Predicting the long-term viability of ischaemic bowel during surgery is challenging. The aim was to determine whether intraoperative near-infrared angiography (NIR-AG) of ischaemic bowel might provide metrics that were predictive of long-term outcome.

NIR-AG using indocyanine green was performed on 24 pigs before, and after inducing bowel ischaemia to determine the feasibility of NIR-AG for detecting compromised perfusion. Contrast-to-background ratio (CBR) over time was measured in regions of interest throughout the bowel, and various metrics of the CBR-time curve were developed. Sixty rat small bowels, with or without strangulation, were imaged during surgery and on day 3 after operation. CBR metrics and clinical findings were assessed quantitatively for their ability to predict animal survival, histological grade of ischaemic injury and visible necrosis on day 3.

In ischaemic pig small bowel, various qualitative and quantitative CBR metrics appeared to correlate with bowel injury as a function of distance from normal bowel. In rats, intraoperative clinical assessment showed high specificity but low sensitivity for predicting outcome on day 3 after operation. Qualitative patterns of the CBR-time curve, such as absence of an arterial inflow peak and presence of a NIR filling defect, resulted in better prediction of survival (90 per cent), histological grade (85 per cent) and visible necrosis on day 3 (92 per cent).

Survival of ischaemic bowel was predicted by intraoperative NIR-AG with greater accuracy than clinical evaluation alone.

Amputation may be the most appropriate therapy for an ischemic or infected limb, but the level at which to amputate is often difficult to determine. Selecting the appropriate level is crucial when performing an amputation. The goals of surgery are to maintain maximal limb length and ensure successful healing. When more of the foot and limb can be preserved, the chances for rehabilitation are improved. This article reviews how to determine the most appropriate level of amputation.

Intraoperative assessment of intestinal viability following release of strangulation remains difficult. The aim of this study was to establish clinical standards for the evaluation of intestinal viability by charge-coupled device (CCD) microscopy.

A rat ileus model with strangulation for between 15 and 120 min was used. The images obtained by CCD microscopy were used to calculate maximum velocity (V (max)) ratio (ratio of V (max) of blood cell transition in the experimental segment to that in the reference segment) and S ratio (the ratio of S-the effective area of the vascular bed against the total area of the vascular bed-in the experimental segment to that in the reference segment). Rats were divided into group 1, comprising animals that survived for 7 days or more, and group 2, which consisted of animals that died within 4 days.

V (max) ratio and S ratio in group 1 were both significantly higher than those in group 2 (P < 0.01). No death occurred at a V (max) ratio of 0.76 or higher and an S ratio of 0.61 or more, while there were no survivors with a V (max) ratio of 0.54 or less and an S ratio of 0.51 or less.

V (max) ratio and S ratio could be used as indices for evaluation of intestinal viability.

To detect reperfused ischemia of the rat intestine, T2-weighted spin-echo images were acquired, followed by T1-weighted images before and after administration of polylysine-Gd-DTPA or Gd-DTPA. Before administration of the contrast agent, the reperfused intestine was hyperintense on T2-weighted images, and to a lesser extent on T1-weighted images. After administration of polylysine-Gd-DTPA, the reperfused intestine enhanced more than the normal one, giving a significantly better contrast-to-noise (CNR) ratio than on unenhanced images. Gd-DTPA induced the same enhancement of the reperfused and the normal intestine and the CNR was lower than on unenhanced T2-weighted images. Reperfused intestinal ischemia could thus be better detected on polylysine-Gd-DTPA-enhanced MR images than on unenhanced images or on Gd-DTPA-enhanced images.

Acute mesenteric ischemia represents one to two percent of all gastrointestinal illnesses. There are three possible causes of acute arterial mesenteric ischemia: embolism, thrombosis, and nonocclusive mesenteric insufficiency. The key to early diagnosis is a high index of suspicion. The classic clinical picture of obvious cardiac disease, sudden onset of severe abdominal pain and gastrointestinal emptying, is not always present. Serum markers and plain films are often nondiagnostic but may suggest acute arterial mesenteric ischemia. Angiography establishes the diagnosis and allows for planning of aortomesenteric bypass, if indicated. Papaverine is immediately instilled to decrease splanchnic vasoconstriction. Embolic and thrombotic disease is treated by laparotomy with re-establishment of visceral perfusion. Only after blood flow is restored is nonviable bowel resected. Clinical methods of assessing intestinal viability include Doppler scanning, intravascular dyes, and tissue oximetry. The decision to perform a second-look laparotomy is made prior to closure of the abdomen. Pharmacologic treatment is the mainstay of nonocclusive ischemia. Surgery is reserved for clinical deterioration. Survival is dependent on the cause and extent of occlusion as well as the rapidity of diagnosis and therapy. Bowel necrosis results in mortality rates between 80 percent and 95 percent.

Small bowel procedures such as placement of feeding jejunostomy, diagnosis of small bowel ischaemia and obstruction, bowel resection and lysis of adhesions can all be performed laparoscopically. Diagnostic laparoscopy can be performed with low complication rates, and can help avoid unnecessary laparotomy. The open method of trocar placement is preferred in patients with adhesions or distended bowel due to obstruction or ileus. Feeding jejunostomy can be placed by laparoscopically assisted methods, pulling the jejunum out or completely laparoscopically. The latter requires fixation of the jejunum to the abdominal wall by transabdominal sutures or T-fasteners. The T-fastener technique for feeding jejunostomy is simple to perform, safe and effective. Small bowel ischaemia can be difficult to diagnose laparoscopically. Fluorescein and ultrasound Doppler examination of the small bowel may be as useful as in laparotomy, but there is little clinical experience with these techniques. Laparoscopically assisted small bowel resection involves intraperitoneal division of the mesenteric vessels and exteriorization of the small bowel through a small abdominal incision, followed by resection and anastomosis. The causes of small bowel obstruction can be diagnosed laparoscopically, and adhesions can be lysed under laparoscopic guidance. The laparoscopic approach is replacing laparotomy for many small bowel procedures. Improvements in instruments and experience in laparoscopic procedures will continue to make these procedures easier and safer to perform.

Viability of ischemic bowel was assessed in 30 dogs after mesenteric arterial ligation in a 40-cm length of ileum. Viability was evaluated using two gross features, color and peristalsis, and four objective methods including bowel wall surface oximetry (pO2), Doppler ultrasound, quantitative fluorescein fluorimetry, and myoelectric activity measured by a strain gauge probe. Each parameter was measured at 2-cm intervals within the 40-cm ischemic segment before resection and anastomosis was performed. There were seven fatal anastomotic leaks, all due to further bowel necrosis. Survival did not correlate with bowel color, presence of peristalsis, bowel wall pO2 Doppler ultrasound, or the myoelectric parameters. However, fluorescein fluorimetry was predictive of long-term viability. These results suggest that quantitative fluorescein fluorimetry may be a useful adjunct in intraoperative bowel viability assessment.

Acute intestinal ischemia and infarction remain serious clinical problems despite early operative intervention. Accurate intraoperative assessment of intestinal viability is essential in determining the limits of resection in patients with intestinal infarction. Clinical features of bowel viability such as color and peristalsis do not correlate uniformly with bowel survival, and as a result, several techniques have been developed to assess intestinal blood flow at the time of operation. The requirements of an ideal viability test are: 1. The technique must have ready availability, preferably in every operating theater dealing with abdominal emergencies. 2. The necessary equipment must not be cumbersome or require specialized personnel. 3. The method must be accurate with a minimum of false-negative results and, more importantly, few false positives. A false-negative results leaves in situ nonviable bowel, which may lead to early perforation and late stricturing. This situation may be recoverable with further surgical intervention, however. On the other hand, a false-positive assessment of bowel viability results in the resection of potentially recoverable intestine, which is lost forever and may represent a vital difference for morbidity-mortality and long-term nutrition. 4. The technique must be objective and be reproducible. 5. The method must be cost effective. To date, only two tests have found widespread acceptance and clinical applicability: fluorescein assessment and Doppler studies either with ultrasound or as refined in laser velocimetry. Although other techniques may be of some value today or in the future, the most practical approach would appear to be to use fluorescein assessment under a modified Wood's lamp as the initial method of evaluating intestinal viability and either Doppler ultrasound or perfusion fluorometry for any areas of particularly doubtful viability.

Despite the plethora of technologic advances, the most common technique for diagnosing burn depth remains the clinical assessment of an experienced burn surgeon. It is clear that this assessment is accurate for very deep and very shallow burns. But since clinical judgment is not precise in telling whether a dermal burn will heal in 3 weeks, efforts to develop a burn depth indicator are certainly warranted to accurately determine which dermal burns to excise and graft. This review summarizes the considerable literature in which a variety of techniques to determine burn depth have been used.

Since 1988 there have been 15 reported cases of late, spontaneously ruptured intestinal cystoplasties at bowel sites remote from the anastomosis. Ischemic necrosis has been suggested as a possible etiology. We examined this hypothesis by quantifying the uptake of intravascular fluorescein in the augmented bowel of adult mongrel canines. There was a statistically significant decrease in fluorescein uptake at high intravesical pressures, which appeared to be most pronounced at the antimesenteric border. This laboratory study supports a recent clinical report of histological changes pathognomonic for chronic ischemia in the augmented bowel of patients with spontaneous rupture.

To elucidate parameters diagnostic of chronic ischemia, the fluorescence of skin on the foot, leg, arm, and forehead of six chronically ischemic patients and six normal subjects injected with fluorescein was measured serially using a surface-measurement fluorometer (dermofluorometer). Simultaneously collected plasma samples were assayed spectrofluorometrically for unmetabolized fluorescein. The time courses of plasma fluorescein content and dermofluorometer readings were jointly analyzed by combining a standard pharmacokinetic model, a model predicting skin site from plasma concentrations of fluorescein, and a model predicting the dermofluorometer response to those skin concentrations. Fluorescein plasma clearance (0.22 +/- 0.06 versus 0.46 +/- 0.20 L/h/kg) in ischemic patients was only half, and half-life was double (2.4 +/- 1.0 versus 1.3 +/- 0.3 h) those in normal subjects, with volume of distribution (Vdss = 0.46 L/kg) being similar. Despite the ischemia diagnosis for all patients involving claudication of the lower extremities, patients could be distinguished statistically from normal subjects on the basis of fluorescence readings taken on the arm, but not those using the foot or leg. The rate constant describing flux of fluorescein from the arm skin site in patients was only half that in normal subjects, and the peak reading on the arm occurred at 42 +/- 14 min after fluorescein injection in patients, but at only 15 +/- 6 min in normal subjects. Lack of discrimination between subject groups via leg and foot readings may be due to several physiologic and/or experimental factors, including the need to take skin surface readings much earlier than previously recognized.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium fluorescein is an in vivo blood perfusion indicator for soft tissue. When fluorescein dye is introduced into the blood, it distributes throughout the vasculature and the extravascular space. Incident light from an external source causes the dye to fluoresce, the level of which is monitored by a photodetector placed over the tissue. In this study, theoretical analysis incorporating a multicompartmental model for dye distribution is applied to describe the relationship among perfusion, dye kinetics, and fluorescence readings. Errors in calculating perfusion from fluorescence are related to dye concentrations and to measurement errors. These error sources are minimized by selecting the measurement time. The alternatives of measurement during wash-in or during wash-out of dye are compared, as well as the alternatives of introducing dye by bolus injection or by constant infusion. Compensation of wash-in measurements for differences in skin pigmentation is accomplished by the matching of skin optical properties between incident and fluorescing wavelengths. A laboratory study at 80 measurement sites (from ten graded perfusion canine flaps) demonstrated a correlation of wash-in and wash-out perfusion data ranging from 0.88 to 0.96 at typical levels of fluorescein in blood. Since wash-in can be completed in a matter of a few minutes, this is likely to be preferable in the clinical setting to wash-out which can take much longer to complete.

Leakage and stenosis are serious complications of gastrointestinal anastomotic surgery that may, in part, be related to local ischemia. The ability to accurately quantitate the degree of gastrointestinal anastomotic ischemia remains a challenging clinical problem. The purpose of this study was to: 1) develop a model of colorectal anastomotic stenosis following local ischemia; 2) compare the accuracy of laser Doppler velocimetry and intramural colonic pH in quantitating critical levels of intestinal anastomotic ischemia; and 3) compare the anastomotic healing process using either a standard two-layer Czerny-Lembert handsewn or EEATM stapled anastomotic technique under ischemic conditions. The studies reported here were performed in two phases. Phase I was the pilot study in which the authors developed a model of colorectal anastomotic ischemia and defined critical levels of ischemia using laser Doppler velocimetry and intramural pH (less than or equal to 200 mV; less than or equal to 7.0, respectively). These parameters were then tested prospectively in Phase II, assessing the effects of anastomotic ischemia on animals kept alive for 5, 11, 21, and 60 days after surgery. Overall there was a 70 percent incidence of anastomotic healing complications in the Phase II trial with laser Doppler velocimetry correctly predicting anastomotic outcome in 70 percent of cases and tissue pH in 93 percent of cases. The results indicate that, although laser Doppler velocimetry and intramural pH measurements provide safe, easy techniques for assessing the effects of ischemia on the colorectal anastomosis, measurement of intramural pH provides an optimal quantitative method for predicting subsequent anastomotic outcome and tissue viability.

Arteriovenous (ischaemic strangulating obstruction, ISO) and venous obstructions (haemorrhagic strangulating obstruction, HSO) were created for 70 min in the small intestine of eight anaesthetised horses, and ISO was created in four horses for 2 h and four horses for 3 h at the sternal and diaphragmatic flexures of the large colon. Five minutes following release of the occlusions, sodium fluorescein 20 per cent (0.5 mg/kg bodyweight intravenously) was administered. Serial quantitative measurements of serosal surface fluorescence of the injured segments and a control segment were made at 2, 10, 15, 20 and 30 mins using a fibreoptic perfusion fluorometer. Significant differences in fluorescence were seen in small intestine segments between HSO vs control, ISO vs HSO, but not ISO vs control segments. In the large colon, significant differences were seen between the fluorescence in the ischaemic 3 h ventral colon and control segments, and a trend for difference in fluorescence between the 2 and 3 h ischaemic segments. Differences in fluorescence between 2 vs 3 h dorsal colon segments and 2 or 3 h dorsal colon vs control segments were not significant.

The present study employed fiberoptic fluorometry, a noninvasive means of documenting delivery and removal of fluorescein dye, to evaluate the local circulatory changes elicited by topical application of DHV-PGE2 ME, an investigational PGE2 analog. On Day 1, inactive vehicle was applied to a 5 X 4 cm study site on each thigh of healthy volunteer subjects (n = 12). Symmetrical perfusion was confirmed by similar determinations of dye delivery and removal at each site. On Day 2, DHV-PGE2 ME, 30 or 120 micrograms, was applied to one site while inactive vehicle again was applied to the other. After administration of 120 micrograms in a petrolatum vehicle, fluorometry detected a pronounced increase in nutritive perfusion. There was significant acceleration of dye delivery and removal (p less than 0.05 by ANOVA). Less pronounced changes were noted after the lower dose of DHV-PGE2 ME and when the drug was applied in a triethyl citrate vehicle. The local circulatory changes were not accompanied by systemic effects; there were no changes in vital signs or in fluorometric indices at remote sites.

Ischiopagus tripus conjoined twins were recently encountered. All organ systems were thoroughly evaluated using radiographic, angiographic, radionuclide, and CT imaging techniques. None of these studies were capable of accurately assessing the vascular territories of the skin at the level of the pelvis, the most critical area in terms of separation. Qualitative visual assessment of tissue fluorescein delivery under ultraviolet illumination is subject to subjective errors. Perfusion fluorometry is a recently developed technique whereby tissue fluorescence can be quantitated over time in very small amounts, even with repeated injections. In these conjoined twins, using sequential fluorescein injections in each twin, it was possible to accurately determine which portions of the pelvis and the shared leg belonged to which twin and exactly where the skin incisions should be made. Additionally, during operation it was possible to accurately predict the viability of skin flaps used for closure. Both twins survived. This is the first time it has been possible to accurately assess vascular territories of the skin in a complicated form of conjoined twinning. The technique is also useful in the evaluation of flow patterns in various other parts of the body.

Clinical evaluation and qualitative (visual) and quantitative (fluorometric) fluorescence for predicting intestinal viability were compared in an animal model of temporary arterial occlusion with early revascularization. Quantitative fluorescence was determined with a perfusion fluorometer after an intravenous bolus of fluorescein. Qualitative fluorescence was determined by examination under a Wood's lamp in a darkened room. The effectiveness of each diagnostic technique in determining nonviability was expressed in terms of sensitivity, specificity, and accuracy. All three methods had 100 percent specificity; only bowel deemed nonviable proved to be so. Quantitative fluorescence also had a 100 percent sensitivity, but clinical evaluation and qualitative fluorescence had only a 33 and 11 percent sensitivity, respectively (some segments of bowel that were ultimately nonviable were not correctly predicted to be so). The inaccuracy of qualitative fluorescence was due to the fact that ischemic intestine with a hyperfluorescent pattern often progressed to necrosis. Fluorometric quantitation identified those hyperfluorescent segments that were viable. This study suggests that visual fluorescence is not reliable in assessing intestinal viability after early revascularization after arterial occlusion, but quantitative fluorometric fluorescence is reliable in almost all instances.

The fiberoptic fluorometer permits quantitative measurement of fluorescence after intravenous administration of fluorescein. Accurate assessment of tissue fluorescence can be made at any time after the injection, and both uptake and elimination of fluorescein can be followed. The instrument provides instantaneous digital readout of the fluorescence measured in dye fluorescence (DF) units and an index predictive of viability called the dye fluorescence index (DFI). The unit is portable, can be sterilized for operating room use, and can be operated by paramedical personnel with ease. We have used the instrument extensively in clinical and laboratory investigations, where it has been highly reliable in predicting survival and necrosis of a wide variety of flaps. Little or no operating time is added, and serial, low-dose fluorescein injections may be used to monitor a flap in the recovery room or at the bedside in the early postoperative period.