Acid-Base Balance & Arterial Blood Gases

normal pH

7.35-7.45

pH under 7.35

acidic, high hydrogen ion concentration

pH over 7.45

alkalotic/basic, low hydrogen ion concentration

pH below 6.8 or above 7.8

fatal

Arterial Blood Gas (ABG)

performed by arterial puncture

allen’s test for ABG

checking for arterial flow of the hand

• open and close palm and see if color comes back to palm

what happens to blood pressure when losing blood?

it drops

What is PTT and INR?

blood tests that measure how long it takes to form a blood clot

normal range of PaCO2 (carbon dioxide)

35-45 mm Hg

• acidic

normal range of HCO3 (Bicarbonate)

22-26 mEq/L

• basic

PaO2 normal range

80-95 mm Hg

SaO2 normal range

95%+

what is PaO2

partial pressure of oxygen in arterial blood

• most important factor in determining how O2 binds to hemoglobin

• used to measure respiratory function

what is SaO2

oxygen carrying capacity of Hgb

• pulse oximetry

• used to evaluate respiratory function

high levels of PaO2 and SaO2 =

unnecessarily high supplemental oxygen

low levels of PaO2 and SaO2=

hypoxemia

is CO2 is over 45

acidosis

• CO2 retention or hypoventilation

is CO2 is less than 35

alkalotic

• hyperventilation

HCO3

regulated by kidneys

• normal is 22-26 mEq/L

what are the three types of buffers that keep a normal pH

chemical, respiratory, and renal

chemical buffer

bases are released to help combine or neutralize strong acids

respiratory buffer

CO2

renal buffer

most effective but slowest

• kidneys either excrete or reabsorb bicarbonate or hydrogen

compensation

body wants a normal pH and tries to fix itself

if a acid base imbalance is from a metabolic issue…

respiratory system does the heavy lifting to correct

• body will change to respiratory rate to correct

if a acid base imbalance is from a respiratory issue…

renal system is “okay'‘

• body will either excrete or reabsorb hydrogen and bicarbonate to correct

uncompensated

• pH is abnormal

• body isn’t doing anything to fix itself

• either CO2 or bicarbonate will be normal

partially compensated

• pH is abnormal

• CO2 and bicarbonate are abnormal but opposites

• body trying to fix itself

fully compensated

• pH is normal

• CO2 and bicarbonate are abnormal

respiratory acidosis

caused by CO2 retention

• decreased respiratory depth and rate

• low pH and high CO2

what complications can result from respiratory acidosis?

can progress to cerebral vasodilation resulting in paralysis or coma

manifestations of respiratory acidosis

• dyspnea

• restlessness

• headache

• tachycardia

• confusion/lethargy

• respiratory distress

• dysrhythmias

treatment for respiratory acidosis

goal is to lower CO2

• bronchodilators, oxygen, antibiotics

respiratory alkalosis

caused by decrease in CO2, high pH low CO2

• blowing off CO2

  • hyperventilation

complications of respiratory alkalosis

• seizures

• chest pain

manifestations of respiratory alkalosis

• lightheadedness

• confusion

• paresthesia

• tetanic spasms

• palpitations

• sweating

• dry mouth

treatment for respiratory alkalosis

goal is to treat the underlying cause

• cool patient down

• oxygen

• sedative/anxiolytics

metabolic acidosis

caused by an increase in metabolic acids and decrease in bicarbonate

• low pH and low CO2

• formation of nonvolatile acids

• loss of alkali

• can’t get of acids by kidneys (renal failure)

  • leads to hyperkalemia

manifestations of metabolic acidosis

• confusion

• restlessness

• lethargy

• kussmal respirations

• nausea/vomiting (N/V)

• dysrhythmias

• warm, flushed skins

• seizures twitching

• peripheral vasodilation

complications of metabolic acidosis

• cardiac dysfunction, renal osteodystrophy, renal encephalopathy

treatment for metabolic acidosis

fluids, insulin, dialysis for kidney failure

metabolic alkalosis

caused by loss of acid or too much base, higher pH and HCO3

• body will compensate with hypoventilation and hypokalemia

complications of metabolic alkalosis

• cardiac dysrhythmias

manifestations of metabolic alkalosis

• muscle wasting

• tetany

• dizziness

• lethargy

• seizures

• coma

• N/V

metabolic alkalosis treatment

• discontinue potassium wasting diuretics

• stop NG tube suction

  • antiemetics