WATER REPLACEMENT IN HYPERNATREMIA

MADE RIDICULOUSLY SIMPLE SRIJANTANDUKAR

RENALFELLOW

10/26/2018

Doc,I’vebeenhavingthisnaggingcoughandshortnessofbreathfora

fewdaysnow… Hmm..Whatothermedicalproblemsdo

youhave?

Well,I’vehadbipolardisorderforyears,butit’sbeenstablewith

lithiumAnythingelsebothering

you?

Nothingofconcern,butIdodrinkalotandpeea

lot,doc...BP110/60HR102Temp39.1CRR30SpO289%onRA

RalesonLlungbaseLLLinfiltrateonCXRAdmitthepaVentAnVbioVcsforpneumonia

John,45y/oM

Day0

Acuterespiratoryfailure->IntubaVon

PNa140mEq/L

Day4(SVllintubated)

PNa=165mEq/L

UOP=4L;Weight=70kg

Uosm=130mOsm/kg

UNa=25mEq/L;UK=30mEq/L

JohnislosingwaterbasedonhisrisingPNa.

Heisdependinguponyoutoreplenishhim.

Youwanttofindouthisfreewaterdeficit.

NaE TBW

FREEWATERDEFICIT

Hypernatremia=Waterloss+INABILITYTODRINKWATER

So,whatisafreewaterdeficit?

Freewaterdeficit=Normaltotalbodywater–Currenttotalbodywater

Freewaterdeficit=CurrenttotalbodywaterPNa_

140

Freewaterdeficit=60%of70kg165 =7.5L

140

X _ 1

X 1

RapidcorrecVonofhypernatremia

Cerebraledema

Seizures

Permanentneurologicaldamage

Death

165–140=25mEq/L

25mEq/L÷10mEq/L/day=2.5days

2.5daysx24hrs/day=60hours

RateofD5W=7500ml/60hours=125ml/h

PNaishigherthannormalby…

So,ifyoucorrectitbymaximumof10mEq/L/day…

24hoursinaday…

Alrightthen,7500mLover60hours…

“Well,notmorethan10mEq/L

over24hours!”

BUTdespitethisPNaincreasesto167mEq/Lat24hours!

H2O

H2O H2O

WHAT CAUSED THE HYPERNATREMIA?

ONGOINGWATERLOSSES

Stool Skin Urine

≈40mL/h CalculateElectrolyteFree-WaterClearance

=4Lx1-25+30=2.666L/day=111mL/h

165

UNa+UK

PNa‘Electrolyte-free’waterclearance=Vx 1-

PUTTING EVERYTHING TOGETHER…

125ml/h(Freewaterdeficit)+

40ml/h(Ongoinglossesinstoolandskin)+

__________111ml/h(Ongoinglossintheurine)________

276ml/h

6624mlover24hours(1Lenterally/day,D5Wat234ml/h)

TAKE HOME POINTS:

WHEN TREATING HYPERNATREMIA…

•  CalculateFreeWaterDeficit

PNa

140

UNa+UK

PNa‘Electrolyte-free’waterclearance=Vx 1-

Freewaterdeficit=CurrenttotalbodywaterX -1

•  KeepgoalcorrecVonunder10mEq/Lperday

•  Don’tforgettoaddongoinglosses