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J Thorac Cardiovasc Surg 2007;134:825-826
© 2007 The American Association for Thoracic Surgery

Letter to the Editor

Reply to the Editor

^a Department of Intensive Care, The Alfred Hospital, Melbourne, Victoria, Australia
^b Department of Allergy, Immunology, and Respiratory Medicine, The Alfred Hospital, Melbourne, Victoria, Australia

We thank Augoustides for his comments and thoughts about our article.¹ He notes the high mortality rate of those undertaking independent lung ventilation (ILV) and suggests that trials assessing early extubation with appropriate anesthetic modification may be a solution. Clearly in this retrospective case series we cannot assess causation; that is, we cannot say whether the use of ILV was actually harmful, nor whether in balance it increased mortality. We would contend that when ILV was initiated, patients had reached a point at which they could not be sustained without ILV (or in later years extracorporeal membrane oxygenation).

Mechanical ventilation is only justified when its benefits outweigh its risks. Inappropriately high tidal volumes are known to be harmful to lungs with adult respiratory distress syndrome, with an adverse effect on mortality.² This is also likely to be true for lung transplants. It has been our clinical experience that increased mechanical ventilation in the single-lung transplant with excessive dynamic hyperinflation and primary graft failure leads to increasing dynamic hyperinflation within the native lung and subsequent cardiovascular collapse. However, it is possible that there is also direct injury to the transplanted lung from inappropriate mechanical ventilation.

Delineating this can be difficult because, owing to the contribution of the native lung, a healthy patient with a functioning single graft has a lower arterial oxygen tension/inspired oxygen fraction (PaO ₂/FIO ₂) ratio than that of a "similar patient" with a double-lung transplant. At extubation, single-lung transplants have lower PaO ₂/FIO ₂ ratios than double-lung transplants.³ The intermediate outcomes in these 2 groups are similar. It has been suggested that the definition of primary graft failure should be changed to reflect this.⁴

Since the program began at the Alfred Hospital, there have been many advances in all aspects of lung transplantation. Anesthetic techniques have steadily evolved rather than undergoing "quantum" change over this time.⁵ Early extubation of appropriate candidates is often feasible,⁶ and we have practiced this where appropriate. Of the 170 patients in our study,¹ 22 (13%) were extubated in theater before admission to the intensive care unit. Some caution is needed, inasmuch as reperfusion pulmonary edema may not reach its peak for 24 to 48 hours after transplant.

The use of protocols and guidelines has consistently been shown to reduce duration of ventilation.⁷ We have recently introduced a guideline such as this at our hospital with the aim of minimizing the deleterious effects of inappropriate mechanical ventilation and unnecessary intravenous fluid administration to achieve improved graft function and facilitate early extubation.

We thank Dr Augoustides for his comments. Progress in this area will follow a collaborative, multicenter, and international approach to further define the best management of lung transplant recipients.

References

1. Pilcher DV, Auzinger GM, Mitra B, Tuxen DV, Salamonsen RF, Davies AR, et al. Predictors of independent lung ventilation: an analysis of 170 single-lung transplantations. J Thorac Cardiovasc Surg 2007;133:1071-1077.[Abstract/Free Full Text]
   
2. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network. N Engl J Med 2000;342:1301-1308.[Medline]
   
3. Oto T, Griffiths AP, Levvey BJ, Pilcher DV, Williams TJ, Snell GI. Definitions of primary graft dysfunction after lung transplantation: differences between bilateral and single lung transplantation. J Thorac Cardiovasc Surg 2006;132:140-147.[Abstract/Free Full Text]
   
4. Oto T, Levvey B, Snell GI. Potential refinements of The International Society for Heart And Lung Transplantation primary graft dysfunction grading system. J Heart Lung Transplant 2007;26:431-436.[Medline]
   
5. Myles PS, Snell GI, Westall GP. Lung transplantation. Curr Opin Anaesthesiol 2007;20:21-26.[Medline]
   
6. Rocca GD, Coccia C, Costa GM, Pompei L, Di Marco P, Pierconti F, et al. Is very early extubation after lung transplantation feasible?. J Cardiothorac Vasc Anesth 2003;17:29-35.[Medline]
   
7. Lellouche F, Mancebo J, Jolliet P, Roeseler J, Schortgen F, Dojat M, et al. A multicenter randomized trial of computer-driven protocolized weaning from mechanical ventilation. Am J Respir Crit Care Med 2006;174:894-900.[Abstract/Free Full Text]
   

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