Anesthesia and renal disease
Physiology
• Regulation
– Volume & composition of body fluids
– Elimination of toxins
Physiology
• Endocrine function
– Renin-Angiotensin-Aldosterone
– Erythropoietin
– Vitamin D and Ca++ homeostasis
– Insulin metabolism
Physiology
• Glomerular Filtration Rate (GFR)
– 125ml/min
– 90% reabsorbed
• GFR = Kf where
• Kf = (PGC-PBC) – (πGC- πBC)
– P = Hidrostatic pressure, π = Oncotic pressure
– GC = glomerular capillary, BC = Bowman capsule
Physiology
• Renal bloodflow (RBF)
– 25% of cardiac output
– Cortex = 66%
– Medulla 33%
– Autoregulated between 60 – 160mmHg
• ↓RBF = ↓Cl-
– Stimulate JXA →R-A-A
– Stimulate sympathetic system
Evaluation of renal function
• Urea
• Creatinine
• Creatinine clearance
• Fractional excretion of Na+
• Other
– Proteinuria, hematuria, MCS, ultrasound, CT MRI,
Effects of anesthesia on renal
function
• ↓ GFR as ↓ CO
– Induction agents, volatiles
• Autoregulation remains intact
• Stress response = ↑ADH = concentrated urine
• IPPV = ↑ atrial pressure = ↓ ANP = ↓Na+
excretion ↓
Direct nefrotoxic effects
• Enflurane
– Long exposure (9.6 MAC hours)
– ↑ Free fluoride inhibits tubular function
– ↓ Cl- transport in ascending loop
– concentation defect
– high output renal failure resistant to vasopressin
Direct nefrotoxic effects
• Sevoflurane
– 2-5% liver metabolism = free F-
– Potentially nefrotoxic
Direct nefrotoxic effects
• Sevoflurane
– Low flow in Baralime
– Degradation = Compound A
– β lyase ↓
– Nefrotoxic metabolite
• Rare in humans
– 10% β lyase activity
Perioperative renal failure
• Co-existing renal disease
• Hypovolemia
• Liver cirrhosis
• Sepsis
• Multi organ trauma
• Congestive cardiac failure
• Abdominal aneurism resection
• Cardio pulmonary bypass
• Advanced age
Chronic renal failure
• Anemia
• Pruritis
• Coagulopathies
• Altered hydration and e- balance
• Metabolic acidosis
• Systemic hypertension
• Increased susceptibility to infections
Chronic renal failure:
Anemia
• Decreased erythropoietin production
• Increased cardiac output
– Hyperdynamic circulation
• OHEC shifts to right
• Tolerate Hb > 6 for surgery
– Transfusion → fluid overload
– Erythropoietin → worsen hypertension
Chronic renal failure:
Pruritis
• Sign of end stage disease
– ↑ circulating levels of histamine
– Erythropoietin may↓ [histamine]
Chronic renal failure:
Coagulopathies
• Defective platelet function
• Defective vWF
• Systemic heparinisation for dialysis
Chronic renal failure:
Altered hydration
• Unpredictable volume status
– Overload
– Hypovolemic after dialysis
• Disequilibrium syndrome
– CNS symptoms post dialysis due to more rapid
lowering of extracellular osmolarity tha
intracellular
Chronic renal failure:
Hyperkalemia• K+> 5.5
• ECG changes neccesitates Rx
– Peaked T waves
– Prologation PR time, ORS complex
– Heart block
• Rx
– Hyperventilation
– Insulin and glucose
– CaCl2 (physiological antagonist)
Chronic renal failure:
Hypocalcemia
• ↓GFR = ↑PO4 = ↓Ca++
– Hypocalcemia = ↑PTH = bone resorption
– Renal osteodystrophy
• ↓ 1,25 DHCC production
– ↓intestinal absorbsion of Ca++
Chronic renal failure:
Hypermagnesemia
• Oral Mg++ containing antacids
– CNS depression
– Potentiation of muscle relaxants
Chronic renal failure:
Metabolic acidosis
• ↓ GFR = decreased H+ excretion
• pH < 7.35
– Hyperventilation (compensatory)
– ↓ neuromuscular responsiveness
Chronic renal failure:
Hypertension
• Activation of R-A-A
– Vasoconstriction (to increase renal blood flow)
– Retention of fluid (due to aldosterone)
• Fluid overload
• Rx
– ACE inhibitors / ARB
– Ca++ channel antagonists
Chronic renal failure:
Hypertension
• >80% of all renal patients
• Most significant risk factor for
– Congestive cardiac failure
– Myocardial infarction
– Stroke
Chronic renal failure:
Pericardial disease
• Pericardial effusion +/- tamponade
• Due to uremia
• Acute tamponade
– Life threatening
– Rx= pericardiocentesis, dialysis.
Chronic renal failure:
Central cervous system
• Encephalopathy
– Depression
– Sedation
– Coma
• Seizures
– Acute hypertension, brain edema
Chronic renal failure:
Peripheral nervous system
• Distal symmetric mixed polyneuropathy
– Median, Peroneal
Chronic renal failure:
Autonomic nervous system
• Cardiac
– Resting tachycardia
– Attenuated response to hypovolemia, IPPV
– Orthostatic hypotension
• GIT
– Delayed gastric emptying
Chronic renal failure:
Infection
• Most common cause of death
• High risk
– Decreased phagocyte activity Immunosuppressant
drugs.
– Frequent transfusions – Hep B & C, HIV
• Strict aseptic placement of IV lines
Preoperative evaluation
• Etiology of renal failure
• Estimate daily urine production
• Dialysis
– Type
– Frequency
– Side effects
– Time of last dialysis
Preoperative evaluation
• Note any systemic manifestations of uremia
– Cardiovascular, pulmonary
– Bleeding diathesis
– Sepsis
– Neuropathy, encephalopathy
– Hydration status
– Note presence of A-V fistulas
Preoperative dialysis
• Fluid overload
• Hyperkalemia
• Metabolic acidosis.
• Pericarditis
• Coagulopathy
• Drug toxicity
• Refractory GIT symptoms
Preoperative preparation
• Transfuse
– only if Hb < 6
– Extensive surgery with ↑ blood loss
Preoperative preparation
• Correct platelet dysfunction
– DDAVP 0.3mg/kg IV
• Hypertension
– Multidrug therapy
– 170/100 mmHg acceptable
Preoperative preparation
• Hyperkalemia
– Glucose-insulin infusion
– CaCl2
– Kayexilate
– Emergency dialysis
• Premedication
– Midazolam if necessary
Preoperative preparation
• Wear gloves, masks
• Prevent hypothermia
• A-V fistulas
– No IV lines
– No blood pressure cuffs
Induction of anesthesia
• Pre-oxygenate
• Careful fluid load
– Especially after dialysis
• Lower dose induction agent
– ↑ free fraction = ↓albumin, acidosis
– Ketamine useful
Induction of anesthesia
• Rapid sequence induction
– Suxamethonium safe if K+ < 5.5 mmol
– Modified RSI with atracurium, cis-atracurium
• Avoid steroid relaxants
– dependant on renal excretion
– vecuronium has active metabolite (10%)
– recurarisization
Maintenance of anesthesia
• Safe vapours
– Isoflurane, desflurane
• Avoid
– Enflurane = inorganic fluoride production
– Sevoflurane = Compound A
– Halothane = dysrhythmias
– N2O = decreased O2 delivery in severe anemia
Maintenance of anesthesia
• Narcotics
– Short acting, lower doses
• Accumulation
– Morphine-6-glucuronate prolonged effect
– Nor-pethidine = seizures
Intra operative problems
• Hypertension
– Direct vasodilators, B blockade to decrease BP
• Exaggerated hypotension
– Relatively small fluid losses
– Deep anesthesia
• Dysrhythmias
• Excessive bleeding
Post operative problems
• Delayed awakening
• Nausea and vomiting
• Hypertension
• Respiratory depression
• Pulmonary edema
Conclusion
• Multi system disease
• Increased risk of peri-operative morbidity and
mortality
• Handle with care!