A 45-year-old man is admitted to the ICU with acute cyanosis unresponsive to supplemental oxygen. He is intubated, on assist-control ventilation, and receiving a norepinephrine infusion via a central venous catheter for hypotension. Initial arterial blood gas on 60% FiO₂ shows pH 7.28, PaCO₂ 48 mmHg, and PaO₂ 65 mmHg. Co-oximetry reveals a methemoglobin level of 25%. His blood glucose is 85 mg/dL. Methylene blue is being prepared, but administration will be delayed. Which of the following supportive measures is most critical to optimize the efficacy of the impending methylene blue therapy?

A 72-year-old male with severe chronic obstructive pulmonary disease (COPD) and NYHA Class III heart failure is intubated in the MICU on assist-control ventilation with high PEEP. He is receiving a dobutamine infusion for cardiogenic shock and recently underwent bronchoscopy with topical lidocaine. Over the past hour, his skin has developed a bluish discoloration despite an SpO₂ of 88% on 100% FiO₂. Arterial blood gas shows PaO₂ 120 mmHg, PaCO₂ 45 mmHg, pH 7.35, and co-oximetry reveals methemoglobin 18%. Considering his comorbidities and clinical status, which of the following is the MOST critical initial consideration when evaluating definitive treatment for his methemoglobinemia?

A 45-year-old man is admitted to the intensive care unit with severe methemoglobinemia following an accidental dapsone overdose. He is intubated and on mechanical ventilation (FiO2 1.0, SpO2 88%), requiring a norepinephrine infusion at 0.2 mcg/kg/min through a central line to maintain a mean arterial pressure >65 mmHg. Despite maximal oxygen support, his skin and mucous membranes remain cyanotic. Initial labs reveal a methemoglobin level of 25%, a point-of-care glucose of 72 mg/dL, and a pending G6PD status. Which of the following interventions is most critical for supporting the patient’s endogenous methemoglobin reduction pathways?

A 45-year-old man is admitted to the ICU on assist-control ventilation with a norepinephrine infusion through a central line. He was recently started on dapsone. Despite 100% FiO₂, his SpO₂ remains 88%, he appears cyanotic, and blood drawn from his central line is chocolate-brown. What is the most critical immediate step in management?

A 62-year-old man is admitted to the intensive care unit for septic shock. He is mechanically ventilated and requires a continuous norepinephrine infusion via a central line. His current medications include sertraline 100 mg daily for depression. During nursing rounds, his pulse oximetry is noted to be 88% despite an FiO₂ of 1.0, and an arterial blood gas shows a PaO₂ of 120 mmHg. A subsequent co-oximetry confirms a methemoglobin level of 25%. His family reports a history of “anemia after taking certain medications.” Methylene blue is being considered for initial management. Given this patient’s presentation, history, and medication use, which of the following represents the most significant risk associated with methylene blue administration?

A 45-year-old man is admitted to the ICU 4 hours after an accidental ingestion of an unknown oxidizing agent. He is intubated and on assist-control ventilation (tidal volume 6 mL/kg, rate 18, PEEP 5 cm H2O) and receiving norepinephrine 0.1 µg/kg/min via a central line to maintain a MAP ≥ 65 mmHg after 2 L of crystalloid. On 100% FiO2 his ABG shows pH 7.28, PaCO2 48 mmHg, PaO2 85 mmHg. His SpO2 remains 88% despite ventilator adjustments. He appears dusky and cyanotic. Labs: methemoglobin 18% (normal <1%), lactate 4.2 mmol/L (normal <2 mmol/L), hemoglobin 14 g/dL. No history of G6PD deficiency or congenital heart disease. Which of the following is the most appropriate initial management step?

A 45-year-old man is intubated and admitted to the intensive care unit after acute cyanosis unresponsive to oxygen and altered mental status following suspected exposure to an oxidizing agent. He is on assist-control ventilation with an FiO2 of 0.5 and receiving norepinephrine via a central line to maintain a mean arterial pressure of 65 mmHg. Initial arterial blood gas reveals a PaO2 of 120 mmHg, but pulse oximetry shows an SpO2 of 85%. Co-oximetry demonstrates a methemoglobin level of 25%, and his blood appears chocolate-brown. He has no known glucose-6-phosphate dehydrogenase deficiency. Fifteen minutes after receiving methylene blue 1.5 mg/kg IV, his blood glucose is 78 mg/dL. Considering methylene blue’s mechanism of action and this patient’s status, which supportive measure is most critical to optimize the therapeutic response and improve tissue oxygenation?

A 62-year-old man with end-stage renal disease (last hemodialysis 2 days ago) is in the ICU for severe sepsis with acute respiratory distress syndrome on assist-control ventilation (FiO2 0.80) and inhaled nitric oxide, plus a norepinephrine infusion for septic shock. His vital signs are: T 38.2°C, HR 110 /min, BP 85/50 mm Hg, RR 20 /min. On exam he has dusky, cyanotic skin and mucous membranes despite SpO2 98%. Arterial blood gas on FiO2 0.80 shows pH 7.28, PaO2 160 mm Hg, PaCO2 45 mm Hg, and methemoglobin 18%. Which of the following is the MOST appropriate initial management strategy?

A 45-year-old industrial painter is found to have profound cyanosis unresponsive to 100% oxygen after exposure to a high concentration of paint thinner. Arterial blood gas analysis reveals a methemoglobin level of 25% and chocolate-brown–colored blood. His blood glucose is 65 mg/dL. Which of the following is the most appropriate initial supportive intervention before administering methylene blue?

A 62-year-old man in the intensive care unit is noted to have new-onset cyanosis unresponsive to supplemental oxygen. Co-oximetry reveals a methemoglobin level of 28%. His glucose-6-phosphate dehydrogenase status is unknown, with testing pending. He is lethargic but arousable. Which of the following immediate pharmacologic or non-pharmacologic interventions is most appropriate to support oxygen delivery in this patient?