IX: ENDOCRINE & METABOLIC



•  Step 4a: Is there an anion gap?


Anion gap acidosis: (Na – (Cl + bicarb)) > 14 (see chart)


Note: Needs to be corrected for albumin; a fall in serum albumin 1 g/dL from the nl value (4.2 g/dL) decreases the anion gap by 2.5 meq/L. Corrected AG = AG + (2.5 × [4.2 – albumin]).


•  Step 4b: If an anion gap is present, is there an osmolar gap?


Osmolar gap: Measured serum Osm – Calculated Osm >10 mOsm/L, where


Calculated Osm = (2 × [Naμ+μ]) + glucose/18 + BUN/2.8 + Ethanol/4.6


•  Step 4c: If no anion gap is present, what is UAG?


Urinary anion gap: Na + K – Cl


Note: The UAG can help differentiate GI & renal causes of non-AG (or hyperchloremic) metabolic acidosis, as base can be lost from the gut or kidney (negative UAG: GI loss [ie, diarrhea, small bowel fistula, ileostomy]; positive UAG: Renal loss, particularly RTA types I & IV)


•  Step 5: What is the delta ratio, also known as the “delta/delta”?


(AG – nl AG)/(nl HCO3 – HCO3), or simply (AG – 12)/(24 – HCO3)


•  If delta/delta > +6, suggests concomitant metabolic alkalosis, or prior compensated respiratory acidosis


•  If delta/delta = 0, suggests uncomplicated AG metabolic acidosis


•  If delta/delta > –6, suggests concomitant hyperchloremic non-AG metabolic acidosis














Treatment and Disposition


•  Both will largely depend on severity & underlying etiology of the disorder


•  Limited role for bicarbonate in the absence of hemodynamic collapse


ABNORMAL ELECTROLYTES


Hyponatremia


Definition


•  Na <135, excess of water relative to sodium, generally from elevated ADH; generally not symptomatic at Na >125


History


•  Most sxs are nonspecific & can include fatigue, weakness, muscle cramps, thirst, or postural dizziness. Sxs can range to more severe manifestations including confusion, agitation, delirium, lethargy, somnolence, coma, or szs.


•  Other helpful historical features include h/o CHF, cirrhosis, renal dz, cancer, adrenal or pituitary dysfxn, recent GI surgery, thiazide or loop diuretics use, alcoholism


Physical Exam


•  Look for signs to assess pt fluid status:


•  Hypervolemia: Elevated JVP, peripheral edema, crackles, ascites, anasarca


•  Hypovolemia: Tachycardia, hypotension, dry mucous membranes, oliguria, poor skin turgor, IVC collapsibility


•  Look for signs of profound hyponatremia: Lethargic, disoriented/abnl sensorium, depressed reflexes, hypothermic, pseudobulbar palsy, Cheyne–Stokes respiration


Diagnostics


•  Labs: Chem 7, FSG, urine electrolytes (Na, Cr, Osm), serum Osm, albumin


•  VBG w/ stat sodium & Osm may provide more rapid turnaround


•  Corrected Naglucose = Serum Na + [0.016 × (serum glucose – 100)] up to 400 mg/dL


•  for glucose >400 mg/dL, 4 mEq/L should be added to every additional 100 mg/dL


Step-wise Approach to Hyponatremia


•  Step 1: What is the serum osmolality?




•  Step 2: What is the pt’s volume status? Hypervolemic, euvolemic, or hypovolemic?


•  Step 3: What are the urine Na, urine Osm, & FeNA values?


•  Fractional Excretion of Sodium = FeNa = (Naurine × Crserum)/(Naserum × Crurine)




Treatment


•  Asymptomatic or mild sxs of hyponatremia: Correct serum Na at ≤0.5 mEq/L/h


•  Severe manifestations of hyponatremia: RAPID correction serum Na at 2 mEq/L/h × 2–3 h OR until sxs resolve




•  Euvolemic hyponatremia


•  Asymptomatic: Free water restrict (500–1000 mL/d)


•  Symptomatic: See above


•  SIADH


•  Free water restrict + treat underlying cause


•  Caution if using hypertonic or nl saline esp if IVF Osm < urine Osm, serum sodium may worsen (higher Osm will draw out fluid)


•  May also consider lithium or demeclocycline (NEJM 2007;356:2064)


•  Hypovolemic hyponatremia


•  Volume replete w/ nl saline, as above (once dehydration resolved, stimulation of ADH will decline & Na will correct)


•  Hypervolemic hyponatremia


•  Free water restrict (0.5–1.5 L/d)


•  Increase arterial volume: W/ vasodilators (Nitro), loop diuretics; consider albumin in cirrhosis


•  Severe hyponatremia: Consider diuresis + Na replacement


Disposition


•  Home: Mild asymptomatic hyponatremia


•  Admit: Symptomatic, comorbidities, elderly. May require ICU admission if severe.


Pearl


•  Rapid correction >10–12 mEq/L/d may result in central pontine myelinolysis (dysarthria, szs, quadriparesis due to focal myelin destruction in pons & extrapontine areas)


Hypernatremia


Definition


•  Na >145, usually from free water loss or sodium gain (ie, infusion of hypertonic fluid)


•  Appropriate response to hypernatremia is increased free water intake stimulated by thirst & renal excretion of a minimal volume of maximally concentrated urine as regulated by ADH


History


•  Mild sxs include increased thirst or polyuria


•  Severe sxs: AMS (irritability, lethargy, confusion, delirium, coma)


•  RFs: Elderly, infants, debilitated. Endocrine pathology; cardiac, renal, liver dzs; psychiatric disorder (see etiology of Central and Nephrogenic Diabetes Insipidus); MEDS (see below chart), living situation (access to free water).


Physical Exam


•  Look for signs to assess pt fluid status:


•  Hypervolemia: Elevated JVP, peripheral edema, crackles, ascites, anasarca


•  Hypovolemia: Tachycardia, hypotension, dry mucous membranes, oliguria, poor skin turgor, IVC collapsibility


•  Severe hypernatremia: Lethargy, muscle spasticity, tremor, hyperreflexia, respiratory paralysis, ataxia


Diagnostics


•  Labs: Chem 7, FSG, urine electrolytes (Na, Cr, Osm), serum Osm, albumin


•  VBG w/ stat sodium & Osm may provide more rapid turnaround


•  Corrected Naglucose = Serum Na + [0.016 × (serum glucose – 100)] up to 400 mg/dL


•  for glucose >400 mg/dL, 4 mEq/L should be added to every additional 100 mg/dL


Step-wise Approach to Hypernatremia


•  Step 1: What is the serum osmolality?


•  nl serum osmolality = 275–290 mosmol/kg


•  Step 2: What is the pt’s volume status? Hypervolemic, euvolemic, or hypovolemic?


•  Step 3: What are the urine Na & urine Osm values?




Treatment




•  Hypervolemic hypernatremia


•  Treat underlying disorder


•  Replace free water deficit (as above)


•  Euvolemic hypernatremia


•  Replace free water deficit (as above)


•  Treat underlying etiology


•  Central DI: Vasopressin 10 U SQ


•  Hypovolemic hypernatremia


•  Restore volume 1st then replace free water deficit (as above); add 40 mEq KCl IV to fluid replacement once pt is urinating


Disposition


•  Home: Mild hypernatremia which can be corrected in <24 h


•  Admit: Most will be admitted


Hypokalemia


Definition


•  Kμ+μ <3.5 mEq/L (ie, decreased intake, shift into cells, loss); 98% of potassium is intracellular.




History


•  Usually not symptomatic until Kμ+μ <3 mEq/L


•  Nausea, vomiting, weakness, fatigue, myalgia, muscle cramps. Meds (see Differential table).


•  Pts at highest risk for electrocardiac cx of hypokalemia include those w/ acute ischemia, prolonged QT syndrome, & those taking digoxin


Physical Exam


•  Paresthesias, depressed reflexes, proximal muscle weakness, ileus


•  Severe hypokalemia: Hypoventilation, paralysis, rhabdomyolysis, myoglobinuria


•  ARF, polymorphic VT, asystole


Diagnostics


•  Labs: Chem 7, UA, urine electrolytes, urine Osm; consider blood gas, CPK, serum Osm


•  Urine Kμ+μ <15 mmol/d suggests extrarenal, while urine Kμ+μ >15 mmol/d suggests renal etiology


•  Transtubular Kμ+μ concentration gradient (TTKG) is helpful, but rarely used in the ED: TTKG = (PlasmaOsm × UrineK)/(PlasmaK × UrineOsm)


Note: Hypokalemia w/ TTKG >4 suggests renal Kμ+μ loss due to distal Kμ+μ secretion


•  ECG: T-wave flattening/inversion, ST depression, U-waves, prolonged QT/QU interval; may also see PR prolongation, decreased voltage, QRS widening, atrial/ventricular dysrhythmias


Treatment


•  ED


•  Potassium replacement: Potassium chloride, Potassium bicarbonate, Potassium phosphate




•  Treat underlying cause


•  Replace Mg as needed (*Note: Concurrent Mg & Kμ+μ deficiency could lead to refractory Kμ+μ repletion)


•  Goal Kμ+μ = 4 mEq/L in pts at highest risk


•  Home


•  Counsel pts to increase dietary intake of Kμ+μ (dried fruits, nuts, avocados, wheat germ lima beans, vegetables [spinach, broccoli, cauliflower, beets, carrots], fruits [banana, kiwi, etc])


•  Discuss w/ PCP: Decrease diuretic dose; start/substitute for Kμ+μ-sparing med (βB, ACE, ARB, Kμ+μ-sparing diuretic)


•  Potassium replacement: KCl 20 mEq PO QD for prevention; KCl 40–100 mEq PO QD for tx


Disposition


•  Home: Mild hypokalemia w/ close f/u to recheck labs


•  Admit: Moderate/severe hypokalemia, acid–base abnormalities, arrhythmia


Pearl


•  Avoid dextrose solutions (stimulate insulin & inward shift of Kμ+μ)


Guideline: Cohn JN, Kowey PR, Whelton PK, Prisant LM. New guidelines for potassium replacement in clinical practice. Arch Intern Med. 2000;160: 2429–2436.


Hyperkalemia


Definition


•  Kμ+μ >5 mEq/L (ie, Kμ+μ release from cells, decreased renal losses, iatrogenic)



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Sep 6, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on IX: ENDOCRINE & METABOLIC

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