23. Chronic Renal Failure Flashcards
Stages of CKD
G1 ≥90 Normal or high
G2 60 to 89 Mildly decreased
G3a 45 to 59 Mildly to moderately decreased
G3b 30 to 44 Moderately to severely decreased
G4 15 to 29 Severely decreased
G5 <15 Kidney failure (add D if treated by dialysis)
You are asked to anaesthetise a 40-year-old patient with chronic renal
failure on haemodialysis for repair of a recurrent left inguinal hernia.
What anaesthetic problems do these patients present?
Renal patients have multiple medical problems that impact on anaesthesia.
These include
anaemia,
coagulation disorders,
cardiovascular pathology and
disorders of other body systems.
They also have altered drug handling.
Anaemia
Normochromic, normocytic (usually )
Multifactorial causes:
Iron deficiency due to repeated blood loss
with haemodialysis and associated peptic ulcer disease.
B12 and folate deficiency due to poor diet.
Uraemia depresses erythropoietin production.
Uraemia reduces red cell life span.
Enquire about symptoms associated with anaemia, e.g. angina.
Transfusion at Hb<5 g/dl,
or if symptoms are present, has been recommended.
Low haemoglobins are tolerated because of the shift of the oxygen
dissociation curve to the right (↑ 2,3DPG and uraemic acidosis).
NB: Blood transfusion has effects on the immune system that may influence
outcome after future transplantation.
Blood clotting
Patients with end-stage renal failure have abnormalities of
platelet function due to alterations in arachidonic acid metabolism
and increased NO production.
Defective endothelial release of von Willebrand/Factor VIII complex
is thought to contribute and
may be treated with cryoprecipitate
or DDAVP intra-operatively.
Bleeding time is prolonged.
May have residual heparin from haemodialysis.
Risks and benefits of neuraxial blocks need to be carefully assessed.
i.m. injections may be unwise.
Cardiovascular system
Hypertension Present in 80% of patients –
usually on medication.
Volatiles may exacerbate hypotensive effect.
Exaggerated changes in BP and heart rate with induction and laryngoscopy.
IHD
CCF
Pre-operative ECG, CXR and echocardiogram are necessary.
Carotid bruits – doppler studies may be necessary.
Pericarditis – rare.
Endocarditis – especially if vascular access site is infected.
Vascular access – avoid forearm of non-dominant hand which should be
preserved for a potential shunt.
AV fistulas should be kept warm and protected intra-operatively
Respiratory system
SOB due to anaemia and acidosis.
Pulmonary oedema.
Pulmonary fibrosis associated with medical conditions.
Infection.
Nervous system
Neuropathy – autonomic (especially diabetics)/sensory/motor.
Myopathy due to uraemia causes an exaggerated response to muscle relaxants.
Gastrointestinal system
Delayed gastric emptying makes reflux and aspiration more likely.
Rapid sequence induction may be needed (?modified).
Peptic ulceration.
Pre-medication should include an H2 antagonist.
Endocrine/biochemical
Hypocalcaemia and hypermagnesaemia (antacid consumption) potentiate relaxants.
Blood sugar should be monitored and controlled as many renal patients have diabetes.
Potassium rises in renal failure.
Caution with suxamethonium and potassium containing intravenous fluids (e.g. Hartmann’s).
Renal system
Ideal weight should be known.
A knowledge of daily urine volume normally passed and the dose of diuretic taken.
CVP monitoring may be needed to guide fluid management.
Pre-operative dialysis and knowledge of potassium level post-dialysis.
Intra-operative fluid: Avoid large volumes of crystalloid.
Post-operative fluid: Previous hours urine output plus insensible loss/hr.
How is drug handling altered in renal failure?
Many anaesthetic agents are potentiated in renal failure.
This may be due to:
Decreased protein binding.
Greater penetration of the blood–brain barrier.
Systemic effect of uraemia.
Elimination half-lives are prolonged.
With respect to commonly used drugs:
Propofol pharmacokinetics are unchanged.
Thiopentone and benzodiazepines can de reduced due to reduced protein binding.
Morphine, if used, must be carefully titrated as the metabolite
morphine-6-glucuronide is active and accumulates.
Atracurium is the muscle relaxant of choice (Hofmann degradation).
NSAIDs – avoid.
Isoflurane – safe.
Enflurane – avoid due to potential for nephrotoxicity from fluoride ions.
Conduct of general anaesthesia:
Pre-op: Medical assessment, dialysis, transfuse
Pre-med − antacid.
Intra-op:
Monitoring -
including CMV5,
consider A-line and CVP
Vascular access
Induction – RSI
Attention to pressor response.
Maintenance- IPPV, ↑FiO2, N2O safe.
Attention to fluid balance.
Post-op:
Consider HDU/ICU.
Oxygen should be mandatory.
Types of surgery common in renal patients:
Vascular access procedures
Peritoneal dialysis access
Nephrectomy
Renal transplant
Parathyroidectomy
