Fluid and Electrolyte Fluid and Electrolyte PhysiologyPhysiology

Dr. Raymon GroganDr. Raymon Grogan

11/6/0611/6/06

Total Body Fluid by CompartmentTotal Body Fluid by CompartmentTotal Body Water

Electrolyte Composition of Body Electrolyte Composition of Body Fluid CompartmentsFluid Compartments

Composition of Parenteral Fluids Composition of Parenteral Fluids (mEq/L)(mEq/L)

FluidFluid Na+Na+ K+K+ Ca2+Ca2+ Cl-Cl- HCO3-HCO3- pHpHECFECF 142142 44 55 103103 2727 7.47.4

LRLR 130130 44 2.72.7 109109 2828 6.56.5

.9% NaCl.9% NaCl 154154 154154 4.54.5

.45% NaCl.45% NaCl 7777 7777 4.54.5

.2% NaCl.2% NaCl 3030 3030 4.54.5

3% NaCl3% NaCl 513513 513513 4.54.5

5% NaCl5% NaCl 855855 855855 4.54.5

5% Albumin5% Albumin 145145 7.47.4

Composition of GI Fluids (mEq/L)Composition of GI Fluids (mEq/L)

SourceSource Daily LossDaily Loss Na+Na+ K+K+ Cl-Cl- HCO3-HCO3-

SalivaSaliva 10001000 30-8030-80 2020 7070 3030

GastricGastric 1000-20001000-2000 60-8060-80 1515 100100 00

PancPanc 10001000 140140 5-105-10 60-9060-90 40-10040-100

BileBile 10001000 140140 5-105-10 100100 4040

SBSB 2000-50002000-5000 140140 2020 100100 25-5025-50

LBLB 200-1500200-1500 7575 3030 3030 00

SweatSweat 200-1000200-1000 20-7020-70 5-105-10 40-6040-60 00

HyponatremiaHyponatremia

Defined as serum [Na+] less than 136 Defined as serum [Na+] less than 136 mEq/LmEq/L

Water shifts into cells causing cerebral Water shifts into cells causing cerebral edemaedema

125 mEq/L – nausea and malaise125 mEq/L – nausea and malaise 120 mEq/L – headache, lethargy, 120 mEq/L – headache, lethargy,

obtundationobtundation 115 mEq/L – seizure and coma115 mEq/L – seizure and coma

HyponatremiaHyponatremia

1. Assess plasma osmolality1. Assess plasma osmolality 2. Assess volume status of patient2. Assess volume status of patient

Hypervolemic, Euvolemic, HypovolemicHypervolemic, Euvolemic, Hypovolemic 3. Assess Urine Sodium Concentration3. Assess Urine Sodium Concentration

Needed for definitive diagnosis, not needed for Needed for definitive diagnosis, not needed for treatment purposestreatment purposes

4. Calculate Na+ Deficit4. Calculate Na+ Deficit 0.6 x weight (kg) x (130 – plasma [Na+])0.6 x weight (kg) x (130 – plasma [Na+])

5. Correct at no more than 0.5mEq/L per hour 5. Correct at no more than 0.5mEq/L per hour or 12 mEq/L per 24 hoursor 12 mEq/L per 24 hours

Isosmotic and Hyperosmotic Isosmotic and Hyperosmotic HyponatremiaHyponatremia

Iso and Hyperosmotic hyponatremia are due to Iso and Hyperosmotic hyponatremia are due to excessive solutes in plasma. excessive solutes in plasma.

IsosmoticIsosmotic• Pseudohyponatremia – No treatment necessaryPseudohyponatremia – No treatment necessary

HyperlipidemiaHyperlipidemia HyperproteinemiaHyperproteinemia

• Isotonic InfusionsIsotonic Infusions GlycineGlycine MannitolMannitol

Hyperosmotic – Treat underlying causeHyperosmotic – Treat underlying cause• HyperglycemiaHyperglycemia

Each 100 mg/dl of glucose reduces [Na+] by 1.6 mEq/lEach 100 mg/dl of glucose reduces [Na+] by 1.6 mEq/l

• Hypertonic InfusionsHypertonic Infusions GlycerolGlycerol MannitolMannitol GlycineGlycine

Hyposmotic HyponatremiaHyposmotic Hyponatremia

1. Assess volume status1. Assess volume status Hypervolemic – cirrhosis, heart failure, Hypervolemic – cirrhosis, heart failure,

nephrotic syndromenephrotic syndrome Euvolemic – polydipsia, SIADHEuvolemic – polydipsia, SIADH Hypovolemic – most common causeHypovolemic – most common cause

• Excessive renal (diuretic) or GI (emesis, diarrhea) Excessive renal (diuretic) or GI (emesis, diarrhea) losseslosses

Treatment of HyponatremiaTreatment of Hyponatremia

Iso or HyperosmoticIso or Hyperosmotic Correct underlying disorderCorrect underlying disorder

HyposmoticHyposmotic Iso or hypervolemic – fluid restrictionIso or hypervolemic – fluid restriction HypovolemicHypovolemic

• Asymptomatic – fluid resuscitate with isotonic Asymptomatic – fluid resuscitate with isotonic salinesaline

• Symptomatic or plasma [Na+] less than 110 mEq/LSymptomatic or plasma [Na+] less than 110 mEq/L Calculate Na+ deficitCalculate Na+ deficit Correct at a rate no greater than 0.5 mEq/L/hour or 12 Correct at a rate no greater than 0.5 mEq/L/hour or 12

mEq/L/daymEq/L/day

Correction of Sodium DeficitCorrection of Sodium Deficit

Example: A 60 kg woman with a plasma sodium Example: A 60 kg woman with a plasma sodium concentration of 120mEq/L:concentration of 120mEq/L:

Sodium deficit = TBW x (130 – [Na+]p)Sodium deficit = TBW x (130 – [Na+]p)

Sodium deficit = 0.5 x 60 x (130-120) = 300mEqSodium deficit = 0.5 x 60 x (130-120) = 300mEq

3% NaCl contains 513 mEq sodium/L3% NaCl contains 513 mEq sodium/L

Volume of 3% NaCl needed = 300/513 = 585 mLVolume of 3% NaCl needed = 300/513 = 585 mL

At 0.5 mEq/L/hr a correction of 10 mEq should be done At 0.5 mEq/L/hr a correction of 10 mEq should be done over 20 hoursover 20 hours

So, 585 mL/20 hours = 29 mL/hour of 3% NaClSo, 585 mL/20 hours = 29 mL/hour of 3% NaCl

HypernatremiaHypernatremia

Defined as serum [Na+] greater than 146 Defined as serum [Na+] greater than 146 mEq/LmEq/L

Lethargy, weakness, and irritability that Lethargy, weakness, and irritability that progress to seizure, coma, and deathprogress to seizure, coma, and death

Usually occurs in adults with altered Usually occurs in adults with altered mental status or no access to watermental status or no access to water

HypernatremiaHypernatremia

1. Assess volume status1. Assess volume status 2. Measure urine [Na+]2. Measure urine [Na+] 3. Calculate water deficit3. Calculate water deficit

0.6 x weight (kg) x ([Na+]/140 -1)0.6 x weight (kg) x ([Na+]/140 -1) 4. Correct with free water no faster than 4. Correct with free water no faster than

0.5 mEq/L/hour or 12 mEq/L/day0.5 mEq/L/hour or 12 mEq/L/day

HypernatremiaHypernatremia

Hypovolemic – loss of hypotonic fluidsHypovolemic – loss of hypotonic fluids Diuresis, vomiting, diarrheaDiuresis, vomiting, diarrhea

Isovolemic – loss of free waterIsovolemic – loss of free water Diabetes insipidus, hypodipsiaDiabetes insipidus, hypodipsia

Hypervolemic – gain of hypertonic fluidsHypervolemic – gain of hypertonic fluids Hypertonic saline administrationHypertonic saline administration

Treatment of HypernatremiaTreatment of Hypernatremia

Hypovolemic Hypovolemic Replace the free water deficitReplace the free water deficit

HypervolemicHypervolemic Diuretics (lasix) to excrete sodium in urine Diuretics (lasix) to excrete sodium in urine

combined with hypotonic saline for partial combined with hypotonic saline for partial volume replacementvolume replacement

Treatment of HypernatremiaTreatment of Hypernatremia

IsovolemicIsovolemic Diabetes InsipidusDiabetes Insipidus Loss of hypotonic urine secondary to lack of ADH Loss of hypotonic urine secondary to lack of ADH

production (central) or lack of response to ADH by production (central) or lack of response to ADH by kidney (nephrogenic)kidney (nephrogenic)

Hallmark is hypotonic urine (200-500 mOsm/L) with Hallmark is hypotonic urine (200-500 mOsm/L) with hypertonic plasmahypertonic plasma

Treat by correcting free water deficitTreat by correcting free water deficit In central DI must also administer 5 – 10 units of In central DI must also administer 5 – 10 units of

DDAVP Q6H to prevent ongoing free water lossDDAVP Q6H to prevent ongoing free water loss

HyperkalemiaHyperkalemia

Defined as a serum [K+] greater than 4.6 mEq/LDefined as a serum [K+] greater than 4.6 mEq/L Changes in cellular transmembrane potentials can lead Changes in cellular transmembrane potentials can lead

to lethal cardiac arrhythmiasto lethal cardiac arrhythmias Most often associated with renal impairment coupled Most often associated with renal impairment coupled

with exogenous K+ administration or drugs that increase with exogenous K+ administration or drugs that increase K+K+

Transcellular shifts – acidosis, succinylcholine, insulin Transcellular shifts – acidosis, succinylcholine, insulin deficiency, massive tissue destructiondeficiency, massive tissue destruction

Massive blood transfusionsMassive blood transfusions Pseudohyperkalemia - Thrombocytosis, hemolysis, Pseudohyperkalemia - Thrombocytosis, hemolysis,

leukocytosisleukocytosis Urine K+ excretion rate can be used to determine exact Urine K+ excretion rate can be used to determine exact

cause of hyperkalemiacause of hyperkalemia

HyperkalemiaHyperkalemia

Drugs causing hyperkalemia – K+ sparing Drugs causing hyperkalemia – K+ sparing diruetics, ACEI, NSAIDs, Heparin, diruetics, ACEI, NSAIDs, Heparin, Cyclosporin, Tacrolimus, BactrimCyclosporin, Tacrolimus, Bactrim

EKG ChangesEKG Changes 5.5 – 6.5 mEq/L – peaked T-waves5.5 – 6.5 mEq/L – peaked T-waves 6.5 – 7.5 mEq/L – loss of P-waves6.5 – 7.5 mEq/L – loss of P-waves > 8.0 mEq/L – widened QRS> 8.0 mEq/L – widened QRS

Treatment of HyperkalemiaTreatment of Hyperkalemia

1. If EKG changes administer 10 mL of 1. If EKG changes administer 10 mL of 10% Calcium Gluconate10% Calcium Gluconate

2. 1 amp D50 with 10 units IV insulin 2. 1 amp D50 with 10 units IV insulin (onset 10-20 minutes, duration 2-3 hours)(onset 10-20 minutes, duration 2-3 hours)

3. Albuterol 10 -20 mg (onset 4-5 hours, 3. Albuterol 10 -20 mg (onset 4-5 hours, duration 2-3 hours)duration 2-3 hours)

4. Kayexalate 15-30 g (oral onset 4-5 4. Kayexalate 15-30 g (oral onset 4-5 hours, enema onset 1 hour)hours, enema onset 1 hour)

DialysisDialysis

HypokalemiaHypokalemia

Defined as serum [K+] less than 3.6 Defined as serum [K+] less than 3.6 mEq/LmEq/L

Occurs in up to 20% of hospitalized Occurs in up to 20% of hospitalized patientspatients

2.5 mEq/L – muscular weakness, myalgia2.5 mEq/L – muscular weakness, myalgia <2.5 mEq/L – cramps, parasthesias, ileus, <2.5 mEq/L – cramps, parasthesias, ileus,

tetany, rhabdomyolisis, PVCs, A-V block, tetany, rhabdomyolisis, PVCs, A-V block, V-tach, V-fibV-tach, V-fib

HypokalemiaHypokalemia

Inadequate intakeInadequate intake Increased excretion – diarrhea, diuretics, Increased excretion – diarrhea, diuretics,

alkalosis, glucocorticoids, RTAalkalosis, glucocorticoids, RTA Transcellular shifts – beta-agonists, Transcellular shifts – beta-agonists,

theophylline, insulin, hyperthyroidism, theophylline, insulin, hyperthyroidism, bariumbarium

Replace no faster than 20 mEq/H Replace no faster than 20 mEq/H peripherally and 100 mEq/H centrallyperipherally and 100 mEq/H centrally