AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 5 955-R962, Copyright © 1996 by American Physiological Society
Effect of alkali therapy with NaHCO3 or THAM on cardiac contractility
C. D. Mazer, B. Naser and K. S. Kamel
Department of Anaesthesia, St. Michael's Hospital, University of Toronto, Ontario, Canada.
We examined the impact of alkali therapy on myocardial contractility in a
model of myocardial ischemia in dogs using direct measurements of
myocardial contractile function. Myocardial ischemia in the left anterior
descending (LAD) artery territory was induced using a perfusion circuit
from the internal carotid artery to the LAD artery. Myocardial contractile
function was assessed using sonomicrometry for measurement of percent
systolic shortening (%SS), preload recruitable stroke work (PRSW) slope,
and end-systolic pressure-length relationship (ESPLR) area. Because the
blood flow in LAD artery was diminished by approximately 70%, there was a
significant decrease in O2 delivery and uptake by the ischemic myocardium.
Ischemia led to a significant fall in LAD regional contractile function
with %SS decreasing from 15 +/- 2 to 7 +/- 2%, PRSW slope from 82 +/- 10 to
37 +/- 5 mmHg, and ESPLR area from 121 +/- 2 to 48 +/- 14 mmHg.mm (P <
0.05). In six dogs, the intracoronary administration of NaHCO(3) resulted
in a significant increase in pH in LAD arterial and venous blood. There
was, however, no significant increase in %SS (6 +/- 2), PRSW slope (43 +/-
10 mmHg), or ESPLR area (60 +/- 13 mmHg.mm). Since administration of
NaHCO(3) resulted in a significant increase in PCO2 in LAD arterial and
venous blood, similar experiments were carried out in five dogs, but with
the intracoronary infusion of the amine buffer THAM
[tris(hydroxymethyl)aminomethane (Tris) buffer;
2-amino-2-hydroxyl-1,3-propandiol] instead of NaHCO3. Although
administration of THAM resulted in a significant increase in pH and a
significant decrease in PCO2, in both LAD arterial and venous blood, there
was no significant improvement in any of the parameters used to assess
myocardial contractile function. In conclusion, administration of alkali
(NaHCO3 or THAM) does not enhance the contractile function of the ischemic
myocardium.
