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Hyperbaric oxygen therapy may overcome nitric oxide blockage during cyanide intoxication

Purpose: To determine the effects of a blockade of nitric oxide (NO) synthesis on hyperbaric oxygen (HBO2) therapy during cyanide (CN) intoxication.

Methods: 39 anesthetized female Sprague-Dawley rats were exposed to CN intoxication (5.4 mg/kg intra-arterially) with or without previous nitric oxide synthase (NOS) inhibition by L-NG-nitroarginine methyl ester (L-NAME) injection (40 mg/kg intraperitoneally). Subsequently, either HBO2 therapy (284 kPa/90 minutes), normobaric oxygen therapy (100% oxygen/90 minutes) or nothing was administered. Intracerebral microdialysis was used to measure the interstitial brain concentration of lactate, glucose, glycerol and lactate/pyruvate ratios. 

Results: L-NAME potentiated CN intoxication by higher maximum and prolonged lactate (in mM: 0. 5+/- 0.3 vs. 0.7 +/- 0.4, P < 0.005) concentrations compared with solely CN-intoxicated rats. The same trend was found for mean glucose, glycerol and lactate/pyruvate ratio levels.During HBO2 treatment a sustained reduction occurred in mean lactate levels (in mM: 0.5 +/- 0.5 vs. 0.7 +/- 0.4, P < 0.01) regardless of NOS blockade by L-NAME. The same trend was found for mean glucose and glycerol levels.

Conclusion: The results suggest that blocking NOS using L-NAME can worsen acute CN intoxication. HBO2 treatment can partially overcome this block and continue to ameliorate CN intoxication.

DOI: 10.22462/5.6.2017.3