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Acid Base Balance

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Acid Base Balance

Definition
- Normal physiologic Process
  - Acid production
    - Carbonic and metabolic acid production
      - Increased cellular metabolism increases production
        Carbonic acid converted to: CO2 and H20
        Bicarbonate transported to lung capillaries where CO2 level is low (exhaled)
        Metabolic acids is buffered b4 going to the kidneys for excretion
  - Acid buffering
    - Buffering neutralizes pH despite production of acid. Buffer: weak acid + base in equilibrium in a solution
      - Bicarbonate buffer system: carbonic acid and bicarbonate (base)
        most important buffer in ECF
        Buffer metabolic acids, nto carbonic acid as it's part of the buffer
        Carbonic acid converted into gases, metabolic acid is not
  - Acid excretion
    - Lungs excrete gasous carbonic acid, kidney metabolic acid
      - Metabolic acids can't be converted to gaseous forms, not excreted by lungs
      - Changes in rate and depth of respiration alter amount of excretion of carbonic acid
        Hyperventilation
        increased rate and depth
        Increased excretion of carbonic acid
        Hypoventilation
        Decreased excretion of carbonic acid (retention)
  - Age related differences
    - both have decreased ability to excrete large ammounts of metabolic acids
    - Infants and children
      - More ECF, immature renal system, metabolic rate 2x adult, fluid exchange ration greater than adult.
        More at risk acid base and F&E imbalances
    - Older adults
      - Normal physiologic changes: reduces size and fx of kidney (loss of nephrons), able to manage their role of F&E, acid base balance in normal circumstances. Reduced renal reserve, less able to secrete large acid loads, decreased ability to compensate
- The process of regulating pH, HCO3 concentration, partial pressure of CO2
  - Dynamic interplay fo 3 processes: Acid production, acid buffering, acid secretion
    - Acid production: Generation fo acid thorugh cellular metabolism
    - Acid buffering: For pH of body and body fluids ot be within normal range
    - Acid secretion: Removal of acid from the body
- Scope
  - Acidotic
    - Low pH:<7.35
  - Optimal
    - pH: 7.35-7.45, paCO2, HCO3- normal
  - Alkalotic
    - High pH: >7.45
Variations and Context
- Variations: Acid base imbalance
  - Acidosis
    - too much acid conditions, pH below normal range
    - Respiratory
      - too much carbonic acid
    - Metabolic
  - Alkalosis
    - too little acid, pH too high
    - Respiratory
      - too little carbonic acid
    - Metabolic
      - too little metabolic acids
- Compensations
  - triggers oppository mechanisms, does nto treat pcause but to mainatin ph in normal range
  - Chemical
    - Buffers in blood: bicarbonate, phosphate and proteins
  - Respiratory
    - metabolic imbalances
    - Change in rate and depth
      - Acidosis: increase respirations to off load CO2 (acidic)
        respiratory acidosis
        Alkalosis: Decrease respirations to retain CO2
  - Renal
    - Acidosis: Retain HCO3 a base to increase ph
      - Alkalosis: Excrete HCO3
  - Degrees
    - Uncompensated
      - Body does not try to correct imbalance
    - Partial compensated
      - Body tries to correct imbalance but blood pH is still abnormal despite attempt
    - Fully Compensated
      - Body is correcting imbalance, blood pH is normal, other values remain abnormal until cause is TX
Respiratory and Renal responses
- Stimulus
  - Respiratory acidosis
    - too much carbonic acid
    - Respiratory alkalosis
      - too little carbonic acid
      - Metabolic acidosis
        too much metabolic acid
        Metabolic alkalosis
        too little metabolic acid
        Compensation: Hypoventilation
        Cause: More bicarbonate than kidneys can excrete (too little metabolic acid)
        Correction: Decreased H+ secretion, less NH3 production
        Compensation: Hyperventilation
        Cause: More metabolic acid production than kidneys can excrete
        Correction: Increased H+ secretion, more NH3 production
      - Cause: Hypoventilation
        Correction: Hyperventilation
      - Compensation: Decreased H+ secretion, less NH3 production
    - Cause: Hypoventilation
      - Correction: Hyperventilation
    - Compensation: Increased H+ excretion, more NH3 production
  - Respiratory response
  - Renal response
Risk factors
- all individuals need acid base balance for physiologic fx
- Preterm infants
  - Immature lungs, kidney, thermal regulation and metabolic process. Risk related to weight and gestational age
- Term infants
  - Immature kidney, elevated metabolic rates, large fluid exchange ration
- Older adults
  - Decreased renal reserve d/t/ gradual loss of nephrons, decreased ability to correct and compensate to imbalances.
- Individual risk factors
  - R. acidosis
    - Hypoventilation
      - Asthma
        clinical exacerbtion, severe airway obstruction
        COPD
        decreased carbonic acid secretion d/t/ structual changes in ungs and excessive mucus production
        Obesity
        obesity hypoventilation syndrome- decreased lung expansion
        MS
        acute or chronic respiratory failure
        Causes
        Hypoventilation
        chronchitis, severe asthma, emphysema, pneumonia, pulmonary edema
        Guillain Barre Syndrome
        ineffective breathing- immune system attacks for nerves
        CNS depression
        sedatives, narcotics, CVA
        Neuromuscular disorders
        acute or chronic
        Acute airway obstruction
        foreign body, tumor, reactive airway
        Sickness
        severe pulmonary edem, onstruction, pleural effusion
        Chest cavity problems
        flail chest, pneumothorax, hemothorax
        Chronic lung disease
        obstructive or restrictive
        Central hypoventilation, OSA
        Obstructive Sleep Apnea
  - R. Alkalosis
    - Hyperventilation
      - increased rate an depth of respiration d/t increased secretion of carbonic acid
      - Pyrexia
        increased metabolic demands- hyperpyrexia, rise in body T, fever
        Hypoxia
        Acute pain or anxiety
        Liver disease
        alone or in combo w/ metabolic acidosis
        Causes
        Hyperventilation
        anxiety, pain, fever
        HF
        Central stimulation of resp center
        meningitis, stoke, head trauma
        Lung disease w or w/o hypoxia pneumonia
        Drugs
        salicylates, catecholamines, progesterone
        Mechanical ventilation
        High altitude
        Mechanical ventilation
        3 Categories
        Systemic
        sepsis, ASA, HF, liver failure, endocrine
        Central
        respiratory center, ischemia, CNS trauma
        Lungs
        pneumonia, PE, asthma
  - M. Acidosis
    - Diabetes
      - DKA, lakc insulin produces ketoacidosis faster than kidneys are able t secrete them
      - Drugs
        laxative abuse, spirin OD
        Genetic conditions
        congenital lactic acidosis, 1 or more mutations
        Chronic renal failure
        oliguria renal disease, liver disease, lactic ac
        Cancer
        lactic acidosis, non-Hodgkin's Lymphoma
        Causes
        DKA
        SKA
        starvation ketoacidosis
        AKA
        alcoholic ketoacidosis
        Thyroid storm
        Lactic acidosis
        from tissue anoxia- lack 02
        ASA OD
  - M. Alkalosis
    - Excessive vomiting
      - Overuse od diuretics
        thiazide- high dose
        IV sodium bicarbonate
        excessive admin
        Laxatives
        can prolong diarrhea, loss bicarbonate buffers from the body???
        Causes
        Gain of base
        bicarb
        Ingestion/ infusion of NaHCO3
        Diuretic therapy
        Massive blood transfusion
        Mineral cortical excess syndrome
        Excessive vomiting
        3 Categories
        Chest cavity
        Flail chest, pneumothorax
        Central causes
        sedation, CVA
        Lungs
        pna, asthma
Clinical Manifestations
- Decreased LOC is on a continuum: On one end decreased attention span and drowsiness, on the other stupor and coma. interpretation of assessment findings may be complicated by F&E imbalances
- Common clinical findings
  - Acid base imbalances trigger compensatory mechanisms, timing is important, pH changesimpair cellular and organ fx
  - R.Acidosis
    - Headache, decreased LOC d/t/ hypoventilation, cardiac dysrrhtmias, severe: hypotensions
  - M.Acidosis
    - Decreased LOC, hyperventilation (compensation), N&V, abdominal pain, cardiac dysrrythmias
  - R. Alkalosis
    - Excitation, belligerence, lightheadedness, unusual behaviors, then decreased LOC,
      - severe: perioral and digital paresthesias, carpopedal spasms, tetany, diaphoresis, hyper ventilation (cause), cardiac dysrrtythmias
        paresthesia: burning or prickling sensation carpopedal: spasms in hands and feet
  - M.Alkalosis
    - Excitation the decreased LOC
      - Severe: Perioral and digital paresthesia, carpopedal spasm, hypoventilation (compensate), signs of volume depletion and hypokalemia
- Blood gas findings
  - R. Acidosis
    - pH decreased/ low normal if compensated, increased paCO2, increased HCO3- compensation
  - M.Acidosis
    - pH decreased or low if compensated, paCO2 decreased (compensation), HCO3 decreased
  - R. Alkalosis
    - pH increased, paCO2 increased, HCO3 decreased if compensation
  - M.Alkalosis
    - pH inceased, paCO2 increased (compensation), HCO3 increased
- Time of course of compensatory mechs
  - Acid base imbalances= blood pH not innormal range
    - Overwhelmed buffer, acid excretion mechs restore pH
      - Low acid: kifney and lungs excrete acid
        even if onyl one of the organs wille xcrete the type of acid that is ecvessive, the other organ is compensating
        Depending on time, course and severity
        Compensation: uncompensated, partially compensated, fully compensated
        Respiratory problem= renal compensation which takes a few days to become significant
        Short lived will not be compensated
        Rapid tx will correct the problem b4 renal compensation can occur
        Chronic or episodes- renal compensation may be partial or full
        Respiratory alkalosis from hyperventilation don't last long enough for renal compensation
        Kidney problem= respiratory compensation
        Fast
        Severe disruption will be partially compensated
        Metabolic alkalosis- need for O2 limits use of hypoventilation, full compensation does not occur
        Even if compensation does not return pH to normal, prevents from becoming more abnormal
- Impaired cellular and organ fx
  - Cell fx altered esp. in brain
    - Disorders or carbonic acid cause more neurologic S&S than metabolic
      - CO2 crosses BBB easily, changes CSF pH fast
        Acidosis decreases LOC
        Alkalosis- inital excitation may happen then decrease in LOC if pH keeps increasing
        Dysrythmias (potassium imbalances d/t/ acid base imbalances)
      - Metabolic acid and HCO3 cross BBB w/ difficulty few and slow neurologic S&S
      - Abnormal EC pH can change IC pH, affects enzyme fx- cell dysfx, esp if respiratory
DX tests: ABG
- definitive test fro acid base imbalances
- pH
  - Negative logarithm of H+ concentration, decrease= increase in pH (alkaline), increases= decrease in pH (acidic)
    - H+ arises from dissociation fo acids (metabolic and carbonic acid)
    - Ranges from 1-14, 7 = neutral. Normal: 7.35-7.45 (slightly alkaline), lower in neonates and infants.
      - Academia: pH declines below lower limit (acidotic).Alkalemia- blood pH above normal range (alkalotic).
- paCO2
  - Partial pressure of CO2 in lungs
    - shows how well lungs are excreting carbonic acid (CO2 and H20)
    - Normal: 35-35 mmHg (4.7-6.0 kPa) in adults, lower in infants
      - Increased paCO2= accumulation of CO2 in blood, too much acid d/t/ primary or compensatory hyporventilation
        Decreased paCO2= decreased CO2 in blood, too little acid, d/t/ primary or compensatory hyperventilation
- HCO3
  - Shows how well kidneys are excreting metabolic acid.
    - Adult range: 22-26 mmol/L or mEq, lower in infants
      - Increased HCO3= too little metabolic acid, decreased HCO3= too much metabolic acid
- Base Excess
  - Range: -2 - +2 mmol/L
  - How well the buffer is managing metabolic acid.
    - Less than -2mmol/L (negative base excess) = too much metabolic acid, greater than +2mmol/L = too little.
- Anion gap
- Stewart strong ion difference
Clinical Management
- Nursing Interventioms
  - acid base disbalance always results from other conditions  (and F&E imbalances) that's why assessment of acid base are performed in the context of other conditions
  - Ongoing assessment
  - Safety measures
  - Comfort measures
  - Support compensatory mechanisms
  - Collaborative internvetions
    - Tx underlying cause pH adjustment
    - Untx acid base imbalance can be fatal
      - Most medical and nursing mngmt is directed towards disease process, instead of disrupted acid base balance
        Respiratory support
        disbalances cused by underlying respiratory condition
        Too much or too little acid: airway mangmt, O2 therapy
        Hyperventilation leads to R.alklosis
        too little acid
        TX: underlying factors that drive hyperventilation
        hypoxia, acute pain, anorexia
        Compensatory hyperventilation (d/t/ metabolic acidosis) should be allowed to continue while tx M.acidosis
        F&E support
        caused by underlyign metabolic condition
        DKA: fluids and insulin
        tx problem and normalize pH
        Oliguria renal disease: Dialysis
        accumulates too much metabolic acid, dialysis tx multiple aspects of conidtion, restores pH to normal
        Danger: very low pH, may adjust pH
        Common: NaHCO3
        CONTROVERSIAL
        May cause ECV excess or hypernatremia which delay renal excretion of ketoacidosis, may lead to metabolic alkalosis
        Monitor S&S of complications and acid base balance
  - Monitory therapy complications
  - Patient teaching
    - teach culturally appropriate ways to prevent acid base balance disruptions.
    - Recognize early problems
      - know when to seek help w/ chronic conditions
    - Mngmt of underlying conditions
  - Prevention
    - Primary
      - Prevention of major risk factors
        ex: prevent respiratory disease to prevent carbonic acid accumulation
    - Secondary
      - screening
      - Screening not performed in the general pop
  - Individual interventions
    - Provide safety and comfort
      - Safety high priority w/ decreased LOC
        Interventions to promote compensation mechanisms:
        ex: PT hyperventilating for metabolic acidosis, proper positioning for chest expansion, frequent oral care- prevent drying and cracking of lips
        HX + Assessment of risk factors
        Non specific signs: decreased LOC
        Consider presenting symptoms in the context of other conditions
        HX: respiratory, renal problems or other conditions that can cause disbalances
        Recent hx of vomiting (metabolic alkalosis), diarrhea (metabolic acidosis),
        Use of heartburn/ indigestions meds (metabolic alkalosis d/t baking soda/ NaHCO3
        Recent attempt to lose weight and methods
        high fat, low carb diet, fasting predisposes to ketoacidosis
        Medications, dietary supplements, alcohol
        Exam findings
        Unless severe, S&S of acid base imbalances overshadowed by manifestations of underlying cause
        Type B COPD (chronic bronchitis)
        Dyspnea, excessive mucus production (more obvious than mild drowsiness d/t/ partially compensated R. acidosis)
        Severe acute asthma: chest tightness, coughing, wheezing, us of accessory muscles, low O2 overshadow manifestations of acute respiratory acidosis.
        End stage renal failure (chronic oliguric condition)
        Manifestations predominate over S&S of metabolic acidosis, that may occur b/w dialysis, unless severe
        In rapid changes of pH (like ketoacidosis)
        Dramatic change in LOC can overshadow s&s of underlying conditions
        DKA:polyuria, polydipsia, polyphagia and weight loss of hyperglycemia b4 onset of ketoacidosis.
        Manifestations often realized in retrospective, after abdominal pain and decreased LOC from ketoacidosis have become focus and metabolic acidosis is resolved
        Interrelated concepts
        F&E related to A-B balance, change in one affects the other
        Gas exchange, perfusion, nutrition
        Normal acid production
        Alterations: ischemia, hypoxia, starvation, high fat low carb diet can disrupt process
        Elimination: acid excretion, oliguria and diarrhea can disrupt balance
        Altered cognition d/t/ imbalances
           ´Understanding acid-base balance is a core concept that can help you think critically about your patients and recognize how imbalances can impact their overall wellbeing.   ´The nurse role is to provide safety and comfort for people who have disrupted acid-base balance.

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Beschreibung: NURS 224 Mindmap am Acid Base Balance, erstellt von Mag Mag am 24/03/2020.
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Acid Base Balance

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