Cause of death and mechanism of pulmonary fat embolism
It was clear that the patient died from pulmonary fat embolism according to the diagnostic criteria of pulmonary fat embolism, with samples evaluated at 100 × magnification[1]. There were fat emboli with antler-like configurations that were clearly visible and abundant in all regions of the lungs. There was no sample without fat emboli, indicating degree Ⅲ embolism (massive fat embolism)[1]. The author believes that the specific cause and mechanism of fat embolism warrant attention in this patient. There were more than 30 pinholes in her lower back, and we calculated that the silver needle used for acupuncture was 1.1 mm in diameter; thus, the total area of damaged fat tissue was approximately 0.2851 cm2. However, fat components in some blood vessels of various organs besides the lungs, such as the liver, heart, spleen and thyroid gland, indicated that there was a substantial amount of circulating fat. Hence, it is believed that the cause of death in this case was severe nontraumatic pulmonary fat embolism, which was made on the basis of the pathology findings, including obesity, multiorgan adipose tissue hyperplasia and stress triggered by silver-needle acupuncture. The mechanism of nontraumatic pulmonary fat embolism is a neuroendocrine effect that leads to an increase in catecholamine secretion, which releases a large amount of peripheral fat into the blood, resulting in an unstable lipid emulsification state, chylomicron agglutination and finally blockage of the interstitial vessels in the lungs[20–22].
Prevention of pulmonary fat embolism as a complication
The adipose tissue damage caused by silver-needle acupuncture was not a risk factor for pulmonary fat embolism. In practice, acupuncture is part of the healing system of traditional Chinese medicine (TCM) and is widely used in many countries throughout the world for pain relief in the neck, shoulders and lower back[23, 24]. Silver-needle acupuncture, as a kind of complementary and alternative medicine (CAM), is a unique branch of acupuncture[25, 26] and has not previously been associated with pulmonary fat embolism. In the clinic, death from fat embolism is not uncommon, as it is a complication of minor trauma, surgery, or other treatments, and thus should be given adequate attention. However, in the event of pulmonary fat embolism, patients present with atypical manifestations (Table 1), making diagnosis and treatment difficult. For example, in this case, the patient developed dizziness immediately after silver-needle acupuncture treatment and heart failure 2 hours later, without a series of manifestations associated with pulmonary fat embolism, such as dyspnea, chest pain and hemoptysis. It should be noted that the patient had signs of respiratory insufficiency, cerebral dysfunction, and skin ecchymosis[20, 21, 27]. Evidently, ageing, obesity, underlying diseases, mental status and irritation due to treatment protocols may be risk factors for stress-induced pulmonary fat embolism, so the choice of treatment must be in strict accordance with the indications and contraindications, and the patient should be closely observed for any related clinical manifestations to reduce the occurrence of complications and adverse events[23]. This case suggests that when the patient's condition suddenly deteriorates or respiratory insufficiency develops after physiotherapy to relieve pain, such as acupuncture, the possibility of pulmonary fat embolism should be considered, and a prompt diagnosis and treatment should be provided.
Differential diagnosis of fat embolism source
This was a very interesting case of pulmonary fat embolism that was suspected to be due to stress. In fatal posttraumatic pulmonary fat embolism caused by subcutaneous soft tissue contusion, there are no uniform criteria regarding the area of the damage or the extent of the injury.
Moreover, in fatal pulmonary fat embolism cases, the soft tissue contusion area generally affects 30–35% of the body surface[27, 28]. Some studies have also shown that fat compression in different body regions can range from 20 cm2 to 21–70 cm2[2]. In this case, based on the isolated puncture injuries on the skin, the nature of the adipose tissue injury was wounds formed by needle pricks and peripheral bleeding due to ruptured vessels and blood infiltration, not soft tissue contusions. In addition, the degree (about 0.2851 cm2 by 30 pinholes) of adipose tissue damage in this case was very low and far from the degree of adipose tissue damage noted in previous reports.
Those performing postmortem autopsy and histopathology examinations of patients who died of suspected of pulmonary fat embolism should take into account whether there was a history of trauma, and the degree of adipose tissue damage should be assessed. Significantly minor adipose tissue injury in the presence of trauma is an indication of death from nontraumatic pulmonary fat embolism. Examinations of sites for fat emboli should include each major organ[3] as well as the peripheral arterial system and the venous system draining from noninjured sites to identify the possible source of the fat embolus. It has been reported that biochemical testing of the deceased's cardiac blood should be performed, with attention to abnormal changes in VLDL, cholesterol, TG, FFA, and CRP[3]. Lipid analysis of fat emboli, if necessary, may also be performed, which may suggest a possible mechanism of pulmonary fat embolism formation[4]. Moreover, attention should be paid to individual factors and subclinical conditions, such as obesity, multiple organ adipose hyperplasia and other condition, that may be risk factors for nontraumatic fat embolism[3].
There are some limitations in this report, including the availability of clinical examination results for the patient before and after silver-needle acupuncture; this prevented us from knowing the full extent of the patient’s underlying diseases and collecting fresh tissue from additional organs for Sudan III staining. We report a case of nontraumatic pulmonary fat embolism resulting in death following acupuncture, which has not been reported previously. Despite this case, acupuncture therapy is not considered to be a dangerous; however, the major risk factors for nontraumatic pulmonary fat embolism need to be emphasized in relation to similar treatments.