Splenic artery loops: Potential splenic plexus stimulation sites for neuroimmunomodulatory-based anti-inflammatory therapy?

INTRODUCTION: The splenic plexus might represent a novel neuroimmunomodulatory therapeutic target as electrical stimulation of this tissue has been shown to have beneficial anti-inflammatory effects. Tortuous splenic artery segments (splenic artery loops), including their surrounding nerve plexus, have been evaluated as potential stimulation sites in humans. At present, however, our understanding of these loops and their surrounding nerve plexus is incomplete. This study aims to characterize the dimensions of these loops and their surrounding nerve tissue. MATERIALS AND METHODS: Six formaldehyde fixed human cadavers were dissected and qualitative and quantitative macro- and microscopic data on splenic artery loops and their surrounding nerve plexus were collected. RESULTS: One or multiple loops were observed in 83% of the studied specimens. These loops, including their surrounding nerve plexus could be easily dissected free circumferentially thereby providing sufficient space for further surgical intervention. The splenic plexus surrounding the loops contained a significant amount of nerves that contained predominantly sympathetic fibers. CONCLUSION: The results of this study support that splenic artery loops could represent suitable electrical splenic plexus stimulation sites in humans. Dimensions with respect to loop height and width, provide sufficient space for introduction of surgical instruments and electrode implantation, and, the dissected neurovascular bundles contain a substantial amount of sympathetic nerve tissue. This knowledge may contribute to further development of surgical techniques and neuroelectrode interface design.

Quantification of clinically applicable stimulation parameters for precision near-organ neuromodulation of human splenic nerves.

Neuromodulation is a new therapeutic pathway to treat inflammatory conditions by modulating the electrical signalling pattern of the autonomic connections to the spleen. However, targeting this sub-division of the nervous system presents specific challenges in translating nerve stimulation parameters. Firstly, autonomic nerves are typically embedded non-uniformly among visceral and connective tissues with complex interfacing requirements. Secondly, these nerves contain axons with populations of varying phenotypes leading to complexities for axon engagement and activation. Thirdly, clinical translational of methodologies attained using preclinical animal models are limited due to heterogeneity of the intra- and inter-species comparative anatomy and physiology. Here we demonstrate how this can be accomplished by the use of in silico modelling of target anatomy, and validation of these estimations through ex vivo human tissue electrophysiology studies. Neuroelectrical models are developed to address the challenges in translation of parameters, which provides strong input criteria for device design and dose selection prior to a first-in-human trial.

Disagreement between splenic switch-off and myocardial T1-mapping after caffeine intake.

Caffeine is an adenosine receptor antagonist and a possible cause of inadequate stress perfusion. Splenic switch-off (SSO) and splenic rest-stress T1-mapping have been proposed as indicators of stress adequacy during perfusion cardiac magnetic resonance (CMR). We compared myocardial rest-stress T1-mapping with SSO and splenic rest-stress T1-mapping in patients with and without recent coffee intake. We analyzed 344 consecutive patients suspected of myocardial ischemia with adenosine perfusion CMR. All 146 normal CMR studies with a normal T1-rest of the myocardium, used as standard of reference, were included and divided in two groups. 22 patients accidentally ingested coffee < 4 h before CMR, compared to control group of 124 patients without self-reported coffee intake. Two independent readers graded SSO visually. T1-reactivity (ΔT1) was defined as percentual difference in T1-rest and T1-stress. Follow-up data were extracted from electronic patients records. In patients with recent coffee intake SSO was identified in 96%, which showed no significant difference with SSO in controls (94%, p = 0.835), however event rates were significantly different (13.6 and 0.8%, respectively (p < 0.001), median FU 17 months). Myocardial ΔT1 in the coffee group (- 5.2%) was significantly lower compared to control (+ 4.0%, p < 0.001), in contrast to the splenic ΔT1 (- 3.7 and - 4.0%, p = 0.789). The splenic T1-mapping results failed to predict false negative results. SSO and splenic rest-stress T1-mapping are not reliable indicators of stress adequacy in patients with recent coffee intake. Therefore, the dark spleen sign does not indicate adequate myocardial stress in patients with recent caffeine intake. Myocardial rest-stress T1-mapping is an excellent indicator of stress adequacy during adenosine perfusion CMR.

Embolization for pediatric blunt splenic injury is an alternative to splenectomy when observation fails.

BACKGROUND: Management of splenic injury has shifted from operative to nonoperative management in both children and adults with reports of high success rates. Benefits of splenic conservation include decreased hospital stay, blood transfusion, and mortality, as well as avoidance of infectious complications. Angiography with embolization is an innovative adjunct to nonoperative management and has resulted in increased splenic salvage in adults; however, data in the pediatric population are scant. METHODS: A retrospective comparative study of a single-hospital trauma registry reviewed from 1999 to 2009. Patients 18 years and younger admitted with injury to the spleen were included. Children with penetrating injury were excluded. Children were divided into three categories by initial treatment: observation, embolization, or splenectomy. Data recorded include age, radiographic grade of injury, and Injury Severity Score (ISS). Groups were analyzed for success of initial treatment, requirement for transfusion of packed red blood cells, splenic salvage, and mortality. RESULTS: Registry review identified 259 children with blunt splenic injury. Initial treatment was observation in 227, embolization in 15, and splenectomy in 17. In the observation group, 9 (4%) of 227 children failed initial treatment; 8 of these underwent embolization, while 1 unerwent splenectomy. In the embolization group, 1 (7%) of 15 failed initial treatment and underwent splenectomy. Blood transfusion was required by 38 (17%) of 227 in the observation group, 6 (40%) of 15 (p = 0.02) in the embolization group, and 15 (88%) of 17 (p < 0.01) in the splenectomy group. Overall splenic salvage rate was 237 (92%) of 259. Three children died in the observation group, and four children died in the splenectomy group. There was no death in the embolization group. CONCLUSION: Splenic artery embolization for blunt trauma in children is associated with a higher blood transfusion rate compared with observation but offers a safe, intermediate alternative to splenectomy when observation fails. LEVEL OF EVIDENCE: Therapeutic study, level IV.

2 Hz electro-acupuncture at yinlingquan (SP9) and ququan (LR8) acupoints induces changes in blood flow in the liver and spleen.

According to the principles of traditional Chinese medicine, channels and collaterals within the body provide pathways through which qi and blood travel, and each channel or collateral is linked with a specific organ. The Yinlingquan (spleen 9, SP9) and Ququan (liver 8, LR8) acupoints represent the sea points of the spleen and liver meridians, respectively, from which qi and blood flow into their specific visceral organs. The purpose of this study was to investigate the changes in blood flow/perfusion in the liver and spleen resulting from the application of 2 Hz electro-acupuncture (EA) to the Yinlingquan (SP9) or Ququan (LR8) acupoints. A total of 18 Spragrue-Dawley rats were randomly divided into three groups of six rats each as follows: sham group receiving sham EA; Yinlingquan (SP9) group receiving 2 Hz EA, applied at bilateral Yinlingquan (SP9) acupoints; and Ququan (LR8) groups receiving 2 Hz EA, applied at bilateral Ququan (LR8) acupoints. The mean blood flow/perfusion of the spleen and liver was recorded using a laser Doppler blood flow monitor prior to EA (representing the baseline), during EA, and post-EA. Each measurement period lasted ten minutes. Nitric oxide levels were also measured from the right femoral arterial blood, following the conclusion of each series of blood flow/perfusion recordings. The results indicate that the sham EA did not increase the mean blood flow/perfusion in the liver or spleen; 2 Hz EA at bilateral Yinlingquan (SP9) acupoints increased the mean blood flow/perfusion in the spleen, but not in the liver. In contrast, 2 Hz EA at bilateral Ququan (LR8) acupoints increased the mean blood flow/perfusion in the liver, but not in the spleen. Nitric oxide levels showed no significant difference between any of the groups at any stage of the measurements. According to the results, we conclude that EA at the Yinlingquan (SP9) and Ququan (LR8) acupoints can increase the blood flow in the spleen and liver, respectively.

Evaluation of prothrombin complex concentrate and recombinant activated factor VII to reverse rivaroxaban in a rabbit model.

BACKGROUND: As a potent anticoagulant agent, rivaroxaban exposes a risk of bleeding. An effective way to reverse its effects is needed. Objectives were to study efficacy and safety of recombinant activated factor VII (rFVIIa) and prothrombin complex concentrate (PCC) to reverse the anticoagulant effect of an overdose of rivaroxaban in a rabbit model of bleeding and thrombosis. METHODS: First, a dose-ranging study assessed the minimal rivaroxaban dose that increased bleeding. Then, 48 anesthetized and ventilated rabbits were randomized into four groups: control (saline), rivaroxaban (rivaroxaban and saline), rFVIIa (rivaroxaban and rFVIIa), and PCC (rivaroxaban and PCC). The Folts model was applied: a stenosis and an injury were carried out on the carotid artery, inducing thrombosis, detected as cyclic flow reductions, which were recorded over 20 min. Then the following were measured: ear immersion bleeding time, clotting times, anti-Xa activity, thrombelastometric parameters, and thrombin generation test. Ultimately, a hepatosplenic section was performed and the total amount of blood loss after 15 min was evaluated as primary endpoint. RESULTS: Rivaroxaban increased blood loss (17 g [8-32] vs. 7 g [5-18] for control (median [range]), P = 0.0004), ear bleeding time, clotting times, thrombelastographic clotting time, and decreased thrombin generation. In contrast, rFVIIa decreased ear bleeding time (92 s [65-115] vs. 140 s [75-190], P < 0.02), but without efficacy on blood loss. PCC and rFVIIa decreased activated partial thromboplastin time as well as thrombelastographic clotting time. Regarding safety, neither rFVIIa nor PCC increased cyclic flow reductions. CONCLUSION: rFVIIa and PCC partially improved laboratory parameters, but did not reverse rivaroxaban induced-bleeding.

[Involvement of splenic hemangioma and rectal varices in a patient with klippel: trenaunay syndrome].

Klippel - Trenaunay syndrome (KTS) is characterized by a cutaneous vascular nevus of the involved extremity, bone and soft tissue hypertrophy of the extremity and venous malformations. We present a case of KTS with splenic hemangiomas and rectal varices. A 29-year-old woman was referred for intermittent hematochezia for several years. She had history with a number of operations for cutaneous and soft tissue hamangiomas since the age of one year old and for increased circumference of her left thigh during the last few months. Abdominal CT revealed multiple hemangiomas in the spleen, fusiform aneurysmal dilatation of the deep veins and soft tissue hemangiomas. There was no evidence of hepatosplenomegaly or liver cirrhosis. Colonoscopy revealed hemangiomatous involvement in the rectum. There were rectal varices without evidence of active bleeding. Upon venography of the left leg, we also found infiltrative dilated superficial veins in the subcutaneous tissue and aneurysmal dilatation of the deep veins. The patient was finally diagnosed with KTS, and treated with oral iron supplementation only, which has been tolerable to date. Intervention or surgery is not required. When gastrointestinal varices or hemangiomatous mucosal changes are detected in a young patient without definite underlying cause, KTS should be considered.

Involvement of Splenic Hemangioma and Rectal Varices in a Patient with Klippel - Trenaunay Syndrome / 대한소화기학회지

Klippel - Trenaunay syndrome (KTS) is characterized by a cutaneous vascular nevus of the involved extremity, bone and soft tissue hypertrophy of the extremity and venous malformations. We present a case of KTS with splenic hemangiomas and rectal varices. A 29-year-old woman was referred for intermittent hematochezia for several years. She had history with a number of operations for cutaneous and soft tissue hamangiomas since the age of one year old and for increased circumference of her left thigh during the last few months. Abdominal CT revealed multiple hemangiomas in the spleen, fusiform aneurysmal dilatation of the deep veins and soft tissue hemangiomas. There was no evidence of hepatosplenomegaly or liver cirrhosis. Colonoscopy revealed hemangiomatous involvement in the rectum. There were rectal varices without evidence of active bleeding. Upon venography of the left leg, we also found infiltrative dilated superficial veins in the subcutaneous tissue and aneurysmal dilatation of the deep veins. The patient was finally diagnosed with KTS, and treated with oral iron supplementation only, which has been tolerable to date. Intervention or surgery is not required. When gastrointestinal varices or hemangiomatous mucosal changes are detected in a young patient without definite underlying cause, KTS should be considered.

Estudo histomorfométrico do baço de ratos Wistar sadios e diabéticos suplementados ou não pela vitamina C / Histomorfometric study of the spleen of healthy and diabetic Wistar rats supplemented or not with vitamin C

O objetivo deste trabalho foi de analisar morfometricamente fragmentos histológicos do baço de animais normais e diabéticos, comparando os resultados encontrados e relacionando-os ao sexo e a suplementação da vitamina C. Foram utilizados 32 ratos Wistar, os quais foram analisados número de vasos, o número de folículos germinativos (polpa branca) e o diâmetro dos vasos de cada animal. As análises histológicas e morfometricas foram feitas em amostras de 5µm de espessura demonstrando que: na quantidade de folículos germinativos, observamos resultados comparando, independente do sexo, animais controles suplementados com vitamina C e controles não suplementados (p£"0,05; F=0,1452); na quantidade de vasos, observamos resultados comparando, fêmeas diabéticas suplementadas pela vitamina C e fêmeas diabéticas não suplementadas (pd"0,05; F=6.8893); e no diâmetro dos vasos, observamos resultados comparando fêmeas, tanto no grupo controle quanto ao grupo diabético, suplementadas pela vitamina C quando comparadas às fêmeas não suplementadas pela vitamina C (p<0,05; U=121.50; Z(U)=2.1234) e (p<0,05; F=4.8134). De um modo geral, a indução de diabetess modifica o diâmetro vascular nas fêmeas e que a administração de vitamina C interfere nos dados métricos relativos ao diâmetro vascular somente nas fêmeas.

The objective of this study was to analyze morphometric histological shatters of the spleen of normal and diabetic animals, comparing the joined results and relating them in the sex and the suplementation of vitamin C. Had been used 32 Wistar rats, which had been analyzed: number of vases; the number of germinative folicules (white pulp); and the diameter of the vases of each animal. Histological and morphometric analyses were applied on 5µm thick samples and showed that: in the amount of germinative folicules, we observe resulted comparing, independent of the sex, animals controls supplemented with vitamin C and controls not supplemented (p£0.05; F=0.1452); in the amount of vases, we observe resulted comparing, of diabetic females supplemented by vitamin C when compared with not supplemented (pd"0.05; F=6.8893); and in the diameter of the vases, we observe resulted comparing females, as much in the group has controlled how much to the diabetic group, supplemented with vitamin C when compared with the females not supplemented with vitamin C (p<0.05; U=121.50; Z(U)=2.1234) and (p<0,05; F=4.8134). In a general way, the induction of diabetes modifies the vascular diameter in the females and that the vitamin C administration only intervenes with relative metric data to the vascular diameter in the females.

Enteral glutamine supplementation impairs intestinal blood flow in rats.

BACKGROUND: Clinical studies have shown that enteral immune-enhancing diets (IEDs) containing l-glutamine decrease septic complications and length of stay in some patient populations. Animal studies suggest IED benefits might include augmented gut blood flow. We hypothesized that enteral glutamine supplementation modulates gastrointestinal blood flow. METHODS: Blood flow was measured in male Sprague-Dawley rats via the colorimetric microsphere technique at baseline, 60, and 120 minutes. Four groups were studied: (1) control diet (CD) + enteral glutamine; (2) CD + enteral glycine; (3) CD + enteral saline; and (4) CD + intravenous glutamine. RESULTS: There were no differences in blood pressure or heart rate in any group. Group 1 blood flow was decreased at 120 minutes compared with controls (groups 2 and 3) in small intestine, colon, spleen, and pancreas, whereas the intravenous glutamine group (group 4) had no effect on blood flow. CONCLUSIONS: Enteral glutamine supplementation (as in IEDs) appears to impair gastrointestinal blood flow. Because glutamine provides energy directly to active enterocytes, enteral glutamine availability might diminish metabolic stimuli of absorptive hyperemia. This finding might partially explain the benefits observed with parenteral versus enteral glutamine supplementation in clinical studies (such as bone-marrow-transplant patients).

Postbiopsy splenic bleeding in a dog model: comparison of cauterization, embolization, and plugging of the needle tract.

OBJECTIVE: The purpose of our study was to compare radiofrequency cauterization, embolization using an absorbable gelatin sponge, and a Histoacryl-Lipiodol mixture plugging as postbiopsy bleeding reduction methods after splenic core needle biopsy in a dog model. MATERIALS AND METHODS: Eleven mongrel dogs were randomly separated into nonheparinized (n = 5) and heparinized (n = 6) groups. Eight splenic biopsies per animal were performed using an 18-gauge automated core biopsy needle: two as controls, two ablated by radiofrequency, two embolized using an absorbable gelatin sponge, and two plugged using a Histoacryl-Lipiodol mixture. Procedure times and postbiopsy bleeding amounts were assessed. Statistically significant differences were determined by repeated measures analysis of variance; the Tukey-Kramer test for multiple comparisons was used for post hoc comparisons. Three-day follow-up CT scans were obtained to check for procedure-related complications or delayed bleeding. RESULTS: The postbiopsy bleeding reduction groups showed significantly less blood loss than the control group for both the nonheparinized (p < 0.0001) and heparinized groups (p < 0.0001). In the heparinized group, both radiofrequency cauterization (p < 0.01) and gelatin sponge embolization (p < 0.05) significantly reduced bleeding compared with Histoacryl-Lipiodol mixture plugging. Gelatin sponge embolization was the longest procedure (p < 0.001). On follow-up CT, no delayed bleeding was observed. However, multiple Histoacryl-Lipiodol emboli were observed in the splenic and portal veins in all the dogs we treated. CONCLUSION: Radiofrequency cauterization was found to be the most useful postbiopsy bleeding reduction method in terms of the amount of bleeding and the procedure time.

[Viability of the spleen in rats after ligation of the splenic vessels: effects of hyperbaric oxygen therapy]. / Viabilidade do baço de ratos após a ligadura dos vasos esplênicos: efeito do tratamento com oxigênio hiperbárico.

OBJECTIVE: To investigate the effects of splenic artery and vein ligation and the influence of hyperbaric oxygen after the double vascular ligation on the viability of spleen tissue. METHODS: Sixty nine adult male Wistar rats (285-375 g) were randomly separated in three groups: group 1, four rats, sham operated, group 2, 34 rats, submitted to simultaneous splenic artery and vein ligation and group 3, 31 rats, submitted to hyperbaric oxygen during 11 days, after double vascular ligation. All animals were killed on day 12 after surgery. The spleen was removed and paraffin embedded for microscopic examination. RESULTS: In the groups submitted to vascular ligation, the spleen was normal in 8.82% of rats not treated with hyperbaric oxygen and in 45.16% of rats that received hyperbaric oxygen after vascular ligation (p=0.01). In the spleens with white infarct, the mass of preserved splenic tissue in relation to the total body mass did not differ between the groups treated or not with hyperbaric oxygen. The preserved splenic tissue had normal histology in both groups. The healing process was more accelerated in the group of rats treated with hyperbaric oxygen. CONCLUSION: Results demonstrate that exposure to hyperbaric oxygen increased the frequency of total spleen mass preservation after simultaneous ligation of the splenic artery and vein but did not alter the percentage of the spleen's viable area, however the healing process in necrotic areas was accelerated.

Viabilidade do baço de ratos após a ligadura dos vasos esplênicos: efeito do tratamento com oxigênio hiperbárico / Viability of the spleen in rats after ligation of the splenic vessels: effects of hyperbaric oxygen therapy

OBJETIVO: Verificar o efeito da ligadura dos vasos esplênicos principais no baço de ratos e a influência do tratamento com o oxigênio hiperbárico após a ligadura. MÉTODOS: Foram operados 69 ratos Wistar, machos, de 285g a 375 g. Os animais foram divididos aleatoriamente em três grupos: grupo 1: quatro ratos, simulação; grupo 2: 34 ratos, ligadura simultânea da artéria e veia esplênica; grupo 3: 31 ratos, ligadura da artéria e veia esplênica seguida de oxigenioterapia hiperbárica no pós-operatório por 11 dias, sendo mortos no 12° dia. O baço era retirado e incluído em parafina para estudo microscópico. RESULTADOS: O baço era normal em 8,82 por cento e 45,16 por cento, respectivamente, no grupo que sofreu a ligadura vascular sem ou com oxigenioterapia hiperbárica (p= 0,01). O percentual de massa viável do tecido esplênico nos baços que infartaram em relação ao percentual da massa corporal dos animais não diferiu entre os grupos 2 e 3. O aspecto histopatológico mostrou arquitetura preservada na porção não infartada nos dois grupos e neoformação conjuntivo-vascular cicatricial mais acentuada no grupo que recebeu oxigênio hiperbárico. CONCLUSÕES: O tratamento com oxigênio hiperbárico, a partir do pós-operatório imediato, após a ligadura simultânea da artéria e da veia esplênicas, reduziu significativamente a freqüência dos infartos, mas não alterou o percentual de massa viável dos baços, quando o infarto ocorreu, e acelerou o processo de cicatrização, com aumento da proliferação de fibroblastos e da neoformação vascular.

Hyperthermia-enhanced splenic cytokine gene expression is mediated by the sympathetic nervous system.

Whole body hyperthermia (WBH) has been used in experimental settings as an adjunct to radiochemotherapy for the treatment of various malignant diseases. The therapeutic effect of WBH has been hypothesized to involve activation of the immune system, although the effect of hyperthermia-induced activation of sympathetic nerve discharge (SND) on splenic immune function is not known. We tested the hypothesis that heating-induced splenic sympathoexcitation would alter splenic cytokine gene expression as determined using gene array and real-time RT-PCR analyses. Experiments were performed in splenic-intact and splenic-denervated anesthetized Sprague-Dawley rats (n=32). Splenic SND was increased during heating (internal temperature increased from 38 degrees to 41 degrees C) in splenic-intact rats but remained unchanged in nonheated splenic-intact rats. Splenic interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and growth-regulated oncogene 1 (GRO 1) mRNA expression was higher in heated than in nonheated splenic-intact rats. Splenic IL-1beta, IL-6, and GRO 1 mRNA expression was reduced in heated splenic-denervated compared with heated splenic-intact rats, but did not differ between heated splenic-denervated and nonheated splenic-intact rats. These results support the hypothesis that hyperthermia-induced activation of splenic SND enhances splenic cytokine gene expression.

Influence of spleen meridian herbs on the harmonic spectrum of the arterial pulse.

Pulse analysis is a powerful method in Chinese medicine. We suggest that the effect of herbal medicine is to redistribute the blood to organs and meridians. In this report, by injecting extracts into rats and then analyzing the blood pressure wave measured at the caudate arteries, we studied eight important spleen meridian related herbs: They were Semen Lablab, Fructus Amomi Globosi, Rhizoma Atractylodis Macrocephalae, Rhizoma Atractylodis, Tuber Pinelliae, Radix Codonopsitis, Pericarpium Aurantii and Rhizoma Polygonati. All eight herbs increased the intensity of the 3rd harmonic (C3) of the pressure pulse which is correlated to the spleen and spleen meridian, as described in traditional Chinese medical literature. All of them also increased the 2nd harmonic (which is correlated to the kidney and the kidney meridian) as well as decreased the heart load (DC term of pressure wave, C0). Tuber Pinelliae, Radix Codonopsitis, Pericarpium Aurantii and Rhizoma Polygonati decreased the 1st harmonic (correlated to the liver meridian) significantly, while Rhizoma Atractylodis Macrocephalae only decreased C1 slightly. Except for Semen Lablab, all the others decreased the intensity of the 5th (stomach meridian) and the 7th harmonics. The effects of kidney herbs: Cortex Eucommiae and Radix Achyranthis were also shown for comparison.

No effect of D-myo-inositol-1,2,6-triphosphate on vasoconstriction evoked by neuropeptide Y and non-adrenergic sympathetic nerve stimulation.

The effects of the proposed neuropeptide Y (NPY) antagonist, D-myo-inositol-1,2,6-triphosphate (PP56), on vasoconstrictor responses evoked by NPY and non-adrenergic sympathetic nerve stimulation were investigated in the pig in vivo. Under control conditions, exogenous NPY evoked a dose-dependent increase in arterial blood pressure and vasoconstriction in spleen, kidney and skeletal muscle. After administration of PP56 (50 mg/kg), which transiently reduced systemic blood pressure by 18 +/- 5 mm Hg, the vascular responses evoked by NPY did not differ from those observed under control conditions. Stimulation of the splenic nerve and the lumbar sympathetic chain with 20-Hz burst activity in reserpine-pretreated pigs, which are devoid of their noradrenaline content, decreased splenic and hindlimb vascular conductance by 67 +/- 7 and 57 +/- 7%, respectively, under control conditions. In the presence of PP56 the nerve stimulation-evoked reductions in splenic and hindlimb vascular conductance were slightly but not significantly reduced to 59 +/- 9 and 48 +/- 7%, respectively. It is concluded that PP56 in the presently used high dose, which causes non-selective inhibition of vasoconstriction in the rat, cannot be used as an antagonist of vasoconstrictor responses evoked by NPY or non-adrenergic sympathetic nerve stimulation in the pig.

Effects of splenectomy on hemodynamic performance in fixed volume canine hemorrhagic shock.

Studies of canine hemorrhagic shock commonly use a splenectomized fixed-pressure model. Splenectomy is recommended in this model to avoid variable degrees of autotransfusion that reduce the reliability of mortality estimates and blood volume measurements. The effects of splenectomy on a non-lethal fixed-volume canine hemorrhage have not been established. The purpose of this study was to investigate cardiovascular and biochemical effects of splenectomy in fixed-volume canine hemorrhagic shock. Nineteen beagles of uniform size and weight were bled 50% of their estimated blood volumes over 1 hr and then left without therapeutic intervention for a 90 min stabilization period. Arterial blood pressure (MAP), central venous pressure, pulmonary artery pressure, heart rate (HR), cardiac output, glucose, lactate, arterial and mixed venous blood gases, and hematocrit (HCT) were measured at regular intervals. Cardiac index (CI), stroke volume, and oxygen saturation (O2SAT), delivery (O2DEL) and consumption (O2CON) were calculated at these intervals. Results from ten control animals were compared to those from nine animals that had been splenectomized 2 wk prior to hemorrhage. During the hemorrhage period, there were no significant differences observed between groups for HR, MAP, or O2DEL. CI remained higher (P less than 0.025) and HCT lower (28.9 +/- 4.7 vs 39.8 +/- 4.5) (P less than 0.001) in splenectomized animals. Immediately following hemorrhage there were no significant differences in the mean values for HR, CI, MAP, or serum lactate. O2DEL however, was significantly higher in control animals (P less than 0.05). During stabilization MAP, CI, and O2DEL rose while HCT fell in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Variability of heating patterns in animals by magnetic induction hyperthermia.

In a test of electromagnetic induction hyperthermia to deep viscera of a live dog model, we found that heating was not uniform to any depth, but was quite variable. In general, there was a thermal gradient between peripheral and central portions of the transposed spleen of about 1 degree C. Though heat generation within the abdomen was not uniform, its temperature pattern in the alive animal resulted in significant heating of that part of the organ that had been surgically placed at the center of the animal. This heating could not be explained by perfusion with regionally heated core blood. Our results indicate that extensive investigations in living systems and complex dynamic phantoms will be necessary before individual patient response can be predicted.

Deep-heating characteristics of an RF capacitive heating device.

An RF capacitive heating device was constructed and its deep-heating characteristics were studied using three mini-pigs. The deep-heating ability of RF capacitive heating was found to be improved by enlarging the electrodes, driving at 8 MHz, cooling the skin under the electrodes, inserting a bolus between the body and the electrodes and considering the anatomical structure of the body. The heating characteristics obtained were as follows. When applicators were placed on both sides of the abdomen of a mini-pig, 7 mm in fat layer thickness and 23 cm in lateral chest thickness, the increase in temperature of the deep part was greater than that of the fat layer. When applicators were placed on the posterior and anterior abdomen, overheating was noted in the fat and muscle near the back. The temperature was highest in a mock tumour, made by blocking blood flow to the spleen. The bio-heat equation revealed that RF capacitive heating accompanied by surface cooling at 10 degrees C could heat the deep portion of the body to 42 degrees C without excessive heating of a 1.6 cm thick fat layer.