Non-Invasive Monitoring of Tissue Oxygenation During Donor Nephrectomy
Background: Standard methods for assessment of organ viability during surgery are typically limited to visual cues and tactile feedback in open surgery. However, during laparoscopic surgery, these processes are impaired. This is of particular relevance during laparoscopic renal donation, where the condition of the kidney must be optimized despite considerable manipulation. However, there is no in vivo methodology to monitor renal parenchymal oxygenation during laparoscopic surgery.
Methods: We have developed a method for the real time, in vivo, whole organ assessment of tissue oxygenation during laparoscopic nephrectomy to convey meaningful biological data to the surgeon during laparoscopic surgery. We apply the 3-CCD (charge coupled device) camera to monitor qualitatively renal parenchymal oxygenation with potential real-time video capability.
Results: We have validated this methodology in a porcine model across a range of hypoxic conditions, and have then applied the method during clinical laparoscopic donor nephrectomies during clinically relevant pneumoperitoneum. 3-CCD image enhancement produces mean region of interest (ROI) intensity values that can be directly correlated with blood oxygen saturation measurements (R > 0.96). The calculated mean ROI intensity values obtained at the beginning of the laparoscopic nephrectomy do not differ significantly from mean ROI intensity values calculated immediately before kidney removal (p > 0.05).
Conclusion: Here, using the 3-CCD camera, we qualitatively monitor tissue oxygenation. This means of assessing intraoperative tissue oxygenation may be a useful method to avoid unintended ischemic injury during laparoscopic surgery. Preliminary results indicate that no significant changes in renal oxygenation occur as a result of pneumoperitoneum.

In the past 10 years the use of living donor kidneys have markedly increased and in 2003 surpassed deceased donors as the predominant source of donor organs. Laparoscopic donor nephrectomy has become a major driving force in increasing the acceptance of living donation. Laparoscopic donor nephrectomy (LDN) is thought to have several potential advantages over open donor nephrectomy (ODN). Namely, laparoscopic procedures require a shorter hospital stay, decreased amounts of analgesia, allow for a faster return to work and provide improved cosmesis. However, disadvantages of laparoscopic surgery include slightly longer warm ischemic times, and increased incidences of delayed graft function, the later thought to be the result of tissue hypoxia from pneumoperitoneum associated hypoperfusion and organ manipulation. These issues, while minor in most donors, are increasingly problematic in situations utilizing older donors, or organs intended for use in very small children. Many technical aspects of laparoscopic donation have been developed to minimize organ ischemic injury, and several parameters have been monitored to indirectly assess the general tolerance of pneumoperitoneum, including cardiac output, stroke volume, mean arterial pressure, urine output, systemic vascular resistance and end-tidal CO₂. All of the methodologies are limited by their inability to assess the organ directly. The most direct measurement would be that of whole organ oxygenation. Unfortunately, to date there has not been a method to evaluate tissue oxygenation laparoscopically in a time frame that is clinically relevant. The ability to intraoperatively monitor renal paranchyemal oxygenation would be useful in a number of clinical situations in which prompt resolution may have a dramatic effect. One such an example is encountered when during the course of the operation the blood supply to the organ becomes impaired by the technical manuevers done during dissection (i.e., approaching the vessels from the posterior aspect). Prompt recognition of decreased oxygenation would allow for repositioning of the kidney and re-establishment of blood flow. Other examples include the determination of secondary renal arteries and the establishment of a baseline acceptable pneumoperiotenum, potentially useful in older donors.

In this report, we describe the development of a means of directly assessing organ oxygenation during laparoscopic surgery. Spectroscopic information obtained by a standard 3-CCD camera used in laparoscopic surgery is processed thereby providing real time feedback to the surgeon using equipment readily available in any standard laparoscopic operating suite.