The Case A 61-year-old male with a long-standing smoking history, nephrolithiasis, D2M, HTN, and HLD presents to the ED with recurrent 10/10 non-radiating periumbilical pain. The patient had presented one day prior with two episodes of vomiting and abdominal pain “after eating McDonald’s.” The patient had resolution of pain after being treated with ketorolac and morphine. All of his labs (CBC, CMP, lipase, troponin) were unremarkable. In addition, the UA from the first visit and renal ultrasound were both normal. The discharge diagnosis at that time was unclear – possibly dyspepsia or a passed kidney stone.
Physical Exam HR 91/min, BP 189/107 mm Hg, T 99.4 F, RR 18/min, SpO2 100% RA The patient was prone on the stretcher, noting that the only relief he experienced was with the edge of the stretcher pressing into his abdomen. The exam was otherwise notable for agitation and pallor. Chest was clear, and the rhythm was regular. There was periumbilical tenderness and an abdominal mass. Radial and dorsalis pedis pulses were 2+. Differential Diagnosis At this point, the differential included obstruction, mesenteric ischemia, ACS, gastritis, nephrolithiasis, diverticulitis, urinary retention, and a range of other less likely diagnoses. Aortic dissection was considered, but lower on the differential given the overall prevalence of the disease (at most, 30 cases per 1,000,000) and the absence of other typical aortic dissection symptoms – radiation to the back, “tearing” pain, wide pulse pressure, loss of peripheral pulses.1 Given the intensity and quality of the pain and the fact that this was the patient’s second ED visit in three days, there was concern for significant intra-abdominal pathology. Work up ECG Normal sinus rhythm, normal axis, normal intervals; +unifocal PAC, poor R progression with flattened T waves in all leads; no ST-elevations or depressions. Lab Results There was leukocytosis of 14. CBC, CMP, troponin, and UA were normal. Imaging A CT abdomen/pelvis with contrast was ordered and when the dissection flap was identified, a CTA chest, abdomen, and pelvis promptly followed. The clip below is from the CTA. Full radiology read: Fusiform infrarenal abdominal aneurysm with dissection flap, measuring 5.3 cm in diameter. Fenestrated dissection flap with no evidence of aortic wall thickening, intramural thrombus, or hematoma. No findings to suggest mycotic aneurysm. No findings of SBO. Diverticula without diverticulitis. Hospital Course Vascular surgery consult was unimpressed with the size of the aneurysm, considered the dissection flap an incidental finding, and urged the team to continue to consider alternative causes for the pain. Constipation was considered, but the CT did not show a large stool burden. Ureterolithiasis was a consideration, but there was no hydronephrosis or calculus on CT, and the pain seemed to be progressive and evolving in nature, not quite consistent with renal colic. Finally, could it have been UTI or other GU abnormality? The urine was negative for bacteria, leukocyte esterase, nitrites, and blood. Bladder catheterization yielded 500 cc of clear urine, and a bedside US did not show acute urinary retention or prostatic mass. The concern for acute aortic dissection was now highest, so the patient was given morphine and started on esmolol and nicardipine infusions. After much discussion and escalation among the various services, the patient was admitted to the SICU under vascular surgery for aggressive hemodynamic control, further monitoring, and consideration of definitive management. ED Management Bedside Ultrasonography AAA was not initially considered, so bedside ultrasound was not completed prior to CT, but it is an important component of ED management. Bedside US has a sensitivity of 67-80% for abdominal aortic intimal flap visualization and a specificity of 99-100%.2 Ultrasonography may be a useful tool in male patients > 50 years of age with severe abdominal pain. Ultrasound image of 5.62cm abdominal aortic aneurysm Medical Management Regardless of whether your patient is going to the OR, start medical management immediately. We won’t dwell on medical management too much as this is a heavily-covered topic in EM literature and FOAMed: see this EMCrit post and this emDOCs post for more information. After notifying your surgeon, consider placing an arterial line for more accurate blood pressure monitoring. If the dissection involves the left subclavian artery, a right radial arterial line is preferred over the left, as the left radial a-line may reflect falsely low blood pressures. If the dissection is purely a type B dissection, some literature suggests avoiding the placement of femoral a-lines as the cannulation could precipitate worsening of the dissection with end-organ malperfusion3. Achieve goals of therapy through: 1.Pain control → Pain = higher HR and BP 2. Beta blocker (to manage HR primarily; negative inotrope/chronotrope) → Esmolol drip5 (onset: 2-10 min, duration: 10-30 min, easily titratable) 3. Calcium channel blocker (add BP still > 110 mm Hg after rate control): reduces afterload → Nicardipine drip (onset: 5-15 min, duration 4-6 hours) Which aortic dissections need surgery? Although it is not the ED team’s decision whether to take a patient with dissection to the OR, it is vitally important for us to be familiar with the indications, so we can effectively advocate for our patients as needed. Management of aortic dissections differs depending on whether they are acute or chronic and where they are located. Dissections that are acute (diagnosed within 2 weeks), have signs of impending rupture and involve the ascending aorta are treated surgically. All other types of dissections are treated medically with close monitoring. The implications of missing an acute dissection can be catastrophic as acute dissections leading to rupture have a mortality of 50% within the first 48 hours.6 This patient’s CT had some findings concerning for an acute dissection–namely, there was no evidence of a mural thrombus. Over time, as the intimal layer of the aorta tears away from the medial layer, the exposed and damaged tissue causes clot to form.7 This is more of a chronic and stable process. A mural thrombus can also be protective against rupture as it allows collagen to form and reinforce the weakened wall.8,9 Other findings suggestive of a chronic process include false lumen outer wall calcification and a false lumen that is greater in size than the true lumen. Calcification, in general, is a chronic process. The second point, however, can use some explanation. After a dissection flap is created, shear forces are now flowing through both the true and false lumens, further separating the already weak intimal dissection flap from the medial layer, allowing the false lumen to expand.7 Our patient had neither of these more chronic findings on CT. Although aneurysm formation independently can be a chronic process, dissection within an aneurysm suggests impending rupture. As blood fills the true and false lumens, hemodynamic forces against the now weakened wall cause it to balloon outwards, forming an aneurysm. The constant shear forces against the weakened aneurysmal outer wall can then lead to rupture. A dissection with an aneurysm size of 5.5 cm or more is an indication for immediate operative management (our patient’s aneurysm was borderline at 5.3 cm).6,10 Finally, sudden onset of abdominal pain in the setting of a newly diagnosed dissection that cannot be explained by another process is termed a “symptomatic dissection” and should be managed surgically, even in the absence of other worrisome features.6 In other words, even if our patient did not have an associated aneurysm or dilated false lumen, the sudden and intractable pain alone may be enough to necessitate surgery. It was also suggested that dissection flaps within aneurysms are painless. There is no literature commenting one way or another and may have been the particular surgeon’s very legitimate personal experience. Conclusion Given the findings on CT suggestive of acute etiology and the patient’s acute, refractory quality of the pain (“symptomatic aneurysm”), the patient was transferred to a specialized center for endovascular aortic repair (EVAR) with transfemoral stent placement over the site of the dissection. Take Home Points »There is no reliable way to determine acute vs chronic dissection; however, false lumen calcification, a dilated false lumen, and an intramural thrombus are features suggestive of chronicity. »A few signs of impending rupture include intractable pain, associated aneurysm > 5.5 cm, and para-aortic stranding. »Goals of treatment include HR < 60/min and SBP < 110 mm Hg. Start treatment if your suspicion is high, even if you are still waiting for the consult service. »Start medical management with a beta-blocker for rate control, then add on a calcium channel blocker for afterload reduction. References 1Levy D, Le JK. Aortic Dissection. [Updated 2019 Dec 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441963/ 2Fojtik JP, Costantino TG, Dean AJ. The diagnosis of aortic dissection by emergency medicine ultrasound. J Emerg Med. 2007;32(2):191-196. 3Harrington DK, Ranasinghe AM, Shah A, Oelofse T, Bonser RS. Recommendations for haemodynamic and neurological monitoring in repair of acute type a aortic dissection. Anesthesiol Res Pract. 2011;2011:949034 4Suzuki T, Eagle KA, Bossone E, Ballotta A, Froehlich JB, Isselbacher EM. Medical management in type B aortic dissection. Ann Cardiothorac Surg. 2014;3(4):413-7. 6Vu KN, Kaitoukov Y, Morin-roy F, et al. Rupture signs on computed tomography, treatment, and outcome of abdominal aortic aneurysms. Insights Imaging. 2014;5(3):281-93. 7Orabi NA, Quint LE, Watcharotone K, Nan B, Williams DM, Kim KM. Distinguishing acute from chronic aortic dissections using CT imaging features. Int J Cardiovasc Imaging. 2018;34(11):1831-1840. 8Spinelli D, Benedetto F, Donato R, et al. Current evidence in predictors of aortic growth and events in acute type B aortic dissection. J Vasc Surg. 2018;68(6):1925-1935.e8. 9Schriefl AJ, Collins MJ, Pierce DM, Holzapfel GA, Niklason LE, Humphrey JD. Remodeling of intramural thrombus and collagen in an Ang-II infusion ApoE-/- model of dissecting aortic aneurysms. Thromb Res. 2012;130(3):e139-46. 10Chaikof EL, Dalman RL, Eskandari MK, et al. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018;67(1):2-77.e2.
Goals of Therapy4:
Reduce shearing force (dp/dt):
• HR < 60/min
• SBP < 110 mmHg
→ Fentanyl or another opioid as needed
→ Loading dose: 500 mcg/kg IV bolus over 1 min (can repeat bolus one time according to the manufacturer, but institutional protocols differ)
→ Infusion: 50 mcg/kg/min, titrate by 50 mcg/kg/min q4 min; max: 300 mcg/kg/min;
→ Resident tips: if up-titrating, you need to repeat the IV bolus at least once (but up to three times, depending on your institutional protocol).
→ Infusion 5 mg/hr, titrate by 2.5mg/hr q5min; max: 15 mg/hr
→ Resident tips: Nicardipine and esmolol can be given through the same line.
→ Contraindication: Severe aortic stenosis.
5Pevtsov A, Kerndt C, Fredlund KL. Esmolol. [Updated 2020 Feb 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK518965/
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