The Bradycardic Trauma Patient During Transport
You are the technician on a mobile ECC unit called to a rural clinic 90 minutes from the referral hospital. A 4-year-old Labrador (31 kg) was hit by a car 45 minutes ago. Findings: obtunded but responsive to pain, HR 58 and irregular, weak pulses, RR 32, SpO2 93% on room air, mucous membranes pale, CRT 4 seconds, temperature 36.2 C. A quick FAST exam by the referring vet shows free fluid in the abdomen. PCV 38%, TS 5.4 g/dL, lactate 5.9 mmol/L. The unit carries LRS, 0.9% NaCl, hypertonic saline, a small oxygen cylinder, a manual defibrillator, and one unit of canine packed RBCs (unknown crossmatch). The referral hospital is 90 minutes away and has no blood bank.
1. Explain the bradycardia in this trauma patient and prioritize your interventions for the next 30 minutes.
Read the worked answer
Bradycardia with weak pulses and pale membranes in a trauma patient is not reassuring - it suggests decompensated shock with possible increased vagal tone, hypothermia (36.2 C), or a head/thoracic injury, and is a pre-arrest sign. Do not interpret a "normal-ish" HR as stability.
Priorities (next 30 min):
- Oxygen by mask/flow-by; SpO2 93% is marginal.
- Warm the patient - hypothermia worsens coagulopathy and bradycardia; use blankets and warmed fluids if available.
- Crystalloid bolus: 10–20 mL/kg LRS (310–620 mL) over 15–20 min with reassessment; if BP remains low, consider HTS 4 mL/kg as a bridge.
- Control external hemorrhage if present; splint fractures.
- Establish the need for blood: with TS 5.4, PCV 38 (likely pre-hemodilution), and abdominal free fluid, the dog likely needs transfusion. The single unit of pRBC is a bridge - type/crossmatch if time allows; if not, use the unit and monitor for reaction.
- Prepare for transport: secure airway, monitor HR/BP/SpO2 continuously, and pre-alert the hospital.
The judgement point: bradycardia in shock is a red flag, not a comfort.
2. During transport the HR drops to 42 and the dog becomes unresponsive. The monitor shows a wide-complex rhythm at 40 bpm. What do you do, and what is the reasoning?
Read the worked answer
This is a peri-arrest bradyarrhythmia (wide-complex, slow) with loss of consciousness. Follow a bradycardia-with-pulses algorithm, escalating to CPR if pulses are lost.
Actions:
- Confirm pulses and responsiveness; if pulseless, start CPR immediately (compressions 100–120/min, 1/3 chest depth, 2-min cycles, minimize interruptions).
- If pulses present: oxygen, atropine 0.04 mg/kg IV (≈1.2 mg) - repeat once if no response; consider a second vagolytic or, per protocol, epinephrine at low dose for refractory bradycardia.
- Treat reversible causes: hypothermia, hypoxia, hypovolemia, hyperkalemia (check if possible), tension pneumothorax.
- Continue volume resuscitation cautiously; do not withhold fluids for bradycardia alone.
- Pre-alert the hospital for a peri-arrest arrival.
Reasoning: wide-complex bradycardia with collapse is an unstable rhythm; atropine is first-line for vagally mediated bradycardia, but if the rhythm is an escape rhythm from severe hypoxia or hyperkalemia, atropine will not fix it - treat the cause. The decision point is pulses vs. no pulses, which changes the algorithm entirely.