Most trauma professionals have heard of OPSI, but few have ever seen it. The condition was first described in splenectomized children in 1952. Soon after, it was recognized that this infection occurred in asplenic adults as well.
OPSI is principally due to infection by encapsulated organisms, those with a special polysaccharide layer outside of the bacterial wall. This layer is only weakly immunogenic, and confers protection from the normal immune mechanisms, particularly phagocytosis. However, these bacteria are more easily identified and removed in the spleen.
OPSI may be caused by a number of organisms, the most common being Strep. pneumonia, Haemophilus influenza, and meningococcus. For this reason, the standard of care has been to administer vaccines targeting the usual organisms to patients who have lost their spleen.
How common is OPSI? A recent paper from Gernany reviewed comprehensive data from 173 intensive care units over a 2-year period. Here are some of the more interesting factoids:
- 2,859 ICU beds were screened, but the number of unique patients was not given. This is very disappointing because incidence cannot be calculated!
- 52 cases of OPSI occurred
- Only half of the patients had received vaccines
- Pneumococcus was the most common bacterium (42%). There were no H. Flu or meningococcal infections.
Bottom line: Yes, OPSI exists and can occur in your asplenic patients. It is uncommon enough that you and your colleagues will probably never see a case. But proper vaccination remains important. Papers consistently show that we are collectively not very good at ensuring that our splenectomized patients receive all their vaccines, ranging from only 11-50%. We collectively need to make better efforts to provide them to our at-risk patients.
Reference: Overwhelming Postsplenectomy Infection: A Prospective Multicenter Cohort Study. Clin Infec Diseases 62:871-878, 2016.
The current standard of care is to vaccinate patients after splenectomy to prevent overwhelming post-splenectomy sepsis (OPSS). The real questions are, is this reasonable and is it needed after splenorrhaphy or angioembolization, too?
The spleen was recognized as contributing to infection resistance in the early 1900s. A study on post-splenectomy sepsis that has been widely quoted was published in 1952. Unfortunately, the children involved all had hematologic disorders, so it is difficult to determine if their sepsis deaths were due to splenectomy or their underlying disease.
Reports of sepsis and death continued to accumulate in the latter half of the last century, but there was a tremendous amount of overlap in patient cases. Richardson reviewed the world literature to date and found that, as of about 2003, there were roughly 70 total cases worldwide since the beginning of time, with a death rate of about 30%. Basically, there are more published papers and reports on death from OPSS than there are actual cases!
This flawed data directed a push toward splenorrhaphy and then to nonoperative management of splenic injury. Guidelines have been developed and revised that suggest that the following vaccines should be given to patients with splenectomy:
- Pneumovax 23 – .5cc SQ, booster every 6 years
- Haemophilus B conjugate – .5cc IM, no booster
- Meningococcal vaccine (polysaccharide or diphtheria conjugate) – .5cc (route depends on vaccine), booster status unclear
There is no good data at all on vaccine administration after angioembolization. Animal studies suggest that at least 50% of the spleen must be perfused by the splenic artery in order to maintain immune competence. Patients who have CT or angiographic evidence that a significant portion of the spleen is not perfused should probably undergo vaccination.
Given the rarity of OPSS and the even lower probability of dying from it, a definitive study regarding the usefulness of spleen vaccine administration will never be done. So we are stuck with giving them in spleen-injured or spleen-free patients even though the usefulness can never be proven.
Reference: J David Richardson. Managing Liver and Spleen Injuries. J Am Col Surg 200(5):648-669, 2005.