Simulated model of RAPID concept: highlighting innate inflammation and liver regeneration

Background

The resection and partial liver segment II/III transplantation with delayed total hepatectomy (RAPID) concept is a novel transplantation technique for removal of non‐resectable liver tumours. The aim of this study was to establish a simulated RAPID model to explore the mechanism involved in the liver regeneration.

Methods

A RAPID model was created in rats involving cold ischaemia and reperfusion of the selected future liver remnant (FLR), portal vein ligation, followed by resection of the deportalized lobes in a second step. Histology, liver regeneration and inflammatory markers in RAPID‐treated rats were compared with those in controls that underwent 70 per cent hepatectomy with the same FLR size. The effects of interleukin (IL) 6 and macrophage polarization on hepatocyte viability were evaluated in an in vitro co‐culture system of macrophages and BRL hepatocytes.

Results

The survival rate in RAPID and control hepatectomy groups was 100 per cent. The regeneration rate was higher in the RAPID‐treated rats, with higher levels of IL‐6 and M1 macrophage polarization (P < 0·050). BRL hepatocytes co‐cultured with M1 macrophages showed a higher proliferation rate through activation of the IL‐6/signal transducer and activator of transcription 3/extracellular signal‐regulated kinase pathway. This enhancement of proliferation was inhibited by tocilizumab or gadolinium trichloride (P < 0·050).

Conclusion

The surgical model provides a simulation of RAPID that can be used to study the liver regeneration profile.

Immediate and long-term impact of the COVID-19 pandemic on delivery of surgical services

Background

The ongoing pandemic is having a collateral health effect on delivery of surgical care to millions of patients. Very little is known about pandemic management and effects on other services, including delivery of surgery.

Methods

This was a scoping review of all available literature pertaining to COVID-19 and surgery, using electronic databases, society websites, webinars and preprint repositories.

Results

Several perioperative guidelines have been issued within a short time. Many suggestions are contradictory and based on anecdotal data at best. As regions with the highest volume of operations per capita are being hit, an unprecedented number of operations are being cancelled or deferred. No major stakeholder seems to have considered how a pandemic deprives patients with a surgical condition of resources, with patients disproportionally affected owing to the nature of treatment (use of anaesthesia, operating rooms, protective equipment, physical invasion and need for perioperative care). No recommendations exist regarding how to reopen surgical delivery. The postpandemic evaluation and future planning should involve surgical services as an essential part to maintain appropriate surgical care for the population during an outbreak. Surgical delivery, owing to its cross-cutting nature and synergistic effects on health systems at large, needs to be built into the WHO agenda for national health planning.

Conclusion

Patients are being deprived of surgical access, with uncertain loss of function and risk of adverse prognosis as a collateral effect of the pandemic. Surgical services need a contingency plan for maintaining surgical care in an ongoing or postpandemic phase.

Growth rates of pulmonary metastases after liver transplantation for unresectable colorectal liver metastases

Background

The previously reported SECA study demonstrated a dramatic 5-year survival improvement in patients with unresectable colorectal liver metastases (CLM) treated with liver transplantation (LT) compared with chemotherapy. The objective of this study was to assess whether immunosuppressive therapy accelerates the growth of pulmonary metastases in patients transplanted for unresectable CLM.

Methods

Chest CT scans from 11 patients in the SECA study resected for 18 pulmonary metastases were reviewed retrospectively. Tumour diameter, volume and CT characteristics were registered and tumour volume doubling time was calculated. Findings in the SECA group were compared with those of a control group consisting of 12 patients with non-transplanted rectal cancer resected for 26 pulmonary metastases. Disease-free survival (DFS) and overall survival (OS) after first pulmonary resection were determined.

Results

Median doubling time based on tumour diameter and volume in the SECA and control groups were 125 and 130 days (P = 0·658) and 110 and 129 days (P = 0·632) respectively. The metastases in both groups were distributed to all lung lobes and were mostly peripheral. Median DFS after LT in the SECA group and after primary pelvic surgery in the control group was 17 (range 6–42) and 18 (2–57) months respectively (P = 0·532). In the SECA group, estimated 5-year DFS and OS rates after first pulmonary resection were 39 and 51 per cent respectively.

Conclusion

Patients treated by LT for unresectable CLM have a good prognosis following resection of pulmonary metastases. Doubling time did not appear to be worse with the immunosuppression used after LT.

Experimental evaluation of liver regeneration patterns and liver function following ALPPS

Background

The underlying mechanism of liver regeneration after Associating Liver Partition and Portal vein ligation (PVL) for Staged hepatectomy (ALPPS) is still unclear. The aim of this study was to evaluate the relationship between future liver remnant (FLR) volume, liver regeneration characteristics and restoration of function in an experimental model of ALPPS.

Methods

An ALPPS model in rats was developed with selective PVL, parenchymal transection and partial hepatectomy (step 1), followed by resection of the liver (step 2). Three different ALPPS groups with FLR sizes of 30, 20 and 10 per cent of total liver volume were compared with sham‐operated controls and animals undergoing resection of left lateral lobe and 90 per cent PVL with respect to morbidity, mortality, liver regeneration and function.

Results

Three of 15 animals that had ALPPS with 10 per cent FLR (ALPPS10) died after step 1. Ascites developed in two of five rats that had ALPPS with 20 per cent FLR and in three of four animals in the ALPPS10 group after step 2. Although the relative increments in FLR size and growth rates were highest in the ALPPS groups, small FLR size was associated with a sustained increase in levels of serum aminotransferases and bilirubin, a lower albumin concentration, severe sinusoidal injury, increased expression of proliferation markers and increased activation of hepatic progenitor cells after step 2.

Conclusion

There is discordance between FLR volume increase and functional restoration after the ALPPS procedure.

Human regulatory T cells control TCR signaling and susceptibility to suppression in CD4+ T cells

Human CD4(+)CD25(hi)FOXP3(+) regulatory T cells maintain immunologic tolerance and prevent autoimmune and inflammatory immune responses. Regulatory T cells undergo a similar activation cycle as conventional CD4(+) T cells upon antigen stimulation. Here, we demonstrate that T cell receptors and costimulation are required to activate the regulatory T cell suppressive function. Regulatory T cells suppressed the T cell receptor signaling in effector T cells in a time-dependent manner that corresponded with inhibition of cytokine production and proliferation. Modulation of the activation level and thereby the suppressive capacity of regulatory T cells imposed distinct T cell receptor signaling signatures and hyporesponsiveness in suppressed and proliferating effector T cells and established a threshold for effector T cell proliferation. The immune suppression of effector T cells was completely reversible upon removal of regulatory T cells. However, the strength of prior immune suppression by regulatory T cells and corresponding T cell receptor signaling in effector T cells determined the susceptibility to suppression upon later reexposure to regulatory T cells. These findings demonstrate how the strength of the regulatory T cell suppressive function determines intracellular signaling, immune responsiveness, and the later susceptibility of effector T cells to immune suppression and contribute to unveiling the complex interactions between regulatory T cells and effector T cells.

Regulatory T cells that co-express RORγt and FOXP3 are pro-inflammatory and immunosuppressive and expand in human pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is highly infiltrated by CD4⁺T cells that express RORγt and IL-17 (T_H17). Compelling evidence from the tumor microenvironment suggest that regulatory T cells (T_reg) contribute to T_H17 mediated inflammation. Concurrently, PDAC patients have elevated levels of pro-inflammatory cytokines that may lead to T_H17 associated functional plasticity in T_reg. In this study, we investigated the phenotype and functional properties of T_reg in patients with PDAC. We report that PDAC patients have elevated frequency of FOXP3⁺T_reg, which exclusively occurred within the FOXP3⁺RORγt⁺T_reg compartment. The FOXP3⁺RORγt⁺T_reg retained FOXP3⁺T_reg markers and represented an activated subset. The expression of RORγt in T_reg may indicate a phenotypic switch toward T_H17 cells. However, the FOXP3⁺RORγt⁺T_reg produced both T_H17 and T_H2 associated pro-inflammatory cytokines, which corresponded with elevated T_H17 and T_H2 immune responses in PDAC patients. Both the FOXP3⁺T_reg and FOXP3⁺RORγt⁺T_reg from PDAC patients strongly suppressed T cell immune responses, but they had impaired anti-inflammatory properties. We conclude that FOXP3⁺RORγt⁺T_reg have a dual phenotype with combined pro-inflammatory and immunosuppressive activity, which may be involved in the pathogenesis of PDAC.

The association of early post-transplant glucose levels with long-term mortality

AIMS/OBJECTIVE

We aimed to assess the long-term effects of post-transplant glycaemia on long-term survival after renal transplantation.

METHODS

Study participants were 1,410 consecutive transplant recipients without known diabetes who underwent an OGTT 10 weeks post-transplant and were observed for a median of 6.7 years (range 0.3-13.8 years). The HRs adjusted for age, sex, traditional risk factors and transplant-related risk factors were estimated.

RESULTS

Each 1 mmol/l increase in fasting plasma glucose (fPG) or 2 h plasma glucose (2hPG) was associated with 11% (95% CI -1%, 24%) and 5% (1%, 9%) increments in all-cause mortality risk and 19% (1%, 39%) and 6% (1%, 12%) increments in cardiovascular (CV) mortality risk, respectively. Including both fPG and 2hPG in the multi-adjusted model the HR for 2hPG remained unchanged, while the HR for fPG was attenuated (1.05 [1.00, 1.11] and 0.97 [0.84, 1.14]). Compared with recipients with normal glucose tolerance, patients with post-transplant diabetes mellitus had higher all-cause and CV mortality (1.54 [1.09, 2.17] and 1.80 [1.10, 2.96]), while patients with impaired glucose tolerance (IGT) had higher all-cause, but not CV mortality (1.39 [1.01, 1.91] and 1.04 [0.62, 1.74]). Conversely, impaired fasting glucose was not associated with increased all-cause or CV mortality (0.79 [0.52, 1.23] and 0.76 [0.39, 1.49]). Post-challenge hyperglycaemia predicted death from any cause and infectious disease in the multivariable analyses (1.49 [1.15, 1.95] and 1.91 [1.09, 3.33]).

CONCLUSIONS/INTERPRETATION

For predicting all-cause and CV mortality, 2hPG is superior to fPG after renal transplantation. Also, early post-transplant diabetes, IGT and post-challenge hyperglycaemia were significant predictors of death. Future studies should determine whether an OGTT helps identify renal transplant recipients at increased risk of premature death.

EULID project: European living donation and public health

The choice of transplantation from a living donor offers advantages over a deceased donor. However, it also carries disadvantages related to donor risks in terms of health and safety. Furthermore, there are several controversial ethical aspects to be taken into account. Several national and international institutions and the scientific community have stated standards that have great influence on professional codes and legislations. Living organ donation and transplantation are to some extent regulated by parliamentary acts in most European countries. It is necessary to take a step forward to develop a legal framework to regulate all of these processes to guarantee the quality and to prevent illegal and nonethical practices. It is also necessary to develop and implement living donor protection practices not only in terms of physical health, but also to minimize potential impacts on the psychological, social, and economic spheres. Finally, an additional effort should be made to create a database model with recommendations for registration practices as part of the standardized follow-up care for the living donor. The European Living Donation (EULID) project's (http://www.eulivingdonor.eu/) main objective was to contribute to a European consensus to set standards and recommendations about legal, ethical, and living donor protection practices to guarantee the health and safety of living donors.

Double-balloon enteroscopy for endoscopic retrograde cholangiography in patients with a Roux-en-Y anastomosis

BACKGROUND AND STUDY AIMS

Double-balloon enteroscopy (DBE) has been proved to be effective for deep intubation of the small bowel. Patients with a Roux-en-Y enteroanastomosis and biliary problems have been a challenge in gastrointestinal practice because of the lack of endoscopic access to the biliary anastomosis. We report on the first case series of patients with Roux-en-Y anatomy who have been examined using DBE.

PATIENTS AND METHODS

Between September 2005 and May 2006, 18 endoscopic retrograde cholangiography procedures were performed in 13 patients (median age 53, range 2 - 81 years) using the DBE technique at our hospital. Most of the cases (10/13) had had a liver transplant for primary sclerosing cholangitis. The Fujinon T-series DBE system was used in all cases.

RESULTS

The entero-enteric anastomosis was reached easily in all 18 procedures, and the end of the Roux limb was reached in 17/18 procedures. The mean intubation time was 40 minutes (range 5 - 120 minutes). Adequate imaging was achieved in all but two cases, one of whom had a native papilla. Biliary stenting was performed in two patients, stent removal in three patients, and removal of a small stone in one patient.

CONCLUSIONS

Endoscopic access and biliary cannulation in the setting of Roux-en-Y anatomy is safe and feasible using the new DBE system for enteral intubation. Adaptation of accessories would further improve the utility of the procedure.

Calcineurin Inhibitor Avoidance with Daclizumab, Mycophenolate Mofetil, and Prednisolone in DR-Matched de Novo Kidney Transplant Recipients

BACKGROUND

Calcineurin inhibitor (CNI)-free regimens posttransplantation have been claimed to conserve graft function in addition to reduce the risk factors for cardiovascular and malignant disease in renal transplant recipients.

METHODS

The primary aim of this prospective, open-label, randomized, parallel-group, single-center study was to compare the effect of complete CNI-avoidance posttransplant (daclizumab + mycophenolate mofetil + prednisolone: Dac-group, n=27) with the standard CNI-based immunosuppressive protocol at our transplant unit (cyclosporine A + mycophenolate mofetil + prednisolone: CsA-group, n=27) on renal function (glomerular filtration rate [GFR] determined as plasma clearance of 51Cr-EDTA) in a selected low immunogenic risk population (DR-matched, PRA-negative de novo cadaveric transplant recipients).

RESULTS

There were no significant difference in GFR at week 10 (P=0.61), but GFR was significantly (P=0.029) lower in the Dac-group (52+/-20 ml/min) at month 12 than in the CsA-group (69+/-29 ml/min). One-year patient and graft survival did not differ between the two groups. Overall acute rejection rate was 70.4% (19/27) in the Dac-group and 29.6% (8/27) in the CsA-group (P=0.006).

CONCLUSIONS

The strategy to select DR-matched, PRA-negative de novo cadaveric transplant recipients for a CNI-avoidance protocol was not successful. The incidence of acute rejection was unacceptable high even though anti-CD25 antibody induction as well as initial higher mycophenolate mofetil doses (3 g/day) were applied, and renal function was significantly lower in the CNI-avoidance patients at 1 year. Other strategies need to be examined for avoidance of CNI's in the early posttransplant period.

Assessment of mucosal inflammation and blood flow in response to four weeks' intervention with probiotics in patients operated with a J-configurated ileal-pouch-anal-anastomosis (IPAA)

BACKGROUND

Pouchitis is a common and troublesome condition in patients operated on with ileal-pouch-anal-anastomosis (IPAA). A disturbed mucosal perfusion in the pouch has been suggested as a possible cause. Laser Doppler flowmetry (LDF) has been used successfully to measure gastric and colonic mucosal perfusion in humans. In a previous study, we demonstrated a reduced mucosal perfusion in the distal part of the pouch, during probiotic intervention, examined by LDF measurement. The aim of the present study was to confirm our previous results in a much larger material, and to compare the results of LDF measurements and inflammatory activity in ulcerative colitis (UC) patients with those in familial adenomatous polyposis (FAP) patients.

METHODS

Five hundred millilitres of a fermented milk product (Cultura), containing live lactobacilli (La-5) and bifidobacteria (Bb-12), was given daily for 4 weeks to 41 UC and 10 patients with FAP, operated on with IPAA. Mucosal perfusion was measured with LDF and the degree of inflammation was examined at predefined levels of the distal bowel by histology and faecal calprotectin measurements both before and after intervention. We also evaluated the applicability of a Pouchitis Disease Activity Index (PDAI).

RESULTS

The LDF measurements were reproducible in the pelvic pouch at each of the predefined levels, but did not change during intervention. Mucosal perfusion was significantly reduced in the distal compared to the proximal part of the pouch in the UC group (P < 0.05). The perfusion levels were higher in the FAP patients compared to the UC patientsat all predefined levels (P < 0.05). Calprotectin levels and histological score did not change significantlyafter intervention in any of the groups. The calprotectin level was significantly lower in the FAP compared to the UC group both before and after intervention. The PDAI decreased in both groups from alevel considered diagnostic for pouchitis to a level considered as not active pouchitis. The decreasewas significant for the UC patients.

CONCLUSIONS

The results did not demonstrate an effect of probiotics on histology, although a significant effect on the PDAI was achieved, which concurs with the previously reported effect on symptoms and endoscopic score. The significantly reduced blood flow in the UC group compared to the FAP group, operated on with the same procedure, and the significantly increased calprotectin levels in the UC group, are original findings. Both findings may be related to an increased risk for pouchitis among UC patients. The lack of effect of intervention on mucosal perfusion does not exclude a role for reduced circulation as a cause of pouchitis based on the reduced LDF measurements in the distal part of the pouch.

Assessment of mucosal inflammation and circulation in response to probiotics in patients operated with ileal pouch anal anastomosis for ulcerative colitis

BACKGROUND

Pouchitis is a common and troublesome condition, and a disturbed microbiological flora and mucosal blood flow in the pouch have been suggested as possible causes. Laser Doppler flowmetry (LDF) has been used successfully to measure gastric and colonic mucosal perfusion in humans. The aim of this study was to evaluate the effect of intervention with probiotics on ileal pouch inflammation and perfusion in the pouch, assessed by endoscopy, histology, fecal calprotectin and LDF.

METHODS

A fermented milk product (Cultura; 500 ml) containing live lactobacilli (La-5) and bifidobacteria (Bb-12) was given daily for 4 weeks to 10 patients operated with ileal-pouch-anal anastomosis (IPAA) for ulcerative colitis (UC). Mucosal perfusion was measured with LDF and the degree of inflammation was examined at predefined levels of the distal bowel by endoscopy and histology. Stool samples were cultured for lactobacilli and bifidobacteria and calprotectin were measured before and after intervention.

RESULTS

The LDF measurements were reproducible in the pelvic pouch at each of the predefined levels, but did not change after intervention. The mucosal perfusion was reduced in the distal compared to the proximal part of the pouch. Calprotectin levels did not change significantly after intervention. The median endoscopic score for inflammation was significantly reduced by 50% after intervention, whereas the histological score did not change significantly.

CONCLUSION

The results suggest that probiotics primarily act superficially, with change of gross appearance of the mucosa at endoscopy, but without significant effect on histological picture, mucosal perfusion or faecal calprotectin, during a relatively short period of 4 weeks.

Assessment of Mucosal Inflammation and Circulation in Response to Probiotics in Patients Operated with Ileal Pouch Anal Anastomosis for Ulcerative Colitis

BACKGROUND

Pouchitis is a common and troublesome condition, and a disturbed microbiological flora and mucosal blood flow in the pouch have been suggested as possible causes. Laser Doppler flowmetry (LDF) has been used successfully to measure gastric and colonic mucosal perfusion in humans. The aim of this study was to evaluate the effect of intervention with probiotics on ileal pouch inflammation and perfusion in the pouch, assessed by endoscopy, histology, fecal calprotectin and LDF.

METHODS

A fermented milk product (Cultura; 500 ml) containing live lactobacilli (La-5) and bifidobacteria (Bb-12) was given daily for 4 weeks to 10 patients operated with ileal-pouch-anal anastomosis (IPAA) for ulcerative colitis (UC). Mucosal perfusion was measured with LDF and the degree of inflammation was examined at predefined levels of the distal bowel by endoscopy and histology. Stool samples were cultured for lactobacilli and bifidobacteria and calprotectin were measured before and after intervention.

RESULTS

The LDF measurements were reproducible in the pelvic pouch at each of the predefined levels, but did not change after intervention. The mucosal perfusion was reduced in the distal compared to the proximal part of the pouch. Calprotectin levels did not change significantly after intervention. The median endoscopic score for inflammation was significantly reduced by 50% after intervention, whereas the histological score did not change significantly.

CONCLUSION

The results suggest that probiotics primarily act superficially, with change of gross appearance of the mucosa at endoscopy, but without significant effect on histological picture, mucosal perfusion or faecal calprotectin, during a relatively short period of 4 weeks.

[Local thrombolytic treatment of peripheral arterial thrombosis and embolism]

Local intra-arterial low-dose thrombolysis has become a therapeutic alternative for acute and subacute occlusion of vascular grafts and native vessels in the lower limbs. The series comprises 31 patients treated with Streptokinase as thrombolytic agent. Complete primary thrombolysis was achieved in 20 patients, whereas in 11 patients the outcome was only partially successful or a failure. Vascular stenoses were considered to precipitate thrombosis in 18 cases, and prompted percutaneous transluminal angioplasty after thrombolysis. Two-year patency was 48% (30-66%) in the total series and 74% (56-92%) among the patients with successful primary thrombolysis. There were no major complications. Five patients sustained local inguinal haemorrhage, of whom three required surgical revision. Local intra-arterial thrombolysis is an elaborate procedure associated with potential hazardous complications. It should be carried out in institutions with radiological and vascular surgical expertise.

[The recurrence frequency in inguinal hernia. A 10-year survival material]

Over a period of ten years, from 1980 to 1989, 701 hernioplasties were performed in 592 patients. 582 of these patients were available for follow-up examination (83%). The average follow-up was 10.3 years, median 10.2 years. The recurrence rate was 12%, 8% of the recurrences occurred after hernioplasties performed by specialists, and 13% after operations performed by surgeons in training. The results are discussed. The authors briefly review recent developments in hernia surgery.

Postocclusive hyperaemia in skin measured in pigs by laser Doppler: influence of site of arterial stenosis in the limb

OBJECTIVE

To investigate how site and severity of arterial stenosis, and distance between tourniquet and measuring probe influences the postocclusive hyperaemic response in limb skin recorded by laser Doppler.

DESIGN

Open study.

MATERIAL

Nine Norwegian Landrace pigs.

INTERVENTION

Experimental stenoses in the abdominal aorta, the external iliac and femoral arteries. The hyperaemic responses were recorded with the probe at two different distances from the tourniquet.

MAIN OUTCOME MEASURES

Curve pattern, relative reduction in flux between the two peaks in double humped curves, and time to peak hyperaemic flux.

RESULTS

Double humped curves were produced at all sites, but the blood pressure gradient required at the stenosis was greater the more proximal the stenosis. In distal stenoses there was a greater relative reduction in flux between the two peaks (p < 0.05). The time to peak hyperaemic flux was related to the gradient of the stenosis (mmHg) (r = 0.62, p < 0.0001), but was independent of its site. Increased distance between the tourniquet and the probe gave lower laser Doppler amplitudes and prolonged the time to peak hyperaemia in experiments with femoral artery stenosis (p < 0.05).

CONCLUSION

The hyperaemic response is governed by both the severity and the site of arterial stenosis. Stenoses distal to the tourniquet seem to impair the initial reperfusion more than comparable lesions proximal to the tourniquet. Time to reach peak hyperaemia is the single variable most closely related to the severity of the stenosis.

Correlation between peripheral vascular resistance and time to peak flow during reactive hyperaemia

Earlier studies have proposed that the time to reach peak hyperaemic flux recorded with laser Doppler (tp) is a simple and accurate method of evaluating ischaemic limbs and possibly a method of estimating the peripheral vascular resistance (PR). The aim of this study was to investigate the relationship between the tp and changes in limb vascular resistance caused by arterial stenosis. Forty postocclusive hyperaemia tests with arterial stenoses of different pressure gradients were performed in four pigs. A laser Doppler fluxmeter was used to record postocclusive hyperaemia in the skin of one hind limb. A specially designed tourniquet was used for the arterial occlusion. Proximal and distal to the occlusion level a snare was used to form different grades of stenosis. The PR (mmHg.ml-1.min-1) was either estimated by infusion of a known blood volume into the tested limb over a given time period with simultaneous measurement of pressure or calculated on the basis of measurements of limb blood flow and blood pressure gradients. The tp was closely related to total limb vascular resistance assessed by the blood infusion method (r = 0.83, p < 0.0003) and to the resistance calculated from volume blood flow and intraarterial pressures (r = 0.86, p < 0.0001). This study suggests that the tp accurately reflects limb vascular resistance in an experimental model. Thus tp may be used as a quantitative indicator of overall blood flow impairment, and should be evaluated in patients with lower-limb atherosclerosis.

[Ulcer surgery and anti-ulcer agents. Changes in surgical activities and sale of anti-ulcer agents in Nord-Trøndelag 1975-89]

During recent decades the number of operations for peptic ulcer has decreased significantly. The incidence of operations for peptic ulcer or related complications during the period 1975-89 in persons older than 15 years was investigated in the Nord-Trøndelag region of Norway, with a population of approximately 100,000. The number of elective surgical procedures decreased by 72% from 1975 to 1989. The greatest reduction was found for duodenal ulcers. The incidence of acute operations decreased by 35%. The main reason was fewer surgical interventions in patients with haemorrhage, since the number of operations for perforation remained almost constant during the period of 15 years. The reduction in surgical treatment can be explained mainly by the introduction of new H2-antagonists in the seventies, leading to more successful pharmacological treatment of peptic ulcer.

Infusion methods for determination of peripheral resistance: influence of infused medium and back pressure

It has been suggested that peripheral vascular resistance (PR), measured intraoperatively, can predict the outcome of infrainguinal reconstructions. There is, however, a great deal of variability in design and predictive value with this method, and it is prone to technical difficulties and possible errors. The present study evaluated the influence of the choice of infusion medium and the back pressure on PR as measured by the infusion technique. In a porcine model of experimentally induced stenosis, standard PR (calculated by the pressure difference across the stenosis and the Doppler volume flow) was compared with PR based on infusions of blood or saline solution. With blood as the infusion medium there was a significant correlation between the PR and the standard values (r = 0.795, p = 0.0005), whereas there was no correlation when saline solution was infused (r = 0.067, p = 0.345). Subtracting the back pressure resulted in a slight improvement in the correlations between standard PR and PR measured after infusion of blood but not saline solution. In summary, blood should be used as an infusion medium in methods of PR determination, but the influence of back pressure remains uncertain.

Human bronchial perfusion evaluated with endoscopic laser Doppler flowmetry

Endoscopic laser Doppler flowmetry (LDF) was used to study human bronchial microvascular perfusion in 25 healthy subjects. In total 617 recordings with good signal to noise ratio were obtained and, in the hands of an experienced bronchoscopist, the procedure did not cause major technical problems. Curve fluctuations synchronous to heart rate and respiration were identified. The spatial variation of measurements in one region was considerable, but when the mean of four measurements was used, acceptable precision levels were obtained. Regional differences were observed between 40.3 arbitrary perfusion units (PU) (34.0-46.6) in the right upper lobe bronchus and 77.3 PU (63.6-91.0) at the main carina. Measurements were obtained from the main carina, the right upper lobe bronchus, the apical segment of the right and left lower lobe bronchus. In all bronchi, recordings were performed at two locations distal to the bifurcation; 1-5 mm (central) and 6-10 mm (peripheral). The peripheral flux levels were significantly higher than the central (p < 0.001). Analysis of the short and long term temporal variation showed no significant differences, when the data was analyzed on a group basis. We conclude that LDF seems to be a promising method for future clinical investigations.

Laser Doppler flux and tissue oxygen tension as indicators of colonic perfusion in pigs

OBJECTIVE

To evaluate laser Doppler flowmetry (LDF) and tissue oximetry (TpO2) for intraoperative assessment of colonic perfusion in pigs.

MATERIAL

Eight pigs weighing from 19-22 kg.

INTERVENTIONS

Relationships of laser Doppler flux and TpO2 to mean arterial pressure (MAP) were measured in porcine sigmoid colon. The influence of different fractional inspired oxygen concentrations (FiO2) and the variability of the laser Doppler flux were evaluated.

RESULTS

Highly significant reproducible non-linear perfusion compared with pressure relations were found with both methods (r > or = 0.9, p < 0.0001). There was a rapid decrease when MAP fell below 90 mmHg. The dependency of TpO2 on FiO2 was omitted by using the ratio TpO2:PaO2. The coefficient of variation of repeated LDF recordings of 30 second duration with the hand held probe was 0.11 (0.07-0.16) (median and 95% confidence interval). Three recordings gave a reproducible mean flux with an estimated precision of 10% either way. Simultaneous recordings with sutured and hand-held probes correlated well (r > or = 0.9, p < or = 0.01).

CONCLUSION

Both methods yielded quantitative and reproducible intraoperative assessments of colonic perfusion, and are applicable for clinical use.

The significance of probe design in evaluation of colonic perfusion with laser Doppler flowmetry

The significance of probe design for laser Doppler flowmetry measurement depth and variation was investigated by determining flux versus pressure relations and spatial variability with various probes placed on the serosal surface of porcine sigmoid colon. For two large probes (three optical fibers with diameter and center separation > or = 500 microns) the flux versus pressure relations showed autoregulation, indicating that the mucosal perfusion contributed to the flux signal. The curves were reproducible between individuals. With two smaller probes linear flux versus pressure relations were obtained, indicating a shallow measurement not influenced by the autoregulated mucosal perfusion. The spatial variation expressed as coefficients of variation of repeated recordings at each pressure level was significantly greater with the smaller probes (p < 0.001). For clinical use the larger probes should be preferred. These include all wall layers, and only 3 repeated recordings are needed to obtain a reproducible mean flux value within +/- 10%, as opposed to 10 with the smaller probes.

Intraoperative prediction of ischaemic injury of the bowel: a comparison of laser Doppler flowmetry and tissue oximetry to histological analysis

Intraoperative diagnosis of inadequate colonic perfusion would contribute to prevention of ischaemic colitis after abdominal aortic reconstructions. The aim of this study was to evaluate laser Doppler flowmetry (LDF) and tissue oximetry (TpO2) as predictors of the development of bowel necrosis. Devascularised loops of colon and ileum in anaesthetised pigs were divided into 10-20 mm segments and measurements of laser Doppler flux and TpO2 were performed in each segment. After 7 h of ischaemia the segments were resected for histological and biochemical analysis. In 65 colonic and 58 ileal segments a significantly lower flux was found in segments with necrosis of greater than or equal to 30% of the mucosal thickness compared to segments with necrosis of less than or equal to 10% (p less than 0.01). The discriminant flux value was 50 perfusion units, confirming a previous clinical study. The specificity was 0.96 and the sensitivity 0.94. Flux was inversely correlated to tissue lactate concentration. Significantly lower TpO2 was found in 19 colonic segments with necrosis of greater than or equal to 30% of mucosa compared to 19 colonic segments with necrosis of less than or equal to 10% (p less than 0.01). Using a discriminant value of 5kPa, a specificity of 0.79, and a sensitivity of 0.95 were calculated. In 27 ileum segments no significant difference in TpO2 between different histological groups was found (p greater than 0.30). The results show that LDF and TpO2 can predict ischaemic injury of the colon, and LDF also of the small bowel.

Assessment of the physiological importance of iliac artery stenosis by laser Doppler flowmetry in pigs

OBJECTIVE

To test the hypothesis that a curve with two peak values (double hump) recorded by laser Doppler flowmetry over the skin of the lower limb during postocclusive hyperaemia reflects pathological vascular resistance in the aortoiliac segment.

DESIGN

Open study.

MATERIAL

Six Norwegian Landrace pigs.

INTERVENTION

Arterial stenoses were induced in the external iliac arteries.

MAIN OUTCOME MEASURES

Presence of double humped laser Doppler curves, relative decrease in laser Doppler flux between the two peaks, and time taken to reach peak hyperaemic flux.

RESULTS

Double humped curves were seen only when arterial stenoses were present. The relative decrease in laser Doppler flux between the two peaks, and the time to reach peak hyperaemic flux were related to the blood pressure gradient (mmHg) at the stenosis (r = 0.88 and 0.83, p less than 0.0001). The laser Doppler curve pattern can be explained by similar dynamic changes in arterial blood pressure distal to the tourniquet during hyperaemia.

CONCLUSION

These results confirm the hypothesis, and suggest that laser Doppler flowmetry recordings of postocclusive hyperaemia may be a non-invasive way of assessing the condition of the iliac artery.

Repeated measurement variation and precision of laser Doppler flowmetry measurements

The repeated measurement variation of laser Doppler flowmetry (LDF) recordings is essential for the precision level of the method in the assessment of tissue perfusion. The objective of this paper was to discuss the practical consequences of this problem by presenting a statistical method which can be used to estimate the number of replicates needed to reach a certain precision standard. By a repeated measures analysis of variance with a single-factor design, the mean variation of repeated measurements and its standard deviation were estimated. This estimate was used for simulation of a 95% confidence interval with length defined as a percentage of the mean of repeated measurements. The analyses were made in LDF samples performed in skin, gastric mucosa, and pig kidney in order to exemplify the use of the method. Paired values gave an unacceptable precision estimate in all tissues, but by increasing the number of replicates, the estimated precision was greatly enhanced. A preliminary recommendation for the practical use of LDF in the assessment of tissue perfusion is to perform at least four to six repeated measurements. Further studies are needed in order to establish methodological standards. The presented statistical considerations could also be relevant for other procedures used in microvascular research.

Aerobic endurance, anatomical factors and time properties of laser Doppler recorded skin postocclusive hyperaemia

Aerobic endurance capacity is partly dependent on blood supply to and metabolic capacity of the active muscles. Recordings of lower limb skin postocclusive hyperaemia with laser Doppler flowmetry can differentiate between patients with lower limb atherosclerosis and healthy controls. In this study, we investigated the relationship between aerobic endurance, calf volume, common femoral artery diameter and time properties of the postocclusive laser Doppler curve. A group of 16 healthy male subjects with values for aerobic endurance which varied from those of untrained men to elite endurance trained athletes were examined. Duration of laser Doppler recorded skin postocclusive hyperaemia was significantly correlated to both aerobic power and anaerobic threshold (P less than 0.01). Hyperaemia in subjects with large common femoral artery diameter was of shorter duration (P less than 0.05). The peak and mean body mass related blood flow during hyperaemia was correlated to anaerobic threshold (P less than 0.05). These results were in agreement with previous studies indicating an effect of endurance training on the blood supply to the muscles concerned.