Murray played on at the neighbouring Margaret Court Arena apparently unaware of the drama unfolding elsewhere and was far from his fluent best as he sealed a 6-2 3-6 6-2 6-2 victory over Portugal's Joao Sousa.
When Murray completed victory, Sears was undergoing tests with a cardiologist but Jamie Murray told Press Association Sport the 58-year-old was "conscious, talking and sitting up".
At the end of the contest, Murray departed the arena immediately, rather than doing a customary on-court interview. It was also announced he would not be attending a post-match press conference.
However, in a statement later provided to the media, Murray said he found it tough against the Portuguese No.1 and admitted he had to keep fighting for the win.
"I thought I struggled," he said. "At the beginning I think he was extremely aggressive, very intense.
"He was getting into positions to dictate a lot of points with his forehand. Once I started to hit the ball a little bit cleaner towards the end of the match I was able to get him in his backhand corner and dictate more of the points.
"I just tried to keep fighting. At the end I was actually hitting the ball well and felt better at the end. It was good to get through that one."
The Briton had struggled for his usual rhythm during the match as he consistently mistimed his forehand and was regularly forced to rely on his second serve.
Sousa, however, was unable to capitalise as he carved out a number of early opportunities but each time watched Murray momentarily find his best to survive.
A scintillating cross-court forehand from the Scot saved a break point in the third game and then two irretrievable serves diverted another in the fifth as Sousa failed to make his strong start count.
It proved costly as Murray found his groove at 3-2, brilliantly hunting down and then flicking away a Sousa drop-shot to break the Portugese and move two games clear.
Frustrated, Sousa wavered from his baseline game, which suited Murray, who picked him off with ease and broke again to clinch the opening set.
The score, however, flattered the British No.1 and it was little surprise that Sousa, composing himself again, nicked the first break in the second when a Murray backhand flew long.
Sousa had a foothold and as Murray huffed and puffed, his opponent broke again to seal the set and level up.
When Murray appears most exasperated he often produces his most inspired tennis and that was the case in the third set, as he used his superior touch, craft and speed to outmanoeuvre Sousa.
Two breaks of serve put the Briton back in front and he carried his momentum into the fourth with another break at 2-2.
Sousa was suddenly on the back foot and he never looked like recovering as Murray raced away, breaking again at 5-2 before sealing victory in two hours and 38 minutes.