ABG's

Conditions that can cause hypoventilation? (which can then result in respiratory acidosis)

Central nervous system depression related to head injury Central nervous system depression related to medications such as narcotics, sedatives, or anesthesia Impaired respiratory muscle function related to spinal cord injury, neuromuscular diseases, or neuromuscular blocking drugs Pulmonary disorders such as atelectasis, pneumonia, pneumothorax, pulmonary edema, or bronchial obstruction Massive pulmonary embolus Hypoventilation due to pain, chest wall injury/deformity, or abdominal distension

Sometimes, the system that is compensating (respiratory or metabolic) may either have not had sufficient time to correct the situation, or is unable to completely compensate for the degree of abnormality present.

If the pH is between 7.35-7.45, the condition is fully compensated. If the pH is outside the range of 7.35-7.45, the condition is only partially compensated. Remember, neither buffer system has the ability to overcompensate!

Conditions that can cause hyperventilation? (which can then result in respiratory alkalosis)

Psychological responses, such as anxiety or fear Pain Increased metabolic demands, such as fever, sepsis, pregnancy, or thyrotoxicosis Medications, such as respiratory stimulants Central nervous system lesions

Activation of the lungs to compensate for an imbalance starts to occur with in how long?

1-3 min

What is the normal acid to base ratio?

1:20

Normal HCO3

22-26

Normal PaCO2 values

35-45

Normal pH values

7.35-7.45

Normal PaO2

80-100

Normal SaO2

95%-100%

Metabolic alkalosis is one of the most difficult acid-base imbalances to treat. How do you treat?

Bicarbonate excretion through the kidneys can be stimulated with drugs such as acetazolamide (Diamox®), but resolution of the imbalance will be slow. In severe cases, IV administration of acids may be used.

ABG Example: pH 7.38, PCO2 56, HCO3 35

Compensated Respiratory Acidosis. Because the acidosis is completely compensated, and we know the kidneys take hours to days to respond, we know that this patient's respiratory problem has been going on for some time.

What can cause metabolic alkalosis?

Excess of base or a loss of acid within the body can cause metabolic alkalosis. Excess base occurs from ingestion of antacids, excess use of bicarbonate, or use of lactate in dialysis. Loss of acids can occur secondary to protracted vomiting, gastric suction, hypochloremia, excess administration of diuretics, or high levels of aldosterone.

What can correct respiratory acidosis?

Increasing ventilation. The method for achieving this will vary with the cause of hypoventilation. If the patient is unstable, manual ventilation with a bagmask is indicated until the underlying problem can be addressed. After stabilization, rapidly resolvable causes are addressed immediately. Causes that can be treated rapidly include pneumothorax, pain, and CNS depression related to medications. If the cause cannot be readily resolved, the patient may require mechanical ventilation while treatment is rendered. Although patients with hypoventilation often require supplemental oxygen, it is important to remember that oxygen alone will not correct the problem.

how is the body able to self-regulate acid-base balance in order to maintain pH within the normal range?

It is accomplished using delicate buffer mechanisms between the respiratory and renal systems.

Signs and Symptoms of Metabolic Acidosis: pulmonary

Kussmaul's respirations

Signs and Symptoms of Metabolic Alkalosis: GI

Nausea vomiting

Causes of increased acids include

Renal failure Diabetic ketoacidosis Anaerobic metabolism Starvation Salicylate intoxication

Signs and Symptoms of Metabolic Alkalosis: pulmonary

Respiratory depression

How do you know when compensation is occurring?

When an acid-base disorder is either uncompensated or partially compensated, the pH remains outside the normal range. In fully compensated states, the pH has returned to within the normal range, although the other values may still be abnormal. Be aware that neither system has the ability to overcompensate.

Diamox

a carbonic anhydrase inhibitor that decreases H+ ion secretion and increases HCO3 excretions by the kidneys, causing a diuretic effect.

Chronic obstruction pulmonary disease (COPD):

a disease process involving chronic inflammation of the airways, including chronic bronchitis (disease in the large airways) and emphysema (disease located in smaller airways and alveolar regions). The obstruction is generally permanent and progressive over time.

Conditions that cause enhanced release of the oxygen molecule include

acidosis, fever, elevated CO2 levels, and increased 2,3-diphosphoglycerate (2,3-DPG, a by-product of glucose metabolism). This change in affinity is called a shift to the right (C waveform).

Iatrogenic:

any condition induced in a patient by the effects of medical treatment.

In an effort to maintain the pH of the blood within its normal range, the kidneys excrete or retain, what?

bicarbonate (HCO3)

Metabolic alkalosis is defined as

bicarbonate level greater than 26 mEq/liter with a pH greater than 7.45

Metabolic acidosis is defined as

bicarbonate level of less than 22 mEq/L with a pH of less than 7.35.

Significant changes in the blood pH above 7.8 or below 6.8 will interfere with what?

cellular functioning, and if uncorrected, will lead to death.

Treatment of respiratory alkalosis

centers on resolving the underlying problem. Patients presenting with respiratory alkalosis have dramatically increased work of breathing and must be monitored closely for respiratory muscle fatigue. When the respiratory muscles become exhausted, acute respiratory failure may ensue.

Correction of a patient's blood oxygenation level may be accomplished through

combination of augmenting the means of oxygen delivery and correcting existing conditions that are shifting the oxyhemoglobin curve.

Changes in body system functions that occur in an acidic state

decrease in the force of cardiac contractions, a decrease in the vascular response to catecholamines, and a diminished response to the effects and actions of certain medications.

Metabolic acidosis is caused by either

deficit of base in the bloodstream or an excess of acids, other than CO2. (Diarrhea and intestinal fistulas may cause decreased levels of base)

Signs and Symptoms of Metabolic Alkalosis: neurological

dizziness lethargy disorientation seizures coma

Signs and Symptoms of Respiratory Alkalosis: Miscellaneous

dry mouth tetanic spasms of the arms and legs

Signs and Symptoms of Respiratory Acidosis: Pulmonary

dyspnea respiratory distress shallow respirations

Signs and Symptoms of Respiratory Alkalosis: cardiovascular

dysrhythmias palpitations diaphoresis

Signs and Symptoms of Metabolic Acidosis: Cardiovascular

dysrhythmias warm, flushed skin

The only 2 ways an alkalotic state can exist?

from either too little pCO2 or too much HCO3.

The only 2 ways an acidotic state can exist?

from either too much pCO2 or too little HCO3.

Although the kidneys provide an excellent means of regulating acid-base balance, the system may take, how long to correct an imbalance?

from hours to days to correct the imbalance.

Signs and Symptoms of Metabolic Acidosis: neurological

headache confusion restlessness lethargy stupor or coma

Signs and Symptoms of Respiratory Acidosis: Neurologic

headache restlessness confusion

If the oxygen binds too loosely to hemoglobin

hemoglobin may give up its oxygen before it reaches the tissues in need.

Conditions that keep the oxygen molecule tightly attached to hemoglobin include

hypothermia, alkalosis, low PCO2, and decrease in 2,3-DPG. This change is called a shift to the left (B waveform). A shift to the left has more negative implications for the patient than a shift to the right.

The presence of metabolic acidosis should spur a search for?

hypoxic tissue somewhere in the body. Hypoxemia can lead to anaerobic metabolism system-wide, but hypoxia of any tissue bed will produce metabolic acids as a result of anaerobic metabolism even if the PaO2 is normal.

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. Remember: A negative base excess indicates a base deficit in the blood.

If the oxygen binds too tightly

it may not transfer to the tissues at all.

the use of sodium bicarbonate is indicated only for?

known bicarbonate-responsive acidosis, such as that seen with renal failure. Routine use of sodium bicarbonate to treat metabolic acidosis results in subsequent metabolic alkalosis with hypernatremia and should be avoided.

Signs and Symptoms of Respiratory Alkalosis: Neurological

light-headedness numbness and tingling confusion inability to concentrate blurred vision

Signs and Symptoms of Metabolic Acidosis: GI

nausea and vomiting

Respiratory alkalosis is defined as

pH greater than 7.45 with a PaCO2 less than 35 mm Hg.

Respiratory acidosis is defined as

pH less than 7.35 with a PaCO2 greater than 45 mm Hg.

Any condition that results in hypoventilation, causes what type of acid base balance?

respiratory acidosis (not breathing off the CO2). Hyperventilation causes respiratory alkalosis

The only appropriate way to treat this source of acidosis is to?

restore tissue perfusion to the hypoxic tissues. Other causes of metabolic acidosis should be considered after the possibility of tissue hypoxia has been addressed.

Signs and Symptoms of Respiratory Acidosis: Cardiovascular

tachycardia dysrhythmias

An alkalotic state interferes with what?

tissue oxygenation and normal neurological and muscular functioning

Thyrotoxicosis:

toxic condition due to hyperactivity of the thyroid gland. Symptoms include rapid heart rate, tremors, increased metabolic basal metabolism, nervous symptoms and loss of weight.

Signs and Symptoms of Metabolic Alkalosis: musculoskeletal

weakness muscle twitching muscle cramps tetany