Shock
A life-threatening condition in which the body's tissues do not receive enough oxygenated blood to function, most commonly caused in trauma by severe blood loss.
In the Field
Shock is the engine that drives most preventable trauma deaths. The textbooks teach you to assess shock by checking blood pressure, looking at skin color, watching for diaphoresis, monitoring an EKG. None of that works in a tactical environment. You are in low light, behind cover, with gloves on, and the patient is wearing a uniform you cannot easily expose. The single most reliable shock indicator you have under those conditions is the radial pulse: whether you can feel it, how fast it is, and whether it is strong or weak. Everything else comes later, when the environment allows it.
Common Mistake
Trying to apply hospital-style shock assessment in a tactical setting where most traditional indicators are not observable, instead of using the radial pulse as the primary field indicator.
Technical Detail
Shock is a state of inadequate tissue perfusion: cells throughout the body are not receiving enough oxygenated blood to maintain normal function. Untreated, shock progresses to organ dysfunction and death.
Categories of shock. Several distinct mechanisms can produce shock, each requiring different treatment:
Hypovolemic shock. Caused by loss of circulating blood volume. In trauma, this is almost always hemorrhagic shock from external or internal bleeding. The dominant form of shock in tactical medical contexts.
Distributive shock. Caused by abnormal blood vessel dilation and redistribution of blood flow. Includes septic shock (infection), anaphylactic shock (allergic reaction), and neurogenic shock (spinal cord injury).
Cardiogenic shock. Caused by failure of the heart as a pump. More common in medical (heart attack) than trauma settings.
Obstructive shock. Caused by physical obstruction of blood flow. In trauma, the most relevant form is from tension pneumothorax compressing the heart and great vessels.
Stages of hemorrhagic shock. The American College of Surgeons categorizes hemorrhagic shock into four classes based on blood loss percentage and physiologic response:
Class I (up to 15 percent blood loss). Minimal physiologic compensation. Mild anxiety. Normal vital signs.
Class II (15 to 30 percent blood loss). Increased heart rate, mild anxiety, narrowed pulse pressure. Blood pressure typically still normal due to compensation.
Class III (30 to 40 percent blood loss). Significant tachycardia, decreased blood pressure, confusion, decreased urine output. Compensation is failing.
Class IV (over 40 percent blood loss). Severe tachycardia, marked hypotension, lethargy or unconsciousness. Imminent death without intervention.
These classes are useful as a teaching framework but are not directly measurable in the field. Field assessment relies on observable surrogate signs.
Field assessment in the tactical environment. Many traditional shock assessment methods that hospital and even routine EMS practitioners rely on are not feasible in a tactical setting:
Blood pressure measurement. A blood pressure cuff requires time, a stable patient, an uninjured arm, and an environment quiet enough to hear or read the result. None of these are reliably available under threat conditions or during a multi-casualty incident.
Skin color and capillary refill. Low-light conditions, vehicle interiors, night operations, dust and contamination, dark or camouflaged uniforms, and the patient's own skin tone all interfere with visual assessment of color and refill.
Diaphoresis (sweating). Difficult to assess on a patient who is already wet from sweat from physical exertion, environmental conditions, blood, or contamination. Cannot be reliably distinguished from non-shock sweating.
ECG monitoring. Requires patient exposure, electrode placement on bare skin, a stable cable run, and a working monitor. Generally available only during evacuation or at a Casualty Collection Point, not at the point of injury.
Mental status changes. Useful when present, but a patient who is anxious from the threat itself or simply quiet from training may not display obvious changes. Late-stage confusion and lethargy are reliable but indicate the patient is already decompensating.
The radial pulse. In the tactical environment, the rate and quality of the radial pulse is the most reliable and feasible shock indicator. The radial pulse can be assessed without removing equipment, in low light, while behind cover, and through tactical gloves with practice.
Three findings carry significant prognostic weight:
Absent radial pulse. A radial pulse that cannot be palpated suggests a systolic blood pressure below approximately 80 to 90 mmHg, indicating significant hemorrhagic shock requiring immediate intervention.
Weak or thready radial pulse. A pulse that is present but difficult to feel suggests compensated shock with reduced stroke volume.
Rapid pulse rate. A radial pulse rate above approximately 100 beats per minute in an adult, particularly when combined with a weak quality, suggests compensatory tachycardia from blood loss.
Combined with the mechanism of injury and any visible bleeding, the radial pulse provides actionable shock assessment in the time and conditions available at the point of injury.
Other field-feasible findings. When operational conditions permit, providers can also use:
Patient-reported anxiety, restlessness, or sense of impending doom.
Visual estimate of blood loss when the wound is accessible.
Mental status compared to the patient's known baseline.
Respiratory rate, when the patient is exposed for chest seal application or other interventions.
When formal vital signs become possible. Once the patient is moved to Indirect Threat Care or onto an evacuation platform, more comprehensive assessment becomes feasible. Blood pressure measurement, pulse oximetry, ECG monitoring, and more thorough physical exam are appropriate at that point. The doctrine is to use the assessment tools the environment allows, not to delay treatment waiting for tools that are not available.
Treatment priority. In hemorrhagic shock, the only effective treatment is stopping the bleeding and replacing lost volume. Tourniquets, hemostatic agents, and rapid evacuation address the underlying cause. Aggressive fluid resuscitation in the prehospital setting is no longer recommended, in favor of permissive hypotension that maintains perfusion without disrupting clot formation.
Decreased blood pressure, when it can be measured, is a late sign of hemorrhagic shock and indicates the patient has already exhausted compensatory mechanisms. Waiting for measurable hypotension before treating is waiting too long. Treatment is driven by mechanism of injury, visible bleeding, and the radial pulse.
Categories of shock. Several distinct mechanisms can produce shock, each requiring different treatment:
Hypovolemic shock. Caused by loss of circulating blood volume. In trauma, this is almost always hemorrhagic shock from external or internal bleeding. The dominant form of shock in tactical medical contexts.
Distributive shock. Caused by abnormal blood vessel dilation and redistribution of blood flow. Includes septic shock (infection), anaphylactic shock (allergic reaction), and neurogenic shock (spinal cord injury).
Cardiogenic shock. Caused by failure of the heart as a pump. More common in medical (heart attack) than trauma settings.
Obstructive shock. Caused by physical obstruction of blood flow. In trauma, the most relevant form is from tension pneumothorax compressing the heart and great vessels.
Stages of hemorrhagic shock. The American College of Surgeons categorizes hemorrhagic shock into four classes based on blood loss percentage and physiologic response:
Class I (up to 15 percent blood loss). Minimal physiologic compensation. Mild anxiety. Normal vital signs.
Class II (15 to 30 percent blood loss). Increased heart rate, mild anxiety, narrowed pulse pressure. Blood pressure typically still normal due to compensation.
Class III (30 to 40 percent blood loss). Significant tachycardia, decreased blood pressure, confusion, decreased urine output. Compensation is failing.
Class IV (over 40 percent blood loss). Severe tachycardia, marked hypotension, lethargy or unconsciousness. Imminent death without intervention.
These classes are useful as a teaching framework but are not directly measurable in the field. Field assessment relies on observable surrogate signs.
Field assessment in the tactical environment. Many traditional shock assessment methods that hospital and even routine EMS practitioners rely on are not feasible in a tactical setting:
Blood pressure measurement. A blood pressure cuff requires time, a stable patient, an uninjured arm, and an environment quiet enough to hear or read the result. None of these are reliably available under threat conditions or during a multi-casualty incident.
Skin color and capillary refill. Low-light conditions, vehicle interiors, night operations, dust and contamination, dark or camouflaged uniforms, and the patient's own skin tone all interfere with visual assessment of color and refill.
Diaphoresis (sweating). Difficult to assess on a patient who is already wet from sweat from physical exertion, environmental conditions, blood, or contamination. Cannot be reliably distinguished from non-shock sweating.
ECG monitoring. Requires patient exposure, electrode placement on bare skin, a stable cable run, and a working monitor. Generally available only during evacuation or at a Casualty Collection Point, not at the point of injury.
Mental status changes. Useful when present, but a patient who is anxious from the threat itself or simply quiet from training may not display obvious changes. Late-stage confusion and lethargy are reliable but indicate the patient is already decompensating.
The radial pulse. In the tactical environment, the rate and quality of the radial pulse is the most reliable and feasible shock indicator. The radial pulse can be assessed without removing equipment, in low light, while behind cover, and through tactical gloves with practice.
Three findings carry significant prognostic weight:
Absent radial pulse. A radial pulse that cannot be palpated suggests a systolic blood pressure below approximately 80 to 90 mmHg, indicating significant hemorrhagic shock requiring immediate intervention.
Weak or thready radial pulse. A pulse that is present but difficult to feel suggests compensated shock with reduced stroke volume.
Rapid pulse rate. A radial pulse rate above approximately 100 beats per minute in an adult, particularly when combined with a weak quality, suggests compensatory tachycardia from blood loss.
Combined with the mechanism of injury and any visible bleeding, the radial pulse provides actionable shock assessment in the time and conditions available at the point of injury.
Other field-feasible findings. When operational conditions permit, providers can also use:
Patient-reported anxiety, restlessness, or sense of impending doom.
Visual estimate of blood loss when the wound is accessible.
Mental status compared to the patient's known baseline.
Respiratory rate, when the patient is exposed for chest seal application or other interventions.
When formal vital signs become possible. Once the patient is moved to Indirect Threat Care or onto an evacuation platform, more comprehensive assessment becomes feasible. Blood pressure measurement, pulse oximetry, ECG monitoring, and more thorough physical exam are appropriate at that point. The doctrine is to use the assessment tools the environment allows, not to delay treatment waiting for tools that are not available.
Treatment priority. In hemorrhagic shock, the only effective treatment is stopping the bleeding and replacing lost volume. Tourniquets, hemostatic agents, and rapid evacuation address the underlying cause. Aggressive fluid resuscitation in the prehospital setting is no longer recommended, in favor of permissive hypotension that maintains perfusion without disrupting clot formation.
Decreased blood pressure, when it can be measured, is a late sign of hemorrhagic shock and indicates the patient has already exhausted compensatory mechanisms. Waiting for measurable hypotension before treating is waiting too long. Treatment is driven by mechanism of injury, visible bleeding, and the radial pulse.