9.3 Vital Signs Interpretation, Glasgow Coma Scale & Clinical Reassessment

9.3 Vital Signs Interpretation, Glasgow Coma Scale & Clinical Reassessment

Pediatric and Adult Physiological Norms Across the Lifespan

Vital signs are the physiological bedrock of prehospital assessment. Under the Canadian Paramedic Competence Framework (CPCF Area H2.2 and Appendix A #18), primary care paramedics must possess an exacting knowledge of normal baseline parameters across developmental stages. An isolated set of vital signs represents merely a single snapshot in time; clinical excellence depends upon serial vital sign trending to detect occult physiological decompensation before catastrophic collapse occurs.

Pediatric Blood Pressure Calculation Rules

In children between 1 and 10 years of age, normal blood pressure ranges correlate directly with somatic growth. Paramedics utilize validated mathematical formulas to identify the threshold for pediatric hypotension:

• Lower Limit of Normal Systolic BP (5th Percentile): 70 + (2 × age in years) mmHg
• Median Normal Systolic BP (50th Percentile): 90 + (2 × age in years) mmHg

Clinical Example: For a 5-year-old child, the minimum acceptable systolic blood pressure is 70 + (2 × 5) = 80 mmHg. Any systolic blood pressure below 80 mmHg in this child indicates decompensated shock, a critical medical emergency.

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Comprehensive Vital Sign Modalities & Technical Pitfalls

Blood Pressure: Auscultation vs. Palpation

• Auscultation (Korotkoff Sounds): The clinical gold standard. The cuff is inflated 20–30 mmHg beyond the loss of the radial pulse and deflated at 2–3 mmHg per second. Korotkoff Phase I (initial clear tapping) defines Systolic Blood Pressure (SBP); Korotkoff Phase V (complete disappearance of sound) defines Diastolic Blood Pressure (DBP).
• Palpation: Performed when ambient ambulance noise or extreme vibration precludes auscultation, or during profound circulatory collapse. As the cuff deflates, the return of the palpable radial pulse denotes the SBP. Palpation measures systolic pressure only and is documented as (e.g.) "90/P". Palpation typically underestimates auscultated SBP by 8 to 10 mmHg.
• Cuff Sizing Rules: The inflatable bladder must have a width equal to 40% of upper arm circumference and a length encircling 80% of the arm. A cuff that is too small / too narrow produces falsely elevated readings; a cuff that is too large / too loose produces falsely depressed readings.

Pulse Oximetry (SpO2) and Physiological Pitfalls

Target prehospital oxygen saturation in Canada is 94% to 98% for most acute medical and trauma presentations. In patients with chronic hypercapnic respiratory failure (severe COPD), the target is calibrated to 88% to 92% to avert hyperoxia-induced ventilation-perfusion mismatch and hypercapnia.

Critical monitoring artifacts include:

• Hypoperfusion and Hypothermia: Severe peripheral vasoconstriction prevents pulsatile arterial detection, yielding absent or erratically low SpO2 waveforms.
• Carbon Monoxide (CO) Toxicity: Standard two-wavelength pulse oximeters cannot differentiate oxyhemoglobin from carboxyhemoglobin. A patient in severe carbon monoxide poisoning will present with a falsely reassuring SpO2 of 99% or 100% despite profound cellular hypoxia.
• Methemoglobinemia: Methemoglobin absorbs light at both 660 nm and 940 nm equally, locking standard pulse oximeter displays at approximately 85% regardless of true oxygenation.

Pupillary Dynamics (PERRL)

Pupils are assessed for size (measured in millimeters, normally 2 to 6 mm), shape (round), equality, and light reactivity (direct and consensual constriction):

• Unilateral Dilated, Non-Reactive Pupil ("Blown Pupil"): Signifies compression of the third cranial nerve (oculomotor) against the tentorium cerebelli, caused by uncal herniation from expanding ipsilateral intracranial mass or hematoma.
• Bilateral Constricted, Pinpoint Pupils (Miosis): Classic indicator of opioid toxicity (e.g., fentanyl, heroin) or acute pontine hemorrhage.
• Bilateral Dilated, Sluggish Pupils (Mydriasis): Associated with severe brainstem anoxia, sympathomimetic intoxication (cocaine, amphetamines), or anticholinergic toxidromes.

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Glasgow Coma Scale (GCS) and Neurological Stratification

The Glasgow Coma Scale (GCS) is an internationally standardized, 15-point scoring system assessing central nervous system function across three domains: Eye Opening (E: 1–4), Verbal Response (V: 1–5), and Motor Response (M: 1–6).

GLASGOW COMA SCALE (GCS) MATRIX
[EYE OPENING (1-4)]      [VERBAL RESPONSE (1-5)]      [MOTOR RESPONSE (1-6)]
4: Spontaneous           5: Oriented                  6: Obeys commands
3: To sound/speech       4: Confused conversation     5: Localizes to pain
2: To pressure/pain      3: Inappropriate words       4: Normal flexion (withdrawal)
1: None                  2: Incomprehensible sounds   3: Abnormal flexion (decorticate)
                         1: None                      2: Extension (decerebrate)
                         (T: Intubated/Tracheostomy)  1: None

Traumatic Brain Injury (TBI) Stratification

Total GCS scores range from 3 (deep coma / brain death) to 15 (fully intact):

• Severe TBI (GCS 3 – 8): Denotes severe brain injury and loss of airway protective reflexes. Governed by the classic prehospital aphorism: "GCS of 8, intubate / ventilate." Mandates aggressive airway management, avoidance of hypoxia (SpO2 <90%), and strict prevention of hypotension (SBP <90 mmHg, or <110 mmHg in adults ≥15 years per updated TBI guidelines).
• Moderate TBI (GCS 9 – 12): Significant impairment requiring urgent trauma centre evaluation and rapid neurosurgical consultation.
• Mild TBI (GCS 13 – 15): Concussion or minor head trauma requiring neurological monitoring and cervical spine risk assessment (e.g., Canadian C-Spine Rule).

Pediatric Glasgow Coma Scale (PGCS) Adaptations

For pre-verbal infants (<2 years of age), verbal and motor scores are adapted:

• Verbal: 5 = Coos, babbles; 4 = Irritable, cries consolably; 3 = Cries persistently to pain; 2 = Moans to pain; 1 = None.
• Motor: 6 = Normal spontaneous movements; 5 = Withdraws to touch; 4 = Withdraws to pain; 3 = Abnormal flexion; 2 = Extension; 1 = None.

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Serial Vital Sign Trending and Pathophysiological Patterns

Compensated Shock vs. Decompensated Shock

Shock is inadequate tissue perfusion at the cellular level. Paramedics must recognize the physiological progression:

PHYSIOLOGICAL SHOCK PROGRESSION
[Compensated Shock]   --> Tachycardia, Tachypnea, Normal SBP, Narrowed Pulse Pressure, Pale/Cool Skin
         ↓
[Decompensated Shock] --> Hypotension (SBP Drops), Profound Tachycardia, Altered Mental Status, Oliguria
         ↓
[Irreversible Shock]  --> Bradycardia, Agonal Breathing, Asystole, Cellular Demise

In early compensated shock, systemic vascular resistance increases dramatically via adrenergic vasoconstriction. Systolic blood pressure remains within normal limits, but diastolic pressure rises, producing a narrowed pulse pressure (e.g., BP moving from 120/80 to 112/90 mmHg). Reliance on systolic hypotension to diagnose shock is a lethal clinical error; hypotension marks decompensation.

Cushing's Triad vs. Hypovolemic Shock

A critical distinction on the COPR entry-to-practice exam is the pathophysiological contrast between hypovolemic shock and severe intracranial hypertension (Cushing's triad):

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Clinical Reassessment Intervals and Protocol

Clinical reassessment is a continuous, dynamic duty. Provincial clinical practice guidelines across Canada dictate mandatory minimum reassessment intervals:

• Unstable Patients: Must be completely reassessed at least every 5 minutes. This includes patients with abnormal primary survey findings, physiological shock, Glasgow Coma Scale <13, severe respiratory distress, or those receiving active pharmacotherapeutic interventions (e.g., sublingual nitroglycerin, salbutamol nebulization, epinephrine administration).
• Stable Patients: Must be completely reassessed at least every 15 minutes. This includes conscious, physiologically normal patients with isolated minor complaints.

Stepwise Reassessment Sequence

1. Re-evaluate Primary Survey: Re-check airway patency, work of breathing, respiratory rate, and radial/carotid pulse.
2. Record Complete Vital Signs: Obtain full numerical values (BP, HR, RR, SpO2, and GCS/pupils).
3. Inspect Clinical Interventions: Check tourniquet security and absence of distal bleeding; verify chest seal adhesion and lack of tension build-up; inspect IV site for infiltration and confirm infusion rate; verify oxygen tank volume and mask positioning.
4. Evaluate Patient Response: Inquire about changes in pain severity (repeat OPQRST) or medication adverse reactions (e.g., post-nitroglycerin headache or hypotension).

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Clinical Scenario: Trending Decompensation in Blunt Abdominal Trauma

Prehospital Vignette: The Concealed Internal Bleed

Paramedics respond to a 34-year-old male motorcyclist struck by an SUV at an urban intersection. On scene, the patient was found standing beside his motorcycle, fully alert, with mild left flank tenderness.

Initial On-Scene Vital Signs (Time 00:00):

• HR: 92 bpm (regular)
• BP: 126/82 mmHg (Pulse Pressure: 44 mmHg)
• RR: 18 breaths/min
• SpO2: 98% on room air
• GCS: 15 (E4, V5, M6)
• Skin: Warm, pink, dry

Serial Trending During 20-Minute Transport (Unstable Protocol: Reassessed Every 5 Min):

• Minute 05: HR 108 bpm, BP 122/88 mmHg (pulse pressure narrowing to 34 mmHg), RR 20 bpm. Patient states he feels slightly nauseated and cold. Skin is cool to touch.
• Minute 10: HR 124 bpm, BP 114/90 mmHg (pulse pressure 24 mmHg), RR 24 bpm, SpO2 97%. Skin is cool and diaphoretic. The paramedic identifies compensated hemorrhagic shock from an occult splenic laceration.
• Minute 15: HR 136 bpm, BP 86/60 mmHg, RR 28 bpm. Patient becomes anxious and confused (GCS 14: E4, V4, M6). The patient has crossed into decompensated hemorrhagic shock.

Paramedic Actions: Recognizing rapid decompensation, the paramedic elevates the priority level, notifies the trauma team for activation of the Massive Transfusion Protocol (MTP), establishes two large-bore IVs, initiates a fluid bolus of warmed normal saline titrated to maintain permissive hypotension (target SBP 80–90 mmHg to avoid dislodging internal clots), applies active external warming blankets, and arrives at the trauma bay with clear longitudinal trend documentation.

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Exam Pitfalls & High-Yield Pearls

• The Isolated Vital Sign Illusion: Treating a single "normal" blood pressure reading as proof of stability in a high-energy trauma patient is a classic exam trap. Relying on blood pressure alone ignores the tachycardia, tachypnea, and narrowing pulse pressure of early compensated shock.
• Pulse Oximeter Blindness in CO Exposure: Accepting a 99% SpO2 reading in a patient extricated from an enclosed structure fire or displaying cherry-red skin/headache is a fatal error. Pulse oximetry cannot detect carbon monoxide poisoning; always administer high-flow oxygen via non-rebreather mask regardless of the pulse oximeter value.
• Motor Scoring Accuracy in GCS: When scoring the Motor component of the Glasgow Coma Scale, always score the best response elicited. If a patient localizes with the right arm (M5) but shows abnormal flexion with the left arm (M3), the correct motor score is M5.
• Reassessment Following Interventions: Any time a paramedic delivers a medication (such as nitroglycerin or salbutamol) or performs an invasive procedure, the patient immediately transitions to the 5-minute reassessment interval, even if previously classified as stable.