Fluids & Electrolytes and Nutrition

1. Fluids & Electrolytes and Nutrition Srinivas H Reddy, MD Trauma & Surgical Critical Care Jacobi Medical Center

2. Fluids & Electrolytes

3. “The recognition and management of fluid, electrolyte, and related acid-base problems are common challenges on the surgical service.” Lawrence, P F,Essentials of General Surgery, 4th ed., 2005

4. Goals • Review concept of total body fluids • Review types of crystalloids and colloids • Review electrolyte disturbances & their treatment strategies • Review acid-base disturbances

5. 25% 8% 67% 33% Na-K ATPase

6. Na+/K+ ATPase Actively pumps 3 Na+ out of cell and 2K+ inside cell Energy from ATP Regulated by Insulin Aldosterone

7. Starling’s Forces

9. Cations and Anions in Body Fluids

10. Serum Osmolality = [2 x Na] + [BUN/2.8] + [Gluc/18]

11. Osmolality = CONCENTRATION Tonicity = ONCOTIC PRESSURE FORCE ON WATER

12. Primary Regulatory Hormones Antidiuretic hormone (ADH, Vasopressin) • Stimulates kidney to resorb water from collecting ducts • Causes systemic vasoconstriction • Stimulates thirst center Aldosterone • Stimulates Na+ (& water) absorption and K+ loss along the DCT • Similar action on distal colon Natriuretic peptides (ANP and BNP) • Reduce thirst and block the release of ADH and aldosterone

13. Renin-Angiotensin-Aldosterone System

14. Renin-Angiotensin-Aldosterone System

17. 25% 8% 67% 33% Na-K ATPase

18. GI Fluid & Electrolyte Losses

19. Lactated Ringers / Normal Saline • Normal Saline (NS) • Does not contain calcium, may be used to carry PRBC transfusion • Hyperchloremic metabolic acidosis after aggressive resuscitation • pH = 5.5 • Lactated Ringers (LR) • Sydney Ringer’s frog hearts (London 1882) • Alexis Hartman pediatric cholera, added bicarbonate (US 1930’s) • Lactate -> Pyruvate -> Bicarbonate • Lactic Acidosis? • Immunosuppressive effect on WBC’s? • Calcium precipitates with citrate in PRBC transfusion • pH=6.5

20. Maintenance Fluids • Formula per day • 100mL/kg/d x first 10kg • 50mL/kg/d x next 10kg • 25mL/kg/d x each addl kg • Formula per hour • 4mL/kg/hr x first 10kg • 2mL/kg/hr x next 10kg • 1mL/kg/hr x each addl kg • “4-2-1 Rule - per hr”

21. Maintenance Electrolytes Sodium • 1-2 mEq/kg/day Chloride • 1-2 mEq/kg/day Potassium • 0.5-1 mEq/kg/day Calcium • 800 - 1200 mg/d Magnesium • 300 - 400 mg/d Phosphorus • 800 - 1200 mg/d

22. Normal Serum Electrolytes Cations Sodium (mEq/L) 135 - 145 Potassium (mEq/L) 3.5 - 4.5 Calcium (mg/dL) 4.0 - 5.5 Magnesium (mEq/L) 1.5 - 2.5 Anions Chloride (mEq/L) 95 - 105 CO2 (mmol/L) 24 - 30 Phosphate (mg/dL) 2.5 - 4.5

23. Fluid Status SIADH Hypothyroid Cortisol GI loss CHF Cirrhosis 120 140 140 [Na] GI loss Renal loss Osmotic NaHCO3 3% NaCl Seawater 160 DI Insensible high low normal ECV

24. Composition of IV Fluid Solutions Solution Na+ Cl- K+ Ca+2 HCO3- Gluc Plasma 141 103 4-5 5 26 0 NS 154 154 0 0 0 0 LR 130 109 4 3 28 0 D5W 0 0 0 0 0 50g D5 1/2NS+20KCl 77 77 20 0 0 50g Serum Osmolality = [2 x Na] + [BUN/2.8] + [glucose/18]

25. Replacement Fluid Strategies • Sweat: D5¼NS + 5mEq KCl • Gastric: D5½NS + 20mEq KCl • Biliary/Pancreatic: LR • Small Bowel: LR • Colon: LR • 3rd space losses: LR

26. Resuscitation • Crystalloids first, initial bolus 20mL/kg (1-2L), may be repeated, usually NS or LR • If they have transient response, give additional fluids • Once 3-4 liters of crystalloid has been given consider blood • Current recommendations in hemorrhagic shock from trauma, transfuse 1:1 PRBC:FFP (previously, and for other bleeds 3:1 ratio)

27. Fluid Pearls Resuscitation – isotonic fluid (LR or NS), no dextrose, if ongoing losses consider using colloid Post-op – LR or NS until pt euvolemic, then switch to maintenance Bolus – isotonic fluid, no dextrose Mobilization – movement of fluid from 3rd space into intravascular space

28. Indicators of Successful Resuscitation • PULSE <100 - 120 bpm • URINE OUTPUT • Child >1.0 ml/kg/hr • Adult >0.5 ml/kg/hr • Clearance of LACTATE • Resolution of BASE DEFICIT • BLOOD PRESSURE is a POOR INDICATOR!

29. Hypovolemia Acute volume loss Tachycardia Hypotension Decreased UO Changes in mental status Gradual volume loss Loss of skin turgor, dry mucus membranes Thirst Low CVP Hemoconcentration (Hct rise) BUN:Cr ( >20:1) Metabolic acidosis due to hypoperfusion

30. Hypervolemia Large UO Pitting edema JVD Crackles on lung auscultation Hypoxia CXR – cephalization of vessels, pulmonary edema

31. Hyponatremia Serum Na+ < 130mEq/L Sx- nausea, emesis, weakness, altered MS, seizure May be hypovolemic, euvolemic, or hypervolemic Tx Fluid restriction Replete with Normal Saline For severe hyponatremia <120-125mEq/L and/or mental status changes, use Hypertonic Saline Remember: do NOT correct faster than 0.5 mEq/L/hr to avoid central pontine myelinolysis

32. Causes of Hyponatremia • Hypovolemic • Causes – Na+ and water are lost and replaced with hypotonic solutions • Renal – salt wasting nephropathy • GI – diarrhea, vomiting, fistulas • Skin – excessive sweating • 3rd spacing – ascites, peritonitis, pancreatitis, burns • Hypoaldosteronism • Euvolemic • Causes – SIADH, psychogenic polydipsia • Hypervolemic • Causes - renal failure, nephrotic synd, CHF, cirrhosis

33. Hypernatremia Serum Na+ > 145 Sx – altered level of consciousness, seizure, coma, signs of dehydration Causes – DI, hyperosmolar diuresis, EtOH (suppresses ADH) Txcalculate Free Water Deficit FWD = 0.6 x wt (kg) x (measured Na+ - 140) / 140 Replace first ½ in 24hrs, then 2nd ½ in next 24 hrs No faster than 10mEq/day to avoid cerebral edema Use D5W, ½ NS, or ¼ NS

34. Hypokalemia K+ < 3.5 Sx – fatigue, weakness, ileus, N/V, arrhythmia, rhabdomylosis, flaccid paralysis, resp compromise EKG changes - long QT, depressed ST, low T waves, U waves Causes – vomiting, NGT drainage, diarrhea, high output enteric/pancreatic fistula, hyperaldosteronism, loop diuretics Tx – replete 10 mEq KCl for every 0.1 below 4.0, oral or IV not more than 10-20mEq/hr, if persistent hypokalemia, may also need Mg 2+ replacement, also available K phos or K acetate

35. Hyperkalemia K+ > 5.0 Sx – weakness, N/V, abdominal cramping, diarrhea, arrhythmias EKG – peaked T waves, prolonged PR, widened QRS, V-fib, diastolic cardiac arrest Causes – iatrogenic, renal failure, acidosis, hemolysis, crush injury, reperfusion injury Tx

36. Treatment of Hyperkalemia • Cardiac monitoring, EKG • If EKG changes, give Calcium gluconate or chloride (stabilizes cardiac membrane) CaCl : CaGluc = 3 : 1 elemental calcium • Dextrose and Insulin • Bicarbonate • Albuterol • Kayexalate • Renal Replacement Therapy (Dialysis)

37. Hypocalcemia Ca2+ < 8.5 Sx – parasthesias, muscle spasms, tetany, seizures, Chvostek, Trousseau EKG – prolonged QT, can progress to complete heart block or V-fib Causes – pancreatitis, tumor lysis syndrome, blood transfusion, renal failure, thyroid or parathyroid surgery, diet deficient in Vit D or Ca, inability to absorb fat-soluble vitamins Tx – chronic hypocalcemia give supplemental oral calcium & vitamin D, and for symptomatic hypocalcemia, give IV calcium ± PO calcium/vit D

38. Hypercalcemia Ca2+ > 10.5 Sx – stones, moans, groans, psychologic overtones Causes – ‘CHIMPANZEES’ Tx – Identify and treat cause Severe/symptomatic hypercalcemia, treat with IVF, diuretics (saline diuresis) Bisphosphonates, if due to release of Ca2+ from bone

39. Acid / Base Respiratory Acidosis Metabolic Alkalosis BE = 0 HCO3 = 24 Respiratory Alkalosis Metabolic Acidosis 7.4

40. Acid-Base Disturbances

41. Mechanisms Regulating Acid-Base Balance • Chemical buffers in cells and ECF • Instanteous action • Combine acids or bases added to the system to prevent marked changes in pH • Respiratory System • Minutes to hours in action • Controls CO2 concentration in ECF by changes in rate and depth of respiration • Kidneys • Hours to days in action • Increases or decreases amount of NaHCO3 in ECF

42. Buffer Mechanisms of pH Control • Buffer system consists of a weak acid and its anion • Three major buffering systems: • Protein buffer system • Amino acid • H+ are buffered by hemoglobin buffer system • Carbonic acid-bicarbonate • Buffer changes caused by organic and fixed acids • Phosphate • Buffer pH in the ICF

43. Relationship between PCO2 and Plasma pH

44. Central Role of Carbonic Acid-Bicarbonate Buffer System in Regulation of Plasma pH

45. Central Role of Carbonic Acid-Bicarbonate Buffer System in Regulation of Plasma pH

46. ABG Rules • Rule #1: increase or decrease in PaCO2 of 10 mm Hg, is associated with a reciprocal decrease or increase of 0.08 pH • Rule #2: increase or decrease in HCO3- of 10 mEq/L is associated with a directly-related increase or decrease of 0.15 pH

47. Severe Acidosis pH < 7.2 • decreased responsiveness to catecholamines • cardiac dysfunction • arrhythmias • increased potassium serum levels

48. Nutrition

49. Goals • Why important? • What nutrients are needed? • How much nutrition is necessary? • How to administer nutrition to patient?

50. Why Nutrition? • Growth • Immunity • Wound healing