View source for Arterial blood gas analysis

==Basics==
==='''pH'''===
*Measurement of acidity or alkalinity of solution . The normal range is 7.35 to 7.45
*pH > 7.45 = [[alkalosis]]
*pH< 7.35 = [[acidosis]]
==='''PaO<sub>2</sub>'''===
*The partial pressure of oxygen that is dissolved in the arterial serum that is ''not'' carried by hemoglobin. The normal range is 80 to 100 mm Hg.
**Used to assess alveolar-arterial (A-a) gradient, or [[P<sub>a</sub>O<sub>2</sub>/FiO<sub>2</sub> ratio]].
==='''SaO<sub>2</sub>'''===
*The arterial oxygen saturation
*The normal range is 95% to 100%.

==='''pCO<sub>2</sub>'''===
*The amount of carbon dioxide dissolved in arterial blood
*The normal range is 35 to 45 mm Hg.
*pCO<sub>2</sub> >45 = primary [[respiratory acidosis]]
*pCO<sub>2</sub> <35 = primary [[respiratory alkalosis]]

==='''HCO<sub>3</sub>'''===
*The calculated value of the amount of bicarbonate in the bloodstream
*The normal range is 22 to 26 mEq/liter
*HCO3 > 26 = [[alkalosis]]
*HCO3 < 22 = [[acidosis]]

==='''B.E.'''===
*The base excess indicates the amount of excess or insufficient level of bicarbonate in the system.
*The normal range is -2 to +2 mEq/liter.
*A negative base excess indicates a base deficit in the blood.


==ABG in [[Hypothermia]]==
*Blood gas analyzers typically warm blood to 37°C before making calculations however physicians should simply interpret the values as given by the lab
*At any temperature, a pH of 7.4 and a PCO2 of 40 mm Hg represent normal acid-base balance
The best (simplest) approach is to use uncorrected ABG values compared with the normal values at 37°C<ref>Burnett RW, Noonan DC. Calculations and correction factors used in determination of blood pH and blood gases. Clin Chem. 1974 Dec;20(12):1499-506. Review. </ref>
===TEMPERATURE CORRECTION OF PO2 and PCO2===
Oxygen and carbon dioxide increase in solubility as water temperature lowers, so warmed ABGs from hypothermic patients with show a  higher PaO2, higher PaCO2 and a lower pH than what is actually present in the patient’s blood although the clinical implications of this change is not significant.<ref>Ashwood ER, Kost G, Kenny M. Temperature correction of blood-gas and pH measurements. Clin Chem. 1983 Nov;29(11):1877-85. Review. PubMed PMID: 6354511.</ref>
*PO2 is 5 mmHg lower for each degree below 37C° 
*PCO2 is 2mmHg lower for each degree below 37C°

==ABG after [[Cardiac Arrest]]==
pH of blood dependent on:
*cause of arrest
*duration of arrest when ABG is taken
*the quality of the CPR and ventilation the patient is receiving
*temperature of the patient when ABG taken
*drugs administered during arrest (ie. Adrenaline and NaHCO3)

'''Elevated pCO<sub>2</sub>'''
*often due to inadequate ventilation during resuscitation

'''Low PaO2'''
*insufficient oxygenation during resuscitation
*aspiration
*[[pulmonary edema]]
*[[PE]]
*primary respiratory pathology

'''[[Hyperkalemia]] Causes'''
*cell death
*loss of cell membrane integrity and acidosis
*other sources such as missed dialysis

==References==
<references/>

[[Category:Critical Care]]
[[Category:Pulmonary]]