Fluids and Electrolytes Flashcards
we are ___% water
60%
What portion is intracellular and what portion is extracellular?
2/3 intracellular
1/3 extracellular
what portion of ECF is plasma and what portion is interstitial?
80% interstitial
20% plasma
what do you need to consider when managing a patients fluid status?
NPO Deficit
Maintenance
Evaporative Losses and “Third Spacing”
Blood loss
what are the two main patient types that you would not want to fluid overload?
- renal patient who is dialysis-dependent, because their kidneys do not filter the excess fluid.
- patients with CHF with fluids, because the more preload their hearts have, the less they can respond by increasing contractility and they can end up in cardiogenic pulmonary edema.
4/2/1 Rule
4 mL/kg/hr for 1st 10kg
2 mL/kg/hr for 2nd 10kg
1 mL/kg/hr for remaining kg
what is the additional fluid requirement for minimal, moderate and severe tissue trauma?
minimal: 2-4mL/kg/hr
moderate: 4-6mL/kg/hr
severe: 6-8mL/kg/hr
describe “third spacing”
This refers to an internal redistribution of fluids, especially during large thoracic or abdominal procedures. Intravascular fluid volume is depleted as inflamed tissue sequesters much fluid in the interstitial space. Replacement of this fluid is necessary to avoid organ hypoperfusion, especially in renal insufficiency.
what are the advantages and disadvantages of crystalloids?
Advantages: safe, nontoxic, reaction free, and cheap.
Disadvantages: limited time in IV space, edema with large volumes.
Solutions of inorganic and small organic molecules dissolved in water. The main solute is saline or glucose and the solution may be iso, hypo, or hypertonic.
crystalloid
in terms of acid-base balance, what can NS and LR cause?
Saline solution –> Hyperchloremic metabolic acidosis
Lactated Ringer’s–> Metabolic alkalosis (lactate–> HCO3)
what ion in which crystalloid limits its use when transfusing blood products?
Calcium in LR
Why is NS used in neuro cases?
pulls fluid out of the tissue, making a clearer visual field for the surgeon
Homogeneous noncrystalline substance consisting of large molecules dissolved in a solute. Most are dissolved in normal saline, but glucose, hypertonic saline, and LR have been used as well
Colloid
advantages of colloids
Greater capacity to remain in the IV space (longer half life), more efficient for replacing a severe fluid deficit quickly, smaller infused volume.
disadvantages of colloids
greater expense, coagulopathy, hypersensitivity reactions
what is the difference between hextend and hespand?
Hextend = hetastarch in LR Hespan = hetastarch in NS
Albumin is purified from _________
human plasma
______ can lead to a reduction in factor VIII and vWf, impairs plt function, and can prolong PTT.
hetastarch
how does dextran 40 improve microcirculation blood flow?
by decreasing blood viscosity and is often used by vascular and plastic surgeons to maintain patency of anastamoses.
_________ decreases platelet aggregation and adhesiveness.
dextran (mostly 70)
what portion of colloids is distributed intracellularly and extracellularly?
100% extracellular
100% intravascular
what is a mEq?
A milliequivalent is defined as 1/1000 of an equivalent of a chemical element, radical or compound. Its abbreviation is “mEq.” The equation used to calculate a milliequivalent is atomic weight (g) / (valence x 1000). The unit of measure for mEq is grams (g).
what are some normal hematology lab values?
White Blood Cell Count (WBC)(cells/ml): 4,500-10,000
Red Blood Cell Count (RBC)(x 10 6): 4.0-5.5
Hemoglobin (Hgb)(g/dl): 12.0-16.5
Hematocrit (Hct)(%): 36-50
Mean Corpuscular Volume (MCV): 80-100
Platelet Count (plt): 100,000-450,000
what are some normal plasma values for electrolytes?
Sodium (Na+)( mEq/L): 135-145 Potassium (K+)(mEq/L): 3.5-5.0 Chloride (Cl-)(mEq/L): 100-106 Calcium (Ca++)(mEq/L): 8.5-10 Bicarbonate (HCO3-) (mEq/L) 22-26 Magnesium (Mg++)(mEq/L): 1.5-2.5 Phosphate (PO4---)(mEq/L): 0.5-1.5 Sulfate (SO4--)(mEq/L): 0.3-0.6
what are some normal values for coagulation studies?
Protime (PT)(Extrinsic pathway): 10-14 seconds
Partial Prothrombin Time (PTT)(Intrinsic pathway): 25-39 sec
International Normalized Ratio (INR): 0.8-1.2
INR= PT test/PT normal
_______ is the key regulator of water balance in the body
Sodium
_______ is the most abundant cation of the ECF and is critical in determining EC and IC osmolarity.
Sodium
_______ is the most abundant anion of the ECF
chloride
______ is the most abundant intracellular cation
potassium
______ is the most abundant intracellular anion
phosphate
what are two causes of hyponatremia?
- True loss of sodium: from excess sweating, vomiting, diarrhea, burns, and the administration of diuretics.
- Dilutional Hyponatremia: Due to an excess of TBW.
what is the most common cause of hyponatremia?
dilutional hyponatremia from excess TBW= excess ADH release (stress, SNS activation, SIADH),TURP syndrome.
what are the neurological signs and symptoms of hyponatremia?
N&V, visual disturbances, depressed consciousness, agitation, confusion, coma, seizures, muscle cramps, weakness, myoclonus.
what effect (if any) does hyponatremia have on MAC?
decreases it
Hypervolemic hyponatremia can cause _____,______, & _______
pulmonary edema, HTN, and heart failure
at what concentrations do you see symptoms with hyponatremia?
< 123 mEq/L = cerebral edema
< 100 mEq/L = cardiac symptoms
a typical surgical suction container holds what volume?
3 L
what is the half life of a crystalloid?
30-60 mins
what is the half life of a colloid?
albumin: 3-4Hrs
Dextran: 6-12Hrs
Hetastarch lasts the longest (up to 17 days)
what is TURP syndrome?
too much fluid for scope –> hyponatremia & neuro damage
how can hyponatremia be treated?
Water restriction or loop diuretic in the case of water overload (TURP syndrome).
Hypertonic saline in the case of severe hyponatremia with neurologic symptoms.
Correct Na deficits very SLOWLY!
Why do we correct [Na] slowly?
Central pontine myelinolysis is a concentrated, frequently symmetric, noninflammatory demyelination within the central basis pontis
“…cellular edema, which is caused by fluctuating osmotic forces, results in compression of fiber tracts and induces demyelination. Prolonged hyponatremia followed by rapid sodium correction results in edema..”
difficulty speaking due to neurologic damage of the neurons that control muscles of speech
dysarthria
lack of muscle coordination
ataxia
An increase in ECF [Na] (above 145 mEq/L) which may be accompanied by the presence of low, normal, or high total-body Na content.
hypernatremia
signs and symptoms of hypernatremia
Intense thirst (unless malfunctioning thirst mechanism) Lethargy, mental status changes --> coma and convulsions. Shock, peripheral edema, myoclonus, ascites, muscle tremor, hyperactive reflexes, pleural effusion, expanded intravascular fluid volume
how can hypernatremia be treated?
Treatment: diuretics and hypotonic crystalloids to restore normal osmolality and volume.
Slow correction
what effect (if any) does hypernatremia have on MAC?
increases MAC
4 factors that have a short term influence on K+ concentration?
1) insulin- causes more Na to enter the cell through Na+/H+ transporter. To maintain electroneutrality as H leaves, Potassium must be pumped into the cell.
2) pH
3) B2-adrenergic agonists, and HCO3 administration.
4) Hyperventilation can also decrease K (indirectly due to pH changes)
2 factors that have a long term effect on K+ concentration
kidney and aldosterone
how are acidemia and potassium concentration related?
In acidemia, the body will use potassium to decrease H ions by moving K out and H in. Therefore, acidemia potentiates hyperkalemia.
signs and symptoms of hypokalemia
in the range of 2-2.5 mEq/L, hypokalemia can cause muscle weakness, arrythmias, and ECG changes
. If potassium is below _____, treat with IV KCl.
2.6
how must KCl be administered?
KCl must be diluted in NS (250 mL) and should not be infused faster than 10 mEq/hr in a peripheral IV, and 20 mEq/hr through a CVL. Monitor the EKG continuously.
signs and symptoms of hyperkalemia
muscle weakness, 6-7 mEq/L-peaked T waves and long PR. Wide QRS, VF and asystole as approach 10-12 mEq/L
how is hyperkalemia treated?
determined by presence of ECG changes. Stabilize heart with IV calcium. Redistribute potassium into cells by IV glucose and insulin, (amp D50 + 10 U Insulin- lowers levels within 10 min and lasts 4-6 hrs), Bicarb, hyperventilation
Dialysis, diuretics, B agonists, aldosterone agonists, kayexelate
what is the relationship between aldosterone and K+?
Aldosterone increases Na+ reabsorption causing K+ to be excreted
in the evolution of the EKG, which electrolyte disturbance creates a “U” wave after the T wave?
hypokalemia
how does hyperkalemia affect the EKG?
peak T waves –> Wide QRS –> sine wave –> V fib
what controls Calcium balance?
PTH and Calcitonin
what are the three different forms of Calcium in the body?
Bound to protein (40%)
Ionized, physiologically active (50%)
Nonionized chelated with anions: Phosphate, Sulfate, Citrate (10%)
low serum albumin has what effect on Calcium?
Low serum albumin affects only the level of total calcium, not ionized. Calcium levels must be adjusted for low albumin. If Albumin is low, then the adjusted calcium value is higher than the measured serum calcium value
_____ calcium is what determines the biological effect
Ionized calcium
what effect do PTH and calcitonin have on Ca+ balance?
PTH causes increased calcium reabsorption in the kidney and decreased excretion. It also causes bone resorption, therefore increasing calcium.
Calcitonin is produced in the thyroid gland, increases excretion of calcium in the kidneys acutely, but has little effect on chronic calcium homeostasis. (“tones” it down)
during what procedure is it common to have to measure the Calcium every 30 mins
During a parathyroidectomy, often times you will need to measure the serum calcium level every 30 minutes or so as an indication of removal of the parathyroid glands. Once PTH stops being released with removal of the gland, the Calcium level will substantially drop.
symptoms of hypocalcemia
mental status changes, tetany, laryngospasm, hypotension, dysrrhythmias. Chvostek’s sign, Trousseau’s sign. Tetany is due to hyperexcitable neurons caused by hypocalcemia.
how is hypocalcemia treated?
calcium chloride or calcium gluconate
SLOWLY
causes of hypercalcemia
Due to hyperparathyroidism most often, or an excess of Vitamin D, Renal failure, and paraneoplastic disorders (secondary to cancer).
symptoms of hypercalcemia
Symptoms: Abdominal pain or discomfort Bone pain and fractures Decreased appetite Difficulty concentrating, Excessive thirst & urination, Fatigue, Low back pain, Malaise or lethargy Muscle twitching or weakness Nausea and vomiting Depression
treatments for hypercalcemia
parathyroidectomy, diuretics, fluid replacement, dialysis, calcitonin type medications
what are the metabolic functions of magnesium?
Inhibits ACH release
Activates 300 enzyme systems, including many involved in energy metabolism.
Essential for production/function of ATP.
Essential for DNA, RNA, and protein synthesis.
Regulates calcium access into the cell and the actions of calcium in the cell.
Natural physiological calcium antagonist
which patients are commonly on a Mg regimen?
preeclamptic (acts as an anticonvulsant due to cerebral vasodilation)
Mg is a cofactor of ___ uptake and is often used to treat what electrolyte imbalance?
Potassium
many times hypokalemia can not be fully corrected by administration of K + alone . Magnesium is required for adequate processing of K+, and if the patient’s magnesium is low, they will have refractory hypokalemia. Magnesium is a cofactor for potassium uptake.
Magnesium is 18 times more concentrated in the ______ than in the plasma and acts as an anticoagulant and vessel dilator, which helps keep the _________ patent.
heart
coronary arteries
how is Mg eliminated and why is that important?
IV Mag has 100% renal elimination. Magnesium also potentiates the NMB, as well as anesthetics, opioids, and hypnotics. AVOID in patients with heart block!!
who is susceptible to hypomagnesemia?
Critical care patients, athletes, high metabolic states (pregnancy), diuretics/prolonged diarrhea, chronic alcoholics.
signs and symptoms of hypomagnesemia
CNS irritability: seizures, hyperreflexia, muscle spasm, signs are similar to hypocalcemia.
what are the symptoms of hypermagnesemia and how is it treated?
S&S: Decreased DTR’s, sedation, hypoventilation, bradycardia, hypotension, muscle weakness. EKG changes.
Treatment: Diuretics, fluid loading, dialysis
how does Mg affect the EKG?
Hypomagnesemia is a cause of a polymorphic Vtach- Torsades de Pointes. It starts with a long QT interval.
Hypermagnesemia causes wide QRS, long P-R interval, hypotension, myocardial depression.
how do you know what is normal/when to treat the PaO2 after a blood gas?
alveolar O2 equation or you can just estimate using paO2/fio2, which should be >400 mmHg. Hypoxemia is indicated by a ratio less than 300.
what is base excess and what does it tell you?
Base Excess refers to the amount of proton needed to bring the blood pH back to 7.4. It is an indicator of the metabolic component of pH in the blood.
what is the difference between CO2 and base excess?
While carbon dioxide defines the respiratory component of acid-base balance, base excess defines the metabolic component.
what are the pH and PaCO2 values for respiratory acidosis?
pH < 7.35
PaCO2 > 45 mmHg
Increase the patient’s ventilation!
what are the pH and PaCO2 values for respiratory alkalosis?
pH > 7.45
PaCO2 < 35 mmHg
Decrease the patients ventilation
what are the pH and HCO3 values for metabolic acidosis?
pH < 7.35
HCO3_ < 22 mEq/L
BE > -2 mEq/L
HCO3 = temporary fix
what are the pH and HCO3 values for metabolic alkalosis?
pH > 7.45
HCO3_ > 26 mEq/L
how is metabolic acidosis treated?
HCO3- (mEq/L)=BE x kg x 0.3
Treat underlying cause: (Hypovolemia, DKA, Hypoxia, etc) Blood products, fluid, oxygen, insulin, respiratory compensation (hyperventilation).
how is metabolic alkalosis treated?
Chloride administration, volume correction with NaCl, respiratory compensation (hypoventilation).
Treat underlying cause ( citrate toxicity, hypovolemia, vomiting/GI suction, diuretics)
what electrolytes are in NS? What is its osmolarity?
Na+
Cl-
308 mOsm/L
what electrolytes are in LR? What is its osmolarity?
Na+ Cl- K+ Ca2+ Lactate
273 mOsm/L
what electrolytes are in plasma-lyte? What is its osmolarity?
Na+ Cl- K+ Mg2+ acetate gluconate
294 mOsm/L
what are the pH levels the following crystalloids…
D5W, 0.9 NS, LR, and Plasma-Lyte?
D5W = 5 pH
0.9 NS = 4.2 pH
LR = 6.5 pH
Plasma-Lyte = 7.4 pH
NOTE: all of the other crystalloids we’ve studied have a pH around 5 - 5.6 .
