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Unit Code 9102:
Acid-Base Balance, Blood

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Useful For

Assessment of acid-base status in order to detect respiratory and/or

metabolic acidosis or alkalosis.

Clinical Information

Blood gas analysis is the standard approach to the assessment of

respiratory function in patients with potential respiratory compromise

and/or acid-base disorders. Patients presenting with a change in

consciousness, evidence of respiratory difficulty, and/or intoxication

may need such testing to determine the diagnosis and the need for

treatment. Periodic blood gas testing is also routine for patients

undergoing oxygen therapy, mechanical ventilation, anesthesia, or

resuscitation.

 

The acid-base balance test is intended for use with a venous blood

specimen to provide specific information that can be used to assess

the acid-base status of the patient. The use of a venous specimen may

be necessary due to the patient's condition and multiple studies have

shown that results from such a specimen provide a reasonable estimate

of acid-base status. In this test, the standard bicarbonate is reported;

this value eliminates the influence of respiration on the bicarbonate

concentration and represents only metabolic changes in acid-base

balance.

Reference Values

                                             

pH                                        7.32-7.42                    

PCO(2)                               41-51 torr                     

Standard bicarbonate  21.3-24.8 mmol/L       

Interpretation

Patient results vary depending on the underlying medical condition

and the type of therapy being received.

Cautions

Specimens should be iced immediately and analyzed

within 60 minutes of collection.

Clinical Reference

1.   Radiometer ABL 700 Series Reference Manual, Radiometer

      Medical A/S, Denmark, 2002

2.   Tietz Textbook of Clinical Chemistry. Edited by Burtis and

      Ashwood. Philadelphia, WB Saunders Company, 1999

3.   Kraut JA, Madias NE:  Approach to patients with acid-base

      disorders. Respir Care 2001;46:392-403

4.   Gennis PR, Skovron ML, AronsonST, et al:  The usefulness of

      peripheral venous blood in estimating the acid-base status in

      acutely ill patients. Ann Emerg Med 1985;14:845-49

5.   Brandenburg MA, Dire DJ:  Comparison of arterial and venous

      blood gas values in the initial emergency department evaluation

      of patients with diabetic ketoacidosis. Ann Emerg Med 1998;31:

      459-465

6.   Kelly AM, McAlpine R, Kyle E:  Venous pH can safely replace

      arterial pH in the initial evaluation of patients in the emergency

      department. Emerg Med J 2001;18:340-42

Key