Fluids And Electrolytes

16 FLUIDS AND ELECTROLYTES

• What is the percentage of total body water by weight in an adult? What percent of total body water is intracellular?
• Body weight in Kg x 0 .6 = L of water
• 2/3rds is intracellular
• If 1/3rd of our total body water is extracellular, what percentage of that is intravascular?
• ¼ is intravascular
• ¾ is extravascular
• What is blood volume of 70 kg male?
• 5 L
• 7% by body weight
• In pediatric it is 80 cc/kg
• What are our common maintenance fluids?
• D5 ½ NS + 20 Meq of K
• D5 ¼ NS in babies
• Resuscitative fluids?
• Balanced crystalloid (LR or NS)
• Colloids
• Electrolyte concentrations of NS and LR in 1L
• NS = 154 mEq of Na and Cl
• LR = 130 mEq sodium, 4 mEq potassium, 2.7 mEq calcium, 109 mEq chloride and 28 mEq of HCO3
• Maintenance fluids
• 4, 2, 1 rule = hourly rate
• 4 cc/kg for first 10 kg, 2 cc/kg for second 10, every 1 cc for every kg over 20 kg

• Simplified version(for adults) = weight in kg + 40 = hourly rate of fluids

• How much sodium does a person need a day?
• 1-2 mEq/kg
• 70 kg person = 70-140 mEq/day
• How much potassium does a person need a day?
• 0.5 -1 mEq/kg
• 70 kg person = 35-70 mEq/day
• When to use D5 ½ NS?
• Patients that are NPO
• Protein sparing for fasting patients
• D5 = 5% per liter = 50 Grams
• 50 Grams x 3 .4 kcal = 170 kcals per liter of D5 saline solution
• What fluid do you give to someone that has been copiously vomiting?
• Resuscitative fluids (no D5), generally NS
• 1 L at a time to see if they respond
• ¼ of it stays intravascular
• How do colloids increase intravascular volume?
• Oncotic pressure in vessel that draws fluids intravascular
• Concern in sepsis/trauma/burns is with increased capillary permeability is colloid will leak out to interstitial space and draw fluid with it
• What colloids are available?
• Albumin
• Plasmanate
• Hetastarch, Hespand
• Side effects of coagulopathy
• Negatively effects platelet function

• Also can cause acute kidney injury

• What increases insensible losses?
• Burns
• Fevers
• Ventilators
• Open abdomen
• Large open wounds
• What fluid do you replace with?
• High NG tube output
• Normal Saline
• High volume bile leak (lose bicarb in bile)
• LR or D5 solution with bicarb
• Patient with diarrhea (lose K for colon)
• LR or NS with K
• Patient 2 days s/p open procedure now hyponatremic what are possibilities?
• Excess free water
• SIADH
• Pseudohyponatermia due to hyperglycemia or other high protein state
• How to differentiate
• Determine measured serum osmoles and calculated serum osmoles
• Serum osmolality is calculated by looking at chemistry
• Na, Glucose and BUN
• (2 x Na) + Glucose/18 + BUN/2 .8
• Simplified (Na x 2) + 10
• Compare to urine osmolality
• If it is SIADH your serum osmolality will be less than urine (very concentrated urine)

• If it is excess free water urine osmolality will be very low (trying to excrete excess water)

• If it is excess free water how do you treat?
• Fluid restriction
• If it is SIADH?
• Fluid restriction
• Give NS (don’t correct sodium too quickly, no more than 1 mEq/hour)
• Vaptans (vasopressin antagonist)
• Demeclocycline
• How to determine sodium deficit?
• Desired sodium - actual sodium x TBW = Sodium deficit in mEq
• Primary causes of hypernatremia?
• Iatrogenic
• Diabetes insipidus
• Pt with head injury and urine output increases to 700 cc/hr and now hypernatremic how to confirm its DI?
• Compare serum osmolality to urine osmolality
• Serum osmolality will be high and urine will be low in DI
• How to treat DI?
• Desmopressin (DDAVP)
• How to calculate free water deficit
• (Actual Na - Desired Na)/ Desired Na x TBW = Volume in liters
• What is hypophosphatemia associated with?
• Refeeding syndrome due to P04 shift extracellular to intracellular
• Can lead to failure to wean from ventilator
• How do you manage patient with hyperkalemia?
• Likely renal failure, could be medication induced

• EKG looking for peaked T waves

• Treatment
• Give calcium to stabilize myocardium
• NaHCO3
• Glucose with IV Insulin
• Lasix
• Kayexalate
• Albuterol
• Emergent Dialysis
• How to treat hypokalemia?
• Causes - Iatrogenic such as over diuresis
• 40 mEq of K should increase total K 0.4
• Hypocalcemia symptoms
• Weakness
• Perioral Tingling
• Chovstek’s sign - tap on facial nerve and get perioral twitching
• Trousseau’s sign - Carpal pedal spasm with blood pressure cuff
• Treatment of hypocalcemia?
• IV Calcium
• Vit D and Mg
• If hypocalcemia patient has low serum albumin, how do we correct serum calcium?
• Normal Albumin = 4
• Every point below 4 add 0 .8 to calcium level
• If Albumin = 2, add 1 .6 to serum calcium level
• What are main causes of hypercalcemia?
• MC cause of hypercalcemia in outpatient = hyperparathyroidism

• MC cause of hypercalcemia in an inpatient = malignancy

• Symptoms of hypercalcemia?
• Stones, bones, groans, and psychiatric overtones
• Kidney stones, bone pain, abdominal pain, and psychosis
• Treatment of hypercalcemia?
• Crystalloid resuscitation
• Loop diuretic second line
• Bisphosphonates are helpful for hypercalcemia due to cancer
• Calcitonin
• Glucocorticoids
• Dialysis
• Most important parts of ABG?
• pCO2, Bicarb, Base Excess/Base Deficit
• Normal values of ABG (to remember for exam)
• pCO2 = 40
• pH = 7 .4
• Bicarb = 24
• A change in pCO2 what change in pH would you expect?
• 0.8 x DCO2 = DpH for acute changes
• pH change by .1 for every 12 point change in CO2
• Dr . Matthew Martin Tips When Looking at ABG
• Looks at CO2 first
• If high writes resp acidosis . If low, writes resp alkalosis
• Then looks at bicarb
• If high, writes metabolic alkalosis . If low, writes metabolic acidosis

• Then he looks at pH and their history to put it all together

• Metabolic acidosis
• Start with calculating anion gap
• (Na + K) - (Cl + HCO3)
• Gap Acidosis = MUDPILES
• Non-Anion Gap = Ileal conduit, Fistulas, Hyperchloremic (Too much NaCL), Renal Tubular Acidosis, Diarrhea, Acetazolamide
• Metabolic alkalosis
• NG suction - Hyperchloremic, hypokalemic metabolic alkalosis
• Contraction alkalosis from over diuresis
• Give chloride back is most important Table 1: Common Electrolyte Abnormalities and Treatment

Acid Base Practice Problems

• Patient undergoes surgery and has 3L NG Suction, postop ABG shows 7 .55, pCO2= 52, HCO3 = 40
• What is his primary disorder?
• He is alkalotic with a metabolic alkalosis (HCO3 of 40)
• Respiratory acidosis is compensatory
• Primary metabolic alkalosis with respiratory compensation
• Patient who is admitted in a coma, pCO2 = 16, HCO3 = 5, pH = 7 .1
• Metabolic acidosis with a respiratory compensation
• Respiratory alkalosis is compensatory as overall disorder is acidotic
• Climber climbing a mountain, he is at 5000 meters, what is his going to happen to his pCO2 and his pH?
• pCO2 will go down and pH will go up
• Respiratory alkalosis
• Patient whose pH is 7 .5, PCO2 = 50, HCO3 is 35
• Primarily metabolic alkalosis with respiratory compensation Quick Hits
• Cation that determines serum osmolarity
• Na
• Primary intracellular cation
• K
• Sepsis resuscitation bolus amount cc/kg
• 30cc/kg
• Pediatric patient who needs bolus
• 20 cc/kg

• Blood products = 10 cc/kg

• Pt with K of 6 .5 and peaked T waves on EKG, what medication do you give first
• Calcium gluconate
• Pt on liver transplant list, who was started on a “water pill” by his PCP, now has K of 2 .5
• Lasix
• Pt on liver transplant list, who was started on a “water pill” by his PCP, now his K is 5 .5
• Spironolactone
• Pt came in hyponatremic getting 3% NS, and now they develop spastic quadriplegia
• Central pontine myelinolysis
• Pt is hyponatremic, they are on free water restriction, still hyponatremic
• Can give vaptans (acts on V2 receptor in the kidney) or demeclocycline
• Or hypertonic saline
• Baby with pyloric stenosis who has been having emesis for 1 week
• Hypochloremic, hypokalemic, metabolic acidosis
• Paradoxical aciduria
• Effect of acidosis on oxygen-hemoglobin disassociation curve
• Right shift - oxygen will unload easier
• Surgical patient gets hextend and is now bleeding in OR, what coagulation disorder do they have
• Platelet dysfunction
• Pt with marked metabolic alkalosis, now has decreased respiratory drive, what drug could you give
• Acetazolamide
• Pt with high NG output, or vomiting

• Hypochloremic, metabolic alkaloses

• Pt with diarrhea
• Hypokalemic metabolic acidosis
• Mountain climber
• Respiratory alkalosis
• POD 2 after whipple is now somnolent with pinpoint pupils
• Respiratory acidosis, due to overdose on narcotics
• Ileal conduit and high output
• Metabolic acidosis, non-gap

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