hla hyper nat re mia handout

8/3/2019 Hla Hyper Nat Re Mia Handout

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Hypernatremia

Primary Care Conference

K. Mae Hla, M.D., M.H.S.April 21, 2004


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Objectives

Brief review of pathophysiology, causes,clinical manifestations of hypernatremia

Review management, emphasizing aquantitative approach to correction offluid imbalance

DisclosureNot sponsored by any pharmaceutical companies


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The Patient

51-year-old male with acutely decompensatedschizo-affective disorder was readmitted 1 day

after discharge to UW Psychiatry involuntarilyfor increasing agitation and psychosis

History of noncompliance with medications(Lithium 1200 mg, Clozaril 375 mg, Modafinil400 mg, Synthroid 75 mcg) all of which wererestarted


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Deterioration during

hospitalization

Patient was in and out of locked seclusion

due to violent behavior with subsequent poororal intake

CBC, Chem 7 and CK were done after 4 daysbecause staff felt that patients mental status

has worsened and dystonia might be present Serum sodium was noted to be high, and a

general medicine consult was requested


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Physical Exam

BP: 160/82, P: 92, T: 37; orthostatic to110/60 previous evening per nursing note

Tongue and oral mucosa: dry Skin: poor turgor and tenting

Cor: JVP-flat, normal heart sounds

Lungs: Clear. Abdomen, non-tender, BS + GU: incontinent of urine in diaper

Neuro: limited exam, incoherent, psychotic,agitated, in 4 point leather restraints


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Initial Lab Results

Sodium = 154

Potassium = 4.4

Chloride = 115 HCO3 = 26

BUN = 27

Creatinine = 1.4

Calcium = 10.1

Glucose = 100

Urine Na+ = 41 Urine Osmolality = 492

Plasma Osmolality = 315


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What is the cause of his

hypernatremia?


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Water homeostasis

Water homeostasis is mediated by:

Thirst

Arginine Vasopressin (ADH)

Kidneys

A disruption in the water balance leads

to abnormality in serum sodium


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Hypernatremia (Na+ > 145 mEq)

Hypernatremia is caused by a relativedeficit of water in relation to sodium

which can result from Net water loss: accounts for majority of

cases of hypernatremia pure water loss

hypotonic fluid loss Hypertonic gain results from iatrogenic

sodium loading


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Extracellular-Fluid & Intracellular-Fluid Compartments underNormal Conditions and during States of Hypernatremia


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Causes of Hypernatremia

Net water loss

Pure water loss

Unreplaced insensible losses (dermal and respiratory)

Hypodipsia

Neurogenic diabetes insipidus Post-traumatic

tumors, cysts, histiocytosis, tuberculosis, sarcoidosis

Idiopathic

aneurysms, meningitis, encephalitis, Guillain-Barre

syndrome


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Pure Water Loss (contd)

Congenital nephrogenic diabetes insipidus

Acquired nephrogenic diabetes insipidus

Renal disease (e.g. medullary cystic disease)Hypercalcemia or hypokalemia

Drugs (lithium, demeclocycline, foscarnet,methoxyflurane, amphotericin B, vasopressin V2-

receptor antagonists)


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Causes of Hypernatremia (contd)

Hypotonic fluid loss

Renal causes

Loop diuretics

Osmotic diuresis (glucose, urea, mannitol)

Postobstructive diuresis

Polyuric phase of acute tubular necrosis

Intrinsic renal disease


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Hypotonic Fluid Loss (contd)

Gastrointestinal causes

Vomiting

Nasogastric drainage

Enterocutaneous fistula

Diarrhea

Use of osmotic cathartic agents (e.g., lactulose)

Cutaneous causesBurns

Excessive sweating


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Causes of Hypernatremia (contd)

Hypertonic sodium gainHypertonic sodium bicarbonate infusion

Ingestion of sodium chloride

Ingestion of sea water

Sodium chloride-rich emeticsHypertonic saline enemas

Intrauterine injection of hypertonic saline

Hypertonic sodium chloride infusion

Hypertonic dialysisPrimary hyperaldosteronism

Cushings syndrome


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What is the hypernatremia

due to in our patient? Poor water/oral intake due to psychosis

(per hx)

Acquired partial nephrogenic DI due toLithium (suggested by low urine osmolalityrelative to high serum osmolality)

Increased insensible loss due to agitation,and hyperventilation

?? Renal loss of sodium-urine Na+ 41


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Clinical Manifestations

CNS dysfunction s/s depend on large or rapidincreases in serum Na+ concentration

Outpatients: Affects extremes of ages

Infants: hyperpnea, restlessness, m/s weakness,lethargy, coma

Elderly: few sx until Na+ > 160; confusion, coma

more related to coexisting condition Inpatients: all ages, sx more elusive in presence

of pre-existing neurologic dysfunction


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Management

A two-pronged approach:

Addressing the underlying cause: stopping

GI loss, controlling pyrexia, hyperglycemia,correcting hypercalcemia or feedingpreparation, moderating lithium inducedpolyuria

Correcting the prevailing hypertonicity: rateof correction depends on duration ofhypernatremia to avoid cerebral edema


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Effects of Hypernatremia on the Brain andAdaptive Responses


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Correction of Hypernatremia

Hypernatremia that developed over aperiod of hours (accidental loading)

Rapid correction improves prognosiswithout cerebral edema

Accumulated electrolytes in brain rapidly

extruded Reducing Na+ by 1 mmol/L/hr appropriate


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Goal of Treatment

Reduce serum sodium concentration to145 mmol/L

Make allowance for ongoing obligatoryor incidental losses of hypotonic fluidsthat will aggravate the hypernatremia

In patients with seizures promptanticonvulsant therapy and adequateventilation


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Administration of Fluids

Preferred route: oral or feeding tube

IV fluids if oral not feasible

Except in cases of frank circulatorycompromise, isotonic saline is unsuitable

Only hypotonic fluids are appropriate-pure

water, 5% dextrose, 0.2 % saline, 0.45%saline-the more hypotonic the infusate, thelower the infusion rate required


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Calculation of Free Water Deficit

Assuming pure water loss,

CBW x [Na+] = NBW x 140

NBW = (CBW x [Na+

]) / 140Water deficit = NBW CBW

= {CBW x [Na+] / 140} CBW

= CBW {[Na+] / 140} 1}

= 65 x 0.6 x (154/140 1)

= 39 x (14/140)

= 3.9 L


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Patients Serial Electrolytes

Before and After Treatment

4/22 4/26 4/27(a.m.)

4/27(p.m.)

Na+ 145 154 150 154

K 4.5 4.8 4.4 4.8

Cl 110 114 115 117

CO2 25 29 26 26

BUN 17 28 27 25

Creat 1.1 1.4 1.4 1.4

Glu 87 100 92


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Formula for ManagingHypernatremia

CLINICAL USE

Estimate the effect of 1 liter of any

infusate on serum Na+

Estimate the effect of 1 liter of anyinfusate containing Na+ and K+ onserum Na+

FORMULA*

1. Change in serum Na+

=

2. Change in serum Na+ =

infusate Na+ - serum Na+

total body water + 1

(infusate Na+ + infusate K+) -serum Na+

total body water + 1


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Characteristics of Infusate

Infusate Infusate Na+

Extracellular-FluidDistribution

mmol per liter %

5% Dextrose in H20 0 40

0.2% NaCl in 5% dextrose in H2O 34 55

0.45% NaCl in H2O 77 73

Ringers lactate 130 97

0.9% NaCl in H2O 154 100


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Rate of infusion of 0.2 saline

in 5% dextrose in waterChange in Na+ with 1 L of above solution

= (34-154) / {(65 x 0.6) + 1} = -120/40 = - 3 mEq/L

Desired change in Na+ = 145 154 = - 9 mEq/Lover 24 hours

Thus needs 9/3 = 3 L (over 24 hours)

Calculated rate of infusion = 3000/24 = 125 ml/hr


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Change in Serum Na+ afteradjusting the infusate and rate

4/22 4/26 4/27(a.m.)

4/27(p.m.)

4/28(a.m.)

4/28(p.m.)

Na+ 145 154 150 154 151 148

K 4.5 4.8 4.4 4.8 4.2 3.7

Cl 110 114 115 117 115 114

CO2 25 29 26 26 26 26

BUN 17 28 27 25 23 20

Creat 1.1 1.4 1.4 1.4 1.3 1.3

Glu 87 100 92 115 115


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Summary of Managing

Hypernatremia Isotonic saline unsuitable except in ECF volume

depletion causing hemodynamic instability

Switch to hypotonic solutions as soon as

circulatory status stabilized Avoid excessive rapid correction or over

correction

Select the most hypotonic infusate suitable with

appropriate allowances for ongoing fluid losses Most important - reassess infusion prescriptions

at regular intervals based on pts clinical statusand electrolyte values

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