Acid-Base Disorders

Question 1

Metabolic acidosis: definition

Answer 1

pH < 7.35
HCO3- : usually < 22
Compensation: Decreased pCO2

Normal AG metabolic acidosis: AG < 12, indicates primary HCO3- loss or H+ plus Cl- gain

High AG metabolic acidosis, AG > 15, indicates addition to serum of non Cl- acid anion (lactate)

Question 2

Metabolic alkalosis: definition

Answer 2

pH > 7.45
HCO3- : usually > 28
Compensation: Increased pCO2

Question 3

Respiratory acidosis: definition

Answer 3

pH < 7.35
increased pCO2 > 45
Compensation: increased HCO3-

Question 4

Respiratory alkalosis: definition

Answer 4

pH > 7.45
pCO2 < 36
Compensation: decreased HCO3-

Question 5

Metabolic acidosis: etiologies

Answer 5

**Normal AG metabolic acidosis**
#GI HCO3- loss: diarrhea, pancreatic drainage.
#Insufficient renal acid excretion, renal tubule acidosis, mild/mod kidney failure (GFR >20-30)
#HCL intake of acidifying salts

**High AG metabolic acidosis**
#Endogenous or exogenous acids
#LACTIC ACIDOSIS: sepsis, hypoxia, circulatory shock, DKA
#ETOH ketoacidosis
#Advanced renal insuff (GFR <15-20)
#Salicylate poisoning, methanol, ethylene glycol

Question 6

Metabolic alkalosis: etiologies

Answer 6

#GI hydrogen loss: vomiting, NG aspiration
#Renal hydrogen loss: 
1) 2º Hyperaldosteronism from volume contraction: diuretic therapy, vomiting, NG aspiration, K+ depletion w/ or wo/ MG++ deficiency. 


2) Hyperaldosteronism w/ normal or expanded volume- primary aldosteronism, Cushing’s, renal artery stenosis
#Bicarb gains (think renal insuff): NaHCO3 admin, massive transfusion of  citrate (PRBC, FFP) or acetate (TPN, dialysis solutions)

Question 7

Respiratory acidosis: etiologies

Answer 7

**Acute Hypoventilation**
#CNS depression (opioids, sedatives)
#CNS injury (brain stem injury, CVA)
#Neuromuscular disease (MG, Guillain Barre, poliomyelitis)
#Airway obstruction (mucus/foreign body, sever bronchospasm of status asthmaticus, bronchitis, emphysema)
#Chest disorders (flail chest, pneumothorax, kyphoscoliosis

Chronic Hypoventilation
COPD, obesity (Pickwickian syndrome), diaphragmatic weakness/paralysis

Question 8

Respiratory alkalosis: etiologies

Answer 8

Acute Hyperventilation
CNS disorders (anxiety, pain, fever, head trauma, salicylates)

Pulmonary disease: ⇓ lung compliance (pulm edema, CHF, PNA, PE, asthma, sepsis, acute salicylate toxicity)

Chronic Hyperventilation
residence at high altitude, pregnancy, chronic hepatic insuff/cirrhosis

Question 9

Metabolic acidosis: signs & symptoms

Answer 9

#Anorexia 
#Nausea
#Weakness
#Lethargy to coma
#Signs of underlying disorder
#Kussmaul breathing
#Hypotension

Question 10

Metabolic alkalosis: signs & symptoms

Answer 10

#CNS symptoms: HA

#Lethargy to coma
#Tetany or seizure r/t decreased Ca++
#Postural hypotension or tachycardia
#Resp. depression
#Signs of primary disorder

Question 11

Respiratory acidosis: signs & symptoms

Answer 11

**ACUTE**
#Decreased LOC to coma
#HA, anxiety, confusion, hallucinations
#Dyspnea
#BP ⇑ 
#papilledema
#tremor
#abnormal DTR’s

**CHRONIC**
#sleep disturbances
#memory loss
#impaired coordination, tremor
#signs of cor pulmonale 
#signs of COPD

Question 12

Respiratory alkalosis: signs & symptoms

Answer 12

**ACUTE**
#light headed
#confusion
#paresthesias (esp around mouth) 
#chest tightness
#muscle cramps
#Hyperactive DTR
#Carpopedal spasm (tetany, flexed wrist/ankle with hyperextended digits

**CHRONIC**
#Generally none

Question 13

Treatment for metabolic acidosis

Answer 13

TREAT PRIMARY DISORDER!

# NaHCO3 therapy via IV: controversial, & rarely indicated for pH >7.10!  DKA: not required or recommended. Lactic acidosis: may INCREASE lactate levels, so screw that!
#NaHCO3 injection: very hypertonic, limit to 1-2 ampules,
#NaHCO3 infusion, isotonic, use formula.
0.5 X kg X (20-serum HCO3-) = required HCO3-

Question 14

Treatment for metabolic alkalosis

Answer 14

#Volume depletion- IV NS at 100-150/hr
#KCl replacement
#Diamox 250-500 mg IV or PO BID, especially in volume expanded states
#Aldactone 25-50 mg PO TID/QID or Inspra in aldosterone excess states with hypokalemia
#HCl infusion- 0.1 M solution, in central vein, SLOW, total infusion approx. 0.2 X kg X (HCO3- - desired HCO3-), potentially hazardous
#Hemodialysis agent low HCO3-  bath

Question 15

Treatment for respiratory acidosis

Answer 15

**ACUTE**
#Reverse CNS depression (Narcan, Romazicon)
#Reverse airway obstruction (bronchodilator, mechanical extraction of secretions or foreign body, assist ventilation with CPAP or intubation)

**CHRONIC**
#avoid respiratory depression
#nocturnal CPAP
#vigorous treatment of underlying disorder

Question 16

Treatment for respiratory alkalosis

Answer 16

**ACUTE**
#Treat underlying cause
#Reassure 
#Rebreathing into paper bag for hyperventilation

**CHRONIC**
#generally none required