ABGs Flashcards
Purpose of ABG Interpretation
- Assessment of oxygenation status of blood
- Assessment of ventilation/gas exchange
- Assessment of acid/base balance
- Evaluation of treatments used to correct acid/base imbalances
Measurement of Oxygenation
- PaO2
- A measure of the partial pressure (P) of oxygen dissolved in arterial blood plasma
- Normal Range: 80-100mmHg
Measurement of Ventilation
- pH
- PaCO2
- HCO3
pH
- The pH is the hydrogen ion. (H+) concentration of plasma
- Normal Range: 7.35-7.45
PaCO2
- A measure of the partial pressure of carbon dioxide dissovled in arterial blood plasma
- LUNGS
- Normal Range: 35-45mmHg
HCO3
- Bicarbonate (HCO3) is the acid-base component tht reflects kidney function
- HCO3 lvl is reduced or incrd in the plasma by renal mechanisms
- KIDNEYS
- Normal Range: 22-26mEq/L
Acidosis
pH < 7.35
Alkalosis
pH > 7.45
Respiratory Acidosis
- pH < 7.35
- PaCO2 incrd, > 45mmHg
Metabolic Acidosis
- pH < 7.35
- HCO3 dcrd, < 22mEq/L
Respiratory Alkalosis
- pH > 7.45
- PaCO2 dcrd, < 35mmHg
Metabolic Alkalosis
- pH > 7.45
- HCO3 incrd, > 26mEq/L
PaO2 - Mild Hypoxemia
60-79%
PaO2 - Moderate Hypoxemia
40-59%
PaO2 - Severe Hypoxemia
<40%
Base Range
- Base excess & base deficit reflect the nonrespiratory contribution to acid-base balance
- Normal Range: -2mEq/L to +2mEq/L
High Base
- Base excess (> +2mEq/L)
- Indicates tht there is a higher than normal amnt of HCO3 in the blood, may be due to a primary metabolic alkalosis or a compensated respiratory acidosis
- The base excess is another surrogate marker of metabolic acidosis or alkalosis
Low Base
- Base deficit (< -2mEq/L)
- Indicates tht there is a lower than normal amnt of HCO3 in the blood, suggesting either a primary metabolic acidosis or a compensated respiratory alkalosis
Compensatory Responses
-
Responses by the lungs (Co2) and kidney (HCO3) to metabolic and respiratory disturbances
> respiratory compensation is rapid
> metabolic compensation is slow
Uncompensated
-
pH = abnormal
> less than 7.35 or greater than 7.45 - PaCO2 &/or HCO3 = abnormal
- Body does not have enough time to return pH back to normal
Compensated
-
pH = “normal”
> determine which side of 7.40 is closer to - PaCO2 & HCO3 = abnormal
- Body had enough time to restore pH back to normal
Partial Compensation
- pH = abnormal
- PaCO2 = abnormal
- HCO3 = abnormal
- Body is attempting to return pH to normal
Respiratory Acidosis - Uncompensated
- pH low (acidic)
- PaCO2 high (acidic)
- HCO3 normal
Respiratory Acidosis - Partially Compensated
- pH low (acidic)
- PaCO2 incrd (acidic)
- HCO3 incrd (basic)
Respiratory Acidosis - Compensated
- pH normal
- PaCO2 incrd (acidic)
- HCO3 incrd (basic)
Respiratory Acidosis - Causes
- Airway obstruction
-
CNS depression
> hypoventilation, opioids - Brain stem injury
- Sleep apnea
- Neuromuscular impairment
-
Ventilatory restriction
> asthma, COPD -
Incrd CO2 production
> shivering, rigors, seizures, malignant hyperthermia, hypermetabolism, incrd intake of carbs - Incorrect ventilator settings
Respiratory Acidosis - Treatment
- Treat underlying cause
- Oxygen
- Mechanical ventilation
- Suction
- Bronchodilators
Respiratory Acidosis - Signs & Symptoms
- R/T cause
- Confusion, lethargy, dyspnea, pale or cyanotic skin, mental cloudiness, restlessness, HTN, weakness, headache, incrd resp effort w/ nasal flaring/yawning, use of neck & upper body muscles
-
Dcrd resp rate/hypoventilation
> associated w/ dcrd function of resp center as in head trauma, oversedation, general anesthesia, metabolic alkalosis - Adventitious breath sounds (crackles, wheezes); stridor, crowing
Respiratory Alkalosis - Uncompensated
- pH high (basic)
- PaCO2 dcrd (basic)
- HCO3 normal
Respiratory Alkalosis - Partially Compensated
- pH low (basic)
- PaCO2 incrd (basic)
- HCO3 incrd (acidic)
Respiratory Alkalosis - Compensated
- pH normal
- PaCO2 dcrd (basic)
- HCO3 dcrd (acidic)
Respiratory Alkalosis - Causes
-
Hypoxemia or hypoxia
> lung disease, profound anemia, low FiO2 - Incorrect ventilator settings
-
CNS stimulation
> fever, pain, fear, anxiety, CVA, cerebral edema, brain trauma/tumor, CNS infection - Pulmonary embolism
Respiratory Alkalosis - Treatment
- Treat the underlying cause
- Mechanical ventilation
- Buffers
-
Have the pt rebreathe air tht has been exhaled
> put on a non-rebreather on w/o oxygen
Respiratory Alkalosis - Signs & Symptoms
- Deep rapid breathing (40+ bpm)
- CNS & neuromuscular disturbances: lightheadedness, agitation, circumoral & peripheral paresthesias, carpopedal spasms, twitching & muscle weakness, N/V, muscle twitching
Metabolic Acidosis - Uncompensated
- pH low (acidic)
- PaCO2 normal
- HCO3 dcrd (acidic)
Metabolic Acidosis - Partially Compensated
- pH low (acidic)
- PaCO2 dcrd (basic)
- HCO3 dcrd (acidic)
Metabolic Acidosis - Compensated
- pH normal
- PaCO2 dcrd (basic)
- HCO3 dcrd (basic)
Metabolic Acidosis - Causes
- Hypoxia
- Lactic acidosis
- Ketoacidosis
-
Renal failure
> uremic acidosis -
GI loss of HCO3
> diarrhea -
Renal loss of HCO3
> renal tubular acidosis, diamox -
Poison
> salucylate intoxication, methanol, ethylene glycol - Overconsumption of alcohol
- Rhabdomyolysis
Metabolic Acidosis - Treatment
- Treat the underlying cause
- Buffers
Metabolic Acidosis - Signs & Symptoms
- Headache
- Drowsiness & confusion
- Weakness
- Incrd resp rate & depth
- N/V
-
Diminished cardiac output w/ pH < 7
> results in hypotension, cold clammy skin, & cardiac arrhythmias
Metabolic Alkalosis - Uncompensated
- pH high (basic)
- PaCO2 normal
- HCO3 incrd (basic)
Metabolic Alkalosis - Partially Compensated
- pH high (basic)
- PaCO2 high (acidic)
- HCO3 high (basic)
Metabolic Alkalosis - Compensated
- pH normal
- PaCO2 high (acidic)
- HCO3 high (basic)
Metabolic Alkalosis - Causes: GI Loss of H+
- Nasogastric suctioning
- Gastric lavage
- Prolonged vomiting
Metabolic Alkalosis - Causes: Renal Loss of H+
- Loop & thiazide diuretics
-
Edematous states
> heart failure, cirrhosis, nephrotic syndrome - Hyperaldosteronism
- Hypercortisolism
- Excess ACTH
- Exogenous steroids
- Hyperreninemia
- Severe hypokalemia
- Renal artery stenosis
- Bicarbonate administration
- Hypokalemia
Metabolic Alkalosis - Causes: Retention/Addition of Bicarbonate
Excessive quantities of antacids
Metabolic Alkalosis - Treatment
- Treat underlying cause
- KCL
- Volume
- Arginine monohydrochloride
- HCL
Metabolic Acidosis Examples
- DKA
- Renal failure
Metabolic Alkalosis Examples
-
Chronic indigestion & use antacids daily
> antacids are alkalotic - Long term nasogastric suctioning
Narcotic Overdose
Respiratory acidosis
narcotics depress resp system
Anxiety Attack
Respiratory alkalosis
hyperventilation = breathing off too much CO2