nephrology clearance

Nephrology Clearance

Dr. JC E. LorenDept. of Internal Medicine

Southern Philippines Medical CenterFebruary 14, 2011

PRE-OPERATIVE PREPARATIONS

I. FLUID STATUSAND EXTENT OF UREMIAA. FLUID STATUS

- Avoid OVERHYDRATION- Avoid DEHYDRATION

B. EXTENT OF UREMIA- affects platelet function, fibroblast response to tissue injury, and the immune system- for elevtive procedure:

Dialysis 12-24 hours before the planned surgeryAdvisable to have 2-3 sessions of dialysis before the procedure to ensure a well dialyzed statusWatch out for dehydration, hypokalemia AND

II. ELECTROLYTE DISORDERS

A. SERUM POTASSIUM LEVEL- should be at the lower range of normal (4 meq/L)- prevention of hyperkalemia:

> furusemide> salbutamol nebulization> Regular Insulin + D5 water> Kalimate sacchet

- post dialysis potassium prior to surgery should be 3.0 (dialysate should contain at least 2 meq/L)


• A. SERUM POTASSIUM LEVEL- special cases like patients on: DIGITALIS/HEMODYNAMICALLY UNSTABLE PATIENTS ------- higher K on the dialysate is recommended (3 meq/L)- in severely catabolic/bleeding patients, the rate of rise in the serum potassium value is greater than 1.0 – 1.5 meq/L/day. AGGRESSIVE LOWERING OF POTASSIUM IS WARRANTED - prevention of hypokalemia to prevent arrythmia during anesthesia induction


B. SERUM SODIUM LEVEL> mild hyponatremia is common in seriously ill patients> use of dialysate high in sodium> avoid hypotonic solution

III. ACID BASE STATUS

GOALS: 1. correct pH rather than the HCO3 level2. mild preoperative acidosis is safer than alkalosis

IV. HEMATOCRIT LEVEL AND COAGULATION PROFILE

Hct level: minimum of Hct at 20 – 35% is acceptable

If time permits, prior to major surgical procedure, the Hct should be corrected by erythropoietin therapy


• COAGULATION– Uremic platelet dysfunction and deficient platelet -

vessel wall interaction– The best screening test is Bleeding Time– Measures to shorten the BT:

• A course of intensive hemodialysis or PD to maximize reversal of the uremic state

• Administration of desmopressin (DDA VP), cryoprecipitate, or coagulated estrogen

• Transfusion of red cells or the administration of ERYTHROPOIETIN to raise the hematocrit to at least 30%


Drugs that inhibit platelet function

- aspirin and dipyridamole must be avoided for at least 2 weeks prior to surgery


• Heparin effects from previous dialysis:– Heparin t½ is beteewn 1 – 2.5 hrs– Defer surgery at least 12 hours from the last

dialysis (which used heparin)– For emergency surgery, dialyzed the patient

without heparinization – No problem with PD

INTRAOPERATIVE

1. PROTECTION OF THE VASCULAR ACCESS2. ANESTHESIA

A. PREMEDICATION- commonly used drugs (diazepam, atropine, fentanyl) can be used in normal dosage in dialysispatients- best to check the pharmacokinetics to detremine if a dosage reduction is required

INTRAOPERATIVE

B. MUSCLE RELAXANTSNon- depolarizing:

> Tubocurarine, the least affected by the renal failure but the duration of action is still prolonged> Gallamine should not be used because its elimination is completely dependent on the kidneys > Metocurine, pancuronium may offer certain hemodynamic advantage over curare but their half lives are greatly prolonged in renal failure

INTRAOPERATIVE

B. MUSCLE RELAXANTSDepolarizing:

> Succinylcholine can be given in usual dosage but closely monitor the potassium (the drug causes intracellular K release)

> Decamethonium should be used with great caution

INTRAOPERATIVE

ANESTHETIC AGENTS:Can be safely given in renal failure without

dose adjustment: HALOTHANE and NITROUS OXIDE

Enflurane and methoxyflurane should be avoided since its metabolite yield OXALATE and FLUORIDE (NEPHROTOXIC)

INTRAOPERATIVE

3. FLUID AND ELECTROLYTE MANAGEMENT– Most patients with renal failure have heart disease– Volume status and cardiac filling pressure need to

be carefully monitored– Potassium-containing IV fluids should not be given

routinely intra-op

4. INTRAOPERATIVE HEMODIALYSIS- for patients undergoing bypass

POST-OPERATIVE

meticulous monitoring of fluid and electrolyte balance

decision whether hemodialysis is necessary should be made on a daily basis

any dialysis post op especially from vascular or ophthalmic surgery should be done without using heparin

Common problems encountered post-op are:

I. HYPERKALEMIA– Dialysis for K > 6 meq/L– URGENT therapy for life threatening hyperkalemia:

– NaHCO3– Clucose + insulin– Albuterol(Reduction of K level ranges from 0.5 to 1.0 meq/L, duration of effect

is 2 hours)

II. HYPERTENSION - Refelects increased volume- Withdrawal of antihypertensive drugs


III. HYPOTENSION- reflects the hemorrhage or fluid deprivation due to preoperative dehydration - pericardial effusion

IV. FEVER- any fever persisting 24-48 hours after surgery may be an indication of infection - uremic patients are in the state of immunodepression- careful adjustment of antimicrobial dose and to the metabolic load associated with administration of certain of these drugs


VI. PULMONARY- dialysis patients have stiff hypertrophied hearts that require a relatively high filling pressure for optimal function but at the same time suffer from the increased capillary permeability (due to uremia)------- PULMONARY EDEMA

ANEMIA OF RENAL FAILURE

Erythropoetin therapy (EPOTEIN ALPHA or BETA)Uses: restores erythropoiesis brings back to normal the electrocyte survival and

viability increases elasticity, deformability and antioxidant

enzymatic system of RBChigher Red Cell superoxide dismutase/total glutathione

peroxidaseuremic BT shortened

ANEMIA OF RENAL FAILURE anemia starts to occur once GFR is down to 20-35ml/min 7% of patients with renal failure DO NOT need treatment

for anemia normal EPO level: 8-18 mu/cc goal of therapy: Hct 28-33% Recommended dose: 50-300 IU/kg 3x a week T1/2 of IV = 4-13 hours T1/2 of SQ = 24 hours EPO Alpha and Beta differs in their oligosaccharide

moiety (more in Alpha) but NO difference in pharmacokinetics and efficacy

DRAWBACK IN EPO THERPY: EXACERBATION OF HYPERTENSION

Recommendation: can occur during the first 4 months of therapy

while the Hct is increasing avoid rate of rise in the Hgb of >3 g/dl in any 4

week period each time dosage is increased, the increment

shou8ld not exceed 30 IU/kg 3x a week reason for the Hypertension:

- Correction of Hct losses the reactive vasodilatation broughtn about by chronic hypoxemia of anemia

EFFECT OF RENAL FAILURE ON HEMOSTASIS

BLEEDING TIME is a predictor of bleedingPlatelet are adequate in renal failure but

function is impaired

UREMIA = BLEEDING TENDENCY AND THROMBOSIS

I. BLEEDING TENDENCY IN UREMIA Associated with excessive formation of NO NO inhibits platelet aggregation Stimulation of TNF alpha and IL-1 beta CRD (defect in platelet function):

Decreased total platelet gp!b Defect in gp 11b – III a complex

II. ABNORMALITY OF COAGULATION AND FIBRINOLYSIS: (thrombotic tendency) increased Fibrinogen (activates fibrinolysis) Increased Factor VIII – C Decreased antithrombin C Decreased protein S and C

nephrology clearance

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