ABA Pain Medicine cheat sheet

A-delta fibers are thinly myelinated and conduct sharp, well-localized first pain at roughly 5-30 m/s; unmyelinated C fibers conduct dull, burning second pain at 0.5-2 m/s.

Nociceptors transduce noxious stimuli through TRPV1 (heat, capsaicin), acid-sensing ion channels, and mechanosensitive channels; the cell body sits in the dorsal root ganglion and the central terminal ends in the dorsal horn.

Primary afferents synapse in laminae I, II (substantia gelatinosa), and V; wide dynamic range neurons in lamina V receive convergent somatic and visceral input, which explains referred pain and secondary hyperalgesia.

Spinothalamic axons decussate within 1-2 segments in the anterior white commissure and ascend in the anterolateral quadrant to the ventroposterolateral thalamus, insula, and anterior cingulate cortex.

Descending inhibition runs from the periaqueductal gray through the rostral ventromedial medulla to the dorsal horn; serotonin and norepinephrine at these synapses are the targets of SNRIs and tricyclic antidepressants.

Mu, delta, and kappa opioid receptors are G-protein coupled; activation inhibits adenylyl cyclase, opens potassium channels, and closes voltage-gated calcium channels, reducing neurotransmitter release.

Wind-up and central sensitization depend on NMDA receptor activation and glial signaling; ketamine and magnesium act as NMDA antagonists, and this mechanism underlies opioid-induced hyperalgesia.

NSAIDs inhibit cyclooxygenase and reduce prostaglandin synthesis; COX-1 is constitutive (gastric mucosal protection, platelet thromboxane), whereas COX-2 is induced by inflammation.

Local anesthetics block voltage-gated sodium channels from the intracellular side in a use-dependent manner; inflamed tissue is acidic, lowering the uncharged drug fraction and reducing block efficacy.

The numeric rating scale runs 0-10; commonly mild is 1-3, moderate 4-6, and severe 7-10, but a change of 2 points or 30 percent is the usual threshold for clinically meaningful improvement.

Intensity alone is insufficient; document function (activity tolerance, sleep, mood) with the Brief Pain Inventory or the PEG (Pain, Enjoyment, General activity) scale.

Neuropathic screening: a DN4 score of 4 or more out of 10, or a painDETECT score of 19 or higher, suggests a neuropathic component; painDETECT 13-18 is indeterminate.

Patients with advanced dementia who cannot self-report require observational tools such as the Abbey Pain Scale or PAINAD, scored on facial expression, movement, vocalization, and consolability.

Children: use the Wong-Baker FACES scale from about age 3 and the FLACC behavioral scale for preverbal or nonverbal children.

Urgent red flags: new bowel or bladder dysfunction, saddle anesthesia, progressive motor deficit, fever, unexplained weight loss, cancer history, or night pain unrelieved by rest.

Screen psychological comorbidity with the PHQ-9 for depression, GAD-7 for anxiety, and the Pain Catastrophizing Scale; these predict treatment response and disability.

The McGill Pain Questionnaire (and short form SF-MPQ) separates sensory-discriminative from affective-motivational dimensions of the pain experience.

Acetaminophen ceiling is generally 3-4 g/day in healthy adults; reduce to about 2 g/day in hepatic impairment, chronic heavy alcohol use, malnutrition, or low body weight.

MME conversion (CDC): 30 mg oral morphine equals 30 mg hydrocodone, 20 mg oxycodone, or 7.5 mg hydromorphone; methadone conversion is nonlinear and dose-dependent.

NSAIDs: avoid with eGFR below 30, active peptic ulcer, or after CABG; combining an NSAID with an ACE inhibitor and a diuretic (triple whammy) sharply raises acute kidney injury risk.

Tramadol is a weak mu agonist plus serotonin-norepinephrine reuptake inhibitor; it lowers seizure threshold and can cause serotonin syndrome with SSRIs, SNRIs, triptans, or MAOIs.

Duloxetine 60 mg daily is approved for diabetic peripheral neuropathic pain, fibromyalgia, and chronic musculoskeletal pain; it is a first-line neuropathic agent.

Gabapentin and pregabalin require renal dose adjustment and cause sedation, dizziness, and peripheral edema; combined with opioids they increase respiratory depression risk.

Tricyclics (nortriptyline, desipramine) are second-line neuropathic agents; obtain a baseline ECG in older adults and avoid in narrow-angle glaucoma, conduction disease, and orthostatic hypotension.

Lidocaine 5% patch is approved for postherpetic neuralgia: up to 12 hours per day, no more than three patches simultaneously, on intact skin.

Methadone prolongs the QT interval and is metabolized by CYP3A4 and CYP2B6; reserve it for opioid-tolerant patients and obtain ECG at baseline and after dose changes.

Cervical transforaminal epidural steroid injection risks spinal cord infarction from vertebral or radicular artery injury; use blunt-tip needles, contrast confirmation, and avoid particulate steroids.

Facet-mediated pain: two-level medial branch blocks yielding at least 50 percent relief support radiofrequency ablation of the medial branches.

Stellate ganglion block is performed at the C6 (Chassaignac) tubercle, anterior to the longus colli; Horner syndrome indicates sympathetic block but is not required for clinical response.

Celiac plexus or splanchnic nerve block is used for upper abdominal visceral cancer pain, particularly pancreatic adenocarcinoma.

Lumbar sympathetic block targets sympathetically maintained pain of the lower extremity, including complex regional pain syndrome.

Spinal cord stimulation delivers current to the dorsal columns via epidural leads; best evidence is in failed back surgery syndrome and complex regional pain syndrome, usually after a successful trial.

Intrathecal therapy uses only preservative-free approved drugs; morphine and bupivacaine are common, and ziconotide is a non-opioid N-type calcium channel blocker requiring slow titration.

ASRA neuraxial anticoagulation intervals: prophylactic low-molecular-weight heparin 12 hours, therapeutic LMWH 24 hours, apixaban or rivaroxaban 72 hours before the procedure.

Fluoroscopy safety follows ALARA: minimize screening time, maximize distance from the beam, and use collimation, pulsed fluoroscopy, and shielding.

Fear-avoidance model: catastrophic interpretation of pain leads to fear, avoidance, deconditioning, depression, and disability, forming a self-reinforcing cycle.

Cognitive behavioral therapy targets maladaptive pain beliefs and behaviors; acceptance and commitment therapy emphasizes acceptance of pain and engagement in values-based activity.

Graded activity and graded exposure start below the patient's baseline and advance in planned increments, reducing pain-related fear and improving tolerance.

Operant treatment reinforces well behaviors and activity while withdrawing attention from pain behaviors; involving a spouse or family member improves generalization.

Pacing uses time-contingent rather than pain-contingent activity and rest schedules to prevent boom-and-bust cycles.

Relaxation training and biofeedback reduce sympathetic arousal; electromyographic biofeedback is used for tension-type pain and headache.

A Pain Catastrophizing Scale total of 30 or higher indicates clinically relevant catastrophizing and predicts poorer treatment response.

Interdisciplinary functional restoration improves function and return to work more than usual care in chronic low back pain.

The biopsychosocial model integrates biological, psychological, and social contributors and is the conceptual foundation of comprehensive pain care.

Core team members are a physician, psychologist, physical and occupational therapist, nurse, and pharmacist; social work and vocational counseling are added as needed.

Multidisciplinary care involves parallel disciplines; interdisciplinary care adds regular communication, shared goal setting, and a single coordinated treatment plan.

Stepped care moves from self-management and primary care to specialty consultation to intensive interdisciplinary programs based on risk and complexity.

Goals should be SMART (specific, measurable, achievable, relevant, time-bound) and functional, such as walking 20 minutes or returning to part-time work.

IMMPACT core outcome domains: pain intensity, physical functioning, emotional functioning, global improvement, satisfaction, symptoms, and adverse events.

Functional restoration programs combine progressive physical conditioning, cognitive-behavioral intervention, and vocational rehabilitation.

Written care plans and shared decision-making reduce fragmented care and improve adherence across multiple prescribers.

Informed consent requires discussion and documentation of diagnosis, nature and purpose of the procedure, material risks and benefits, alternatives, and the right to refuse.

Risk mitigation for long-term opioid therapy uses prescription drug monitoring program checks, urine drug testing, treatment agreements, and pill counts.

The 2022 CDC guideline recommends individualized, function-focused care, non-opioid options first, no hard MME thresholds, and no abrupt discontinuation of long-term opioids.

Offer naloxone when the dose is 50 MME/day or more, when a benzodiazepine is co-prescribed, or when there is a history of substance use disorder or overdose.

Avoid concurrent opioid and benzodiazepine prescribing; combined use substantially increases the risk of fatal respiratory depression.

Fluoroscopy safety follows ALARA principles; document screening time and radiation dose and use last-image hold rather than additional exposures.

A procedural time-out verifies patient identity, site, procedure, consent, allergies, and anticoagulation status aloud with the full team before starting.

Adverse events and near misses are reported through institutional systems, and harmful events are disclosed to patients as a professional and ethical obligation.