As a physician monitoring a woman undertaking a 100‑km open‑water swim from [LOCATION] to [LOCATION], what preparations and medical support should I arrange?

Medical Preparation for 100-km Open Water Swim

You must prepare for life-threatening hyperthermia, cardiac arrest in water, and exhaustion-related emergencies by ensuring immediate access to resuscitation equipment on a stable rescue boat, real-time core temperature monitoring, and aggressive cooling strategies throughout the event.

Critical Life-Threatening Priorities

Cardiac Arrest Response

The most catastrophic risk is sudden cardiac arrest during the swim. Do not attempt chest compressions in the water—move the athlete as quickly as possible to dry land or a rescue boat 1. Your rescue boat must provide a stable enough platform for high-quality CPR and AED use. If the boat is too small or unstable, you cannot perform effective resuscitation and must prioritize rapid transport to shore 1.

Essential equipment on the rescue boat:

• AED with waterproof capabilities
• Epinephrine 1 mg for immediate IV/IO administration if non-shockable rhythm
• IV/IO access supplies
• Oxygen and bag-valve-mask for ventilation
• Equipment must be secured and immediately accessible 2, 1

Hyperthermia Management

Water temperatures approaching 31°C (the World Aquatics upper limit) create severe thermal stress during prolonged exposure. Hyperthermia is your primary medical concern for a 100-km swim, as impaired thermoregulation leads to dangerous core temperature elevation, dehydration, and cardiovascular strain 3.

Implement these cooling strategies:

• Pre-cooling: Cool the swimmer before starting (ice vests, cold water immersion)
• Per-cooling: Provide cold fluids during feeding stops; consider ice packs to major vessels during brief rest periods
• Real-time core temperature monitoring: Use wearable temperature sensors to track Tc continuously 3
• Establish clear abort criteria: Define maximum safe Tc (typically 39-39.5°C) and mandate withdrawal if reached

Medical Equipment and Supplies

Comprehensive First Aid Kit

Based on 2024 AHA/Red Cross guidelines, your kit must include 2:

Immediate access items:

• Medical examination gloves (multiple pairs)
• Tourniquet (manufactured, windlass type) for potential boat-related trauma
• Sterile pads (4×4 in, at least 8) for bleeding control
• Aspirin 325 mg (chewable) for cardiac symptoms
• Oral glucose tablets (20g) for hypoglycemia
• Foil blanket for hypothermia (though less likely in warm water)
• Epinephrine autoinjector (minimum 2 doses) for anaphylaxis from marine stings
• Eye/skin wash saline solution for jellyfish stings or irritants

Advanced medical supplies:

• IV access equipment and normal saline
• Epinephrine 1 mg vials for cardiac arrest
• Antiemetics for nausea/vomiting (common in ultra-endurance events 4)
• Electrolyte replacement solutions
• Sunscreen and lip protection (reapply regularly)

Communication and Safety Infrastructure

• UHF radio system for priority medical transmissions between rescue boat and shore support 5
• GPS tracking of swimmer position
• Weather monitoring equipment
• Backup rescue boat in case primary vessel has mechanical failure

Specific Medical Conditions to Monitor

Gastrointestinal Issues

Nausea, vomiting, and diarrhea are extremely common in ultra-endurance water events 4. Prolonged vomiting leads to:

• Severe dehydration and electrolyte imbalances
• Aspiration risk if swimmer becomes disoriented
• Inability to maintain caloric intake (critical for 100-km distance)

Have antiemetics readily available and establish feeding protocols with easily digestible, high-calorie nutrition every 30-60 minutes.

Dehydration and Exhaustion

Despite being in water, dehydration is the leading medical issue in ultra-endurance swimming 5. The combination of:

• Prolonged exertion (likely 20-30+ hours for 100 km)
• Inability to recognize thirst while swimming
• Thermal stress from warm water
• Inadequate fluid intake during brief feeding stops

Monitor for signs requiring immediate intervention:

• Altered mental status or confusion
• Severe weakness or inability to maintain stroke mechanics
• Pallor, diaphoresis, weak peripheral pulses
• Persistent vomiting preventing fluid intake 2

Sleep Deprivation Effects

For a swim lasting 24+ hours, sleep deprivation causes dangerous cognitive impairment and hallucinations 4. The swimmer may:

• Lose spatial orientation
• Swim off course
• Fail to respond to safety instructions
• Develop severe drowsiness leading to aspiration risk

Establish clear abort criteria if the swimmer shows signs of severe sleep deprivation affecting safety.

Infections and Water Quality

Open water swimming carries infection risks, particularly gastrointestinal and skin infections 6. Pre-event:

• Review water quality reports for the route
• Ensure swimmer has updated tetanus vaccination
• Have broad-spectrum antibiotics available for post-event prophylaxis if water quality is questionable
• Monitor for signs of infection in the days following the event

Environmental Hazards

Marine Life Encounters

Depending on location, prepare for:

• Jellyfish stings (vinegar, hot water immersion)
• Marine animal bites or trauma
• Allergic reactions to stings (epinephrine autoinjector) 2

Solar Radiation

Prolonged sun exposure over 20-30+ hours causes:

• Severe sunburn affecting performance
• Increased core temperature
• Dehydration
• Eye damage from glare

Apply waterproof sunscreen every 2 hours and provide UV-protective eye wear during feeding stops.

Staffing Requirements

Based on ultra-endurance event data, you need approximately 2.5 physicians and 7.5 nurses/paramedics per 100 competitors 5. For a single swimmer:

• Minimum 2 medical personnel on the rescue boat at all times
• Shore-based medical team for handoff if emergency evacuation needed
• Rotation schedule if event exceeds 24 hours to prevent provider fatigue

Critical Pitfalls to Avoid

1. Inadequate rescue boat stability: Test CPR and AED deployment on your specific boat before the event. If the platform is unstable, you cannot perform effective resuscitation 1.

2. Delayed recognition of hyperthermia: Unlike hypothermia which swimmers report, hyperthermia causes confusion and altered judgment. The swimmer will not self-report feeling dangerously hot. You must monitor core temperature objectively 3.

3. Underestimating gastrointestinal issues: Vomiting and diarrhea can rapidly progress to life-threatening dehydration and electrolyte imbalances in ultra-endurance events 4, 5.

4. Inadequate communication systems: Radio failure in an emergency is catastrophic. Have backup communication methods 5.

5. Attempting resuscitation in water: This is explicitly contraindicated and ineffective. Move to boat or land immediately 1.

Pre-Event Coordination

• Coordinate with local EMS and hospitals along the route
• Establish evacuation points and transport times to definitive care
• Conduct equipment checks and practice emergency scenarios
• Review swimmer's medical history for seizure disorders, cardiac disease, or lung disease that increase drowning risk 7
• Ensure swimmer has completed appropriate swim testing and training for this extreme distance