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.
Ahmed
Muneeb
M
Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Lobo
S Melvyn
SM
Weinstein
Joseph
J
Kruskal
Jonathan B
JB
Gazelle
G Scott
GS
Halpern
Elkan F
EF
Afzal
S Karim
SK
Lenkinski
Robert E
RE
Goldberg
S Nahum
SN
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