Electrolytes lecture Flashcards
increase in total body fluid/Na
*increased weight; edema, ascites
ie HF
volume overload
wt loss, excessive thirst, postural hypotension and dry mucous membranes;
BOTH** water and salt are loss
ie..vomiting, diarrhea
volume depletion
refers to volume depletion with DISPROPORTIONATE WATER DEFICIT; may lead to increased Na, osmolality
dehydration
diarrhea; other heat related illnesses, fevers, vomiting
most common causes of dehydration
breakdown product of muscle energy metabolism; lower in women than men, reflects lean muscle mass. Good indicator of glomerular filtration.
Creatinine
0.6-1.2 mg/dL
end product of protein metabolism; excreted by kidney
blood urea nitrogen (BUN)
8-20 mg/dL
weakness, delerium, seizures
HYPOnatremia
arrhythmias, muscle weakness, cramps
HYPOkalemia
weakness, diarrhea
HYPERkalemia
cramps, arrhythmias, seizures
HYPOcalcemia
polyuria, constipation, lethargy/confusion
HYPERcalcemia
what is essential in patients with neuromuscular symptoms?
measurement of electrolytes
glucose, BUN, Cr, electrolytes (Na, K, Cl, HCO3), Ca, Mg, O2 sat
assessment of metabolic and renal status
Na under 130 meq/L
HYPOnatremia
most cases of HYPOnatremia result from ____ imbalance
water imbalance
NOT Na imbalance**
increased ADH secretion can lead to…
water reabsorption, and ultimately HYPO Na
very small increases in plasma osmolality (1-2%) result in…
ADH secretion
large changes in volume (5-10%), with concomitant decrease in BP, results in…
ADH release
- mediated through baroreceptors in the circulation
- free H20 is retained, leading to HypoNa
decreased Na with decreased extracellular volume can be caused by either….
*total body Na/H2O decreased
RENAL (diuretics) or EXTRARENAL (vomiting, diarrhea, volume loss)
ADH secretion is increased to maintain….
intravascular volume
*this drive OVERRIDES the need to sustain normal osmolality. pt often initially unable to take in adequate Na/H2O orally
Pt has..... decreased volume total Na/H2O decreased serum osmolal decreased ADH secretion increased renal status preserved HYPOnatremia HYPOkalemia
Rx?
isotonic fluids IV (normal saline/0.9% saline or ringers lactate) with KCL
If there is a mild volume decrease and oral intake intact…suggest what?
electrolyte drink (Gatorade) plus KCL
Hyponatremia with increased ECF seen in what kind of disorders?
Edema related*
ie…HF**, cirrhosis, nephrotic syndrome)
total body Na/H20 increased but CIRCULATING BLOOD VOLUME IS SENSED AS INADEQUATE BY BARORECEPTORS because of decreased CO and BP
Hypervolemic hypotonic HypoNa
decreased cardiac output leads to decreased renal perfusion, which causes….
INCREASED ADH + activation of RAA system
Tx of hypervolemic HypoNa (i.e. HF, cirrhosis, nephortic syndrome)
Water restriction*
diuretics
tx underlying condition
euvolemic normal or mildly decreased Na serum osmolality decreased increased ADH secretion normal renal status hyponatremia increased urine osmolality
Euvolemic hypoNa
*SIADH is the most common cause
Syndrome of inappropriate antidiuretic diuretic hormone secretion (SIADH) is the most common cause of…
euvolemic HypoNa
disorders of CNS (stroke), tumors (lung ca, others), pulmonary lesions (TB, lung abscess), drugs with ADH-like effects (SSRIs), post op pain, etc
can all lead to…
Euvolemic HypoNa
Hyponatremia, decreased serum osmolality with inappropriate high urine osmolality is seen with…
Euvolemic HypoNa
- Absence of cardiac, liver, renal, adrenal or thyroid disease.
- Urine Na greater than 20meq/L. Natriuresis (RAAS turned off) compensates for slight increase in volume from ADH.
- Serum BUN and uric acid are low due to increased clearance (mild volume expansion).
SIADH
symptomatic HypoNa (Na under 120) is a….
medical emergency!!!
correction of hyponatremia must be done…
SLOWLY!! (less than 10-12 me/L/ day)
Osmotic demyelination of brainstem can occur if…
HypoNa correction occurs too quickly
Marked excess free H2O intake, greater than 10 L/d or more.
*Seen in patients with psychiatric disease who may be on psychiatric meds (SSRI’s, others) that can interfere with H2O excretion.
psychogenic polydipsia
Euvolemia maintained via renal excretion of H2O and Na (urine Na more than 20 meq/L).
- Serum ADH levels are low.
- Urine osmolality is low.
Psychogenic polydipsia
post-op pain does what to ADH?
increased ADH secretion!
If post-op pt in pain receives hypotonic fluids, can cause….
severe HypoNa
seizures
HA
Treatment: Appropriate pain control with administration of isotonic fluids until patient able to take adequate fluids orally.
Post-op HypoNa
Seen with significant hyperglycemia in diabetics, especially if insulin dependent, with an acute rise in BS →↑osmolality. Water is drawn from cells into extracellular space
Hypertonic HypoNa
Na falls 2-4 meq/l for every 100mg/dL rise in glucose above 200mg/dL; resolves with insulin infusion and volume expansion.
Hypertonic HypoNa
20% of ambulatory and 50% of hospitalized patients with _____ have HypoNa
AIDS (HIV)
Pathophysiology: multiple mechanisms involved, often a combination of GI fluid and electrolyte loss along with inappropriate ADH secretion associated with CNS and/or pulmonary involvement from ____ infection.
HIV
Unusual with intact thirst mechanism and access to H2O. “Stranded in the desert/lost at sea.”
*Appropriate H2O intake not possible (no H2O available or unconscious).
Signs/Sx: Orthostatic hypotension, dehydration; oliguria.
HyperNa with concentrated urine
urine osmolality greater than 400 with intact renal function
*ADH levels increased
HyperNa with concentrated urine
Correct cause of fluid loss and replace volume, water and electrolytes as indicated.
Replace water deficit slowly to avoid cerebral edema (brain cell adaptation to serum hyperosmolality). Fluid deficit should be replaced over 48-72 hours.
tx of HyperNa
CHF, nephrotic syndrome, renal failure, hepatic cirrhosis…all cause?
Hyponatremia with HYPERvolemia
SIADH, hypothyroidism, glucocorticoid excess..all cause?
Hyponatremia with EUvolemia
Renal and nonrenal sodium loss..all cause?
Hyponatremia with HYPOvolemia
lethargy, disorientation, muscle cramps, anorexia, hiccups, nausea, vomiting, seizures
*weakness, agitation, hyporeflexia, orthostatic hypotension, Cheyne-Stokes respirations, delirium, coma, stupor
HYPOnatremia
*Diabetes Insipidus: ↑↑thirst, ↑↑H2O (polydipsia)
Urine osmolality
Hypernatremia with dilute urine
Major intracellular ion
K
K uptake by cells stimulated by _____ in the presence of glucose and facilitated by beta adrenergic stimulation.
insulin
RAA system is a major excretion of….
K+
RAA system AKA Renal K modulation
Symptoms/signs: weakness, muscle cramps, fatigue, constipation.
ECG: NSST-T* changes and “U” waves; PVC’s
HYPOkalemia
Aldosterone facilitates urinary K excretion; most important regulator of body K content. Most diuretics lead to renal K losses.
Renal losses of K+ (leading to HYPOkalemia)
Treatment for mild to moderate K losses
oral KCL
Severe hypokalemia treatment
SLOW** IV fluids/KCL
cardiac monitoring
Patients with renal insufficiency are at risk for which potassium disorder?
HYPERkalemia
Mild hyperkalemia may accompany which acid-base disorder?
Metabolic acidosis
- Severe renal insufficiency
- Renal insufficiency plus K supplements (KCL), K sparing diuretic or ACEI
- Combination of KCL + K sparing diuretic as Rx of hypokalemia: avoid for most patients
Risk factors for HYPERkalemia
Abnormalities in neuromuscular function: weakness, diarrhea, rarely paralysis.
**Characteristic ECG findings may occur: Peaked T waves, widening of QRS, increased intervals, loss of P waves, etc.
HYPERkalemia
50% of this electrolyte is ionized and used for muscle and nerve function
Calcium
Important to measure serum ____ to determine if Ca levels reflect true deficiency.
albumin
Is ionized calcium effected by albumin levels?
NO!
For every 1 gram ↓of albumin, total Ca ↓s by ___ meq/L
0.8
Most common cause of HYPOcalcemia
renal failure
Signs/Sx: Increased excitation of nerve and muscle cells; cramps, tetany, paresthesias and convulsions.
Chvostek’s sign, Trousseau’s sign
* ECG: Prolonged Q-T interval/arrhythmias
HYPOcalcemia
If symptomatic: IV calcium gluconate via bolus and infusion.
If asymptomatic: Oral calcium and Vitamin D.
Tx for HYPOcalcemia
Etiologies include hyperparathyroidism, malignancy (tumors produce PTH related proteins), milk-alkali syndrome (Ca antacids + Vit D excess).
HYPERcalcemia
Signs/Sx: Often without sx if mild ↑Ca Renal/GI: polyuria (H2O* reabsorption is blocked by hypercalciuria), nephrolithiasis; nausea, constipation. Neuro changes (drowsiness, weakness, lethargy, stupor/coma) if severe
HYPERcalcemia
ECG findings: Shortened Q-T, PVC’s.
Lab: increased Ca with nl. or low PO4.
HYPERcalcemia
Treat underlying disease process.
Promote Na rich diuresis which will be accompanied by excretion of Ca.
Infusion of 0.9% Saline + IV furosemide will expand ECF volume and promote Na/Calcium rich diuresis.
**Avoid Thiazide diuretics: Can worsen
HYPERcalcemia
Symptoms similar to hypocalcemia: weakness, muscle cramps, tremors, neurmuscular and CNS hyperirritability.
Often associated with hyopK and hypoCa
*can cause dangerous (ventricular) cardiac arrhythmias, esp if K is low.
HYPOmagnesemia
Very common in hospitalized patients, especially those on diuretics who are receiving continuous IV fluid support.
HYPOmagnesemia
