Acid-Base Balance Flashcards
(46 cards)
Electrolytes
* Bicarbonate (HCO3-)
* Major buffer in the body
* In ECF & ICF
* Normal serum level is ___ - ___ mEq/L
22-26
Function
* Maintains acid-base balance by functioning as the primary buffer in the body; levels rise and fall to maintain pH
Regulation
* Lost through diarrhea, diuretics, renal insufficiency
* Excess possible if person ingests quantities of acid neutralizers
Source
* Present in acid neutralizers (e.g. sodium bicarbonate)
* Not consumed in the diet; produced by the body to meet current needs
Normal Blood pH Scale
pH : 7.35 - 7.45
PaCO2 (respiratory) : ___ - ___
HCO3 (metabolic) : ___ - ___
35-45
22-26
Acid-Base Regulation
Acids & bases are formed in the body as part of normal metabolic processes
A ___ or ___ is a compound that combines with (accepts) H+ ions in solution
A(n) ___ is any compound that contains H+ ions that can be released
* e.g. common strong = HCI - gastric secretions
base; alkali
acid
pH Measurement
* The amount of acid or base present in a solution is measured as pH
* The pH is reported on a scale of 1 to 14
> 1 to 6.9 is acidic
> 7 is neutral
> 7.1 to 14 is basic, or alkaline
Strong acid = lower pH
Strong base = high pH
Normal serum pH - arterial blood and tissue fluid normally have a pH of 7.35 to 7.45; therefore, they are slightly alkaline
* A serum pH below 7.30 or above 7.52 alters enzymatic activity and creates myocardial irritability
* A serum pH below 6.9 or above 7.8 is usually fatal
3 complex mechanisms maintain acid-base balance;
- Buffers
- Respiratory control of carbon dioxide
- Renal regulation of bicarbonate (HCO3-)
Regulation - Buffers
* Buffer systems prevent wide swings in pH
* Consist of a weak acid and a weak base
* Buffer molecules keep strong acids or bases from altering the pH either by absorbing or releasing free H+
Blood and tissue fluids depend on this buffer system to maintain constant pH
Buffers
- Proteins (plasma : (-) & (+) ions)
- Hemoglobin (found on RBC)
- Phosphate (weak base & weak acid)
- Bicarbonate: carbonic acid (weak base & weak acid)
Regulation - Respiratory Mechanisms
* The lungs are the 2nd line of defense to restore normal pH
* They control the body’s carbonic acid supply via CO2 retention or removal to maintain the 20:1 ratio of base to acid
* When the serum pH is too acidic (pH is low), the lungs remove CO2 through rapid, deep breathing. This reduces the amount of CO2 available to make carbonic acid
* When the serum pH is too alkaline (pH is high), the lungs try to conserve CO2 through shallow respirations
Respiratory regulation of blood pH
H2CO3 - carbonic acid
Regulation - Renal Mechanisms
* The last line of defense is the kidneys, which regulate the concentration of plasma bicarbonate (HCO3)
* If the serum pH is too acidic, the kidneys conserve additional bicarbonate to neutralize the acid
* If the serum pH is too alkaline, the kidneys excrete additional bicarbonate to lower the amount of base and thereby decrease the pH
* The kidneys also buffer pH by forming acids and ammonium (a base)
Regulation
Acidosis = serum pH falls below ___
Alkalosis = serum pH increases above ___
- 35
- 45
ABGs measure;
pH
partial pressure of oxygen (PO2)
partial pressure of carbon dioxide (PCO2)
saturation of oxygen (SaO2)
bicarbonate (HCO3)
Respiratory disturbance alters carbonic acid = RESPIRATORY ACIDOSIS OR ALKALOSIS
Metabolic disturbance alters bicarbonate = METABOLIC ACIDOSIS OR ALKALOSIS
Key Point: Acid-base balance is reflected by the pH, PCO2, and HCO3- values
A respiratory disturbance alters the ___ portion of the buffering system, and the resulting imbalance is labeled respiratory acidosis or respiratory alkalosis
A metabolic disturbance alters the ___ portion of the buffering system, so the resulting imbalance would be labeled metabolic acidosis or metabolic alkalosis
carbonic acid
bicarbonate
Acidosis or Alkalosis? Interpreting ABGs
Step 1: Examine the pH Is it acidotic, alkalotic, or normal?
If the pH is low (<7.35), the blood is acidic
If the pH is high (>7.45), the blood is alkalotic
If the pH is between 7.35 and 7.45, the blood is normal
Neutral pH is 7.4
The partial pressure of oxygen (PO2) and saturation of oxygen (SaO2) are also part of the ABG result, but they affect tissue oxygenation
Acidosis or Alkalosis? Interpreting ABGs
Step 2: Check the amount of carbon dioxide in the blood (PCO2) Is there too much or too little?
If PCO2 is <35 mm Hg, there is too little acid in the blood (respiratory ___)
If PCO2 is >45 mm Hg, there is too much acid in the blood (respiratory ___)
If PCO2 is 35 to 45 mm Hg, the cause for the abnormal pH is not respiratory
alkalosis
acidosis
Acidosis or Alkalosis? Interpreting ABGs
Step 3: Think about bicarbonate level (HCO3-) Is there too little or too much?
If HCO3- is <22 mEq/L, there is too little base in the blood (metabolic ___)
If HCO3- is >26 mEq/L, there is too much base in the blood (metabolic ___)
If HCO3- is 22 to 26 mEq/L, the cause for the abnormal pH is not metabolic
acidosis
alkalosis
Respiratory ___
Caused by conditions or medications that IMPAIR GAS EXCHANGE at the alveolar-capillary membrane, depressed respiratory rate and depth, or injury to the respiratory center in the brain
Acidosis
Clinical Manifestations
Acute:
Increased pulse and respiratory rate
Headache, dizziness
Confusion, decreased level of consciousness (LOC)
Muscle twitching
Chronic: Weakness, headache
Interventions
- Provide pulmonary hygiene (methods used to clear mucous & secretions from airways)
- Institute measures to improve gas exchange, such as chest physiotherapy, bronchodilators, antibiotics possible
- Provide supplemental oxygen
- Maintain hydration
Respiratory Acidosis is an acid-base imbalance characterized by increased partial pressure of arterial CO2 and decreased blood pH
Contributing Factors
- Chronic obstructive respiratory disorders
- Chest wall trauma, pulmonary edema, atelectasis, pneumothorax, drug overdose, pneumonia, Guillain-Barre syndrome
- Any condition that results in hypoventilation
Signs & Symptoms/Clinical Manifestations
- Increased pulse, RR, & BP
- Mental cloudiness & feeling of fullness in head
- Weakness, dull headache
Labs indicated: ABG studies reveal abnormal values: pH below 7.35 & pCO2 above 45 mmHg
Nursing Diagnoses
- Impaired gas exchange
- Ineffective breathing pattern
- Ineffective tissue perfusion
- Acute confusion
- Risk for injury
Medical Management/Nursing Interventions
- Institute safety measures
- Assist w/positioning
- Monitor I&O and administer fluids as ordered
- Administer oxygen and medications for order; monitor hourly VS and respiratory status (may require mechanical ventilation)
- Monitor ABGs - pH, PaCO2, HCO3
Respiratory ___
Retention of CO2 by lungs
Acidosis
Respiratory ___
Caused by hyperventilation resulting from anxiety, fever, sepsis, thyrotoxicosis, lesion in the respiratory center in the brain, or excessive ventilation w/a mechanical ventilator
Alkalosis
