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Copy of my slides made for an interactive discussion on hyponatremia
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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?????