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Methaemoglobin levels during nitroglycerin infusion for the intraoperative induction of controlled hypotension
Abstract:
The methaemoglobin formation resulting from the intravenous infusion of nitroglycerin, was investigated, intraoperatively, in 46 patients in whom the substance was used to achieve controlled hypotension. The mean infusion rate was 3.50 +/- 0.38 micrograms/kg/min, and the mean duration of the infusion 87 +/- 7.0 min (mean +/- SEM). The concentrations of methaemoglobin were measured prior to, during, and also 60 min after, the infusion of nitroglycerin, using an IL CO Oximeter 282. The control level of the methaemoglobin prior to the start of infusion was 0.6 +/- 0.1%. Nitroglycerin infusion resulted in a slight increase in the level of methaemoglobin of about 1% maximum, which showed no correlation with the total dose of nitroglycerin or the rate of infusion. The mean maximum methaemoglobin level was 0.9 +/- 0.2%. The results suggest that, at average infusion rates of up to 10 micrograms/kg/min, nitroglycerin does not give rise to any clinically significant methaemoblobinaemia.
Insights
Intravenous nitroglycerin infusion for controlled hypotension minimally increased methaemoglobin levels in patients. This study found no clinically significant methaemoglobinaemia at typical infusion rates.
Area of Science:
- Cardiovascular Pharmacology
- Anesthesiology
- Hematology
Background:
- Nitroglycerin is frequently used intraoperatively to induce controlled hypotension.
- Potential adverse effects, such as methaemoglobinaemia, require careful monitoring.
Purpose of the Study:
- To investigate methaemoglobin formation during intravenous nitroglycerin infusion for controlled hypotension.
- To determine if nitroglycerin infusion leads to clinically significant methaemoglobinaemia.
Main Methods:
- Intraoperative investigation in 46 patients receiving intravenous nitroglycerin for controlled hypotension.
- Methaemoglobin concentrations measured pre-infusion, during, and 60 minutes post-infusion using an IL CO Oximeter 282.
- Analysis of infusion rates (mean 3.50 ± 0.38 µg/kg/min) and duration (mean 87 ± 7.0 min).
Main Results:
- Baseline methaemoglobin levels were 0.6 ± 0.1%.
- Nitroglycerin infusion caused a maximum increase of approximately 1% in methaemoglobin levels.
- No correlation observed between methaemoglobin increase, total nitroglycerin dose, or infusion rate.
- Mean maximum methaemoglobin level reached 0.9 ± 0.2%.
Conclusions:
- Intravenous nitroglycerin infusion at average rates up to 10 µg/kg/min does not induce clinically significant methaemoglobinaemia.
- The observed methaemoglobin increase is minimal and not dose-dependent.
- Nitroglycerin can be safely administered for controlled hypotension without significant risk of methaemoglobinaemia.