Enhancing Prehospital Emergency Care Through Reliable Assessment of Consciousness Levels: A Structured Narrative Review

Altered level of consciousness (ALOC) is among the most frequent and most consequential presentations in prehospital emergency care. Registry data from unselected ambulance populations indicate that approximately one in eight transported patients has a reduced Glasgow Coma Scale (GCS) score, and that even mild reductions carry substantial 30-day mortality. Assessment of consciousness governs airway management, transport destination, and activation of stroke and traumatic brain injury (TBI) pathways. The GCS and the AVPU scale (rendered AVDS in Portuguese-language services) are the instruments in routine field use, yet both were developed and validated predominantly outside the prehospital environment. This review addresses four questions: (i) the clinical importance of consciousness assessment in prehospital care; (ii) the reliability and validity of the GCS, AVPU/AVDS, and FOUR score, with specific attention to performance in EMS provider cohorts; (iii) the operational and human-factor determinants that degrade assessment accuracy in the field; and (iv) the current evidence for objective adjuncts to subjective scoring. We conducted a structured narrative review reported in accordance with the Scale for the Assessment of Narrative Review Articles (SANRA). PubMed/MEDLINE, Embase, and the Cochrane Library were searched from inception to May 2026, combining controlled-vocabulary and free-text terms across four concept blocks: consciousness; assessment instruments; prehospital/EMS setting; and reliability, validity, accuracy, and inter-rater agreement. Records were screened independently by two reviewers. Where a prior review was identified, its reference list was hand-searched and the underlying primary studies were retrieved and cited in preference to the review, so that evidence is not double-counted. Thirty-six sources form the synthesis corpus. A narrative rather than systematic design was chosen because the eligible literature is heterogeneous in design, population, and outcome metric to a degree that precludes meaningful pooling; the trade-offs of this choice are stated explicitly. Field GCS correlates with arrival GCS ( r = 0.67; n = 12,882) and the change between the two independently predicts mortality. The GCS is the most granular instrument, but its reliability is component-dependent, with the motor component consistently weakest; after structured training, weighted kappa reached 0.85–0.96 across components, motor response remaining lowest at 75.1% agreement. For AVPU/AVDS, large prehospital datasets localise disagreement precisely to the Verbal and Pain categories: in 4.3 million paediatric EMS encounters, overall AVPU-GCS accuracy was 0.95 (kappa = 0.61) but intraclass F1 fell to 0.37 for Verbal and 0.50 for Pain, against 0.98 for Alert; in 2,900 prehospital trauma activations, GCS differed significantly between all AVPU categories except Verbal versus Pain ( p = 0.18). The FOUR score shows modestly superior reliability and validity to the GCS in ICU and ED settings but has not been validated prehospitally. Substituting GCS-motor for total GCS increases undertriage in patients over 65 ( n = 4,480,185). Automated pupillometry substantially outperforms manual pupil examination (ICC 0.99 versus 0.92), and low Neurological Pupil Index (NPi) values are consistently associated with adverse TBI outcomes, though prognostic accuracy in isolation is moderate (AUC 0.66–0.68). Ambulance-based EEG recording is feasible but remains at proof-of-concept stage. The evidence supports specific, bounded recommendations rather than broad prescription. Calibration training should target the GCS motor component and the AVPU/AVDS Verbal-Pain boundary, which are the empirically identified loci of disagreement. Total GCS should be retained over GCS-motor for field triage, particularly in older patients, and all three components should be documented and handed over alongside the total. Automated pupillometry is the most mature adjunct and warrants piloting in defined high-yield scenarios. The central evidence gap remains the principal research priority: no study has directly compared GCS, AVPU/AVDS, and FOUR score reliability within a prehospital provider cohort under field conditions.