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Abstract
Background:
Methaemoglobinaemia refers to the oxidation of ferrous
iron to ferric iron within the haemoglobin molecule,
which occurs following oxidative stresses. The
subsequent impairment in oxygen transport may lead to
progressive hypoxia that is highly dangerous condition
especially in borderline patients like the cardiac
patient.
Objectives: In the
present work, authors explore
the extent of
methaemoglobinaemia in cardiac patients receiving
nitrate therapy.
Methodology: The study
included 970 cardiac patients presented in cardiology
department, Mansoura Specialised Medical Hospital,
Egypt, in the period from February to July 2009.
Patients were taking oral, sublingual, dermal
preparation or a combination of two preparations.
Results: cases of the
study had methemoglobin level 1.1782 ± 0.3476 g/dL with
insignificant difference between males and females.
Methemoglobin showed positive correlation with
carboxyhemogloin and negative correlation with O2
content and O2 saturation. It was significantly higher
in cardiac patient with chest infection, anaemia and
diabetic patients but didn't differ in hepatic or non
hepatic cardiac patients. 3.2% of cardiac patients who
receive more than one nitrate preparation (either oral
and dermal or oral and sublingual therapy) have
methemoglobin level significantly higher than those who
receive single preparation. There is significant
difference in methemoglobin level in cardiac patients
complaining of myocardial infarction “MI”, unstable
Angina, atrial fibrillation “AF” and hypertensive heart
disease “HTN”.
Conclusions: It is
concluded that commonly used dosages of nitrates are
capable of causing elevations of methemoglobin ranged
from 0.9 – 5.3 g/dl. Although the elevation in
methaemoglobin (MetHb) levels was not of routine
clinical significance, there was statistically
significant increase in MetHb levels in cardiac patients
with another pathologic condition as anaemia, diabetes
mellitus or chest infections. Also, it was significantly
higher in patients receiving more than one nitrate
therapy in combination.
Keywords:
Methemoglobinaemia, cardiac toxicity, nitrate therapy |
