Renal Physiology

Question 1

What are the common causes of end stage renal failure?

Answer 1

• Diabetes mellitus
• Glomerulonephritis
• Hypertension
• Polycystic kidney disease
• Pyelonephritis
• Renal vascular disease

Question 2

What history and examination findings would be important to know about a patient with end stage renal failure undergoing an operation?

Answer 2

History
- Cause of renal failure
- Any symptoms of ischaemic heart disease
- Dry weight, fluid restriction and whether they pass any urine normally
- Timing of dialysis
- Current medications
- Evidence of delayed gastric emptying, if diabetic

Examination
- Current fluid status
- Site of fistula
- Assessment of venous access, avoiding fistula site

Question 3

What investigations would be useful preoperatively in an end stage renal failure undergoing surgery?

Answer 3

• ECG
  
  • Blood pressure
  • Full blood count and electrolytes
  • Arterial blood gas
  • Chest xray

Question 4

How would a radial arterio-venous fistula affect your anaesthetic management?

Answer 4

• Cannula on other arm/limb
  
  • Positioning and protecting the limb from pressure
  • Non invasive blood pressure measurements from other arm

Question 5

What targets would you aim for during a kidney transplant?

Answer 5

• Mean arterial blood pressure at least 90mmHg to ensure adequate perfusion
  
  • Normotension, particularly when cross clamp removed
  • Avoid fluid overload, aim for normovolaemia to optimise cardiac function
  • Aim for central venous pressure of 12-14mmHg

Question 6

What analgesic agents should you avoid using in renal transplant patients?

Answer 6

Non steroidal anti-inflammatories reduce renal blood flow and exacerbate renal toxicity by cyclosporin

Question 7

A renal patient is given intravenous sodium bicarbonate, however the cannula tissues, and the patient develops painful swelling around the site.

What are your management options?

Answer 7

The aim is to dilute the irritant drug

Saline irrigation and washout
Hyaluronidase to encourage spread throughout the tissue to dilute the bicarbonate solution
Steroids to reduce inflammation

Question 8

What are the ECG features of hypokalaemia?

Answer 8

• T wave inversion (and flattening)
• S-T depression
• Q-T prolongation
• P-R prolongation
• U waves
• PEA

Question 9

What is the highest rate at which potassium can be replaced safely?

Answer 9

40mmol/hour