• Injected fragments from rubber stoppers
• Self-assembled jet ventilation devices

A new study highlights a potential risk associated with injected anesthetics: rubber particles cored from the caps of medication vials.

These fragments, which shear off as a needle penetrates a rubber stopper, are difficult to detect, given their miniscule size and that an opaque vial or a label often obscures them. Some researchers are concerned that injecting this matter into patients may lead to complications, such as latex allergies and ischemia.

The study found that the incidence of coring is “alarmingly high”—particles may be found in as many as 19% of doses drawn from rubber stoppers. The authors presented their findings at the 2008 PostGraduate Assembly in Anesthesiology (abstract P-9155), in New York City. As a growing number of patients receive multiple exposures to anesthetic agents, the risk for injecting rubber cores may be rising, the researchers noted.

Anesthesiologist Tariq M. Wani, MD, of the University of Missouri-Columbia School of Medicine, who helped conduct the study, said the work was prompted by the question: “If we are using plastic needles to protect ourselves, does it result in more rubber core in medications?”

The answer, he said, seems to be yes. Coring was considerably less frequent with acutely beveled sharp steel needles (4%) than with blunt plastic needles (29%), said Dr. Wani, whose group also presented its findings at the 2008 annual meeting of the American Society of Anesthesiologists (abstract A-368), in Orlando, Fla.

The investigation was a randomized, controlled, double-blind study that analyzed 500 medication vials used by anesthesia providers at the University of Louisville Hospital in Kentucky, where Dr. Wani did his residency. Doctors were randomly assigned to use either 18-gauge sharp steel (type A beveled) needles or blunt plastic needles to administer medications from rubber-topped vials. To reduce the risk for accidental injection of cored material, the anesthesiologists were instructed to pierce the caps with 18-gauge needles before using smaller, 25-gauge needles to draw the medication. The used vials were then filled with 5 mL of normal saline, filtered and examined for rubber particles.

According to Dr. Wani, the results of two previous studies on particulate matter suggested that cored rubber may cause ischemia in muscles and block small blood vessels in the lungs. Latex allergy also may be a complication, he added.

However, for these adverse effects to occur, cored fragments from the vial cap must be aspirated into the syringe and then injected into the patient. The likelihood of this chain of events remains unknown, as do the adverse clinical effects of rubber particles in the bloodstream.

There is no substantiated risk that rubber cores will harm a patient, Dr. Wani acknowledged. However, he estimated that the chances of cored matter being injected into a patient are fairly high, particularly with 18-gauge needles.

To reduce the likelihood of coring, Dr. Wani recommended that filtered needles be used to draw doses of medication, or that a method other than piercing the rubber caps be used to open the medication vials—steps that take time, he acknowledged. Although clinicians often prefer blunt plastic needles for safety, the potential risks associated with rubber coring must be considered, he said.

The prospect of harm from coring is intriguing, but the risk to patients remains uncertain, said Robert Lagasse, MD, professor of anesthesiology at Montefiore Medical Center in Bronx, N.Y., and president of the New York State Society of Anesthesiologists.

“We might now know the risk of coring—4% with sharp bevels—but we don’t know the risk of the core exiting the needle,” added Dr. Lagasse, who is a member of the editorial board of Anesthesiology News. “If you have ever lost a cork in a wine bottle, especially a rubber ‘cork,’ then you can see how the two might be different. I would like to see anesthesiologists stop sticking needles in rubber stoppers because the risk of accidental needlestick injury to the anesthesiologist is real.”

—Alicia Lukachko, MPH

Patients rarely require jet ventilation through a needle, but physicians should consider purchasing a ready-made device for these emergency situations rather than attempting to build their own.

The self-assembled devices often use a three-way stopcock to connect a high-pressure oxygen source to a catheter that is passed through the cricothyroid membrane and into the trachea, said Ankie Hamaekers, MD, an anesthesiologist at University Hospital Maastricht, in the Netherlands, who has studied the issue.

Physicians assume that they can use the three-way stopcock to completely shut off the flow of oxygen to the patient at any time, Dr. Hamaekers said. But this kind of device “will never ensure complete flow and pressure release through its side port when connected to a continuous flow of oxygen.” And the continuous flow of oxygen to a patient with an obstructed upper airway will inevitably create a positive end-expiratory pressure, which can lead to barotrauma and hemodynamic instability, she said.

Dr. Hamaekers and her colleagues presented their analysis of three such jury-rigged devices at the 2008 annual meeting of the Society for Airway Management, in Boston (abstract 8). Each of the makeshift assemblies consisted of a three-way stopcock (inner diameter of 2.0, 2.5 or 3.0 mm) connected in-line to a flowmeter and a 75-mm-long transtracheal catheter with an internal diameter of 2 mm. The researchers measured the pressure at the tip of the catheter of each device while the side port was in the open position at four different oxygen flow settings (6, 9, 12 and 15 L/min).

When the oxygen flow rate was set at 15 L/min, the pressure at the catheter tip was 71.1 cm H₂O. Although the pressure dropped when the oxygen flow rate was lowered, a flow rate of 9 L/min still generated a pressure of 25.8 cm H₂O at the catheter tip.

Dr. Hamaekers and her colleagues concluded that oxygen flow settings of 9 L/min would lead to “dangerously high airway pressures” in patients with obstruction of the upper airway. “Based on our findings,” they said, “these self-assembled jet devices should not be used in airway emergencies because upper airway obstruction can never be excluded.”

William Rosenblatt, MD, professor of anesthesiology at the Yale University School of Medicine, in New Haven, Conn., agreed.

“What’s funny about this is that when it comes to ventilation with a face mask, supraglottic airway or endotracheal intubation, money is no object,” Dr. Rosenblatt said. “They will spend a tremendous amount of money to get the best equipment. But when it comes to an emergency procedure, such as putting a needle in the patient’s neck, people are not as prepared to spend money.”

Dr. Rosenblatt suspects the rarity of the situation leads physicians to opt for the homemade solution. “But the irony is that compared to everything else, this equipment for transtracheal jet oxygenation is very cheap,” he said.

Beyond the issue of leakage, Dr. Rosenblatt said, physicians need to be realistic about the time it takes to assemble the jury-rigged device. People assume that they can throw it together quickly, “but when you make these homemade devices, studies show it takes longer than you think it will, and you’ve got a patient starving for oxygen. Now this study comes along showing that they don’t even work well. We’re fooling ourselves if we think you can turn the stopcock in such a way that the oxygen stops flowing to the patient.”

The best solution, Dr. Rosenblatt said, is to go out and buy a product that is specially made for this situation.

Indeed, that’s the standard at the University of Pittsburgh Medical Center, said Michael Mangione, MD, associate professor of anesthesiology at the institution and chief of anesthesia at the Pittsburgh Veterans Administration Health Care System. Anyone tempted to use the homemade devices should heed the Dutch researchers’ warning, he said. “I can see someone hooking a patient up this way and having the gas flow turned on and a patient blowing up.”

—Linda Carroll