Fluids

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Fluids Electrolytes and Nutrition

• Srinivas H Reddy, MD
• Trauma Surgical Critical Care
• Jacobi Medical Center

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Fluids Electrolytes
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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
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Goals

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

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Na-K ATPase
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Na/K ATPase

• Actively pumps 3 Na out of cell and 2K inside
  cell
• Energy from ATP
• Regulated by
• Insulin
• Aldosterone

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Starlings Forces
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Cations and Anions in Body Fluids
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Serum Osmolality

• 2 x Na BUN/2.8 Gluc/18

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• Osmolality CONCENTRATION
• Tonicity ONCOTIC PRESSURE FORCE ON WATER

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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

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Renin-Angiotensin-Aldosterone System
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Renin-Angiotensin-Aldosterone System
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Na-K ATPase
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GI Fluid Electrolyte Losses
Source Volume (ml) Na (mEq/L) Cl (mEq/L) K (mEq/L) HCO3 (mEq/L) H (mEq/L)
Stomach 1000-4200 20-120 130 10-15 30-100
Duodenum 100-2000 110 115 15 10
Ileum 1000-3000 80-150 60-100 10-15 30-50
Colon 500-1700 120 90 25 45
Bile 500-1000 140 100 5 25
Pancreas 500-1000 140 30 5 115
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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 Ringers frog hearts (London 1882)
• Alexis Hartman pediatric cholera, added
  bicarbonate (US 1930s)
• Lactate -gt Pyruvate -gt Bicarbonate
• Lactic Acidosis?
• Immunosuppressive effect on WBCs?
• Calcium precipitates with citrate in PRBC
  transfusion
• pH6.5

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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

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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

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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

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Fluid Status
SIADH Hypothyroid Cortisol
GI loss
CHF Cirrhosis
120
140
140
Na
NaHCO3 3 NaCl Seawater
GI loss Renal loss Osmotic
160
DI Insensible
high
low
normal
ECV
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Composition of IV Fluid Solutions

• Solution Na Cl- K Ca2 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 1/2NS20KCl 77 77 20 0 0 50g

Serum Osmolality 2 x Na BUN/2.8
glucose/18
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Replacement Fluid Strategies

• Sweat D5¼NS 5mEq KCl
• Gastric D5½NS 20mEq KCl
• Biliary/Pancreatic LR
• Small Bowel LR
• Colon LR
• 3rd space losses LR

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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 11 PRBCFFP (previously, and
  for other bleeds 31 ratio)

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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

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Indicators of Successful Resuscitation

• PULSE lt100 - 120 bpm
• URINE OUTPUT
• Child gt1.0 ml/kg/hr
• Adult gt0.5 ml/kg/hr
• Clearance of LACTATE
• Resolution of BASE DEFICIT
• BLOOD PRESSURE is a POOR INDICATOR!

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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)
• BUNCr ( gt201)
• Metabolic acidosis due to hypoperfusion

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Hypervolemia

• Large UO
• Pitting edema
• JVD
• Crackles on lung auscultation
• Hypoxia
• CXR cephalization of vessels, pulmonary edema

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Hyponatremia

• Serum Na lt 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 lt120-125mEq/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

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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

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Hypernatremia

• Serum Na gt 145
• Sx altered level of consciousness, seizure,
  coma, signs of dehydration
• Causes DI, hyperosmolar diuresis, EtOH
  (suppresses ADH)
• Tx calculate 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

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Hypokalemia

• K lt 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

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Hyperkalemia

• K gt 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

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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)

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Hypocalcemia

• Ca2 lt 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

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Hypercalcemia

• Ca2 gt 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

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Acid / Base
Respiratory Acidosis
Metabolic Alkalosis
BE 0 HCO3 24
Respiratory Alkalosis
Metabolic Acidosis
7.4
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Acid-Base Disturbances
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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

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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

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Relationship between PCO2 and Plasma pH
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Central Role of Carbonic Acid-Bicarbonate Buffer
System in Regulation of Plasma pH
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Central Role of Carbonic Acid-Bicarbonate Buffer
System in Regulation of Plasma pH
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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

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Severe Acidosis

• pH lt 7.2
• decreased responsiveness to catecholamines
• cardiac dysfunction
• arrhythmias
• increased potassium serum levels

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Nutrition
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Goals

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

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Why Nutrition?

• Growth
• Immunity
• Wound healing

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What Nutrition?

• Water
• Carbohydrate (Glucose) 60-70 of total kcal
• Protein 1.0-2.0 gm/kg/day
• Fat/Lipids 15-40 of total kcal
• Vitamins/Minerals/Elements

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How Much Nutrition?

• Water - You already know this part!
• Glucose _at_ 2-6 mg/kg/min
• Protein _at_ 1-2 g/kg/day
• Fat/Lipids _at_ 1-2 g/kg/day
• Vitamins/Minerals/Elements - A, D, E, K, B, C,
  Zinc, Chromium, Selenium, Phosphate, etc.

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How Much Nutrition?

• Harris-Benedict Equation for Basal Energy
• Expenditure (BEE) in kilocalories
• Male 66(13.8xW)(5xH)-(6.8xA)
• Female 655(9.6xW)(1.85xH)-(4.7xA)
• Range 20-40 kcal/kg/day
• Multiply by stress factor (1.2-2.0)
• i.e. burn, trauma, sepsis, increased activity
• Indirect Calorimetry estimate Resting
• Energy Expenditure and efficiency of fuel burning

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How Much Nutrition?

• Caloric Goal 25-30 kcal/kg/day
• Higher for burn patients (hypercatabolic)
• Glucose (2-6 mg/kg/min) _at_ 4 kcal/gm
• Protein (1-2 g/kg/day) _at_ 4 kcal/gm
• Fat/Lipids (1-2 g/kg/day) _at_ 9 kcal/gm
• Nutritional Status Parameters
• N2 Balance N2 in N2 out
• N2 in Protein intake (gm/day) / 6.25
• N2 out UUN 4
• Albumin / Transferrin / PreAlbumin / RBP
• Anthropometrics (TSF, MAC)

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Metabolic Stress

• Sepsis (infection)
• Trauma (including burns)
• Surgery
• Once the systemic response is activated, the
  physiologic and metabolic changes that follow are
  similar and may lead to septic shock

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Overfeeding

• Enough but not too much
• Excess calories
• Hyperglycemia
• Diuresis complicates fluid/electrolyte balance
• Hepatic steatosis (fatty liver)
• Excess CO2 production
• Exacerbate respiratory insufficiency
• Prolong weaning from mechanical ventilation

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How to Give Nutrition?

• Enteral - via the gut
• Preferred method
• Prevent intestinal atrophy
• Protect from bacterial translocation across
  basement membrane
• Gastric stress ulcer prevention
• Parenteral - via the vein
• Only for severely protein-malnourished patients
  who cannot be fed enterally in the long-term
• Higher risk of complications and infections,
  related to catheters and lipids (?)

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Tube Feeding

• Used when oral feeding cannot be tolerated
  (altered mental status, endotracheal intubation,
  facial trauma, dysphagia, etc)
• Nasogastric or orogastric tube is most common
  route
• Nasoduodenal or nasojejunal tube more appropriate
  for patients at risk for aspiration, reflux, or
  continuous vomiting

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Enteral Tube Feeding
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Alternate Routes for Enteral Tube Feeding

• Percutaneous Endoscopic Gastrostomy (PEG)
• Percutaneous Endoscopic Jejunostomy (PEJ)
• Open (surgical) Gastrostomy
• Feeding Jejunostomy
• Esophagostomy

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Tube-Feeding Formula

• Generally prescribed by the physician
• Important to regulate amount and rate of
  administration
• Diarrhea is most common complication
• Wide variety of commercial formulas available

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Parenteral Feeding Routes

• Peripheral Parenteral Nutrition (PPN) uses less
  concentrated solutions through small peripheral
  veins when feeding is necessary for a brief
  period (lt10 days)
• Total Parenteral Nutrition (TPN) used when
  energy and nutrient requirement is large or to
  supply full nutritional support for long periods
  of time through large central vein

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Questions?
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Thank You!