- Email: [email protected]
Laser-Doppler Flowmetry in the Monitoring of the Human Intestinal Allograft: A Preliminary Report
Laser-Doppler Flowmetry in the Monitoring of the Human Intestinal Allograft: A Preliminary Report M. Oltean, G. Herlenius, G. Dindelegan, M. Gäbel, J. Mölne, O. Nilsson, A. Aneman, and M. Olausson ABSTRACT During acute rejection, graft endothelium becomes a prime target for recipient immune cells. Animal studies have shown reduced microvascular perfusion, probably due to increased endothelial-leukocyte interaction and endothelial impairment, leading to graft damage. Using laser-Doppler flowmetry (LDF), we correlated the microvascular blood flow in the intestinal mucosa of five patients receiving multivisceral grafts with clinical events and pathology results. Measurements (n ⫽ 75) were performed during the first 4 weeks posttransplantation by inserting the LDF flexible probe through the ileostomy for 25 to 30 cm. Forty-six of the 75 measurements were performed within 24 hours of endoscopy and biopsy. In uncomplicated cases, we recorded a gradual increase in mucosal perfusion during the first week posttransplantation that presumably reflected regeneration after reperfusion injury. Increased mucosal perfusion did not seem to correlate with rejection or other adverse clinical events. Sudden and sustained decreases in mucosal perfusion by 30% or more compared to the previous measurements were associated with septic episodes, rejection, or both. LDF revealed a good sensitivity in monitoring the intestinal microcirculation. It was able to indicate perfusion changes associated with acute rejection. The relatively low specificity of LDF may be compensated by the low invasivity, allowing frequent investigation. LDF may be an additional tool for routine monitoring of intestinal allografts.
A
CUTE REJECTION (AR) is the greatest risk factor for intestinal allograft survival. Its early recognition is a key issue in the management of the patients receiving intestinal allografts because progression to severe rejection is rarely reversible and carries a dark prognosis. As reliable serum assays are not yet available, graft surveillance relies heavily on frequent endoscopies and biopsies. These procedures carry significant invasivity, require expertise, need considerable time, and engender high costs. During AR, graft endothelium becomes a primary target for recipient immune cells. Animal studies have revealed reductions in microvascular perfusion1,2; microscopic examination evidenced morphologic changes in the microvasculature in the setting of AR.3 We sought to explore whether laser Doppler flowmetry (LDF) detected microvascular alterations occurring during acute rejection of intestinal allograft in humans and ultimately could be used to monitor the intestinal allografts. PATIENTS AND METHODS Using LDF, we monitored the microcirculation in the intestinal mucosa of five consecutive patients undergoing multivisceral trans-
plantation. Patients received antithymocyte globulin induction. Targeted tacrolimus levels were 10 to 15 ng/mL with no steroids administered routinely. Patient characteristics are summarized in Table 1. Briefly, the principle of LDF relies on changes in wavelength (Doppler shift) of a laser beam that hits moving red blood cells. The magnitude and frequency of these changes are directly related to the speed and number of the blood cells. Reflected light is captured by a returning fibre, recorded, and analyzed by a computer program (Perisoft, Perimed AB Järfälla, Sweden). A flexible fiberoptic probe is advanced through the ileostomy for 25 to 30 cm, then gradually redrawn. Mucosal blood flow is measured at different locations with results expressed as arbitrary perfusion units and a mean calculated for each recording. Seventy-five recordings were performed over the first 4 weeks From the Departments of Transplantation and Liver Surgery (M.O., G.H., G.D., M.G., M.O.), Anesthesia and Intensive Care (A.A.), and Pathology (J.M., O.N.), Sahlgrenska University Hospital, Göteborg, Sweden. Supported by funds from Sahlgrenska University Hospital (LUA). Address reprint requests to Dr Mihai Oltean, Department of Transplantation and Liver Surgery, Sahlgrenska University Hospital, 41345 Göteborg, Sweden. E-mail: [email protected]
© 2006 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/06/$–see front matter doi:10.1016/j.transproceed.2006.05.001
Transplantation Proceedings, 38, 1723–1725 (2006)
1723
1724
OLTEAN, HERLENIUS, DINDELEGAN ET AL Table 1. Patient Characteristics
RESULTS
Patient
Age
Gender
Diagnosis
Transplant Type
1
58
F
Multivisceral Tx
2
40
F
3
67
F
4
44
M
5
37
F
Neuroendocrine pancreatic tumor with liver metatases Crohns’ disease, short bowel syndrome Chronic intestinal pseudoobstruction Neuroendocrine pancreatic tumor with liver metatases Chronic intestinal pseudoobstruction, short bowel syndrome
Multivisceral Tx Multivisceral Tx Multivisceral Tx
Multivisceral Tx
posttransplantation. Forty-six of 75 recordings were performed within 24 hours from endoscopy and biopsy. We correlated the results with other parameters, namely, blood pressure, immunosuppression, C reactive protein, white blood cell count, and hemoglobin concentration, as well as significant clinical events.
Mucosal perfusion showed an increase throughout the first week posttransplantation and eventually stabilized at levels specific for each patient. At the time of all measurements, systolic blood pressure was above 90 mm Hg. In patient 3, we recorded a biopsy-proven episode of moderate AR. Compared to the previous examinations, mucosal microvascular perfusion recorded a 30% drop on the day before the diagnostic biopsy. Mucosal blood flow slowly recovered after antirejection therapy (steroid bolus, OKT3), returning to baseline after about 1 week. In patient 5, mucosal perfusion did not show an initial increase, as was seen in the other patients but gradually decreased. Moreover, tacrolimus levels were always below the target. A biopsy taken on day 7 showed severe rejection, which was successfully treated. Mucosal microvascular perfusion slowly recovered, reaching levels comparable to other patients having an uncomplicated course. Perfusion also declined in sepsis and during transient, unexplained episodes of hypoperfusion revealed by LDF, endoscopy, or histological examination (Fig 1).
Fig 1. Overview of the LDF results and clinical events over the first 4 weeks posttransplantation. Perfusion is expressed as arbitrary perfusion units (PU). AR, acute rejection; S, sepsis; P, pancreatitis. In patient 2, monitoring discontinuation at day 19 posttransplant was due to logistical problems.
LASER-DOPPLER FLOWMETRY IN INTESTINE
Graft perfusion did not change significantly during localized intraabdominal infections (pancreatitis, abscesses). At the time of all measurements, systolic blood pressure was above 90 mm Hg. Overall there was no correlation between the tacrolimus level, the CRP, the blood pressure, and the mucosal perfusion, probably due to the limited number of observations on each patient. However, over several intervals there was a direct proportionality between tacrolimus levels and mucosal perfusion that was close to statistical significance. DISCUSSION
In the present study we sought to determine a pattern for the microvascular perfusion of intestinal allografts following multivisceral transplantation using a novel, minimally invasive approach. Consistent with a study using orthogonal polarized spectral imaging,4 the current report noted that microvascular damage resolved gradually over the first 3 to 4 days posttransplantation. At several days after transplantation, mucosal perfusion stabilized at levels specific for each patient, remaining relatively constant during an uncomplicated course (individual baseline value). The most important finding is that the decreased mucosal perfusion during acute rejection was revealed by LDF. This reduced perfusion, which exceeded 35% compared with previous measurements, recovered following antirejection therapy. However, the technique showed a relatively low specificity because LDF, also demonstrated decreased perfusion in sepsis and other, ambiguous circumstances. Another shortcoming was the limited segment explored. However, as
1725
experimental and clinical evidence suggested uniform distribution of impaired microcirculation during AR in contrast with the patchy histological changes, we believe that our results obtained from the distal 25 to 30 cm are representative of the entire graft. LDF is expeditious, painless, and well tolerated by the patient. It provides a means to quantify and compare assessments on microcirculation and perfusion as real-time information. The thin, flexible probe allowed serial measurements at multiple levels with minimal tissue manipulation. The technique may be used for routine monitoring, providing an early alert on incipient changes. Interfering factors can be identified and diminished during recordings through careful consideration of other relevant parameters, namely, vascular resistance, mean arterial pressure, hematocrit, vasoactive medication and through identification of a baseline level by a few iterative measurements over several days. REFERENCES 1. Stojanovic T, Schlemminger R, Bedke J, et al: In vivo changes in acute rejection of rat small bowel allografts. Transplant Proc 32:1247, 2000 2. Dindelegan G, Liden H, Kurlberg G, et al: Laser-Doppler flowmetry is reliable for early diagnosis of small bowel acute rejection in the mouse. Microsurgery 23:233, 2003 3. Ruiz P, Garcia M, Pappas P, et al: Mucosal vascular alterations in isolated small bowel allografts: relationship to humoral sensitization. Transplant Proc 34:869, 2002 4. Cautero N, Gelmini R, Villa E, et al: Orthogonal polarization spectral imaging: a new tool in morphologic surveillance in intestinal transplant recipients. Transplant Proc 34:922, 2002
A
CUTE REJECTION (AR) is the greatest risk factor for intestinal allograft survival. Its early recognition is a key issue in the management of the patients receiving intestinal allografts because progression to severe rejection is rarely reversible and carries a dark prognosis. As reliable serum assays are not yet available, graft surveillance relies heavily on frequent endoscopies and biopsies. These procedures carry significant invasivity, require expertise, need considerable time, and engender high costs. During AR, graft endothelium becomes a primary target for recipient immune cells. Animal studies have revealed reductions in microvascular perfusion1,2; microscopic examination evidenced morphologic changes in the microvasculature in the setting of AR.3 We sought to explore whether laser Doppler flowmetry (LDF) detected microvascular alterations occurring during acute rejection of intestinal allograft in humans and ultimately could be used to monitor the intestinal allografts. PATIENTS AND METHODS Using LDF, we monitored the microcirculation in the intestinal mucosa of five consecutive patients undergoing multivisceral trans-
plantation. Patients received antithymocyte globulin induction. Targeted tacrolimus levels were 10 to 15 ng/mL with no steroids administered routinely. Patient characteristics are summarized in Table 1. Briefly, the principle of LDF relies on changes in wavelength (Doppler shift) of a laser beam that hits moving red blood cells. The magnitude and frequency of these changes are directly related to the speed and number of the blood cells. Reflected light is captured by a returning fibre, recorded, and analyzed by a computer program (Perisoft, Perimed AB Järfälla, Sweden). A flexible fiberoptic probe is advanced through the ileostomy for 25 to 30 cm, then gradually redrawn. Mucosal blood flow is measured at different locations with results expressed as arbitrary perfusion units and a mean calculated for each recording. Seventy-five recordings were performed over the first 4 weeks From the Departments of Transplantation and Liver Surgery (M.O., G.H., G.D., M.G., M.O.), Anesthesia and Intensive Care (A.A.), and Pathology (J.M., O.N.), Sahlgrenska University Hospital, Göteborg, Sweden. Supported by funds from Sahlgrenska University Hospital (LUA). Address reprint requests to Dr Mihai Oltean, Department of Transplantation and Liver Surgery, Sahlgrenska University Hospital, 41345 Göteborg, Sweden. E-mail: [email protected]
© 2006 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/06/$–see front matter doi:10.1016/j.transproceed.2006.05.001
Transplantation Proceedings, 38, 1723–1725 (2006)
1723
1724
OLTEAN, HERLENIUS, DINDELEGAN ET AL Table 1. Patient Characteristics
RESULTS
Patient
Age
Gender
Diagnosis
Transplant Type
1
58
F
Multivisceral Tx
2
40
F
3
67
F
4
44
M
5
37
F
Neuroendocrine pancreatic tumor with liver metatases Crohns’ disease, short bowel syndrome Chronic intestinal pseudoobstruction Neuroendocrine pancreatic tumor with liver metatases Chronic intestinal pseudoobstruction, short bowel syndrome
Multivisceral Tx Multivisceral Tx Multivisceral Tx
Multivisceral Tx
posttransplantation. Forty-six of 75 recordings were performed within 24 hours from endoscopy and biopsy. We correlated the results with other parameters, namely, blood pressure, immunosuppression, C reactive protein, white blood cell count, and hemoglobin concentration, as well as significant clinical events.
Mucosal perfusion showed an increase throughout the first week posttransplantation and eventually stabilized at levels specific for each patient. At the time of all measurements, systolic blood pressure was above 90 mm Hg. In patient 3, we recorded a biopsy-proven episode of moderate AR. Compared to the previous examinations, mucosal microvascular perfusion recorded a 30% drop on the day before the diagnostic biopsy. Mucosal blood flow slowly recovered after antirejection therapy (steroid bolus, OKT3), returning to baseline after about 1 week. In patient 5, mucosal perfusion did not show an initial increase, as was seen in the other patients but gradually decreased. Moreover, tacrolimus levels were always below the target. A biopsy taken on day 7 showed severe rejection, which was successfully treated. Mucosal microvascular perfusion slowly recovered, reaching levels comparable to other patients having an uncomplicated course. Perfusion also declined in sepsis and during transient, unexplained episodes of hypoperfusion revealed by LDF, endoscopy, or histological examination (Fig 1).
Fig 1. Overview of the LDF results and clinical events over the first 4 weeks posttransplantation. Perfusion is expressed as arbitrary perfusion units (PU). AR, acute rejection; S, sepsis; P, pancreatitis. In patient 2, monitoring discontinuation at day 19 posttransplant was due to logistical problems.
LASER-DOPPLER FLOWMETRY IN INTESTINE
Graft perfusion did not change significantly during localized intraabdominal infections (pancreatitis, abscesses). At the time of all measurements, systolic blood pressure was above 90 mm Hg. Overall there was no correlation between the tacrolimus level, the CRP, the blood pressure, and the mucosal perfusion, probably due to the limited number of observations on each patient. However, over several intervals there was a direct proportionality between tacrolimus levels and mucosal perfusion that was close to statistical significance. DISCUSSION
In the present study we sought to determine a pattern for the microvascular perfusion of intestinal allografts following multivisceral transplantation using a novel, minimally invasive approach. Consistent with a study using orthogonal polarized spectral imaging,4 the current report noted that microvascular damage resolved gradually over the first 3 to 4 days posttransplantation. At several days after transplantation, mucosal perfusion stabilized at levels specific for each patient, remaining relatively constant during an uncomplicated course (individual baseline value). The most important finding is that the decreased mucosal perfusion during acute rejection was revealed by LDF. This reduced perfusion, which exceeded 35% compared with previous measurements, recovered following antirejection therapy. However, the technique showed a relatively low specificity because LDF, also demonstrated decreased perfusion in sepsis and other, ambiguous circumstances. Another shortcoming was the limited segment explored. However, as
1725
experimental and clinical evidence suggested uniform distribution of impaired microcirculation during AR in contrast with the patchy histological changes, we believe that our results obtained from the distal 25 to 30 cm are representative of the entire graft. LDF is expeditious, painless, and well tolerated by the patient. It provides a means to quantify and compare assessments on microcirculation and perfusion as real-time information. The thin, flexible probe allowed serial measurements at multiple levels with minimal tissue manipulation. The technique may be used for routine monitoring, providing an early alert on incipient changes. Interfering factors can be identified and diminished during recordings through careful consideration of other relevant parameters, namely, vascular resistance, mean arterial pressure, hematocrit, vasoactive medication and through identification of a baseline level by a few iterative measurements over several days. REFERENCES 1. Stojanovic T, Schlemminger R, Bedke J, et al: In vivo changes in acute rejection of rat small bowel allografts. Transplant Proc 32:1247, 2000 2. Dindelegan G, Liden H, Kurlberg G, et al: Laser-Doppler flowmetry is reliable for early diagnosis of small bowel acute rejection in the mouse. Microsurgery 23:233, 2003 3. Ruiz P, Garcia M, Pappas P, et al: Mucosal vascular alterations in isolated small bowel allografts: relationship to humoral sensitization. Transplant Proc 34:869, 2002 4. Cautero N, Gelmini R, Villa E, et al: Orthogonal polarization spectral imaging: a new tool in morphologic surveillance in intestinal transplant recipients. Transplant Proc 34:922, 2002