Former Formula One driver Alex Zanardi. Image Credit: Reuters

Italian race car champion-turned-Paralympic gold medallist Alex Zanardi remained in critical condition a day after crashing his handbike into a truck.

Zanardi is hooked up to an artificial ventilator and has “stable” blood flow while his neurological status “remains serious”, the Santa Maria alle Scotte hospital in Siena said Saturday.

Zanardi was transported by helicopter to the hospital after crashing near the Tuscan town of Pienza during a relay race Friday.

Late Friday, the hospital said Zanardi underwent “a delicate neurosurgery operation” due to “severe cranial trauma”.

The surgery lasted about three hours, after which Zanardi was moved to the intensive care unit.

Zanardi’s wife, Daniela, and his son, Niccolo, are at his bedside.

Local TV at the scene of the crash showed what was apparently Zanardi’s handbike lying on its side at the edge of the road and a large truck pulling a semi-trailer parked ahead.

The 53-year-old Zanardi won two championships in CART in the United States before a brief move to Formula One. He returned to America and was racing in Germany in a CART event in 2001 when both of his legs were severed in a horrific accident the weekend after the September 11 terrorist attacks.

During his recovery, Zanardi designed his own prosthetics and learnt to walk again. He then turned his attention to hand cycling and developed into one of the most accomplished athletes in the world. He won four gold medals and two silvers at the 2012 and 2016 Paralympics, competed in the New York City Marathon and set an Ironman record.