17 Mar 2017

Improving pain control after surgery

Example of a Visual Analog Scale (VAS) to measure pain intensity
by Anne Crawford

Pain is a subjective and emotional experience that can vary widely between individuals, but being able to measure it effectively is important for clinicians gauging the level of comfort of their patients and for researchers investigating it.

A study conducted by Monash University and Alfred Hospital researchers has led to the development of a simple yet effective measurement technique to help manage pain control and reduction after surgery and trauma.

The multi-disciplinary study overseen by Professor Paul Myles, Head of the Department of Anaesthesia and Perioperative Medicine, set out to test an existing measurement commonly used to test pain reduction after surgery or trauma.

The Visual Analog Scale (VAS) has been widely used to measure pain intensity – clinically and in research – for more than 40 years. The scale measures pain as rated by patients on a scale from 0-100, from none to very severe pain, with 70 points or over generally considered more severe pain and 30 points or under considered mild pain.

It has proved a quick, useful and inexpensive, if one-dimensional, method.

But despite its widespread use, it was unclear how big a difference or improvement in pain reduction after surgery was needed to get good pain control, that is, what minimal change in score would indicate a meaningful change in a patient’s pain status.

“It was always assumed what those numbers had been but no one had actually done a proper study of this, so that was our purpose,” Professor Myles said.

The researchers questioned 219 adult patients with varying degrees of acute postoperative pain who were receiving pain management while recovering from a broad range of operations in surgical wards at the Alfred, Royal Women’s, and Shepparton Hospitals, on two sequential days.

“What we showed very clearly is that if we could reduce the pain score by at least 10 points it would be clinically meaningful for the patients,” Professor Myles said.

“The major conclusion was that if we are to use any pain control method to improve pain control – whether that’s anaesthesia, a nerve block or something like hypnosis – that unless we get at least a 10 point reduction that would be no real improvement,” he said.

The other main finding was that a pain score of 33 points or less signifies acceptable pain control after surgery.

Professor Myles said the findings would be useful to guide future research and for doctors and nurses caring for patients after surgery. The Alfred Hospital has already implemented the measurements as a benchmark standard. Researchers elsewhere had responded quickly to the paper, published online in the prestigious British Journal of Anaesthesia last month, praising its simplicity, methodology and predicting it would be highly cited.

Professor Myles said the study benefited from having a multidisciplinary team bringing different perspectives, including son Daniel Myles, who works in the Monash Department of Psychology and is doing his PhD in psychology, Alfred pain management nurse practitioner Dana Boyd, and anaesthetists from the Alfred and Royal Women’s Hospital.

Reference:
Myles PS, Myles DB, Galagher W, Boyd D2, Chew C, MacDonald N, Dennis A. Measuring acute postoperative pain using the visual analog scale: the minimal clinically important difference and patient acceptable symptom state. Br J Anaesth. 2017 Feb 10. doi: 10.1093/bja/aew466. [Epub ahead of print]

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