Pain medicine basics: Overview

Neuromodulation: Technology at the Neural Interface is the preeminent journal in the area of neuromodulation, providing our readership with the state of the art clinical, translational and basic science research in our field and representing the needs of the broad neuromodulation community. For clinicians, engineers, scientists and members of the biotechnology industry alike, Neuromodulation provides timely and rigorously peer reviewed articles on the technology, science and clinical application of devices that interface with the nervous system to treat disease and improve function. Neuromodulation covers an ever expanding field including pain, headache, movement disorders, spasticity, paralysis, psychiatric disorders, epilepsy, sensory deprivation, gastric dysfunction, obesity and incontinence.

Regional Anesthesia & Pain Medicine, the official publication of the American Society of Regional Anesthesia and Pain Medicine (ASRA Pain Medicine), is a monthly journal that publishes peer-reviewed scientific and clinical studies to advance the understanding and clinical application of regional techniques for surgical anesthesia and postoperative analgesia. Coverage includes intraoperative regional techniques, perioperative pain, chronic pain, obstetric anesthesia, paediatric anesthesia, outcome studies, and complications.

Abstract
Objective: Complex Regional Pain Syndrome (CRPS) presents significant diagnostic challenges due to its diverse clinical presentation. This study aims to describe the diagnostic trajectory of patients labeled with CRPS, focusing on referral patterns, application of the Budapest criteria, and accuracy of CRPS diagnosis.

Methods: A retrospective study was conducted of 53 patients treated for CRPS at a peripheral nerve clinic within a tertiary care center (2020-2024). Patient demographics, referral patterns, events leading to CRPS diagnosis, and diagnostic tests were analyzed. Three clinicians (two plastic surgeons, one pain medicine specialist) retrospectively assessed the validity of CRPS diagnoses using the Budapest criteria. Inter-rater reliability (IRR) for CRPS presence and type was calculated using Cohen's kappa (κ).

Results: Among the 53 patients, the median time from the first mention of CRPS to referral to the nerve clinic was 1.3 years (IQR:0.4-3.6). The Budapest criteria had been assessed in 26% of patients pre-evaluation. In 33% of patients labeled with CRPS type I, an inciting nerve injury was identified. Following retrospective assessment, 42% of patients were determined to have CRPS by all raters, 26% were determined not to have CRPS, and 32% showed inconsistent agreement. The IRR for CRPS diagnosis and type ranged from minimal to moderate (κ=0.32-0.72).

Discussion: Our findings highlight variability in the application of the Budapest criteria for CRPS diagnosis, as well as inconsistencies in its retrospective application. Potentially treatable peripheral nerve injuries should be addressed prior to CRPS diagnosis. These findings may help improve early diagnostic assessment in patients with chronic pain.

Abstract
Introduction: Non-traumatic back pain commonly leads people to seek health care from paramedics via triple-zero (emergency phone number in Australia), yet the management approaches by providers of ambulance services remain unclear.

Study objectives: This study aims to investigate paramedic management of non-traumatic back pain in New South Wales (NSW), Australia, including the call characteristics, provisional diagnoses, and the clinical care being delivered by paramedics.

Methods: This study is a retrospective analysis of NSW Ambulance computer-aided dispatch and electronic medical records from January 1, 2017 through December 31, 2022. Adults who sought ambulance service with a chief complaint of back pain, were triaged as non-traumatic back pain, and subsequently received treatment by paramedics were included. Multivariable logistic regression models were used to explore factors associated with primary outcomes; ambulance transport, opioid use, and use of medication combinations were reported as odds ratios (ORs).

Results: There were 73,128 calls to NSW Ambulance with a chief complaint of back pain that were triaged as non-traumatic back pain. Of these, 54,444 (74.4%) were diagnosed with spinal pain, of which 52,825 (97.1%) were categorized by the paramedic as back or neck pain, 1,573 (2.9%) as lumbar radicular pain, and 46 (0.1%) as serious spinal pathology. Eight out of ten patients with spinal pain were transported to emergency departments. The medicine most administered by a paramedic was an opioid (37.4% of patients with spinal pain). Older patients (OR = 1.36; 95% CI, 1.30 to 1.44) were more likely to be transported to an emergency department. Patients with moderate (OR = 4.39; 95% CI, 4.00 to 4.84) and severe pain (OR = 18.90; 95% CI, 17.18 to 20.79) were more likely to be administered an opioid.

Conclusions: Paramedic management of non-traumatic back pain in NSW typically results in the administration of an opioid and transport to an emergency department.

Abstract
Ketamine is an N-methyl-d-aspartate receptor antagonist approved for use in anaesthesia, with analgesic properties. Despite publication of numerous trials and expert guidelines on its use for pain management, administration of ketamine as part of multimodal perioperative analgesia remains 'off-label'. We conducted an online, prospective survey of ANZCA Fellows, exploring current prescribing practices of intravenous ketamine for perioperative analgesia. We surveyed 2000 Fellows and received 806 responses. The factors mostly likely to influence their administration of perioperative ketamine included pre-existing chronic pain, and heavy or multiple opioid use by patients preoperatively. Amongst respondents, less senior anaesthetists and those working in public hospitals were more likely to administer intraoperative ketamine. The surgical procedures most likely to result in ketamine administration intraoperatively were open pelvic/abdominal, thoracic and major spinal surgery, where ketamine administration was likely practice for the majority of respondents, with typical loading doses that ranged widely. The commonest choices of intraoperative loading dose were between 0.2 mg kg-1 and 0.6 mg kg-1. The commonest choice of intraoperative and postoperative infusion rate was in the range of 0.1-0.2 mg kg-1 h-1. Postoperative ketamine infusion was most commonly prescribed as third-line or rescue analgesia. The majority of respondents thought it either 'likely' or 'very likely' ketamine would reduce postoperative chronic pain after thoracic surgery, but not in other surgical categories. Our findings suggest that off-label perioperative administration of ketamine at analgesic dose ranges is routine or common practice in major surgery for a majority of specialist anaesthetists in Australia and New Zealand.