Do on-demand irrigation warmers provide an adequate intraoperative rate of irrigation for holmium enucleation of the prostate?

Introduction: On-demand irrigation warmers are widely used to provide a convenient way of irrigating warmed fluids for endoscopic procedure. However, concern has been raised that flow rates via these devices are inadequate for safe operating. Holmium enucleation of prostate (HoLEP) requires significant volume and flow rate of irrigation. Poiseuille’s Law states the resistance of a tube will result in reduced flow and a reduction in pressure across the tube. The aim was to compare the irrigation rates provided by one such warming device compared to a standard giving set whilst simulating HoLEP and to monitor intravesical pressure. Methods: A simulated apparatus was set up to replicate HoLEP surgery. Simulated design rather than ‘real-life’ apparatus was used to allow for repeated testing in a more controlled environment and to avoid other variables due to operative differences. Comparison of irrigation rate and pressure difference was measured whilst using a standard irrigation set (Fresenius Kabi) with pre-warmed fluid and the Ranger irrigation warming system (3M). Pressure was measured using a pressure line passed via the working channel of the laser resectoscope. Results: The standard giving set demonstrated lower resistance and higher irrigation rates. The irrigation rate was 31% higher (7.2 vs 5.5 ml/s). A lower change in pressure across the standard giving set was found (20 vs 38 cm H2O). The resistance therefore is much higher in the Ranger irrigation system, which gave a much slower flow and greater drop in pressure. Conclusion: This unique demonstration has led to a quantitative assessment of commonly used giving sets and has shown irrigation rates via a standard giving set are 31% greater than through the Ranger irrigation warming system. On-demand fluid warmers are felt to result in poor intraoperative vision and pose a potential risk to patient safety during HoLEP and other urological procedures requiring high fluid volumes.