A 77-year-old diabetic, hypertensive male patient is admitted to ICU after an emergency repair of a ruptured abdominal aortic aneurysm.

His blood biochemistry the day after his admission to ICU is as follows:

Parameter

Patient Value

Adult Normal Range

Sodium

140 mmol/L

135 – 145

Potassium

5.4 mmol/L*

3.5 – 5.0

Chloride

113 mmol/L*

95 – 105

Bicarbonate

18.0 mmol/L*

22.0 – 26.0

Urea

39.0 mmol/L*

3.0 – 8.0

Creatinine

391 μmol/L*

45 – 90

  1. List the specific factors that may contribute to a high serum creatinine value in this patient. (30% marks)
  2. What factors would influence your decision whether to start renal replacement therapy (RRT) in this patient? (70% marks)

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College answer

List the specific factors that may contribute to a high serum creatinine value in this patient. (3 Marks)
Pre-existing elevation of serum creatinine:
Diabetic Nephropathy Hypertensive Nephrosclerosis Renal Artery Stenosis

Acute elevation of serum creatinine Pre-renal factors
Hypotension, hypoperfusion
Prolonged aortic clamp time, surgical ligation renal artery Intra-abdominal hypertension
Cholesterol Embolism Renal factors
Radio-contrast Nephrotoxic drugs Rhabdomyolysis Sepsis
Post renal factors
Occlusion of both ureters - rare

What factors would influence your decision whether to start RRT in this patient? (7 marks)
Several factors would influence this decision
 
General condition of the patient including volume status

Baseline renal function and its likely trajectory

Other factors

If the patient is clinically stable, the current biochemistry would support a watch and wait approach. The serum creatinine value of 391 umol/L does put the patient in KDIGO stage 3 (or RIFLE ‘F’), which could be past the point when early RRT can be considered. The rate of rise of creatinine, urine output and its course (increasing or decreasing) and preoperative creatine will give an idea of the likelihood of renal recovery. If the patient was unstable, or had evidence of compromise from volume overload then early initiation of RRT could be considered.
Other factors might include – preoperative dialysis dependence
A requirement to remove the effects of sedative drugs to allow prognostication (perhaps in the setting of a cardiac arrest for example) might be another consideration.

Examiners Comments:

Candidates who tailored their answer to the specific patient in the question scored well, in contrast to those who simply listed generic indications for dialysis.

Discussion

"specific factors that may contribute to a high serum creatinine" basically means "likely causes of deterioration in renal function", just as it did in Question 24 from the first paper of 2007.  

Answer organised by pathophysiology:

  • Pre-renal
    • Hypovolemia due to blood loss
    • Hypotension due to distributive shock, eg. sepsis
    • Cardiac failure
    • Renal vascular damage
    • Abdominal compartment syndrome
  • Renal
    • ATN due to prolonged aortic cross-clamp time
    • Nephrotoxicity due to drugs, eg. gentamicin or metformin
    • Contrast-induced nephropathy
    • ATN due to rhabodomyolysis
  • Post-renal
    • Intraoperative ureteric or bladder injury
    • kinked or malpositioned IDC

Answer organised by aetiology:

  • Vascular and cardiac causes
    • Renal vascular damage
    • Abdominal compartment syndrome
    • ATN due to prolonged aortic cross-clamp time
    • Cardiac failure with low cardiac output
  • Infectious causes
    • Septic shock due to bacterial translocation from the gut during a period of ischaemia, or from ischaemic bowel due to atheromatous emboli
  • Idiosyncratic causes
    • The bladder was perforated intraoperatively, and this rise in creatinine represents its reabsorption from the abdominal cavity
  • Drug-related causes
    • Nephrotoxicity due to drugs, eg. gentamicin or metformin
    • Contrast-induced nephropathy
  • Traumatic causes
    • Hypovolemia due to blood loss
    • Rhabdomyolysis

What factors would influence your decision whether to start RRT in this patient?

History factors

  • Premorbid renal function (i.e. is this the baseline??)
  • patient's course pre precedure (i.e. did they arrest three times in the ED)
  • Perioperative haemodynamic course (did the patient have prolonged periods of hypotension to explain this degree of ATN?)
  • Surgical findings consistent with severe ATN (eg. prolonged supra-renal crossclamp time)

Clinical indicators

  • Anuria or oliguria
  • Presence of dialysiable toxins, i.e. IV contrast or sedatives
  • Fluid overload affecting respiratory function

Modifiers and imperatives: how necessary is it to...

  • Control the fluid balance (i.e. do I really need to worry about pleural effusions and pulmonary oedema, or is this patient's respiratory function already borderline?)
  • Control the acid-base balance (i.e is the patient's acid base balance rapidly deteriorating, or can we temporise with alkalinisng therapies)
  • Control the electrolytes (i.e. the potassium is currently survivable, but tomorrow, is there such hyperkalemia that ECG changes are developing?)
  • Wash out the urea (is the uraemia preventing extubation?)

Presence of positive prognostic features:

  • Controlled shock 
  • Good urine output
  • Short perioperative period of crossclamp or hypotension
  • Minimal exposure to nephrotoxins perioperatively

References

References

Schrier, Robert W., et al. "Acute renal failure: definitions, diagnosis, pathogenesis, and therapy." The Journal of clinical investigation 114.1 (2004): 5-14.

Perazella, Mark A., and Glen S. Markowitz. "Drug-induced acute interstitial nephritis." Nature Reviews Nephrology 6.8 (2010): 461-470.

Heyns, C. F., and P. D. Rimington. "Intraperitoneal rupture of the bladder causing the biochemical features of renal failure." British journal of urology 60.3 (1987): 217-222.

Cho, Jae-Sung, et al. "Contemporary results of open repair of ruptured abdominal aortoiliac aneurysms: effect of surgeon volume on mortality." Journal of vascular surgery 48.1 (2008): 10-18.

Brimacombe, J., and A. Berry. "Haemodynamic management in ruptured abdominal aortic aneurysm." Postgraduate medical journal 70.822 (1994): 252-256.