![]() The response is usually rapid the dose may be repeated in one hour, but is frequently not necessary. Methylene blue (MB), given intravenously in a dose of 1 to 2 mg/kg over five minutes provides an artificial electron acceptor for the reduction of methemoglobin via the NADPH-dependent pathway (show figure 2). You will see transient drop in Sats from the blue color of the drug. Methylene blue 1 to 2 mg/kg over 5 minutes (Do not give if G6PD (can give in low doses)) Serves as electron carrier for reduction of MetHb. Place venous blood on piece of paper, in normals, should turn bright red after 15 min, MetHb wont. PaO2 is normal (Sat Gap-on o2, high PO2, low pulse ox Sat) Pulse ox readings stay at 85% while calculated blood gas sat will be normal. Heart disease has low PO2 while MetHb has high PaO2 despite cyanosis In infants, must also be differentiated from cyanotic heart disease. However, even after taking all those factors into consideration – it should be possible to “guesstimate” that the serum COHb level should decrease to 1.5 g/dl in contrast to normal Hb which requires 5 g/dl of deoxygenated form. There were a number of other articles suggesting that the half-life of carboxyhemoglobin could be affected by additional factors such as the duration of CO exposure and the inspired PO2, and that two exponential decay curves could be utilized in calculating the rate of decrease in the serum COHb over time. ![]() They calculated the COHb t1/2 as 74 mins 25 mins with a range of 26 – 148 minutes. ![]() “Carboxyhemoglobin half-life in carbon monoxide-poisoned patients treated with 100% oxygen at atmospheric pressure (Chest 2000 117:801-808) Need cooximetry to detect, normal pulse ox is 100% Room air ½ is 2-7 hrs, O2 90 min, Hyperbaric 23 minutes >25% should get hyperbaric, >10-15% in pregnant women, >15 in CAD Modern cars do not produce though propane burners like tractors, mowers doĢ30-260 times the affinity of oxygen for HbĬarboxyhemoglobin does not carry O2, shifts O2 disassoc curve to left limiting Hb O2 release to tissue, Binds to myglobin limiting muscle O2, Blocks oxidative phosphorylationĬauses NO release which can cause peripheral vasodilation, can knock a pt out If acid, use Bicarb in 1:3 dilution c saline Altered Hbs: Carbon Monoxide (CO) Poisoning Afterdamp is CO2 release after mine explosion of firedampĬhloramine Phosgene (smells like fresh cut hay)
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