Cyanide Poisoning

Dizziness, fushing, headache, hypotension, methemoglobinemia, nausea,  syncope,
tachycardia  and vomiting may occur.

Special Precautions-
Methemogloinemia -  both sodium nitrite and amyl nitrite in excessive doses  induce dangerous
methemoglobinemia  and can cause death.
The dosage recommended is not  excessive for adult.
The dose for children should be calculated on a surface area or a  weight basis  with dosage
 adjusted so that excessive methemoglobulin is not found

In adddition oxygen inhalation and transfusion of whole fresh blood  should be considered.

Monitoring- nitrates produce significant vasodilation and rapid administration may result in
hypotension. Hypotenson may  be avoided or lessened by slow administration eg IV push over
at least 5 minutes  or by diluting the dose in 50 to 100ml of 5% dextrose  in water or normal saline.
and beginning infusion as a slow drip then increasing to  the most rapid rate tolerated

Frequently monitor blood pressure during treatment with sodium nitrite

Indication-
Cyanide Poisoning

Dosage-
Instruct an assistant how to break an ampule of amyl nitrate , 1 at a time in an hankerchief  and
hold it infront of a patients mouth for 15 seconds, followed by rest for 15 seconds , Then reapply
until  sodium nitrate can be administered ,This interrupted schedule is important because
continuous use of amyl nitrate may prevent oxygenation.

Discontintinue administeration of amyl nitrate and inject intravenoulsly 300mg ( 10ml of 3% soln )
 of sodium nitrate  at the rate of 2.5 to 5ml/min .
The recommended dose of sodium nitrate for children is 6 to 8ml/m2  ( approx, 0.2ml/kg of body wt.)
but not to exeed 10ml.

Immediately thereafter inject 12.5 g (  50ml of a 25% soln ) of sodium thiosulfate for adults.
The dosage for children 1s 7g/m2 of body surface area, but the dosage should not exceed  12.5g.
The same needle and vein may be used.

If a patient has taken by mouth a gastric lavage should be peformed as soon as possible but
this should not delay the treatment outlined above.
Lavage may be done by a third person, a physician or a nurse.. 

Pharmacology-
Sodium nitrite reacts with hemoglobin to form methemoglobin. The latter removes cyanide ions from
various tissues and couple with them to become cyanmethemoglobin whic has relatively low
toxicity . The function of sodium thiosulfate is to convert cyanide to thiocyanate, probably by an
enzyme known as rhodanese.  The combined mechanism is expressed as

NaNO2 + HCN + O  = HSCN

HCN + methemoglobin = cyanomethemoglobin

NaNS2O3 + HCN + O = HSCN