Basic fluids and electrolytes
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Basic Fluids and Electrolytes. Douglas P. Slakey. Why ? . Essential for surgeons (and all physicians) Based upon physiology Disturbances understood as pathophysiology To Encourage Thought Not Mechanical Reaction Most abnormalities are relatively simple, and many iatrogenic.

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Why ?

  • Essential for surgeons (and all physicians)

  • Based upon physiology

    • Disturbances understood as pathophysiology

      To Encourage Thought Not Mechanical Reaction

      Most abnormalities are relatively simple, and many iatrogenic


It's better to keep your mouth shut and let people THINK you're a fool than to open it and remove all doubt.

Mark Twain


It s all about balance
It’s All About Balance you're a fool than to open it and remove all doubt.

  • Gains and Losses

    • 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


Fluid compartments
Fluid Compartments you're a fool than to open it and remove all doubt.

  • 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 you're a fool than to open it and remove all doubt.

60% BODY WEIGHT

ECF

1/3

ICF

2/3

H2O

Predominant solute

K+

Predominant solute

Na+


I Love Salt Water! you're a fool than to open it and remove all doubt.


Electrolytes you're a fool than to open it and remove all doubt.

(mEq/L) Plasma Intracellular

Na 140 12

K 4 150

Ca 5 0.0000001

Mg 2 7

Cl 103 3

HCO3 24 10

Protein 16 40


Fluid movement
Fluid Movement you're a fool than to open it and remove all doubt.

  • 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
Movement of Water you're a fool than to open it and remove all doubt.

  • Osmotic activity

    • Most important factor

    • Determined by concentration of solutes

      Plasma (mOsm/L)

      2 X Na + Glc + BUN

      18 2.8


Third space
Third Space you're a fool than to open it and remove all doubt.

  • Abnormal shifts of fluid into tissues

  • Not readily exchangeable

  • Etiologies

    • Tissue trauma

    • Burns

    • Sepsis


Fluid status
Fluid Status you're a fool than to open it and remove all doubt.

  • Blood pressure

  • Check for orthostatic changes

  • Physical exam

  • Invasive monitoring

    • Arterial line

    • CVP

    • PA catheter

    • Foley


Remember jvd
Remember JVD? you're a fool than to open it and remove all doubt.


Dx of fluid imbalances
Dx of Fluid Imbalances you're a fool than to open it and remove all doubt.

  • Must assess organ function

    • Renal failure

    • Heart failure

    • Respiratory failure

  • Excessive GI fluid losses

  • Burns

  • Labs: electrolytes, osmolality, fractional excretion of Na, pH,


Disorders to be able to diagnose and treat
Disorders to be able to diagnose you're a fool than to open it and remove all doubt.AND Treat

  • Volume deficit

  • Volume excess

  • Hyper/hypo –natremia

  • Hyper/hypo –kalemia

  • Hyper/hypo -calcemia


Volume deficit
Volume Deficit you're a fool than to open it and remove all doubt.

  • 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


Dehydration you're a fool than to open it and remove all doubt.

Chronic Volume Depletion

Affects all fluid components

Solutes become concentrated

Increased osmolarity

Hct can increase 6-8 pts for 1 L deficit

Patients at risk:

Cannot respond to thirst stimuli

Diabetes insipidus

Treatment: typically low Na fluids


Hypovolemia acute volume depletion
Hypovolemia you're a fool than to open it and remove all doubt.Acute Volume Depletion

Isotonic fluid loss, from extracellular compartment

Determine etiology

Hemorrhage, NG, fistulas, aggressive diuretic therapy

Third space shifting, burns, crush injuries, ascites

Replace with blood/isotonic fluid

  • Appropriate monitoring

    • Physical Exam

    • Foley (u/o > 0.5 ml/kg/min)

    • Hemodynamic monitoring


Fluid replacement
Fluid Replacement you're a fool than to open it and remove all doubt.

  • Isotonic/physiologic

    • NS (154 meq, 9 grams NaCl/L)

    • LR (130 Na, 109 Cl, 28 lactate, 4 K, 3 Ca)

  • Less concentrated

    • 0.45NS, 0.2NS

    • Maintenance

  • Hypertonic Na


Fluid replacement1
Fluid Replacement you're a fool than to open it and remove all doubt.

  • Plasma Expanders

    • For special situations

    • Will increase oncotic pressure

    • If abnormal microvasculature, will extravasate into “third space”

      Then may take a long time to return to circulation


Fluid replacement2
Fluid Replacement you're a fool than to open it and remove all doubt.

  • Maintenance

    • 4,2,1 “rule”

  • Other losses (fistulas, NG, etc)

    • Can measure volume and composition!!!

    • Should be thoughtfully assessed and prescribed separately if pathologic

  • (i.e. gastric: H, Na, Cl)


Maintenance fluid
Maintenance Fluid you're a fool than to open it and remove all doubt.

  • Daily Na requirement: 1 to 2 mEq/kg/day

  • Daily K requirement: 0.5 to 1 mEq/kg/day

  • AHA Recommended Na intake: 4 to 6 grams per day

    To Replace Ongoing Losses, NOT Pre-existing Deficits


Maintenance Fluids you're a fool than to open it and remove all doubt.

D5 0.45NS + 20 mEq KCl/L at 125 ml/hr


How much sodium is enough
How much Sodium is Enough??? you're a fool than to open it and remove all doubt.

  • NS

    • 0.9% = 9 grams Na per liter

  • 0.45 NS = 4.5 grams per liter

  • 125 ml/hour = 3000 ml in 24 hours

  • 3 liters X 4.5 grams Na = 13.5 GRAMS Na!

    (If 0.2 NS: 3 liters X 2 grams Na = 6 grams Na)


Btw dr slakey the sodium is 120 hyponatremia
“BTW Dr Slakey, the sodium is 120 you're a fool than to open it and remove all doubt.”Hyponatremia

  • Na loss

    • True loss of Na

    • Dilutional (water excess)

    • Inadequate Na intake

  • Classified by extracellular volume

    • Hyovolemic (hyponatremia)

      • Diuretics, renal, NG, burns

    • Isotonic (hyponatremia)

      • Liver failure, heart failure, excessive hypotonic IVF

    • Hypervolemic (hyponatremia)

      • Glucocorticoid deficiency, hypothyroidism


Siadh
SIADH you're a fool than to open it and remove all doubt.

  • Causes

    • Surgical stress (physiologic)

    • Cancers (pancreas, oat cell)

    • CNS (trauma, stroke)

    • Pulmonary (tumors, asthma, COPD)

    • Medications

      • Anticonvulsants, antineoplastics, antipsychotics, sedatives (morphine)


Siadh1
SIADH you're a fool than to open it and remove all doubt.

Too much ADH

  • Affects renal tubule permeability

  • Increases water retention (ECF volume)

    Increased plasma volume, dilutional hyponatremia, decreases aldosterone

    Increased Na excretion (Ur Na >40mEq/L)

    Fluid shifts into cells

    Symptoms: thirst, dyspnea, vomiting, abdominal cramps, confusion, lethargy


Siadh treatment
SIADH Treatment you're a fool than to open it and remove all doubt.

  • Fluid restriction

    • Will not responded to fluid challenge!

      • i.e. a “Bolus” will not work

      • (distinguishes from pre-renal cause)

  • Possibly diuretics


Hypovolemia and metabolic abnormality
Hypovolemia and Metabolic Abnormality you're a fool than to open it and remove all doubt.

  • Acidosis

    • May result from decreased perfusion i.e decreased intravascular volume

  • Alkalosis

    • Complex physiologic response to more chronic volume depletion

    • i.e. vomiting, NG suction, pyloric stenosis, diuretics


Paradoxical aciduria
Paradoxical Aciduria you're a fool than to open it and remove all doubt.

Hypochloremic

Hypovolemia

Na

Na

H

Cl

K

Loop of Henle


Hypernatremia
Hypernatremia you're a fool than to open it and remove all doubt.

Relatively too little H2O

  • Free water loss (burns, fever)

  • Diabetes insipidus (head trauma, surgery, infections, neoplasm)

    • Dilute urine (Opposite of SIADH)

  • Nephrogenic DI

    • Kidney cannot respond to ADH


Hypernatremia1
Hypernatremia you're a fool than to open it and remove all doubt.

  • Hypovolemic

    • GI loss, osmotic diuresis

    • Increased Na load (usually iatrogenic)

Free water deficit:

[0.6 X wt (kg)] X [Serum Na/140 - 1]


Hypernatremia volume replacement
Hypernatremia Volume Replacement you're a fool than to open it and remove all doubt.

  • Example:

  • Na 153, 75 kg person

  • (0.6 X 75) X [(153/140) - 1]

  • 45 X [1.093 -1]

  • 45 X 0.093 = 4.2 Liters


Potassium and ph
Potassium and Ph you're a fool than to open it and remove all doubt.

  • 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
    Hyperkalemia you're a fool than to open it and remove all doubt.

    • Associated medications

      • Too much K+, ACE inhibitors, beta-blockers, antibiotics, chemotherapy, NSAIDS, spironolactone

    • Treatment

      • Mild: dietary restriction, assess medications

      • Moderate: Kayexalate

        • Do NOT use sorbitol enema in renal failure patients

      • Severe: dialysis


    Hyperkalemia1
    Hyperkalemia you're a fool than to open it and remove all doubt.

    • Emergency (> 6 mEq/l)

    • Treatment

      • Monitor ECG, VS

      • Calcium gluconate IV (arrhythmias)

      • Insulin and glucose IV

      • Kayexalate, Lasix + IVF, dialysis


    The End you're a fool than to open it and remove all doubt.

    Makani U’i


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