Tuller's Analysis
- The Physician and His System (Fig. 20)
- Martin A. Tuller, M.D.
- Associate Attending Physician, Long Island Jewish-Queens
Hospital, Jamaica, NY
- analyzes the acid-base status of his patients using the
bicarbonate system and electrolytes
- relationships among variables in the bicarbonate buffer system
- pH can be calculated from [HCO3-] and PaCO2
- [HCO3-] can be calculated from PaCO2 and pH
- PaCO2 can be calculated from [HCO3-] and pH
- Empirical Definitions (Fig. 21)
- normal acid-base status
- pH, PaCO2 and [HCO3-] are all with their normal limits
- pH out of normal range (pH < 7.35 or pH > 7.45)
- an acid-base problem exists
- PaCO2 out of normal range
- (PaCO2 > 45 mm Hg or PaCO2 < 35 mm Hg)
- the lungs are either the cause of or compensation for any
acid-base disturbance
- [HCO3-] out of normal range
- ([HCO3-] < 22 mM or [HCO3-] > 28 mM)
- the kidneys are either the cause of or compensation for any
acid-base disturbance
- Working Assumptions
- five basic assumptions to Tuller's acid-base analysis (Fig. 22)
Fig. 22
- Tuller's fifth assumption is of key importance (Fig. 23)
- compensations can never be complete
(control systems argument)
- how can the physician know the normal pH for each patient
(normal distribution of pHs)?
- Specific Examples
- case A
- data
- pH = 7.35 units
- PaCO2 = 30 mm Hg
- [HCO3-] = 16 mmol/L
- diagnosis
- 1ø metabolic acidosis
- 2ø respiratory alkalosis
- full compensation
- case B
- data
- pH = 7.45 units
- PaCO2 = 30 mm Hg
- [HCO3-] = 20 mmol/L
- diagnosis
- 1ø respiratory alkalosis
- 2ø metabolic acidosis
- full compensation
- summary
- both cases have very similar bicarbonate system values,
but different diagnoses and treatments
- the interpretation hinges on the side of normal each pH value
resides
- the physician should also closely examine each patient's history
for compatibility with diagnosis