Acid/Base Disorders 2015

Transcription

1 Objectives Identify acid/base disorders 2. Discuss etiologies for 1 0 acid/base disorders (will not include mixed disorders) 3. Interpret acid/base disorders by interpreting arterial blood gas & serum chemistry values 4. Develop optimal pharmacotherapy plans for acid/base disorders Terms Acidemia ph < Alkalemia ph > Acidosis process causing acidemia 4. Alkalosis process of causing alkalemia 5. Compensation ph normalizes by alterations in a component NOT primarily affected - i.e. 1 0 metabolic disorder respiratory compensatory mechanism 6. Correction ph normalizes by altering the 1 0 component affected - i.e. respiratory = 1 0 cause of acidemia respiratory system Δ occurs ph allowing the respiratory system to correct itself. Arterial blood gas interpretation will be used to determine if compensation vs correction has occurred. Steps to Acid/Base Analysis Assess ABG: Acidemic: ph < 7.35 Alkalemic: ph >7.45 Normal: ph= Determine if disturbance is: Respiratory PC0 2 Metabolic HC If disturbance is respiratory if it s acute or chronic 4. If disturbance is metabolic if it s an anion gap or non-anion gap 5. If disturbance is metabolic if respiratory system is compensating adequately 6. If anion gap exists if other metabolic disturbances exist (mixed disorder) Normal Blood Gas Values (ABGs used most often for Acid/Base Disorders) 5, 6 Generally, arterial blood gases most often assessed for acid-base decisions Mixed venous blood gases assess amount 0 2 utilization by the body ABG nomenclature ph/pac0 2/Pa0 2/HC0 3 if obtained on the blood gas Ventilator parameters important if pt. ventilated 1. Fi0 2 fraction of inspired oxygen 2. Tv title volume 3. Rate administered by ventilator; pt. might breath above this rate 4. PS pressure support 5. PEEP positive end expiratory pressure pc0 2 = carbon dioxide partial pressure Arterial Mixed Venous p mmhg mmhg Sa % % pc mmhg mmhg HC meq meq Respiratory compensation occurs in the kidney takes more time to respond. There is a delay least 12 hrs. for HC0 3 to Δ. Metabolic compensation occurs in the respiratory system. Response is quick w/i few hrs. The brain recognizes problem. Lungs adjust to fix. 1 0 Disorder 1 0 Defect ph Effect Compensation Respiratory acidosis PC0 2 HC0 3(kidney) Respiratory alkalosis PC0 2 HC0 3(kidney) Metabolic acidosis HC0 3 PC0 2 Metabolic alkalosis HC0 3 PC0 2 1 Renal

2 Table below captures analysis parameters, equations, and normal values. You can use this table for Acid/Base analysis or you can answer the questions outlined on pg. 1 of the notes above. Acid/Base Analysis 1. Assess ABG (ph= ) Acidemic: ph < 7.35 Alkalemic: ph > Disturbance Respiratory PC0 2) Metabolic HC0 3) 3. If respiratory Acute Chronic 4. If metabolic anion/non-anion gap Anion gap (AG) Non-anion gap (Think MUD PILES vs HARD UP causes) 5. Anion-Gap, other metabolic disturb. 6. If metabolic, resp. compensation. Yes compensation No compensation Notes 7. Metabolic, compensation, complete? Yes complete No, incomplete 8. Disorder Chloride responsive? Yes Cl - responsive No Cl - non-responsive 1 0 Disorder 1 0 Defect ph Effect Compensation Respiratory acidosis PC0 2 HC0 3 Respiratory alkalosis PC0 2 HC0 3 Metabolic acidosis HC0 3 PC0 2 Metabolic alkalosis HC0 3 PC0 2 Equations 1. Anion Gap (AG) (normal 9-11)(pg. 4) AG = Na+ - (Cl- + HC03-) (determines if problem due to H+ accumulation or HC03 loss) 2. Metabolic Acidosis Compensation, expected PaC02 expected value = [(1.5 x HC03) + 8] (+/- 2) OR PaC02 value? PaC02 expected value = HC03 1 meq PaC mmhg 3. Chloride responsiveness metabolic NaCl responsive, urine Cl < 10 meq/l); (volume related) alkalosis ( HC03) (pg. 6 notes - table) NaCl resistant, urine Cl > 20 meq/l; (volume independent) Arterial Normal Values Mixed Venous Normal Values p mmhg mmhg Sa % % pc mmhg mmhg HC meq meq 2 Renal

3 The algorithm below was provided in 2012 & is a good reference to help you through the thought process of evaluating Acid-Base Disorders. 3 Renal

4 Compensation Mathematical Equations Example: Disorder Primary Defect Compensation Metabolic acidosis HC03 to 20 (4 meq Δ) PCO2 to 36 ( by 4) Disorder Compensation Rate - 7 Metabolic Acidosis HC03 1 meq/l PaC meq Metabolic Alkalosis HC03 1 meq/l PaC mmhg Respiratory Acidosis (acute) 10 mmhg PaC02 HC03 1 meq/l Respiratory Acidosis (chronic) 10 mmhg PaC02 HC03 4 meq/l Respiratory Alkalosis (acute) 10 mmhg PaC02 HC meq/l Respiratory Alkalosis (chronic) 10 mmhg PaC02 HC meq/l ph Δ by Disorder (Helps in deciding acute vs. chronic condition) Degree of serum ph change - 8 Disorder ph Δ Calculation - 8 Respiratory Acidosis (acute) 7.4 (0.08) x [(measured PC02 40)/10] Respiratory Acidosis (chronic) 7.4 (0.03) x [(measured PC02 40)/10] Respiratory Alkalosis (acute) (0.08) x [(40 measured PC02)/10] Respiratory Alkalosis (chronic) (0.03) x [(40 measured PC02)/10] Metabolic acidosis ( HC0 3) 9, 10 Most classic development of another anion present. Anion Gap Metabolic Acidosis - 9 Non-Anion Gap Metabolic Acidosis - 10 In unmeasurable anions (MUD PILES) No in unmeasurable anions (HARD UP) Methyl alcohol Hyper alimentation (not enough HC02 provided) Uremia Acetazolamide Diabetic, alcoholic, starvation ketoacidosis Renal tubular acidosis, renal insufficiency Paraldehyde RTA 1 hypokalemia, urine ph > 5.5* Isoniazid, iron RTA 4 hyperkalemia, urine ph < 5.5 Lactic acidosis Diarrhea, diuretics (drives unmeasurable anion component) Ethyl alcohol Ureteroenterostomy Salicylates Pancreatic fluids * Pt. unable to acidify urine. Metabolic Acidemia S/S - 11 Severe Symptoms 1. Kussmaul hyperventilation (deep, rapid resp. rate); 2. Atrial tachycardia; 3. V-Fib; 4. atrial vasodilation & hypotension; 5. Hyperkalemia; 6. CNS depression more common on the respiratory side 4 Renal

5 Major Adverse Effects of Acidemia 12, 13 Can considerably affect hemodynamics Not good to leave pt. in acidemic state Cardiovascular Symptoms 1. Contractility impairment 2. Arteriolar dilation, venous constriction, centralization of blood volume 3. pulmonary vascular resistance 4. cardiac output, hepatic & renal blood flow 5. Sensitization to reentrant arrhythmias 6. Attenuation of CV responsiveness to catecholamines Hyperventilation with Kussmaul breathing (slide 13) metabolic demands anaerobic metabolism Insulin resistance HYPERkalemia protein degradation Inhibition of metabolism & cell volume regulation Obtundation & coma Metabolic Acidemia Assessment: Anion Gap - 14 If alkalemic there s no anion gap to measure. Only in acidemia is there an anion to measure. 1. Acidemia or alkalemia? 2. Primary disorder: respiratory or metabolic? 3. Anion gap or non-anion gap? (if metabolic) Anion Gap Determines if problem is from accumulation of H+ or loss of HC0 3- Calculating Anion Gap: Anion Gap = Na+ - (Cl- + HC0 3-) Normal Anion Gap 9-11 Metabolic Acidosis Assessment: Compensation - 15 Equation: PaC0 2 = [(1.5 x HC0 3) + 8] +/- 2 OR HC0 3 1 meq/l PaC mmhg Example: If compensation has occurred, what is the expected PaCO 2 if serum HCO 3 = 12? (1.5)(12) + 8 = PaCO 2 = 26 mmhg HC0 3 by 10-14; PaC or Therefore: = 26. Pt has compensated. Metabolic Acidosis: Treatment Goals Restore hemodynamic stability via ph 2. Normalize acid-base 3. Correct underlying electrolyte abnormalities 4. Correct other electrolytes 5. Identify/resolve underlying conditions Metabolic Acidemia: Treatment Options - 17 Chronic conditions Acute conditions 1. Sodium bicarbonate 1. Na Bicarb TX target ph 7.2 LD (meq) = [(V d HC0 3) (Wt.)][(Desired - current HC0 3)] ph > 7.2 & pt. not severely affected NO bicarb. Divide, administer over 3-5 days 2. THAM (consumes H+ ion) 2. Oral alkali replacement Dose (ml) = (1.1)(wt.)(normal HC03- current HC03) MD (meq) = (2 meq/kg)(wt.)/day 5 Renal

6 Case yr. old; insulin dependent diabetic; CC of feeling achy with abdominal discomfort Labs: ABG Chem 7 ph = 7.23 Na+ = 138 PCO2 = 32 K+ = 5.6 P02 = 88 CL- = 106 HC03 = 16 SrCr = 1.1 Arterial Mixed Venous p mmhg mmhg Sa % % pc mmhg mmhg HC meq meq Steps to Acid/Base Analysis Assess ABG: a. Acidemic: ph < 7.35 b. Alkalemic: ph >7.45 c. Normal: ph= Determine if disturbance is: a. Respiratory PC0 2 b. Metabolic HC If disturbance is respiratory if it s acute or chronic 4. If disturbance is metabolic if it s an anion gap or non-anion gap 5. Yes, anion gap = 16: Na-(Cl + HC0 3) 138 ( ) = If disturbance is metabolic if respiratory system is compensating adequately 7. Yes compensating OK; is it complete? Yes. 32. (1.5) (16) + 8 = 32; PCO2 to If anion gap exists if other metabolic disturbances exist (mixed disorder) 9. Yes others exist (16 12) = 20. Additional non-anion gap metabolic acidosis will not elaborate on this. In case 2, we will use a chart for analysis. You can use either format: 1. Answering the above questions OR 2. Doing the same in a chart form. 6 Renal

7 Metabolic Alkalosis Cause ( HC03) - 20 Volume related Volume Independent (NaCl responsive urine Cl < 10 meq/l) (NaCl resistant urine Cl > 20 meq/l) 1. GI disorders: * 1. Excess mineralocorticoid Vomiting Hyperaldosteronism Gastric drains Cushing s Chloride diarrhea 2. Estrogen therapy 2. Diuretics 3. Electrolyte disorders 3. Cystic fibrosis Mg Mild moderate HYPOkalemia K+ severe * GI disorders volume depletion S/S = dry mucous membranes; muscle aches S/S related to underlying cause Severe (ph > 7.6) + heart risk for arrhythmia Metabolic Alkalosis HCO 3-21 S/S Assessment Compensation TX Goal Treatment (TX) Options Treat cause Relate to cause Acute Metabolic Alkalosis Correct Chloride responsive * 1. Volume depletion Expected PaC0 2: cause 1. NS vol. replacement - Muscle aches HC0 3 1 meq/l 2. Acetazolamide** - Dry mucous membranes PaC mmhg 3. HCL - infusion eq. below Severe: ph > HD OR 4. Ammonium Chloride - risk of arrhythmia Chronic Metabolic Alkalosis limited value Expected PaC0 2 Chloride Resistant HC meq/l 1. K+ replacement*** PaC mmHg 2. Mineralocorticoid activity dose PaC0 2 Max Compensation 3. Diuretics = mmhg (key note) - Spironolactone - Amiloride - Triamterene Dose HCL (meq) = (0.5 L/kg (wt. kg) x (desired current HCO3) be careful not to overshoot. * Probably extracellular volume depletion 2 0 to lack of NaCl. ** Acetazolamide use esp. in pts. that are volume limited. Monitor K+ because HYPOkalemia can occur. *** K+ often present with Cl- resistance. Must correct to correct metabolic alkalosis. 7 Renal

8 Case 2-23 Jane, 54 yr. old; hypertension TX with diuretic. S/S: dizziness Physical exam: appears volume depleted Labs: ABG Chem 7 ph 7.46 Na+ 138 PCO2 48 K+ 2.6 PO2 98 Cl - 99 HC03 28 SrCr 1.1 Urine Cl - 57 meq/l If alkalemic there s no anion gap to measure. Only in acidemia is there an anion to measure. Acid/Base Analysis - 24 Notes 1. Assess ABG (ph= ) Acidemic: ph < 7.35 Alkalemic: ph >7.45 Alkalemia Disturbance Respiratory PC0 2) Metabolic HC0 3) Metabolic 3. If respiratory Acute Chronic N/A Not Respiratory 4. If metabolic anion/non-anion gap Anion gap (AG) Non-anion gap N/A pt. alkalemic (Think MUD PILES vs HARD UP causes) 5. Anion-Gap, other metabolic disturb. N/A 6. If metabolic, resp. compensation. Yes compensation No compensation 7. Metabolic, compensation, complete? Yes complete No complete (28-24)(2)+40=48 PaC02 expected = Disorder Chloride responsive? Yes Cl - responsive No Cl - not responsive Urine Cl - 57 meq/l 1 0 Disorder 1 0 Defect ph Effect Compensatory Respiratory acidosis PC0 2 HC0 3 Respiratory alkalosis PC0 2 HC0 3 Metabolic acidosis HC0 3 PC0 2 Metabolic alkalosis HC0 3 PC0 2 Equations 1. Anion Gap (AG) (normal 9-11) AG = Na+ - (Cl- + HC03-) (determines if problem due to H+ accumulation or HC03 loss) 2. Metabolic Acidosis Compensation, expected PaC02 expected value = [(1.5 x HC03) + 8] (+/- 2) OR PaC02 value? PaC02 expected value = HC03 1 meq PaC mmhg 3. Chloride responsiveness metabolic NaCl responsive, urine Cl < 10 meq/l); (volume related) alkalosis ( HC03) NaCl resistant, urine Cl > 20 meq/l; (volume independent) Arterial Mixed Venous p mmhg mmhg Sa02 95 % % pc mmhg mmhg HC meq meq Cause & Treatment: Severe hypokalemia TX: potassium supplementation 8 Renal

9 Respiratory Acidosis ( PCO 2) 25, 26 Acute Causes Chronic Causes Compensation Treatment 1. Drug ingestion 1. Obstructive lung disease 1. Acute Resp. Alkalosis life-threatening 2. CNS alteration 2. Tumor PaC mmhg hypoxia 1. Stroke 3. Pickwickian syndrome HC0 3 1 meq/l 2. ID/correct cause 2. Head injury 4. Brainstem infarct or injury 2. Chronic Resp. Alkalosis 3. Airway obstruction PaC mmhg Pneumonia HC0 3 4 meq/l Pulmonary edema COPD 4. Neuromuscular disease Case yr. old; CC of cough; shortness of breath x 12 hrs. PMH: Severe COPD Labs: ABG Chem 7 ph 7.21 Na+ 135 PCO2 85 K+ 4.0 PO2 47 Cl - 90 HC03 34 HC0 3-3 months ago: 34 Acid/Base Analysis Case 3 Notes 1. Assess ABG (ph= ) Acidemic: ph < 7.35 Alkalemic: ph >7.45 Acidemia Disturbance Respiratory PC0 2) Metabolic HC0 3) Respiratory 3. If respiratory Acute Chronic Chronic 7.4 (0.03)[(85-40)/10]= If metabolic anion/non-anion gap Anion gap (AG) Non-anion gap N/A (Think MUD PILES vs HARD UP causes) 5. Anion-Gap, other metabolic disturb. N/A 6. If metabolic, resp. compensation. Yes compensation No compensation N/A 7. Metabolic, compensation, complete? Yes complete No complete N/A 8. Disorder Chloride responsive? Yes Cl - responsive No Cl - not responsive 1 0 Disorder 1 0 Defect ph Effect Compensatory Respiratory acidosis PC0 2 HC0 3 Respiratory alkalosis PC0 2 HC0 3 Metabolic acidosis HC0 3 PC0 2 Metabolic alkalosis HC0 3 PC0 2 Equations 1. Anion Gap (AG) (normal 9-11) AG = Na+ - (Cl- + HC03-) (determines if problem due to H+ accumulation or HC03 loss) 2. Metabolic Acidosis Compensation, expected PaC02 expected value = [(1.5 x HC03) + 8] (+/- 2) OR PaC02 value? PaC02 expected value = HC03 1 meq PaC mmhg 3. Chloride responsiveness metabolic NaCl responsive, urine Cl < 10 meq/l); (volume related) alkalosis ( HC03) NaCl resistant, urine Cl > 20 meq/l; (volume independent) Arterial Mixed Venous p mmhg mmhg Sa02 95 % % pc mmhg mmhg HC meq meq 9 Renal

10 Respiratory alkalosis ( PCO 2 < 40 mmhg) Respiratory alkalosis ( PCO 2 < 40 mmhg) Causes Compensation Goals TX 1. Pain 1. Acute: 1. ID/Correct cause 1. Consider re-breathing device 2. Anxiety, nervousness PaC mmhg 2. MV adjust settings, dead 3. Pulmonary embolism HC meq/l space 4. Pulmonary fibrosis 2. Chronic 5. Pregnancy PaC mmhg 6. High-altitude HC meq/l Case 4 22 yr. old student studying for exams. Seen in ED for confusion. Brought by friends. Labs: ABG Chem 7 ph 7.49 Na+ 133 PCO2 28 K+ 3.9 PO2 52 Cl HC03 22 SrCr Is pt. acidemic or alkalemic? 2. Is 1 0 disturbance metabolic or respiratory? 3. If respiratory, is it acute or chronic? Acute: (0.8) x (40-28)/10= expected ph = If metabolic, is there an anion gap? N/A 5. If metabolic, has compensation occurred? Is it complete? NA 6. Are there any other metabolic disturbances? N/A 7. Treatment? Help through anxiety; If symptomatic breath through a bag. 10 Renal

11 Acid/Base Analysis Case 4 Notes 1. Assess ABG (ph= ) Acidemic: ph < 7.35 Alkalemic: ph >7.45 Alkalemia Disturbance Respiratory PC0 2) Metabolic HC0 3) Respiratory 3. If respiratory Acute Chronic Acute (0.8)[(40-28)/10]= If metabolic anion/non-anion gap Anion gap (AG) Non-anion gap N/A (Think MUD PILES vs HARD UP causes) 5. Anion-Gap, other metabolic disturb. N/A 6. If metabolic, resp. compensation. Yes compensation No compensation N/A 7. Metabolic, compensation, complete? Yes complete No complete N/A 8. Disorder Chloride responsive? Yes Cl - responsive No Cl - not responsive 1 0 Disorder 1 0 Defect ph Effect Compensatory Respiratory acidosis PC0 2 HC0 3 Respiratory alkalosis PC0 2 HC0 3 Metabolic acidosis HC0 3 PC0 2 Metabolic alkalosis HC0 3 PC0 2 Equations 1. Anion Gap (AG) (normal 9-11) AG = Na+ - (Cl- + HC03-) (determines if problem due to H+ accumulation or HC03 loss) 2. Metabolic Acidosis Compensation, expected PaC02 expected value = [(1.5 x HC03) + 8] (+/- 2) OR PaC02 value? PaC02 expected value = HC03 1 meq PaC mmhg 3. Chloride responsiveness metabolic NaCl responsive, urine Cl < 10 meq/l); (volume related) alkalosis ( HC03) NaCl resistant, urine Cl > 20 meq/l; (volume independent) Arterial Mixed Venous p mmhg mmhg Sa02 95 % % pc mmhg mmhg HC meq meq 11 Renal