A 73-year-old male patient, smoker of 55 packets of cigarettes a year, with no known drug allergies and no previous treatment. He was admitted for ST-segment elevation acute coronary syndrome (STEMI), complicated 72 hours later by post-infarction angina. A haemodynamic study revealed 90% obstruction in the right coronary artery (RCA), 70% in the anterior descending (AD), 90% in the first diagonal, 70% in the bisector and 70% in the circumflex (CX). Catheterisation showed an ejection fraction of 75% with normal left ventricular end-diastolic pressure. At the medical-surgical session, the patient was accepted for surgery, and treatment was started with carvedilol, captopril, amlodipine, simvastatin and acetylsalicylic acid. After 30 days, a planned myocardial revascularisation was performed using saphenous vein to CD and diagonal vein and mammary artery to DA grafts. During the procedure, an ECC time of 112 minutes, an ischaemia time of 76 minutes and a hypothermia of 29°C was achieved. Anaesthesia was induced with etomidate and cisatracurium and maintained with midazolam (5-7.5 mg/hour), cisatracurium (2.5-5 mg/hour), and remifentanil (0.01-0.02 µg. kg-1. min-1). Standard cardiopulmonary bypass with pulsatile flow was used. Heparin activity was antagonised with protamine. Pump output was normal, and there were no intraoperative incidents.
On admission to the Intensive Care Unit, he showed the following haemodynamic parameters: mean arterial pressure (MAP) of 77 mmHg, with dobutamine perfusion at 4.5 µg kg-1 min-1, heart rate of 80 l/min, pulmonary artery pressure of 31/20 mmHg, PVC of 18 mmHg and PCP of 16 mmHg. Cardiac output (CO) was 6.8 l/min, with a cardiac index (CI) of 3.35 l/min/m2.
Within 2 hours of evolution, the patient developed haemodynamic deterioration, with marked hypotension despite adding noradrenaline perfusion at 0.4 µg kg-1.min-1 and increasing the dose of dobutamine to 8 µg kg-1.min-1. He maintained diuresis, remained afebrile and well adapted to maximal ventilation. Mediastinal drains were scanty. Plain chest X-ray showed no evidence of parenchymal condensation, the Swan-Ganz catheter was in the correct position and there were no changes in the electrocardiogram (ECG).
A total of 2,200 cc of crystalloids and colloids were administered in one hour, i.e. about 30 ml/kg (weight: 70 kg) and noradrenaline perfusion was increased above 0.5 µg kg-1 min-1 without any response. Dobutamine infusion was maintained at the same doses. Sedation was performed with low doses of midazolam. Echocardiographic monitoring ruled out other complications. Core temperature was 35°C and there was no early rewarming, according to the usual pattern. In the presence of data compatible with postoperative vasoplegia refractory to treatment, it was decided to use methylene blue. However, blood cultures were taken and were negative. In addition to requesting the corresponding consents, the relatives were informed of the use of this medication.
The haemodynamic parameters measured with the pulmonary artery catheter before and at various times after methylene blue infusion are shown in table 1. A dramatic haemodynamic response was observed at the time of infusion, which was sustained over time. It allowed withdrawal of noradrenaline, normalised MAT and increased systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR). No changes in arterial blood gases were recorded.

Methylene blue was administered at a dose of 2 mg/kg diluted in 250 cc of 5% glucose saline, to be given over 60 minutes.
No adverse effects of interest were observed, except for urine staining. There was no renal failure, maintaining normal urea and creatinine values and preserved diuresis. Haemoglobin levels were unchanged and there were no alterations in coagulation or liver failure. The level of methaemoglobinaemia was not determined, although this adverse effect, like the others, has been described with the use of doses much higher than those used in our case.
After stabilisation, the patient was extubated 24 hours after admission, and discharge was extended preventively until 72 hours, with no new complications arising. Hospital discharge occurred 11 days later and no late complications were observed.