Led by Dr Yash Kumarasamy, researchers from Aberdeen's Robert Gordon University studied 350 patients having cannulas over six weeks time in the acute medical assessment unit of Aberdeen Royal Infirmary.
In fact, an A and E expert claimed that doctors should resort to cannulas less frequently, and that too for a shorter periods.
Cannulas are hollow plastic tubes with a needle at the tip, costing around 1.70 pounds each.
They are used for giving medication and fluids to people who cannot swallow because they are unconscious or being given nil by mouth. And according to estimates, around 80 percent of hospital patients have them fitted. Drugs may also be more easily absorbed if given this way.
However, using cannulas may lead to a host of complications, including problems with veins (phlebitis), drugs leaking into tissues around the site of the tube, serious infection and blood clots.
In their study, the researchers found that 91 percent of patients had a cannula inserted, but 28 percent of the tubes were never used.
Also, in the records of 71 percent of patients, there wasn't any mention of a cannula being inserted, while in 57 percent there was no documentation of it being removed.
Out of those treated, four patients had developed blood poisoning, which infection control specialists said was likely to be linked to the cannula.
According to the researchers, many UK hospitals follow the practice of inserting an intravenous cannula, the moment the patient is admitted, irrespective of need.
"We would like to see the introduction of a formal procedure under which hospital pharmacists review patients and their medications and make recommendations to the treatment team about whether or not a cannula is needed," the BBC quoted Kumarasamy as saying.
Dr Martin Shalley, a former president of the British Association of Emergency Medicine, also said that doctors were overtly relying on cannula use.
He said that many trusts had policies saying cannulas had to be removed after 72 hours
"It used to be a knee-jerk response to insert a cannula - but we now recognize there's a need to think if fitting one is a benefit for that patient. It's entirely reasonable to look at their use. That's the case in A and E medicine and across acute medicine too," he said.
He also claimed that such over-reliance on cannulas had increased the level of hospital-acquired infections such as MRSA.
The study was presented to the British Pharmaceutical Conference in Manchester.