All posts by TheTraumaPro

Serial Hemoglobin / Hematocrit – Huh?

The serial hemoglobin (Hgb) determination. We’ve all done them. Not only trauma professionals, but other in-hospital clinical services as well. But my considered opinion is that they are not of much use. They inflict pain. They wake patients up at inconvenient hours. And they are difficult to interpret. So why do them?

First, what’s the purpose? Are you looking for trends, or for absolute values? In trauma, the most common reason to order is “to monitor for bleeding from that spleen laceration” or some other organ or fracture complex. But is there some absolute number that should trigger an alarm? If so, what is it? The short answer is, there is no such number. Patients start out at a wide range of baseline values, so it’s impossible to know how much blood they’ve lost using an absolute value. And we don’t use a hemoglobin or hematocrit as a failure criterion for solid organ injury anymore, anyway.

What about trends, then? First, you have to understand the usual equilibration curve of Hgb/Hct after acute blood loss. It’s a hyperbolic curve that reaches equilibrium after about 3 days. So even if your patient bled significantly and stopped immediately, their Hgb will drop for the next 72 hours anyway. If you really want to confuse yourself, give a few liters of crystalloid on top of it all. The equilibration curve will become completely uninterpretable!

And how often should these labs be drawn? Every 6 hours (common)? Every 4 hours (still common)? Every 2 hours (extreme)? Draw them frequently enough, and you can guarantee eventual anemia.

Bottom line: Serial hemoglobin/hematocrit determinations are nearly worthless. They cost a lot of money, they disrupt needed rest, and no one really knows what they mean. For that reason, my center does not even make them a part of our solid organ injury protocol. If bleeding is ongoing and significant, we will finding it by looking at vital signs and good old physical exam first. But if you must, be sure to explicitly state what you will do differently at a certain value or trend line. If you can’t do this and stick to it, then you shouldn’t be ordering these tests in the first place!

Related post:

Reference: Serial hemoglobin levels play no significant role in the decision-making process of nonoperative management of blunt splenic trauma. Am Surg 74(9):876-878, 2008.

February Newsletter Released To Subscribers This Weekend!

The February Trauma MedEd Newsletter will be released to subscribers over the weekend. This month’s theme is “tips and tricks.” Articles include:

  • What exactly is a wide mediastinum?
  • Bowel sounds, or just BS?
  • Predicting ambulance arrival time
  • Do you really need to do what the radiologist says?
  • And more!

Anyone on the subscriber list as of 8 PM (CST) Saturday will receive it on Sunday. I’ll release it to everyone else next Friday via the blog. So sign up for early delivery now by clicking here!

Pick up back issues here!

How To Avoid Missed Injuries

I’ve just spent two days here looking at the phenomenon of “delayed diagnosis” or missed injury. I believe that there are only two fundamental reason why this occurs:

  • Insufficient diagnostic technique – A good physical exam and/or specific diagnostic techniques were not performed. Or rarely, the injury cannot be readily detected by existing techniques and technology. The former is usually the real problem, and may be an issue with either the physical exam completeness and/or technique, or judgment used to obtain the appropriate diagnostic test. Example 1: a penetrating injury to the back is missed because the patient is not logrolled to examine this area. Example 2: a spine fracture is missed in an elderly patient with a fall from standing because the back pain found on physical exam is evaluated only with conventional imaging of the spine, not CT.
  • Failure to recognize the injury – The injury was actually identified on a test, but was not appreciated by the clinician. Example 1: the radiologist may not have appreciated and reported out a subtle anomaly in the cervical spine imaging. Example 2: you fail to check you patient’s lab tests and miss a sudden spike in serum amylase or lipase the day after your patient was kicked in the epigastrium by a horse.

So what can you do to avoid this potential problem? Here are some tips:

  • Admit that it can really happen to you. If the missed injury rate at your center is off the low end of the bell curve (< 5%) then you are either really good or really blind. You’d better take a close look at your performance improvement process, because you may be fooling yourself.
  • Adopt a firm definition of “delayed diagnosis.” Basically, you need a time frame after which a new diagnosis is considered “delayed.” It should be a reasonable time interval after the patient has left the ED. If it’s too short an interval (e.g. once they leave the ED), your number will be unnecessarily high. If it’s too long (days and days later), then significant morbidity may occur that you don’t account for. Most centers have adopted 24, 36, or 48 hours after patient arrival.
  • Implement a tertiary survey process. This is a complete physical re-examination followed by a review of all diagnostic studies (lab and radiology) that have been performed. This exam needs to be dated and timed to ensure that it is performed within the time frame noted above. If a new finding is discovered on the tertiary survey, it is not considered a delayed diagnosis. If found after the survey (or after the pre-determined time interval), it is and must be entered into your performance improvement process.
  • Be paranoid. I hate the phrase, “maintain a high index of suspicion” because it’s meaningless. It’s like those stupid “start seeing motorcycles” bumper stickers. You can’t see what you can’t see. But you can be suspicious all the time, constantly looking for the inevitable clinical surprises of trauma care. 

Related posts:

Are There Really More Missed Injuries After Hours?

Yesterday, I wrote about the usual reasons for delayed diagnosis: insufficient diagnostic technique or insufficient recognition. What about time of day? A recent paper looked at the correlation between admission time and rate of missed injuries.

The work was done at a large teaching hospital and Level I trauma center in Australia. A large number of patients were reviewed over an 11 year period. The study was complicated slightly by the implementation of a dedicated trauma unit in the middle of the study period, but the authors stratified their groups to account for this. 

Results were stratified by time of admission: office hours vs after-hours vs weekends. Missed injuries were defined as those found after completion of the primary and secondary surveys. The overall statistical treatment appeared to be robust.

Here are the factoids:

  • A huge number of patients (53,000) were reviewed. This is a busy place!
  • There were 2519 missed injuries in 1262 patients (2.4%) [low!]
  • Missed injuries occurred during office hour admissions in 2.2%, after-hours in 2.6%, and on weekends 2.5% of the time
  • The increased incidence of delayed diagnosis in after-hours admits was marginally significant (p = 0.048)
  • Missed injuries appeared to have increased over time, and were 1.34 times more likely at the end of the study period vs the beginning
  • Thoracic spine and abdominal injuries were most the commonly missed

Bottom line: Hmm, time of day was not in my list of reasons for missing diagnoses. What gives? If you read the article closely, the trauma service at this hospital was staffed with a higher number of trainees after hours and on weekends than during office hours. It was also noted that incomplete physical examination was thought to be a factor in many of the delays. Most likely, both of my listed reasons were in play here. Inexperienced clinicians and insufficient examination are both major factors. And what about the increase in missed injuries over time? Midway through the study, the hospital implemented a dedicated trauma unit, and a tertiary exam became routine. This identified more injuries after the primary and secondary surveys were complete. 

Tomorrow I’ll talk about strategies to drop the incidence of missed injury.

Reference: Office hours vs after-hours: do presentation times affect the rate of missed injuries in trauma patients? Injury 2015, in press.

Missed Injury / Delayed Diagnosis

Missed injuries (or delayed diagnosis in polite conversation) are the bane of any trauma program.Trauma professionals want to know that they’ve identified all significant injuries in their patients so no future harm will occur due to them.

But what exactly is a missed injury? The definitions tend to vary a bit, which is why their incidence varies so widely in the literature (1 – 39%). The simplest way to describe one is any injury that is identified after a set amount of time. But what is a reasonable time frame? Some define it as the time spent in the emergency department (highest incidence). Others count any injury found after a predetermined period of time (typically 24-48 hours). Some use even longer time intervals, so they obviously look the best and have the lowest incidence.

And what are the factors that contribute to us “missing” these injuries? As you can imagine, there are quite a few, but they boil down to two major categories:

  • Inadequate diagnostic technique (physical exam and/or technology) – I can’t see it
  • Inadequate recognition – I didn’t think of it

A good physical exam with the focused use of appropriate imaging is paramount. Sure, you could use a shotgun approach and just scan everything. The problem is that CT scans have limitations, but we tend to forget that. So we believe that if we don’t see anything on scan, it must not exist. Wrong! The physical exam may pick up suspicious findings that tell the clinician that a specialized study is necessary to rule a potential injury out.

The failure to recognize that an injury is present can occur with everyone that “touches” the patient. The EMT or physician may not appreciate a subtle injury. The radiologist may miss a problem on the images they read. The surgeon might even fail to notice another injury separate from the one she is operating for. Obviously, experience plays a large part in this factor. Students will fail to appreciate a potential injury that a senior clinician will detect rapidly. 

What to do about it? Tomorrow, I’ll review a recent paper that tries to correlate missed injuries with time of admission. And on Friday, I’ll discuss some strategies to try to help keep it from happening to you.