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!