Fluids and Electrolytes for surgeons

1. Fluids and Electrolytes for surgeons Anil S. Paramesh MD, FACS Associate Professor of Surgery, Urology and Pediatrics

2. Why ? • Essential for surgeons (and all physicians) • Knowledge can diagnose, treat and prevent many of the problems in surgical patients Most abnormalities are relatively simple, and many iatrogenic

3. 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%

4. TOTAL BODY WATER 60% BODY WEIGHT ECF 1/3 (20% BW) ICF 2/3 (40% BW) H2O Predominant solute K+ Predominant solute Na+ 75% interstitial 25% intravascular (5% of BW)

5. It’s All About Balance • Gains and Losses • Most individuals ingest approx 2 – 2.5 L/day • 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

6. How much fluid can a patient lose if a patient could lose fluid? • Sensible losses • Blood (most pts can tolerate 500 cc BL) • Sweat (up to 4 L /day) • Tears – (diarrhea) • Insensible losses • Skin 250 cc/day/degree fever • Trach/vent – upto 1500 cc/day • Peritoneum - > 1/day • Third spacing

7. I Love Salt Water!

8. 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 • Gibbs-Donnan equation – product of diffusible an/cations same on both sides of SP membrane

9. 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

10. Movement of Water • Osmotic activity • Normal around 300 mOsm/L • Osmolality determined by concentration of solutes Plasma (mOsm/L) 2 X Na + Glc + BUN 18 2.8

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

12. 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

13. HypovolemiaAcute Volume Depletion Determine etiology Hemorrhage, NG, fistulas, Aggressive diuretic therapy Third space shifting, burns, crush injuries Ascites

14. What kind of fluid are we losing? • Sweat – hypotonic (low sodium) • Insensible loss is pure water • GI loss is usually isotonic • Stomach – acid, high CL • Pancreas/bile – high HCO3 • Saliva – high K

15. IV fluids a la carte • NaCl • Normal saline (0.9%) has 154 mEq/L Na, 154 mEqCl • ½ Normal has 77 mEq Na/Cl • Lactated Ringers • Has 130 Na, 109 Cl (also has some K, Ca, lactate) • D5Water • Good replacement for insensible losses

16. 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

17. Case 1 Labs 200 12.3

18. Case 1 F & E Problem List • Hypovolemia • Hypochloremia • Hypokalemia • Alkalosis

19. Treatment – Patient weight is 12 kg • Fluid choice? • Replace volume • Replace K/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

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

21. Paradoxical Aciduria Hypochloremic Hypovolemia Aldosterone activation H Na Na K Loop of Henle

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

23. Case 2 • 64 year old, 50 kg, 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

24. Case 2 Labs Mg 1.1 180 16.3

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

26. Case 2 • Why does patient have hypervolemia?

27. 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)

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

29. Patient was receiving maintenance fluids D5 0.45NS at 125 ml/hr

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) + (28/1.8) = 335 • 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 • Hemolyzed specimen • Underlying disease • Renal failure • Rhabdomyolysis • Associated medications • Too much K+, ACE inhibitors, beta-blockers, antibiotics, chemotherapy, NSAIDS, spironolactone

41. 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)

42. 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 • Severe: dialysis

43. Pimping Questions on Rounds! • Signs of hypo Ca? • MCC of Hyper Ca? • Signs of hyper Mg • Signs of hypo Phos? • Compl of correcting Na too rapidly? • Chvostek, Trousseau, prolonged QT • PTH/metastatic Ca • Loss of DTR • Difficulty weaning off vent • Central Pontine Myelinolysis