FLUIDS AND ELECTROLYTES FOR SURGEONS Anil S. Paramesh MD, FACS Associate Professor of Surgery, Urology and Pediatrics

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

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%

TOTAL BODY WATER 60% BODY WEIGHT ICF 2/3 (40% BW) Predominant solute K + ECF 1/3 (20% BW) Predominant solute Na + H2OH2OH2OH2O 75% interstitial 25% intravascular (5% of BW)

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 Skin600 ml Lungs400 ml Kidneys1500 ml Feces100 ml Balance can be dramatically impacted by illness and medical care

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

I L OVE S ALT W ATER !

(mEq/L)Plasma Intracellular Na K 4150 Ca Mg 2 7 Cl103 3 HCO Protein Gibbs-Donnan equation – product of diffusible an/cations same on both sides of SP membrane Electrolytes

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

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

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

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

Hypovolemia Acute Volume Depletion Determine etiology Hemorrhage, NG, fistulas, Aggressive diuretic therapy Third space shifting, burns, crush injuries Ascites

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

IV fluids a la carte NaCl Normal saline (0.9%) has 154 mEq/L Na, 154 mEq Cl 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

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

Case 1 Labs

Case 1 F & E Problem List  Hypovolemia  Hypochloremia  Hypokalemia  Alkalosis

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? rule

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

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

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

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

Case 2 Labs Mg 1.1

Case 2  Diagnoses?  New onset A fib, why?  Hypervolemia  Hyponatremia  Hypokalemia  Hypomagnesemia  Anemia

Case 2  Why does patient have hypervolemia?

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)

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

Patient was receiving maintenance fluids D NS at 125 ml/hr

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

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

Case 3 Labs Glucose 213 Mg 1.4

Current Problems Hypovolemia Increased plasma osmolarity 2 X (213/18) + (28/1.8) = 335 Hypernatremia Renal insufficiency Acidosis

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

Hypernatremia Relatively too little H 2 O 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

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

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

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

Case 4 Evaluate the patient Exam ECG Order repeat labs

Hyperkalemia - Common Causes Hemolyzed specimen Underlying disease Renal failure Rhabdomyolysis Associated medications Too much K +, ACE inhibitors, beta-blockers, antibiotics, chemotherapy, NSAIDS, spironolactone

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)

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

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