Medicine – Severe Complications of Acute Kidney Injury

Acute kidney injury (AKI) is the modern term that has largely replaced acute renal failure (ARF). Severe AKI can rapidly produce life-threatening disturbances in electrolytes, acid–base balance, fluid status and uraemic toxin accumulation.

The most important complications to recognise urgently are hyperkalaemia, pulmonary oedema, severe volume disturbance, metabolic acidosis and uraemic complications such as bleeding, encephalopathy and pericarditis.

1. Hyperkalaemia

Hyperkalaemia is one of the most immediately dangerous complications of AKI.

When renal function falls, the kidneys are less able to excrete:

Potassium.

As a result, serum potassium may rise rapidly.

2. Why Hyperkalaemia Is Dangerous

Severe hyperkalaemia can disturb cardiac electrical activity and cause:

Tall peaked T waves.

PR prolongation.

Loss of P waves.

QRS widening.

Sine-wave pattern.

Ventricular arrhythmias.

Cardiac arrest.

Therefore:

AKI + severe hyperkalaemia = medical emergency.

3. Factors That Can Worsen Hyperkalaemia

Hyperkalaemia may become more severe when AKI is associated with:

Metabolic acidosis.

Tissue breakdown.

Rhabdomyolysis.

Haemolysis.

Certain medications.

Important drugs include:

ACE inhibitors.

ARBs.

Potassium-sparing diuretics.

4. Management of Severe Hyperkalaemia

Immediate treatment may include:

Intravenous calcium when there are significant ECG changes or severe hyperkalaemia requiring membrane stabilisation.

Insulin with glucose to shift potassium into cells.

Nebulised beta₂-agonist as an additional intracellular shift.

The underlying cause should be corrected, and potassium-removing strategies should be used as appropriate.

5. Hyperkalaemia and Dialysis

If hyperkalaemia is:

Severe.

Persistent.

Recurrent after temporary treatment.

or

Associated with dangerous ECG abnormalities,

urgent dialysis may be required.

Therefore:

REFRACTORY HYPERKALAEMIA → URGENT DIALYSIS.

6. Pulmonary Oedema

AKI can impair the renal excretion of:

Sodium

and

Water.

This can lead to rapid expansion of extracellular fluid volume.

If fluid accumulates in the lungs, the patient develops:

Pulmonary oedema.

7. Clinical Features of Pulmonary Oedema

Possible features include:

Severe breathlessness.

Orthopnoea.

Hypoxaemia.

Fine inspiratory crackles.

Raised JVP.

Peripheral oedema.

Respiratory distress.

8. Why Pulmonary Oedema Is Dangerous

Pulmonary oedema interferes with:

Oxygen transfer across the alveolar-capillary membrane.

This can cause:

Severe hypoxaemia

and potentially:

Respiratory failure.

Therefore it must be recognised and treated rapidly.

9. Management of Fluid Overload

Management may include:

Oxygen or ventilatory support when required.

Fluid restriction.

Salt restriction.

Loop diuretics if the patient is capable of responding.

If pulmonary oedema remains refractory, dialysis may be required.

10. Pulmonary Oedema and Dialysis

A major indication for urgent dialysis is:

SEVERE FLUID OVERLOAD WITH PULMONARY OEDEMA THAT CANNOT BE ADEQUATELY CONTROLLED MEDICALLY.

This corresponds to the:

“O – Overload”

in the AEIOU mnemonic for dialysis indications.

11. Intravascular Volume Depletion

The original notes correctly mention:

Intravascular volume depletion.

AKI can occur because of volume depletion, but severe AKI can also coexist with or worsen intravascular depletion depending on the underlying illness.

Possible causes include:

Vomiting.

Diarrhoea.

Haemorrhage.

Sepsis.

Burns.

Third-space fluid loss.

12. Consequences of Volume Depletion

Reduced circulating volume causes:

Reduced renal perfusion.

This may worsen:

Pre-renal AKI

and, if prolonged, may progress to:

Acute tubular injury.

13. Clinical Features of Volume Depletion

Possible findings include:

Hypotension.

Postural hypotension.

Tachycardia.

Dry mucous membranes.

Reduced peripheral perfusion.

Low urine output.

However, physical signs are imperfect and should be interpreted with the overall clinical picture.

14. Volume Replacement

When true hypovolaemia is present, treatment usually involves:

Appropriate intravenous fluid replacement.

The amount and rate depend on:

Cause.

Blood pressure.

Cardiac status.

Urine output.

Evidence of ongoing losses.

15. Fluid Overload

At the opposite extreme, AKI can also cause:

Fluid overload.

This occurs because impaired kidneys cannot adequately excrete sodium and water.

Therefore AKI can present with either:

Volume depletion

or

Volume overload.

16. Clinical Features of Fluid Overload

Features include:

Peripheral oedema.

Raised JVP.

Weight gain.

Hypertension.

Pulmonary crackles.

Pulmonary oedema.

17. Why Volume Assessment Matters

Incorrect fluid treatment can worsen AKI.

Giving excessive fluid to a patient who is already overloaded may cause:

Pulmonary oedema.

Conversely, failing to replace true volume depletion can worsen:

Renal hypoperfusion.

Therefore:

ASSESS VOLUME STATUS CAREFULLY BEFORE GIVING LARGE AMOUNTS OF FLUID.

18. Bleeding

Severe renal failure can cause a:

Bleeding tendency

because uraemia impairs:

Platelet function.

Platelet numbers may be relatively normal, but platelet adhesion and aggregation are impaired.

This is called:

Uraemic platelet dysfunction.

19. Clinical Features of Uraemic Bleeding

Possible manifestations include:

Easy bruising.

Epistaxis.

Bleeding from venepuncture sites.

Gastrointestinal bleeding.

Mucosal bleeding.

Prolonged bleeding after procedures.

20. Why Uraemic Bleeding Occurs

The main problem is not usually severe thrombocytopenia.

Instead, uraemic toxins interfere with:

Platelet adhesion.

Platelet aggregation.

Interaction between platelets and vascular endothelium.

Therefore:

Platelet count may be normal despite significant bleeding risk.

21. Management of Uraemic Bleeding

Management depends on severity.

Important measures may include:

Correcting severe uraemia.

Treating anaemia when relevant.

Avoiding unnecessary antiplatelet or anticoagulant exposure where possible.

Dialysis when bleeding is clinically significant and related to uraemia.

Other specific haemostatic measures may be used depending on the clinical setting.

22. Bleeding as a Dialysis Indication

Clinically significant:

Uraemic bleeding

is an indication for urgent dialysis.

Therefore:

URAEMIA + SIGNIFICANT BLEEDING → CONSIDER URGENT DIALYSIS.

23. Metabolic Acidosis

An important severe complication not included in the original list is:

Metabolic acidosis.

Healthy kidneys normally:

Excrete hydrogen ions

and

Regenerate bicarbonate.

AKI impairs these processes.

24. Consequences of Severe Acidosis

Severe metabolic acidosis can cause:

Reduced myocardial contractility.

Hypotension.

Reduced responsiveness to catecholamines.

Respiratory compensation with rapid breathing.

It can also worsen:

Hyperkalaemia.

25. Acidosis and Dialysis

If metabolic acidosis is:

Severe

and

Refractory to appropriate medical treatment,

particularly when causing haemodynamic compromise, dialysis may be required.

Therefore:

SEVERE REFRACTORY METABOLIC ACIDOSIS → URGENT DIALYSIS.

26. Uraemic Encephalopathy

Another important severe complication is:

Uraemic encephalopathy.

Accumulation of uraemic toxins can impair cerebral function.

27. Clinical Features of Uraemic Encephalopathy

Possible features include:

Confusion.

Poor concentration.

Drowsiness.

Asterixis.

Altered consciousness.

Seizures in severe cases.

28. Uraemic Encephalopathy and Dialysis

Uraemic encephalopathy is a major indication for:

Urgent dialysis.

Therefore:

URAEMIA + ENCEPHALOPATHY → URGENT DIALYSIS.

29. Uraemic Pericarditis

Severe uraemia can also cause:

Pericardial inflammation.

This is called:

Uraemic pericarditis.

30. Clinical Features of Uraemic Pericarditis

Possible features include:

Chest pain.

Pericardial friction rub.

Pericardial effusion.

A large effusion may progress to:

Cardiac tamponade.

31. Uraemic Pericarditis and Dialysis

Uraemic pericarditis is another strong indication for:

Urgent kidney replacement therapy.

Therefore:

URAEMIC PERICARDITIS → URGENT DIALYSIS.

32. Other Electrolyte Abnormalities

AKI may also cause abnormalities in:

Phosphate.

Calcium.

Magnesium.

Hyperphosphataemia is common as phosphate excretion falls.

Calcium may fall, particularly in advanced renal dysfunction.

These abnormalities are important, although usually less immediately dangerous than severe hyperkalaemia.

33. Hyponatraemia

Excess water retention may cause:

Dilutional hyponatraemia.

Severe or rapidly developing hyponatraemia can cause neurological symptoms, although sodium abnormalities in AKI depend greatly on fluid intake and the underlying illness.

34. Infection and Sepsis

Sepsis is a major cause of AKI and can also complicate the course.

Patients with severe AKI are often critically ill and may have:

Impaired immune function.

Invasive lines or catheters.

Prolonged hospitalisation.

These factors increase infection risk.

35. Cardiovascular Complications

AKI can stress the cardiovascular system through:

Hyperkalaemia.

Acidosis.

Fluid overload.

Hypertension or hypotension.

This can precipitate:

Arrhythmias.

Heart failure.

Pulmonary oedema.

Haemodynamic instability.

36. Neurological Complications

Severe AKI and uraemia may cause:

Confusion.

Encephalopathy.

Asterixis.

Seizures.

Neurological dysfunction should raise concern for:

Severe uraemia

and possible need for dialysis.

37. Gastrointestinal Manifestations of Uraemia

Severe uraemia can produce:

Anorexia.

Nausea.

Vomiting.

These symptoms can worsen:

Nutrition

and

Volume depletion.

Persistent severe uraemic symptoms may contribute to the decision to begin kidney replacement therapy.

38. Severe AKI Complications – Note Form

Hyperkalaemia:

Reduced renal potassium excretion.

Risk of fatal arrhythmia.

Severe/refractory cases may require dialysis.

Pulmonary oedema:

Sodium and water retention.

Breathlessness and hypoxaemia.

Refractory pulmonary oedema is an urgent dialysis indication.

Intravascular volume depletion:

Reduced circulating volume.

Reduced renal perfusion.

Can worsen pre-renal AKI and lead to tubular injury.

Volume overload:

Oedema.

Raised JVP.

Hypertension.

Pulmonary oedema.

Bleeding:

Uraemic platelet dysfunction.

Platelet count may be normal.

Clinically significant uraemic bleeding may require dialysis.

Metabolic acidosis:

Reduced renal acid excretion.

Can worsen hyperkalaemia and cardiovascular instability.

Severe refractory acidosis may require dialysis.

Uraemic encephalopathy:

Confusion.

Drowsiness.

Asterixis.

Seizures.

Urgent dialysis indication.

Uraemic pericarditis:

Chest pain.

Pericardial rub.

Effusion.

Urgent dialysis indication.

39. Important Corrections to the Original Notes

The term:

“ARF”

should now generally be replaced by:

ACUTE KIDNEY INJURY – AKI.

The original list includes:

“Intravascular volume depletion/overload.”

This is important, but these are opposite states and should be separated clinically:

VOLUME DEPLETION → REDUCED RENAL PERFUSION.

VOLUME OVERLOAD → OEDEMA/PULMONARY OEDEMA.

The original complication:

“Bleeding”

is best understood as:

URAEMIC PLATELET DYSFUNCTION.

The platelet count may be normal despite impaired haemostasis.

The original list should also include two major severe complications:

SEVERE METABOLIC ACIDOSIS

and

URAEMIC ENCEPHALOPATHY/PERICARDITIS.

Key Clinical Pattern

The severe complications of AKI can be remembered as:

POTASSIUM → HYPERKALAEMIA.

FLUID → DEPLETION OR OVERLOAD.

LUNGS → PULMONARY OEDEMA.

ACID → METABOLIC ACIDOSIS.

URAEMIA → ENCEPHALOPATHY + PERICARDITIS + BLEEDING.

The complications most likely to trigger urgent dialysis are:

REFRACTORY HYPERKALAEMIA.

REFRACTORY PULMONARY OEDEMA.

SEVERE REFRACTORY METABOLIC ACIDOSIS.

SYMPTOMATIC URAEMIA – especially encephalopathy, pericarditis or significant bleeding.