Donor-dependent risk factors for early surgical complications after simultaneous pancreas-kidney transplantation

Outcome-Orientated Organ Allocation-A Composite Risk Model for Pancreas Graft Evaluation and Acceptance

Background: Pancreas transplantation (PTX) remains the most effective treatment to prevent long-term complications and provide consistent euglycemia in patients with endocrine pancreatic insufficiency, mainly in type I diabetic patients. Considering early graft loss (EGL) and the perioperative complication rate, an optimal risk stratification based on donor risk factors is paramount. Methods: In our single-center study, we retrospectively assessed the risk factors for EGL and reduced graft survival in 97 PTXs (82 simultaneous pancreas and kidney [SPK], 11 pancreases transplanted after kidney [PAK] and 4 pancreases transplanted alone [PTA]) between 2010 and 2021. By statistically analyzing the incorporation of different donor risk factors using the Kaplan-Meier method and a log-rank test, we introduced a composite risk model for the evaluation of offered pancreas grafts. Results: The overall EGL rate was 6.5%. In the univariate analysis of donor characteristics, age > 45 years, BMI > 25 kg/m2, lipase > 60 U/L, cerebrovascular accident (CVA) as the cause of death, mechanical cardiopulmonary resuscitation (mCPR), cold ischemia time (CIT) > 600 min and retrieval by another center were identified as potential risk factors; however, they lacked statistical significance. In a multivariate model, age > 45 years (HR 2.05, p = 0.355), BMI > 25 kg/m2 (HR 3.18, p = 0.051), lipase > 60 U/L (HR 2.32, p = 0.148), mCPR (HR 8.62, p < 0.0001) and CIT > 600 min (HR 1.89, p = 0.142) had the greatest impact on pancreas graft survival. We subsumed these factors in a composite risk model. The combination of three risk factors increased the rate of EGL significantly (p = 0.003). Comparing the pancreas graft survival curves for ≥3 risk factors to <3 risk factors in a Kaplan-Meier model revealed significant inferiority in the pancreas graft survival rate (p = 0.029). Conclusions: When evaluating a potential donor organ, grafts with a combination of three or more risk factors should only be accepted after careful consideration to reduce the risk of EGL and to significantly improve outcomes after PTX.

Elevated liver enzymes at the time of deceased donor organ donation do not affect recipient or pancreas allograft survival following pancreas transplantation

BACKGROUND

There is a lack of data on the impact of donor liver function tests (LFTs) on pancreas transplantation outcomes. Understanding their contribution could expand the donor pool.

METHODS

Using the UNOS database, data from January 2010-2022 was retrospectively analyzed. Multivariable cox regressions were performed to evaluate the association between LFTs (AST, ALT and total bilirubin levels), graft failure and mortality up to three years post-transplant.

RESULTS

9138 pancreas transplants were completed. Multivariate analysis showed no association between donor AST values > 500 U/L and increased rates of graft failure (p = 0.826) or mortality (p = 0.836). Similar findings were noted for donor ALT values > 500 U/L (p = 0.522 and p = 0.997, respectively). There was no correlation with graft failure (p = 0.322) or mortality (p = 0.423) for total bilirubin levels >3 mg/dL.

CONCLUSION

LFTs in the deceased pancreas donor did not increase risk of graft failure or mortality following pancreas transplantation. Elevated LFTs should not serve as absolute contraindications to transplant.

Exploring definitions of graft pancreatitis following pancreas transplantation: A scoping review

Despite the clinical relevance of graft pancreatitis (GP) after pancreas transplantation (PT), a universally accepted definition is lacking. Aim of this scoping review was to provide a systematic overview of GP definitions reported in the literature. MEDLINE, Web of Science and Embase were searched for relevant articles. Prospective/retrospective studies reporting a GP definition were included. The included series (n = 20) used four main criteria (clinical, biochemical, radiological and pathological) to define GP. Overall, 9 studies defined GP using a single criterion (n = 8 biochemical, n = 1 pathological), 7 series using two criteria (n = 3 clinical + biochemical, n = 3 biochemical + radiological, n = 1 clinical + radiological), 3 series using three criteria (n = 3 clinical + biochemical + radiological), and 1 series using four criteria. Overall, 20 definitions of GP were found. GP rate was reported by 19 series and ranged between 0% and 87%. This scoping review confirms that a universally accepted definition of GP is absent, and there is no consensus on the criteria on which it should be grounded. Future research should focus on developing a validated definition of GP.

Impact of Donor Age on Long-Term Outcomes in Simultaneous Pancreas-Kidney Transplantation

BACKGROUND

Simultaneous pancreas-kidney transplantation (SPKT) is the treatment of choice for type 1 diabetes patients with end-stage renal disease. Donor characteristics are determinants of graft and patient survival. We aimed to study the impact of donor age on outcomes in SPKT.

METHODS

We retrospectively studied 254 patients submitted to SPKT between 2000 and 2021. Patients were classified as "younger donor" (donor age <40 years) and "older donor" (donor age ≥40 years).

RESULTS

Fifty-three patients received grafts from older donors. Pancreas graft survival rates at 1, 5, 10, and 15 years were 89%, 83%, 77%, and 73% in the younger donor group, respectively, and 77%, 73%, 67%, and 62% in the older donor group, respectively (P = .052). Older donors and previous major adverse cardiovascular events (MACEs) were associated with pancreas graft failure at 15 years. Kidney transplant survival (1, 5, 10, and 15 years) was lower in the older donor cohort (94%, 92%, 69%, 60% vs 97%, 94%, 89%, and 84%, respectively; P = .004). Older donor, recipient age, and previous MACE predicted kidney graft failure at 15 years. Patient survival rates at 1, 5, 10, and 15 years were 98%, 95%, 91%, and 81% in the younger donor group, respectively, versus 92%, 90%, 84%, and 72% in the older donor group, respectively (P = .127).

CONCLUSIONS

The kidney graft survival rate was lower in the older donor group, whereas pancreas graft survival and patient survival did not differ significantly. Multivariate analysis showed that a donor age of ≥40 years was an independent predictor of pancreas and kidney graft failure at 15 years in SPKT patients.

Impact of Perioperative Prophylaxis With Enterococcus Activity on Risk of Surgical-Site Infection After Pancreas Transplantation

Surgical-site infection (SSI) is the most common early infectious complication after pancreas transplantation (PT). Although SSI has been shown to worsen outcomes, little data exist to guide optimal choices in perioperative prophylaxis.

Methods

We performed a retrospective cohort study of PT recipients from 2010-2020 to examine the effect of perioperative antibiotic prophylaxis with Enterococcus coverage. Enterococcus coverage included antibiotics that would be active for penicillin-susceptible Enterococcus isolates. The primary outcome was SSI within 30 d of transplantation, and secondary outcomes were Clostridioides difficile infection (CDI) and a composite of pancreas allograft failure or death. Outcomes were analyzed by multivariable Cox regression.

Results

Of 477 PT recipients, 217 (45.5%) received perioperative prophylaxis with Enterococcus coverage. Eighty-seven recipients (18.2%) developed an SSI after a median of 15 d from transplantation. In multivariable Cox regression analysis, perioperative Enterococcus prophylaxis was associated with reduced risk of SSI (hazard ratio [HR] 0.58; 95% confidence interval [CI], 0.35-0.96; P = 0.034). Anastomotic leak was also significantly associated with elevated risk of SSI (HR 13.95; 95% CI, 8.72-22.32; P < 0.001). Overall, 90-d CDI was 7.4%, with no difference between prophylaxis groups (P = 0.680). SSI was associated with pancreas allograft failure or death, even after adjusting for clinical factors (HR 1.94; 95% CI, 1.16-3.23; P = 0.011).

Conclusions

Perioperative prophylaxis with Enterococcus coverage was associated with reduced risk of 30-d SSI but did not seem to influence risk of 90-d CDI after PT. This difference may be because of the use of beta-lactam/beta-lactamase inhibitor combinations, which provide better activity against enteric organisms such as Enterococcus and anaerobes compared with cephalosporin. Risk of SSI was also related to anastomotic leak from surgery, and SSI itself was associated with subsequent risk of a poor outcome. Measures to mitigate or prevent early complications are warranted.

Pancreas Donor Risk Index and Preprocurement Pancreas Suitability Score for Prediction of Pancreas Transplant Outcomes

OBJECTIVES

The Pancreas Donor Risk Index and Preprocurement Pancreas Suitability Score were designed to assist in the evaluation of pancreases for transplant. Preprocurement Pancreas Suitability Score <17 and PancreasDonor Risk Index ≤1.57 were deemed ideal.We aimed to determine the ability ofthese scores to predict pancreas transplant outcomes.

MATERIALS AND METHODS

The Pancreas Donor Risk Index and the Preprocurement Pancreas Suitability Score were retrospectively calculated from a prospectively maintained database of consecutive pancreas transplants performed during a 13-year period (December 2004 to November 2017). Outcomes measuredwere rejection rate, graft and patient survival, and duration of hospital stay.

RESULTS

Of 159 pancreas transplants (108 simultaneous pancreas and kidney transplants, 33 pancreas after kidney transplants, 18 pancreas-only transplants), full data were available for 155 (97%) to calculate Pancreas Donor Risk Indexes and 129 (81%) to calculate Preprocurement Pancreas Suitability Scores. Fortyseven patients (30%) experienced at least 1 episode of acute rejection. We calculated Pancreas Donor Risk Indexes for 155 patients, and 19 (23%) and 27 (38%) were in the ≤1.57 and >1.57 groups, respectively (P = .047). We calculated Preprocurement Pancreas Suitability Scores for 129 patients, and 12 (21%) and 27 (32%) were in the <17 and ≥17 groups, respectively (P = .202). Donor age and recipientfemale sex were the main predictors forrejection (binary logistic regression, P < .05). One-year graft survival rates were 95% and 81% forthe ≤1.57 and >1.57 PancreasDonor Risk Index groups,respectively, and 95% and 80% forthe <17 and ≥17 Preprocurement Pancreas Suitability Score groups, respectively (not significant).

CONCLUSIONS

Pancreas Donor Risk Index and Preprocurement Pancreas Suitability Score were not helpful to predict graft/patient survival in our population. A higher Pancreas Donor Risk Index was associated with higher risk of graft rejection. Further studies with larger cohorts are required.

Impact of Histidine-Tryptophan-Ketoglutarate Versus University of Wisconsin Solution on the Outcome of Pancreas Transplant With Cold Ischemic Time ≥12 Hours: A Retrospective Study

OBJECTIVES

Histidine-tryptophan-ketoglutarate and University of Wisconsin solutions are currently used for pancreas graft preservation. Our hypothesis was whether the use of histidine-tryptophan-ketoglutarate solution is associated with worse pancreas graft survival than University of Wisconsin solution, in general and after prolonged cold ischemic time of ≥12 hours.

MATERIALS AND METHODS

This retrospective study investigated the impact of static cold storage in histidine-tryptophan-ketoglutarate (n = 133) versus University of Wisconsin (n = 107) solution on outcomes of 240 pancreas transplant procedures. Patient and graft survival rates were compared after 1, 3, and 5 years in both groups. Serum lipase, amylase, and C-reactive protein levels and incidence of surgical complications were evaluated at postoperative week 1. A subgroup analysis of 96 grafts (52 with histidine-tryptophanketoglutarate/44 with University of Wisconsin) with pancreas graft cold ischemic time ≥12 hours was also performed.

RESULTS

At mean follow-up of 75.2 ± 9.9 months, both groups demonstrated comparable short- and long-term patient survival. Overall, pancreas graft survival was slightly better in the histidine-tryptophan-ketoglutarate group (Kaplan-Meier analysis, log-rank P = .013). However, the subgroup analysis of grafts with cold ischemic time ≥12 hours showed slightly better pancreatic graft survival in the University of Wisconsin group, although not significantly (log-rank P = .95). Serum lipase and C-reactive protein levels at postoperative week 1 were higher in the histidinetryptophan-ketoglutarate group. Surgical complications were comparable. Multivariable Cox regression analysis identified neither solution as a risk factor affecting patient and graft survival.

CONCLUSIONS

Although a direct comparison between histidine-tryptophan-ketoglutarate and University of Wisconsin showed better pancreas graft survival with histidine-tryptophan-ketoglutarate, the multivariable analysis showed that the perfusion solution does not significantly influence patient and graft survival. However, in the analysis of transplants with cold ischemic time ≥12 hours, pancreas graft survival was slightly better in the University of Wisconsin group, although not significantly.

Risk indices predicting graft use, graft and patient survival in solid pancreas transplantation: a systematic review

BACKGROUND

Risk indices such as the pancreas donor risk index (PDRI) and pre-procurement pancreas allocation suitability score (P-PASS) are utilised in solid pancreas transplantation however no review has compared all derived and validated indices in this field. We systematically reviewed all risk indices in solid pancreas transplantation to compare their predictive ability for transplant outcomes.

METHODS

Medline Plus, Embase and the Cochrane Library were searched for studies deriving and externally validating risk indices in solid pancreas transplantation for the outcomes of pancreas and patient survival and donor pancreas acceptance for transplantation. Results were analysed descriptively due to limited reporting of discrimination and calibration metrics required to assess model performance.

RESULTS

From 25 included studies, discrimination and calibration metrics were only reported in 88% and 38% of derivation studies (n = 8) and in 25% and 25% of external validation studies (n = 12) respectively. 21 risk indices were derived with mild to moderate ability to predict risk (C-statistics 0.52-0.78). Donor age, donor body mass index (BMI) and donor gender were the commonest covariates within derived risk indices. Only PDRI and P-PASS were subsequently externally validated, with variable association with post-transplant outcomes. P-PASS was not associated with pancreas graft survival.

CONCLUSION

Most of the risk indices derived for use in solid pancreas transplantation were not externally validated (90%). PDRI and P-PASS are the only risk indices externally validated for solid pancreas transplantation, and when validated without reclassification measures, are associated with 1-year pancreas graft survival and donor pancreas acceptance respectively. Future risk indices incorporating recipient and other covariates alongside donor risk factors may have improved predictive ability for solid pancreas transplant outcomes.

Early intestinal complications following pancreas transplantation: lessons learned from over 300 cases - a retrospective single-center study

Enteric complications remain a major cause of morbidity in the post-transplant period of pancreas transplantation despite improvements surgical technique. The aim of this single-center study was to analyze retrospectively the early intestinal complications and their potential relation with vascular events. From 2000 to 2016, 337 pancreas transplants were performed with systemic venous drainage. For exocrine secretion, intestinal drainage was done with hand-sewn anastomosis duodenojejunostomy. Twenty-three patients (6.8%) had early intestinal complications. Median age was 39 years (male: 65.2%). Median cold ischemia time was 11 h [IQR: 9-12.4]. Intestinal complications were intestinal obstruction (n = 7); paralytic ileus (n = 5); intestinal fistula without anastomotic dehiscence (n = 3); ischemic graft duodenum (n = 3); dehiscence of duodenojejunostomy (n = 4); and anastomotic dehiscence in jejunum after pancreas transplantectomy (n = 1). Eighteen cases required relaparotomy: adhesiolysis (n = 6); repeated laparotomy without findings (n = 1); transplantectomy (n = 6); primary leak closure (n = 3); re-positioning of the graft (n = 1); and intestinal resection (n = 1). Of the intestinal complications, 4 were associated with vascular thrombosis, resulting in two pancreatic graft losses. Enteric drainage with duodenum-jejunum anastomosis is safe and feasible, with a low rate of intra-abdominal complications. Vascular thrombosis associated with intestinal complications presents a risk factor for the viability of pancreatic grafts, so prevention and early detection is vital.

Pancreas Donor Risk Index but Not Pre-Procurement Pancreas Allocation Suitability Score Predicts Pancreas Graft Survival: A Cohort Study from a Large German Pancreas Transplantation Center

Background

The pre-procurement pancreas allocation suitability score (P-PASS) was introduced to support clinical decision-making and ultimately expand the currently insufficient pancreas donor pool. The pancreas donor risk index (PDRI) can be used at the time of organ offering to predict one-year graft survival. Thus, this study aimed to analyze the validity of the PDRI and P-PASS in a large German transplant center.

Material/Methods

From 2002 to 2015, we performed 327 pancreas transplantations at our center. P-PASS and PDRI were calculated for 322 patients. To evaluate the pancreas graft survival, the patient cohort was divided into 2 P-PASS (<17, n=115 and ≥17, n=207) and 3 PDRI groups (<1, n=87; 1–1.5, n=133; and >1.5, n=102). Kaplan-Meier and Cox regression analyses were performed. We also examined differences regarding early pancreas graft failure for both scores using the chi-square test.

Results

The PDRI was associated with pancreas graft survival in the univariate analysis (p=0.023). In the multivariate analysis, a PDRI >1.5 was associated with significantly decreased graft survival (hazard ratio=1.792, 95% confidence interval=1.10–2.90, p=0.018). The P-PASS showed no significant association (p=0.081) with pancreas graft survival in the Kaplan-Meier survival analysis. There were significantly more early pancreas graft losses in the P-PASS ≥17 group (p=0.025).

Conclusions

Our results showed an association between P-PASS ≥17 and early pancreas graft failure. However, this does not apply to long-term pancreas graft survival; the PDRI proved to be a better tool for this, and PDRI values >1.5 were associated with significantly worse outcomes after pancreas transplantation.

An alternative technique of arterial anastomosis in mouse heart transplantation

OBJECTIVE

To investigate the characters and feasibility of continuous-interrupted suture (CIS) method for arterial anastomosis in mouse heart transplantation (MHT).

METHODS

A MHT model was adopted. End-to-end anastomosis of donor ascending aorta to recipient abdominal aorta was achieved by CIS or continuous suture (CS) method. In both groups, end-to-end anastomosis of pulmonary vein to inferior vena cava (IVC) was achieved by CS. Technical indexes and histological examination were analyzed between 2 groups.

RESULTS

The total operative time in CIS group was 92.83 ± 2.13 minutes, and in CS group was 92.40 ± 3.85 minutes. In CS group, artery anastomosis time was 20.13 ± 1.89 minutes; in CIS group, it was 20.36 ± 1.09 minutes. Additionally, venous anastomosis time in CS group was 14.80 ± 0.84 minutes, and in CIS group was 15.03 ± 0.85 minutes. Operation success rate in CIS group was 100%, and in CS group was 80%. There were no significant histological findings differences in graft between 2 groups. However, cell arrangement of anastomosis site was lightly irregular and the vascular alignment was poor in CS group. In CIS group, cell arrangement of anastomosis site was well arranged and vessels were well aligned.

CONCLUSIONS

CIS method could avoid arterial anastomosis-related complications induced by CS and improve the success rate.

What Is the Influence of Both Risk Donor and Risk Receiver on Simultaneous Pancreas-Kidney Transplantation?

INTRODUCTION

Some factors affect the pancreas of a marginal donor, and although their influence on graft survival has been determined, there is an increasing consensus to accept marginal organs in a controlled manner to increase the pool of organs. Certain factors related to the recipient have also been proposed as having negative influence on graft prognosis. The objective of this study was to analyze the influence of these factors on the results of our simultaneous pancreas-kidney (SPK) transplantation series.

MATERIALS AND METHODS

Retrospective analysis of 126 SPK transplants. Donors and recipients were stratified in an optimal group (<2 expanded donor criteria) and a risk group (≥2 criteria). A pancreatic graft survival analysis was performed using a Kaplan-Meier test and log-rank test. Prognostic variables on graft survival were studied by Cox regression. Postoperative complications (graded by Clavien classification) were compared by χ² test or Fisher test.

RESULTS

Median survival of pancreas was 66 months, with no significant difference between groups (P > .05). Multivariate analysis showed risk factors to be donor age, cold ischemia time, donor body mass index, receipt body mass index, and receipt panel-reactive antibody.

CONCLUSIONS

In our series, the use of pancreatic grafts from donors with expanded criteria is safe and has increased the pool of grafts. Different variables, both donor and recipient, influence the survival of the pancreatic graft and should be taken into account in organ distribution systems.

Surgery of pancreas transplantation

PURPOSE OF REVIEW

The surgical techniques of pancreas transplantation have been evolving and significantly improved over time. This article discusses different current techniques and their modifications.

RECENT FINDING

At this time, the most commonly used technique is systemic venous drainage (for venous outflow) and enteric drainage (for management of exocrine pancreatic secretions). However, new modifications of established techniques such as gastric or duodenal exocrine drainage and venous drainage to the inferior vena cava continue to be introduced.

SUMMARY

This article provides a state-of the-art review of the most prevalent up-to-date surgical techniques as well as a synopsis of their specific risks and benefits. The article also provides the most current registry data regarding utilization of different surgical techniques in the United State and worldwide.

Validation of the Pancreas Donor Risk Index for use in a UK population

Pancreas graft failure rates remain substantial. The PDRI can be used at the time of organ offering, to predict one-year graft survival. This study aimed to validate the PDRI for a UK population. Data for 1021 pancreas transplants were retrieved from a national database for all pancreas transplants. Cases were categorized by PDRI quartile and compared for death-censored graft survival. Significant differences were observed between the UK and US cohorts. The PDRI accurately discriminated graft survival for SPK and was associated with a hazard ratio of 1.52 (P = 0.009) in this group. However, in the PTA and PAK groups, no association between PDRI quartile and graft survival was observed. This is the largest study to validate the PDRI in a European cohort and has shown for the first time that the PDRI can be used as a tool to predict graft survival in SPK transplantation, but not PTA or PAK transplantation.

Pancreas transplantation: a treatment option for people with diabetes

Since the first pancreas transplants in the early 1960s, whole-organ pancreas transplantation, either alone or combined with kidney transplantation, has become commonplace in many countries around the world. Whole-organ pancreas transplantation is available in the UK, with ~200 transplants currently carried out per year. Patient survival and pancreas graft outcome rates are now similar to other solid organ transplant programmes, with high rates of long-term insulin independence. In the present review, we will discuss whole-pancreas transplantation as a treatment for diabetes, focusing on indications for transplantation, the nature of the procedure performed, graft survival rates and the consequences of pancreas transplantation on metabolic variables and the progression of diabetes-related complications.

Clinically significant peripancreatic fluid collections after simultaneous pancreas-kidney transplantation

BACKGROUND

Peripancreatic fluid collections (PPFC) are a serious complication after simultaneous pancreas-kidney transplantation (SPKTx).

METHODS

Retrospective study for all 223 SPKTx performed from December 8, 1996, to October 10, 2011, to evaluate the risk factors (RF) and impact of PPFCs on outcomes was conducted.

RESULTS

Clinically significant PPFCs were seen in 36 (16%) cases, all within 3 months after transplantation. Radiologic drainage resolved 2 (6%) cases, and 34 required laparotomy (mean [SD], 4 [7]). Compared with the non-PPFC group (n=186), the PPFC group had similar patient and total kidney graft survivals but significantly lower total pancreas survival (68% vs. 85%) and greater incidence of infections (75% vs. 46%, all P<0.05) at 5 years. PPFCs were associated with early graft pancreatitis in 18 (50%), pancreatic fistula in 20 (56%, 9 with obvious duodenal stump leak) and infection in the collection in 20 (56%) cases. Comparison of PPFCs with pancreas graft loss to the PPFCs with surviving grafts showed that the incidence of pancreatic fistula was greater in the former (90% pancreas graft loss vs. 42% pancreas graft survival, P<0.01). Binary logistic regression analysis of RF for developing PPFC showed a donor age >30 years to be significant (P=0.03; odds ratio, 3.4; confidence interval, 1.1-10.5) and a trend of association with donor body mass index >30 and pancreas cold ischemia time greater than 12 hr.

CONCLUSIONS

PPFCs are associated with significant reduction in pancreas allograft survival and impact resource use. Donor age >30 years is a significant RF for their development. PPFCs associated with pancreatic fistula carry a greater risk for pancreas graft loss.

A composite risk model for predicting technical failure in pancreas transplantation

Technical failure (TF) continues to have a significant impact on the success of pancreas transplantation. We assessed risk factors for TF in 1115 pancreas transplants performed at a single center between 1998 and 2011. The overall TF rate was 10.2%. In a multivariable model, donor BMI ≥ 30 (HR 1.87, p = 0.005), donor Cr ≥ 2.5 (HR 3.16, p = 0.007), donor age >50 (HR 1.73, p = 0.082) and preservation time >20 h (HR 2.17, p < 0.001) were associated with TF. Bladder drainage of exocrine secretions was protective (HR 0.54, p = 0.002). We incorporated these factors in a Composite Risk Model. In this model the presence of one risk factor did not significantly increase risk of TF (HR 1.35, p = 0.346). Two risk factors in combination increased risk greater than threefold (HR 3.65, p < 0.001) and three risk factors increased risk greater than sevenfold (HR 7.66, p = <0.001). The analysis also identified many factors that were not predictive of TF, including previous transplants, immunosuppressive agent selection, and almost all recipient demographic parameters. While the model suggests that two or more risk factors predict TF, strategies to reduce preservation time may mitigate some of this risk.