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Kidney stone movement during lithotripsy under general anaesthesia: High frequency jet ventilation versus spontaneous ventilation.

For patients receiving general anaesthesia for extracorporeal shockwave lithotripsy (ESWL), the technique of ventilating the lungs may influence the degree of movement of the calculus, which may in turn impact on the success of the treatment. For example, Warner et al (1) compared stone movement and shock requirements inpatients receiving intermittent positive pressure ventilation (IPPV) via an endotracheal tube (ETT) with those receiving high frequency jet ventilation (HFJV). They found that HFJV resulted in less stone movement and lower shock requirements. In the same year, Whelan et al (2) performed an in vitro study and showed in an experimental model that stationary stones exposed to shockwave lithotripsy fragmented more readily than moving stones. Since this time, spontaneous ventilation (SV) via a laryngeal mask airway (LMA) has surplanted IPPV via an ETT as many practitioners' general anaesthetic technique of choice. However, no study has compared stone movement using HFJV to that using SV via an LMA. We therefore conducted a small prospective randomized double-blind trial comparing stone movement during ESWL under general anaesthesia in patients breathing spontaneously via an LMA with those receiving HFJV via a Ben-Jet airway (Baldwin Medical, Knoxfield, Victoria).

Twelve patients were randomized to receive HFJV or SV The HFJV group received total intravenous anaesthesia. The SV group received inhalation maintenance of anaesthesia. Prior to commencement of ESWL and at predetermined intervals through the treatment, stone movement was recorded on a video recorder connected to the ultrasound machine. At a later time, an investigator blinded to group allocation reviewed the videotapes and estimated stone movement at each interval for each patient. The groups were then compared using a Mann-Whitney-U test with Bonferroni correction.

Group demographics were similar. The stones of patients in the SV group moved more than those of patients in the HFJV group (mean 5.4 mm vs 1.6 mm, P<0.01). This was statistically significant at all time intervals (P<0.05).

Our study is the first to compare stone movement during ESWL using SV or HFJV The stones in the SV group moved more than the HFJV group, but less than that reported using IPPV via an ETT (34 mm) (1). Further clinical research is required to ascertain whether the difference in stone movement that we measured is clinically relevant. Nevertheless, the theoretical consequences of excessive stone movement include higher total shock requirements for fragmentation, longer anaesthetic time, increased X-ray exposure due to a longer procedure and the possibility of perinephric tissue damage. Therefore, HFJV may be the preferred technique.

Acknowledgements: Thanks to Dr Maggie Wong (anaesthetist) and Mr Mark Salvatore (radiographer) for their assistance with this study.

References

(1.) Warner MA, Warner ME, Buck CF, Segura JW Clinical efficacy of high frequency jet ventilation during extracorporeal shock wave lithotripsy of renal and ureteric calculi: a comparison with conventional mechanical ventilation. J Urol 1988; 139:486-487.

(2.) Whelan JP, Gravenstein N, Welch JL, Lampotang S, Newman RC, Finlayson B. Simulation of ventilatory-induced stone movement and its effect on stone fracture during extracorporeal shock wave lithotripsy. J Urol 1988; 140:405-407.

D. J. OLIVE

J. R. CORMACK

Melbourne, Victoria
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Author:Olive, D.J.; Cormack, J.R.
Publication:Anaesthesia and Intensive Care
Date:Dec 1, 2006
Words:516
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