Lab Rounds

Shawn Dowling PGY-2

Case

     78 yo M. Brought in by EMS from NSG home c/o generalized weakness, V, D for past 2-3 days Brief GTC seizure while nurses are checking patient in PMHx: HTN (on HCTZ), allergies: ex-wife

Physical Exam

     VS: HR-110, BP110/70, T/RR/sats N Stopped seizing but still altered sensorium (?post-ictal), GCS 13-14 Fluid: looks dry Chest/abdo/extremeties – N Neuro: no focal abnormalities, neck supple

Want to order anything NOW?

Want to order anything NOW?

 Chemstrip

Want to order anything NOW?

  Chemstrip The paramedics had noticed this by his bedside

Want to order anything NOW?

  Chemstrip – 8.0

ABG  Na – 108, K - 3.0, Cl - 90

Objectives

 Acute Hyponatremia     Touch of physiology DDx

The Na calculating game How and when to use HTS

 FOR INDEPTH REVIEW OF HYPONATREMIA SEE MORITZ’S PRESENTATION FROM 2003

Sodium

  H 2 0 makes up  60% of total body weight (:. TBW = 0.6 x wgt(kg))  H 2 0 is distributed between 3 compartments 

Intracellular space (ICS)

  Interstitial space (ISS) Intravascular space (IVS)

Extracellular Space

Na is the predominant cation in the ECS and is distributed primarily in the TBW

   Na + balance primarily controlled by renin-angiotensin-aldosterone system Na governs the movement of fluid between these compartments Water balance largely driven by Na + balance and ADH

Fluid Distribution

TBW = wgt (kg) x 0.6

Distribution of TBW (and Na): Intracellular (2/3) Extracellular (1/3)

IVS (1/3) ISS (2/3)

Hyponatremia DDx

(abridged version)

 “TRUE”   Na Hypovolemic    GI/insensible losses Poor H 2 0 intake Diuretics   Euvolemic  SIADH  Psychogenic polydipsia Hypervolemic    CHF Cirrhosis Nephrotic syndrome    Lab Error Pseudo  Na*   lipids/proteins  No longer an issue Redistributive (  osm)   Hyperglycemia Mannitol *No longer an issue since the lab uses a different technique to calculate Na

Making the Diagnosis

   Hx in particular ROS, PMHx, Meds Physical exam: hypo-,eu- or hypervolemic Labs:   Serum electrolytes (ABG if needed urgently) Urine lytes, Cr (if not on diuretics or have not received fluids yet)   Urine Osmols Serum Glucose

Approach to sodium

 1.

2.

3.

Need to determine: Is the patient symptomatic?

  Is this an acute or chronic process?

 Do I need to intervene emergently?

Seizure?

Comatose?

Focal Neuro Deficits?

S/Sx



Sx

  HA Lethargy     N,V Anorexia Dizzy Confusion 

Signs

  Psychosis Confusion     Focal Neuro deficits Ataxia Seizures Comatose

 37M. Diabetic.

   Glucose 35 Na – 126 How do you correct the sodium for the glucose?

Back to our case

   His Na is 108.

What info do you need to calculate his Na deficit?

What is his Na deficit?

Fluid Distribution

TBW = wgt (kg) x 0.6

Distribution of TBW: Intracellular (2/3) Extracellular (1/3)

IVS (1/3) ISS (2/3)

Calculating Na deficit

   His wgt is 60kg.

Since Na is primarily distributed in the Total body water which is wgt(kg) x 0.6* (Desired Na-actual Na) x TBW Or 

The drop in Na x where the Na is distributed

***Some sources suggest using 0.5 for females/elderly males and 0.45 for elderly females – probably not important acutely

 (140-108) x 0.6x60kg

= (32) x 36 =1152mEq of Na    How quickly can we replace Na? Why?

How are we going to calculate how much to replace over 24 hours?

What solution are you going to use?

 Pt is not seizing, no focal deficits, no coma

Na correction

  CANNOT correct sodium quicker than 10-12mEq/24 hours,  0.5 mEq/hr rule is not absolute – this rule can be broken as long as 10-12/day is not Risk of over-aggressive Na replacement is central pontine myelinolysis  Demyelination of the pons, flaccid paralysis and death -- BAD

Determining how much Na to give

 What is the Na content of…    NS RL HTS (3%)

Determining how much Na to give

 What is the Na content of…    NS – 154mEq RL – 130mEq HTS (3%) – 513mEq

Calculating volume of fluid

   His Na deficit is 1152mEq, but we only want to increase 10-12mEq/24H (Desired Na-actual Na) x TBW   (118-108) x 36 360mEq NS 360/154 = 2.33 L over next 24 hours – check lytes Q2-4H to ensure not correcting too quickly

The Divine Brine – HTS

 HTS (3%) – Na content is 513mEq  Indications     Moderate-Severe hyponatremia (<120) And 1 of the following    Seizures Focal neuro deficit Comatose Dose: 3cc/kg ½ half given over 10 minutes, 2 nd ½ given over 50 minutes Then STOP & check lytes (usually  Na by 3 6mEq). STILL LTD BY 10-12mEq/DAY

Summary

1.

2.

3.

4.

 Order Urine lytes prior to giving fluid Calculate target Na (Goal Na - actual Na) x TBW & DO NOT EXCEED   HTS saline indications Seizure Focal neuro deficits  Comatose  HTS: 3cc/kg, 1 st ½ over 10min, 2 nd ½ over next fifty minutes, then STOP & check lytes Usu  by 3-6 mEq, STILL ltd by 10-12mEq/24hrs

References

     EMRAP March 2006 Yeates K. Salt and Water: A simple Approach. CMAJ . Feb 2004;170, 365-69 Rosen’s Harrison’s Moritz’s presentation 2003