Fluids, Electrolytes, Acid-base

4 Starling Forces (push/ pull forces)

PUSH

1. capillary hydrostatic pressure - pushes fluid out

2. interstitial hydrostatic pressure- pushes fluid back

PULLS

1. capillary oncotic pressure - pulls fluid in (plasma proteins)

2. interstitial hydrostatic pressure- pulls fluid out (interstitial proteins)

examples of incr capillary hydrostatic pressure

heart failure, DVT, sepsis

left sided HF symptom

pulmonary edema

right sided HD symptom

peripheral pitting edema, ascites

DVT symptom

localized edema

liver failure, cirrhosis, nephrotic syndrome, and malnutrition all have

decr plasma oncotic pressure

liver failure/ cirrhosis symptom

ascites, peripheral PITTING edema

nephrotic syndrome symptom

massive proteinuria —> generalized edema (anasarca)

malnutrition symptom

kwashiorkor-type edema (periorbital, dependent)

incr capillary permeability caused by

acute inflammation (pancreatitis, cellulitis)

burns

surgical node removal can cause

NONPITTING lymphedema

sodium/ water r/t edema

incr Na/ water retention —> edema

ex) decr EABV —> RAAS —> eedema

RAAS system (Renin-Angiotensin-Aldosterone system)

Kidneys senses low perfusion → renin → angiotensin I & II → aldosterone 

Angiotensin II = VASOCONTRICTOR & helps raise the BP 

Aldosterone = RETAINS SODIUM & pulls Na into blood (water follows), dumps K 

Result: restores blood volume to vital organs

4 levers to raise BP

4 Levers to raise BP:

1. Vascular resistance – raising BP up or down

2. Heart rate 

3. Volume (give fluids or diuretics) – preload

4. Contractility (strength of the contract) – inotropes, LVAD, balloon pump 

ADH (antidiuretic hormone)

retains water

released when thirsty or low BP

aldosterone

retains sodium (therefore water)

ANP (atrial natriuretic peptide)

incr sodium excretion

sympathetic NS

vasoconstrict, incr Na

hypernatremia causes & symptoms

>145

diabetes insipidus, osmotic diuresis (hyperglycemia), excessive sweating

thirst, irritability, neuromuscular excitability, seizures

hyponatremia causes & symptoms

<135

hypovolemic

euvolemic

hypervolemic

nausea, headache, confusion, seizures

hypovolemic hyponatremia causes & symptoms

renal:

diuretics, nephropathy, adrenal insufficiency

symptom: vomiting, diarrhea, burns

euvolemic hyponatremia causes & symptoms

SIADH (symptom of inappropriate ADH aka too much ADH)

psychogenic polydipsia, beer potomania

hypervolemic hyponatremia causes

↓ EABV → ADH ↑ → water retention → hyponatremia (edema) 

CHF, cirrhosis, nephrotic syndrome

central diabetes insipidus vs. nephrogenic DI

central causes: pituitary surgery, trauma

treat: desmopression (DDAVP)

nephrogenic: kidneys don’t respond to ADH, DDAVP doesn’t work

causes: lithium toxicity, hypercalcemia

SIADH clinical signs/ causes

high urine specific gravity

hyponatremia

incr ADH

small-cell lung cancer, CNS disorders, psych meds

U-waves, flattened T waves, arrhythmias (PVCs, VT) are a sign of

hypokalemia

Peaked T waves, widened QRS, sine-wave pattern → Vfib/asystole are a sign of

hyperkalemia

hypokalemia causes

diuretics, vomiting, diarrhea

ALKALOSIS

hyperkalemia causes

K-sparing diuretics, renal failure, rhabdo, ACE-inhibs, ARBS

ACIDOSIS

normal ranges for Na, K, Ca, Mg

Na 135-145

K 3.5-5

Ca 8.5-10.5

Mg 1.7-2.2

Tetanty, Chvostek’s Trousseau’s signs, QT prolongation - signs of

hypocalcemia

Stones, bones, grains, psychiatric overtones; shortened QT, arrhythmias

hypercalcemia

Neuromuscular irritability, tetany, arrhythmias // Often w/ hypokalemia - sign of

hypomagnesemia

Muscle weakness, hypotension, bradycardia, prolonged PR/QT, coma- sign of

hypermagnesemia

hypoventilation, COPD, drug overdose, neuromuscular weakness can cause 

resp acidosis

hyperventilation (pain, anxiety, PE, high altitude) → lightheadedness, tingling can cause

resp alkalosis

high AG metabolic acidosis causes (MUDPILES)

• Methanol

• Uremia (renal failure) 

• DKA

• Propylene glycol, Paraldehyde 

• Infection, Iron, Isoniazid

• Lactic acidosis 

• Ethylene glycol

• Salicylates

normal AG metabolic acidosis causes, compensation

diarrhea, renal tubular acidosis (RTA), ureteral diversion

resp: blows off CO2

metabolic alkalosis causes

vomiting, NG suction

excessive alkali ingestion (antacids)

loop, thiazide diuretics

Conn’s synrom

ABG values

pH acidosis 7.35-7.45 alkalosis

CO2 alkalosis 35-45 acidosis

HCO3 acidosis 23-27 alkalosis