17. Oliguria In The Postoperative Patient

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17. Oliguria In The Postoperative Patient

  1. 1. Oliguria In a Post-Operative Patient Alok Narayan Med VI
  2. 2. Urine Output <ul><li>Oliguria- Urine output <1 ml/kg/h </li></ul><ul><ul><li><400ml/day, but this is less accurate </li></ul></ul><ul><ul><li>Often reversible, but may be a sign of ARF </li></ul></ul><ul><li>Anuria- </li></ul><ul><ul><li><100ml/day </li></ul></ul><ul><ul><li>Decreased UOP is usually not a </li></ul></ul><ul><ul><li>concern unless ARF is also present. </li></ul></ul>
  3. 3. What is ARF <ul><li>Significant (>50%) decrease in GFR with an associated accumulation of nitrogenous wastes (BUN & Creatinine) in the body (a.k.a. azotemia) </li></ul><ul><ul><li>Serum creatinine provides the most accurate and consistent estimation of GFR. </li></ul></ul><ul><ul><ul><li>ARF=Serum creatinine ↑ >0.5mg/dl (Normal=0.8-1.4) </li></ul></ul></ul><ul><li>Early sign of ARF is oliguria. </li></ul><ul><ul><li>Only seen in 2/3 of ARF pts. </li></ul></ul>
  4. 4. Etiology <ul><li>Prerenal - 70% and COMMONEST CAUSE OF OLIGURIA </li></ul><ul><ul><li>Kidney hypoperfusion due to: </li></ul></ul><ul><ul><ul><li>Absolute decrease in blood volume (Dehydration, hemorrhage, GI losses, ↓ PO) </li></ul></ul></ul><ul><ul><ul><li>Relative decrease in blood volume (sepsis, vasodilatory drugs, renal artery stenosis) </li></ul></ul></ul><ul><li>Intrinsic </li></ul><ul><ul><li>Parenchymal injury due to: </li></ul></ul><ul><ul><ul><li>Acute Glomerulonephritis </li></ul></ul></ul><ul><ul><ul><li>Interstitial Nephritis </li></ul></ul></ul><ul><ul><ul><li>Acute Tubular Necrosis (ischemia, drugs, or toxins) </li></ul></ul></ul><ul><li>Postrenal </li></ul><ul><ul><li>Obstruction due to </li></ul></ul><ul><ul><ul><li>Calculi, Tumor, Obstructed Foley Catheter </li></ul></ul></ul>
  5. 5. Post-Op Oliguria <ul><li>Often a patient will have a diminished urine output after a major operation. This may be the result of fluid and blood loss and d/t response of the adrenal cortex to stress - there is an increase in aldosterone release (adrenal cortex) and ADH release (posterior pituitary) in the first 24 hours after surgery. This results in both salt and water retention. </li></ul><ul><li>The oliguria should be temporary and not last more than 24h. If there is a urine output of less than 400ml in the first 24 hours then this warrants investigation. </li></ul>
  6. 6. Assessing Oliguria <ul><li>Review patient immediately </li></ul><ul><li>Assess need for urgent resuscitation </li></ul><ul><li>- ABCs </li></ul><ul><li>Immediate Questions </li></ul><ul><li>1) Does the patient have any symptoms or predisposing conditions that suggest hypovolemia? </li></ul><ul><ul><li>Diarrhoea, vomiting, GI bleeding, high fever, low intake (whether oral or IV) </li></ul></ul><ul><ul><li>Positional dizziness suggests hypo-volaemia </li></ul></ul><ul><ul><li>If post-op: bleeding, wound drainage, infection leading to septicemia </li></ul></ul><ul><li>2) Previous symptoms to suggest bladder outlet obstruction from prostatic hypertrophy? </li></ul><ul><ul><li>Hesitancy, difficulty voiding, dribbling </li></ul></ul><ul><ul><li>i.e. post renal obstruction </li></ul></ul><ul><li>3) History of hematuria? </li></ul><ul><ul><li>Renal stones can lead to obstruction </li></ul></ul><ul><li>4) Is the patient likely to be suffering from acute renal failure? </li></ul><ul><ul><li>Previous Hx </li></ul></ul><ul><ul><li>Renal disease </li></ul></ul><ul><ul><li>Nephrotoxic drugs (aminoglycoside AB’s and NSAIDs) </li></ul></ul><ul><ul><li>Exposure to nephrotoxic agents (contrast, chemotherapy) </li></ul></ul><ul><li>5) Any underlying diseases/procedures that could result in oliguria? </li></ul><ul><ul><li>Cardiac failure, cirrhosis, epidural infusion </li></ul></ul><ul><li>6) Symptoms suggestive of uremia? </li></ul><ul><ul><li>Nausea, vomiting, anorexia, insomnia, mental status changes </li></ul></ul>
  7. 7. Physical examination <ul><li>Vital signs - ABCs </li></ul><ul><li>decrease in weight suggests volume depletion </li></ul><ul><li>Hypertension (volume overload or if long standing can cause renal insufficiency) </li></ul><ul><li>Check orthostatic BP </li></ul><ul><li>Irregularly irregular pulse suggests atrial fibrillation (a common cause of emboli) </li></ul><ul><li>Skin </li></ul><ul><li>Decreased skin turgor, dry mucous membranes suggest hypovolemia </li></ul><ul><li>Neck </li></ul><ul><li>Flat neck veins while supine suggest volume depletion </li></ul><ul><li>Raised JVP in volume overload </li></ul><ul><li>Chest </li></ul><ul><li>rales suggest CHF </li></ul><ul><li>Abdomen </li></ul><ul><li>ascites (cirrhosis) or distended bladder (outlet obstruction) </li></ul><ul><li>Genitourinary </li></ul><ul><li>PR for males’ prostate </li></ul><ul><li>Pelvis for females (feel for masses) </li></ul><ul><li>Extremities </li></ul><ul><li>assess perfusion (colour, capillary refill, temp.) </li></ul>
  8. 8. Lab data <ul><li>Urinalysis </li></ul><ul><li>high specific gravity suggests volume depletion </li></ul><ul><li>large amounts of protein or red cell casts suggests glomerular disease </li></ul><ul><li>significant hematuria (renal embolisation or stones) </li></ul><ul><li>WBC casts (infection or sever inflammation) </li></ul><ul><li>Frequent granular casts (acute tubular necrosis) </li></ul><ul><li>Serum chemistries </li></ul><ul><li>compare blood urea and creatinine </li></ul><ul><ul><li>if ratio >10:1, prerenal cause is likely but could also be obstruction, GI bleeding, severe catabolic states </li></ul></ul><ul><ul><li>If ratio <10:1 renal cause is likely </li></ul></ul><ul><li>always note high/low sodium or high potassium which can complicate acute renal failure </li></ul><ul><li>Urine electrolytes and creatinine </li></ul><ul><li>Urinary sodium <15mmol/L suggests pre-renal…….. >20 suggests renal </li></ul>
  9. 9. Management of Oliguria <ul><li>Minimal acceptable output is 1 mL/kg/hr </li></ul><ul><li>Take records of fluid intake and output </li></ul><ul><li>Review meds and stop all nephrotoxic drugs (Aminoglycosides, NSAIDS, COX-2 inhibitors) </li></ul><ul><li>Adjust doses of renally excreted drugs </li></ul><ul><li>Address all the Septic Foci (ABx, surgical drainage, UTI) </li></ul>
  10. 10. Mx of Oliguria…. <ul><li>Pre-renal </li></ul><ul><li>Volume challenge (i.e. 500mL NS for 30 mins) </li></ul><ul><li>Monitor volume replacement to ensure circulatory adequacy (i.e. use arterial and R. heart catheters to measure CVP to be above 10mmHg) </li></ul><ul><li>Follow hourly urine output (w a catheter in place) </li></ul><ul><li>Consider additional measures (some doctors may disagree with this) </li></ul><ul><ul><li>Frusemide (but usually reserved for fluid overload) </li></ul></ul><ul><li>Renal causes </li></ul><ul><li>Consider frusemide and mannitol </li></ul><ul><li>Emergency dialysis in the following: </li></ul><ul><ul><li>Severe hypovolemia unresponsive to diuretics </li></ul></ul><ul><ul><li>Intractable acidosis </li></ul></ul><ul><ul><li>Severe hyperkalemia </li></ul></ul><ul><ul><li>Pericarditis secondary to uremia </li></ul></ul><ul><ul><li>Severe uremic symptoms or encephalopathy </li></ul></ul><ul><li>Post Renal causes </li></ul><ul><li>Place a catheter, if immediate flow starts then urethral obstruction is very likely </li></ul><ul><li>If catheter already present, replace or irrigate it as it could be obstructed </li></ul><ul><li>Consult a urologist </li></ul>
  11. 11. Oliguria/ARF Systemic Complications <ul><li>Infections of urinary tract & lungs due to uremia </li></ul><ul><ul><li>Up to 70% of pts. with ARF. </li></ul></ul><ul><ul><li>#1 cause of ARF morbidity/mortality </li></ul></ul><ul><li>Anemia </li></ul><ul><ul><li>Kidney makes EPO, ↓ EPO  anemia (HCT 20-30) </li></ul></ul><ul><li>“ 3 rd space disease” </li></ul><ul><ul><li>Salt and Water retention (esp. in pre-renal failure) </li></ul></ul><ul><ul><li>Pulmonary edema, Pleural effusion, & ascites </li></ul></ul><ul><li>Hypocalcemia </li></ul><ul><ul><li>↓ excretion of phosphate  impaired GI absorption of Calcium. </li></ul></ul><ul><li>Hyperkalemia </li></ul><ul><ul><li>↓ glomerular filtration, ↓ tubular secretion </li></ul></ul><ul><ul><li>Malaise, nausea, and muscle weakness. </li></ul></ul><ul><ul><li>A cardiac emergency </li></ul></ul><ul><li>Metabolic Acidosis w/ ↑ anion gap </li></ul><ul><ul><li>↓ excretion of acids & ↓ tubular reabsorption of bicarbonateresults in metabolic acidosis with a high anion gap. </li></ul></ul><ul><ul><li>Hypotension, Kussmaul’s respirations </li></ul></ul>
  12. 12. Important Facts <ul><ul><li>Oliguria in an alert patient that is associated with normal pre-existing renal function and cardiovascular stability, is unlikely to require intervention unless it persists for four hours or more. So, wait and see… </li></ul></ul><ul><ul><li>If oliguria is associated with other symptoms or signs suggestive of fluid depletion, it should be treated initially with a fluid challenge. </li></ul></ul><ul><ul><li>In all cases of oliguria it is important to exclude obstruction of the urinary tract or urinary catheter. </li></ul></ul><ul><ul><li>Diuretics should not be used to treat oliguria and should be reserved for fluid overload. </li></ul></ul><ul><ul><li>Dopamine should not be used to treat oliguria or to prevent renal failure. </li></ul></ul>

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