NURS 211 Ch 12 Assessment and Care of Patients With Problems of Acid-Base Balance.

respiratory acidosis: pathology: underelimination of hydrogen ions

Conditions: Respiratory depression: Anesthetics Drugs (especially opioids) Electrolyte imbalance Inadequate chest expansion: Muscle weakness Airway obstruction Alveolar-capillary block

metabolic acidosis: pathology: overelimination of bicarbonate

Conditions: diarrhea

metabolic acidosis: pathology: underelimination of hydrogen ions

Conditions: kidney failure

Acid base assessement: PaCO2: SIGNIFICANCE OF ABNORMAL FINDINGS

Increased: Respiratory acidosis, emphysema, pneumonia, cardiac failure, respiratory depression Decreased: Respiratory alkalosis, excessive ventilation, diarrhea

Acidosis; pt Hx

Older adults are more at risk for problems leading to acid-base imbalance, including cardiac, kidney, or pulmonary impairment -They also may be taking drugs that disrupt ACID-BASE BALANCE, especially diuretics & aspirin. -Ask about specific risk factors such as any type of breathing problem, kidney failure, diabetes mellitus, diarrhea, pancreatitis & fever.

Management: Acid deficits can be caused by disease processes or medical treatment. Disorders causing acid deficits include

prolonged vomiting, excess cortisol, and hyperaldosteronism. Treatments that promote acid loss causing metabolic alkalosis include thiazide diuretics and prolonged gastric suctioning.

PaCO2 PaO2

-Partial pressure of arterial carbon dioxide; -partial pressure of arterial oxygen.

Acidosis patho

-Patients at greatest risk for acute acidosis- pt's c problems that impair breathing, older adults c chronic health problems -Problems that increase acid production include diabetic ketoacidosis and seizures. -Problems that decrease acid elimination include respiratory impairment and kidney impairment. -relative acidosis: the amount of acids does not increase. Instead the amount or strength of the bases decreases (to create a base deficit), which makes the fluid relatively more acidic than basic. -A relative acidosis (base deficit) is caused by either overeliminating or underproducing bicarbonate ions (HCO3−). Problems that underproduce bases include pancreatitis and dehydration. A condition that overeliminates bases is diarrhea.

Bicarbonate ions

-The most common base (HCO3−); -the most common acid carbonic acid (H2CO3). - body keeps both @ ratio of 1 molecule of carbonic acid to 20 free bicarbonate ions (1 : 20) -to keep ration body must balance the production and elimination of carbon dioxide (CO2) and hydrogen ions (H+).

the carbon dioxide content of a fluid is directly related to the amount of hydrogen ions in that fluid.

-Whenever conditions cause carbon dioxide to increase, more free hydrogen ions are created. Likewise, whenever free hydrogen ion production increases, more carbon dioxide is produced.

ALKALOSIS

-an excess of bases, especially bicarbonate (HCO3−). -amount or strength of the bases is greater than normal compared with the amount of the acids. -Alkalosis is a decrease in the free hydrogen ion level of the blood and is reflected by an arterial blood pH above 7.45.

Buffers

-can react either as an acid (releasing a hydrogen ion) or as a base (binding a hydrogen ion). -Buffers always try to bring the fluid as close as possible to the normal body fluid pH of 7.35 to 7.45. -If the fluid is basic (with few free hydrogen ions), the buffer releases hydrogen ions into the fluid -If the fluid is acidic (with many free hydrogen ions), the buffer binds some of the excess hydrogen ions. -In this way buffers act like hydrogen ion "sponges," soaking up hydrogen ions when too many are present and squeezing out hydrogen ions when too few are present.

Nursing Safety Priority Assess the ------------- system first in any patient at risk for acidosis because --------

-cardiovascular system -acidosis can lead to cardiac arrest from the accompanying hyperkalemia. If cardiac changes are present, respond by reporting these changes immediately to the health care provider. -Arterial blood pH is the laboratory value used to confirm acidosis

Interventions for metabolic acidosis include

-hydration & drugs or treatments to control the problem causing the acidosis. -EX: if the acidosis is from diabetic ketoacidosis, insulin is given to correct the hyperglycemia and halt the production of ketone bodies. Rehydration and antidiarrheal drugs are given if the acidosis is a result of prolonged diarrhea. Bicarbonate is administered only if serum bicarbonate levels are low and the pH is less than 7.2. Nursing priorities: continuously monitoring the patient for indications either they're responding to the tx or the acidosis is becoming worse. The cardiovascular & skeletal muscle systems are sensitive to acidosis and are the most important systems to monitor. Interpreting ABG results is an important part of monitoring.

acid base balance

-maintenance of arterial blood pH between 7.35 and 7.45 through regulation of hydrogen ion (H+) production & elimination. -pH- indirect measure of the free hydrogen ion level in the blood and other body fluids. -A change of 1 pH unit actually represents a tenfold change in free hydrogen ion level

Interventions for respiratory acidosis

-same as those used for a patient with (COPD), which is the most common health problem associated with continuing risk for respiratory acidosis. -Drug therapy - focus on ventilation/gas exchange rather than directly on altering pH. Include: bronchodilators, anti-inflammatories, and mucolytics. Oxygen therapy: monitor oxygen saturation levels to ensure that the lowest flow of oxygen that prevents hypoxemia is used to avoid oxygen-induced tissue damage. Ventilation support with mechanical ventilation may be needed for patients who cannot keep their oxygen saturation at 90% or who have respiratory muscle fatigue. -Monitoring breathing status hourly -Listen to breath sounds and assess how easily air moves into and out of the lungs. -Check for any muscle retractions, the use of accessory muscles (especially the neck muscles [sternocleidomastoids]), and whether breathing produces a grunt or wheeze that can be heard without a stethoscope. -Assess nail beds and oral membranes for cyanosis (a late finding).

acids

-substances that release (H+) ions when dissolved in water (H2O) or body fluids, increasing the amount of free hydrogen ions in that solution. -strength of an acid is measured by -how easily it releases a (H+) ion in solution. -A strong acid (ex HCl) separates completely in water and releases all of its hydrogen ions -A weak acid releases only some (H+) ions

compensation

-the body adapts to attempt to correct changes in blood pH and maintain ACID-BASE BALANCE. -A pH below 6.9 or above 7.8 is usually fatal.

Acid Base Assessment: ph >90 yr: arterial:

7.25-7.45

Acid Base Assessment: ph <90 yr: venous:

7.31-7.41

Acid Base Assessment: ph >90 yr: venous:

7.31-7.41

Acid Base Assessment: ph <90 yr: arterial:

7.35-7.45

Acid base assessement: PaO2: Adult >90 yr

70-90 mm Hg

Acid base assessement: PaO2: Adult <90 yr

80-100 mm Hg

-An increase in bicarbonate causes A -a decrease in bicarbonate causes B

A. the amount of hydrogen ions to decrease and the pH to increase, becoming more alkaline (basic). B. the free hydrogen ion level to increase and the pH to decrease, becoming more acidic.

TABLE 12-1: Acid-Base Regulatory Mechanisms: kidney

Actions to decrease pH: Increased kidney excretion of bicarbonate Increased kidney reabsorption of hydrogen ions Actions to increase pH: Decreased kidney excretion of bicarbonate Decreased kidney reabsorption of hydrogen ions Characteristics: The most powerful regulator of acid-base balance Respond to large or chronic fluctuations in hydrogen ion production or elimination Slowest response (hours to days) Longest duration

NCLEX Examination Challenge 12-3 A client asks why the provider has recommended that he breathe into a paper bag for several minutes when his anxiety disorder causes him to hyperventilate. What is the nurse's best response? A. "Even your exhaled breath still has some oxygen in it, and rebreathing this air ensures that you won't pass out from lack of oxygen." B. "When you breathe fast, you can lose too much carbon dioxide, and rebreathing this air keeps you from becoming dizzy and falling." C. "Rapid breathing can lead to dehydration from excessive fluid loss, and rebreathing this air helps you retain fluid in the form of vapor moisture." D. "Breathing into the bag for several minutes helps you become distracted from whatever is making you anxious and allows you to calm down."

B. "When you breathe fast, you can lose too much carbon dioxide, and rebreathing this air keeps you from becoming dizzy and falling."

S & S of acidosis

Cardiovascular Signs and Symptoms • Delayed electrical conduction: • Ranges from bradycardia to heart block • Tall T waves • Widened QRS complex • Prolonged PR interval • Hypotension • Thready peripheral pulses Central Nervous System Signs and Symptoms • Depressed activity (lethargy, confusion, stupor, coma) Neuromuscular Signs and Symptoms • Hyporeflexia • Skeletal muscle weakness • Flaccid paralysis Respiratory Signs and Symptoms • Kussmaul respirations (in metabolic acidosis with respiratory compensation) • Variable respirations (generally ineffective in respiratory acidosis) Integumentary Signs and Symptoms • Warm, flushed, dry skin in metabolic acidosis • Pale-to-cyanotic and dry skin in respiratory acidosis

S & S of ALKALOSIS

Central Nervous System Signs and Symptoms • Increased activity • Anxiety, irritability, tetany, seizures • Positive Chvostek's sign • Positive Trousseau's sign • Paresthesias Neuromuscular Signs and Symptoms • Hyperreflexia • Muscle cramping and twitching • Skeletal muscle weakness Cardiovascular Signs and Symptoms • Increased heart rate • Normal or low blood pressure • Increased digitalis toxicity Respiratory Signs and Symptoms • Increased rate and depth of ventilation in respiratory alkalosis • Decreased respiratory effort associated with skeletal muscle weakness in metabolic alkalosis

metabolic acidosis: pathology: overproduction of hydrogen ions

Conditions: Excessive oxidation of fatty acids: Diabetic ketoacidosis Starvation Hypermetabolism: Heavy exercise Seizure activity Fever Hypoxia, ischemia Excessive ingestion of acids: Ethanol or methanol intoxication Salicylate intoxication

respiratory alkalosis: pathology: Excessive loss of carbon dioxide

Conditions: Hyperventilation, fear, anxiety Mechanical ventilation Salicylate toxicity High altitudes Shock Early-stage acute pulmonary problems

metabolic acidosis: pathology: underproduction of bicarbonate

Conditions: Kidney failure Pancreatitis Liver failure Dehydration

metabolic akalosis: pathology: increase of base components

Conditions: Oral ingestion of bases: Antacids Parenteral base administration: Blood transfusion Sodium bicarbonate Total parenteral nutrition

metabolic akalosis: pathology: decrease of acid components

Conditions: Prolonged vomiting Nasogastric suctioning Hypercortisolism Hyperaldosteronism Thiazide diuretics

NCLEX Examination Challenge 12-1 Physiological Integrity How are blood hydrogen ion levels and blood carbon dioxide levels related?

D. Blood hydrogen ion levels and blood carbon dioxide levels are directly related so, when the level of one increases, the level of the other increases to the same degree.

NCLEX Examination Challenge 12-2 Physiological Integrity Which blood laboratory values does the nurse need to evaluate to determine whether the client's acidosis has a respiratory origin or a metabolic origin? Select all that apply. A. Calcium B. HCO3− C. Lactic acid (lactate) D. PaCO2 E. PaO2 F. pH G. Potassium

HCO3− PaCO2 PaO2

TABLE 12-1: Acid-Base Regulatory Mechanisms: Respiratory

Increased H+ or increased carbon dioxide: Triggers the brain to increase the rate and depth of breathing, causing more CO2 to be lost and decreasing the H+ concentration Decreased hydrogen ions or decreased carbon dioxide: Inhibits brain stimulation, leading to decreased rate and depth of breathing, causing carbon dioxide to be retained and increasing the hydrogen ion concentration Characteristics: Primarily assist buffering systems when the fluctuation of hydrogen ion concentration is acute

Acid base assessement: lactate: SIGNIFICANCE OF ABNORMAL FINDINGS

Increased: Hypoxia, exercise, insulin infusion, alcoholism, pregnancy Decreased: Fluid overload

Acid base assessement: PaO2: SIGNIFICANCE OF ABNORMAL FINDINGS

Increased: Increased ventilation, oxygen therapy, exercise Decreased: Respiratory depression, high altitude, carbon monoxide poisoning, decreased cardiac output

Acid base assessement: bicarbonate: SIGNIFICANCE OF ABNORMAL FINDINGS

Increased: Metabolic alkalosis, bicarbonate therapy Decreased: Metabolic acidosis, diarrhea, pancreatitis

Acid base assessement PH: SIGNIFICANCE OF ABNORMAL FINDINGS

Increased: Metabolic alkalosis, loss of gastric fluids, decreased potassium intake, diuretic therapy, fever, salicylate toxicity, respiratory alkalosis, hyperventilation Decreased: Metabolic or respiratory acidosis, ketosis, renal failure, starvation, diarrhea, hyperthyroidism

TABLE 12-1: Acid-Base Regulatory Mechanisms: Chemical

Protein buffers (albumin, globulins, hemoglobin) Chemical buffers (bicarbonate, phosphate) Characteristics: -Very rapid response Provide immediate response to changing conditions Can handle relatively small fluctuations in hydrogen ion production during normal metabolic and health conditions

Management: Metabolic alkalosis is an acid-base imbalance caused by either an increase of bases (base excess) or a decrease of acids (acid deficit). Excessive use of bicarbonate-containing antacids, medical treatments such as citrate excesses during massive blood transfusions & IV sodium bicarbonate given to correct acidosis can cause a metabolic alkalosis. The hallmark of a base excess acidosis is

an ABG result with an elevated pH and an elevated bicarbonate level, along with normal oxygen and carbon dioxide levels.

Management: Respiratory alkalosis is usually caused by an excessive loss of CO2 through hyperventilation (rapid respirations). Hyperventilation can also result from direct stimulation of central respiratory centers because of fever, central nervous system lesions, and salicylates. The hallmark of respiratory alkalosis is

an ABG result with an elevated pH coupled with a low carbon dioxide level. Usually the oxygen and bicarbonate levels are normal.

Acid base assessement: bicarbonate

arterial: 21-28 mEq/L (21-28 mmol/L) venous: 24-29 mEq/L (24-29 mmol/L)

Acid base assessement: lactate:

arterial: 3-7 mg/dL 0.3-0.8 mmol venous: 5-20 mg/dL 0.6-2.2 mmol/L

Acid base assessement: PaCO2:

arterial: 35-45 mm Hg venous: 40-50 mm Hg

bases

bind free hydrogen ions in solution and lower the amount of free hydrogen ions in solution. -Strong bases bind hydrogen ions easily (Ex (NaOH sodium hydroxide & ammonia NH3). -Weak bases bind hydrogen ions less readily (Ex bicarbonate HCO3−).

relative alkalosis

the actual amount or strength of bases does not increase; but the amount of the acids decreases, creating an acid deficit. A relative base-excess alkalosis (actual acid deficit) results from an overelimination or underproduction of acids

Management for respiratory acidosis: Pt expected to have a reduction in acidosis signs and symptoms. Indications include:

• Arterial pH approaching 7.35 • PaO2 levels above 90 mm Hg • PaCO2 levels below 45 mm Hg or at least 15 mm Hg below the patient's admission level

KEY POINTS: Safe and Effective Care Environment

• Assess the cardiovascular system first in any patient at risk for acidosis because acidosis can lead to cardiac arrest from the accompanying hyperkalemia • Assess the airway of any patient who has acute respiratory acidosis • Assess heart rate and rhythm at least every 2 hours for any patient with an acid-base imbalance • Monitor the neurologic status at least every 2 hours in patients being treated for a problem with ACID-BASE BALANCE • Assess the ACID-BASE BALANCE of any patient with new-onset muscle weakness • Use fall precautions for any patient with a problem in ACID-BASE BALANCE

KEY POINTS: Psychosocial Integrity

• Assess the gas exchange status of any patient with acute confusion • Perform a mental status assessment in any patient with or at risk for problems of ACID-BASE BALANCE • Assist patients who have anxiety-induced respiratory alkalosis to identify causes of anxiety

KEY POINTS: Physiological Integrity

• Be aware of how the following principles, processes, and mechanisms influence the regulation of ACID-BASE BALANCE: • The normal pH of the body's extracellular fluids (including blood) is 7.35 to 7.45. • The more hydrogen ions present, the more acidic the fluid; the fewer hydrogen ions present, the more alkaline the fluid. • pH values below 7.35 indicate acidosis; pH values above 7.45 indicate alkalosis. • Anything that increases the CO2 level in the blood increases the hydrogen ion content and lowers the pH. • Acids are normally formed in the body as a result of metabolism. • Chemical blood buffers are the immediate way that acid-base imbalances are corrected. • The lungs control the amount of CO2 that is retained or exhaled. • The kidneys regulate the amount of hydrogen and bicarbonate ions that are retained or excreted by the body. • If a lung problem causes retention of carbon dioxide, the healthy kidney compensates by increasing the amount of bicarbonate that is produced and retained. • Acidosis reduces the excitability of cardiovascular muscle, neurons, skeletal muscle, and GI smooth muscle. • Alkalosis increases the sensitivity of excitable tissues, allowing them to over-respond to normal stimuli and respond even without stimulation. • Check the serum potassium level for any patient who has acidosis. • Monitor arterial blood gas (ABG) values to evaluate the effectiveness of therapy for acid-base imbalances.

Maintaining ACID-BASE BALANCE is important because changes from normal pH interfere with many functions. These include

• Changing the shape & reducing the function of hormones & enzymes • Changing the distribution of other electrolytes, causing fluid & electrolyte imbalances • Changing excitable membranes, making the heart, nerves, muscles, & GI tract either less or more active than normal • Decreasing the effectiveness of many drugs

expected outcomes for treating someone with respiratory acidosis

• Maintains adequate gas exchange • Has an arterial pH above 7.2 and closer to 7.35 • Has a PaO2 level above 90 mm Hg or at least 10 mm Hg higher than his or her admission level • Has a PaCO2 levels below 45 mm Hg or at least 15 mm Hg below his or her admission level

KEY POINTS: Health Promotion and Maintenance

• Teach patients to take drugs as prescribed, especially diuretics, antihypertensives, and cardiac drugs • Instruct patients at continuing risk for respiratory acidosis to stop smoking