5 Hyponatremia: ICU Pseudohyponatremia Post-operative Hyponatremia SIADH Hyperglycemia, HyperlipidemiaPost-operative HyponatremiaSIADHCerebral Salt WastingMechanical VentilationCirrhosisCongestive Heart FailureSIRS/MODSLoop diuretics with hypotonic fluid replacementCertain drug intoxicationsAgents that enhance ADH release or action
6 Major Causes of Hyponatremia EIVF DepletionTrue Volume DepletionCHF or CirrhosisSIADHHormone mediatedAdrenal InsufficiencyHypothyroidismPregnancyDisorders in which ADH levels may be appropriately suppressedAdvanced renal failurePrimary polydipsiaBeer drinker’s potomaniaPseudohyponatremiaHigh plasma osmolality: hyperglycemia, mannitol, ureaNormal plasma osmolality: hyperlipidemia, hyperproteinemia, glycine infusion.
7 Steps in the Evaluation of Hyponatremia Calculate plasma osmolalityMeasure plasma osmolalityWhen low; defines true hypo-osmolal state or clinical hyponatremiaConsider plasma glucose, protein and lipidsEvaluate volume status of patientVolume depletionVolume expansionEuvolemiaMeasure urine sodium
8 Estimating the Serum Osmolality In Spurious Hyponatremia:Calculated OSMp < Determined OSMp Spurious Hyponatremia (hyperlipemia, hyperproteinemia) is not a hypoosmolar state.
9 Causes of Hypoosmolality Volume DepletionGI, lung or skin lossesThird space sequestrationAdrenal insufficiencyRenal salt wastingCerebral salt wastingVolume ExpansionCHF, cirrhosis with ascites, nephrotic syndromeEuvolemicSIADH, water intoxication, reset osmostat, drugs
11 Syndrome of Inappropriate ADH Release (Bartter’s Criteria) Hyponatremia and true hypoosmolality by definitionEuvolemia clinicalUrine less than maximally dilute (urinary osmolality usually > 200 mOsm/kg of H2O)Normal renal, cardiac, hepatic, adrenal, pituitary, and thyroid functionNo history of antidiuretic drugsNo emotional or physical stressUrinary sodium > 20 mEq/literaa Urinary sodium may be <20 mEq/liter if the patient is volume deleted or on low sodium intake.
12 Disorders Associated With SIADH CarcinomasPulmonary disordersCentral nervous system disorders
13 Most Common Causes of SIADH in Elderly (CDP and NHR)* MedicationsIdiopathic formMalignancies*Aging Clin Exp Res 2003, 15:6-11.
14 Disorders Associated With SIADH: Carcinomas Small cell carcinoma of the lungCarcinoma of the duodenumCarcinoma of the pancreasThymomaLymphomaEwing’s sarcomaMesotheliomaCarcinoma of the bladderProstatic carcinomaOlfactory neuroblastoma
16 Disorders Associated With SIADH: Central Nervous Disorders Encephalitis (viral or bacterialMeningitis (viral, bacterial, tuberculosis, fungal)Head traumaBrain abscessBrain tumorsGuillain-Barré syndromeAcute intermittent porphyriaSubarachnoid hemorrhage or subdural hematomaCerebellar and cerebral atrophyCavernous sinus thrombosisNeonatal hypoxiaHydrocephalusShy-Drager syndromeRocky Mountain spotted feverDelirium tremensCerebrovascular accident (cerebral thrombosis or hemorrhage)Acute psychosisPeripheral neuropathyMultiple sclerosis
17 Guiding Principles in the Treatment of Hyponatremia 1. Neurologic disease can follow both the failure to promptly treat as well as injudiciously rapid treatment of hyponatremia.2. Presence or absence of significant neurologic signs and symptoms must guide treatment.3. Acuity or chronicity of the electrolyte disturbance impacts the rate at which the correction should be undertaken.
18 A Prudent Approach to the Treatment of Hyponatremia - 1 Acute Symptomatic Hyponatremia (duration < 48 hours)Risk for complication of cerebral edema greater than risk of treatment of complication.Treat with hypertonic NaCl: 3% 1-2 mL/kg/hr or 2 mEq/L/hr. until convulsions subside. Usually means increasing [Na+] by 10%.Alternative: furosemide and hypertonic NaClFull correction is dangerous. Correct by 10% or to mEq/L slowly.Then initiate water restriction.
19 A Prudent Approach to the Treatment of Hyponatremia - 2 Symptomatic Hyponatremia (Chronic or Unknown Duration)1. Increase serum sodium by 10%, that is, approximately 10 mEq/L and then water restrict. Usually 1 -2 mL/kg/hr of hypertonic saline.2. Do not exceed a correction rate of 1.5 mEq/L/hr at any given time.3. Do not increase serum sodium by more than15 mEq/day.4. Long-termH2O restrictionDemeclocycline mg bidV2 receptor antagonist? Aquaretics
20 Therapeutic Strategy Based On Volume Status of PatientPresence of Absence of SymptomsDuration of HypoosmolalityPresence of absence of risk factors for development of neurological complicationOsmotic demyelination is rare in patients with initial Na+ > 120mEq/L
21 A Prudent Approach to the Treatment of Hyponatremia - 3 Asymptomatic Hyponatremia1. Almost always chronic.2. Treat with water restriction regardless of how low the serum sodium.
22 Calculating Sodium Requirement in Hyponatremia In correcting hyponatremia the approximate expansion of total body water must be determined first by calculating the volume of water which was required to dilute the serum sodium concentration to its observed value. For example, in a 70 kg patient with a serum Na+ concentration of 120 mEq/L rather than 140 mEq/L, this calculation is made as follows:Body water in normal state = (70 kg) (0.60) = 42 LBody water in abnormal state = (x) (120) = (42)(140) = 49LExcess body water = 7 LThe amount of Na+ in milliequivalents required for correction can then be calculated; again it is necessary to assume Na+ is distributed throughout the total body water.(140-patient’s - Na+) (calculated total body water) = total Na+ requirement.
23 How to predict the effect of therapy on the patient’s serum sodium The Bottle:0.9% = 154 mEq/LRinger’s = 130 mEq/L0.45% = 77 mEq/L3% = 513 mEq/L
26 Steps in Evaluation of Hypernatremia Establish history of water intake, and integrity of thirst mechanismSevere hypernatremia is unusual unless thirst mechanism is defective or water is not available to the patient.Determine patient’s volume statusMeasure urine sodium concentration
27 Causes of Hypernatremia Volume DepletionUrine Na+ < 20: sweating, diarrhea, burnsUrine Na+ > 20: Renal losses: Hyperglycemia, mannitol, urea (osmotic diuresis), or intrinsic renal diseaseVolume ExpansionUrine Na+ > 20: Salt loading, Cushing’s syndrome, NaHCO3, hypertonic dialysisEulovemicUrine Na+ < 20: Fever, heat exhaustion, hypermetabolic stateUrine Na+ variable or > 20: Central DI, Nephrogenic DI
29 Patient Groups at Increased Risk for Hypernatremia Post craniotomy (sellar tumors)Elderly, nursing home residentsHypertonic infusionsTube feedingsOsmotic diureticsLactuloseMechanical ventilationDiabetes mellitus with poor glycemic controlPolyuric disorders
30 Diabetes Insipidus Central DI Failure to synthesize or secrete ADH Unable to concentrate urine with water deprivation (caution !)3% decrease in BW or increase in Posm to 295 normally results in increase in Uosm > 700Submaximal response: give ADHCentral DI Uosm will increase by 100% or more
31 Therapeutic Regimens for the Treatment of Diabetes Insipidus
32 Nephrogenic Diabetes Insipidus Does not respond to AVPCauses:Congenital NDI - AVPR2 or AQP2 mutationHypokalemiaHypercalcemiaDrugs: Lithium, demeclocycline, glyburide, colchicine, amphotericin BTreatment:ThiazidesReduce solute intake (low Na+ diet)NSAIDS
33 Treatment of Symptomatic Hypernatremia 1. Drop Na+S by 2 mEq/L/hr.2. Replace 50% of water deficit over hrs.3. Replace rest over next 24 hrs.4. Perform serial neurological exams.5. Decrease rate of correction when patient improved.6. Measure Na+ in serum and urine q 12 hrs.