Acid-Base Balance(Acidosis and Alkalosis)

Acid-Base Balance : 

Acid-Base Balance By Sr. Beverly Raway Fall 2001

Normal Acid-Base Balance : 

Normal Acid-Base Balance Normal pH 7.35-7.45 Narrow normal range Compatible with life 6.8 - 8.0 ___/______/___/______/___ 6.8 7.35 7.45 8.0 Acid Alkaline

Maintenance of Balance : 

Maintenance of Balance Balance maintained by: Buffering systems Lungs Kidneys H2CO3…..HCO3

Buffer Systems : 

Buffer Systems Prevent major changes in pH Act as sponges… 3 main systems Bicarbonate-carbonic acid buffer Phosphate buffer Protein buffer H+ H+ H+

Buffer Systems : 

Buffer Systems Bicarbonate buffer - most important Active in ECF and ICF Phosphate buffer Active in intracelluar (ICF) fluid Protein buffer - Largest buffer store Albumins and globulins (ECF) Hemoglobin (ICF)

Bicarbonate-Carbonic Acid : 

Bicarbonate-Carbonic Acid Body’s major buffer Carbonic acid - H2CO3 (Acid) Bicarbonate - HCO3 (Base) 1 20 pH = 7.4 H2CO3 ……………… HCO3 24 mEq/L 1.2 mEq/L

Bicarbonate-Carbonic Acid : 

Bicarbonate-Carbonic Acid Ratio important Not absolute values Person with COPD (CAL) 1 20 7.4 H2CO3 ……………… HCO3 48 mEq/L 2.4 mEq/L

Regulation : 

Regulation Key concept Carbonic anhydrase equation CO2 +H2O H2CO3 H+ + HCO3 Carbon Carbonic Bicarbonate Dioxide Acid (ACID) (BASE)

Slide 9: 

Acid Substance that contains H+ ions that can be released (H2CO3) Carbonic acid releases H+ ions Base Substance that can accept H+ ions (HCO3) Bicarbonate accepts H+ ions

Slide 10: 

As CO2 increases, carbonic acid increases, H+ ions increase pH drops….. becomes more acidic CO2 +H2O H2CO3 H+ + HCO3 Carbonic Bicarbonate Acid CO2 H2CO3 H+ HCO3 (pH Acidic <7.35)

Slide 11: 

As HCO3 increases, H+ decreases pH rises, becomes more alkaline CO2 +H2O H2CO3 H+ + HCO3 Carbonic Bicarbonate Acid CO2 H2CO3 H+ HCO3 (pH Basic >7.45)

Respiratory & Renal Regulation : 

Respiratory & Renal Regulation Lungs control CO2 Kidneys control HCO3 pH = kidneys (bicarbonate) lungs (carbon dioxide)

Respiratory Regulation : 

Respiratory Regulation Mechanisms of control … Hyperventilation -- blow off CO2 Hypoventilation -- retain CO2 Regulation rapid... Seconds to minutes Measured by PaCO2 - Normal 35-45 mm Hg

Renal Regulation : 

Renal Regulation Mechanism of control Excretion or retention of H+ or HCO3 Regulation….. Slow Hours to days to change pH Normal serum HCO3 22-26 mEq/L

Acid-Base Imbalances : 

Acid-Base Imbalances Ratio of 20 to 1 out of balance Acidosis (acidemia) pH falls below 7.35 Increase in blood carbonic acid or Decrease in bicarbonate

Acid-Base Imbalances : 

Acid-Base Imbalances Alkalosis (alkalemia) pH greater than 7.45 Increase in bicarbonate or Decrease in carbonic acid

Acid-Base Imbalances : 

Acid-Base Imbalances Primary cause or origin: Metabolic Changes brought about by systemic alterations (cellular level) Respiratory Changes brought about by respiratory alterations

Acid-Base Imbalances : 

Acid-Base Imbalances Compensation Corrective response of kidneys and/or lungs Compensated Restoration of pH and 20 : 1 ratio Uncompensated Inability to adjust pH or 20 : 1 ratio

Four Basic Types of Imbalance : 

Four Basic Types of Imbalance Respiratory Acidosis Respiratory Alkalosis Metabolic Acidosis Metabolic Alkalosis

Respiratory Acidosis : 

Respiratory Acidosis Carbonic acid excess Exhaling of CO2 inhibited Carbonic acid builds up pH falls below 7.35 Cause = Hypoventilation (see chart) H2CO3

Acid-Base Imbalances : 

Acid-Base Imbalances Normal 1 20 7.4 H2CO3 ……………… HCO3 24 mEq/L 1.2 mEq/L

Respiratory Acidosis : 

Respiratory Acidosis 1 13 7.21 H2CO3 ……………… HCO3 24 mEq/L 1.84 mEq/L

Respiratory Acidosis : 

Respiratory Acidosis Compensation: How? Opposite regulating mechanism Problem = depressed breathing, build up of CO2 in blood Response - Kidney retains HCO3 (Response ….. Slow)

Respiratory Alkalosis : 

Respiratory Alkalosis Carbonic acid deficit Increased exhaling of CO2 Carbonic acid decreases pH rises above 7.45 Cause = hyperventilation (see chart) H2CO3

Acid-Base Imbalances : 

Acid-Base Imbalances Normal 1 20 7.4 H2CO3 ……………… HCO3 24 mEq/L 1.2 mEq/L

Respiratory Alkalosis : 

Respiratory Alkalosis 1 40 7.70 H2CO3 ……………… HCO3 24 mEq/L 0.6 mEq/L

Respiratory Alkalosis : 

Respiratory Alkalosis Compensation: Problem = excess “blowing off” of CO2 Result = decrease in carbonic acid and increase in HCO3 Response: Kidney excretes excess bicarbonate

Metabolic Acidosis : 

Metabolic Acidosis Base-bicarbonate deficit Low pH (< 7.35) Low plasma bicarbonate (base) Cause = relative gain in H+ (lactic acidosis, ketoacidosis) or actual loss of HCO3 (renal failure, diarrhea)

Acid-Base Imbalances : 

Acid-Base Imbalances Normal 1 20 7.4 H2CO3 ……………… HCO3 24 mEq/L 1.2 mEq/L

Metabolic Acidosis : 

Metabolic Acidosis Kidney failure (decrease in bicarbonate) 1 10 7.10 H2CO3 ……………… HCO3 12 mEq/L 1.2 mEq/L

Metabolic Acidosis : 

Metabolic Acidosis Lactic acidosis, keto acidosis (increase acid… no change in bicarbonate) 1 10 7.10 H2CO3 ……………… HCO3 24 mEq/L 2.4 mEq/L

Metabolic Acidosis : 

Metabolic Acidosis Compensation: Problem = low HCO3 (base) or high H+ ion (acid) Response: Lungs hyperventilate Get rid of CO2 (decrease PaCO2 and therefore raise level of HCO3)

Metabolic Alkalosis : 

Metabolic Alkalosis Bicarbonate excess High pH (> 7.45) Loss of H+ ion or gain of HCO3 Most common causes vomiting, gastric suctioning (NG tube) Other: Abuse of antacids, K+ wasting diuretics

Acid-Base Imbalances : 

Acid-Base Imbalances Normal 1 20 7.4 H2CO3 ……………… HCO3 24 mEq/L 1.2 mEq/L

Metabolic Alkalosis : 

Metabolic Alkalosis 1 30 7.58 H2CO3 ……………… HCO3 36 mEq/L 1.2 mEq/L

Metabolic Alkalosis : 

Metabolic Alkalosis Compensation: Problem = too much base Response: Lungs compensate by hypoventilating Retain CO2, increase PaCO2 Increase acid level in blood

Assessing ABGs : 

Assessing ABGs pH 7.35 - 7.45 PaCO2 35 - 45 mmHg HCO3 22 - 26 mEq/L Base Excess -2 - +2 mEq/L PaO2 80 - 100 mm Hg O2 saturation 95 - 100 %

Interpreting ABGs : 

Interpreting ABGs 1. Start with pH Normal? Acidosis? Alkalosis? ___/______/___/______/___ 6.8 7.35 7.45 8.0 Acidosis Alkalosis

Interpreting ABGs : 

Interpreting ABGs 2. Assess PaCO2 (respiratory value) _____/________/______ 35 45 Respiratory Respiratory Alkalosis Acidosis (Note reversal) (See Chart)

Interpreting ABGs : 

Interpreting ABGs 3. Evaluate metabolic indicators Bicarbonate (HCO3) 22-26 and Base excess (-2 to +2)

Interpreting ABGs : 

Interpreting ABGs HCO3 _______/_______/________ 22 26 BE ______/_______/_________ -2 +2 Metabolic Metabolic acidosis alkalosis

Interpreting ABGs : 

Interpreting ABGs 4. Determine level of compensation Has the body tried to readjust the pH? Uncompensated Partly compensated Compensated

Interpreting ABGs : 

Interpreting ABGs Uncompensated pH abnormal (high or low) One component abnormal (high or low CO2 or HCO3) The other component is normal (The component not causing the acid-base imbalance is still normal)

Slide 44: 

Partly compensated pH not normal (but moving toward normal) Both CO2 and HCO3 are outside normal range The component that was normal is changing in order to compensate

Interpreting ABGs : 

Interpreting ABGs Compensated pH normal Other values abnormal in opposite directions One is acidotic the other alkaline

Interpreting ABGs : 

Interpreting ABGs Determine amount of hypoxemia present Normal PaO2 (adults - room air) < 70 years = 80-100 mm Hg 70-79 = 70-100 mm Hg Drops 10 mm Hg for each decade

Interpreting ABGs : 

Interpreting ABGs Hypoxemia = < 70 mm Hg (for adult < 70 years old) Mild = 60-80 mm Hg Moderate = 40-60 mm Hg Severe = < 40 mm Hg

Interpreting ABGs : 

Interpreting ABGs Oxygen saturation (pulse oximetry) 95-100% < 91% confusion < 70% life threatening

Practice Problem : 

Practice Problem 80 year old female with severe pneumonia, fever pH = 7.25 PaCO2 = 55 mm Hg HCO3 = 24 mEq/L PaO2 = 65 mm Hg O2 sat = 80%

Practice Problems : 

Practice Problems What is the problem? Acidosis or alkalosis? Respiratory or metabolic? Compensated or not? Level of hypoxemia? Diagnoses? Interventions?

Tic-Tac-Toe Method : 

Tic-Tac-Toe Method ACID NORMAL ALKALINE _pH__________________________ _PaCO2_______________________ HCO3 Problem: _Respiratory acidosis___ Compensated? _Uncompensated_____

Slide 52: 

Level of hypoxemia? mild to normal…. Diagnosis? Impaired gas exchange R/T lung congestion Dx pneumonia AMB CO2, acid pH, low PaO2, crackles, rapid resp rate and HR etc.

Nursing Management : 

Nursing Management Assessment of breath sounds and respiratory rate Maintain patent airway Oxygen support, ventilation Positioning/turning q 2 hrs… good lung? Pulmonary hygiene POE’s, IV antibiotic

More Practice Problems : 

More Practice Problems Handout and Transparencies Phipps, p. 441 Critical Thinking

Collaborative Management : 

Collaborative Management Identifying clients at risk: Pulmonary, renal, CV disease Fever, sepsis, burns TPN, tube feedings Mechanical ventilation Diabetes (insulin dependent)

Slide 56: 

Vomiting, diarrhea, enteric drainage Elderly (limited ability to compensate)

Assessment : 

Assessment Comprehensive physical assessment (Phipps, p. 437-441) Fluid balance - often disturbed CV function - HR, BP, ECG (decreased K+) Ventilatory status - always changes

Slide 58: 

Breathing Respiratory acidosis - variable, usually shallow/rapid Respiratory alkalosis - increased rate, depth Metabolic acidosis - “air hunger” deep/rapid (Kussmaul) resp

Assessment : 

Assessment CNS function - Acidosis - depressed activity Alkalosis - stimulated Neuromuscular function - Acidosis - weak, flaccid Alkalosis - cramps, twitching

Assessment (cont.) : 

Assessment (cont.) Skin - Respiratory acidosis - pale to cyanotic Metabolic acidosis - warm, dry, pink

Assessment (cont.) : 

Assessment (cont.) Lab values ABGs - interpretation critical, reported first to nursing staff then to doctor Electrolytes - coexisting imbalance almost always present (Na, K+, Ca+) BUN, Creatinine, serum lactate

Diagnoses : 

Diagnoses Ineffective breathing pattern Impaired gas exchange Altered tissue perfusion (cerebral) Activity intolerance Altered thought processes Risk for injury

Goals/Outcomes : 

Goals/Outcomes Client experiences: improved pulmonary ventilation adequate gas exchange and oxygenation of tissues

Outcome Criteria : 

Outcome Criteria ...evidenced by absence of symptoms of respiratory distress (R rate decreases to ____) ...evidenced by ABGs within normal limits (list specifics) by ______ (specify time)

Goals/Outcomes : 

Goals/Outcomes Protection of client from injury: Client experiences no physical injury Confusion decreases…. Oriented x 3 (to person, place, time)

Interventions : 

Interventions Monitor /interpret ABGs Correction of underlying problem Administer O2 as appropriate Positioning, pulmonary hygiene Hydration, appropriate IV solutions, electrolytes (bicarbonate, KCl) Medications (antibiotics, bronchodilators, mucolytics, diuretics) Reorientation Protection of client from injury See Table 16-4 p. 437 and pp. 437-441

Evaluation : 

Evaluation Frequency depends on severity Goals met: ABGs - normal limits /compensation Patent airway Minimization of respiratory effort Increased activity tolerance Oriented x 3

Nursing ManagementRespiratory Acidosis : 

Nursing ManagementRespiratory Acidosis Assessment of breath sounds and respiratory rate Maintain patent airway Oxygen support, ventilation Positioning/turning q 2 hrs Pulmonary hygiene (postural drainage, chest clapping) POE’s

Nursing ManagementRespiratory Alkalosis : 

Nursing ManagementRespiratory Alkalosis Teach how to relieve/ prevent anxiety Calm environment Positioning for comfort Assist with relaxation techniques Reorientation Protection from injury Education re: drug overdose, esp aspirin

Nursing ManagementMetabolic Acidosis : 

Nursing ManagementMetabolic Acidosis Frequent assessment of vital signs esp respiratory rate and rhythm (compensatory mechanisms) Reorientation Safety precautions for confusion For ketoacidosis, sodium bicarbonate IV Education about diabetes

Nursing ManagementMetabolic Alkalosis : 

Nursing ManagementMetabolic Alkalosis Monitoring LOC and confusion Reorientation, protection from harm Monitor serum electrolytes, ABG’s Administer K and Cl replacement as ordered Antiemetics to relieve vomiting Seizure precautions Teaching/monitoring of diuretic therapy Referrals re: eating disorders

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