Much of prehospital practice is inherited through folklore, anecdote, and misapplied pattern recognition — not evidence. Each entry below examines a persistent myth, what the evidence actually shows, where genuine nuance exists, and what the correct prehospital practice is. Evidence quality is graded. The goal is not to be iconoclastic — it is to be accurate.
01
"Bilateral BP difference = Abdominal Aortic Aneurysm"
The most common cause is subclavian artery stenosis / atherosclerosis, not AAA. Interarm differences >10mmHg occur in up to 20% of hypertensive patients with no vascular emergency.
02
"You must treat pyrexia — fever is always harmful"
Fever is an ancient, conserved, adaptive immune response. Evidence does not support routine antipyretic administration. In some contexts, treating fever worsens outcomes.
03
"High-flow oxygen is always safe and beneficial"
Hyperoxia causes vasoconstriction, reduces coronary flow, worsens COPD outcomes, and is associated with increased mortality post-cardiac arrest. Titrate to target SpO₂.
04
"Pinpoint pupils always mean opioid overdose"
Bilateral miosis has numerous causes. Pontine haemorrhage, organophosphates, clonidine, and Horner's syndrome all produce miosis. Naloxone without evidence of opioid response is not benign.
05
"Give glucose to any unconscious patient"
Hyperglycaemia in stroke and TBI worsens outcomes via increased cerebral oedema, acidosis, and infarct expansion. Blind glucose without BM is potentially harmful in the post-ictal or stroke patient.
06
"All trauma patients need spinal precautions"
Routine cervical collar use causes raised ICP, venous obstruction, dysphagia, and delays scene time. Evidence-based selective immobilisation (NEXUS, Canadian C-Spine Rule) is safer than universal collaring.
Myth #1
Cardiovascular
Good evidence to refute
Bilateral BP difference
= Abdominal Aortic Aneurysm
= Abdominal Aortic Aneurysm
VERDICT
The most common cause of interarm BP difference is subclavian artery stenosis and generalised atherosclerosis — not AAA. A bilateral BP difference ≥10mmHg occurs in up to 20% of hypertensive patients asymptomatically. AAA itself has a sensitivity of only ~62% for producing interarm differences. The association is real but non-specific, non-sensitive, and should not anchor clinical thinking.
THE MYTH IN PRACTICE
- BP difference bilateral → "could be AAA" becomes the dominant thought
- Finding anchors clinical reasoning and diverts from more probable causes
- Leads to pattern-matching shortcuts without differential breadth
- Bilateral BP difference is not in AAA diagnostic criteria
- AAA is primarily a felt pulsatile mass + back/flank pain + haemodynamic instability
WHAT THE EVIDENCE SHOWS
- Most common cause: subclavian artery stenosis / atherosclerosis. Prevalence 1.9–7.1% in general/clinical populations (Shadman et al.)
- Interarm difference ≥10mmHg occurs in hypertensive patients without any vascular emergency (PubMed 11927464)
- Differences also caused by: peripheral arterial disease, aortic dissection (Type A), coarctation, brachial artery variation
- For aortic dissection: interarm SBP difference ≥10mmHg has sensitivity 62% / specificity 89% — meaning 38% of dissections DON'T produce it
- IAD ≥10mmHg is actually associated with cardiovascular mortality as a risk marker, not an acute emergency sign
THE GENUINE NUANCE
- In aortic dissection (not AAA), an arm BP difference CAN be clinically useful — it suggests the dissection flap is compromising the subclavian. But it's absent in 38% of dissections.
- AAA rupture is diagnosed clinically: hypotension + pulsatile mass + pain. Not by BP differential.
- A difference ≥20mmHg is more significant — but still non-specific
- Always use the higher reading arm for ongoing BP monitoring — the lower arm may be misrepresenting true pressure
DIFFERENTIAL FOR INTERARM BP DIFFERENCE
- Subclavian artery stenosis (most common)
- Generalised atherosclerosis / peripheral arterial disease
- Aortic dissection involving subclavian ostium
- Thoracic outlet syndrome
- Coarctation of the aorta (arm–leg differential more classic)
- Measurement technique error (different sized cuffs, sequential not simultaneous)
- Physiological variation in hypertensive patients (up to 20%)
- Previous brachial/subclavian surgery, fistula, PICC line
Key Evidence
Clark et al. (Lancet 2012) — 53,827 individuals. IAD ≥10mmHg associated with peripheral vascular disease (RR 2.4), coronary artery disease (RR 2.7), and all-cause mortality. Risk marker, not acute emergency sign.
RCT/CohortIMR Press 2023 (PMID PMC11270447) — IASBPD predicts acute aortic dissection with AUC 0.779, sensitivity 61.7%, specificity 88.9% at ≥10mmHg threshold. Absent in 38% of dissections.
CohortPubMed 11927464 — Bilateral BP >10mmHg difference is frequent in asymptomatic hypertensives. Specificity for pathology only 82%, meaning 18% of positives have no underlying disease even in this enriched population.
PopulationShadman et al. — Subclavian stenosis present in 7.1% of clinical populations. Principal driver of interarm differences. Associated with smoking, hypertension, low HDL — not acute emergencies.
Prehospital Implication
Bilateral BP difference alone should not anchor you to AAA or aortic dissection. Use the full clinical picture: pain character (tearing/ripping, maximal at onset), pulse deficit, haemodynamic status, symptom onset, and risk factors. The presence of a BP difference is supportive context — never diagnostic in isolation. Always document which arm gave which reading and use the higher arm for ongoing management. AAA rupture is a clinical diagnosis of haemodynamic instability + pulsatile mass + pain — bilateral BP is a footnote, not the story.
CORRECT APPROACH
Document both BP values and which arms were used. Note difference as a finding, not a diagnosis. Consider aortic dissection if tearing chest/back pain + maximal at onset + pulse deficit. Consider AAA rupture if hypotension + pulsatile abdominal mass + pain. Treat the haemodynamics. Do not anchor.
Myth #2
Physiology
Strong evidence base
Pyrexia is dangerous —
Always treat fever aggressively
Always treat fever aggressively
VERDICT
Fever is a conserved, purposeful, adaptive immune response that has existed for over 600 million years of vertebrate evolution. The evidence does not support routine antipyretic administration in non-critically ill patients. Multiple RCTs and meta-analyses show no mortality benefit from treating fever in ICU patients, and some studies show antipyretics increase mortality by ~5% in viral infection. The impulse to treat every fever is cultural, not evidential.
THE MYTH IN PRACTICE
- "Temp 38.9° — get some paracetamol on board"
- Tepid sponging routinely applied without evidence
- Fever treated as pathology, not as physiological response
- Antipyretics given prophylactically in suspected infection
- Temperature number drives treatment rather than patient condition
- Cooling blankets applied in sepsis without RCT support
WHAT THE EVIDENCE SHOWS
- Fever has been conserved in warm and cold-blooded vertebrates for 600+ million years — strong evolutionary signal of benefit (Evans et al., Nature Immunol 2015)
- Fever inhibits microbial replication, enhances neutrophil recruitment and activity, increases NK cell cytolytic activity, and accelerates lymphocyte trafficking
- Antipyretic use correlates with 5% increase in mortality in influenza populations (PMC4786079)
- RCTs in ICU: no mortality benefit from antipyretic therapy in septic patients. External cooling may be harmful in sepsis (PubMed meta-analysis)
- PubMed 2019 review: "evidence does not currently support routine antipyretic administration"
- In rabbits: 70% mortality with aspirin vs 16% without in rinderpest virus infection
WHEN FEVER IS GENUINELY HARMFUL — THE NUANCE
- Neurological injury (stroke, TBI, SAH): fever worsens cerebral oedema and secondary injury. Target normothermia actively here.
- Uncontrolled hyperpyrexia (≥41°C): enzyme denaturation, rhabdomyolysis, disseminated intravascular coagulation risk. Treat.
- Febrile seizures in children: controversial whether antipyretics prevent recurrence (Cochrane: they don't reliably), but symptomatic management of distress is reasonable
- Cardiac patients: increased metabolic demand may stress compromised myocardium. Individual judgement.
- Septic shock: hypothermia (anapyrexia) may actually be protective as immune down-regulation — avoid treating if spontaneous temp drops
THE IMMUNE MECHANISM OF FEVER
- Infection/injury → pyrogens (IL-1β, IL-6, TNF-α) → prostaglandin E2 → hypothalamic thermostat reset
- Fever is a regulated, coordinated rise — distinct from hyperthermia (unregulated, e.g. heatstroke, serotonin syndrome)
- Higher temperature: most bacteria and viruses have narrow optimal growth ranges; 38–40°C impairs replication
- Heat shock proteins induced by fever: reduce TNF-α and IL-1 — endogenous protective mechanism
- Lymphocyte homing to lymphoid organs is thermally enhanced — adaptive immunity accelerated
- Antipyretics blunt all of this by blocking PGE2 synthesis (COX inhibition)
Key Evidence
ICU meta-analysis (PMC4879924) — 3 RCTs, 320 patients. No mortality benefit from antipyretic therapy in critically ill patients (RR 0.91, 95% CI 0.65–1.28). Antipyretics reduced temperature effectively but not mortality.
ScienceDirect 2020 — 13 RCTs, 1,963 patients. Antipyretics effectively reduce temperature but do not affect 28-day mortality, hospital mortality, or length of stay. "Treatment should be individualised."
ReviewEvans et al., Nature Immunology 2015 (PMC4786079) — Antipyretics correlate with 5% increase in influenza mortality. Review of 600 million years of fever conservation as adaptive survival mechanism.
ReviewPubMed 31116598 (2019) — "The evidence does not currently support routine antipyretic administration." Review of RCTs in infected patients — contrasting results, some show increased mortality with antipyretics.
ReviewOxford Academic EMPH (2020) — "Let fever do its job." Fever suppression may improve symptoms at cost of longer-evolved defence. 'Immune brinksmanship' theory: body harms itself and pathogen equally, betting on winning the gamble.
Prehospital Implication
Do not reflexively treat pyrexia. Fever in a patient with a normal GCS, no neurological injury, and no hyperpyrexia (≤40.5°C) is an adaptive response that is doing its job. Document the temperature, consider the cause, treat the patient — not the thermometer. Paracetamol to reduce distress or pain is reasonable as symptom management. Administering it as if reducing temperature will improve the infection is not evidence-based. In neurological injury (stroke, TBI, post-arrest), actively target normothermia — this is the context where fever is genuinely harmful.
CORRECT APPROACH
Measure and document temperature. Treat the cause, not the number. Antipyretics for comfort/pain relief: reasonable. Antipyretics as mandatory fever treatment: not evidence-based. Hyperpyrexia ≥41°C: active cooling warranted. Neurological injury with fever: target normothermia. Septic shock with spontaneous hypothermia: do not reflexively warm — it may be protective.
Myth #3
Pharmacology
Dangerous if unchallenged
High-flow oxygen is always safe —
more is better
more is better
VERDICT
Oxygen is a drug. Hyperoxia causes vasoconstriction, reduces coronary blood flow by up to 30%, worsens outcomes in stroke, COPD, MI, and post-cardiac arrest. An RCT showed high-flow O₂ in COPD increased mortality — titrated O₂ reduced mortality by 58% in all breathless patients and 78% in confirmed COPD. Target SpO₂ 94–98% in most patients, 88–92% in COPD/type 2 respiratory failure risk.
THE MYTH IN PRACTICE
- Non-rebreather mask applied routinely to all sick patients
- "Give them some oxygen" as a reflexive comfort measure
- Hypoxic drive theory used to justify low-dose O₂ in COPD — the mechanism is mostly wrong
- 80% of COPD exacerbations receive excess oxygen from ambulance crews (despite guidelines)
- Oxygen continued at 15L/min post-ROSC when saturation already 100%
- High-flow given to chest pain patients without checking SpO₂
WHAT THE EVIDENCE SHOWS
- High-flow O₂ reduces coronary arterial blood flow by up to 30% within 5 minutes in cardiac patients
- Austin RCT (BMJ 2010): titrated O₂ reduced mortality by 58% in all breathless patients, 78% in confirmed COPD vs high-flow
- Hyperoxia post-cardiac arrest associated with increased mortality (Circulation 2011)
- O₂ in acute ischaemic stroke without hypoxia: no benefit, potential harm (AHA 2018 guidelines)
- High-flow O₂ in MI without hypoxia: increases infarct size at MRI (AVOID trial, JAMA)
- COPD: hyperoxia causes hypercapnic acidosis via V/Q mismatch, Haldane effect, and resorption atelectasis — multiple mechanisms, not just hypoxic drive
- 2002 Texas trauma study: prehospital supplemental O₂ in 5,549 patients nearly doubled mortality
WHEN HIGH-FLOW OXYGEN IS INDICATED
- SpO₂ <94% in most patients — titrate up to target
- CO poisoning: 100% O₂ always — CO has 250× affinity for Hb; competitive displacement requires FiO₂ 1.0
- Cluster headache: 100% O₂ is an acute abortive treatment
- Decompression illness: 100% O₂ prehospital
- During cardiac arrest: 100% during CPR is accepted (SpO₂ unmeasurable); titrate immediately on ROSC
- Pneumothorax: high FiO₂ accelerates nitrogen resorption — facilitates resolution of small pneumothorax
WHY COPD HYPEROXIA IS MORE COMPLEX THAN HYPOXIC DRIVE
- V/Q mismatch: O₂ abolishes hypoxic vasoconstriction → blood flows to poorly ventilated lung → CO₂ retention
- Haldane effect: oxyhaemoglobin carries CO₂ less well than deoxyhaemoglobin → dissolved CO₂ rises in plasma
- Resorption atelectasis: high FiO₂ replaces N₂ in alveoli → alveolar collapse → more dead space
- Hypoxic drive: only true in a small subset of COPD patients; the above mechanisms are more important and universal
Key Evidence
RCTAustin et al., BMJ 2010 — 405 COPD patients prehospital. Titrated O₂ (SpO₂ 88–92%) vs high-flow mask. Mortality reduced by 58% (all patients) and 78% (confirmed COPD). NNT approximately 14 for COPD.
CohortKilgannon et al., Circulation 2011 — Post-ROSC hyperoxia associated with significantly worse survival to discharge. Dose-dependent relationship between PaO₂ and mortality post-arrest.
RCTAVOID Trial (JAMA 2015) — STEMI without hypoxia: supplemental O₂ increased myocardial injury by 27% on cardiac MRI at 6 months. Infarct size larger in O₂ group.
CohortTexas trauma study 2002 — 5,549 trauma patients. Prehospital supplemental O₂ administration nearly doubled mortality. Plausible mechanism: absorption atelectasis and reperfusion injury.
Prehospital Implication
Treat oxygen as a drug with a dose-response curve and a therapeutic window. Target SpO₂ 94–98% in most patients. Target 88–92% in COPD, known type 2 respiratory failure, or any patient with chronic hypoxic-hypercapnic history. Exceptions: CO poisoning, decompression illness, cluster headache — 100% indicated. In cardiac arrest: 100% during CPR, then immediately titrate on ROSC. In chest pain without hypoxia: withhold supplemental O₂ unless SpO₂ drops below 94%. Use a pulse oximeter to guide dosing — not habit.
CORRECT APPROACH
Check SpO₂ before applying oxygen. If ≥94%: no supplemental O₂ needed. If 88–93%: titrate to low-normal target. If <88%: apply O₂ and titrate to target range. Avoid NRB routinely — use nasal cannula or 28–35% Venturi for titration in at-risk patients. Document starting SpO₂ and target. Treat oxygen like any other drug: indication, dose, route, monitoring.
Myth #4
Toxicology / Neurology
Pattern recognition trap
Pinpoint pupils =
Opioid overdose — give naloxone
Opioid overdose — give naloxone
VERDICT
Bilateral miosis (pinpoint pupils) is a non-specific finding with a broad differential. Opioids are one cause among many. Pontine haemorrhage, organophosphate poisoning, clonidine/alpha-2 agonists, pilocarpine, and Horner's syndrome all produce miosis. Naloxone given without opioid evidence causes acute withdrawal which can precipitate severe hypertension, pulmonary oedema, and seizures. Pattern-matching "pinpoint = opioid" is dangerous in neurology patients.
THE MYTH IN PRACTICE
- Unconscious + pinpoint pupils → naloxone automatically
- Pupil size used as primary diagnostic discriminator
- Pontine haemorrhage missed because of opioid assumption
- Naloxone given to elderly patient with pontine stroke — acute agitation, pulmonary oedema risk
- Organophosphate toxidrome partially masked/confused by naloxone trial
- Clonidine overdose (common in children) treated as opioid overdose
FULL DIFFERENTIAL FOR PINPOINT PUPILS
- Opioids: bilateral miosis + reduced respiratory rate + reduced consciousness
- Pontine haemorrhage: bilateral pinpoint + coma + quadriplegia/decorticiate. No respiratory depression pattern.
- Organophosphates: SLUDGE/DUMBELS + miosis + bradycardia. Atropine is the antidote.
- Clonidine / alpha-2 agonists: miosis + bradycardia + hypotension. Not reversed by naloxone.
- Horner's syndrome: ipsilateral miosis (partial) + ptosis + anhidrosis. Check for asymmetry.
- Pilocarpine eye drops: miosis without systemic cause — always ask about eye drops
- Cholinergic toxidrome: miosis + bronchospasm + bradycardia + salivation
RISKS OF INAPPROPRIATE NALOXONE
- Acute opioid withdrawal: severe hypertension, tachycardia, diaphoresis — dangerous in ischaemic heart disease
- Acute pulmonary oedema — well-documented complication of rapid naloxone reversal
- Seizures in opioid-dependent patients with acute withdrawal
- Aggressive/combative behaviour on reversal — crew safety and patient injury risk
- Half-life of naloxone (30–90 min) is shorter than most opioids — re-narcotisation after reversal if cause not addressed
DISCRIMINATING OPIOID FROM OTHER CAUSES
- Opioid triad: miosis + respiratory depression (<12) + reduced GCS — all three present
- Contextual evidence: paraphernalia, known user, track marks, witnessed use, pill bottles
- Pontine bleed: sudden onset, usually age >50, hypertensive, no respiratory depression initially
- OP poisoning: SLUDGE — Salivation, Lacrimation, Urination, Defaecation, GI cramps, Emesis. Plus bradycardia.
- Clonidine: child who found medication, bradycardia disproportionate, BP low
- Titrated naloxone (100–200mcg increments): if opioid, partial response guides diagnosis; avoids acute reversal
Prehospital Implication
Pinpoint pupils trigger a differential, not a diagnosis. Ask: is there respiratory depression? Is there clinical context for opioid use? Are there features of an alternative toxidrome (SLUDGE, hemodynamic picture)? Is this a sudden-onset coma in a hypertensive patient (pontine haemorrhage)? If naloxone is indicated, titrate — do not bolus. The goal is improved respiratory drive, not full reversal. A patient who wakes up aggressive and pulls out their IV is not a clinical success.
CORRECT APPROACH
See pinpoint pupils → open the differential. Look for respiratory depression rate, context, toxidrome features. If opioid: titrate naloxone 100–200mcg IV/IM, aim for RR >12, not full wakefulness. If pontine stroke: immediate transport, airway management, no naloxone. If OP poisoning: atropine. If clonidine: supportive, not naloxone. Document which signs drove your clinical decision.
Myth #5
Metabolic / Neurology
Potentially harmful
Unconscious patient —
Give glucose, it can't hurt
Give glucose, it can't hurt
VERDICT
Hyperglycaemia in stroke, TBI, and post-cardiac arrest worsens neurological outcomes. Glucose administration to a stroke patient producing blood glucose of 8–10mmol/L or higher increases cerebral oedema, expands infarct size, facilitates anaerobic metabolism in penumbral tissue, and worsens outcome at 90 days. Glucose should only be given after confirming hypoglycaemia with a BM — never empirically in suspected stroke or neurological emergency.
THE MYTH IN PRACTICE
- "It can't hurt to give glucose" — it can and does in neurological injury
- Glucose given before or without BM in unconscious patients
- Glucagon given to post-ictal hypoglycaemia when oral intake possible later
- 10% or 50% dextrose given empirically in stroke mimics
- Thiamine deficiency not considered before glucose in chronic alcoholics
WHAT THE EVIDENCE SHOWS
- Hyperglycaemia in acute ischaemic stroke: associated with increased infarct volume, worse functional outcomes, and higher mortality at 90 days
- Each 1 mmol/L increase above 7 in acute stroke: 28% increase in relative risk of poor outcome
- In penumbral ischaemic tissue: glucose drives anaerobic glycolysis → lactic acidosis → accelerated neuronal death
- Post-cardiac arrest: hyperglycaemia associated with worse neurological outcome regardless of TTM status
- Wernicke's encephalopathy: glucose administration without thiamine in thiamine-deficient patients (alcohol misuse, malnutrition) precipitates acute Wernicke's
- True hypoglycaemia: only indication for glucose — treat aggressively when BM confirmed <4 mmol/L with symptoms
THE NUANCE — WHEN GLUCOSE IS CLEARLY RIGHT
- BM-confirmed hypoglycaemia (<4.0 mmol/L symptomatic, <3.0 mmol/L any state): give glucose immediately, urgently
- Diabetic hypoglycaemia: 10% dextrose IV preferred over 50% (less phlebitis, smoother correction)
- Hypoglycaemia mimicking stroke: correct glucose → stroke signs resolve = hypoglycaemia, not stroke
- If no IV access and unconscious: glucagon IM — but check BM first if possible
- Post-ictal with confirmed hypoglycaemia: glucose
THIAMINE — THE HIDDEN RISK
- Chronic alcohol use + malnutrition + poor diet → thiamine (B1) deficiency
- Glucose administration in thiamine-deficient state: depletes remaining thiamine → precipitates Wernicke's encephalopathy (confusion, ataxia, ophthalmoplegia)
- Wernicke's is preventable: IV thiamine (Pabrinex) before or with glucose in at-risk patients
- Korsakoff's syndrome (irreversible) follows untreated Wernicke's — permanent amnestic syndrome
- Prehospital: if known alcoholic or malnourished + confused + hypoglycaemic → consider thiamine administration (JRCALC protocol allows this)
Prehospital Implication
Always check BM before giving glucose in any altered consciousness. If <4.0 mmol/L with symptoms: treat. If ≥4.0 mmol/L: glucose is unnecessary and potentially harmful in stroke or TBI. In chronic alcoholics with hypoglycaemia: give thiamine first or simultaneously — Pabrinex IV is available under JRCALC in some trusts. Do not allow the logistics of a difficult IV to override the principle: establish BM, establish indication, then treat. "It can't hurt" is not a clinical justification.
CORRECT APPROACH
Check BM immediately in any altered GCS. BM <4.0 with symptoms → 10% dextrose 100–200ml IV, recheck, repeat to target 6–8 mmol/L. BM ≥4.0 → do not give glucose empirically. Alcohol history + hypoglycaemia → Pabrinex (thiamine) before or with glucose. Post-cardiac arrest → target normoglycaemia; treat hyperglycaemia actively. Suspected stroke + BM ≥4.0 → standard stroke pathway, no glucose.
Myth #6
Trauma
Overused intervention with documented harm
All trauma patients need
spinal precautions + cervical collar
spinal precautions + cervical collar
VERDICT
Routine cervical collar application causes raised intracranial pressure, venous obstruction, dysphagia, skin breakdown, and masking of vascular injuries. The evidence for collar use preventing neurological deterioration is largely absent. Validated clinical decision rules (NEXUS, Canadian C-Spine Rule) have high sensitivity for clinically significant cervical spine injuries and allow safe clearance without imaging in low-risk patients. Selective immobilisation is safer than universal collaring.
THE MYTH IN PRACTICE
- Every RTC → c-collar regardless of mechanism, conscious level, or symptoms
- Collar applied before scene assessment of mechanism
- Collar left on for hours in ED causing pressure sores
- Collar applied to conscious, ambulatory patient who walked away from incident
- Self-extrication without collar being preferable to forced immobilisation ignored
- "Can't be too careful" used to justify universal application
DOCUMENTED HARMS OF CERVICAL COLLARS
- Raised ICP: collar restricts jugular venous drainage → increased intracranial pressure — harmful in TBI
- Venous obstruction: JVP elevation observed with collar application in healthy volunteers
- Dysphagia: airway management impaired, increased aspiration risk
- Cervical collar does NOT prevent spinal movement — studies show it permits 28–50% of normal motion
- Self-extrication by conscious cooperative patient: equivalent or less movement than extrication with full immobilisation devices (Nutbeam et al.)
- Masking of carotid and vertebral artery injuries that require palpation
- NICE guidance (2016) and JRCALC acknowledge evidence of harm
NEXUS CRITERIA — LOW RISK (COLLAR NOT REQUIRED)
- No posterior midline cervical tenderness
- No focal neurological deficit
- Normal level of alertness (GCS 15)
- No intoxication (drugs/alcohol)
- No distracting painful injury
- If ALL 5 met: sensitivity 99.6% for clinically significant cervical injury. Safe to clear without collar.
CANADIAN C-SPINE RULE — HIGH RISK FACTORS
- High risk (immobilise): Age ≥65, dangerous mechanism (fall ≥1m, axial load, high-speed RTC, rollover, ejection, motorised recreational vehicle, bicycle), paraesthesia in extremities
- Low risk (may clear if range of movement adequate): simple rear-end collision, sitting position in ED, ambulatory since injury, no midline pain, delayed onset of pain
- Able to rotate neck 45° left and right: if yes and no high-risk factors → clear without imaging
- Canadian C-Spine Rule: sensitivity 100%, specificity 42% vs NEXUS sensitivity 90.7% in original studies
Key Evidence
Validation studyNEXUS study (N Engl J Med 2000) — 34,069 trauma patients. NEXUS criteria: sensitivity 99.6% for clinically significant c-spine injury. 12.6% of patients would have been immobilised unnecessarily without rule.
Validation studyCanadian C-Spine Rule (JAMA 2001) — Prospective validation, 8,924 patients. Sensitivity 100% in alert, stable patients. Superior specificity to NEXUS (42% vs 12.9%).
Cohort/physiologicalNutbeam et al. (BJA 2020) — Self-extrication by conscious cooperative patients produces equivalent or less cervical spine motion than forced immobilised extrication with full MILS and extrication device.
PhysiologicalMultiple studies (summarised JRCALC 2021): Cervical collars raise ICP, impair venous drainage, permit 28–50% of normal cervical spine motion, and impair airway management. Benefits limited to specific high-risk mechanisms.
Prehospital Implication
Apply clinical decision rules before applying immobilisation devices. A conscious, GCS 15 patient who walked away from a rear-end collision, has no midline tenderness, no neurology, no distracting injury, and is not intoxicated does not need a cervical collar under NEXUS criteria (sensitivity 99.6%). The conscious cooperative patient who wants to self-extricate should generally be allowed to — this produces less motion than forced MILS extrication. Collars should be applied for high-risk mechanisms, unconscious patients, midline tenderness, or neurological deficit. Document your clinical reasoning — not just "c-collar applied per protocol."
CORRECT APPROACH
Apply NEXUS or Canadian C-Spine Rule to every trauma patient. Document your assessment of each criterion. If all low-risk criteria met: clinical clearance — no collar required. If high-risk mechanism or criteria failed: immobilise with collar + head blocks + long board or scoop. Avoid collar in TBI if possible — use manual inline stabilisation if immobilisation genuinely required. Conscious cooperative patient: consider supervised self-extrication. Always document clinical reasoning, not just the intervention.