C & H — Circulation and Hypothermia: Pressure Dressings & Heat Loss Prevention

By the time you reach the C and H of MARCH, the loudest problems are handled: the massive bleed is controlled, the airway is open, and the chest is sealed. Circulation and Hypothermia are where you consolidate those wins, and where a lot of casualties are quietly lost. C means finding the bleeding you missed and making sure every intervention is still doing its job. H means keeping the patient warm, because a trauma patient who gets cold loses the ability to clot, and the bleeding you already stopped can start winning again. Neither step is dramatic. Both are decisive.

C — Circulation: Find What You Missed, Recheck What You Fixed

The circulation phase starts with a deliberate head-to-toe blood sweep. Adrenaline, dark clothing, and darkness itself hide wounds; a casualty focused on the obvious leg injury may have no idea about the second wound under their jacket. The sweep is systematic, run gloved hands along the back, armpits, groin, and every surface you have not directly seen, checking your gloves for blood as you go. A wound you cannot see is a wound you cannot treat.

The second half of C is reassessment. Interventions fail: a tourniquet applied over bulky clothing loosens as fabric compresses, packed gauze can slowly soak through, and a dressing that was tight on scene shifts during movement. Look at each one again. Is the bleeding still stopped? If a tourniquet has stopped working, formal training teaches when to tighten it and when to add a second one above it, that judgment call is exactly why the course matters more than the gear. This is also the phase where trained responders assess for shock: pale, cool, clammy skin, a weak or absent radial pulse, and confusion are signs the body is losing the fight even without visible blood on the ground. Everything you need to stock for this phase lives in our C — Circulation collection.

Pressure Dressings: The Workhorse of the C Phase

The signature tool here is the pressure dressing. The 6 inch Emergency Trauma Dressing combines a sterile pad with an elastic wrap and pressure bar, so you can convert two hands holding a wound into a secured intervention and move on. It reinforces packed wounds from the M phase, covers the lesser bleeds that did not justify a tourniquet, and frees you to manage the rest of the patient. A 6 inch elastic compression wrap earns its slot too, it secures dressings, splints, and chest seal edges when tape fails on wet skin. If you have not read it yet, the Massive Hemorrhage deep dive covers where those original interventions came from.

H — Hypothermia: Why Trauma Patients Get Cold So Fast

A bleeding trauma patient is not just a healthy person who happens to be chilly. Blood loss shuts down the body's heater. Less circulating volume means less warm blood reaching the skin and core, shock diverts what remains to the vital organs, and the body loses its ability to generate and retain heat. Add cut-away clothing, blood-soaked fabric, wind, and direct contact with cold ground or pavement, and core temperature can drop startlingly fast, even indoors.

This matters because of what medics call the lethal triad: hypothermia, acidosis, and coagulopathy, three problems that feed each other in a spiral. Explained simply: as the body cools, the clotting process, which is driven by temperature-sensitive chemistry, stops working properly. Poor perfusion from blood loss makes the blood more acidic, which degrades clotting further. Worse clotting means more bleeding, more bleeding means less warm blood, and the spiral tightens. A casualty whose core temperature drops even a few degrees can bleed from wounds that had already stopped. Keeping the patient warm is not comfort care, it is bleeding control.

Preventing Heat Loss in the Field

Hypothermia prevention is cheap, light, and mostly about denying the ground and the air access to your patient:

• Get them off the ground. Conduction into cold earth, concrete, or a truck bed steals heat faster than the air does. A pack, jacket, foam pad, or folded tarp under the casualty is one of the highest-value moves you can make.
• Cover them, including the head. A heat-reflective Mylar rescue blanket weighs a few ounces and reflects radiated body heat back at the patient. Wrap it around, not just over, and layer real insulation like blankets or sleeping bags on top when available.
• Remove wet fabric where practical. Blood-soaked and rain-soaked clothing wicks heat away continuously. Cut away what is wet, then cover what is exposed.
• Block the wind. Move the casualty into a vehicle or structure, or use bodies and gear as a windbreak while awaiting EMS.

Stock the H phase from our Hypothermia and Head Injury collection, a blanket or two adds almost nothing to a kit's weight and covers one of the deadliest gaps in most civilian IFAKs.

Yes, Even in Warm Climates

The most common mistake is treating H as a winter problem. Trauma-induced hypothermia is documented in casualties injured in desert heat. A patient in shock lying on shaded concrete in an 80-degree parking garage, wet with blood, with clothing cut away, is losing heat faster than their compromised body can replace it. The threshold that matters is not the air temperature, it is whether the patient's body can keep its core warm, and in serious hemorrhage the answer is usually no. If your kit lives in Florida or Arizona, it still needs a blanket.

Closing Out the Sequence

C and H are the phases that reward discipline over drama: sweep thoroughly, recheck honestly, insulate early. From here the MARCH sequence hands off to pain management, antibiotics, and evacuation, the domain of formal medicine. If you are building toward the full protocol, start with the complete MARCH pillar guide, review the Airway and Respiration deep dive, and pressure-test your skills with our dryland training drills. Then take a Stop the Bleed or TECC course, gear stops bleeding and holds heat, but only training makes you the person who uses it well.

This article is educational content, not medical advice; seek formal training such as Stop the Bleed or TECC before relying on these interventions.