Sodium nitroprusside exposure

Hydrogen cyanide (HCN) is a colorless, rapidly acting, highly poisonous gas or liquid that has an odor of bitter almonds. Most HCN is used as an intermediate at the site of production. Major uses include the manufacture of nylons, plastics, and fumigants. Exposures to HCN may occur in industrial situations as well as from cigarette smoke, combustion products, and naturally occurring cyanide compounds in foods. Sodium nitroprusside (Na2[Fe(CN)5 N0]-2H20), which has been used as an antihypertensive in humans, breaks down into nonionized HCN. 

Thiocyanate in blood 40 (rg/l 00 mL in control nonsmokers 100 (rg/l00 mL in control smokers 420 (ig/100 mL in cyanide-exposed nonsmokers 480 pg/100 mL in cyanide-exposed smokers Maehly and Swensson (1970) Found no relationship between exposure and blood cyanide levels Blood CN—of control nonsmokers ranged from 3.5-10.1 pg/100 mL Blood CN—of control smokers ranged from 2.0-13.0 pg/100 mL Blood CN—of control and cyanide-exposed workers combined ranged from 2.0-15 pg/100 mL (Separate data were not provided for cyanide workers) Aitken et al. (1977) Male and female patients, ages 13-66, presurgery mean 2.7 pg/100 mL Following infusion of sodium nitroprusside 13-205 pg/100 mL Metabolic acidosis at >90 pg/100 mL Nitroprusside doses 12-783 pg/kg (0.8-9.8 pg/kg/min over durations of 15 to 86 min) ... 

Exposure of anhydrous sodium nitroprusside to y-rays at 77 K gave an e.s.r. spectrum consistent with [Fe fCNlgNO]" and NO the reaction mechanism ... 

Poisoning with cyanide may occur in a variety of ways accidental or intentional poisoning with cyanide salts, which are used in industry or in laboratories as a result of exposure to hydrogen cyanide in fires when polyurethane foam burns from sodium nitroprusside, which is used therapeutically as a muscle relaxant and produces cyanide as an intermediate product and from the natural product amygdalin, which is found in apricot stones, for example. 

Exposure of rat primary mixed hippocampal cell cultures to either sodium nitroprusside (SNP 100 xM) or 3-morpholinosydnonimine resulted in both a decrease in cell survival and an increase in free-radical accumulation. These SNP-induced events were blocked by either EGb 761 (10 to 100 pg/ml) or its flavonoid fraction CP 205 (25 pg/ml), as well as by inhibitors of protein kinase C (PKC chelerythrine) and 1-type calcium channels (nitrendipine). In contrast, the terpenoid constituents of EGb 761, known as bilobalide and ginkgolide B, as well as inhibitors of phospholipases A [3-[4-octadecyl)benzoyl]acrylic acid (OBAA)] and C (U-73122), failed to display any significant effects. Moreover, EGb 761 (50 pg/ml), CP 205 (25 pg/ml), and chelerythrine were also able to rescue hippocampal cells preexposed to SNP (up to 1 mM). Finally, EGb 761 (100 g/ml) was shown to block the activation of PKC induced by SNP (100 xM). These data suggest that the protective and rescuing abilities of EGb 761 are not only attributable to the antioxidant properties of its flavonoid constituents but also by their ability to inhibit NO-stimulated PKC activity (Figure 36.1). 

Properties.—An aqueous solution of sodium nitroprusside deposits Prussian blue on exposure to light. In the presence of alkali sulphides— as, for example, ammonium sulphide—it yields a beautiful purple colour, which is very characteristic, and so sensitive that the presence of 0 0000018 gram of hydrogen sulphide in 0 004 c.c. can easily be detected.2 Ammonium hydroxide does not hinder the colour formation, but caustic alkalies destroy it. It gradually fades on standing, in consequence of oxidation of the sulphide to sulphite. The composition of the purple substance is uncertain, but Hofmann 3 suggests the formula Na3[Fe(CN)5(0 N.SNa)], since, by the action of thio-urea, CS(NH2)2, upon sodium nitroprusside, he obtained the complex derivative Na3[Fe(CN)5(0 N.SCNH.NH2)], as a carmine-red powder, closely similar to the substance under discussion.4... 

Sewell et al. (73) evaluated the stability of sodium nitroprusside (0.5 and 1.67 mg/ mL in 5% dextrose) injection packaged in polypropylene syringes and administered by a syringe pump system. When exposed to artificial radiation and window-glass-filtered daylight, the time to 10% decomposition, was about four hours. After 24 hours of exposure, the level of free cyanide exceeded 2mg/L. 

Exposure to NO donors, S-nitrosoglutathione (250 pM) or sodium nitroprusside (500 pM) induced lipid peroxidation in primary cultures of cerebellar granule cells of 7-day-old Wistar rats as indicated by the significant increase in thiobarbituric acid reactive substances (Wei et al. 1999). In cells pre-treated with L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-l-benzopyran-6-yl-hydrogen phosphate] potassium salt (EPC-Kl), superoxide dismutase or NO scavenger haemoglobin, the formation of thiobarbituric acid reactive substances was markedly suppressed. 

Only freshly prepared nitroprusside should be administered, and the container should be covered with lightproof materials, since they are decomposed upon exposure to light. Solutions may be discolored due to the presence of organic and inorganic substances and must not be used. Preservatives, such as sodium bisulfate and hydroxy benzoates, reduce the stability of nitroprusside.124 126... 

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