General

Flying Or Diving After Traumatic Pneumothorax: Part 2

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In my last post, I wrote about the accepted management of and delay in flying due to traumatic pneumothorax. I republished the post because of the publication of a paper from Oregon Health Science University in Portland. The authors specifically tried to assess timing of chest tube removal and long-distance flight, and to measure the risk of pneumothorax recurrence or other complications.

The authors performed a retrospective review of a series of military patients who had sustained chest injuries that were treated with chest tubes over a 5 year period from 2008 to 2012. After tube removal and a pneumothorax-free period of at least 24 hours (by chest x-ray), the patients were then transported by air from the military theater back to the United States.

Here are the factoids:

  • Of 517 patients screened in the military trauma registry database, only 73 were available for study after applying exclusion criteria
  • Subjects were predominantly young and male, as one would expect from the injured military population, and 74% were injured by a penetrating mechanism
  • Median time that the chest tube was in place was 4 days, and median time from tube removal to flight was 2.5 days
  • All patients had post-flight documentation available for review, but only half (37) had in-flight documentation available
  • Nearly half (40%) had positive pressure ventilation in place during the flight
  • Five patients had “in-flight medical concerns” (4 were ventilated), but none were related to the pneumothorax. The four ventilated patients had ventilator issues, the non-vented patient had “self-limited discomfort without evidence of respiratory distress.”
  • None of the subjects developed a recurrent pneumothorax, either post-flight or over the following 30 days

The authors conclude that air travel after tube removal and a 24-72 hour observation period “appears safe.”

Bottom line: Not so fast! This is yet another small, retrospective study making grand claims. The study group is a very unique population: healthy, fit young men with penetrating injury. Your average civilian trauma patient is older, less healthy, and usually has a blunt mechanism with multiple rib fractures. In-flight documentation was not available in half of the cases. And a full medical team was present on the aircraft had a problem actually occurred.

Contrast this with a civilian patient on a commercial aircraft with very limited medical equipment and expertise on board. What could go wrong? I definitely do not recommend changing our practice on these patients yet based on this one paper. Until we have better guidance (more good papers) stick to the usual wait time to ensure a safe flight for your patient.

Reference: Trauma patients are safe to fly 72 hours after tube thoracostomy removal. J Trauma, published ahead of print, May 18 2018.

Thorax

Flying Or Diving After Traumatic Pneumothorax: Part 1

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Today, I’m dusting off an old post on flying and diving after pneumothorax. This shows the thinking up until a few years ago. In my next post, I’ll write about a more recent paper that suggests that we can shorten the “no-fly” time considerably.

Hint: no changes to the diving recommendations. One pneumothorax is likely to ground you forever. (pardon the pun)

Patients who have sustained a traumatic pneumothorax occasionally ask how soon they can fly in an airplane or scuba dive after they are discharged. What’s the right answer?

The basic problem concerns Boyle’s Law (remember that from high school?). The volume of a gas varies inversely with the barometric pressure. So the lower the pressure, the larger the volume of gas becomes. Most of us hang out close to sea level, so this is not an issue. But for flyers or divers, it may be.

Flying

Helicopters typically fly only one to two thousand feet above the ground, so the air pressure is about the same as standing on the earth. However, flying in a commercial airliner is different. Even though the aircraft may cruise at 30,000+ feet, the inside of the cabin remains considerably lower though not at sea level. Typically, the cabin altitude goes up to about 8,000 to 9,000 feet. Using Boyle’s law, any volume of gas (say, a pneumothorax in your chest) will increase by about a third on a commercial flight.

The physiologic effect of this increase depends upon the patient. They may never know anything is happening if they are young and fit. But if they are elderly and/or have a limited pulmonary reserve, it may compromise enough lung function to make them symptomatic. And having a medical problem in an aluminum tube at 30,000 feet is never good.

Commercial guidelines for travel after pneumothorax range from 2-6 weeks. The Aerospace Medical Association published guidelines that state that 2-3 weeks is acceptable. The Orlando Regional Medical Center reviewed the literature and devised a practice guideline with a single Level 2 recommendation that commercial air travel is safe 2 weeks after resolution of the pneumothorax, an that a chest x-ray should be obtained immediately before travel to confirm resolution.

Diving

Diving would seem to be pretty safe, right? Any pneumothorax would just shrink while the diver was at depth, then re-expand to the original size when he or she surfaces, right?

Not so fast. You are forgetting why the pneumothorax was there in the first place. The lung was injured, most likely via tearing it, penetration by something sharp, or popping a bleb. If the injured area has not completely healed, then air may begin to escape through it again. And since the air used in scuba diving is delivered under pressure, this could result in a tension pneumothorax.  This is disastrous underwater!

Most injuries leading to pneumothorax heal completely. However, if there are bone spicules stuck in the lung or more complicated parenchymal injuries from penetrating injury, they may never completely heal. This makes the diver susceptible to a tension pneumothorax anytime they use their regulator.

Bottom line: Most patients can safely travel on commercial aircraft 2 weeks after resolution of pneumothorax. Ideally, a chest xray should be obtained shortly before travel to confirm that it is gone. Helicopter travel is okay at any time, since they typically fly at 1,500 feet or less.

Divers should see a physician trained in dive medicine to evaluate their injury and imaging prior to making another dive.

Tomorrow: new info on flying after pneumothorax

References:

  • Divers Alert Network – Pneumothorax – click to download
  • Practice Guideline, Orlando Regional Medical Center. Air travel following traumatic pneumothorax. October 2009.
  • Medical Guidelines for Airline Travel, 2nd edition. Aerospace Medical Association. Aviation, Space, and Environmental Medicine 74(5) Section II Supplement, May 2003.
Complications

Top 10 Worst Complications: #1 Nasocerebral Tube

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Minor complications from nasogastric tube insertion occur relatively frequently. Emesis is fairly common when the gag reflex is stimulated by the tube in the back of the oropharynx. An infrequent but possibly fatal one is insertion through the cribriform plate. 

The cribriform plate is located directly posterior to the nares and is part of the ethmoid bone. It is very porous in nature and weaker than the surrounding portions of the ethmoid. It is easily fractured, and can be seen is association with basilar skull fractures. This is one source for rhinorrhea in patients with these fractures.

Cribriform fracture is a contraindication to unprotected insertion of a nasogastric tube. If you look at the sagittal section below, the plate lies directly behind the nares. When inserting the NG tube, we are usually taught to aim the tube straight back. Unfortunately, this aims it directly at the cribriform. If a fracture is present, it is possible that you may be inserting a nasocerebral tube!

Cribriform plate - sagittal section

The usual symptoms when this occurs consist of immediate neurologic deterioration to coma, and a unilateral or bilateral blown pupil. The tube must not be withdrawn, because it will cause significant injury to the base of the brain. A stat neurosurgical consultation must be obtained, and if the patient is salvageable, the tube must be withdrawn through a craniectomy.

To avoid this dreaded complication, identify patients at risk for cribriform injury. They are:

  • patients with signs of trauma from eyebrows to zygoma
  • comatose patients
  • patients with signs of basilar skull fracture (Battle’s sign, raccoon eyes, oto- or rhinorrhea)

If your patient is at risk, follow these guidelines:

  • first, does the patient really need a gastric tube?
  • if comatose, insert an orogastric tube
  • if awake, don’t put the tube in their mouth, as they will gag continuously. Instead, place a lubricated, curved nasal airway. Then lube up a slightly smaller Salem sump tube and pass it through the airway.
Complications

Nausea In The Trauma Bay: Gastric Tube vs Anti-Emetic Drugs?

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Nausea and vomiting are common problems in trauma patients, particularly those in a trauma activation. Inciting factors include pain, full stomach from food eaten before the event or blood swallowed after, or reaction to pain medications. For years, trauma professionals reached for the lowly gastric tube to evacuate stomach contents to “solve” the problem.

But how many of you have seen a patient forcefully empty their stomach as soon as the tube touches the oropharynx? And of course, your patient is lying supine, so the vomitus goes straight up, then back down into their airway. And if their mental status is not quite right, they may aspirate, causing even bigger problems.

We’ve had anti-emetic medications for a long time, some more effective than others. Only recently have we begun to rely on these as a first line defense in the trauma resuscitation room. But do they work? Are they safer?

The University Medical Center Utrecht in the Netherlands looked at this problem. They changed their policy from inserting a gastric tube to administering anti-emetics at the beginning of 2014. They studied their experience for the 6 months before and 6 months after the policy change. They inserted an orogastric (OG) tube preferentially before the switch, and used ondansetron and/or metoclopramide after.

Here are the factoids:

  • A total of 1446 trauma patients were admitted during this period. After excluding patients who were intubated or did not complain of nausea, 453 were analyzed (30%)
  • 20% of patients who had an OG tube placed vomited vs only 3% receiving medication (significant)
  • After therapy, 14% of patients receiving an OG were still nauseated vs only 2% getting meds (also significant)
  • 3 patients vomited and aspirated after OG placement, and 1 developed a pneumonia. 2 patients became bradycardic and med administration, and one developed QT-prolongation

Bottom line: This is a relatively small, retrospective study. Furthermore, the choice of gastric tube route (oral) is a setup for gagging and vomiting. Nasogastric tubes are a bit less noxious, but can’t be inserted in all patients (see next week’s post). Even so, the use of anti-emetics in trauma patients complaining of nausea seems like the kinder, gentler way to go. 

Which drug to use? Previous studies have shown that ondansetron 4mg is as effective as 8mg, and that this drug is about equally as effective as metoclopramide. There is also some evidence that giving both is more effective than just giving one.

Gastric tubes are still important, particularly in the comatose patient. But since these patients are at risk for cribriform plate injury, only the oral route should be used.

Reference: Analysis of two treatment modalities for the prevention of vomiting after trauma: orogastric tube or anti-emetics. Injury (accepted manuscript, in press) online 8 July 2017.

Abdomen, Complications

Colonic Pseudo-Obstruction In Trauma Patients – Part 2

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In my last post, I discussed a paper describing the incidence of colonic pseudo-obstruction (CPO), or Ogilvie syndrome, in trauma patients. The paper confirmed my bias that this condition could be a problem in a specific subset of trauma patients. They are generally older men with pelvic or spine fractures, with or without surgical fixation. In addition, some comorbidities like diabetes, obesity, and concomitant head injury increase the incidence.

The usual dogma is that a cecal diameter > 12cm places the patient at risk of perforation. Therefore, as the size of the colon increases, steps should be taken to decompress it definitively. This typically involves neostigmine infusion, which usually requires transfer to the ICU, or colonoscopic decompression.

Until about eight years ago, we managed this issue at Regions Hospital using the IV neostigmine option in the ICU. But then, one of our colorectal surgeons described his experience managing CPO with subcutaneous neostigmine. A light bulb turned on! Intravenous neostigmine requires admission to an ICU at our hospital for continuous monitoring to quickly identify the development of bradycardia.

But subcutaneous neostigmine was not on the naughty list! We developed a practice guideline to identify and exclude patients for whom this drug was contraindicated. And it required monitoring that could be accomplished in a floor bed with brief episodes of continuous EKG monitoring. Our inpatient trauma unit could easily do this. However, it might require a step-down bed in yours.

Here is the guideline. Click the image of the link at the end of this post to download a copy.

Here are the major features of the guideline:

  • Identification. Any patient, especially those with the previously described risk factors, begins daily monitoring with a flat plate abdominal x-ray. Patients with abdominal distension with subjective discomfort or nursing concerns with the distension fall into this category.
  • Trigger. Once distension of any part of the colon, particularly the cecum, exceeds 10 cm, it is time to act. Otherwise, daily monitoring and a bowel regimen continue.
  • Contraindications to neostigmine. If the patient has a recent history of MI, bronchospasm, is on beta-blocker therapy, or has SBP < 90 torr, heart rate < 60, or weight < 50kg, colonoscopic decompression should be carried out.
  • Continuous monitoring must be available for one hour after injection. This requires an appropriate nurse and an EKG monitor. Atropine must be present at the bedside in case bradycardia develops.
  • Up to three doses of SQ neostigmine (1mg) can be given 12 hours apart. If the patient responds with a large bowel movement or passage of gas, it should be confirmed with an abdominal x-ray.
  • Patients with insufficient response must transfer to ICU for IV neostigmine or should be scheduled for an urgent colonoscopy.

Our experience has shown that this guideline is usually very effective. However, a few patients have had a recurrence after 24-48 hours, which is uncommon. The guideline can be repeated if necessary.

Bottom line: A low index of suspicion for CPO in trauma patients is critical. Once the colon perforates, these patients do poorly, and serious complications are common. This guideline allows the trauma service to keep these patients out of the ICU while treating it. But before you implement this, please work closely with your pharmacists to ensure that hospital policy allows using neostigmine outside of an ICU setting.

Colonic Pseudo-Obstruction in Trauma – Practice guideline. Click to download.

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