Tag Archives: ct scan

IV Contrast

We use CT scanning in trauma care so much that we tend to take it (and its safety) for granted. I’ve written quite a bit about thoughtful use of radiographic studies to achieve a reasonable patient exposure to xrays. But another thing to think about is the use of IV contrast.

IV contrast is a hyperosmolar solution that contains some substance (usually an iodine compound) that is radiopaque to some degree. It has been shown to have a significant impact on short-term kidney function and in some cases can cause renal failure.

Here are some facts you need to know:

  • Contrast nephrotoxicity is defined as a 25% increase in serum creatinine, usually within the first 3 days after administration
  • There is usually normal urine output and minimal to no proteinuria
  • In most cases, renal function returns to normal after 3-4 days
  • Nephrotoxicity almost never occurs in people with normal baseline kidney function
  • Large or repeated doses given within 72 hours greatly increase risk for toxicity
  • Old age and pre-existing diabetic renal impairment also greatly increase risk

If you must give contrast to a patient who is at risk, make sure they are volume expanded (tough in trauma patients), or consider giving acetylcysteine or using isosmolar contrast (controversial, may still cause toxicity).

Bottom line: If you are considering contrast CT, try to get a history to see if the patient is at risk for nephrotoxicity. Also consider all of the studies that will be needed and try to consolidate your contrast dosing. For example, you can get CT chest/abdomen/pelvis and CT angio of the neck with one contrast bolus. Consider low dose contrast injection if the patient needs formal angiographic studies in the IR suite. Always think about the global needs of your patient and plan accordingly (and safely).

Related posts:

Reference: Contrast media and the kidney. British J Radiol 76:513-518, 2003.

Identifying Bowel and Mesenteric Injury by CT

CT scan is an invaluable tool for evaluating blunt abdominal trauma. Although it is very good at detecting solid organ injury, it is not so great with intestinal and mesenteric injuries. Older studies have suggested that CT can detect mesenteric injuries if done right, but a newly published study has shown good accuracy with a few imaging tweaks.

A Taiwanese study looked at a series of prospectively studied victims of blunt abdominal trauma. Patients with abdominal pain or a positive FAST were entrolled (total 106). IV contrast was given, and scans during the arterial, portal, and equilibrium contrast phases were performed using a multidetector scanner. Images were read in a blinded fashion.

A total of 13 of 23 patients who underwent laparotomy were found to have a bowel or mesenteric injury. Five had bowel injury, 4 had mesenteric hemorrhage, and 4 had both. Mesenteric contrast extravasation was seen in 7 patients, and this correlated with mesenteric bleeding at laparotomy.

The authors found that the following signs on CT scan indicated injury:

  • Full or partial thickness change in bowel wall appearance
  • Increased mesenteric density
  • Free fluid without solid organ injury

Bottom line: This study shows that CT scan can detect bowel and mesenteric injury reliably if you scan the patient 3 times! This seems like over-radiation and overkill. A more intelligent way to approach this would be to perform a normal trauma abdominal scan. If a suspicious area of mesenteric or bowel thickening is seen, then a limited rescan through the affected area only for equilibrium phase images may be warranted. If actual contrast extrvasation is seen, no further scanning is needed. A quick trip to the OR is in order.

Reference: Contrast-enhanced multiphasic computed tomography for identifying life-threatening mesenteric hemorrhage and transmural bowel injuries. J Trauma 71(3):543-548, 2011.

Pediatric CT Scans Before Transfer to a Pediatric Trauma Center

CT scan is essential in diagnosing injury, although concerns for unnecessary radiation exposure are growing. These concerns are even greater in children, who may be more likely to have long-term effects from it. This makes avoiding duplication of CT scanning extremely important.

Unfortunately, there are only about 50 pediatric trauma centers in the US, so the majority of seriously injured children are seen at another hospital before transfer. Does CT evaluation at the first hospital increase the likelihood that a repeat scan will be needed at the trauma center, increasing radiation exposure and risk?

Rainbow Babies and Children’s Hospital in Cincinnati looked at 3 years of transfers of injured children from community hospitals. They then looked at how many of those children had an initial head and/or abdomen scan at the outside hospital, and whether a repeat scan of those areas was performed within 4 hours or arrival at Rainbow.

Numbers were small, but here are the results:

  • 33 had an outside CT scan, 28 (90%) were repeated
  • 6 had an outside abdominal scan, 2 (33%) were repeated
  • 55 did not have outside scans, none were repeated at Rainbow. (This is a weird thing to look at. I would hope that the trauma center didn’t have to repeat any of their own scans within 4 hours!)

Bottom line: It is critically important for referring hospitals to use radiation wisely! First, if the patient has obvious injuries that require transfer, don’t scan, just send. If you need to scan to decide whether you can keep the patient, use the best ALARA* technique you can. And trauma centers, please send a copy of your CT protocols to your referring hospitals so they can get the best images possible.

*ALARA = As low as reasonably achievable (applied to radiation exposure). Also known as ALARP outside of North America (as low as reasonably practicable). Click here for more info.

Related posts:

Reference: Computed tomography before transfer to a level I pediatric trauma center risks duplication with associated radiation exposure. J Pediatric Surg 43(12): 2268-2272, 2008.

Portable CT Scanning For Trauma Patients

I recently had the opportunity to see a portable head CT scanner in action, the CeroTom by NeuroLogica (Danvers, MA). Today, I’ll give my thoughts on this new technology.

There are 3 major considerations when evaluating portable CT scanning:

  • Patient safety, always at the forefront
  • Usefulness, also know as image quality
  • Financial viability

From a safety standpoint, portable scanning can decrease (but not eliminate) the safety hazards associated with transporting a critically ill patient out of the ICU. Road trips are associated with misplaced/displaced lines, tubes and monitors about 15% of the time. These are lifelines in some patients, and even momentary disruptions can be life-threatening. Some patients are on levels of support so high they are not transportable, so portable scanners offer an opportunity to get diagnostic imaging that would not be available otherwise.

Clinical performance is on par with standard scanners. Resolution is lower, but the diagnostic accuracy and reliability are not different compared to fixed scanners.

From a financial standpoint, use of the portable scanner works as well. The Cleveland Clinic deployed a CereTom scanner a few years ago and found that the unit paid for itself in 6.9 months. For you financial types, the internal rate of return was 169% and the 5-year expected economic benefit was $2.6 million.

Bottom line: This new piece of technology offers significant benefits to patients in the ICU who may otherwise not be able to get imaging due to safety reasons. It can also be employed in the OR on anesthetized patients, which can assist with diagnosis in patients with both abdominal injuries requiring immediate operation and concomitant head injury.

Practical notes: The CereTom is an 8-slice scanner with a 25cm field of view. The patient is moved onto a scan board which supports the head while it is moved slightly off the top of the bed to accommodate the scanner. Current scanner cost is $450,000 and attachment packages for hospital beds are $7,000. One CT technologist can operate the unit, which takes about 5 minutes to set up and 15 minutes to scan. All lines, tubes and monitors must be (carefully) moved to the side of the bed so the scanner can fit over the top.  

References:

  • The economic and clinical benefits of portable head/neck CT imaging in the intensive care unit. Radiology Manage 30(2):50-54, 2008.
  • Review of portable CT with assessment of a dedicated head CT scanner. Am J Neuroradiol 30:1630-1636, 2009.

I have no financial interest in Neurologica, Inc.

Results – Blunt Trauma Radiographic Imaging Protocol

In my previous post (click here to view) I discussed an imaging protocol that we developed and implemented last year. Today, I’ll detail what it has accomplished in our patients.

We looked at 229 patients who had their imaging performed according to the new protocol during a 3 month period and compared them to 215 patients who were imaged the previous year. Each scan administered to each body area (head, chest, abdomen/pelvis, c-spine, t-spine, l-spine, face, neck angio) were tabulated separately.

We found that the overall number of scans performed decreased significantly. We looked at our data and generated numbers per 100 patients. During the control period, we did 298 CT scans per 100 patients. This decreased to 271 during the study period. The number of head scans remained the same (82 per 100 patients during control, 85 per 100 during the study), as did the cervical spine scans (84 vs 86).

The biggest declines were seen in chest CT (53 per 100 control vs 33 per 100 study) and abdominal CT (57 vs 43).

We did see an increase in conventional xrays of the thoracic and lumbar spines to offset the absence of reformatted spine images that would have been generated from the chest and abdominal CT scans. We also noted small increases in CT of the head, cervical spine, and neck angio. This was likely due to better adherence to specific guidelines.

Bottom line: we believe that our work shows that careful adoption of well thought out guidelines can make a difference in practice and significantly decreases radiation exposure in our blunt trauma patients.

To read the post on this protocol, or to download it, click here.

Click here to download the Blunt Trauma Radiographic Imaging Protocol Worksheet