Wk 1 - Acid-Base Balance PDF

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Nursing Praxis Wk 1 Acid-Base Balance Purpose  Maintain a steady balance between acids and bases to achieve homeostasis  Health problems lead to imbalance o Diabetes mellitus o Vomiting and diarrhea o Respiratory conditions pH  

Measure of H+ ion concentration Blood is slightly alkaline pH 7.35 to 7.45 o Below 7.35 is acidosis o Above 7.45 is alkalosis

Regulators of Acid/Base  Metabolic processes produce acids that must be neutralized and excreted  Regulatory mechanisms o Buffers o Respiratory system o Renal system  Buffers: Act chemically to neutralize acids or change strong acids to weak acids o Primary regulators o React immediately o Cannot maintain pH without adequate respiratory and renal function  Respiratory System: Eliminates CO2 o Respiratory centre in medulla controls breathing o Responds within minutes/hours to changes in acid/base o Increased respirations lead to increased CO 2 elimination and decreased CO2 in blood o Normal Paco2 is 35 to 45 mm Hg.  Renal System: eliminates H+ and reabsorbs HCO3o Reabsorption and secretion of electrolytes (e.g., Na +, Cl-) o Responds within hours to days o Normal HCO3- level is 22-26 mmol/L Alterations in Acid-Base Balance  Imbalances occur when compensatory mechanisms fail  Classification of imbalances o Respiratory: Affect carbonic acid concentration o Metabolic: Affect bicarbonate Respiratory Acidosis  Carbonic acid excess caused by o Hypoventilation o Respiratory failure  Compensation o Kidneys conserve HCO3- and secrete H+ into urine pH below 7.35 and a Paco2 above 45 mm Hg. HCO3– is normal Respiratory Alkalosis

Carbonic acid deficit caused by o Hyperventilation o Hypoxemia from acute pulmonary disorders  Compensation o Rarely occurs due to aggressive treatment of causes of hypoxemia pH above 7.45 and a Paco2 below 35 mm Hg. HCO3– is normal. 

Metabolic Acidosis  Base bicarbonate deficit caused by o Ketoacidosis o Lactic acid accumulation (shock) o Severe diarrhea o Kidney disease  Compensatory mechanisms o Increased CO2 excretion by lungs  Kussmaul respiration (deep and rapid) o Kidneys excrete acid  HCO3– below 22 mEq/L and a pH below 7.35. Paco2 is normal Metabolic Alkalosis  Base bicarbonate excess caused by o Prolonged vomiting o Gain of HCO3o Compensatory mechanisms o Decreased respiratory rate to increase plasma CO 2 o Renal excretion of HCO3HCO3– above 26 mEq/L and a pH above 7.45. Paco2 is normal Blood Gas Values  Arterial blood gas (ABG) values provide information about o Acid-base status o Underlying cause of imbalance o Body’s ability to regulate pH o Overall oxygen status  pH: 7.35 to 7.45  Paco2: 35 to 45 mm Hg  HCO3-: 22 to 26 mEq/L. Interpretation of ABGs  Diagnosis in 5 steps o Evaluate pH o Analyze PaCO2 o Analyze HCO3o Determine if CO2 or HCO3- matches the alteration o Decide if the body is attempting to compensate Acid-Base Mnemonic—ROME ?????

Interpretation of ABGs

Normal Values Sea Level

Mile High

Mixed Venous

pH

7.35–7.45

7.35–7.45

7.34–7.37

PaCO2

35–45

35–45

44–46

HCO3

22–26

22–26

24–30

PaO2

80–100

65–75

38–42

SaO2

>95%

>95%

60%–80%

Interpretation of ABGs  Respiratory o ↑ pH, ↓ PaCO2 o ↓ pH, ↑ PaCO2  Metabolic o ↑ pH, ↑ HCO3 o ↓ pH, ↓ HCO3 Interpretation of ABGs  pH 7.36  PaCO2 67 mm Hg  PaO2 47 mm Hg  HCO3 37 mEq/L  What is this? o Respiratory acidosis Interpretation of ABGs  pH 7.18  PaCO2 38 mm Hg  PaO2 70 mm Hg  HCO3- 15 mEq/L  What is this? o Metabolic acidosis Interpretation of ABGs  pH 7.60  PaCO2 30 mm Hg  PaO2 60 mm Hg  HCO3- 22 mEq/L  What is this? o Respiratory alkalosis Interpretation of ABGs  pH 7.58  PaCO2 35 mm Hg  PaO2 75 mm Hg  HCO3- 50 mEq/L  What is this? o Metabolic alkalosis Interpretation of ABGs  pH 7.28  PaCO2 28 mm Hg  PaO2 70 mm Hg  HCO3- 18 mEq/L  What is this? o Metabolic acidosis partial Nursing implications  ABGs  Clinical Assessment!!! o vital signs: check respirations for 1 full minute plus the rate and depth o level of consciousness

o o

fluid balance assessment findings=diagnosis?

Treatment  Metabolic acidosis= fix the underlying cause o E.g., antibx, fluid therapy, surgery  Metabolic alkalosis=fix the underlying cause o E.g., electrolyte imbalance requires fluid/electrolyte replacement  Respiratory acidosis=improve ventilation o E.g., medications, ventilation  Respiratory alkalosis=slow the breathing rate o E.g., anxiolytics, pain control...