Haemorrhage Shock in Trauma

Shock is defined as an abnormality of the circulatory system that results in inadequate organ perfusion and tissue oxygenation. Haemorrhage is the most common cause of shock in trauma patients.

Haemorrhage is an acute loss of circulating blood volume. Although it can vary considerably, normal adult blood volume is approximately 7% of body weight. For example, a 70 kg male has a circulating blood volume of approximately 5 L. The blood volume of obese adults is estimated based on their ideal body weight, because calculation based on actual weight can result in significant overestimation. The blood volume for a child is calculated as 8% to 9% of body weight (70-80 mL/kg).

Identify the source of bleeding as external or internal.

The physiologic effects of haemorrhage are divided into four classes, based on clinical signs, which are useful for estimating the percentage of acute blood loss. The clinical signs represent a continuum of ongoing haemorrhage and serve only to guide initial therapy. Subsequent volume replacement is determined by the patient's response to therapy.

Parameter	Class I	Class II (mild)	Class III (moderate)	Class IV (severe)
Approximate blood loss	< 15%	15 - 30%	31 - 40%	> 40%
Volume of blood loss (ml)	Up to 750	750-1500	1500-2000	>2000
Heart rate	<100	>100	>120	>140
Respiratory rate	14-20	20-30	30-40	>40
Blood pressure	Normal	Normal	Decreased	Decreased
Pulse pressure	Normal or increased	Decreased	Decreased	Decreased
Urine output (mL/h)	>30	20-30	10-20	Negligible
Mental state	Slightly anxious	Mildly anxious	Anxious, confused	Confused, lethargic
Base deficit	0 to -2	-2 to -6	-6 to -10	-10 or less
Resuscitation required	Monitor	Crystalloid fluid	Crystalloid fluid +/- blood products	Massive transfusion protocol

The diagnosis and treatment of shock must occur almost simultaneously. For most trauma patients, clinicians begin treatment as if the patient has haemorrhagic shock, unless a different cause of shock is clearly evident. The basic management principle is to stop the bleeding and replace the volume loss.

Vascular Access

• Obtain access to the vascular system promptly.
• Insert two large caliber (minimum of 18-gauge in an adult) peripheral intravenous catheters. The most desirable sites for peripheral intravenous lines in adults are the forearms and antecubital veins. If peripheral access cannot be obtained, consider placement of an intraosseous needle for temporary access.
• If circumstances prevent the use of peripheral veins, clinicians may initiate large-caliber, central venous (i.e. femoral, jugular, or subclavian vein) access. A chest x-ray must be obtained after attempts at inserting a subclavian or internal jugular line to document the position of the line and evaluate for a pneumothorax or haemothorax.
• As intravenous lines are started, draw blood samples for type and crossmatch, appropriate laboratory analyses, toxicology studies, and pregnancy testing for all females of childbearing age. Blood gas analysis (and lactate) also may be performed at this time.
• Use fluid warmers in the presence of massive haemorrhage to prevent hypothermia.

Initial Fluid Replacement

• The amount of fluid and blood required for resuscitation is difficult to predict on initial evaluation of a patient. Administer an initial, warmed fluid bolus of isotonic fluid. The usual dose is 1 liter for adults and 20 mL/kg for pediatric patients weighing less than 40 kilograms.
• Observe the patient's response during this initial fluid administration and base further therapeutic and diagnostic decisions on this response. Persistent infusion of large volumes of fluid and blood in an attempt to achieve a normal blood pressure is not a substitute for definitive control of bleeding.
• Early resuscitation with blood and blood products must be considered in patients with evidence of class III and IV haemorrhage. Early administration of blood products at a low ratio of packed red blood cells to plasma and platelets can prevent the development of coagulopathy and thrombocytopenia.
• N.B. Fluid resuscitation and avoidance of hypotension are important principles in the initial management of patients with blunt trauma, particularly those with traumatic brain injury BUT in penetrating trauma with haemorrhage, delaying aggressive fluid resuscitation until definitive control of haemorrhage is achieved may prevent additional bleeding; a careful, balanced approach with frequent reevaluation is required.
• The same signs and symptoms of inadequate perfusion that are used to diagnose shock help determine the patient's response to therapy. The return of normal blood pressure, pulse pressure, and pulse rate are signs that perfusion is returning to normal, however, these observations do not provide information regarding organ perfusion and tissue oxygenation.
• The volume of urinary output is a reasonably sensitive indicator of renal perfusion; normal urine volumes generally imply adequate renal blood flow. Adequate volume replacement during resuscitation should produce a urinary output of approximately 0.5 mL/kg/hr in adults, whereas 1 mL/kg/hr is adequate urinary output for pediatric patients. For children under 1 year of age, 2 mL/kg/hr should be maintained.
• Patients in early hypovolemic shock have respiratory alkalosis from tachypnoea, which is frequently followed by mild metabolic acidosis and does not require treatment. However, severe metabolic acidosis can develop from long-standing or severe shock. Metabolic acidosis is caused by anaerobic metabolism, as a result of inadequate tissue perfusion and the production of lactic acid. Persistent acidosis is usually caused by inadequate resuscitation or ongoing blood loss.

Patient Response to Initial Fluid Replacement

• Rapid response
  • Patients quickly respond to the initial fluid bolus and become haemodynamically normal
  • Blood loss is typically < 15% of blood volume
  • No further fluid bolus or immediate blood administration is indicated
• Transient response
  • Patients respond to the initial fluid bolus but begin to show deterioration of perfusion indices
  • Blood loss is typically 15 - 40% of blood volume
  • Transfusion of blood and blood products is indicated
• Minimal or no response
  • Failure to respond to crystalloid and blood administration
  • Requires immediate, definitive intervention to control exsanguinating haemorrhage

Blood Replacement

• The decision to initiate blood transfusion is based on the patient's response. Patients who are transient responders or nonresponders require pRBCs, plasma and platelets as an early part of their resuscitation.
• Fully crossmatched pRBCs are preferable, but the complete crossmatching process requires approximately 1 hour. For patients who stabilise rapidly, crossmatched pRBCs should be obtained and made available.
• If crossmatched blood is unavailable, type O pRBCs are indicated for patients with exsanguinating haemorrhage. AB plasma is given when uncrossmatched plasma is needed.
• A small subset of patients with shock will require massive transfusion, most often defined as > 10 units of pRBCs within the first 24 hours of admission or more than 4 units in 1 hour.

Coagulopathy

• Severe injury and hemorrhage result in the consumption of coagulation factors and early coagulopathy. Such coagulopathy is present in up to 30% of severely injured patients on admission.
• Massive fluid resuscitation with the resultant dilution of platelets and clotting factors, as well as the adverse effect of hypothermia on platelet aggregation and the clotting cascade, contributes to coagulopathy in injured patients.
• Prothrombin time, partial thromboplastin time, and platelet count are valuable baseline studies to obtain in the first hour.