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Lab Rounds

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

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Lab Rounds

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  1. Lab Rounds Shawn Dowling PGY-2

  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

  3. 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

  4. Want to order anything NOW?

  5. Want to order anything NOW? • Chemstrip

  6. Want to order anything NOW? • Chemstrip • The paramedics had noticed this by his bedside

  7. Want to order anything NOW? • Chemstrip – 8.0 • ABG • Na – 108, K - 3.0, Cl - 90

  8. 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

  9. Sodium • H20 makes up  60% of total body weight (:. TBW = 0.6 x wgt(kg)) • H20 is distributed between 3 compartments • Intracellular space (ICS) • Interstitial space (ISS) • Intravascular space (IVS) • Na is the predominant cation in the ECS and is distributed primarily in the TBW Extracellular Space

  10. Na+ balance primarily controlled by renin-angiotensin-aldosteronesystem • Na governs the movement of fluid between these compartments • Water balance largely driven by Na+ balanceand ADH

  11. Fluid Distribution TBW = wgt (kg) x 0.6 Distribution of TBW (and Na):

  12. “TRUE”  Na Hypovolemic GI/insensible losses Poor H20 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 Hyponatremia DDx(abridged version)

  13. 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

  14. Approach to sodium • 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?

  15. Sx HA Lethargy N,V Anorexia Dizzy Confusion Signs Psychosis Confusion Focal Neuro deficits Ataxia Seizures Comatose S/Sx

  16. 37M. Diabetic. • Glucose 35 • Na – 126 • How do you correct the sodium for the glucose?

  17. Back to our case • His Na is 108. • What info do you need to calculate his Na deficit? • What is his Na deficit?

  18. Fluid Distribution TBW = wgt (kg) x 0.6 Distribution of TBW:

  19. 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

  20. (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

  21. 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

  22. Determining how much Na to give • What is the Na content of… • NS • RL • HTS (3%)

  23. Determining how much Na to give • What is the Na content of… • NS – 154mEq • RL – 130mEq • HTS (3%) – 513mEq

  24. 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

  25. 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, 2nd ½ given over 50 minutes • Then STOP & check lytes (usually  Na by 3-6mEq). STILL LTD BY 10-12mEq/DAY

  26. Summary • 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, 1st ½ over 10min, 2nd ½ over next fifty minutes, then STOP & check lytes • Usu by 3-6 mEq, STILL ltd by 10-12mEq/24hrs

  27. 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

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