Question 18

College answer

a)

Hypovolaemic • Bleeding

Cardiogenic • Acute MI • Graft obstruction • Diastolic dysfunction • RV failure • Pacing problem • Pulmonary hypertension

Distributive • Long bypass time • Occult sepsis (e.g. GI tract ischaemia) • Relative adrenal dysfunction • Nutritional deficiency

Obstructive • Pericardial tamponade • Left Ventricular Outflow Tract Obstruction • Prosthetic valve obstruction • Tension Pneumothorax (may be loculated due to previous surgery) • IABP failure / dyssynchrony/ malposition

Combination of above e.g. Aortic dissection

b)

Medical management only +/- palliation. Considered if prognosis of comorbidities is worse than natural history of AS. Avoids risks of surgery.

Medical management + balloon valvuloplasty. BAV may provide some symptomatic benefit albeit at the risk of complications from femoral vessels/ annular rupture. May also be useful diagnostically to see if dyspnoea improves.

TAVI – femoral access probably unlikely to be possible due to PVD, transapical or transoartic much higher risk but possible. Less invasive.

Discussion

When you fix an aortic stenosis and it all goes well, frequently the patient will become hypertensive instead,  which is clearly not what we see here. The table of potenstial reasons for shock is offered below, and it is similar to what is offered in the chapter about approaching the haemodynamically unstable post-pump patient. 

In light of the offered scenario, several of these possibilities are more likely than the others:

• Vasoplegic shock (long by pass time, more circuit exposure, and with the background history of hypertension one might confabulate that she might have been on an ACE-inhibitor chronically).
• Cardiac tamponade (due to right ventricular injury)
• Right heart failure due to cardiotomy 
• Post-bypass myocardial depression (coronary arteries need to be grafted as an emergency procedure, and the background contains enough ischaemic heart disease; on top of that the college tell us that an IABP was required to wean off bypass)
• Myocardial infarction post-operatively
• Tension pneumothorax (the history of emphysema makes ruptured bullae more likely)

Alternatives to open valve surgery can be listed, but the "advantages/disadvantages" question is an opening to a tabulated response. The best literature reference for this would probably be something like the UpToDate article, which gives you a choice between surgery, TAVI and conservative medical therapy. The 2016 article by Fattouch et al is also a good overview (and free).