![]() COHb and MetHb were used as indexes of CO and NO, and were measured using an arterial blood gas analyzer. The hemodynamic instability with a pressor dose (norepinephrine equivalent) was estimated 1 hour after graft reperfusion. This study investigated the hemodynamic implications of CO and NO levels measured using carboxyhemoglobin (COHb) and methemoglobin (MetHb) during living donor liver transplantation (LDLT). Hemodynamic instability due to liver transplantation may result in poor prognosis of graft. ![]() Like other antidotes, MB has its own adverse effects.Ĭarbon monoxide (CO) and nitrogen oxide (NO) affect vasodilation and cause hemodynamic change. A high dose of MB may induce methemoglobinemia paradoxically and also cause hemolytic anemia. However, the dose should not exceed 7 mg/kg. It can be repeated every 30 minutes to 1 hour. The recommended initial dose of MB is 1 to 2 mg/kg. Patients with comorbidities such as anemia, heart disease, pneumonia, chronic obstructive pulmonary disease, or liver cirrhosis can be candidates for MB therapy with an even lower MetHb level. The indication for MB therapy in a symptomatic patient is a MetHb level >20% and in an asymptomatic patient, a MetHb level >30%. The decision to initiate MB therapy for methemoglobinemia depends on the MetHb level and the symptoms. However, to the exceeding exogenous oxidative stress, the cytochrome b5 MetHb reductase pathway is soon exhausted, and the NADPH MetHb reductase pathway can be activated 4 to 5 times by the exogenous cofactor, MB. ![]() The nicotin amide adenine dinucleotide phosphate (NADPH) MetHb reductase pathway is a minor reducing system of MetHb, and it needs NADPH as a cofactor. The cytochrome b5 MetHb reductase pathway plays a major role in reducing MetHb to hemoglobin. Thus a healthy man can have about 1% of methemoglobinemia. Equilibrium between hemoglobin and MetHb is approximately 99:1. Hemoglobin is oxidized to methemoglobin (MetHb) with the ferric atom, which cannot bind to or carry oxygen. In the human body, hemoglobin is the oxygen-carrying protein including a ferrous atom. ![]() MB is a basic dye, yielding a blue solution. Methylene blue (MB) is an effective antidote for methemoglobinemia.
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