Case 30: Cerebrovascular Accident

Fig. 30.1

Digital subtraction angiography (DSA)

30.1.7 What Do You See on the DSA Image?

The digital subtraction angiography shows the aortic arch with a catheter clearly visible. Further on, the branches of the left common carotid artery, the brachiocephalic trunk, the right common carotid artery, and the right subclavian artery are visible. There is no contrast in the left subclavian artery. Figure 30.2 outlines the vessels for better understanding.

Fig. 30.2

The same image as in Fig. 30.1, with the vessels outlined

30.1.8 What Is Ms. Ross’s Diagnosis?

Ms. Ross has a proximal occlusion of the left subclavian artery with a corresponding subclavian steal syndrome. Blood supply to the left arm occurs via the left and right vertebral arteries, which is blood considered to be “stolen” from the brain. The subclavian steal syndrome is often asymptomatic. When neurological symptoms occur, these appear as cerebellar symptoms [7]. The result of the occlusion is a much lower measured blood pressure on the affected arm.

>> Dr. Berenice punctured the right radial artery. The measured blood pressure was 210/120 mmHg, and the phenylephrine was promptly reduced. CRNA Judy obtained an arterial blood gas in the meantime; the stat lab showed:

pH: 7.15 (reference 7.35–7.45)
P _aO ₂: 75 mmHg (reference 70–100 mmHg)
P _aCO ₂: 72 mmHg (reference 36–44 mmHg)
HCO ₃^–: 17.8 mEq/l (reference 22–26 mEq/l)
BE: –8 mEq/l (reference ±2 mEq/l)
S _aO ₂: 87.5 % (reference 95–98 %)
Lactate: 0.6 moll/l (reference 0.5–2.2 moll/l)

30.1.9 How Would You Interpret the ABG? How Large Would You Estimate the Dead Space Ventilation to Be, if the End-Tidal CO₂ Is 35 mmHg?

Ms. Ross is hypoxic, with a mixed metabolic respiratory acidosis. The relative dead space ventilation ( ${\dot{V}}_{\mathrm{D}}$ / ${\dot{V}}_{\mathrm{T}}$ ) can be calculated according to the following formula:

${\dot{V}}_{\mathrm{D}}/{\dot{V}}_{\mathrm{T}}=\left(\frac{\mathrm{arterial}\;{\mathrm{CO}}_2-\mathrm{end}-\mathrm{tidal}\;{\mathrm{CO}}_2}{\mathrm{arterial}\;{\mathrm{CO}}_2}\right)$