Acid-Base

0.00004 mEq/L or 40 mEq/L

pH=6.1+log[(HCO3)/(0.03 x PCO2)]

6.1-most important for physiologic buffering system, regulated by kidney

6.8, most useful in intracellular

occurs in minutes, max effect 12-24 hours, chemical buffer system is first-line and immediate but limited in scope

responds within hours, max effect within 2-5 days, takes longer and max effect takes longer

24

decreased pH, decreased HCO3, compensation decrease PaCO2

decrease pH, increase in PaCO2, compensate increase in HCO3

increased pH, increased HCO3, compensate by increase PaCO2

increased pH, decreased PaCO2, compensated decrease HCO3

Paco2=[(1.5 x HCO3) +8] +-2

PaCO2=40 + [(HCO3-25) x 0.6 +-2

Acute: pH = 7.4 – [(PaCO2 –40) x 0.008] +- 0.02

Chronic (> 12-24 hrs): pH = 7.4 –[(PaCO2 –40) X 0.003] +_ 0.02

Acute: pH= 7.4 + [(40-PaCO2) x 0.008] +- 0.02

Chronic (> 6-12 hrs): pH= 7.4 + [(40-PaCO2) x 0.003] +- 0.02

7.35-7.45

partial pressure arterial carbon dioxide, 35-45 mmHg

partial pressure arterial oxygen 80-100 mmHg

calculated value 22-26 mEq/L

HCO3 of ABG to HCO3 (or CO2) from blood chemistry panel, or calculated pH to pH from ABG

plus or minus 0.02

plus or minus 2

Calculation: Na - [(Cl + HCO3)]=about 9 (3-12)

↑ Anion Gap (> 12) = accumulation of unmeasured anions, calculate especially for metabolic acidosis but also for others to not miss a toxicology

pH <7.35 HCO3<22

pH <7.35 PaCO2>45

pH >7.45 HCO3>26

pH>7.45 PaCO2<35

“KUSMAL” Æ Ketoacidosis, Uremia, Salicylate, Methanol, Antifreeze, (ethylene glycol), Lactic acidosis

USEDCART-urrethral diversions, small bowel, exogenous chloride, diarrhea, carbonic anhydrase inhibitors, adrenal insufficiency, renal tubular acidosis, topamax

(HCO3- < 8 mEq/L or pH < 7.2)

IV sodium bicarb

Base deficit (mEq) = 0.5 x Kg x (desired HCO3 - observed HCO3- )

10 mg/L and pH NMT 7.20

Tromethamine (THAM)- (150 mEq/500 ml or 0.3 N solution), LOTS of SEs, only use in cardiac transplantation

• ml of THAM=1.1 x Kg x (desired HCO3-observed HCO3)
• OR
• 1-5mM/kg over 1 hr

oral bicarb replacement,administer over 3-5 days to avoid volume overload followed by maintenance 1-3 mEq base/Kg/day if metaboic acidosis persists

• 325 and 650
• each 650 mg tab=7.7 mEq HCO3

citrate metabolized to bicarb by liver

Each ml contains 1 mEq Na+ & 1 mEq HCO3

each ml contains 1 mEq Na, 1 mEq K and 2 mEq HCO3, don't use in CKD

• IV sodium acetate or sodium lactate,
• Metabolized to HCO3
• -
• Substituted for usual chloride salts in TPN

dialysis, if already have access, for severe life-threatening metabolic acidosis

• 1. 0.9% NaCl +/- KCL
• 2. Acetazolamide

• 1. HCL
• 2. NH4Cl
• 3. Arginine
• 4. Dialysis

urine Cl > 20 mEq/L

• 1. Correct underlying problem
• 2. Potassium repletion if K < 3.5

Measure ABG’s & serum K+ every 2-4 hrs depending upon severity

• 1. treat underlying cause
• 2. Replace volume with 0.9% NaCl & add KCL as necessary

• ? Carbonic Anhydrase inhibitor diuretic
• ? Promotes bicarbonate diuresis
• ? Dose: 250 – 375 mg IV or PO qd - bid
• ? Onset w/in 2 hrs; max effect w/in 15 hrs; duration 24 hours

(a) Cl (mEq) deficit = 0.5 x Kg x (desired HCO3 - observed HCO3 ) (b) CL (mEq) deficit = 0.2 x Kg x ( 103 - observed Cl-)

• 1. combines with CO2 and releases HCL following hepatic metabolism to urea
• 2. CNS toxicity limits dose/rate of infusion
• 3. calc Cl deficit and admin 1/2 avoid ammonium overload
• 4. recomm max adult dose=20gm (374 mEq H)/24 hr
• 5. recom max peds dose=16mg/kg IV or 75 mg/kg PO qd
• 6. caution in pts with liver(enchephalopathy) or reanl disease(uremia)

• a.300 ml (10% soln)=142.5 mEq of HCl via hepatic metabolism
• b. infuse 10g/hr
• c. caution: pts with CKD (increase K & BUN)

• a. correct underlying
• b. exogenous cs admin-dec dose
• c. endo cs source-surgery
• d. spironolactone-mc receptor antag
• e. aggressive potassium replacement

• treat underlying
• restore/maintain airway
• oxygen

• Perfusion Abnormalities;
• Airway obstruction
• Aspiration
• COPD
• Neuromuscular Abnormalities;
• Trauma, stroke Brainstem or cervical cord injury Guillain-Barre’ syndrome Myasthenia gravis Status epilepticus Narcotic or sedative overdose Obesity, Poliomyelitis, MS Tumors
• Miscellaneous;
• Mechanical ventilator malfunction Overfeeding with TPN (RQ > 1)

• central stimulation of respiration:
• Anxiety Pain Fever Brain tumors, CVA’s Head trauma Infections Pregnancy Progesterone Catecholamines, Theophylline Salicylates Nicotine Peripheral stimulation of respiration;
• Pulmonary emboli CHF Altitude Asthma Hypotension Pneumonia Interstitial lung damage
• Miscellaneous;
• Hepatic cirrhosis Gram negative sepsis Heat exposure

• identify and treat underlying
• re-breathing device
• adjust mechanical ventilation

• 1. Verify
• Accuracy
• Compare HC03 from ABG’s with HC03 (or CO2) on Chemistry panel or calculate HC03 or pH using modified Henderson-
• Hasselbach Equation
• 2. Identify
• Primary
• Disorder

• pH < 7.35 & HCO3
• - < 22
• 3. Calculate
• Expected
• Compensation
• Winter’s Equation:
• PaCO2 = [(1.5 x HCO3) + 8] ± 2
• 4. Identify
• Mixed
• Disorder
• Observed < Expected →
• Co- Respiratory Alkalosis
• Observed >Expected →
• Co - Respiratory Acidosis
• 5. Identify
• Other
• Metabolic
• Problems
• Calculate Anion Gap
• Na+ - (Cl- + HCO3
• -) = 3-11
• ↑ Anion Gap (>12) →AGMA
• Anion Gap < 12 → NAGMA
• 6. Treat
• Appropriately
• • Bicarb (IV / PO)
• • Na Acetate or Na Lactate
• • THAM
• • Dialysis

• Metabolic Alkalosis
• pH > 7.45 & HCO3
• - > 26
• 3. Calculate
• Expected
• Compensation
• Winter’s Equation:
• PaC02 =
• 40 + [(HC03 – 25) x 0.6] ±2
• 4. Identify
• Mixed
• Disorder
• Observed < Expected →
• Co- Respiratory Alkalosis
• Observed >Expected →
• Co - Respiratory Acidosis
• 5. Identify
• Other
• Metabolic
• Problems

• Calculate Anion Gap
• (suggested)
• Check Urine Chloride
• Urine Cl < 10 mEq/L →
• NaCl Responsive
• Urine Cl > 20 mEq/L →
• NaCl Resistant
• Dependent on above Urine
• Chloride

• Respiratory Acidosis - < 22
• pH < 7.35 & PaCO2 > 45
• 3. Calculate
• Expected
• Compensation
• Acute:
• pH = 7.4 –[ (PaCO2-40) x 0.008]
• Chronic (> 12-24 hrs):
• pH = 7.4 –[ (PaCO2-40) x 0.003]
• 4. Identify
• Mixed
• Disorder

• Observed < Expected →
• Co -Metabolic Acidosis
• Observed > Expected →
• Co -Metabolic Alkalosis
• 5. Identify
• Other
• Metabolic
• Problems
• Calculate Anion Gap
• (suggested)
• Restore/Maintain Airway
• Oxygen

• pH > 7.45 & PaCO2 < 35
• 3. Calculate
• Expected
• Compensation
• Acute:
• pH = 7.4 + [(40- PaCO2) x 0.008]
• Chronic (> 6-12 hrs):
• pH = 7.4 +[ (40- PaCO2) x 0.003]
• 4. Identify
• Mixed
• Disorder
• Observed < Expected →
• Co - Metabolic Acidosis
• Observed > Expected →
• Co - Metabolic Alkalosis
• 5. Identify
• Other
• Metabolic
• Problems
• Calculate Anion Gap
• (suggested)
• Identify
• Other Metabolic Problems
• 6. Treat
• Appropriately
• Rebreathing device
• Adjust mechanical
• ventilation

• a. add NMT 100-250 mEq HCL to 500 ml glass container of D5W or NS
• b. admin thru central line
• c, infuse over 12-24 hours
• d. ABGs and electrolytes q4-8hrs and adjust
• e. DC when pH 7.5