Tag Archives: splenectomy

Abdomen

Spleen Vaccines: So Confusing! – Part 2

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Who needs to get these vaccines? Obviously if your patient’s spleen was surgically removed, they should get it. But what about patients who underwent angioembolization? Unfortunately, the only data available is either very old or is based on antibody response to the vaccine. And antibody titers do not predict immunity to infection, so these studies are close to meaningless.

Old research showed that the spleen’s immune function was preserved as long as 50% of its blood flow was delivered through the splenic artery. How can you tell if half of the spleen is still functioning after splenic angioembolization? Look at the images and make an educated guess. If in doubt, vaccinate.

When is the best time to vaccinate? There has been much gnashing of teeth regarding early vs late vaccination. The arguments against early vaccination center around the typical immune suppression seen with major trauma. However, trauma patients frequently do not appear for all their followup visits and would not receive vaccines at all if they are a no-show. So I recommend vaccinating as early as possible during the hospital stay to avoid forgetting. The data recommending waiting until just before discharge are also based on antibody titers, and I don’t buy it.

Bottom line: I’m not an epidemiologist. But making a set of vaccination rules more complicated for a complex population seems unwise. Especially since the added vaccine offers protection for only one more serotype of Pneumococcus.

But I can’t argue with the FDA and CDC. I have no idea of the wheeling and dealing that occurred to get the new vaccine approved. All we can do is follow the recommendations the best we can, and try to remind our patients to get that Pneumovax and meningococcal conjugate booster five years down the road. Good luck with that.

Abdomen

Spleen Vaccines: So Confusing! – Part 1

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Earlier this year, there were a lot of television commercials for Prevnar 13, a 13-valent pneumococcal vaccine for immun-ocompromised or asplenic adults. And interestingly, I noticed that the CDC has added a recommendation that these patients receive this vaccination, followed by the original 23-valent vaccine (Pneumovax 23) 8 weeks later.

WTF? Patients with splenectomy (or significant angio-embolization) for trauma are considered functionally asplenic. And although the data for immunization in this group is weak, giving triple vaccinations with pneumcoccal, H. flu, and meningococcal vaccines has become a standard of care.

This was difficult enough already because there was debate around the best time to administer: during the hospital stay or several weeks later after the immune system depression from trauma had resolved. The unfortunate truth is that many trauma patients never come back for followup, and so don’t get any vaccines if they are not given during the hospital stay.

And then came the recommendation a few years ago to give a 5-year booster for the pneumococcal vaccine. I have a hard time remembering when my last tetanus vaccine was to schedule my own booster. How can I expect my trauma patients to remember and come back for their pneumococcal vaccine booster?

So what do we do with the CDC Prevnar 13 recommendation? If we add it, it means that we give Prevnar while the patient is in the hospital, and then hope they come back 8 weeks later for their Pneumovax. And then 5 years later for the booster dose. Huh?

Looking at the package insert, I read that Pneumovax 23 protects against 23 serotypes of S. Pneumo, which represent 85% of most commonly encountered strains out there. So it’s not perfect. Prevnar 13 protects against 13 serotypes, and there is no in-dication as to what percent of strains encountered are protected against.

So I decided to dig deeper and look at the serotypes included in each vaccine. They are shown in the chart below. The 23 bars with maroon in them (solid or striped) are Pneumococcal serotypes covered by Pneumovax 23. The 13 bars containing gray are ones covered by Prevnar 13. There is only one serotype in Prevnar 13 not covered by Pneumovax 23, serotype 6A. Unfortunately, it’s nearly impossible to find the prevalence of infections by serotype, and it varies geographically and over time anyway. So does cover-age of a single extra serotype by Prevnar 13 justify an additional vaccination and complicated administration schedule? Hmm.

It turns out that there is one significant difference between these two vaccines. Pneumovax 23 is a polysaccharide vaccine made up of fragments of polysaccharide from pneumococcus cell walls. Prevnar 13 is a “conjugated vaccine,” meaning that the polysaccharides are linked to a protein. This is thought to increase the immune system response to the vaccine.

(click for full-size graph)

The current CDC recommendations are listed below. In the old days, we just gave three vaccines before the patient left the hospital. Then the Pneumovax 23 booster was added at 5 years. Same for the meningococcal serogroup B booster at 4 weeks. Then the meningococcal conjugate vaccine (Menactra) came along and was added (with a booster at 8 weeks). Finally, Prevnar 13 was added with its own booster, and Pneumovax 23 was delayed for 8 weeks. Oh, and don’t forget the 5 year boosters for both Pneumovax 23 and the meningococcal conjugate vaccines. It has become very complicated.

(click for full-size chart)

In my next post, I’ll try to make sense of this mish-mash and offer some thoughts on how to decide what to do for your patients.

Abdomen

Spleen Injury, Angiography, And Splenectomy

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The shift toward initial nonoperative management of spleen injuries began in the early 1990’s, as the resolution of early CT scans began to improve. Our understanding of the indicators of failure also improved over time, and success rates rose and splenectomy rates fell.

Angiography was adopted as an adjunct to early management, especially when we figured out what contrast extravasation and pseudoaneurysms really meant (bad news, and nearly certain failure in adults). At first, it was used in a shotgun approach in most of the higher grade injuries. But we have refined it over the years, and now it is used far more selectively at most centers.

A group at Indiana University was interested in looking at the impact of angio use on splenic salvage over a long time frame. They queried the National Trauma Data Bank, looking specifically at high grade splenic injury care at Level I and II centers from 2008-2014. Patients undergoing splenectomy were divided into early (<= 6hr after admission) and late (> 6 hrs). Over 50,000 records were analyzed.

Here are the factoids:

  • There was a shift from early splenectomy to late splenectomy over the study period that was statistically significant
  • Use of angio increased from 5 to 12% during the study period
  • Overall splenectomy rate remained about the same

So the authors recognize that late splenectomy has decreased. But they also state that early splenectomy has increased. They attribute it to increased recognition of patient requiring early splenectomy. They then call into question the need to use angiography if it hasn’t decreased the overall splenectomy rate.

Problem: The early splenectomy rate increased from about 13% to 14%, reading their graph, and is probably not significant. These are the failures that occur in the trauma bay and shortly thereafter that must be taken to the OR. The late splenectomy rate decreased from 5% to 3%, which may be significant (p value not included in the abstract). These are failures during nonoperative management, and are decreasing over time. And BTW, the authors do not define what “high grade” splenic injuries they are looking at.

AAST2016-Paper35

Bottom line: This abstract illustrates why it is important to read the entire article, or in this case, listen to the full presentation at AAST. It sounds like one that’s been written to justify not having angiography available as it is currently required. 

The authors showed that overall splenectomy rate was the same, but delayed splenectomy (late failure) has decreased with increasing use of angiography. But remember, this is an association, not cause and effect. Most of the early failures are still probably ones that can’t be prevented, but we’ll see if the authors can dissect out how many went to OR very early (not eligible for angio), or later in the 6 hour period (could have used angio). It looks to me like the use of angiography is having the desired effect. But undoubtedly we could use that resource more wisely. What we really need are some guidelines as to exactly when a call to the interventional radiologists is warranted.

Related posts:

Reference: Overall splenectomy rates remain the same despite increasing usage of angiography in the management of high grade blunt splenic injury. AAST 2016, paper 35.

General

When to Give Spleen Vaccines After Splenectomy for Trauma

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I’ve written previously on the (f)utility of giving vaccines after splenectomy for trauma (click here to read). However, it is more or less a medicolegal standard, so pretty much everyone gives them. The big question is, when? 

Some centers give them immediately postop, some before hospital discharge, and some during their postop visit. Who is right? The argument is that major surgery produces some degree of immunocompromise. So if the vaccines are given too early, perhaps the anitbodies will not be processed as effectively, and the response to an actual bacterial challenge might not be as good.

One prospective study randomized patients to receive their pneumococcal vaccine either 1, 7, or 14 days after surgery. IgG levels were measured before vaccination and again after 4 weeks. This study found that antibody concentrations were the same in all groups. However, functional activity of the antibodies was low in the 1 and 7 day groups, and nearly normal in the 14 day group.

Following this, a rat study looked at vaccination timing followed by exposure to pneumococcus. These animals were splenectomized, then given a real or sham vaccination at 1, 7, or 42 days. They then had pneumococcus injected into their peritoneal cavity. About 70% of all rats with sham vaccination died. Only 1.5% of the vaccinated rats died, and there were no differences based on vaccination timing.

Bottom line: Neither antibody titer studies nor rat studies easily translate into recommendations for treating overwhelming post-splenectomy sepsis (OPSS) in humans. And such a study can never be done because of the rarity of this condition (less than 70 cases since the beginning of time). It really boils down to your specific population, balancing your assurance that your patient will get it against the possibility that their immune system may not react to it as much as it could. 

At our center, we give the vaccines as soon as possible postoperatively. This ensures that it is given, and erases any doubt of what might happen if the patient does not show up for their postop check.

References:

  • Immune responses of splenectomized trauma patietns to the 23-valent pneumococcal polysaccharide vaccine at 1 versus 7 versus 14 days after splenectomy. J Trauma 44(5):760-766, 1998.
  • Timing of vaccination does not affect antibody response or survival after pneumococcal challenge in splenectomized rats. J Trauma 45(4):682-697, 1998.

Related posts:

General

When to Give Spleen Vaccines After Splenectomy for Trauma

Leave a comment

I’ve written previously on the (f)utility of giving vaccines after splenectomy for trauma (click here to read). However, it is more or less a medicolegal standard, so pretty much everyone gives them. The big question is, when? 

Some centers give them immediately postop, some before hospital discharge, and some during their postop visit. Who is right? The argument is that major surgery produces some degree of immunocompromise. So if the vaccines are given too early, perhaps the anitbodies will not be processed as effectively, and the response to an actual bacterial challenge might not be as good.

One prospective study randomized patients to receive their pneumococcal vaccine either 1, 7, or 14 days after surgery. IgG levels were measured before vaccination and again after 4 weeks. This study found that antibody concentrations were the same in all groups. However, functional activity of the antibodies was low in the 1 and 7 day groups, and nearly normal in the 14 day group.

Following this, a rat study looked at vaccination timing followed by exposure to pneumococcus. These animals were splenectomized, then given a real or sham vaccination at 1, 7, or 42 days. They then had pneumococcus injected into their peritoneal cavity. About 70% of all rats with sham vaccination died. Only 1.5% of the vaccinated rats died, and there were no differences based on vaccination timing.

Bottom line: Neither antibody titer studies nor rat studies easily translate into recommendations for treating overwhelming post-splenectomy sepsis (OPSS) in humans. And such a study can never be done because of the rarity of this condition (less than 70 cases since the beginning of time). It really boils down to your specific population, balancing your assurance that your patient will get it against the possibility that their immune system may not react to it as much as it could. 

At our center, we give the vaccines as soon as possible postoperatively. This ensures that it is given, and erases any doubt of what might happen if the patient does not show up for their postop check.

References:

  • Immune responses of splenectomized trauma patietns to the 23-valent pneumococcal polysaccharide vaccine at 1 versus 7 versus 14 days after splenectomy. J Trauma 44(5):760-766, 1998.
  • Timing of vaccination does not affect antibody response or survival after pneumococcal challenge in splenectomized rats. J Trauma 45(4):682-697, 1998.

Related posts: