A self-matched leaky-wave antenna for ultrahigh-field magnetic resonance imaging with low specific absorption rate.

The technology of magnetic resonance imaging is developing towards higher magnetic fields to improve resolution and contrast. However, whole-body imaging at 7 T or even higher flux densities remains challenging due to wave interference, tissue inhomogeneities, and high RF power deposition. Nowadays, proper RF excitation of a human body in prostate and cardiac MRI is only possible to achieve by using phased arrays of antennas attached to the body (so-called surface coils). Due to safety concerns, the design of such coils aims at minimization of the local specific absorption rate (SAR), keeping the highest possible RF signal in the region of interest. Most previously demonstrated approaches were based on resonant structures such as e.g. dipoles, capacitively-loaded loops, TEM-line sections. In this study, we show that there is a better compromise between the transmit signal [Formula: see text] and the local SAR using non-resonant surface coils generating a low electric field in the proximity of their conductors. With this aim, we propose and experimentally demonstrate a leaky-wave antenna implemented as a periodically-slotted microstrip transmission line. Due to its non-resonant radiation, it induces only slightly over half the peak local SAR compared to a state-of-the-art dipole antenna but has the same transmit efficiency in prostate imaging at 7 T. Unlike other antennas for MRI, the leaky-wave antenna does not require to be tuned and matched when placed on a body, which makes it easy-to-use in prostate imaging at 7 T MRI.

The Swiss Canine Cancer Registry: a retrospective study on the occurrence of tumours in dogs in Switzerland from 1955 to 2008.

Diagnostic records are a key feature of any cancer epidemiology, prevention or control strategy for man and animals. Therefore, the information stored in human and animal cancer registries is essential for undertaking comparative epidemiological, pathogenic and therapeutic research. This study presents the Swiss Canine Cancer Registry, containing case data compiled between 1955 and 2008. The data consist of pathology diagnostic records issued by three veterinary diagnostic laboratories in Switzerland. The tumours were classified according to the guidelines of the International Classification of Oncology for Humans on the basis of tumour type, malignancy and body location. The dogs were classified according to breed, age, sex, neuter status and place of residence. The diagnostic data were correlated with data on the Swiss general dog population and the incidence of cancer in dogs was thus investigated. A total of 67,943 tumours were diagnosed in 121,963 dogs and 47.07% of these were malignant. The most common tumour location was the skin (37.05%), followed by mammary glands (23.55%) and soft tissue (13.66%). The most common tumour diagnoses were epithelial (38.45%), mesenchymal (35.10%) and lymphoid tumours (13.23%). The results are compared with data in other canine registries and similarities in tumour distribution and incidence are noted. It is hoped that this study will mark the beginning of continuous registration of dog tumours in Switzerland, which, in turn, will serve as a reference for research in the fields of animal and human oncology.

[Dog population and dog breeds in Switzerland from 1955 to 2008]. / Hundepopulation und Hunderassen in der Schweiz von 1955 bis 2008.

Aim of this study is to present a survey of the dog population and breed distribution in Switzerland from 1955 to 2008 as basis to realize a population based canine cancer register for Switzerland. The number of dogs rose from 309'000 in 1955 to approximately 500'000 in 2008 correlating with a parallel increase of human population. The ratio of dogs per 100 inhabitants remains stable. This ratio is lower in German speaking compared to French or Italian speaking Cantons. The variety and popularity of breeds changed from 1955 to 2008, "winners" are Labrador and Golden Retrievers, Yorkshire and Jack Russel Terriers. Less popular breeds over the years are German Sheherd dogs and Poodles.

Relevance of the light line in planar photonic crystal waveguides with weak vertical confinement.

The concept of the so-called light line is a useful tool to distinguish between guided and non-guided modes in dielectric slab waveguides. Also for more complicated structures with 2D mode confinement, the light lines can often be used to divide a dispersion diagram into a region of a non-guided continuum of modes, a region of discrete guided modes and a forbidden region, where no propagating modes can exist. However, whether or not the light line is a concept of practical relevance depends on the geometry of the structure. This fact is sometimes ignored. For instance, in the literature on photonic crystal waveguides, it is often argued that substrate-type photonic crystal waveguides with a weak vertical confinement are inherently lossy, since the entire bandgap including the line defect modes is typically located above the light line of the substrate. The purpose of this article is to illustrate that this argument is inaccurate and to provide guidelines on how an improved light line concept can be constructed.

Morphology and hemodynamics during vascular regeneration in critically ischemic murine skin studied by intravital microscopy techniques.

BACKGROUND: With the understanding of angiogenesis and arteriogenesis, new theories about the orchestration of these processes have emerged. The aim of this study was to develop an in vivo model that enables visualization of vascular regenerating mechanisms by intravital microscopy techniques in collateral arteriolar flap vascularity. METHODS: A dorsal skin flap (15 × 30 mm) was created in mice and fixed into a skinfold chamber to allow for assessment of morphology and microhemodynamics by intravital fluorescence microscopy (IVFM). Laser scanning confocal microscopy (LSCM) was utilized for three-dimensional reconstruction of the microvascular architecture. RESULTS: Flap tpO(2) was 5.3 ± 0.9 versus 30.5 ± 1.2 mm Hg in controls (p < 0.01). The collateral arterioles in the flap tissue were dilated (29.4 ± 5.3 µm; p < 0.01 vs. controls) and lengthened in a tortuous manner (tortuosity index 1.00 on day 1 vs. 1.35± 0.05 on day 12; p < 0.01). Functional capillary density was increased from 121.00 ± 25 to 170 ± 30 cm/cm(2) (day 12; p < 0.01) as a result of angiogenesis. Morphological evidence of angiogenesis on capillary level and vascular remodeling on arteriolar level could be demonstrated by IVFM and LSCM. CONCLUSIONS: Present intravital microscopy techniques offer unique opportunities to study structural changes and hemodynamic effects of vascular regeneration in this extended axial pattern flap model.

An old dream revitalised: preconditioning strategies to protect surgical flaps from critical ischaemia and ischaemia-reperfusion injury.

The prevention of ischaemia and the adequate restitution of blood flow to ischaemic tissue are pivotal to halt the progression of cellular injury associated with decreased oxygen and nutrient supply. Accordingly, the search for novel strategies which aim at preventing ischaemia-reperfusion-induced tissue damage is still of major interest in flap surgery. Preconditioning represents an elegant approach to render the tissue more resistant against deleterious ischaemic insults. For many decades, 'surgical delay' has been the standard method of tissue preconditioning. During the last 10 years, ischaemic preconditioning was added to the repertoire of plastic surgeons to protect flaps from ischaemic necrosis. The invasiveness and expenditure of time of these procedures, however, have always been major drawbacks, hindering a wide distribution in clinical practice. Consequently, the motivation has all along been to further refine and simplify protective strategies. Recent experimental studies have now shown that efficient protection from ischaemic necrosis can also be achieved by remote preconditioning or pretreatment with chemical agents and growth factors, which mimic the action of surgical delay and ischaemic preconditioning. In addition, the local application of unspecific stressors, including both heating and cooling, have been shown to effectively improve flap microcirculation and, thus, tissue survival. In view of successful translational research, it is now time that the efficacy of these novel preconditioning procedures is proven in prospective randomised clinical trials.

The influence of local and systemic preconditioning on oxygenation, metabolism and survival in critically ischaemic skin flaps in pigs.

Stress proteins represent a group of highly conserved intracellular proteins that provide adaptation against cellular stress. The present study aims to elucidate the stress protein-mediated effects of local hyperthermia and systemic administration of monophosphoryl lipid A (MPL) on oxygenation, metabolism and survival in bilateral porcine random pattern buttock flaps. Preconditioning was achieved 24h prior to surgery by applying a heating blanket on the operative site (n = 5), by intravenous administration of MPL at a dosage of 35 microg/kg body weight (n = 5) or by combining the two (n = 5). The flaps were monitored with laser Doppler flowmetry, polarographic microprobes and microdialysis until 5h postoperatively. Semiquantitative immunohistochemistry was performed for heat shock protein 70 (HSP70), heat shock protein 32 (also termed haem oxygenase-1, HO-1), and inducible nitrc oxide synthase (iNOS). The administration of MPL increased the impaired microcirculatory blood flow in the proximal part of the flap and partial oxygen tension in the the distal part by approximately 100% each (both P<0.05), whereas both variables remained virtually unaffected by local heat preconditioning. Lactate/pyruvate (L/P) ratio and glycerol concentration (representing cell membrane disintegration) in the distal part of the flap gradually increased to values of approximately 500 mmol/l and approximately 350 micromol/l, respectively (both P<0.01), which was substantially attenuated by heat application (P<0.01 for L/P ratio and P<0.05 for glycerol) and combined preconditioning (P<0.01 for both variables), whereas the effect of MPL was less marked (not significant). Flap survival was increased from 56% (untreated animals) to 65% after MPL (not significant), 71% after heat application (P<0.05) and 78% after both methods of preconditioning (P<0.01). iNOS and HO-1 were upregulated after each method of preconditioning (P<0.05), whereas augmented HSP70 staining was only observed after heat application (P<0.05). We conclude that local hyperthermia is more effective in preventing flap necrosis than systemic MPL administration because of enhancing the cellular tolerance to hypoxic stress, which is possibly mediated by HSP70, whereas some benefit may be obtained with MPL due to iNOS and HO-1-mediated improvement in tissue oxygenation.

Mode-locked laser diode with an ultrafast integrated uni-traveling carrier saturable absorber.

A novel two-section integrated mode-locked laser diode (MLLD) with a separate ultrafast uni-traveling carrier (UTC) saturable absorber section and semiconductor optical amplifier gain section is demonstrated. The UTC absorber is composed of a thin p-InGaAsP absorbing layer and an intrinsic InGaAsP collecting layer. By confining the photoexcitation process to the thin highly doped absorbing layer, the diffusion-limited hole extraction process is greatly enhanced. The investigated MLLD produces 600 fs uncompressed optical pulses at a 42 GHz repetition rate.

Optical phase locked loop for transparent inter-satellite communications.

A novel type of optical phase locked loop (OPLL), optimized for homodyne inter-satellite communication, is presented. The loop employs a conventional 180? 3 dB optical hybrid and an AC-coupled balanced front end. No residual carrier transmission is required for phase locking. The loop accepts analog as well as digital data and various modulation formats. The only requirement to the transmitted user signal is a constant envelope. Phase error extraction occurs through applying a small sinusoidal local oscillator (LO) phase disturbance, while measuring its impact on the power of the baseband output signal. First experimental results indicate a receiver sensitivity of 36 photons/bit (-55.7 dBm) for a BER of 10 ;-9, when transmitting a PRBS-31 signal at a data rate of 400 Mbit/s. The system setup employs diode-pumped Nd:YAG lasers at a wavelength of 1.06 mum.

Evolution of ischemic tissue injury in a random pattern flap: a new mouse model using intravital microscopy.

BACKGROUND: Dissection of random pattern flaps may cause microcirculatory dysfunction and ischemia, which jeopardize wound healing due to impaired tissue viability. The aim of this study was to develop an in vivo model that enables continuous monitoring of the interplay between microcirculatory dysfunction, ischemia, and tissue injury by intravital microscopy. MATERIALS AND METHODS: A laterally based random pattern skin flap (15 x 11 mm) including the panniculus carnosus was raised in the back of mice and fixed into a dorsal skinfold chamber (n = 10). Arteriolar blood flow, functional capillary density, number of apoptotic cells, and area of tissue necrosis were analyzed by intravital fluorescence microscopy in the proximal, middle, and distal part of the flap at day 1, 3, 5, and 7 after surgery. Chamber preparations without flap harvesting served as controls (n = 6). RESULTS: At day 1, the distal part of the flap showed a decreased arteriolar blood flow (266 +/- 124 pl/s versus controls: 1418 +/- 351 pl/s; P < 0.05), which resulted in severe alteration of functional capillary density (43 +/- 11 cm/cm2 versus 270 +/- 7 cm/cm2; P < 0.001). The impaired microcirculation was associated with apoptotic cell death (277 +/- 50 cells/mm2 versus 50 +/- 5 cells/mm2; P < 0.05). Microcirculatory dysfunction persisted over 7 days, and, finally, resulted in 49 +/- 3% flap necrosis. CONCLUSIONS: This new model enables repetitive and simultaneous in vivo microscopic evaluation of microvascular hypoperfusion, apoptosis, and tissue necrosis in a random pattern flap. By the use of gene-targeted mice, it bears great potential to analyze distinct mechanisms of flap failure. It further represents an ideal tool to study novel protective strategies, including induction of angiogenesis, heat shock proteins, and HIF-1alpha.

Improved skin flap survival after local heat preconditioning in pigs.

BACKGROUND: Preconditioning induces the expression of heat shock proteins (HSPs), which can help a cell survive an acute episode of stress. Similar to the induction of HSP expression, the cell protection is independent of the type of stress. The aim of this study was to test in a large, randomized animal model, if skin flap survival may be improved by local heat preconditioning and induction of HSP 70. MATERIALS AND METHODS: Twenty-four hours before surgery, a heating blanket was laid on the buttocks of large white pigs. In the preconditioned group (n = 6), the blanket was warmed up to 43 degrees C for 3 x 30 min, whereas it was kept at room temperature in between the heating episodes as well as in the control animals (n = 6). A random pattern skin flap was raised on both sides of the buttocks. Flap survival was measured clinically. Induction of HSP and apoptosis were assessed quantitatively by immunohistochemistry and TUNEL assay, respectively. RESULTS: Preconditioning reduced flap necrosis from 40 +/- 8% of the total flap surface to 7 +/- 14% (P < 0.01). Induction of HSP was significantly higher in the experimental group (79 +/- 12% versus 42 +/- 13%, P < 0.01), whereas apoptosis in healthy flap tissue was reduced from 30 +/- 11 to 11 +/- 6 cells/visual field (P < 0.01). CONCLUSION: In the present study, necrosis and apoptosis rate of skin flaps could be reduced significantly due to local heat preconditioning. Our results suggest that ischemia-related wound healing complications could be diminished with local heat application, a most simple and least invasive method of preconditioning.

Modal power loss coefficients for highly overmoded rectangular dielectric waveguides based on free space modes.

A simple formalism to estimate modal power loss coefficients for an overmoded rectangular waveguide with rough surfaces is presented. The method is based on small index differences where the true radiation modes are approximated by free space modes. Loss coefficients are important in order to establish more accurate channel models for, e.g., optical backplane communication systems. The theory is validated by comparing the loss coefficients of a squeezed rectangular waveguide with the loss coefficients of a slab waveguide.

The dissection of the rectus abdominis myocutaneous flap with complete preservation of the anterior rectus sheath.

Harvesting the rectus abdominis myocutaneous flap results in defects in both the rectus abdominis muscle and the anterior rectus sheath, which may be circumvented by dissecting a perforator flap (DIEP flap) instead. However, the latter is associated with a reduction in the number of myocutaneous perforators nourishing the flap, which has been hypothesised to lead to an increased risk of partial flap failure. We present a technical modification that maintains all the feeding perforators within the flap while fully preserving the anterior rectus sheath. The anterior rectus sheath is incised along a line connecting the perforators. A muscle cuff including all the feeding perforators was raised with the flap. This technique was used in 20 consecutive patients. Nine patients underwent free TRAM flap transfers for breast reconstruction (10 flaps), and 11 patients underwent thoracic-wall reconstruction with a superiorly based pedicled flap. The median follow-up was 11 months. One patient with a pedicled flap developed a partial failure that required surgical revision; all other flaps healed spontaneously. One patient in each subset had preoperative abdominal-wall laxity that was partly corrected after surgery; no abdominal bulging or hernia occurred in the other patients. Our results suggest that the technical modification presented here may enable the surgeon to dissect a rectus abdominis myocutaneous flap with maximal perforator-related flap perfusion and minimal donor-site morbidity. An advantage over the DIEP flap is that this technique is applicable to both free and pedicled flaps.

Squamous cell carcinoma of the penile skin in a neovagina 20 years after male-to-female reassignment.

We present a patient who underwent male-to-female reassignment, and then developed squamous cell carcinoma during a complicated long-term follow-up. In very rare cases, squamous cell carcinoma may be considered in the differential diagnosis of sustained ulceration in neovaginas constructed by inverting the penile skin in male-to-female reassignments, in particular because clinical examination may be hampered by contractile scar formation of the neovaginal canal. Despite the lack of statistical evidence, it may be assumed that the heterotopic penile skin is at an increased risk of developing HPV-induced squamous cell carcinoma, especially if, over the years, there is a personal history of venereal warts.

Radical sternectomy and primary musculocutaneous flap reconstruction to control sternal osteitis.

OBJECTIVE: Sternal osteitis after median sternotomy is associated with considerable morbidity and mortality. The use of muscle and omentum flaps has been proved as valid adjunct to combat these severe infections. In this study we present our experience with a more radical approach. METHODS: Sternectomy consisted of the resection of the entire sternum, including the costochondral arches and the sternoclavicular joints, and was followed by the repair of the defect with musculocutaneous flaps without any restabilization of the thoracic wall. Thirteen patients received a vertical rectus abdominis musculocutaneous flap, 14 patients received a pedicled latissimus dorsi musculocutaneous flap, and 12 patients received a free latissimus dorsi musculocutaneous flap (total of 40 flaps in 39 patients of 66 patients who required surgical revision for sternal osteitis of 6078 total patients with sternotomies). RESULTS: Two patients died within 30 days after the operation (early mortality of 5.1%); however, they did not die of sternal infection, which was cured without any recurrence in all cases. Seventeen patients (44%) required secondary, mostly minor operations for local complications. Despite some paradoxic chest movements, the patient satisfaction rating was unanimously high at the long-term follow-up (0.4 to 8.5 years, median 2.3 years). The short- and long-term complication rates were similar in the three groups. CONCLUSION: We conclude that radical sternectomy and immediate musculocutaneous flap repair provided definitive control of sternal infection in even the most severe cases, thus reducing infection-related mortality. The trade-off was a substantial rate of local complications; however, these did not cause any relevant morbidity.

Comparative in vitro study of tissue welding using a 808 nm diode laser and a Ho:YAG laser.

In vitro porcine arteries and veins have been welded end-to-end using either a 808 nm diode laser combined with an indocyanine green enhanced albumin solder, or with a continuous-wave (cw) Ho:YAG laser without biological solder. The vascular stumps were approached to each other over a coronary dilatation catheter in order to obtain a precise alignment and good coaptation. Standard histology revealed for both welding techniques lateral tissue damage between 2 and 3 mm caused by laser-induced heat. Good solder attachment to the tissue was observed by the use of a scanning electron microscope. The vessels soldered with the 808 nm diode laser using albumin solder showed considerably higher tensile strength (1 N compared to 0.3 N) than vessels welded exclusively by Ho:YAG laser radiation. In contrast, leaking pressure (350 +/- 200 mmHg) and bursting pressure (457 +/- 200 mmHg) were found to be independent of the welding technique used. This study demonstrates that fast (total welding time about 2-5 min), stable and tight microvascular anastomosis can be achieved with the use of a dye-enhanced albumin laser soldering technique and an ancillary coronary dilatation catheter.

Endothelin receptor blockade improves oxygenation in contralateral TRAM flap tissue in pigs.

Partial skin and fat necrosis is the most common complication occurring in TRAM flaps. It is related to disturbances of the microcirculation and oxygenation in the contralateral part of the flap. It may be hypothesised that the development of necrosis is promoted by the vasoconstrictor endothelin, the production of which is enhanced in ischaemic flap tissues. The purpose of this study was to evaluate the effect of tezosentan, a new endothelin receptor blocker, on microcirculation and oxygenation in experimental TRAM flaps. The administration of tezosentan began preoperatively (3 mg/kg body weight) and then continued at a rate of 1.5 mg/kg/h. A TRAM flap with a skin island measuring 16 x 8 cm was raised in the middle of the epigastrium in minipigs. The flap was pedicled on the right superior epigastric vessels. Microcirculatory blood flow was measured with laser Doppler flowmetry and tissue oxygen tension was measured with a Clark-type microprobe. Dominant subcutaneous veins were cannulated in both the ipsilateral and the contralateral parts of the flap. Subdermal tissue oxygen tension in the contralateral part of the flap was significantly reduced 4h after surgery to 5 mmHg (ca. 48 mmHg in normal tissue) in the control group, but to only 12 mmHg in the group that had been administered tezosentan (P< 0.05). Furthermore, tezosentan significantly attenuated venous hypertension (14 mmHg versus 24 mmHg), as well as lactate (4.0 mmol/l versus 5.6 mmol/l) and haemoglobin (10.2 g/dl versus 11.4 g/dl) concentrations in the venous effluent of the contralateral part of the flap, although microcirculatory blood flow remained virtually unchanged. Our findings suggest that tezosentan improves oxygenation and metabolism in the jeopardised contralateral flap tissue, probably as a result of a decrease in venous vascular resistance and fluid extravasation.

Dynamic study of the distribution of microcirculatory blood flow in multiple splanchnic organs in septic shock.

OBJECTIVES: To study dynamic distribution of microcirculatory blood flow in multiple splanchnic organs during septic shock; to test the hypothesis that changes in microcirculatory blood flow in splanchnic organs correlate with changes in regional flow during septic shock. DESIGN: A prospective, controlled, animal study. SETTING: Animal laboratory in a university medical center. SUBJECTS: Nine anesthetized and mechanically ventilated domestic pigs. INTERVENTIONS: Systemic flow (cardiac output) was measured with thermodilution and regional (superior mesenteric artery) flow with transit time flowmetry. Local blood flow (microcirculatory flow) was continuously measured in splanchnic organs (gastric, jejunal, and colon mucosa, liver, and pancreas) and the kidney with multichannel laser Doppler flowmetry. Septic shock was induced with fecal peritonitis. After 240 mins of sepsis, intravenous fluids were administered to alter hypodynamic shock to hyperdynamic septic shock. MEASUREMENTS AND MAIN RESULTS: In this severe septic shock model, systemic and regional flows decreased by approximately 50% during the first 240 mins. Similar reductions were recorded in microcirculatory flow in the mucosa of the stomach (-41%; p < .001) and colon (-47%; p < .001). In the jejunal mucosa, on the other hand, flow remained virtually unchanged. Microcirculatory flow was also significantly decreased in the liver (-49%; p < .001), pancreas (-56%; p < .001), and kidney (-44%; p < .001). Administration of intravenous fluids at 240 mins was followed by three-fold increases in systemic and regional flows (approximately 70% above baseline). In the jejunal mucosa, flow also increased significantly above baseline (42%; p < .001), whereas in the stomach and the colon, it barely reached baseline. Kidney blood flow increased to baseline, whereas pancreas and liver flows remained 26% (p < .05) and 34% (p < .001), respectively, below baseline. CONCLUSION: Changes in microcirculatory blood flow in the splanchnic organs are heterogeneous, both in early hypodynamic and in hyperdynamic septic shock, and cannot be predicted from changes in systemic or regional flows. Microcirculatory blood flow in the jejunal mucosa remains constant during early septic shock, whereas pancreatic blood flow decreases significantly more than regional flow.

The effect of pedicle artery vasospasm on microhemodynamics in anatomically perfused and extended skin flap tissue.

The aim of this study was to evaluate quantitatively the influence of pedicle artery vasospasm on the microcirculation in skin flaps, particularly in the jeopardized extended portions. For this purpose, the hamster island skin flap model was used, which allowed for simultaneous assessment of hemodynamics in both the pedicle artery and the microvasculature of the flap by intravital microscopy. Vasospasm was induced by applying a V3 microvascular clamp for 30 seconds. Clamping resulted in a severe vasospasm, with the artery exhibiting a diameter of 7% +/- 2% (mean +/- standard error) of its original diameter (n = 10; p < 0.01), and with a reduction of total blood flow to the flap of 11% +/- 2% (p < 0.01). Diameter and blood flow recovered gradually to baseline levels after 25 and 15 minutes respectively. During recovery from severe pedicle artery vasospasm (moderate to mild vasospasm), the arterioles in the anatomically perfused flap tissue (n = 38) showed reactive vasodilation (p < 0.01), which was absent in the extended tissue (n = 49; p < 0.01 vs. anatomic). At a pedicle artery vasospasm of 50% of the original diameter, blood flow was restored to normal levels in the anatomically perfused arterioles, but remained below baseline in the extended part (partly p < 0.05 vs. baseline and anatomic). The findings suggest that the development of ischemic necrosis in extended flap portions may be promoted by prolonged, moderate vasospasm, which is well tolerated in the anatomically perfused tissue because of its high capacity for implementing compensatory local regulatory mechanisms.

Continuous measurements of microcirculatory blood flow in gastrointestinal organs during acute haemorrhage.

Hypoperfusion of splanchnic organs is an important contributor to the development of multiple organ failure after major surgery and trauma. During general anaesthesia and surgery we compared changes in systemic haemodynamics and regional blood flow with changes in the distribution of microcirculatory flow (MBF) in multiple splanchnic organs in pigs exposed to acute haemorrhage. Seven pigs (25 kg) were bled to a mean arterial pressure of 40 mm Hg; 180 min later the shed blood was retransfused. MBF was measured in the intestinal mucosa (stomach, jejunum, colon), pancreas, liver and kidney using a six-channel laser Doppler flowmeter. Cardiac output was measured by thermodilution and superior mesenteric artery flow by ultrasonic flowmetry. During haemorrhage, MBF in the gastric and colon mucosa and flow in the liver and kidney decreased to a similar extent to regional and systemic flows (30-50%). In contrast, MBF in the jejunal mucosa remained virtually unchanged and flow in the pancreas decreased significantly more than systemic and regional flows (60%, P < 0.05). We conclude that: (1) changes in the distribution of MBF in the gastrointestinal tract during acute haemorrhage are heterogeneous and cannot be predicted from changes in systemic or regional haemodynamics; (2) MBF in the jejunal mucosa did not decrease during haemorrhage, indicating that autoregulation of blood flow in the mucosa remained intact during shock; and (3) MBF in the pancreas decreased significantly more than systemic and regional flows during shock, suggesting that the pancreas is particularly vulnerable to haemorrhage.