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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Basic fluids and electrolytes

Basic Fluids and Electrolytes

Douglas P. Slakey


Basic fluids and electrolytes

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


Basic fluids and electrolytes

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

  • Gains and Losses

    • 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


Fluid compartments

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%


Basic fluids and electrolytes

TOTAL BODY WATER

60% BODY WEIGHT

ECF

1/3

ICF

2/3

H2O

Predominant solute

K+

Predominant solute

Na+


Basic fluids and electrolytes

I Love Salt Water!


Basic fluids and electrolytes

Electrolytes

(mEq/L)Plasma Intracellular

Na14012

K4150

Ca50.0000001

Mg27

Cl1033

HCO32410

Protein1640


Fluid movement

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

Movement of Water

  • 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

  • Abnormal shifts of fluid into tissues

  • Not readily exchangeable

  • Etiologies

    • Tissue trauma

    • Burns

    • Sepsis


Fluid status

Fluid Status

  • Blood pressure

  • Check for orthostatic changes

  • Physical exam

  • Invasive monitoring

    • Arterial line

    • CVP

    • PA catheter

    • Foley


Remember jvd

Remember JVD?


Dx of fluid imbalances

Dx of Fluid Imbalances

  • 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 diagnoseAND Treat

  • Volume deficit

  • Volume excess

  • Hyper/hypo –natremia

  • Hyper/hypo –kalemia

  • Hyper/hypo -calcemia


Volume deficit

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


Basic fluids and electrolytes

Dehydration

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

HypovolemiaAcute 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

  • 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

  • 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

  • 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

  • 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


Basic fluids and electrolytes

Maintenance Fluids

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


How much sodium is enough

How much Sodium is Enough???

  • 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”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

  • Causes

    • Surgical stress (physiologic)

    • Cancers (pancreas, oat cell)

    • CNS (trauma, stroke)

    • Pulmonary (tumors, asthma, COPD)

    • Medications

      • Anticonvulsants, antineoplastics, antipsychotics, sedatives (morphine)


Siadh1

SIADH

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

  • 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

  • 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

Hypochloremic

Hypovolemia

Na

Na

H

Cl

K

Loop of Henle


Hypernatremia

Hypernatremia

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

  • 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

  • Example:

  • Na 153, 75 kg person

  • (0.6 X 75) X [(153/140) - 1]

  • 45X [1.093 -1]

  • 45 X 0.093 = 4.2 Liters


Potassium and ph

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

    Hyperkalemia

    • 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

    • Emergency (> 6 mEq/l)

    • Treatment

      • Monitor ECG, VS

      • Calcium gluconate IV (arrhythmias)

      • Insulin and glucose IV

      • Kayexalate, Lasix + IVF, dialysis


    Basic fluids and electrolytes

    The End

    Makani U’i


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