Interactive session on Sodium Homeostasis

Dr.M.Emmanuel Bhaskar

Assistant Professor in Medicine

SRMC & RI

Plan for Interaction

• Presentation of scenario-1.

• 7 Interactive questions followed by answers for the same

• Presentation of scenario-2.

• 3 Interactive questions followed by answers for the same

• Questioning by the delegates.

Approach to Hyponatremia…

My first question

Sir…What should I read to evaluate and treat Sodium imbalance

Good…read about behaviour of……….

…….water!!

Scenario-1

A 55 yr old lady with complaints of :

Fever and Cough with expectoration-5 dys

Altered behaviour-8 hours

Examination

An Unconscious patient with preserved brain

Stem reflexes, preserved perception of deep

Stimuli and hemodynamically stable

Other systems unremarkable

Investigations

In the Emergency Room:

CBG- 125 mg/Dl

ABG-Ph:7.46 , PCo2-26 mmHg,

HCO3-21meq/L, Pao2-110 mmHg

Investigations

CXR-PA View:Rt Upper lobe consolidation

Hb%-12 g/dl Na-106 meq/l

TC-20,000 cells K- 3.6 meq/l

DC-P 75 L 20 E 5 Cl-92 meq/l

Creatinine-1 mg/dl HCo3-20 meq/l

BUN-8mg/dl S.Osmolality-213 osm

Urine:Specific gravity:1.015 Ph: 5.0 Sugar :Nil Albumin- trace Pus cells-4-5, no castsUrinary spot Na- 80 meq/L

CT-Brain –Normal CSF- Normal

1.Comment on the scenario withstress on hyponatremia

Summary

Euvolemic symptomatic hyponatremia

Serum Hypo-osmolality

Normal urine specific gravity

Urinary spot Na-80 meq/L

Possibilities to be considered

SIADH

Cerebral / Renal salt wasting with

subclinical hypovolemia.

2.How to diagnose SIADH

Diagnosis of SIADH

Euvolemia

↓Serum Osmolality [<275 mOsm/kg]

↑Urine Osmolality [ >100 mOsm/kg ]

Spot urinary Na > 40 meq/L

Diagnosis of SIADH

Euvolemia

More water in serum

Inappropriately Less water in urine

Abnormal urinary sodium loss

Practical Problems in diagnosing SIADH

By definition serum and urine osmolality should be measured

But most of us get only the calculated value

Practical way of diagnosing SIADH

-Euvolemia-Calculated serum.osmolality is as good as

measured , except in cases of CRF and toxin intake.

-Urine specific gravity may be used in place of urine osmolality [newer methods

eliminates sugar and protein ] -Urine Na >40 meq/L

How to use urine sp.gravity to diagnose SIADH

When serum osmolality↓ the appropriate

Urine specific gravity must be <1.005

A specific gravity of >1.005 indicates a

Urine osmolality >100 mOsm/kg

Our Patient

Euvolemic

Serum osmolality-213 mOsm

Urine specific gravity-1.015

Urinary Na- 80 meq/L

3.Conditions to be ruled out when SIADH is suspected

Conditions to be ruled out when SIADH is suspected

Adrenal Insufficiency

Hypothyroidism

Diuretic use

CSW / RSW with sub-clinical hypovolemia

SIADH vs CSW/RSW

How to differentiate???

SIADH vs Wasting Hyponatremia

CSW/RSW is a volume contracted state

But in early stages hypovolemia-subclinical

↑BUN in CSW / RSW ,N or ↓BUN in SIADH

Urinary Na>150 meq points to Na wasting

Our Patient has SIADH

4.What is the plan of Na correction over the next 24 hours

Plan of Na correction over the next 24 hours

0.75 meq/hour for 8 hours= 6meq over 8hr

If appropriate response occurs,

0.20 meq/hour for 16 hours=3meq over 16h

Total=9 meq over 24 hours

5.What is the infusate and how to decide the rate per hour ?

Adrogue-Madias Formula???

Adrogue-Madias Formula

Overcorrects the Na in 60% of cases

Required modification

A correction factor was evolved.

Volume of infusate to attain the desired Na value

Body water X Desired increment in Na

Infusate Na X 1.5

3% NaCl- 513 meq/L

0.9% NaCl- 154 meq/L

Plan for the first 8 hours

Body water X Desired increment in Na

Infusate Na X 1.5

30x6 = 0.23 litre or 230 ml

513X1.5

230 ml in 8 hours=30 ml/hour

For the next 16 hours

If appropriate response occurs over the

first 8 hours, then

3 meq/L increment in Na next 16 hours

120 ml over 16 hours = 8 ml/hour next 16h

6.When does overcorrection occur ?

When does overcorrection occur

Failure to diagnose subclinical hypovolemia

Caused by a wasting syndrome

Sub-clinical hypovolemia can be effectively diagnosed using BUN.

7.When does undercorrection occur ?

When does undercorrection occur

In SIADH:

-Failure to restrict fluids < 1 liter/24 hours

-Excessive 0.9% saline administration

leads to selective water retention due to

the action of ADH.This blunts the response

to hypertonic saline.

Hyponatremia-Summary

• SIADH can be diagnosed using calculated serum osmolality and urine sp.gravity

• Rule out Adrenal insuff,hypothy,wasting hyponat with subclinical hypovolemia

• BUN helps to identify subclin hypovol

• 0.75 meq – 8 hours and subseq slow corr

• Causes of inappropriate correction

Scenario-2

A 75 yr old man admitted with

Impaired level of Consciousness-24 hours

This was preceded by fatigue and impaired

Ambulation for 3 days.

On Examination:

An Unconscious patient responding to deep

Stimuli

Other systems were unremarkable

Investigations

In ER:

CBG-98 mg/dl

ABG-Normal

Investigations

Hb%-16 g/dl Na-158meq/l

PCV-42 K- 4 meq/l

TC-10,000 cells Cl-106 meq/l

HCo3-26meq/l

Creatinine-1.3 meq/l

BUN-28 mg/dl CT-Brain:Normal

CSF: Normal

Comment on the Scenario

Comment on the Scenario

Symptomatic Hypernatremia

Probably due to inadequate water intake

1.What is the plan for Na correction ?

Comment on volume and fluid to be administered, rate of correction

Plan for Na correction

Step 1: Calculate water deficit

??????

Plan for Na correction

Step 1: Calculate water deficit

Patient Na-140 X Body water

140

158-140 X 30 = 4 litres

140

Plan for Na correction

Step 2: Decide on Fluid to be administered

??????????

Plan for Na correction

Step 2: Decide on Fluid to be administered

-Free water through ryles tube

-i.v 5% Dextrose

-i.v 0.45% Saline

Advantages and Disadvantages???

Plan for Na correction

Step 3: Rate of correction

??????????

Plan for Na correction

Step 3: Rate of correction

-0.5 meq/hour

- less than 12 meq/day

2.How to correct?

Formulae ??????

Formulae for Hypernatremia

-Formulae for determining infusate rate

may not be clinically useful.

WHY???

-Correction depends on renal handling of

administered water. This may be unique

for a given patient

A helpful protocol for correction

-Holds good if renal handling is normal -Na<165 meq/L

Administer 50% of water deficit-36 hrsIf appropriate response occurs,Remaining 50% of water deficit-36 hrs

For Our Patient

2 litres[free water or 5% Dex]-36 hours

If appropriate response occurs,

2 litres[free water or 5% Dex]-36hours

3.Can you predict impaired response to treatment

Can you predict impaired response to treatment

Indicators of poor response after initiating treatment:

Urine output > 2ml/kg/hour

Urine specific gravity < 1.010

Can you predict impaired response to treatment

Indicators of poor response after initiating treatment:

Urine output > 2ml/kg/hour

Urine specific gravity < 1.010

INAPPROPRIATE WATER IN URINE

Hypernatremia -Summary

• Calculate water deficit

• Decide on fluid to be administered

• Correction depends on renal handling of administered water. Formulae less useful.

• A 50+50 approach over 72 hours.

• High urine output and a dilute urine indicates a possible poor resp to treatment

To treat dysnatremias you need to know little about sodium more

about water……………….look at the urine of our patient. It solves most of your

problems

Questions?????