Prevention of Catheter-Related Bacteremia with a Daily Ethanol Lock in Patients with Tunnelled CathetersA Randomized, Placebo-Controlled Trial

Picture a hematology ward. A patient is midway through a chemotherapy cycle, and threaded under their skin, curving into a major vein near the heart, sits a tunnelled silicone catheter, known as a Hickman line. It's there for months. It has to be. You can't deliver this kind of treatment through an ordinary intravenous line. But that permanent access point is also a permanent open door, and what walks through it can kill. Catheter-related bloodstream infection, or CRBSI, carries attributable mortality as high as twenty-five percent in critically ill patients. A meta-analysis found that patients with CRBSI have an odds ratio for death of 1.65 compared with matched controls without it. The question isn't whether these infections matter. It's whether we can stop them. The dominant pathway in tunnelled catheters is endoluminal: bacteria contaminate the hub, the external connector. They migrate inside the lumen, form a biofilm on the inner surface, and periodically shed into the bloodstream. That's the target. And the proposed weapon, in the trial reported by Slobbe and colleagues, is both simple and slightly counterintuitive: ethanol. Seventy percent ethanol, locked inside every lumen of the catheter for fifteen minutes a day. Not a drug. Not a new antibiotic. Alcohol. The logic holds up. Ethanol is broadly bactericidal and fungicidal, doesn't promote antibiotic resistance, is inexpensive, and is widely available. The problem with biofilms is penetration; organisms embedded in a matrix are harder to kill than free-floating ones. But prior in vitro work cited by Slobbe and colleagues showed a three-log reduction in biofilm-associated gram-positive cocci after twenty minutes at sixty percent ethanol, and complete eradication after thirty minutes. Another study found full sterilization of a bacterial biofilm after just one minute of exposure to seventy percent ethanol. Those ranges are wide, and that ambiguity matters later. But the biological case for trying this was solid enough to run a proper trial. The trial ran from 2005 to 2008 at Erasmus Medical Center. It was randomized, double-blind, and placebo-controlled. Adult hematology patients who had a tunnelled Hickman catheter inserted within the previous seventy-two hours were eligible. Randomization was catheter-based rather than patient-based, so a single patient could be enrolled more than once if a new catheter was placed. Pharmacy staff prepared labeled ampoules of either seventy percent ethanol or placebo, which was plain saline, maintaining allocation concealment. Each lumen received three milliliters of the lock solution, which sat for fifteen minutes, then was flushed through with ten milliliters of saline. While hospitalized, patients received the lock daily; in outpatient settings, it was applied once weekly. The primary endpoint was endoluminal CRBSI, defined through a combination of hub cultures, blood cultures, genotypic strain matching, and a differential time-to-positivity criterion. This criterion meant the catheter blood culture had to turn positive at least two hours earlier than a peripheral one, indicating the catheter was the source. The sample size calculation assumed a baseline CRBSI incidence of roughly twenty percent and aimed to detect a fifty percent reduction, requiring around 219 catheter episodes per arm. Here's where the story gets complicated. The trial enrolled 376 patients, generating 448 catheters and 27,745 catheter-days of follow-up. In the ethanol arm, the incidence of endoluminal CRBSI was 0.70 per 1,000 catheter-days. In the placebo arm, it was 1.19. The incidence rate ratio was 0.59 — a forty-one percent reduction. The p-value was 0.19. Not significant. Using the strictest possible definition, which required a positive hub culture with the genotypically identical strain in blood, the picture looked even more promising numerically: two events in the ethanol group versus seven in placebo, a three-point-six-fold reduction. That p-value was 0.103. Also not significant. So the trend is real and consistent. Fewer infections, lower rates, a meaningful-looking ratio. And statistically, nothing to show for it. That result demands explanation before a verdict. Slobbe and colleagues are direct about what happened: the trial was underpowered because the baseline CRBSI rate in this population turned out to be far lower than anticipated. The power calculation assumed incidence around twenty percent. The actual observed rate in the placebo arm, by the strictest definition, was roughly three percent, translating to seven infections among 222 catheter episodes. When the event rate is that low, even a large relative reduction produces very few absolute events, and confidence intervals balloon. The authors calculate that a future trial targeting a seventy-five percent reduction would need around 848 patients. To reliably detect a fifty percent reduction, you'd need roughly 2,282 patients. The trial enrolled 376. There's also a procedural question worth considering. The fifteen-minute dwell time was chosen to minimize disruption to clinical care, but the in vitro data suggest it may be at the short end of what's needed. And after those fifteen minutes, the lock was flushed through the catheter rather than removed — a different approach from other studies in the literature. Slobbe and colleagues flag this; removing the lock solution might be preferable, and it might also address the tolerability problems that emerged. Those tolerability problems are real and deserve their own moment. No life-threatening adverse events occurred. Liver enzymes and standard blood markers showed no signal of systemic toxicity after two weeks of locking. But patients in the ethanol arm had a dramatically higher rate of stopping treatment or reducing its frequency. Eleven patients in the ethanol group discontinued the lock versus one in placebo, which is a statistically significant difference with a p-value of 0.006. Ten ethanol patients switched to a reduced lock frequency versus zero in placebo, with a p-value of 0.002. What were they experiencing? In a questionnaire subsample, facial flushing occurred in 39 ethanol patients versus 17 on placebo. Dizziness or drowsiness was reported in 41 versus 10. An alcohol taste occurred in 31 versus 19. These are subjective symptoms. They are not dangerous. But they are recurrent, they affect patients who are already exhausted and immunocompromised, and they apparently happen specifically when the lock is flushed through, which pushes a bolus of diluted ethanol rapidly into the bloodstream. One patient had syncope after the first flush. One catheter lumen ruptured during sleep. Slobbe and colleagues suggest that removing the lock rather than flushing it through could both reduce these effects and potentially allow a longer dwell time. There is also a blinding caveat worth acknowledging. Nursing staff who opened the ampoules could detect ethanol by smell. The investigators themselves remained blinded, and the primary endpoint was objective, but perfect blinding of this intervention is difficult in practice. None of this proves that ethanol locks don't work. Slobbe and colleagues are careful to preserve that distinction: the trial couldn't confirm efficacy, which is different from disconfirming it. The consistent numerical reduction — 0.70 versus 1.19 infections per 1,000 catheter-days, rate ratio 0.59 — is clinically meaningful if real. A forty-one percent reduction in bloodstream infections in a population this vulnerable would matter. The authors call explicitly for further randomized trials in higher-risk populations where baseline CRBSI rates are elevated. Long-term total parenteral nutrition patients are the example they give, and where the trial would therefore be adequately powered to detect a real effect. The intervention costs almost nothing. It doesn't generate antibiotic resistance. And in this trial of 376 hematology patients, it showed a consistent trend toward fewer catheter infections across every way of measuring them. The trial couldn't confirm it statistically, largely because the infection rate was lower than expected, which is itself not a bad clinical problem to have. What the trial did establish clearly is that tolerability is the engineering challenge: patients stop a therapy that makes them feel intermittently dizzy and flushed, even if the alternative is a bacteremia that could kill them. That's not irrational; it's human. The next trial needs to solve that problem first. 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