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Basic Fluids and Electrolytes

Basic Fluids and Electrolytes. Douglas P. Slakey. Why ? . Essential for surgeons (and all physicians) Based upon physiology Disturbances understood as pathophysiology To Encourage Thought Not Mechanical Reaction Most abnormalities are relatively simple, and many iatrogenic.

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Basic Fluids and Electrolytes

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  1. Basic Fluids and Electrolytes Douglas P. Slakey

  2. Why ? • Essential for surgeons (and all physicians) • Based upon physiology • Disturbances understood as pathophysiology To Encourage Thought Not Mechanical Reaction Most abnormalities are relatively simple, and many iatrogenic

  3. It’s All About Balance • Gains and Losses • Losses • Sensible and Insensible • Typical adult, typical day • Skin 600 ml • Lungs 400 ml • Kidneys 1500 ml • Feces 100 ml • Balance can be dramatically impacted by illness and medical care

  4. Fluid Compartments • Total Body Water • Relatively constant • Depends upon fat content and varies with age • Men 60% (neonate 80%, 70 year old 45%) • Women 50%

  5. TOTAL BODY WATER 60% BODY WEIGHT ECF 1/3 ICF 2/3 H2O Predominant solute K+ Predominant solute Na+

  6. I Love Salt Water!

  7. Electrolytes (mEq/L) Plasma Intracellular Na 140 12 K 4 150 Ca 50.0000001 Mg 2 7 Cl 103 3 HCO3 24 10 Protein 16 40

  8. Fluid Movement • Is a continuous process • Diffusion • Solutes move from high to low concentration • Osmosis • Fluid moves from low to high solute concentration. • Active Transport • Solutes kept in high concentration compartment • Requires ATP

  9. Movement of Water • Osmotic activity • Most important factor • Determined by concentration of solutes Plasma (mOsm/L) 2 X Na + Glc + BUN 18 2.8

  10. Third Space • Abnormal shifts of fluid into tissues • Not readily exchangeable • Etiologies • Tissue trauma • Burns • Sepsis

  11. Fluid Status • Blood pressure • Check for orthostatic changes • Physical exam • Invasive monitoring • Arterial line • CVP • PA catheter • Foley

  12. Case 1 • 6 month old boy, born full-term • Developed worsening vomiting during the past week • Today he is listless, irritable, not tolerating oral intake • Pulse 145, BP 70/50 • Diaper is dry, anterior fontanel depressed

  13. Case 1 Labs 200 12.3

  14. Case 1 F & E Problem List • Hypovolemia • Hypernatremia • Hypokalemia • Alkalosis

  15. Volume Deficit • Most common surgical disorder • Signs and symptoms • CNS: sleepiness, apathy, reflexes, coma • GI: anorexia, N/V, ileus • CV: orthostatic hypotension, tachycardia with peripheral pulses • Skin: turgor • Metabolic: temperature

  16. Dehydration ChronicVolume Depletion Affects all fluid components Solutes become concentrated Increased osmolarity Hct can increase 6-8 pts for 1 L deficit Patients at risk: Cannot respond to thirst stimuli Diabetes insipidus Treatment: typically low Na fluids

  17. HypovolemiaAcute Volume Depletion Isotonic fluid loss, from extracellular compartment Determine etiology Hemorrhage, NG, fistulas, aggressive diuretic therapy Third space shifting, burns, crush injuries, ascites Replace with blood/isotonic fluid • Appropriate monitoring • Physical Exam • Foley (u/o > 0.5 ml/kg/min) • Hemodynamic monitoring

  18. Treatment – Patient weight is 12 kg • Fluid choice? • Replace volume • Replace Cl • How to order • “Bolus” • Think about rate over time • Adequate access important • What would maintenance fluid choice and rate be? • 4-2-1 rule • Why not replace K right away?

  19. Acid – Base Balance • Acidosis • May result from decreased perfusion i.e. decreased intravascular volume • K will move out of cells • Alkalosis • Complex physiologic response to more chronic volume depletion • i.e. vomiting, NG suction, pyloric stenosis, diuretics • K will move intracellular

  20. Paradoxical Aciduria Hypochloremic Hypovolemia Na Na H Cl K Loop of Henle

  21. Case 1 When should we operate? • Need to wait until adequately resuscitated • Why • Monitor by: • Normalized vital signs • Good urine output • Normalized labs

  22. Case 2 • 64 year old, had colon resection 5 days ago • “doing well” ….until…. • Suddenly develops atrial fibrillation with rapid ventricular response • P 120, irregular; BP 115/70; RR 20 • Temp 38.7 • Confused, anxious

  23. Case 2 Labs Mg 1.1 180 16.3

  24. Case 2 • Diagnoses? • New onset A fib, why? • Hypervolemia • Hyponatremia • Hypokalemia • Hypomagnesemia • Anemia

  25. Case 2 • Why does patient have hypervolemia?

  26. Increased Antidiuretic Hormone (ADH) • Causes • Surgical stress (physiologic) • Cancers (pancreas, oat cell) • CNS (trauma, stroke) • Pulmonary (tumors, asthma, COPD) • Medications • Anticonvulsants, antineoplastics, antipsychotics, sedatives (morphine)

  27. Hyponatremia – how to classify • Na loss • True loss of Na • Dilutional (water excess) • Inadequate Na intake • Classified by extracellular volume • Hyovolemic (hyponatremia) • Diuretics, renal, NG, burns • Isotonic (hyponatremia) • Liver failure, heart failure, excessive hypotonic IVF • Hypervolemic (hyponatremia) • Glucocorticoid deficiency, hypothyroidism

  28. Patient was receiving maintenance Fluids D5 0.45NS + 20 mEq KCl/L at 125 ml/hr

  29. How much Sodium is Enough??? • NS • 0.9% = 9 grams Na per liter • 0.45 NS = 4.5 grams per liter • 125 ml/hour = 3000 ml in 24 hours • 3 liters X 4.5 grams Na = 13.5 GRAMS Na! • (If 0.2 NS: 3 liters X 2 grams Na = 6 grams Na)

  30. Case 2 - How to treat • A fib: ACLS protocol • Correct electrolytes • Replace Mg and K • Decrease volume, fluid restriction

  31. Case 3 • 23 year old with jejunostomy • Had colon and ileum resected due to injury • Tolerates some oral nutrition, but has high output from jejunostomy (2.5 liters per day), therefore requires TPN • P 118, BP 105/60

  32. Case 3 Labs Glucose 213 Mg 1.4 380 10.3

  33. Current Problems • Hypovolemia • Increased plasma osmolarity • 2 X 154 + (213/18) + (28/2.8) = 329.8 • Hypernatremia • Renal insufficiency • Acidosis

  34. Case 3 - Hypovolemia • Fistula output • High volumes can rapidly lead to dehydration • Electrolyte composition can be difficult to estimate • Can send aliquot to laboratory • May need to be replaced separately from maintenance (TPN) fluids • Hyperglycemia

  35. Hypernatremia Relatively too little H2O • Free water loss (burns, fever, fistulas) • Diabetes insipidus (head trauma, surgery, infections, neoplasm) • Dilute urine (Opposite of SIADH) • Osmotic diuresis • Nephrogenic DI • Kidney cannot respond to ADH • Too much Na, usually iatrogenic

  36. Hypernatremia Free water deficit: [0.6 X wt (kg)] X [Serum Na/140 - 1] Example: Na 154, 60 kg person (0.6 X 60) X [(154/140) - 1] X [1.1 -1] 36 X 0.1 = 3.6 Liters

  37. Case 3 – How to Treat • Correct hyperglycemia • Replace pre-existing volume deficits • Reduce ostomy output if possible • What to do with: • Acidosis? • Hypokalemia?

  38. Case 4 • 58 year old, had a recent kidney transplant • Laboratory calls with critical value: • Potassium 5.9 • What to do?

  39. Case 4 • Evaluate the patient • Exam • ECG • Order repeat labs

  40. Hyperkalemia - Common Causes • Spurious • Blood drawn above running IV • Underlying disease • Renal failure • Rhabdomyolysis • Associated medications • Too much K+, ACE inhibitors, beta-blockers, antibiotics, chemotherapy, NSAIDS, spironolactone

  41. Treatment • Mild: dietary restriction, assess medications • Moderate: Kayexalate • Do not use sorbitol enema in renal failure patients • Severe: dialysis

  42. Potassium and Ph • Normally 98% intracellular • Acidosis • Extracellular H+ increases, H+ moves intracellular, forcing K+ extracellular • Alkalosis • Intracellular H+ decreases, K+ moves into cells (to keep intracellular fluid neutral)

  43. Hyperkalemia - Treatment • Emergency (> 6 mEq/l) • Monitor ECG, VS • Calcium gluconate IV (arrhythmias) • Insulin and glucose IV • Kayexalate, Lasix + IVF, dialysis • Mild to Moderate • Mild: dietary restriction, assess medications • Moderate: Kayexalate • Do not use sorbitol enema in renal failure patients • Severe: dialysis

  44. The End Makani U’i

  45. Remember JVD?

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