The clinical diagnosis of fat embolism

Abstract

F AT embohsm can be defined as the introduction of Iiquid fat into the circmation and its transportation by the bIood stream to occIude the finer bIood vesseIs in various parts of the body. This condition is a frequent resuIt of fractures of the long bones or any other trauma which is associated with damage to adipose tissue. In the majority of cases only an insignificant grade of fat emboIism is produced by the types of injury mentioned. In a few instances, however, especiaIIy when the Iong bones of the Iower extremity are fractured, a Iarge quantity of fat may gain access to the bIood vesseIs and so interfere with the bIood suppIy of the vita1 organs that death resuIts. In most fractures of the Iong bones three factors are present which promote the deveIopment of fat emboIism. They are: (I) The destruction of fat ceIIs in the bone marrow and in the surrounding intermuscuIar tissues so that a Iarge amount of Iiquid oi1 is produced. (2) The tearing of the venuIes in the Haversian canaIs of the bones which cannot coIIapse readiIy because of the rigid waIIs in which they are encased. (3) A mechanism such as muscular spasm or manipuIation of the broken bones which increases interna pressure in the region of the fracture and so favors entrance of the fat into the veins. In the majority of fractures of the Iower extremities (80 per cent) the processes of repair are effective and prevent the entrance of any considerabIe quantity of fat into the bIood stream. For this reason, serious cases of fat emboIism are not common and when they occur it is probable that mechanica interference with the broken bones has interfered with the processes of repair.’ The way in which fat emboIism deveIops in the human subject is not known in a11 its detaiIs. Many have the conception that the fat enters the bIood as a coherent coIumn of oi1 which bIocks the puImonary artery and causes immediate asphyxia. This eventuaIity may occur in rare instances, but in the vast majority of cases it is more probabIe that the fat is forced into the veins at intervaIs as insuIts of various sorts are offered to the injured extremity. Symptoms are produced when sufficient emboIi accumuIate in the Iungs to impede the pulmonary circuIation. CIinicaIIy the serious and fatal cases of fat emboIism are separated into two types: I. Pulmonary Fat Embolism. In this type the fat is transported through the veins, the right heart, the puImonary artery, and finaIIy Iodges in the arterioIes and capiIIaries of the lungs. The flow of the puImonary circuIation is impeded and the patient shows signs of asphyxia. 2. Systemic or Cerebral Fat Embolism. In this type the fat emboIi in the puImonary capilIaries are forced by pressure in the right side of the heart into the puImonary veins, the Ieft side of the heart, and the aorta, whence they are distributed a11 over the body. Most of these emboIi reach the brain and cause definitedamage of the brain substance. Because of this the patient deveIops a coma which becomes deeper and deeper unti1 his death.