Burn shock: causes and intensive care

Burn shock is an early phase of severe burn disease, occurring within the first 24-48 hours after major thermal injury. It is characterized by sudden plasma leakage through damaged endothelium, massive "third space" fluid, hypovolemia, and microcirculatory disturbances, leading to hypoperfusion of vital organs. The combination of hypovolemia and vasodilatation-inflammatory mechanisms makes burn shock a mixed pathophysiology, with components of hypovolemic and distributive shock. [1]

The risk of burn shock increases significantly with damage to more than 20% of the body surface area in adults and more than 10-15% in children, as well as in the presence of inhalation injury to the respiratory tract. Correct and timely fluid resuscitation has a decisive impact on survival and complication rates, but excessive volumes ("fluid creep") pose a risk of edema, compartment syndrome, and lung damage. Therefore, starting formulas are currently used, followed by close titration based on clinical goals and biomarkers. [2]

Current clinical guidelines (American Burn Association, 2023) updated key points: starting 2 mL/kg/% of burn with balanced crystalloid in adults, early consideration of albumin in large burns for volume limitation, and selective monitoring of intra-abdominal and intraocular pressure; evidence to support routine high-dose vitamin C or fresh frozen plasma for initial resuscitation is insufficient. [3]

Code according to ICD-10 and ICD-11

Burn shock is classified as a traumatic shock in the international classification. In ICD-10, the correct code is T79.4 "Traumatic shock," with additional codes in the range T20-T32 to describe the location and area of burns, including T31/T32 for the percentage of body surface area. Code R57.x refers to unspecified shock and should not be used for burn shock. [4]

ICD-11 uses NF0A.4 "Traumatic shock, not elsewhere classified," and the cause (burns) is specified by post-coordination from the ND90-NE1Z block ("Burns of external surface..." and "Burns of multiple or unspecified areas") and external cause codes. This approach improves the accuracy of patient reporting and routing. [5]

Table 1. Codes for burn shock

Classification	Basic shock code	Additional codes for burns	Notes
ICD-10	T79.4 "Traumatic shock"	T20-T32; T31/T32 - surface percentage	Do not use R57.x for burn shock. [6]
ICD-11	NF0A.4 "Traumatic shock"	ND90-NE1Z (burns by localization/multiple), external cause	Post-coordination is mandatory. [7]

Epidemiology

More than 11,000,000 people worldwide suffer burns annually, with low- and middle-income countries accounting for over 90% of the burden. Among hospitalized adults, the proportion of burns involving more than 20% of body surface area is approximately 10%, defining the primary patient population at risk for burn shock. Mortality from severe burns varies by region and resource, but in current specialized care settings is significantly lower than historical values. [8]

Recent meta-analyses show that for severe burns (more than 20% of the burn area), mortality in North America fluctuates around 20% (confidence intervals vary by model and center), and the presence of inhalation injury significantly increases the risk of death, which is reflected in prognostic scales. These figures are not equivalent to "burn shock mortality," but indirectly characterize the severity of the cohort where shock most frequently occurs. [9]

In children, damage to 10% of the body's surface area is considered serious, due to a different surface-to-volume ratio and physiological characteristics. In the pediatric population, burn shock occurs with a smaller affected area than in adults and requires different fluid management and mandatory glucose support. [10]

Table 2. Epidemiological landmarks

Indicator	Adults	Children
High risk threshold for burn shock	≥20% of body surface area	≥10-15% of body surface area [11]
Proportion of patients with >20% area among hospitalized patients	≈10% (one of the larger samples)	Lower than in adults
Impact of inhalation injury	Significantly increases mortality	Same

Reasons

The main cause is thermal injuries (flames, boiling water, hot surfaces). In electrical and chemical burns, the risk of shock is further increased by deep tissue necrosis and myoglobinemia. Inhalation of combustion products (carbon monoxide, cyanides, irritating gases) not only impairs oxygenation but also intensifies the systemic response, worsening the course of shock. [12]

Combined trauma (a combination of burn and mechanical blood loss) creates mixed shock mechanisms, where burn hypovolemia is accompanied by a hemorrhagic component. Such situations require parallel strategies for bleeding control and burn resuscitation. [13]

Risk factors

Burn area and depth are key determinants. Age over 60 years, the presence of inhalation injury, underlying cardiac, pulmonary, and renal disease, and delay in initiating adequate fluid therapy increase the risk of shock and adverse outcomes. [14]

Excessive fluid creep itself becomes a factor in complications—from compartment syndromes of the extremities and orbits to intra-abdominal hypertension and abdominal compartment syndrome. Therefore, the current strategy is "minimally sufficient" fluid administration with early addition of albumin for large burns. [15]

Table 3. Risk factors for severe course of the disease

Factor	Comment
Burn area	Risk of shock ↑ at ≥20% in adults; ≥10-15% in children. [16]
Inhalation injury	Significant risk multiplier. [17]
Age and comorbidity	Worse reserves, higher mortality. [18]
Delayed resuscitation or "fluid creep"	Risk of hypoperfusion or edematous complications. [19]

Pathogenesis

In the first hours after a burn, generalized endotheliopathy develops: capillary permeability increases not only in the damaged area but also systemically. Plasma and proteins leak into the interstitium, the effective circulating blood volume decreases, and stroke volume and cardiac output fall. This is the "Ebb phase," characterized by low cardiac output, vasoconstriction, and organ hypoperfusion. [20]

A cytokine "storm," complement activation, neurohumoral shifts, and coagulopathy contribute to microcirculatory disorders and tissue hypoxia. After 24-48 hours, the "flow phase" begins—hypermetabolism with high energy and protein requirements, requiring early enteral nutrition. [21]

Symptoms

Clinical manifestations range from thirst, tachycardia, and oliguria to hypotension, impaired consciousness, and signs of organ dysfunction. In adults, the target hourly diuresis with adequate resuscitation is approximately 0.5-1.0 ml/kg/hour (usually 30-50 ml/hour); in children, it is approximately 1.0 ml/kg/hour; in cases of electrical injury and myoglobinuria, it is higher. [22]

Signs of inhalation injury (smoke around the mouth, singed nasal hairs, hoarseness, soot in the sputum) are red flags of a severe course. Increasing swelling of the extremities with pain and coldness distal to the burn is a possible compartment syndrome. [23]

Classification, forms and stages

Historically, Russian-language schools have distinguished "erectile" and "torpid" stages of burn shock (the first 24-72 hours), grading them by area and depth. The modern systemic model is the "ebb phase" (the first 24-48 hours) and the "flow phase" (week-long hypermetabolism), which more accurately reflects metabolic shifts and treatment needs. [24]

The revised Baux index is widely used for prognosis: age + body surface area percentage + 17 in the presence of inhalation injury. Higher values correlate with higher mortality and help stratify risk and resources. [25]

Table 4. Staging and scales

Approach	Definition/formula	Application
Ebb → Flow	Low cardiac output → hypermetabolism	Infusion and nutrition plan. [26]
Baux Revisited	Age + % area + 17 (if inhalation injury)	Rapid risk stratification. [27]

Complications and consequences

Insufficient resuscitation leads to renal failure, intestinal ischemia, multiple organ dysfunction, and death. Excessive resuscitation causes edema, respiratory distress, compartment syndromes of the extremities and orbits, intra-abdominal hypertension, and abdominal compartment syndrome. [28]

Thromboembolic events, infections and sepsis predominate at later stages and are closely related to the size of the burn and the timeliness of surgical treatment (early excision and closure of the wound reduces the risk of infection and mortality). [29]

Table 5. Complications of under- and over-resuscitation

Error type	Possible consequences
Insufficient infusion	Oliguria, acute kidney injury, lactic acidosis, tissue death. [30]
Fluid creep	Pulmonary edema, abdominal and orbital compartment syndromes, difficult ventilation. [31]

When to see a doctor

Immediately - for burns of more than 5% in children or more than 10% in adults, for burns of the face, neck, perineum, with signs of inhalation injury, vomiting, severe thirst, shortness of breath, dark urine, decreased urination, increasing drowsiness, or a drop in blood pressure. These are signs of impending burn shock. [32]

Even with a smaller area, if there is doubt about the depth or there are concomitant diseases of the heart, lungs, or kidneys, an early assessment in a hospital is indicated, since the clinical picture of shock may develop late during the first day. [33]

Diagnostics

Step 1. Initial assessment using ABCDE. Ensure airway patency and oxygenation; early intubation if signs of inhalation injury are present. Carboxyhemoglobin measurement if carbon monoxide poisoning is suspected; bronchoscopy if indicated. [34]

Step 2. Volumetric assessment of the burn. Use the "rule of nines" in adults or the Lund-Browder scheme in children to calculate the percentage of body surface area. Accuracy determines the initial infusion calculation and prognosis (Baux scale). [35]

Step 3. Laboratory and monitoring. Lactate, base deficit, arterial blood gases, electrolytes, creatinine, creatine kinase (in case of electrical injury), complete urinalysis (myo-/hemoglobinuria). Targeted diuresis - as below; consider monitoring intra-abdominal pressure during large volume infusions. [36]

Step 4. Instrumental diagnostics of complications. Doppler ultrasonography of peripheral arteries in case of risk of compartment syndrome; in case of worsening ventilation – chest X-ray or computed tomography; measurement of intraocular pressure in case of severe swelling of the face and orbits. [37]

Table 6. Diagnostic goals and thresholds

Parameter	Target/threshold	Comment
Diuresis (adults)	0.5-1.0 ml/kg/hour	Liquid titration benchmark. [38]
Lactate	Downward dynamics	Perfusion marker.
Intra-abdominal pressure	Monitoring selectively	At high infusion volumes. [39]

Differential diagnosis

Burn shock must be differentiated from hemorrhagic shock in combined trauma (obvious sources of blood loss, hemodynamics responsive to bleeding control), septic shock (late phase with infection, refractory vasodilation), anaphylactic shock (acute onset, skin manifestations, bronchospasm), and neurogenic shock (bradycardia, warm skin, spinal cord injury). Physiologic markers and the context of the injury help clarify these distinctions. [40]

Table 7. Differential diagnostic guidelines

Type of shock	The predominant mechanism	Key Features
Burn	Plasma leak, hypovolemia + inflammatory vasodilation	Large burn area, early oliguria, lactate ↑
Hemorrhagic	Blood loss	Source of bleeding, response to hemostasis
Septic	Infection, vasodilation	Later in time, the infectious focus
Anaphylactic	IgE-mediated mediator release	Ultrasound of the lungs is clear, bronchospasm, urticaria

Treatment

Initial actions. Ensure airway and oxygenation; if inhalation injury is suspected, early intubation is performed with a low threshold. Warming (against hypothermia), analgesia, tetanus prevention, and early enteral support are initiated simultaneously. Inhalation injury requires specific monitoring and, if necessary, bronchoscopy and respiratory support. [41]

Initiating the infusion in adults. The current recommendation from the American Burn Association is to start with 2 ml per kilogram of body weight per percent of burn area of a balanced crystalloid (e.g., lactated Ringer's), then titrate hourly based on targets (diuresis, lactate, base deficit, heart rate, blood pressure). The goal is to maintain perfusion and not "drown" the patient. [42]

Children. Children often require 3 ml/kg/hr plus glucose supplementation due to a tendency toward hypoglycemia; the target urine output is approximately 1 ml/kg/hr. Any formulas are only a starting point; the actual infusion rate is adjusted based on the child's condition and monitoring. [43]

Fluid creep limitation. For large burns, albumin is considered in the first 24 hours to reduce the total crystalloid volume and improve diuresis. Routine use of high-dose vitamin C, fresh frozen plasma, or early continuous dialysis lacks sufficient evidence of benefit during the primary resuscitation phase. [44]

What not to use. Hydroxyethyl starches and similar synthetic colloids are contraindicated in patients with burns and critical illness due to the risk of acute kidney injury and increased mortality. Older approaches with dextran and gelatin are not standard and carry risks. [45]

Monitoring complications. In the case of large fluid volumes, intra-abdominal pressure is selectively measured, pressure in the extremity compartments is monitored, and intraocular pressure is monitored in the case of massive facial edema. Early diagnosis of abdominal compartment syndrome and extremity compartment syndrome prevents ischemic complications. [46]

Inhalation injury and ventilation. In cases of severe airway edema and impaired gas exchange, mechanical ventilation is indicated. Inhalation injury protocols include smoke toxin control (carboxyhemoglobin), airway management, and infection prevention. [47]

Surgical tactics. For deep circumferential burns of the chest or extremities, escarotomies are performed to restore ventilation or blood flow; in some cases, this is a life-saving measure. Early excision and closure of wounds (ideally within the first 3-7 days) reduces mortality, infection rates, and length of hospital stay. [48]

Nutrition and transfusion. Early enteral nutrition within the first 24 hours maintains the intestinal barrier and reduces complications. For red blood cell transfusion, current guidelines recommend a hemoglobin cutoff of approximately 7 g/dL in stable adult burn patients, which reduces transfusion volume without worsening outcomes. [49]

Vasopressors and renal support. Vasopressors are not first-line therapy in burn shock; they are considered only after preload optimization for refractory hypotension. There is insufficient evidence to support the use of norepinephrine over vasopressin in this cohort; early non-fluid-removing hemodialysis as a method of volume reduction also lacks a compelling basis in the first 48 hours. [50]

Table 8. Targets of therapy

Target	Landmark	Notes
Diuresis (adults)	0.5-1.0 ml/kg/hour	Individual titration. [51]
Diuresis (children)	~1.0 ml/kg/hour	Plus glucose. [52]
Start for adults	2 ml/kg/% area	Balanced crystalloid. [53]
Consider	Albumin for large burns	Reduction of infusion volume. [54]

Prevention

Household smoke detectors, fire safety training, and teaching children how to handle hot liquids are simple measures that significantly reduce the risk of severe burns. Personal protective equipment and adherence to safety protocols are essential in the workplace. In the event of a fire, evacuate, protect your respiratory system from smoke, and call emergency services. [55]

If a burn occurs, rapid cooling with cool running water for approximately 20 minutes (without ice), removal of jewelry, sterile closure, and early medical attention if a large area or deep tissue is suspected. These actions reduce the depth of injury and the potential for shock. (Generally accepted management; see also ABLS/ABA clinical courses.) [56]

Forecast

Prognosis is determined by the burn area and depth, the presence of inhalation injury, and age. The revised Baux index is a simple and validated tool for rapid mortality risk assessment and resource planning. Early excision and closure, appropriate fluid management, and early nutrition improve survival and functional outcomes. [57]

Table 9. Prognostic tools

Scale	Components	Comment
r-Baux	Age + % area + 17 (if inhalation injury)	Good discrimination, simplicity at bedside. [58]
ABSI/BOBI	Age, gender, area, depth, inhalation injury	More complex but accurate models. [59]

FAQ

1) How much fluid is "required according to the formula"? The formula is just the start. In adults - 2 ml/kg/% of the burn area; in children, 3 ml/kg/% plus glucose is more often used. Then, every hour, the volume is titrated based on diuresis and perfusion markers to avoid "fluid creep." [60]

2) Is albumin necessary in the first 24 hours? In large burns, albumin can reduce the total crystalloid volume and improve diuresis, so it should be considered – this is the recommendation of the American Burn Association. The decision is individualized. [61]

3) Can starches, dextran, or gelatins be used? No, they are contraindicated for burn patients and the critically ill due to the risk of acute kidney injury and increased mortality. Use balanced crystalloids; the colloid of choice for large burns is albumin. [62]

4) What target values indicate adequate resuscitation? For adults, these include a urine output of approximately 0.5-1.0 ml/kg/hour, a downward trend in lactate levels and normalization of the base deficit, and stable hemodynamics without vasopressors. If deviations occur, the infusion rate is reconsidered and complications are identified. [63]

5) When is an escarotome necessary? For deep circumferential burns of the chest, neck, or extremities that threaten breathing or blood flow. This is an emergency procedure that prevents fatal complications. [64]

Table 10. What is critical to update in local protocols

Paragraph	Modern position
Starting infusion in adults	2 ml/kg/% area, with hourly titration to targets. [65]
Colloids	Consider albumin for large burns; avoid HEC/dextrans/gelatins.[66]
Monitoring	Selectively control intra-abdominal and intraocular pressure. [67]
Nutrition	Initiate enteral feeding <24 hours if possible.[68]
Transfusions	The restrictive threshold of hemoglobin is ≈7 g/dL in stable adults. [69]