Acid-Base Imbalances PDF

ACID-BASE BALANCE Tamethia Perkins MS, RRT-NPS, RRT- ACCS RT 3005/6005  ROLE OF THE PCO2/HCO3-/pH IN THE ACID-BASE BALANCE  Respiratory Acid-Base Imbalances As CO2 increases, the PCO2, HCO3-, and H2CO3 increase. Acute ventilatory changes w...

ACID-BASE BALANCE Tamethia Perkins MS, RRT-NPS, RRT- ACCS RT 3005/6005  ROLE OF THE PCO2/HCO3-/pH IN THE ACID-BASE BALANCE  Respiratory Acid-Base Imbalances As CO2 increases, the PCO2, HCO3-, and H2CO3 increase. Acute ventilatory changes will immediately alter the pH. Changes in H2CO3 level play a much more powerful role in affecting the pH than changes in HCO3-. For every H2CO3 molecule increase or decrease, 20 HCO3- must also increase or decrease.  Acute Ventilatory Failure Acute hypoventilation causes increase in PCO2, H2CO3, and HCO3-. Decrease HCO3- to H2CO3 ratio. 24-48 hours, kidneys will retain HCO3- to correct pH. According to the normal blood buffer line, if PaCO2 is 80 mmHg, pH should be 7.2 and HCO3- 30 mEq/L. If pH and HCO3- levels are higher, renal retention of HCO3- has occurred. pH still low= partial compensation. pH normal= complete compensation.  Acute Alveolar Hyperventilation Pain, anxiety. Low PaCO , H CO , and HCO -. 2 2 3 3 HCO3/H2CO3- ratio is larger = >pH.  Chronic Alveolar Hyperventilation and Renal Compensation Hyperventilation >24-48h = low PaCO2 = high pH = kidneys excrete excess HCO3- in the urine.  METABOLIC ACID-BASE IMBALANCES METABOLIC ACIDOSIS Presence of low pH due to presence of acids not related to increased PaCO2 or to renal compensation. Both HCO3- and pH will be lower.  Causes of Metabolic Acidosis Lactic acidosis. End-product of anaerobic metabolism. – Severe acute hypoxemia. Ketoacidosis. Low insulin levels in diabetics cause low intracellular glu levels. Alternative metabolites are ketones. Renal failure. Chronic Metabolic Acidosis and Respiratory Compensation The normal response to metabolic acidosis is increase in RR to decrease PaCO2  Metabolic Alkalosis High pH due to presence of other bases. Common causes: – Hypokalemia: whenever the K is low, kidneys save K by excreting H+= blood base increases.  Chronic Metabolic Alkalosis and Respiratory Compensation Decrease RR = increase PaCO2 = lowers the pH.  BASE EXCESS/DEFICIT Best way to quantify and manage non-respiratory acid-base imbalances.