Patients who had a kidney transplant without any kind of pre-operative treatment were not able to be weaned of the anti-rejection drug.

BBC: 'Drug-free' transplant hope

"Every single emergency patient who comes through the door of an NHS hospital should have an individual risk assessment, diagnosis, treatment plan and post-operative care plan prioritised according to need, " he said.

BBC: Emergency surgery patients' lives at risk, say surgeons

He admits not informing patients' GPs about their treatment and failing to perform a pre-operative x-ray and post-operative mammogram on one woman.

BBC: Surgeon 'mistreated women'

Mr Maduro recently said the president was "battling on" and had entered a new stage of treatment, after successfully finishing the post-operative phase.

BBC: Cashier counts bolivar notes in Venezuela

They found that giving statins before surgery reduced the incidence of post-operative atrial fibrillation, suggesting a beneficial effect for patients with a statin treatment when compared to patients without a statin therapy.

FORBES: Preoperative Statins Found to Reduce AF and Length of Stay But Not Mortality