Multisensor perfusion assessment cohort study: Preliminary evidence toward a standardized assessment of indocyanine green fluorescence in colorectal surgery

Quantification of indocyanine green fluorescence angiography in colorectal surgery: a systematic review of the literature

BACKGROUND

Indocyanine green fluorescence angiography (ICGFA) during colorectal surgery associates with reduced post-operative anastomotic complication rates. Because its interpretation is subjective, quantification has been proposed to address inter-user variability. This study reviews the published literature regarding ICGFA quantification during colorectal surgery with a focus on impactful clinical deployment.

METHODS

A systematic review was performed of English language publications regarding clinical studies of ICGFA quantification in colorectal surgery in PubMed, Scopus, Web of Science and Cochrane Library on 29th August 2024, updated to 18th November 2024, following PRISMA guidelines. Newcastle Ottawa scale (NOS) was used to assess quality.

RESULTS

A total of 1428 studies were screened with 22 studies (1469 patients) selected. There was significant heterogeneity of ICGFA methodology, quantification methods and parameter selection and only three studies were NOS "high" quality. Extracorporeal application was most common. Four studies (154 patients) conducted real-time ICGFA analyses (others were post hoc) and four utilised artificial intelligence methods. Eleven studies only included patients undergoing left-sided resection (six focusing specifically on rectal resections). Only one study employed the quantification method to guide intra-operative decision-making regarding colonic transection. Twenty-six different perfusion parameters were assessed, with time from injection to visible fluorescence and maximum intensity the most commonly (but not only) correlated parameters regarding anastomotic complication (n = 18). Other grounding correlates were tissue oxygenation (n = 3, two with hyperspectral imagery), metabolites (n = 2) and surgeon interpretation (n = 5).

CONCLUSION

Quantification of the ICGFA signal for colorectal surgery is feasible but has so far seen limited academic advancement beyond feasibility.

Indocyanine green fluorescence-guided surgery in the emergency setting: the WSES international consensus position paper

BACKGROUND

Decision-making in emergency settings is inherently complex, requiring surgeons to rapidly evaluate various clinical, diagnostic, and environmental factors. The primary objective is to assess a patient's risk for adverse outcomes while balancing diagnoses, management strategies, and available resources. Recently, indocyanine green (ICG) fluorescence imaging has emerged as a valuable tool to enhance surgical vision, demonstrating proven benefits in elective surgeries.

AIM

This consensus paper provides evidence-based and expert opinion-based recommendations for the standardized use of ICG fluorescence imaging in emergency settings.

METHODS

Using the PICO framework, the consensus coordinator identified key research areas, topics, and questions regarding the implementation of ICG fluorescence-guided surgery in emergencies. A systematic literature review was conducted, and evidence was evaluated using the GRADE criteria. A panel of expert surgeons reviewed and refined statements and recommendations through a Delphi consensus process, culminating in final approval.

RESULTS

ICG fluorescence imaging, including angiography and cholangiography, improves intraoperative decision-making in emergency surgeries, potentially reducing procedure duration, complications, and hospital stays. Optimal use requires careful consideration of dosage and timing due to limited tissue penetration (5-10 mm) and variable performance in patients with significant inflammation, scarring, or obesity. ICG is contraindicated in patients with known allergies to iodine or iodine-based contrast agents. Successful implementation depends on appropriate training, availability of equipment, and careful patient selection.

CONCLUSIONS

Advanced technologies and intraoperative navigation techniques, such as ICG fluorescence-guided surgery, should be prioritized in emergency surgery to improve outcomes. This technology exemplifies precision surgery by enhancing minimally invasive approaches and providing superior real-time evaluation of bowel viability and biliary structures-areas traditionally reliant on the surgeon's visual assessment. Its adoption in emergency settings requires proper training, equipment availability, and standardized protocols. Further research is needed to evaluate cost-effectiveness and expand its applications in urgent surgical procedures.

Risk Factors for Postoperative Complications of Laparoscopic Right Colectomy: A Post Hoc Analysis of the RELARC Trial

BACKGROUND

There is concern regarding the possibility of postoperative complications for laparoscopic right colectomy.

OBJECTIVE

To evaluate the risk factors for postoperative complications for patients undergoing laparoscopic right colectomy.

DESIGN

This was an observational study.

SETTINGS

This was a post hoc analysis of a prospective, multicenter, randomized controlled trial (RELARC trial, NCT02619942).

PATIENTS

Patients included in the modified intention-to-treat analysis in the RELARC trial were all enrolled in this study.

MAIN OUTCOME MEASURES

Risk factors for postoperative complications were identified using univariate and multivariable logistic regression analysis.

RESULTS

Of 995 patients, 206 (20.7%) had postoperative complications. Comorbidity ( p = 0.02; OR: 1.544; 95% CI, 1.077-2.212) and operative time >180 minutes ( p = 0.03; OR: 1.453; 95% CI, 1.032-2.044) were independent risk factors for postoperative complications, whereas female sex ( p = 0.04; OR: 0.704; 95% CI, 0.506-0.980) and extracorporeal anastomosis ( p < 0.001; OR: 0.251; 95% CI, 0.166-0.378) were protective factors. Eighty patients (8.0%) had overall surgical site infection, 53 (5.3%) had incisional surgical site infection, and 33 (3.3%) had organ/space surgical site infection. Side-to-side anastomosis was a risk factor for overall surgical site infection ( p < 0.001; OR: 1.912; 95% CI, 1.118-3.268) and organ/space surgical site infection ( p = 0.005; OR: 3.579; 95% CI, 1.455-8.805). The extracorporeal anastomosis was associated with a reduced risk of overall surgical site infection ( p < 0.001; OR: 0.239; 95% CI, 0.138-0.413), organ/space surgical site infection ( p = 0.002; OR: 0.296; 95% CI, 0.136-0.646), and incisional surgical site infection ( p < 0.001; OR: 0.179; 95% CI, 0.099-0.322). Diabetes ( p = 0.039; OR: 2.090; 95% CI, 1.039-4.205) and conversion to open surgery ( p = 0.013; OR: 5.403; 95% CI, 1.437-20.319) were risk factors for incisional surgical site infection.

LIMITATIONS

Due to the retrospective nature, the key limitation is the lack of prospective documentation and standardization regarding the perioperative management of these patients, such as preoperative optimization, bowel preparation regimens, and antibiotic regimens, which may be confounder factors of complications. All surgeries were performed by experienced surgeons, and the patients enrolled were relatively young, generally healthy, and without obesity. It is unclear whether the results will be generalizable to obese and other populations worldwide.

CONCLUSIONS

Male sex, comorbidity, prolonged operative time, and intracorporeal anastomosis were independent risk factors for postoperative complications of laparoscopic right colectomy. Side-to-side anastomosis was associated with an increased risk of organ/space surgical site infection. Extracorporeal anastomosis could reduce the incidence of overall surgical site infection. Diabetes and conversion to open surgery were associated with an increased risk of incisional surgical site infection. See Video Abstract .

CLINICALTRIALSGOV IDENTIFIER

NCT02619942.

FACTORES DE RIESGO DE COMPLICACIONES POSOPERATORIAS EN COLECTOMA DERECHA LAPAROSCPICA UN ANLISIS POST HOC DEL ENSAYO RELARC

ANTECEDENTES:Existe preocupación con respecto a la posibilidad de complicaciones postoperatorias en colectomía derecha laparoscópica.OBJETIVO:Evaluar los factores de riesgo de complicaciones postoperatorias en pacientes sometidos a colectomía derecha laparoscópica.DISEÑO:Este fue un estudio observacional.ENTORNO CLINICO:Este fue un análisis post hoc de un ensayo controlado aleatorio, multicéntrico y prospectivo: ensayo RELARC (NCT02619942).PACIENTES:Todos los pacientes incluidos en el análisis de intención de tratar modificado en el ensayo RELARC fueron inscritos en este estudio.PRINCIPALES MEDIDAS DE RESULTADO:Los factores de riesgo de complicaciones posoperatorias se identificaron mediante análisis de regresión logística univariante y multivariable.RESULTADOS:De 995 pacientes, 206 (20,7%) tuvieron complicaciones postoperatorias. La comorbilidad ( p = 0,02, OR: 1,544, IC 95%: 1,077-2,212) y el tiempo operatorio >180 min ( p = 0,03, OR: 1,453, IC 95%: 1,032-2,044) fueron factores de riesgo independientes de complicaciones postoperatorias. Mientras que el sexo femenino ( p = 0,04, OR: 0,704, IC 95%: 0,506-0,980) y la anastomosis extracorpórea ( p < 0,001, OR: 0,251, IC 95%: 0,166-0,378) fueron factores protectores. 80 (8,0%) tenían infección general del sitio quirúrgico (ISQ), 53 (5,3%) tenían ISQ incisional y 33 (3,3%) tenían ISQ de órgano/espacio. Anastomosis latero-lateral fue un factor de riesgo para la ISQ general ( p < 0,001, OR: 1,912, IC 95%: 1,118-3,268) y ISQ órgano/espacio ( p = 0,005, OR: 3,579, IC 95%: 1,455-8.805). La anastomosis extracorpórea se asoció con un riesgo reducido de ISQ general ( p < 0,001, OR: 0,239, IC 95%: 0,138-0,413), ISQ órgano/espacio ( p = 0,002, OR: 0,296, IC 95%: 0,136-0,646), e ISQ incisional ( p < 0,001, OR: 0,179, IC 95%: 0,099-0,322). Diabetes ( p = 0,039, OR: 2,090, IC 95%: 1,039-4,205) y la conversión a cirugía abierta ( p = 0,013, OR: 5,403, IC 95%: 1,437-20,319) fueron factores de riesgo para ISQ incisional.LIMITACIONES:Debido a la naturaleza retrospectiva, la limitación clave es la falta de documentación prospectiva y estandarización sobre el manejo perioperatorio de estos pacientes, como la optimización preoperatoria, los regímenes de preparación intestinal y los regímenes de antibióticos, que pueden ser factores de confusión de las complicaciones. Todas las cirugías fueron realizadas por cirujanos experimentados y los pacientes inscritos eran relativamente jóvenes, generalmente sanos y no obesos. No está claro si los resultados serán generalizables a las poblaciones obesas y de otro tipo en todo el mundo.CONCLUSIONES:Sexo masculino, comorbilidad, el tiempo operatorio prolongado y anastomosis intracorpórea fueron factores de riesgo independientes de complicaciones postoperatorias de la colectomía derecha laparoscópica. Anastomosis latero-lateral se asoció con un mayor riesgo de SSI de órgano/espacio. La anastomosis extracorpórea podría reducir la incidencia de ISQ general. La diabetes y la conversión a cirugía abierta se asociaron con un mayor riesgo de ISQ incisional. (Traducción- Dr. Francisco M. Abarca-Rendon ).

ICG-augmented hyperspectral imaging for visualization of intestinal perfusion compared to conventional ICG fluorescence imaging: an experimental study

BACKGROUND

Small bowel malperfusion (SBM) can cause high morbidity and severe surgical consequences. However, there is no standardized objective measuring tool for the quantification of SBM. Indocyanine green (ICG) imaging can be used for visualization, but lacks standardization and objectivity. Hyperspectral imaging (HSI) as a newly emerging technology in medicine might present advantages over conventional ICG fluorescence or in combination with it.

METHODS

HSI baseline data from physiological small bowel, avascular small bowel and small bowel after intravenous application of ICG was recorded in a total number of 54 in-vivo pig models. Visualizations of avascular small bowel after mesotomy were compared between HSI only (1), ICG-augmented HSI (IA-HSI) (2), clinical evaluation through the eyes of the surgeon (3) and conventional ICG imaging (4). The primary research focus was the localization of resection borders as suggested by each of the four methods. Distances between these borders were measured and histological samples were obtained from the regions in between in order to quantify necrotic changes 6 h after mesotomy for every region.

RESULTS

StO2 images (1) were capable of visualizing areas of physiological perfusion and areas of clearly impaired perfusion. However, exact borders where physiological perfusion started to decrease could not be clearly identified. Instead, IA-HSI (2) suggested a sharp-resection line where StO2 values started to decrease. Clinical evaluation (3) suggested a resection line 23 mm (±7 mm) and conventional ICG imaging (4) even suggested a resection line 53 mm (±13 mm) closer towards the malperfused region. Histopathological evaluation of the region that was sufficiently perfused only according to conventional ICG (R3) already revealed a significant increase in pre-necrotic changes in 27% (±9%) of surface area. Therefore, conventional ICG seems less sensitive than IA-HSI with regards to detection of insufficient tissue perfusion.

CONCLUSIONS

In this experimental animal study, IA-HSI (2) was superior for the visualization of segmental SBM compared to conventional HSI imaging (1), clinical evaluation (3) or conventional ICG imaging (4) regarding histopathological safety. ICG application caused visual artifacts in the StO2 values of the HSI camera as values significantly increase. This is caused by optical properties of systemic ICG and does not resemble a true increase in oxygenation levels. However, this empirical finding can be used to visualize segmental SBM utilizing ICG as contrast agent in an approach for IA-HSI. Clinical applicability and relevance will have to be explored in clinical trials.

LEVEL OF EVIDENCE

Not applicable. Translational animal science. Original article.

Fluorescence-guided colorectal surgery: applications, clinical results, and protocols

In recent years, the rise of minimally invasive surgery has driven the development of surgical devices. Indocyanine green (ICG) fluorescence imaging is receiving increased attention in colorectal surgery for improved intraoperative visualization and decision-making. ICG, approved by the U.S. Food and Drug Administration in 1959, rapidly binds to plasma proteins and is primarily intravascular. ICG absorption of near-infrared light (750-800 nm) and emission as fluorescence (830 nm) when bound to tissue proteins enhances deep tissue visualization. Applications include assessing anastomotic perfusion, identifying sentinel lymph nodes, and detecting colorectal cancer metastasis. However, standardized protocols and research on clinical outcomes remain limited. This study explores ICG's role, advantages, disadvantages, and potential clinical impact in colorectal surgery.

Indocyanine Green (ICG) and Colorectal Surgery: A Literature Review on Qualitative and Quantitative Methods of Usage

Background: Due to its many benefits, indocyanine green (ICG) has gained progressive popularity in operating rooms (ORs) globally. This literature review examines its qualitative and quantitative usage in surgical treatment. Method: Relevant terms were searched in five international databases (1. Pubmed, 2. Sciencedirect, 3. Scopus, 4. Oxfordjournals, 5. Reaxys) for a comprehensive literature review. The main benefits of using ICG in colorectal surgery are: intraoperative fluorescence angiography; fluorescence-guided lymph node involvement detection and the sentinel technique; the fluorescent emphasis of a minute liver tumour, counting just 200 tumour cells; facilitation of fistula diagnosis; and tumour tattooing. This methodology can also be used with quantitative characteristics such as maximum intensity, relative maximum intensity, and in-flow parameters such as time-to-peak, slope, and t1/2max. This article concludes that fluorescence surgery with ICG and near-infrared (NIR) light is a relatively new technology that improves anatomical and functional information, allowing more comprehensive and safer tumour removal and the preservation of important structures.

The Safe Values of Quantitative Perfusion Parameters of ICG Angiography Based on Tissue Oxygenation of Hyperspectral Imaging for Laparoscopic Colorectal Surgery: A Prospective Observational Study

BACKGROUND

Safe values for quantitative perfusion parameters of indocyanine green (ICG) angiography have not been fully defined, and interpretation remains at the surgeon's discretion. This prospective observational study aimed to establish the safe values for the quantitative perfusion parameters by comparing tissue oxygenation levels from HSI images in laparoscopic colorectal surgery.

METHODS

ICG angiography was performed using a laparoscopic near-infrared (NIR) camera system with ICG diluted in 10 mL of distilled water. For quantitative perfusion parameters, the changes in fluorescence intensity with perfusion times were analyzed to plot a time-fluorescence intensity graph. To assess real-time tissue oxygen saturation (StO2) in the colon, the TIVITA® Tissue System was utilized for hyperspectral imaging (HSI) acquisition. The StO2 levels were compared with the quantitative perfusion parameters derived from ICG angiography at corresponding points to define the safe range of ICG parameters reflecting good tissue oxygenation.

RESULTS

In the regression analysis, T1/2MAX, TMAX, slope, and NIR perfusion index were correlated with tissue oxygen saturation. Using this regression model, the cutoff values of quantitative perfusion parameters were calculated as T1/2MAX ≤ 10 s, TMAX ≤ 30 s, slope ≥ 5, and NIR perfusion index ≥50, which best reflected colon StO2 higher than 60%. Diagnostic values were analyzed to predict colon StO2 of 60% or more, and the ICG perfusion parameters T1/2MAX, TMAX, and perfusion TR showed high sensitivity values of 97% or more, indicating their ability to correctly identify cases with acceptable StO2.

CONCLUSION

The safe values for quantitative perfusion parameters derived from ICG angiography were T1/2MAX ≤ 10 s and TMAX ≤ 30 s, which were associated with colon tissue oxygenation levels higher than 60% in the laparoscopic colorectal surgery.

Quantification of bowel ischaemia using real-time multispectral Single Snapshot Imaging of Optical Properties (SSOP)

BACKGROUND

Single snapshot imaging of optical properties (SSOP) is a relatively new non-invasive, real-time, contrast-free optical imaging technology, which allows for the real-time quantitative assessment of physiological properties, including tissue oxygenation (StO2). This study evaluates the accuracy of multispectral SSOP in quantifying bowel ischaemia in a preclinical experimental model.

METHODS

In six pigs, an ischaemic bowel segment was created by dividing the arcade branches. Five regions of interest (ROIs) were identified on the bowel loop, as follows: ROI 1: central ischaemic; ROI 2: left marginal; ROI 3: left vascularised; ROI 4: right marginal; and ROI 5: right vascularised. The Trident imaging system, specifically developed for real-time tissue oxygenation imaging using SSOP, was used to image before (T0) and after ischaemia induction. Capillary and systemic lactates were measured at each time point (T0, T15, T30, T45, T60), as well as StO2 values acquired by means of SSOP (SSOP-StO2).

RESULTS

The mean value of SSOP-StO2 in ROI 1 was 30.08 ± 6.963 and was significantly lower when compared to marginal ROIs (ROI 2 + ROI 4: 45.67 ± 10.02 p =  < 0.0001), and to vascularised ROIs (ROI 3 + ROI 5: 48.08 ± 7.083 p =  < 0.0001). SSOP-StO2 was significantly correlated with normalised lactates r = - 0.5892 p < 0.0001 and with histology r =- 0.6251 p = 0.0002.

CONCLUSION

Multispectral SSOP allows for a contrast-free accurate assessment of small bowel perfusion identifying physiological tissue oxygenation as confirmed with perfusion biomarkers.

A Narrative Review of the Usefulness of Indocyanine Green Fluorescence Angiography for Perfusion Assessment in Colorectal Surgery

Anastomotic leakage is one of the most dreaded complications of colorectal surgery and is strongly associated with tissue perfusion. Indocyanine green fluorescence angiography (ICG-FA) using indocyanine green and near-infrared systems is an innovative technique that allows the visualization of anastomotic perfusion. Based on this information on tissue perfusion status, surgeons will be able to clearly identify colorectal segments with good blood flow for safer colorectal anastomosis. The results of several clinical trials indicate that ICG-FA may reduce the risk of AL in colorectal resection; however, the level of evidence is not high, as several other studies have failed to demonstrate a reduction in the risk of AL. Several large-scale RCTs are currently underway, and their results will determine whether ICG-FA is, indeed, useful. The major limitation of the current ICG-FA evaluation method, however, is that it is subjective and based on visual assessment by the surgeon. To complement this, the utility of objective evaluation methods for fluorescence using quantitative parameters is being investigated. Promising results have been reported from several clinical trials, but all trials are preliminary owing to their small sample size and lack of standardized protocols for quantitative evaluation. Therefore, appropriately standardized, high-quality, large-scale studies are warranted.