A 66-year-old female with a history of peripheral vascular disease, hypertension, prior stroke, and insulin-dependent diabetes is found to have expansion of her abdominal aortic aneurysm (AAA) on interval surveillance imaging and is scheduled for elective AAA open repair. As part of her preoperative workup, she has a positive nuclear stress test, leading to a cardiac catheterization showing 80% stenosis of the distal left anterior descending (LAD) artery. She undergoes elective AAA repair and is admitted to the ICU afterward. During her recovery, a family member is upset to learn that her coronary artery disease was not fixed before such a large surgery.
How do you answer?
Correct Answer: C
The Coronary Artery Revascularization Prophylaxis Trial, published in the New England Journal of Medicine in 2004, completed a multicenter randomized clinical trial to assess whether preemptive coronary revascularization (either percutaneous coronary intervention or coronary artery bypass graft [CABG] surgery) conferred any mortality benefit before elective major vascular surgery (either AAA repair or arterial occlusive disease of the lower extremities). Five hundred patients with stable cardiac symptoms and known coronary artery disease were randomized to either receive coronary revascularization, followed by elective vascular surgery, or proceed directly to the planned vascular surgery. The study measured mortality up to 2.7 years after randomization and found no significant difference in mortality between the two groups. Both groups also had equivalent rates of postoperative myocardial infarction (within 30 days of surgery). Based on these findings, it is generally recommended to proceed directly with vascular surgery in patients with stable coronary artery disease.
Reference:
A 63-year-old female who initially presented to the ED with chest pain radiating to her back was found to have a Stanford type B (descending only) aortic dissection and was admitted to the ICU for acute medical management. Her urine output is adequate (1 mL/kg/min), is neurologically intact, and has normal metabolic laboratories. To decrease the shear stress on her aortic dissection she was started on IV metoprolol and IV labetolol with good initial results. Her heart rate is 60 bpm, her blood pressure is 110/70, and she is pain-free.
On her third ICU day she develops increasing pain and becomes progressively more hypertensive with BP 150/90, on metoprolol and labetolol. Considering her worsening condition, what course of therapy has been shown to most improve her overall survival?
Correct Answer: B
Type B aortic dissections that demonstrate a good response to medical therapy alone with alleviation of pain and heart rate below 60 and systolic blood pressure between 100 to 120 are classified as uncomplicated. Typically, patients with uncomplicated dissections are medically managed with beta blockers and antihypertensive agents to decrease the shear forces on the aortic wall and prevent further dissection. Optimal medical management is associated with a 90% to 99% long-term survival in this patient group.
Refractory pain or worsening hypertension in patients with uncomplicated type B aortic dissection denotes failure of medical management. Worsening pain may indicate progression of the dissection flap, and worsening hypertension may be due to renal malperfusion from an extending dissection. In this case, the type B dissection should then be classified as a complicated dissection. Continued medical management alone in this patient group is associated with significantly increased mortality (approximately 30%-40% in-hospital mortality compared with 1%-2% in-hospital mortality in patients with uncomplicated dissections).
Patients with complicated dissections should be treated with surgical intervention to halt further dissection of the aorta. Traditionally this was performed via an open surgical approach, but the in-hospital mortality associated with open repair has remained consistently high, around 20% to 30% since the first operation of this type was performed. Conversely, endovascular repair of type B aortic dissection is associated with a much lower in-hospital mortality of approximately 3% to 10%. Therefore, to give this patient the best chance of survival, an endovascular repair of her complicated type B aortic dissection should be performed.
References
You are called to the ED to evaluate a 54-year-old female who presented with sudden onset chest pain, which began while exercising at the gym, described as “tearing,” with radiation to her upper back. She is a former smoker with a history of hypertension, hyperlipidemia, and diabetes. On presentation her heart rate is 112 and blood pressure is 182/93; she is taking shallow breaths at 18 and her oxygenation saturation is 98% on 2 L NC. Physical examination is significant for a middle-aged woman, mildly diaphoretic, with a diastolic, decrescendo murmur, best heard at the left upper sternal border, and equal breath sounds with crackles at the bases. Chest CT shows an aortic dissection originating in the ascending aorta.
What is the next best step in her management?
Correct Answer: D
This patient has clear evidence of type A aortic dissection with high risk features, which will require immediate surgical intervention. While awaiting definitive treatment, your priority must be to reduce the risk of dissection propagation by decreasing shearing forces. This is best achieved by controlling heart rate (goal 60-75 bpm), decreasing contractile force and lowering blood pressure. Although Nitroprusside will lower this patient’s blood pressure, it may lead to reflex tachycardia and should only be started once heart rate control has been achieved with an easily titratable agent such as Esmolol. If the patient had been unstable and inappropriate for transport to the CT scanner, a transesophageal echo would have been an acceptable alternative imaging modality, but given that you already have evidence of a type A dissection in a patient with high-risk features, no further imaging is necessary. Given this patient’s presentation, part of your initial assessment should have been to differentiate between acute coronary syndrome and aortic dissection. Had the question indicated that the EKG was consistent with a STEMI, a consult to cardiology for emergency revascularization therapy would have been appropriate. However, given the need for immediate surgical invention in this case, a consult to CT Surgery is needed.
References:
A 72-year-old male was brought into the ED with crushing substernal chest pain while mowing his lawn with EKG changes showing T-wave inversions and elevated serum troponins. His symptoms resolve with sublingual nitroglycerin, and he is hemodynamically stable throughout his workup. He undergoes cardiac catheterization shortly thereafter and is found to have multivessel coronary artery disease and is scheduled for coronaryartery bypass graft (CABG) surgery with the use of cardiopulmonary bypass (CPB) (on-pump) the next day. He is admitted to the ICU on a heparin infusion for closer monitoring.
Which of the following statements is correct with regard to off-pump versus on-pump CABG?
CABG surgery can be performed both without and with CPB for multivessel coronary artery disease. Although CPB with cardioplegia is thought to provide optimal surgical conditions for coronary anastomoses, off-pump CABG avoids the many negative consequences of subjecting the human body to CPB. There have been numerous well-designed multicenter randomized control trials comparing the two methods. The four largest clinical trials to date comparing the two methods include CORONARY, DOORS, GOPCABE, and ROOBY included more than 10 000 patients in total looking at outcomes up to 5 years from surgery. In 2012, a Cochrane Review showed that off-pump CABG is associated with increased all-cause mortality versus on-pump CABG. Although on-pump CABG shows improved mortality benefit, there are cases necessitating off-pump CABG, and it is ultimately an individual decision based on surgeon preference and a discussion with each patient.
A 59-year-old male who underwent an aortic valve replacement for congenital bicuspid aortic stenosis is admitted to the ICU post-op. The case went well, with a short bypass and cross-clamp time, minimal blood loss, and no blood products given. At the end of the case, an intraoperative TEE showed good biventricular function and a small amount of air in the apex of the left ventricle. For medications during the case, the patient received 1500 µg fentanyl; 100 mg of Propofol for induction; 100 mg of rocuronium, heparin, and protamine for bypass; and tranexamic acid for antifibrinolysis, and he was placed on dexmedetomidine post-op for sedation in the ICU.
He was extubated without difficulty 5 hours after his arrival from the operating room. Shortly after extubation, he had a witnessed generalized myoclonic seizure. The seizure was terminated within a few minutes after one dose of intravenous lorazepam. A stat head CT was obtained, which was read as normal with no acute changes. He was seen by neurology and had no further seizure activity throughout his hospital stay. Other than air from the surgical procedure, which of the following medications that the patient received are most likely associated with postoperative risk of seizure?
Tranexamic acid (TXA) is an antifibrinolytic drug that binds to plasminogen and blocks the interaction of plasmin with fibrin, thereby stabilizing the fibrin clot. TXA is a lysine analog and crosses the bloodbrain barrier and is thought to affect the central nervous system (CNS) by competitively binding to GABA-A receptors in a dose-dependent fashion. GABA-A receptors, which function in inhibition of CNS transmission, are thereby blocked, resulting in decreased inhibitory activity and increased neuronal excitation in the brain.
In a meta-analysis of seizure risk associated with TXA use in open chamber cardiac procedures, the cumulative incidence rate of seizures was 2.7%, which was much higher than the average 1% risk when TXA was not used. Because TXA inhibits GABA-A in a dose-dependent fashion, the incidence of seizures was shown to increase from 1.4% in the low-dose (25- 50 mg/kg) range, to 2.4% incidence in a middle dose of approximately 60 mg/kg, up to an incidence of 5.3% in the high-dose (80-110 mg/kg) range.
Note that propofol can cause myoclonus but is very unlikely to produce actual seizure activity. Fentanyl has been associated with seizures, but this is more typically seen with intrathecal use, and dexmedetomidine is also highly unlikely to affect the seizure threshold. Neuromuscular blocking agents such as rocuronium have no effect on seizure activity.
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