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Fluid and Electrolyte Management of the Surgical Patient

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Presentation on theme: "Fluid and Electrolyte Management of the Surgical Patient"— Presentation transcript:

1 Fluid and Electrolyte Management of the Surgical Patient
Basic Science 9/08/09 J. P. Stokes

2 Case Presentation #1 28 y/o WM involved in MVC brought to 1W with GCS of 3 and hypotensive. Pt intubated and receives 2L of LR which stabilize HR and BP. Found to have extensive cerebral contusion and SAH. Admitted to ICU with plan by Neurosurgery to correct any coagulopathy and keep sodium >150. Placed on 3% Hypertonic saline with Q6 Na. After 6 hours in the ICU, the patients UOP increases to cc/hr. The next sodium is % discontinued and patient started on Vasopressin replacement and free water. Pt deteroriates and herniates due to cerebral edema.

3 Case Presentation #2 55 y/o WF with low rectal cancer s/p neoadjuvant undergoes LAR with diverting ileostomy. Blood loss is 300cc, fluid for the case was 1.8L crytalloid, and the case lasted 3.5 hours. Post-operative the patient is hypotensive with minimal UOP. Patient receives several 1L boluses and BP and UOP improve. She continues to receive IVFs and her sodium on POD#3 is 128 and her sats are decreased. She is diuresed and improves. On POD #5, she is tolerating liquids and her ileostomy output is 2.8L for that 24 hour period. Her IVFs were discontinued due to her oral intake and the next morning her creatinine is 2.3. She is bolused, restarted on maintenance, and ileostomy replacement, along with anti-motility agents. Her creatinine improves and she is discharged on POD #7 with ileostomy output of 1L/day.

4 Overview Total Body Water (TBW) – 50-60% of total body weight depending on gender (amount of adipose tissue) TBW is divided into extracellular (1/3) and intracellular (2/3) compartments Extracellular is divided into plasma (1/4) and interstitial fluid (3/4) – 5% and 15% of body weight, respectively

5 Questions What is the amount in milliliters of the intracellular volume in a 70kg male? 14,000 ml 10,500 ml 42,000 ml 28,000 ml

6 Composition Extracellular – Sodium (+), Chloride (-) and Bicarbonate (-) Intracellular- Potassium, Magnesium (+), Phosphate and Proteins (-) Plasma – 154 mEq/L of cations/anions Maintained by ATP-driven sodium-potassium pumps

7 Osmotic pressure The movement of water across a cell membrane depends primarily upon osmosis. This depends on solutes or osmotically-active particles. Calculated serum osmolality = 2 X Sodium + glucose/18 + BUN/2.8 Normal mOsm Charge determines equivalents (1 mEq of sodium equals 1 mmol)

8 Questions What is the calculated serum osmolality of a patient with a the following chemistry? Na 140, K 4, Cl 105, HCO3 25, BUN 28, Cr 1.0, Glc 180 260 280 300 320 Bonus: What is the anion gap of this patient?

9 Fluid Homeostasis Average person
Intake - 2L of water per day (75% oral, 25% from solids Output – 1L of urine, 250ml of stool, 600ml of insensible loss (skin and lungs – pure water) Insensible losses increased by fever, hypermetabolism, and hyperventilation Sweating is an active process and is electrolytes and water Average salt intake – 3-5 grams

10 Fluid Balance System Volume down Volume UP
Generalized Weight loss Weight gain Dec. skin turgor Perp. Edema Cardiac Tachycardia Increased CO Orthostasis Increased CVP Hypotension Collasped veins Bulging veins Murmur (flow

11 GI secretions Type Volume Na K Cl HCO3–
Stomach – – – –130 0 Intestine 2000– – – – Colon  Pancreas 600– – – –90 95–115 Bile 300– – – –110 30–40

12 Question What fluid do you replace NGT output with? D51/2NS LR
1/2NS with 20 mEq KCL D5W with 150 mEq NaHCO3

13 Electrolyte Abnormalities
Sodium Hyponatremia Hypervolemic – Excess oral water intake, IV fluids Euvolemic – Hyperglycemia, SIADH, Hyperlipidemia (pseudo) Hypovolemic – Decreased sodium intake or increased loss of sodium containing fluids, GI losses, renal losses (UrNa >20) Hypernatremia Hypervolemic – Salt intake, Mineralcorticoid excess Euvolemic – Renal water loss (diuretics, DI), Nonrenal water loss (skin, GI) Hypovolemic – Adrenal failure, Osmotic diuretics Signs and Symptoms: CNS, MSK, GI, CV, etc.

14 Potassium Dietary intake 50-100 mEq/day; primarily intracellular
Hyperkalemia – Excess intake, increased release from cells, impaired excretion, medications Hypokalemia – Decreased intake, Excess excretion, GI losses (direct vs. indirect) S/S: GI, CNS, CV

15 Magnesium Hypomagnesemia – Poor intake, increased renal excretion, GI losses (diarrhea) Hypermagnesemia – impaired renal function, excess intake (TPN) Magnesium plays an important role in potassium and calcium homeostasis

16 Calcium/Phosphorus Hypercalcemia – Primary hyperparathyroidism, malignancy Hypocalcemia – Pancreatitis, renal failure, hypopara-, etc. Asymptomaic hypocalcemia can be due to hypoproteinemia, mainly albumin Correction for albumin Phosphorus – renal, gastrointestinal

17 Acid/Base Normal pH – 7.35-7.45 Metabolic vs. Respiratory
Uncompensated vs. Compensated pH, CO2, HCO3

18 Anion Gap and Metabolic Acidosis
Anion gap = (Na + K) – (Cl + HCO3) Normal: 12 +/- 4 Non-gap acidosis: Hyperalimentation, Acetozolamide, RTA, Diarrhea, Ureteral diversion, pancreatic fistulas Anion gap acidosis – Methanol, Uremia, DKA, Paraldehyde, INH, Lactate, Ethylene glycol, Salicylate

19 Metabolic Alkalosis Normal acid-base homeostasis prevents metabolic alkalosis from developing unless both an increase in HC03 generation and impaired renal excretion of HCO3 occurs. Generally associated with hypokalemia (pyloric stenosis) Etiology: Mineralocorticoid excess, loss from gastric secretions, exogenous, impaired exretion

20 Question What is the electrolyte and acid/base disturbance in pyloric stenosis, and explain why the patient has paradoxical aciduria?

21 Respiratory derangements
Hyperventilation Hypoventilation Involves minute ventilation (respiratory rate and tidal volume) Treatment directed at the cause

22 Fluid therapy What are the concentrations of normal saline and lactated ringer’s? Na 154 and 130 K 0 and 4 Cl 154 and 109 HCO3 0 and 28 Ca 0 and 3

23 Question What is the amount of dextrose per liter in D51/2NS? How many calories is in one liter? How many calories per hour if fluids 125 cc/hr? 5grams 50grams 500grams 500mg

24 Treating Electrolyte Disturbances
Hypernatremia – Correction of free water deficit Water deficit (L) =[(Na-140)/140] x TBW TBW at 50% in men and 40% in women The rate of fluid administered should be titrated to achieve a decrease in serum sodium of no more than 12 mEq/d. Rapid correction: cerebral edema, herniation Hyponatremia – Free water restriction, sodium administration Neurologic symptoms – 3% (No more than 1 mEq/L/hr); Complication: CPM

25 Potassium Correction Hyperkalemia: Reduce total body potassium, shift from extra- to intracellular, and protect cells from effects of increased potassium What can kill my patient? EKG, calcium How do I shift potassium? Bicarbonate, Glucose (Insulin), Albuterol How can I remove potassium? Lasix, Dialysis, Potassium binders (Kayexalate)


27 Repleting Electrolytes
Potassium: IV and PO/NG Magnesium: IV (Important for repleting other electrolytes) Calcium: IV and PO Phosphorus: IV and PO (ineffective)

28 Treatment of …. Hypermagnesemia: Remove source, calcium for cardiovascular effects, dialysis Hypercalcemia: Volume and diuresis, bisphosphonates, calcitonin Hyperphosphotemia: Phosphate binders, urinary exrection, dialysis

29 Maintenance fluids/Post-op
4, 2, 1 rule (Dextrose, Electrolytes) 5, 2, 1 rule in pediatric surgery Boluses What fluid? Post-Op

30 Question What is the appropriate fluid and maintenance rate for a 4kg baby with pyloric stenosis? What would you use to bolus the baby and why?

31 Special Situations SIADH – Euvolemia and hyponatremia along with elevated urine sodium and urine osmolality; Tx: Free water restriction, diuresis, fluids (?), lithium, democycline DI – Dilute Urine in the face of hypernatremia; Central and Nephrogenic; Tx: Free water, Vasopressin Refeeding: Shift from fat to carbohydrate stimulates insulin release and uptake of electrolytes (PO4, Mg, K, Ca), hyperglycemia

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