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Letters |
University of Wisconsin Madison, WI 53792
We read the September 2004 AJR article "Irrigation of the Bile Ducts with Chilled Saline During Percutaneous Radiofrequency Ablation of a Hepatic Ocular Melanoma Metastasis" [1] with great interest. Lieberman et al. should be congratulated for using a creative, minimally invasive technique to perform radiofrequency ablation safely in a difficult anatomic area. Warming or cooling vulnerable structures as a way to prevent thermal damage is not a new concept. The most widespread use of this type of technique is probably the routine use of a urethral warming catheter for prostate cryoablation [2]. A smaller version of this catheter has also been described for bile duct warming during intraoperative hepatic cryoablation [3].
At the 2003 RSNA Scientific Assembly, Drs. Lees and Gillams described a technique for preventing thermal injury of perihepatic structures during radiofrequency ablation by infusing 5% dextrose in water into the peritoneum. The rationale for using this technique is compelling: 5% dextrose in water is near isotonic, is well tolerated in virtually every body space, and is rapidly absorbed. Most importantly, because 5% dextrose in water is nonionic, it only minimally interacts with electrical current. Recall that tissue heating during radiofrequency ablation is due to ionic agitation by alternating electric current. Thus, placing an ionic solution such as saline in the bile duct may increase the risk of thermal injury [4, 5]. This risk is balanced against the cooling effect of the flowing chilled saline that may or may not create enough cooling to prevent thermal injury.
Using a nonionic solution such as 5% dextrose in water or sterile water more optimally protects vulnerable structures, particularly if an obstruction or slow infusion causes stasis of the saline. We have confirmed the increased protective effect of 5% dextrose in water compared with saline in a recently completed animal trial (unpublished data).
The authors' last sentence is prescient: "Further research is necessary to validate the technique and define the ideal fluid for bile duct irrigation" [1]. As thermal ablation becomes more widespread, it is likely that more aggressive case selection will follow. To decrease complications and avoid discrediting the rapidly burgeoning field of imaging-guided tumor ablation, techniques such as the one in this case report will need to become more widespread. However, physicians should think carefully about using saline when 5% dextrose in water can potentially provide added protection for no additional cost.
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  J. L. Hinshaw, A. M. Shadid, S. Y. Nakada, S. P. Hedican, T. C. Winter III, and F. T. Lee Jr. Comparison of Percutaneous and Laparoscopic Cryoablation for the Treatment of Solid Renal Masses Am. J. Roentgenol., October 1, 2008; 191(4): 1159 - 1168. [Abstract] [Full Text] [PDF]
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