Death-row inmate Christa Pike is conscious and speaking six days after surviving a failed execution in Tennessee, according to her lawyers.

Pike was administered two doses of pentobarbital during the September 30 execution, but survived after executioners struggled to establish intravenous access.

Her attorneys say Pike remains hospitalised and is receiving critical medical care, although her long-term prognosis remains unclear.

They say executioners spent about an hour attempting to insert an IV line, using at least seven needles. Her lawyers believe the lethal drug may have entered her body rather than her bloodstream.

Pike was sentenced to death for the 1995 murder of 19-year-old Colleen Slemmer and was due to become the first woman executed in Tennessee in two centuries.

Following the failed execution, Tennessee Governor Bill Lee halted the state's next scheduled execution and ordered an independent review. The state's corrections commissioner, Frank Strada, has also announced his resignation.