Improved coagulation with saline solution pretreatment during radiofrequency tumor ablation in a canine model.
OBJECTIVE
To determine whether pretreatment with local NaCl injection can increase radiofrequency (RF)-induced coagulation in a large animal model.


METHODS
Multiple canine venereal sarcomas (n = 25) were implanted subcutaneously in eight mildly immunosuppressed dogs (25 mg/kg cyclosporin A twice daily). Tumors were incubated for 8-12 weeks to a diameter of 4.2-6.3 cm (5.1 cm +/- 0.7). Internally cooled RF ablation (1-cm tip; 12 min; pulsed technique; 2,000-mA maximum) was performed. Tumors were pretreated with 6 mL of 18%, 24%, or 36% NaCl injected intratumorally under direct ultrasound guidance after RF electrode insertion, and this treatment was compared to RF treatment without NaCl injection and to 36% NaCl injection without RF ablation. Impedance measurements and remote thermometry were performed. These measurements and resultant coagulation were compared.


RESULTS
Significantly greater RF heating (73 degrees C +/- 11 degrees C at 20 mm) was observed when the tumors were treated with 24% or 36% NaCl pretreatment, compared to the 47 degrees C +/- 5 degrees C observed when 18% or no NaCl was injected (P <.02). In the 36% NaCl group, the entire tumor (5.2 cm +/- 0.8 diameter) was completely ablated in every case, with coagulation extending several centimeters into the surrounding tissues. By comparison, control tumors (without NaCl injection) contained coagulation measuring 3.1 cm +/- 0.2, surrounded by viable, well-perfused tumor (P <.01), and 36% NaCl alone produced 2.7 cm +/- 0.6 of patchy necrosis.


CONCLUSIONS
Pretreatment with intratumoral injection of small volumes of highly concentrated NaCl markedly increases RF heating and coagulation in a large animal tumor model. The complete destruction of tumors 5 cm in diameter or larger suggests that this substantial increase may be achieved for tumor ablation in clinical practice.
Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Muneeb
M
Ahmed
S Melvyn
SM
Lobo
Joseph
J
Weinstein
Jonathan B
JB
Kruskal
G Scott
GS
Gazelle
Elkan F
EF
Halpern
S Karim
SK
Afzal
Robert E
RE
Lenkinski
S Nahum
SN
Goldberg
D000818:Animals; D017115:Catheter Ablation; D004285:Dogs; D004553:Electric Conductivity; D006489:Hemostatic Techniques / Q000295:instrumentation*; D009336:Necrosis; D012044:Regression Analysis; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D012509:Sarcoma / Q000601:surgery*; D014685:Venereal Tumors, Veterinary / Q000601:surgery*
D012462:Saline Solution, Hypertonic