypoglycaemia, metabolic acidosis (low
bicarbonate) and oliguria. The low sodium and high potassium are common in this condition
as cell membrane function becomes less effective. The elevated white count is a marker for
bacterial infection and the low platelet count is part of the picture of disseminated intravas-
cular coagulation. Jaundice and abnormal liver function tests are common features of intra-
abdominal sepsis. Aminoglycosides (gentamicin, streptomycin, amikacin) cause auditory and
vestibular dysfunction, as well as acute renal failure. Risk factors for aminoglycoside nephro-
toxicity are higher doses and duration of treatment, increased age, pre-existing renal insuffi-
ciency, hepatic failure and volume depletion. Aminoglycoside nephrotoxicity usually occurs
7–10 days after starting treatment. Monitoring of trough levels is important although an
increase in the trough level generally indicates decreased excretion of the drug caused by a
fall in the glomerular flow rate. Thus, nephrotoxicity is already established by the time the
trough level rises.
This patient needs urgent resuscitation. She requires transfer to the intensive care unit where
she will need invasive circulatory monitoring with an arterial line and central venous pres-
sure line to allow accurate assessment of her colloid and inotrope requirements. She also needs
urgent renal replacement therapy to correct her acidosis and hyperkalaemia. In a haemo-
dynamically unstable patient like this, continuous haemofiltration is the preferred method.
The patient also needs urgent surgical review. The abdomen should be imaged with either
ultrasound or computed tomography (CT) scanning to try to identify any collection of pus.
Once haemodynamically stable, the patient should have a laparotomy to drain any collection
and form a temporary colostomy.
- Postoperative acute renal failure is often multifactorial due to hypotension, sepsis and the
use of nephrotoxic drugs such as aminoglycosides and non-steroidal anti-inflammatory
drugs (NSAIDs). - Aminoglycoside drugs are extremely valuable for treating Gram-negative infections, but
levels must be monitored to avoid toxicity. - Sepsis syndrome must be recognized early and treated aggressively to reduce the mor-
bidity and mortality of this condition.