Pulmonary embolism

Abstract

CONFIDENCE in modern techniques of post-operative management and the increasing variety and magnitude of surgical interventions has caused an increased incidence of post-operative pulmonary embolism and infarction, but analysis of reported incidence indicates clearly that this is not the only factor; reports from countries devastated by the two world wars shows that the incidence falls significantly during and immediately after such a national disaster. This decrease in incidence can be related directly to the economic status of the population at risk, and is reversed when the nutritional state rises and, in particular, with the rise in the consumption of fats and proteins. There is also suggestive, but not conclusive evidence of a seasonal variation.Morrell, Truelove and Barr (1963) showed that there was a five-fold rise in incidence from 1952 -1961 in two hospitals under review, with a four-fold rise in mortality rate. In patients in medical wards, pulmonary embolism is an appreciable risk over the age of thirty, and the incidence rises sharply over the age of fifty; in surgical wards, the risk is very low below the age of forty, and rises less sharply after the age of fifty. In the two hospitals studied they found that a potentially preventable death occurred once every two weeks. Phear (1960) was able to collect and analyse 168 cases over a three-year period, from one hospital. His conclusions are important and will be referred to again. The EtiologyOf all the factors of etiological significance in thrombo-embolism none appears more important than the limitation of normal activity imposed either by the patient's disease or by the restrictions of out-dated hospital discipline. The reduction of systemic venous flow, together with trauma doubtless forms the broad base upon which all thrombo-embolic phenomena depend. Failure of early post-operative ambulation to control embolism is probably largely due to the failure to recognise pre-operative thromboses. About half the patients who die after a variable period of confinement to bed demonstrate deep venous thromboses unsuspected in life. The majority of emboli originate in the intramuscular veins of the legs, and these veins enlarge with age. The physiological increase in platelet stickiness, which is a normal response to injury, must also be a factor, apart from such obvious ones as haemoconcentration and sludging in the micro-circulation due to dehydration and a reduced cardiac output. The DiagnosisAs long ago as 1934 Churchill stated "the very fact that the event is so unexpected and tragic has coloured the observations with inaccuracies, and it is exceedingly difficult to find an adequate analysis of what really took place." In the major episode signs of infarction are very unusual, occuring only in 10 % of cases, and signs of phlebitis are only found in 15% of cases. It has also been said that in cases operated on for pulmonary embolism the diagnosis has been wrong in more than 60%.