The Massachusetts General Hospital Handbook of Neurology

Authors: Flaherty, Alice W.; Rost, Natalia S.

Title: Massachusetts General Hospital Handbook of Neurology, The, 2nd Edition

Copyright 2007 Lippincott Williams & Wilkins

> Table of Contents > Medicine > Kidneys

Kidneys

A. H&P

Fluid intake, drugs (include NSAIDs), urine output, pain. Cardiac exam, kidney tenderness, palpable bladder, edema.

B. Neurological complications of kidney failure

• Uremic encephalopathy:

  • H&P: Renal dz precipitating illness, with obtundation or agitation, myoclonus, asterixis, generalized seizures in 30%.

  • DDx: Malignant HTN, dialysis disequilibrium syndrome, stroke.

    P.215

    Table 57. Gram-negative susceptibilities (%). (MGH data 2005; courtesy of D. Hooper, MD.)

    Ampicillin Piper-tazo Cefazolin Ceftriaxone Cefepime Aztreonam Meropenem Gentamicin Amikacin Ciprofloxacin TMP-SMX Chloramphen Tetracycline Nitrofurant Acinetobacter 0 66 0 0 39 - 74 46 81 43 58 - 45 0 Aeromonas 0 90 0 93 100 100 100 100 100 97 97 - - - Citro. freundii 0 85 0 83 99 84 99 93 99 86 85 - 79 99 Citro. keseri 0 99 91 97 100 95 100 99 100 96 98 - 100 95 Ent. aerogenes 0 84 0 93 100 91 100 98 100 91 98 - 88 38 Ent. cloacae 0 72 0 75 97 74 100 91 99 83 84 - 73 51 E. coli 59 97 92 99 99 99 100 93 100 88 76 - 73 99 H. influenzae 72 - - 100 - - - - - - 77 97 - - Klebs. pneumo. 0 85 81 84 84 84 100 87 94 80 79 - 78 54 Klebs. oxytoca 0 90 67 93 93 92 100 93 98 92 94 - 89 93 Mo. morganii 0 97 0 97 100 91 100 92 100 91 87 - 57 11 Pr. mirabilis 81 96 97 100 100 99 100 95 100 84 87 - 0 0 Pr. vulgaris 0 97 0 84 100 92 100 100 100 100 97 - 36 5 Ps. aeruginosa - 91 - - 86 70 86 72 77 66 - - - - Salmonella 90 97 - 98 100 98 100 - - 100 98 - 91 - Se. marcescens 0 94 0 94 98 94 100 95 99 93 94 - 15 - Shigella 62 96 - 96 100 100 100 - - 96 46 - 24 -

    Table 58. Gram-positive susceptibilities (%). (MGH data 2005; courtesy D. Hooper, MD.)

    Penicillin Oxacillin Cephalothin c Vancomycin Clindamycin Erythromycin Tetracycline Chloramphen TMP-SMX Levofloxacin Rifampin Linezolid Nitrofurant. Gentamicin Staph. aureus 11 54 54 100 66 37 93 - 96 57 98 100 100 97 Coag-neg. Staph. 14 39 39 100 63 35 86 - 58 49 96 99 100 81 S. saprophyticus - - - 100 89 48 86 - 97 99 100 100 100 100 S. lugdunensis 70 100 - 100 91 87 94 - 100 100 100 100 100 100 Strep. pneumo. 68 - - 100 86 70 79 97 79 100 - - - - a-hemol. Strep. 62 - - 100 85 56 62 - - 93 - - - - Grp A b- Strep. 100-   100100   95 87 69 - - 100 - - - - Grp B b- Strep. 100-   100100   86 73 13 - - 100 - - - - Grp C, G b- Strep 100-   100100   94 76 44 - - 100 - - - - S. anginosus 99 - - 100 84 80 73 - - 100 - - - - Enterococci 78 - - 80 - 18 28 90 - 56 29 99 88 - E. faecalis 100-   - 91 - 18 27 85 - 63 41 100 100 - E. faecium 8 - - 13 - 2 31 97 - 4 11 94 48 -

  P.216

  • Rx: Treat renal failure; seizures. DPH and levetiracetam need renal dosing (see p. 163). Although phenobarbital is excreted by kidneys, levels are unaffected by renal failure unless GFR <10.

• Dialysis disequilibrium syndrome: Acutely during or after dialysis, with headache, muscle cramps, confusion, seizures, or coma. Probably caused by cerebral edema.

• Dialysis dementia syndrome: Subacute memory loss, personality change, apraxia, dysarthria, myoclonus, seizures. EEG shows bursts of slowing and spikes.

C. Hematuria workup

Stop anticoagulants, change bladder catheter, consider irrigation, renal ultrasound, cystoscopy, antineutrophil cytoplasmic Ab (ANCA), antiglomerular basement membrane antibody.

D. Causes of acute renal failure

• Prerenal: Hypovolemia or hypotension from dehydration, sepsis, bleed, or heart failure; liver failure.

• Renal:

  • Acute tubular necrosis (ATN): From ischemia, toxins, radiocontrast agents, hemo- or myoglobinuria.

  • Acute tubulointerstitial nephritis: From drug reaction, pyelonephritis, papillary necrosis.

  • Intrarenal precipitation: Calcium, urates, myeloma protein.

  • Other: Glomerulonephritis, DIC with cortical necrosis, arterial or venous obstruction.

• Postrenal: Obstruction from prostatism, tumor, or stones.

E. Tests

• Blood: BUN, creatinine, electrolytes, Ca, Mg, phos, CBC, CPK.

• Urine: UA, sediment, culture, urine eosinophils, urine electrolytes after 6 h off diuretics (or test urine urea nitrogen if on diuretics).

• FENa: Fractional excretion of sodium. Not helpful in nonoliguric acute tubular necrosis.

  • FENa = 100 (UNa SCr)/(SNa UCr); all in mg/dL.

  • Causes of low FENa: Dehydration, Na-avid renal failure, cirrhosis, nephrotic syndrome, CHF, glomerulonephritis, oliguric contrast-induced renal failure.

  • Causes of high FENa: Recent diuretics; renal failure.

  Table 59. Prerenal kidney failure vs. acute tubular necrosis (ATN).
  Prerenal ATN BUN Up Up Serum Cr ~nl Up BUN/S Cr >20 nl Urine Na <20 >40 U Cr/S Cr >40 <20 Urine osms >500 <350 FeNa <1 >2 IV fluid helps? Yes No

P.217

• 24-h urine for protein and creatinine in chronic renal failure.

  • Creatinine clearance = [urine Cr (mg/dL)][vol (mL)]/[serum Cr (mg/dL)][time (min)]

  • Estimated creatinine clearance: Inaccurate if Cr changing.

    • Male = (140 - age)(wt in kg)/(72 serum Cr)

    • Female = 0.85 male

• Other tests: Consider renal ultrasound, renal scan, glomerulonephritis workup.

F. Orders

Renal diet (<60 g protein, 2 g Na, K) unless on dialysis, when need protein supplements. Strict I/O, bladder catheter, daily wts.

• Stop nephrotoxins: Gentamicin, ACE-I, NSAIDs; renally dose cimetidine and Abx.

  • NSAIDs can lower Na, increase K, cause proteinuria, acute interstitial nephritis.

  • Gentamicin: Pts. on dialysis can have gentamicin; redose after each dialysis.

• IV fluids: If dehydrated.

• Diuretics: If oliguric. Furosemide IV; consider adding chlorothiazide or mannitol. Follow I/Os q1h. Hold diuretics if pt. has no response, or furosemide level will build up and cause ototoxicity.

• Chronic renal failure: Nephrocaps or equivalent vitamin supplementation 1 qd; aluminum hydroxide Amphogel 30 cc qid (avoid Mg compounds), calcium acetate (PhosLo) 1 2 tabs. Consider erythropoietin, iron, calcium, vit D, bicarb (600 1,200 mg PO bid).