Sustaining a critically injured casualty for hours-to-days when evacuation is delayed beyond the "golden hour"
Prolonged Field Care (PFC) is medical care applied beyond doctrinal planning timelines, when evacuation to higher care is delayed by hours or days rather than minutes. It exists because the "golden hour" MEDEVAC model that defined Iraq and Afghanistan-era battlefield medicine cannot be guaranteed in future conflicts — especially against a peer or near-peer adversary contesting the air.
In 2009, U.S. Secretary of Defense Robert Gates mandated that combat casualties in Afghanistan reach surgical care within 60 minutes of injury wherever possible. Backed by an enormous, largely uncontested rotary-wing MEDEVAC fleet, this "Golden Hour" policy is credited with driving battlefield case-fatality rates to their lowest recorded levels in the history of warfare — the large majority of casualties who survived to reach a surgical team went on to survive their wounds.
That model depended on air superiority. It assumed a helicopter could launch, fly to the point of injury, and return to a surgical facility largely unmolested by enemy fire. Military planners now assess that a future conflict against a peer or near-peer adversary — one contesting the air with integrated air defense, electronic warfare, and long-range fires — cannot make that assumption. MEDEVAC aircraft may be unable to fly for hours; ground routes may be cut off or mined; the surgical team itself may be hours away by any means.
Prolonged Field Care doctrine was developed by the Special Operations medical community starting around 2014 specifically to close this gap: to give the front-line medic, corpsman, or PA the skills, mindset, and minimal-equipment techniques to keep a critically injured casualty alive not for one hour, but for many — sometimes days — before evacuation is possible.
War in Ukraine has turned this planning assumption into observed reality: medical personnel operating in contested sectors have reported casualty evacuation, historically a matter of tens of minutes, stretching to many hours and, in some documented cases, more than a day, because contested airspace and drone surveillance make rapid MEDEVAC runs lethal for the aircrew as well as the casualty.
PFC guidelines frame every prolonged casualty scenario around three questions the senior medic must continuously re-ask, not just once at the point of injury:
• What are my resources? — What equipment, drugs, fluids, blood products, and trained hands are actually on hand, and how long will they last at the rate they are being consumed?
• What is the casualty's trajectory? — Is this patient improving, stable, or deteriorating hour over hour? This question can only be answered by trending vital signs and clinical findings over time, not by a single exam.
• What is my evacuation timeline? — Realistically, when will higher care be reachable, and does that timeline match the casualty's trajectory? If the trajectory is worsening faster than evacuation can arrive, the medic must change the plan — improvise further interventions, request a different evacuation asset, or move the casualty toward care rather than waiting for care to arrive.
These three questions are re-asked on a running loop for as long as the casualty remains in the medic's care — sometimes every fifteen minutes, sometimes every hour, for the full duration of the delay.
PFC does not begin at a fixed clock time; it begins the moment a medic realizes the anticipated evacuation window will not materialize as planned. That recognition point is a doctrinal pivot: the mission shifts from "stabilize the casualty to survive a short flight" to "sustain the casualty indefinitely with the resources at hand."
Signs that trigger the shift into PFC mode include: evacuation request denied or delayed with no new estimated time, loss of comms with the evacuation platform, weather or threat conditions grounding aircraft, or a tactical situation that prevents ground movement. Once recognized, the medic reorganizes priorities — securing a defensible or shelterable location, rationing consumables, and establishing the documentation habits (the PFC flow sheet) that will define the rest of the casualty's care.
| Product | Indication | Trial Design | Key Result |
|---|---|---|---|
| Evacuation Time | Golden Hour (Iraq/Afghanistan) | Typically under 60 minutes to surgical care, air-superiority enabled | Golden Hour: minutes |
| Evacuation Time | Prolonged Field Care (contested) | Hours to multiple days; evacuation timeline often unknown at outset | PFC: hours–days |
| Monitoring Approach | Golden Hour | Point-in-time vital signs, rapid primary/secondary survey, brief handoff | Snapshot-based |
| Monitoring Approach | Prolonged Field Care | Hourly trended vitals on a flow sheet; trajectory over time drives decisions | Trend-based |
| Resource Needs | Golden Hour | Minimal — enough supplies to bridge a short flight to a surgical team | Low reserve required |
| Resource Needs | Prolonged Field Care | Extended fluids, warming supplies, sedation, nutrition, hygiene, morale sustainment | High reserve required |
The single most important philosophical shift in Prolonged Field Care is this: a lone vital sign reading is far less informative than the trend of that vital sign over hours. A blood pressure of 100/70 means very different things depending on whether it was 130/85 an hour ago (worsening) or 80/50 an hour ago (improving) — and a snapshot cannot tell you which.
Vital signs are noisy, and the human body compensates for shock remarkably well for a period of time before it decompensates suddenly. A casualty in early hemorrhagic shock can maintain a near-normal blood pressure through vasoconstriction and tachycardia for a surprisingly long window — right up until compensatory mechanisms exhaust themselves and pressure collapses rapidly.
A medic who checks blood pressure once, sees a reassuring number, and moves on can completely miss this compensated shock state. A medic who checks it every hour and plots it will see the heart rate creeping upward and the pulse pressure narrowing long before the systolic pressure itself drops — and can intervene while the casualty is still in a recoverable physiologic state, rather than reacting only after collapse.
This is why PFC doctrine treats the flow sheet, not the individual reading, as the primary clinical tool.
PFC instructors frequently summarize the doctrine with a single line that has become something close to a mantra in the field: "One vital sign is a data point. A trend is a diagnosis." A blood pressure taken in isolation can reassure a medic right up until the moment a casualty crashes.
A standard PFC flow sheet logs, at minimum, every hour (or more frequently if the casualty is unstable):
• Heart rate — rising trend suggests ongoing blood loss, pain, or early sepsis • Blood pressure (systolic/diastolic) — narrowing pulse pressure often precedes an overt drop in systolic pressure • Respiratory rate — rising rate can signal pain, anxiety, shock, or a developing chest injury • Peripheral oxygen saturation (SpO2) — trending down suggests respiratory compromise or worsening perfusion • Core or peripheral temperature — falling temperature signals hypothermia, a direct driver of the lethal triad • Urine output — one of the best available field proxies for end-organ perfusion when invasive monitoring is unavailable; a falling hourly output is an early warning of inadequate circulating volume
Alongside these numbers, the flow sheet also logs every intervention performed and every medication given with a timestamp — turning the sheet into both a clinical decision tool and, eventually, the handoff document for the receiving surgical team.
PFC training emphasizes classifying the casualty's trajectory into simple operational buckets — improving, stable/plateaued, or deteriorating — based on the shape of the trend lines rather than any single threshold crossing. A casualty whose numbers are all still "within normal range" but trending steadily in the wrong direction across three consecutive hourly checks is treated as a deteriorating casualty requiring escalation of care, even before any individual value crosses a critical threshold.
This trajectory-first mindset is what allows a medic with limited diagnostic equipment — often just a blood pressure cuff, a pulse oximeter, and a watch — to functionally approximate the kind of continuous monitoring an ICU provides with far more sophisticated tools.
Sustaining a casualty for hours or days with a limited medical kit requires a specific skill set beyond initial trauma stabilization. PFC training builds field-expedient techniques for the problems that only emerge with time: hypothermia, unmanaged pain, pressure injury, and the physical and psychological toll of prolonged immobilization on both patient and caregiver.
Hypothermia, acidosis, and coagulopathy reinforce one another in a self-worsening cycle known as the "lethal triad": a cold, injured patient clots blood less effectively, which worsens ongoing bleeding, which worsens shock and acidosis, which further impairs clotting and further drops body temperature. Hypothermia can set in surprisingly fast in a trauma casualty — even in a climate that does not feel cold to an uninjured bystander — because blood loss, exposed skin, IV fluids at ambient temperature, and immobility all accelerate heat loss.
PFC medics are trained to actively fight this from the first hour, not just react to shivering. Field-expedient warming techniques include: insulating the casualty from the ground (a major, often-overlooked heat sink), a dedicated hypothermia prevention wrap or blanket system, warming IV fluids before infusion when possible, covering the head and neck (a major site of heat loss), and using chemical heat sources placed away from direct skin contact. Core temperature becomes one of the flow sheet's most closely watched trend lines.
Untreated pain over many hours is not merely humane to address — it drives tachycardia, hypertension, agitation, and oxygen consumption that a marginal casualty cannot afford. But PFC medics typically carry a very limited analgesic and sedative formulary and must titrate carefully, because over-sedation in a casualty with limited airway control or unstable breathing can be as dangerous as untreated pain.
PFC pain and sedation protocols emphasize: starting with the lowest effective dose and titrating to effect rather than to a fixed schedule, continuous reassessment of level of consciousness and respiratory status after each dose, and having a plan for a compromised airway before sedating a casualty who cannot protect it. Every dose given — drug, dose, route, and time — is logged on the flow sheet, both to prevent inadvertent overdose from shift-to-shift caregivers and to inform the receiving medical team.
A urinary (Foley) catheter, when within the medic's scope and equipment, serves two purposes in PFC: patient comfort and hygiene over many immobile hours, and — more importantly — a continuous, hourly measurable proxy for kidney perfusion. Falling urine output is one of the earliest available signs that circulating volume is inadequate, often before blood pressure itself falls.
A casualty who cannot move on their own for many hours is also at real risk of pressure injury developing in a matter of hours, not the days it normally takes in a hospital bed — a risk compounded by shock reducing skin perfusion. PFC protocols call for scheduled repositioning, typically on roughly a two-hour cycle, along with padding bony prominences with whatever improvised material is available.
Finally, PFC doctrine explicitly addresses sustainment beyond pure trauma physiology: nutrition and hydration for extended holds, and the psychological and morale toll on both the casualty and the caregiver, who may be providing intensive one-to-one care for many consecutive hours under threat, fatigue, and uncertainty about when evacuation will finally arrive.
The entire point of hourly trending is to catch deterioration while it is still a trend and not yet a crisis. When a vital sign begins moving into a danger zone, PFC protocol calls for a specific, documented, escalating response — not an improvised one — so that the same warning sign produces the same lifesaving action every time, regardless of which caregiver is on shift.
PFC flow sheets are typically color-banded into stable, watch, and critical zones for each vital sign, but the more important signal is the inflection point — the moment a value that has been flat for several hourly checks begins to move consistently in the wrong direction. A heart rate climbing from 88 to 96 to 108 across three consecutive checks, even if 108 is not yet an alarming absolute number, is treated as a deterioration event because the trajectory itself is the warning.
Catching this inflection early — while the casualty is still in a compensated state — is the entire clinical justification for the hourly-trend discipline. By the time a single spot-check would reveal a crisis (a systolic pressure in the 70s, for example), the window for a simple, low-resource intervention to reverse the trend may already have closed.
When a deterioration event is identified, PFC training discourages ad hoc improvisation in favor of a pre-rehearsed, protocol-driven response appropriate to the likely cause — for example, a fluid bolus and re-examination for a missed bleeding source if hypotension with tachycardia suggests ongoing hemorrhage, or airway and breathing reassessment if oxygen saturation is falling.
Critically, the response itself — what was given, how much, by what route, at what time, and the vital signs immediately before and after — is written onto the flow sheet in real time. This creates an auditable record: if the intervention did not produce the expected trend reversal within the next one to two hourly checks, that failure to respond is itself a trend the medic must recognize and escalate further, rather than assuming the problem is solved because an action was taken.
In a prolonged scenario, caregiver fatigue, shift changes between multiple medics, and the sheer volume of hours involved all create real risk of losing track of what has already been tried, what worked, and what did not. A rigorously maintained flow sheet compensates for human memory limits: a medic coming onto a twelve-hour shift can review the sheet and immediately understand the casualty's full trajectory, every intervention already attempted, and exactly how the casualty responded to each one — rather than restarting the diagnostic process from zero.
This same documentation ultimately becomes the single most valuable object handed to the surgical team at the end of the evacuation: a complete, hour-by-hour physiologic history that would otherwise be entirely lost the moment care transfers to a new team.
The goal of Prolonged Field Care is never to replace evacuation to definitive surgical care — it is to keep a casualty alive long enough to reach it. When an evacuation window finally opens, whether after two hours or two days, the complete PFC flow sheet travels with the patient, compressing the entire prolonged episode into a single document the receiving trauma team can absorb in seconds.
Throughout the entire hold, the medic's objective has never been to definitively fix the casualty's underlying injuries — that requires a surgical team, imaging, blood products, and resources no field kit can replicate. The objective has been narrower and more achievable: keep the casualty's physiology inside a survivable range, hour after hour, for as long as it takes for evacuation to become possible.
When the tactical or environmental situation finally permits movement — air superiority is regained over the extraction route, a ground corridor opens, or weather clears — that evacuation window is often short and unpredictable. PFC doctrine trains medics to keep the casualty continuously evacuation-ready throughout the hold: lines secured, dressings reinforced, warming systems packable, and the flow sheet current, so that no time is lost preparing for movement once the window appears.
At the moment of evacuation, the accumulated PFC flow sheet becomes the single most valuable piece of information the medic can hand to the receiving surgical or higher-echelon medical team. Instead of a brief verbal report covering only the casualty's current state, the team receives the entire trajectory: every hourly vital sign, every medication and dose with timestamps, every deterioration event and how it was addressed, fluid totals in and urine output totals out, and the casualty's response to each intervention over the full duration of the hold.
This lets the surgical team immediately understand not just where the casualty is now, but how they got there — which is often essential for anticipating what is likely to happen next (for example, a casualty who has needed repeated fluid boluses to maintain pressure over many hours may be flagged for immediate blood product resuscitation and urgent operative exploration, rather than a slower initial workup).
PFC training, originally developed within the special operations medical community, has steadily expanded across conventional military medical training as planners across NATO and allied militaries have concluded that contested-airspace evacuation delays are a realistic feature of future large-scale combat, not an edge case. Lessons drawn from the war in Ukraine — where evacuation under contested airspace and drone threat has repeatedly stretched far beyond the Golden Hour benchmark — have been cited directly by military medical planners as validating the PFC Working Group's original planning assumptions from a decade earlier.
The result is a doctrine that, while born in small special operations elements operating deep from support, is increasingly treated as a baseline skill set for any medical provider who might find themselves caring for a critically injured patient with no guarantee of a fast ride to the next echelon of care.
The founding insight of the PFC Working Group has aged into a widely echoed warning across NATO medical planning circles: the Golden Hour was never a law of physiology — it was a property of a specific air-superiority environment. Take away that environment, as contested battlespaces increasingly do, and the hour can become a day.