[Effectiveness of preventing hypotension with H1/H2 antagonists before protamine administration].
BACKGROUND
This prospective randomized study was undertaken to evaluate the effects of prophylactic administration of H1/H2 receptor blockers on histamine release and hemodynamic changes after administration of protamine in two groups of patients (n = 20) undergoing elective coronary artery bypass graft surgery.


METHODS
Group 1 (n = 10) patients were pretreated intravenously with 1 mg/kg ranitidine and 0.1 mg/kg dimetinden 15 min before termination of the extracorporeal circulation; group 2 patients (n = 10) received no medication. After termination of the extracorporeal circulation, heparin was neutralized by administration of 350 U/kg protamine, injected during 4 min via a peripheral vein. Hemodynamic measurements were carried out before the administration of protamine and at 1-min intervals up to 10 min after the injection. Before administration of protamine and 2, 4, 6, 8, and 10 min thereafter, plasma histamine levels were measured using central venous blood samples.


RESULTS
In group 1 patients, who were treated prophylactically with H1/H2 receptor blockers, the plasma histamine concentration was 0.21 +/- 0.15 ng/ml (mean +/- SD) and reached a peak value of 0.30 +/- 0.17 ng/ml within 4 min. In group 2 patients, the plasma histamine concentration increased from 0.17 +/- 0.15 to 0.26 +/- 0.24 ng/ml after 10 min. The hemodynamic reactions were comparable in both groups (group 1: decrease in systolic arterial pressure from 118 +/- 16 to 104 +/- 15 mm Hg; group 2: from 111 +/- 19 to 108 +/- 21 mm Hg; differences statistically not significant). The Spearman rank correlation revealed no statistically significant relationship between the slight plasma histamine release and clinically severe decreases of blood pressure that were observed in single patients.


CONCLUSIONS
Histamine release appears unlikely as the mechanism of protamine-induced hypotension. Therefore, general prophylaxis using H1/H2 receptor antagonists does not seem to be justified and cannot be recommended.
Behne
M
M
Zentrum der Anaesthesiologie, und Wiederbelebung, Johann Wolfgang Goethe-Universität, Frankfurt am Main, BRD.
Bremerich
D
D
Schiesser
S
S
Asskali
F
F
D000368:Aged; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001026:Coronary Artery Bypass; D003907:Dexamethasone / Q000008:administration & dosage* / Q000009:adverse effects; D005112:Extracorporeal Circulation; D005260:Female; D006493:Heparin / Q000008:administration & dosage; D006632:Histamine / Q000097:blood; D006636:Histamine Release / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007022:Hypotension / Q000139:chemically induced* / Q000503:physiopathology / Q000517:prevention & control; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D011292:Premedication; D011446:Prospective Studies; D011479:Protamines / Q000008:administration & dosage / Q000009:adverse effects*; D011899:Ranitidine / Q000008:administration & dosage* / Q000009:adverse effects; D011969:Receptors, Histamine H1 / Q000187:drug effects* / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000187:drug effects* / Q000502:physiology
D011479:Protamines; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D003907:Dexamethasone; D006632:Histamine; D011899:Ranitidine; D006493:Heparin