Renal: AKI

Question 1

How is AKI staged?

Answer 1

1 = baseline Cr, rise of 26.5 micro mol/L

2 = baseline Cr doubles

3 = baseline Cr triples

Question 2

What causes AKI?

Answer 2

Pre-renal = hypovolaemic, burns, sepsis

Intra-renal = GN, vasculitis, ATN

Post renal = renal stones, prostate/bladder pathology

Question 3

What are symptoms and signs of AKI?

Answer 3

Headache, nausea, sickness, unwell

Reduced BP or HTN

Oliguria or anuria

Deranged bloods = increased Cr, increased K

Altered breathing

Oedema

Anaemia

Systemic = joint pain, fever, rash, leg weakness, palpitations

Question 4

How should AKI be investigated?

Answer 4

Assess vol status = JVP, mucous membrane, chest auscultation, sacral/peripheral oedema

Passing urine?

Urine dip

Bladder scan

Monitor daily input/output

Daily weights

CXR

Bloods = FBC, U+E, bone, bicarb, CK, CRP, LFT

VBG

Question 5

What pts are at risk of AKI?

Answer 5

Aged >65

Background CKD

Sepsis

Critical illness

Burns

Cardiac surgery

Nephrotoxic meds (NSAIDs, radio-contrast)

DM

Cancer

Anaemia

Dehydrated

Question 6

How should hyperkalaemia in AKI be managed?

Answer 6

Bloods + ECG (Tall tented T waves, flattened P waves, increased PR interval, wide QRS)

1. Ca gluconate (give with ECG changes or >6.5) - 10mls 10% over 5 mins
2. Insulin - dextrose (insulin moves glucose intracellularly that takes with it K, dextrose to replace loss) 10U insulin with 50ml 50% dex (25mg)
3. Salbutamol neb
4. Calcium resonium
5. Sodium bicarb (SEVERE ACIDOSIS) - 8.4%
6. Perform another ECG, VBG
7. Dialysis for refractory hyperkalaemia, CKD

Question 7

What is ‘DONUT’?

Answer 7

D = Dehydration: Optimise fluid status. Aim for minimum SBP>100 mmHg

• Dry = give IV fluids (caution in HF)
• Euvolaemic = PO intake, bladder scan
• Overloaded = stop fluids, CXR, diuretics

O = Obstruction: US renal tract and catheterise only if appropriate

N = Nephrotoxins: stop offending drugs (diuretics, ACEi, ARB, NSAIDs, Gentamycin, Trimethoprim, IV contrast, metformin - lactic acidosis)

U = Urine: Output: Ensure strict fluid balance is documented Analysis: positive leucocytes and nitrates, send off urine sample for MSU prior to starting antibiotics. Protein positive→ Request urine protein:creatinine ratio, if high seek renal advice

T = Think: Remember AKI is not a diagnosis- what is the underlying cause? If no UTI but positive blood and protein in urine, think of a systemic cause. Seek senior advice, contact nephrology. Check U/Es daily

Question 8

How would you carry out a fluid assessment on a patient?

Answer 8

• BP (90/60 - concern)
• Kidney disease (electrolyte imbalance)
• Dehydration (dry mouth, sunken eyes, dry mucous membranes)
• Urine output (normal = 1/2ml per kg per hour)
• Heart failure (overload = oedema)
• 3rd heart sound = early diastolic murmur (vol overload)
• 4th heart sound = auscultation in the ventricles
• Cap refill = normal is <2 secs
• Urea/creatinine = good measure of renal function
• Regular monitoring of pt weight (once a week)
• Hepatomegaly = vol overload
• Taut, non-pliable skin = interstitial fluid excess

Question 9

What hormones regulate fluid balance in the body?

Answer 9

ADH = from posterior pituitary, promotes water reabsorption via aquaporins

Aldosterone = promotes Na reabsorption in DCT + CD (sets gradient for H2O)

ANP (atrial natriuretic peptide) = released by cardiac tissue in response to stretch

Renin = produced by the kidneys in response to low perfusion