Eric J. Visser

Massive clonidine overdose during refill of an implanted drug delivery device for intrathecal analgesia: a review of inadvertent soft-tissue injection during implantable drug delivery device refills and its management.

OBJECTIVES The study aims to highlight the potentially serious consequences of inadvertent soft-tissue injection of intrathecal drugs such as clonidine, during refills of implanted drug delivery devices, and to suggest strategies to reduce this complication. DESIGN Case report and literature review were used. RESULTS We report the case of a 51-year-old female with chronic arm pain who sustained a massive clonidine overdose (18,000 mcg) due to inadvertent soft-tissue injection during a refill of an implanted drug delivery device, resulting in rapid loss of consciousness and significant cardiovascular instability requiring urgent resuscitation, subsequent myocardial infarction, cardiac failure, and other significant complications. The risks of inadvertent soft-tissue injection of intrathecal drugs during implanted drug delivery device refills and management of such events is poorly documented in the literature. CONCLUSION Inadvertent soft-tissue injection is possibly an underappreciated and underreported complication of intrathecal analgesia via an implanted drug delivery device. Under some circumstances, large doses of other intrathecal drugs such as bupivacaine, opioids, ziconotide, and baclofen may also be delivered by inadvertent soft-tissue injection with potentially life-threatening consequences. We recommend that practitioners, institutions, and professional bodies who manage patients with intrathecal analgesia via intrathecal drug delivery devices highlight and audit this complication and develop systems to manage it.

EXPANDING MELZACK'S PAIN NEUROMATRIX. THE THREAT MATRIX: A SUPER‐SYSTEM FOR MANAGING POLYMODAL THREATS

To the Editor: Ronald Melzack proposed that pain is generated by a pain neuromatrix in the brain (and integrated in a “virtual body-self”) in response to actual or perceived tissue threat. As an extension of this theory, we postulate the existence of a “black-box” threat management super-system integrated within the virtual body-self (VBS) of humans called the Threat Matrix (TM), which manages the barrage of actual and potential (perceived) threats to tissue integrity such as wounding, inflammation, conflicts in sensory processing and psychocognitive inputs. Various “threat-inputs” such as fear-cognition, nociception, immunoception, chemoception, and conflicts in sensory or sensorymotor processing can activate the TM, which in turn may generate a repertoire of defensive responses such as fear (anxiety), pain, itch, sensations of noxious heat or cold, nausea, dyspnea (suffocation), and fatigue. The TM also integrates systemic (whole-person) responses such as the acute (“fight or flight”) and chronic (“sickness”) stress response and “suffering”. The TM also generates “protective” motor responses (limb weakness, paralysis or dystonia, to “protect” an at-risk limb), sensory responses (nondermatomal sensory deficits or “neglect”, to “ignore” an at-risk limb), pain behaviors (“signaling” tissue damage to others to engender help) and even dissociation/depersonalization responses (as a means of “escaping” from the VBS when overwhelmed by threat). These so-called quasi-neurological sensory and motor deficits associated with significant biological or psycho-social (“yellow flag”) threat (stress) loading are frequently diagnosed as somatoform and conversion disorders, but may actually represent TM defensive responses. The TM usually produces “congruous” defensive responses to particular threatening stimuli; nociception would normally produce pain, cutaneous chemical irritation (itch), systemic chemotoxins (nausea), thermal stimuli (noxious heat or cold), impaired gas exchange (dyspnea), cognitive threats (fear and phobias). However, as an integrated threat management super-system, we postulate that any threat stimulus could conceivably produce any-orall of the TM’s repertoire of defensive responses and that in states of extreme threat loading, polymodal responses may be generated. Panic disorder is an example of how a specific threat (a fearful cognition) produces a wide repertoire of symptoms (generated and integrated by the TM), including not only fear (the congruous response), but also nausea, chest and abdominal pains, dyspnea (suffocation) and feelings of depersonalization. In our model, the symptoms of a panic attack reflect many of the components of the TM defensive repertoire. Like Melzack’s pain neuromatrix, the TM is not a defined anatomical or functional entity; there is no “threat center” in the brain or elsewhere, just as there is no “pain center”. The TM is currently conceptualized as a “whole-person” threat management super-system which most likely encompasses neural (neurons and glia), immune, endocrine, paracrine, and cellular components. In conclusion, we propose the TM as a model to explain the wide-ranging and sometimes puzzling variety of threat-related phenomena seen in humans, including pain, fear, sensory-motor dysfunction, illness behaviors, stress and sickness responses and suffering, especially in situations of extreme threat or stress loading.

IS MIGRAINE A COMPLEX REGIONAL PAIN SYNDROME OF THE BRAIN? MIGRAINE PROPHYLAXIS WITH VITAMIN C?

To the Editor: Throughout an article recently published in Pain Practice, the authors recommend the use of urine drug testing for patients with pain, and yet they write in the conclusion there is no evidence it would improve outcomes. In support of that statement, a recent systematic review of studies looking at the use of controlled substance agreements and urine drug testing found “. . . that weak evidence supports the use of treatment agreements and urine drug testing to reduce opioid misuse, despite the theoretical benefits of these strategies.” In addition, the article did not address questionnaire design or issues pertaining to the possible impact drug testing may have on the patient and the doctor–patient relationship. Also, the authors did not discuss potential legal issues with conducting suspicionless searches or invading one’s privacy, both of which may be constitutionally prohibited. Physicians in the employ of state or federally funded organizations, such as an academic pain center or Veterans Administration hospital, are considered “government actors” and are subject to both state and federal constitutions (see New Jersey v. T. L. O., 469 U. S. 325, 335–337 [1985]). Moreover, consent to search urine often comes from a controlled substance agreement, and there are questions as to whether agreements are legally valid. Until there is evidence that urine drug testing provides greater good than harm, it should be used with caution.

Time to reconsider steroid injections in the spine

MJA 199 (11) · 16 December 2013 754 Before impeaching facet joint injections and medial branch blocks, and thereby medial branch neurotomies, as well as lumbar transforaminal epidural steroid injections, Harris and Buchbinder should consider: • interprofessional patient-centred approaches are key; • pharmacological management is often ineffective; • their view does not reflect the current practice of Australian pain medicine physicians; • these procedures help people struggling to continue in social roles and maintain quality of life, so they help to reduce the economic impact of spinal pain on Australian society. We support education to improve evidence-based practice of interventional procedures.

IS MIGRAINE A COMPLEX REGIONAL PAIN SYNDROME OF THE BRAIN? MIGRAINE PROPHYLAXIS WITH VITAMIN C?: Letters to the Editor

To the Editor: Throughout an article recently published in Pain Practice, the authors recommend the use of urine drug testing for patients with pain, and yet they write in the conclusion there is no evidence it would improve outcomes. In support of that statement, a recent systematic review of studies looking at the use of controlled substance agreements and urine drug testing found “. . . that weak evidence supports the use of treatment agreements and urine drug testing to reduce opioid misuse, despite the theoretical benefits of these strategies.” In addition, the article did not address questionnaire design or issues pertaining to the possible impact drug testing may have on the patient and the doctor–patient relationship. Also, the authors did not discuss potential legal issues with conducting suspicionless searches or invading one’s privacy, both of which may be constitutionally prohibited. Physicians in the employ of state or federally funded organizations, such as an academic pain center or Veterans Administration hospital, are considered “government actors” and are subject to both state and federal constitutions (see New Jersey v. T. L. O., 469 U. S. 325, 335–337 [1985]). Moreover, consent to search urine often comes from a controlled substance agreement, and there are questions as to whether agreements are legally valid. Until there is evidence that urine drug testing provides greater good than harm, it should be used with caution.