Pain rating scales have become a medical standard for excellent reason: They give doctors important information about changing symptoms and have led to better outcomes in clinical trials. The pain intensity numeric scale (PI-NRS) and patient’s global impression of change (PGIC) contribute to better care but bring a heavy dose of subjectivity to the consulting room. Partly as a result of this subjectivity, doctors may be too quick to prescribe opioid medication when other treatments would be preferable.
Anaesthesiologist Myles Gart proposes an objective way to assess acute pain. The metrics can be remembered with a cheeky mnemonic based on the acronym ORHBP: Opioids Rarely Help Bodily Pain.
Pain often shows in mood and behavior, but so do symptoms unrelated to pain. By ruling out hypoxemia and other conditions, physicians can assess whether a patient’s pain is intolerable. Gart suggests that analgesics should only be given to patients who have hit 10 on the PI-NRS scale.
The link between respiratory rate and pain has not been proven in trials, but Gart believes that intolerable pain causes a rate higher than 20. He proposes that when rates fall below 12, opioid treatments should not be given.
Heart Rate and Blood Pressure
Rehabilitation doctors often use heart rate to assess pain levels, a link that hasn’t yet been established in trials. A small University of Sherbrook study showed that men’s heart rates rise in the presence of pain. Women’s heart rates weren’t affected.
Similarly, pain might cause high blood pressure during the initial stages of chronic, but not acute, pain. However, studies show that pain often brings blood pressure down, making this an unreliable measure.
Pupil size is used by anaesthesiologists to detect pain response. As long as the patient is not sedated and medicated with drugs that cause dilation, pupil response can add another layer of objectivity to pain assessment.
The medical world has been searching for an objective way to evaluate pain for decades. Gart’s proposals could bring doctors a step closer to achieving that goal, though it needs more evidence-based support. In its current form, it comes with the caveat that different objective measures, such as vital signs, mean different things for different patients.