10 Common Differential Dx Decreased Water ExcretionGFRKidney perfusionSIADHAddison’s DiseaseMalnutrition*Pseudohyponatremia±Psychogenic (>1 L / hour)Prompt them for answers*100mg/dL glucose increase 1.6 mEq/L [Na] decrease± Urine specific gravity < 1.003
11 COMMON CAUSES of HYPONATREMIA History: predisposing featuresExam: volume status (including orthostatics supine/standing)BMP; Urinalysis; Serum Osmolality; (Urine Sodium; Urine Osmolality)Head C.T. (if symptomatic)Other imaging/labs to evaluate CV, Renal, Endocrine systems as needed
22 Guidelines for Hypernatremia Rx Determine and treat likely cause(s)Most common error is “underguesstimation” of water deficit:TBW x ([Na+(measured)] – [Na+(desired) ])/[Na+ (desired)]Replace H20 enterally if possibleFrequent monitoring
24 Hypernatremia: Key Points [Na+] >145 mEq/LNet water lossCalculate the water deficit[Na+] >145 mEq/LUsually inadequate water intake in an obtunded/ill personIncreased [Na+] in ECF Water shift from ICF Cerebral shrinkage lethargy, coma, ICH from tearing of bridging veins
25 Case 3 29 y/o man with severe muscle weakness. No vomiting or diarrhea.Normal physical exam.
28 Common Causes of Hypokalemia Malnutrition/NPODiarrhea (100 mEq/L)Vomiting (volume depletion)DRUGSThiazides (stimulate excretion)Amphotericin BPenicillinsGentamicinFoscarnet
29 “Choose the most likely diagnosis” Bartter’s syndromeLaxative abusePrimary aldosteronismDiuretic abuseDistal renal tubular acidosis
30 Less Common Causes Hormonal Renal tubular disease Primary hyperaldosteronismAdenomas, hyperplasia, ectopic ACTH, ectopic mineralocorticoid (licorice, chaw)Secondary hyperaldosteronismRenal hypoperfusion (CHF, RAS, severe HTN)Renin-secreting tumorRenal tubular diseaseType 1 or 2 RTABartter’s syndrome (metabolic alkalosis, polyuria)Chronic magnesium depletionLaxative abuse (metabolic alkalosis)
31 Hypokalemia Rx Recognize likely total body depletion 1 mEq/L decrease = mEq total deficiencyGradual oral replacementI.V. replacement if serum level less than 3 mEq/LCheck & Replace magnesiumConsider telemetry
32 Hypokalemia: Key Points [K+] < 3.5: review medications, review health status[K+] < 3: interventionRecognize Mg+ is cofactorRenal/CV monitoring
33 Case 459 y/o man with 3-days malaise, decreased mental acuity and responsiveness, slurred speech.ESRD on hemodialysis; HTN, DM, Hypothyroidism
34 Disoriented and lethargic BP (supine) 148/79mmHg, HR 101/min (supine) RR 26/min, T 37.7oC.Mucous membranes are moist, neck veins are distended. Bilateral crackles and wheezes. Loud S peripheral edema.
37 Begin I.V. infusion of normal saline for volume repletion What is the next most appropriate step in managing this patient?Begin I.V. infusion of normal saline for volume repletionAdminister 1 ampule dextrose and 10 units insulin I.V. for hyperkalemiaTransfer to the ICU and perform emergent peritoneal dialysisTransfer to the ICU and perform emergent hemodialysis
43 Hyperkalemia: Key Points K>4.5: caution with medications, & monitorK>5.5: interveneCalcium (not kayexalate) is 1st lineCheck ECG
44 SUMMARY Construct your differential Know the complications of therapy Know the implications of lack of therapyCalculate water/electrolyte needs… But repeated and frequent monitoring is most important.Electrolyte disorders may be a diagnostic clue or an expected consequence of therapy