What is the latest sign of shock to occur in a patient with Road Traffic Accident (RTA), pelvic fracture, and thigh wound with profuse bleeding, resulting in hypovolemic shock?

Signs of Hypovolemic Shock in RTA with Pelvic Fracture and Thigh Wound

Decreased blood pressure is the latest sign of shock to occur in a patient with road traffic accident (RTA), pelvic fracture, and thigh wound with profuse bleeding, resulting in hypovolemic shock.

Progression of Shock Signs in Hypovolemic Shock

According to the Advanced Trauma Life Support (ATLS) classification of hemorrhage severity, the signs of hypovolemic shock appear in a specific sequence as blood loss increases 1:

1. First signs (Class I-II hemorrhage, 15-30% blood volume loss):

   • Tachycardia (heart rate >100-120 bpm)
   • Anxiety and mild mental status changes
   • Decreased pulse pressure
   • Increased respiratory rate (20-30 breaths/min)

2. Intermediate signs (Class III hemorrhage, 30-40% blood volume loss):

   • Further increased heart rate (>120-140 bpm)
   • Increased respiratory rate (30-40 breaths/min)
   • Decreased urine output (5-15 ml/hr)
   • Confusion and anxiety
   • Increased arteriolar resistance and decreased cardiac output

3. Late signs (Class IV hemorrhage, >40% blood volume loss):

   • Decreased systolic blood pressure (appears only after significant blood loss)
   • Severely decreased urine output (negligible)
   • Lethargy/altered mental status
   • Extreme tachycardia (>140 bpm)

Physiological Explanation

The body's compensatory mechanisms attempt to maintain blood pressure despite significant blood loss through:

• Early increases in heart rate (tachycardia)
• Peripheral vasoconstriction (increased arteriolar resistance)
• Increased respiratory rate to compensate for metabolic acidosis
• Increased cortisol release

Blood pressure is maintained until approximately 30-40% of blood volume is lost, making it a late sign of shock 1. This is particularly important in young, healthy patients who can maintain normal blood pressure despite significant blood loss due to robust compensatory mechanisms.

Clinical Implications for Trauma Patients

In patients with pelvic fractures and thigh wounds with profuse bleeding:

• Relying on blood pressure alone to identify shock can lead to delayed recognition and treatment
• Tachycardia, narrowing pulse pressure, and changes in mental status are more sensitive early indicators
• Base deficit measurements can help identify occult shock before blood pressure drops 1

Management Priorities

For patients with RTA, pelvic fracture and thigh wound with profuse bleeding:

1. Immediate assessment using ATLS hemorrhage classification
2. Early recognition of shock based on heart rate, respiratory rate and mental status changes
3. Rapid control of obvious bleeding sources
4. Damage control resuscitation with limited crystalloid and balanced blood component transfusion 2
5. Urgent surgical or radiological intervention for bleeding control 1

Common Pitfalls

• Waiting for hypotension before initiating treatment - this represents decompensated shock and significantly worsens outcomes
• Overreliance on single vital signs rather than evaluating the complete clinical picture
• Failure to recognize that young, healthy patients can maintain normal blood pressure despite significant blood loss
• Delaying surgical intervention while waiting for "stabilization" in patients with ongoing hemorrhage

Therefore, the answer is C. Increased arteriolar resistance and decreased CO occurs as an intermediate sign, while decreased blood pressure (hypotension) is the latest sign of hypovolemic shock to occur.