The imprecision arising from the application of the Henderson—Hasselbalch relationship to the blood of anaesthetized dogs

Abstract

SUMMARY1. Arterial blood samples were obtained from anaesthetized dogs in which either a respiratory alkalaemia, a respiratory acidaemia or a nonrespiratory acidaemia was produced and from animals in which no deliberate changes in acid-base balance were produced. The samples were analysed for pH, carbon dioxide tension and concentration, oxygen tension and concentration and haematocrit. From these determinations the plasma carbon dioxide concentration, the plasma bicarbonate ion concentration and pK' were calculated.2. The value of pK' lay within the range 5-86-6-27. The temperatures of the animals studied were between 36-75 and 39,250 C but there was no significant relationship between pK' and temperature.3. The values of pK' increased with an alkalaemia and decreased with an acidaemia.4. In addition to the variation of pK' with pH there was a considerable residual scatter of pK' values at any one pH value.5. It was concluded that in these experimental conditions the use of the Henderson-Hasselbalch equation in a form not dealing with activities was unacceptable and could lead to much larger errors than has hitherto been thought.

The effect of light chloralose and pentobarbitone anaesthesia on the acid—base state and oxygenation of arterial blood in dogs

“…From these measurements values were calculated for the plasma bicarbonate ion concentration in each sample using the nomogram of Van Slyke & Sendroy (1928). The details of the calculation are described elsewhere (Linden & Norman, 1971). The 'base excess' value for each sample was derived from the pH, the carbon dioxide tension and an estimate of the haemoglobin concentration, using the alignment nomogram of SiggardAndersen (1963).…”

“…. The calculated value for the plasma bicarbonate ion concentration had an accuracy of within + 1 mm (Linden & Norman, 1971). The values for the pH and the carbon dioxide and oxygen tensions were corrected for any difference in temperature between the electrode system and the rectal temperature at the time of sampling using the factors of Rosenthal (1948) and .…”

The Assessment of Acid-Base Disturbance in Man by the Use of Carbon Dioxide Titration Curves

“…For our purposes to insert points on Fig. 5 it was therefore necessary to recalculate the values for PC02originally published by Goldstein et al (1971), the corrections to the pK' value of the Henderson-Hasselbalch equation proposed by Linden & Norman (1971) being used. Thus it may be concluded that in the groups of subjects so far studied, by us and other workers, the relationship between the non-respiratory pH and the slope of the CO 2 titration curve may be defined by a single equation.…”

“…(1971) must be treated with some caution since they did not measure PC02 but calculated PC02 from measurements of pH and CO2 content with the HendersonHasselbalch equation. The imprecision arising from such a procedure has been described by Linden & Norman (1971). For our purposes to insert points on Fig.…”

Acid‐base changes in paediatric anaesthesia*

“…Throughout the operative period the minute volume was measured so that a constant level of intermittent positive pressure ventilation was maintained and further blood samples taken at [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] min intervals. In the recovery phase blood samples were obtained at convenient times.…”