Hib vaccine prevents meningitis, pneumonia, epiglottitis, and other serious infections caused by the Hib bacterium. It is usually injected into the deltoid muscle. According to the guidelines for Hib vaccination from the Center for Disease Control, common adverse reactions include swelling, redness, and pain; systemic reactions such as fever and irritability are infrequent, and serious reactions are rare. In a report on adverse events after Hib vaccination, other outcomes included pyrexia, vomiting, convulsions, irritability, intussusception, diarrhea, crying, hypotonia, lethargy, and apnea . Pseudoaneurysm as an adverse reaction associated with Hib vaccination has never been reported.
Aneurysm refers to the weakening of an artery wall that creates a bulge or distention of the artery. Most aneurysms are asymptomatic and are not dangerous. At their most severe stage, however, some can rupture, leading to life-threatening, internal bleeding. Aneurysms occurring in children are rare and usually occur in the thoracic or abdominal aorta . Nonaortic arterial aneurysms in children are rarer and have been associated with neurofibromatosis , Kawasaki disease , periarteritis nodosa , and giant cell arteritis .
Pseudoaneurysm is a collection of flowing blood that communicates with the arterial lumen and is filled only by the adventitia or surrounding soft tissue. It is a known complication of penetrating arterial injuries such as catheterization, gunshot wounds, and fractures . It may take days, months, or even years to become symptomatic or be detected clinically. Symptoms are usually limited to the mass effect of the lesion and can include tenderness, pain, and swelling. Complications related to peripheral artery pseudoaneurysm include local pain, rupture, neuropathy, local limb ischemia, and even limb loss . In medical practice, iatrogenic arterial injury should be avoided as much as possible to reduce the occurrence of serious complications such as pseudoaneurysm. Although vaccination does not typically affect the arteries, the operator’s knowledge of the anatomy of the vaccination site is still important. In particular, because infants are small, the distance between the brachial artery and the deltoid muscle is relatively short. Therefore, it is necessary to strengthen the technical training of vaccination operators to avoid related iatrogenic injuries.
Pseudoaneurysm can be diagnosed via Doppler ultrasonography, computed tomography angiography, DSA, and magnetic resonance angiography . Doppler ultrasonography can reveal the presence of blood flow or thrombi within the pseudoaneurysm, the size of the neck of the pseudoaneurysm, the integrity of adjacent vessels, and the presence of loculations. Moreover, it is a useful modality during patient follow-up after treatment because it is rapid, convenient, and inexpensive. Computed tomography angiography and DSA can depict the vasculature in different ways, but intravascular contrast medium is required. Magnetic resonance angiography is also a preferred method for diagnostic evaluations of pediatric vascular diseases due to its high image resolution, lack of arterial invasion, and absence of radiation exposure. However, it is comparatively expensive and inconvenient.
Pseudoaneurysm treatments include conservative measures, sonographically guided compression, embolization, and open surgery. Sonographically guided compression was introduced in 1991 and involves the placement of an ultrasound probe directly over the neck of the pseudoaneurysm in conjunction with the application of prolonged compression, thereby producing vascular stasis within the lumen and promoting thrombosis . Although it is noninvasive and its success rate is approximately 90%, the procedure is often painful for patients and uncomfortable for operators, time-consuming, and occasionally unsuccessful . Sonographically guided thrombin injection was used extensively after its introduction in 1997 because of its high success rate, minimal patient discomfort, and immediate results. It involved percutaneous injection of thrombin into the lumen under sonographic guidance. Although success rates ranged from 91 to 100%, the fear of embolic and thrombotic complications hindered the primary use of this method . It was suggested that compression should be used as the first-line treatment and that thrombin injection should be reserved as a backup. Open surgery includes resection, ligation, reanastomosis, or vein graft interpositioning .
Vein graft interpositioning was preferred in the current case due to the size and rapid expansion of the pseudoaneurysm. Fortunately, the operation was performed in time, which enabled the squeezed median nerve to be released, thus avoiding further damage. Long-term follow-up indicated that the surgery was effective and without obvious complications.
In the present case, preoperative image reports, intraoperative surgical findings, and postoperative pathological examination all confirmed the existence of brachial pseudoaneurysm. Because the infant did not suffer from any hereditary disease and had not experienced any other iatrogenic or traumatic injury, we speculated that vaccination into the deltoid muscle had accidentally punctured the brachial artery, leading to the formation of a pulsative mass 10 days later. Although rare, this can happen, resulting in pseudoaneurysm. Fortunately, the surgery was timely; otherwise, sensory and motor dysfunction could have occurred while the median nerve was severely squeezed. The infant recovered well with no complications.
Herein, we have described a case of brachial artery pseudoaneurysm formation after vaccination in an infant, in whom resection of the pseudoaneurysm and vein graft interpositioning were successful. We emphasize that although vaccination can rarely lead to pseudoaneurysm, it is mostly safe. Efforts must be made to avoid such complications during vaccination.