Expected Vital Signs in Abdominal Aortic Aneurysm (AAA)
Patients with intact, asymptomatic AAA typically have normal vital signs, while those with ruptured AAA present with hypotension (systolic BP <95 mmHg), tachycardia (heart rate >100-138 bpm), and tachypnea (respiratory rate >28 breaths/min). 1, 2
Intact/Asymptomatic AAA
- Vital signs are typically normal in patients with intact AAA, as most remain asymptomatic until rupture occurs 3, 4, 5
- These patients are usually discovered incidentally on imaging performed for unrelated reasons, with no hemodynamic compromise 3, 4
- Blood pressure may show underlying hypertension, which is a risk factor for AAA development and expansion 6
Symptomatic/Contained Rupture AAA
- Patients remain hemodynamically stable despite contained rupture, as the perivascular hematoma is sealed off by surrounding structures (pleura, pericardium, retroperitoneum) 6
- Vital signs may show mild tachycardia and normotension to mild hypotension 6
- Pain is the predominant presenting feature rather than hemodynamic instability in contained rupture 6, 3
Ruptured AAA (Frank/Free Rupture)
Critical Hypotension
- Systolic blood pressure <95 mmHg is a significant predictor of mortality in ruptured AAA 1
- Blood pressure of 103/47 mmHg has been documented in case reports of ruptured AAA 2
- Permissive hypotension with systolic BP between 60-90 mmHg is the target during resuscitation to maintain mentation while minimizing bleeding 6
Tachycardia
- Heart rate typically elevated >100 bpm, with documented rates of 138 beats/min in ruptured AAA cases 2
- Supraventricular tachycardia can occur as a complication of hemodynamic instability 2
- Tachycardia represents the body's catecholamine response to hemorrhagic shock 6
Tachypnea
- Respiratory rate >28 breaths/min documented in ruptured AAA patients 2
- Increased respiratory rate reflects metabolic acidosis and compensatory mechanisms in hemorrhagic shock 2
Hypoxemia
- Oxygen saturation may drop to 93% on high-flow oxygen (15 L/min by non-rebreather mask) 2
- Acute respiratory failure can result from free rupture into the left hemithorax 6
Laboratory Correlates of Hemodynamic Instability
- Hematocrit <29% and hemoglobin <100 g/L significantly correlate with mortality in ruptured AAA 1
- Leukocytes >14 × 10⁹/L predict poor outcome 1
- Urea >11 mmol/L and creatinine >180 μmol/L indicate renal hypoperfusion and predict mortality 1
- Low diuresis is both a presenting sign and intraoperative predictor of increased mortality 1
Clinical Pitfalls
- Unconsciousness and cardiac arrest are ominous signs associated with lethal outcomes in ruptured AAA 1
- Normal vital signs do not exclude AAA rupture in the setting of contained rupture, where hemodynamic stability can be maintained temporarily 6
- The mortality rate for ruptured AAA is 65-85%, with many patients not surviving to reach the hospital 5
- Avoid aggressive fluid resuscitation that raises blood pressure above the permissive hypotension target, as this increases bleeding rate 6