Fluids, electrolytes, & acid-base 4 Flashcards
The body attempts to regulate blood pH to
7.40
Normal pH is
7.35-7.45
Acidosis pH is
<7.35
_______________ details how PaCO2 and HCO3 influence pH.
The Henderson-Hasselbalch equation
Buff systems that help mitigate pH changes include
the blood (bicarbonate & hemoglobin)
lungs (changes in ventilation)
kidneys
What is normal HCO3?
22-26 mEq/L
What 5 questions should you ask yourself when evaluating pH?
- Is the pH normal
- Is the PaCO2 normal
- Is the HCO3- normal
- Has compensation occurred?
- If there’s metabolic acidosis, is the anion gap normal or increased?
Acidosis causes ___________________ P50, SNS stimulation, risk of dysrhythmias, myocardial depression, increased pulmonary vascular resistance, hyperkalemia, and increased ICP
Increased
Alkalosis causes ______________ P50, decreased coronary blood flow, risk of dysrythmias, decreased cerebral blood flow, decreased pulmonary vascular resistance, hypokalemia, and decreased ionized calcium.
decreased
H+ is __________ cells and K+ is _____________ cells
transported into cells and K+ is transported out of cells
Acidosis is often accompanied by _________kalemia
hyperkalemia
What is a normal anion gap?
8-12 mEq/L
Metabolic acidosis can have a
normal anion gap & an increased anion gap
Reasons for an increased anion gap in the setting of metabolic acidosis include
MUDPILES
methanol
uremia
diabetic ketoacidosis
paraldehyde
isoniazid
lactate
ethanol, ethylene glycol
salicylates
Reasons for a normal anion gap in the setting of metabolic acidosis include
HARDUP
hyperaldosteronism
acetazolamide
renal tubular acidosis
diarrhea
uretosigmoid fistula
pancreatic fistula
Full compensation causes pH
to return to normal
Compensation for metabolic disorders is ________- due to changes in _______________
rapid; changes in minute ventilation
Consider a mixed disorder if
the PaCO2 & bicarb both shift towards acidosis or alkalosis
the PaCO2 & bicarb are abnormal, but the expected degree of compensation did not occur
Which acid-based disorder is MOST likely to occur in response to untreated pain in the PACU?
a. respiratory acidosis
b. respiratory alkalosis
c. metabolic acidosis
d. metabolic alkalosis
b. respiratory alkalosis
Respiratory acidosis occurs when
alveolar ventilation fails to keep up with CO2 production
Causes of hypercarbia include
increased CO2 production
decreased CO2 elimination
rebreathing
Reasons for increased CO2 production include
sepsis
thyroid storm
MH
Reasons for decreased CO2 elimination include
airway obstruction
COPD
opioid overdose
Reasons for rebreathing include
incompetent unidirectional valve
exhausted soda lime
Mechanical ventilation is indicated when the pH is less than
7.20
Respiratory alkalosis occurs when
alveolar ventilation exceeds CO2 production
Causes of respiratory alkalosis include
iatrogenic (mechanical ventilation)
pain
pulmonary embolism
hypoxia
anxiety
pregnancy
drugs (progesterone, salicylates)
With acute respiratory acidosis, for every 10 mmHg increase in PaCO2, pH
decreases by 0.08
With chronic respiratory acidosis, for every 10 mmHg increase in PaCO2, pH
decreases by 0.03
During respiratory acidosis, the kidneys
excrete hydrogen & conserve bicarbonate to return pH to normal
In the lungs, CO2 is a
direct-acting vasoconstrictor, where it can cause pulmonary hypertension and increase the right ventricular workload
The most common cause of respiratory acidosis is
hypoventilation
The MOST likely etiologies of metabolic alkalosis include: (select 2)
a. large volume resuscitation with NaCl
b. vomiting
c. massive transfusion
d. diabetic ketoacidosis
b. vomiting
c. massive transfusion
Metabolic acidosis is caused by an
accumulation of nonvolatile acids
loss of bicarbonate
large volume resuscitation with a sodium chloride solution
_____________ helps to determine the cause of acidosis
the anion gap
An increased anion gap occurs in the setting of
diabetic ketoacidosis, salicylates, and cyanide poisoning
A normal anion gap occurs in the setting of
diarrhea, pancreatic fistula, and resuscitation with NaCl solutions
_______________ used for anion gap acidosis is controversional.
Sodium bicarbonate
Sodium bicarbonate is best used as a
temporary measure if the pH is <7.2 and the patient is hemodynamically unstable
Metabolic alkalosis is caused by
increased bicarbonate (iatrogenic), loss of nonvolatile acids (continuous NG suction), and increased mineralocorticoid activity (Cushing’s syndrome)
How do you calculate the anion gap?
Na+ - Cl- + HCo3
Accumulation of acid leads to
gap acidosis
Loss of bicarbonate or ECF dilution leads to
non-gap acidosis
An anion gap acidosis is defined as
pH <7.35 and anion gap >14
PaCO2 decreases by _______ for every HCO3- decrease of 1 mEq/L
1-1.5 mmHg
Administering sodium bicarbonate for non-anion gap acidosis is generally
useful because most of the etiologies produce bicarbonate loss
PaCO2 increases by _______- for every HCO3- increase of 1 mEq/L
0.5-1 mmHg
Treatment for metabolic alkalosis includes
treat the underlying cause
-acetazolamide (increases renal excretion of bicarb)
dialysis
-spironolactone (mineralcorticoid antagonist)
Name 5 etiologies that lead to metabolic alkalosis.
massive blood transfusion
vomiting
diuretics
Cushing’s syndrome
hyperaldosteronism
