ACID BASE BALANCE

NUR 101M. GardnerCopyright2/4/2013

ACID /BASE BALANCE In order to meet homeostasis, the

body fluids must maintain a stable chemical balance of hydrogen ions in body fluids.

This is done by regulating their acidity /alkalinity.

Deviation from a normal value indicates that the client is experiencing an acid/base imbalance

ACID/BASE BALANCE ACID – substance that releases

hydrogen ions (H+)

BASE – accept hydrogen ions in solution

This relationship is measured as pH.

ABG’S Measurement of ABGs involves

analysis of several components: pH PCO2 PO2 HCO3

ABCS of ABGs

Arterial blood gas analysis pH – measures the hydrogen ion

concentration it is an indication of the blood’s

acidity or alkalinity. Normal pH of body fluids is 7.35-7.45 pH 7 is neutral pH <7 is acid, pH >7 is alkaline

(base) acidic----neutral----alkaline

ABGs

PaCO2/PCO2 35-45mmHg

Carbon dioxide/CO2 Reflects adequate ventilation by the lungs Hyperventilation occurs PaCO2 <35mmHg.

RR/depth increases the more carbon dioxide is exhaled

Hypoventilation occurs PaCO2>45mmHg. RR/depth decreases, more carbon dioxide is

retained – increasing the concentration of CO2

ABGsHCO3 /Bicarbonate normal range 22-26mE/L base regulated by the kidneys the kidneys excrete and retain HCO3 to

maintain a normal acid/base balance is a principal buffer of the ECF

compartment

< 22mEq/L – indicates metabolic acidosis >26meq/L – indicates metabolic alkalosis

ABGs

PO2 – oxygen in arterial blood Normal range – 90-100mmHg

Regulation of Acid/Base Balance

Several body systems are actively involved in maintaining the narrow pH range necessary for optimal function.

This includes buffers, respiratory system, renal system

Buffers maintain acid/base balance by neutralizing excess acids/bases

The lungs/kidneys help maintain a normal pH by either excreting/retaining acid/bases.

BUFFERS A strong acid added to the ECF

causes the bicarbonate to become depleted neutralizing the acid pH drops acidosis

A strong base is added to the ECF, depleting carbonic acid the pH rises alkalosis

Buffer reaction is immediate

Respiratory Regulation Lungs regulate acid/base balance by

eliminating or retaining carbon dioxide (CO2)

Carbon dioxide powerful stimulator of the respiratory center

CO2 +H2O=H2CO3 this reaction is reversible

Renal Regulation Kidneys kick in by excreting or

retaining bicarbonate and hydrogen ions.

Slower to respond to changes hour/days to correct imbalances

Renal Regulation Excessive hydrogen ions are present

and the pH falls (acidosis) kidneys reabsorb bicarbonate & excrete hydrogen ions.

With alkalosis and high pH excess bicarbonate is excreted and hydrogen ions are retained.

ABG’s –Normal Value

pH 7.35 – 7.45Pa CO2 35-45 mm Hg

PaO2 80 -100 mm Hg HCO3 22-26 mEq/L

O2 Saturation 95-100%

Acid –Base Imbalances Are classified as respiratory or

metabolic considering the general/underlying cause of the disorder.

Respiratory acidosis/alkalosis retention/excretion of CO2

Bicarbonate /hydrogen levels are regulated by the kidneys, any problems metabolic acidosis/alkalosis

Respiratory Acidosis Client hypoventilates CO2 builds up

in the bloodstream and the pH drops below normal.

Kidneys try to compensate by conserving bicarbonate raises the pH

pH <7.35PaCO2 >45HCO3 normal or elevated if

compensating

Respiratory Acidosis

Causes: asthma, COPD chest wall trauma sedation medications Acute lung conditions

Respiratory Acidosis

Clinical Manifestations apprehension dizziness muscular twitching warm flushed skin lethargy diminished/absent breath sounds

over the affected area

Respiratory Acidosis

Interventions bronchodilator chest physiotherapy suction T,C, & DB narcotic antagonist

Respiratory Alkalosis Pt. hyperventilating this causes the

lungs to blow off CO2.

ABGpH > 7.45pCO2 <35HCO3 - normal or below 22, if

compensating

Respiratory Alkalosis

CausesHyperventilation due to extreme anxiety pain inappropriate mechanical ventilator

settings elevated body temperature

Respiratory Alkalosis

Clinical Manifestations increase in rate & depth of

respirations tachycardia anxious, restlessness

Respiratory Alkalosis

Interventions treat the underlying disorder allay anxiety – prevent

hyperventilation monitor VS assist client to breathe in a paper bag

Metabolic Acidosis Bicarbonate levels are low in relation

to the amount of carbonic acid pH low.

ABG pH is below 7.35 pCO2 normal, if less than 35 may be

compensated HCO3 -- <22 mEq/L

Metabolic Acidosis

Causes starvation diarrhea poisoning diabetes

Metabolic Acidosis

Clinical Manifestations headache lethargy confusion tachypnea with deep respirations

Metabolic Acidosis

Interventions treat the underlying problem replace F/E sodium bicarbonate – IV monitor neurological status

Metabolic Alkalosis Commonly associated with

hypokalemia Increase levels of bicarbonate

ABG pH >7.45 pCO2 normal or above 45 if

compensating HCO3 >26

Metabolic Alkalosis

Cause Excessive acid loss from the GI tract Diuretic therapy

Metabolic Alkalosis

Clinical manifestations Slow, shallow respirations S&S are commonly associated with

an underlying condition

Metabolic Alkalosis

Interventions monitor VS maintain patent IV access monitor I&O replace F&E

ABG Analysis It is a respiratory problem if the pH

and CO2 are traveling in the opposite directions.

pH< 7.35 & CO2 >45 = Respiratory Acidosis

pH >7.35 & CO2<35 = Respiratory Alkalosis

ABG Analysis It is a metabolic problem if the pH &

HCO3 are traveling in the same directions

pH <7.35 and the HCO3 <22 = Metabolic Acidosis

pH >7.45 and the HCO3>26 = Metabolic Alkalosis

Identify the Balance pH – 7.30 pCO2 – 36mmHg HCO3 – 14mEq/L

pH – 7.52 pCO2 – 47 mmHg HCO3 – 43 mEq/L

THINK ABOUT THIS The patient comes to the ER with

complaint of vomiting for 3 days. Which acid base imbalance is she at risk for?

The patient has just returned from surgery. He was medicated twice with narcotic analgesics in the PACU. He is difficult to arouse and has a respiratory rate of 12. what acid/base imbalance is he at risk for?

RELAX

Some day you will know all of this!!!!!!!!