Distension of the pulmonary vein - atrial junctions and plasma vasopressin in the chloralose-anaesthetized dog

The effects of localized distension of the pulmonary vein - left atrial junctions on plasma arginine vasopressin (AVP) have been examined in chloralose anaesthetized dogs. Pulmonary vein distension caused an increase in heart rate and a decrease in plasma AVP concentration. Cooling the vagosympathetic nerves to 10 degrees C caused an increase in arterial pressure and plasma AVP concentration and prevented the changes in heart rate and plasma AVP concentration caused by pulmonary vein distension. Cooling the vagus nerves to 16 degrees C did not change heart rate, arterial pressure, or plasma AVP concentration but significantly reduced the changes in heart rate and plasma AVP concentration caused by pulmonary vein distension. Propranolol (0.5 mg/kg) decreased heart rate and prevented the increase in heart rate associated with pulmonary vein distension but did not abolish the decrease in plasma AVP concentration. It is concluded that distension of the pulmonary vein - left atrial junctions causes a decrease in plasma AVP concentration by stimulating atrial receptors with myelinated afferent fibres. The decrease in plasma AVP concentration is not secondary to the reflex changes in heart rate caused by pulmonary vein distension.     

Manual pressure distension of the human saphenous vein changes its biomechanical properties-implication for coronary artery bypass grafting

Patency rates of saphenous vein grafts following coronary artery bypass grafting (CABG) depend on multiple factors. Information regarding the impact of biomechanical properties of vein grafts on patency rates is not available. The objective of the present study was to evaluate whether uncontrolled manual pressure distension during routine preparation of the saphenous vein in CABG-induced changes in the biomechanical properties of the vein. The morphometric and stress-strain properties were studied in isolated segments of the saphenous vein from 12 patients undergoing elective CABG. Six segments were manually distended without pressure control and six were not distended. The mechanical test was performed as a ramp inflation using syringe pump. The vein dimensions were obtained from digitised images at different pressures as well as at the no-load and zero-stress states. The circumferences, the wall and lumen area, the wall thickness, and the outer diameter as function of the applied pressure were largest in the segments with uncontrolled manual distension compared to those without distension (P<0.05). The opening angle and the absolute value of the residual strains were lower (P<0.01) and the circumferential stress-strain curve shifted to the left, indicating the wall became stiffer with uncontrolled manual distension compared to those without distension (P<0.05). In conclusion, manual pressure distension changed the morphometric and biomechanical properties of the saphenous vein. The perspective is that studies on biomechanical properties on the saphenous vein may guide surgeons how to handle graft material without causing major changes of the biomechanical properties during harvesting and preparation.     

Graded compression for preventing deep venous thrombosis.

The physiological effects of static compression of the leg have recently been reinvestigated. Graded compression extending from the ankle to the upper thigh produces the maximum increase in velocity of femoral vein blood flow and the maximum decrease in clearance times of contrast media and radioisotopes from the deep veins of the calf. This type of compression may be easily produced by a specially designed elastic stocking. Graded compression was used in a controlled clinical trial of 98 patients undergoing major operations to assess its effect on isotopically diagnosed deep vein thrombosis. The incidence of deep vein thrombosis was 49% in the control group and 23% in the treated groups. No complications were caused by the stockings. Carefully designed and correctly applied static compression is a safe and effective method of reducing the incidence of deep vein thrombosis.     

Effect of passive myocardium on the compliance of porcine coronary arteries

The objective of this study was to determine the effect of passive myocardium on the coronary arteries under distension and compression. To simulate distension and compression, we placed a diastolic-arrested heart in a Lucite box, where both the intravascular pressure and external (box) pressure were varied independently and expressed as a pressure difference (DeltaP = intravascular pressure - box pressure). The DeltaP-cross-sectional area relationship of the first several generations of porcine coronary arteries and the DeltaP-volume relationship of the coronary arterial tree (vessels >0.5 mm in diameter) were determined using a video densitometric technique in the range of +150 to -150 mmHg. The vasodilated left anterior descending (LAD) coronary artery of six KCl-arrested hearts were perfused with iodine and 3% Cab-O-Sil. The intravascular pressure was varied in a triangular pattern, whereas the absolute cross-sectional area of each vessel and the total arterial volume were calculated using video densitometry under different box pressures (0, 50, 100, and 150 mmHg). In the range of positive DeltaP, we found that the compliance of the proximal LAD artery in situ (4.85 +/- 3.8 x 10-3 mm2/mmHg) is smaller than that of the same artery in vitro (16.5 +/- 6 x 10-3 mm2/mmHg; P = 0.009). Hence, the myocardium restricts the compliance of the epicardial artery under distension. In the negative DeltaP range, the LAD artery does not collapse, whereas the same vessel readily collapses when tested in vitro. Hence, we conclude that myocardial tethering prevents collapse of large blood vessel under compression.     

Congenital venous hypoplasia in the liver of rats.

Narrowed and rudimentary portal vein branches were observed in the livers of specified-pathogen-free rats which, at the age of 6-11 weeks, showed poor condition and reatrded growth. At autopsy abdominal venous distension and congestion suggestive of portal hypertension and collateral circulation appeared to have developed. The cause of the observations and their significance in view of the use of the rats are unknown.     

Growth on an arteriovenous malformation: a case report

A case of an intracerebral arteriovenous malformation that grew is presented. On the initial arteriogram only one early filling vein was seen in the region where a large arteriovenous malformation was present eight years later. The patient''s headaches were relieved by antihypertensive medications. The authors speculate that distension of the AVM caused the headaches.     

Effect of NO, phenylephrine, and hypoxemia on ductus venosus diameter in fetal sheep

To study the regulation of the ductus venosus (DV) inlet in vivo, we measured the effect of vasoactive substances and hypoxemia on its diameter in nine fetal sheep in utero at 0.9 gestation under ketamine-diazepam anesthesia. Catheters were inserted into an umbilical vein and a fetal common carotid artery, and a flowmeter was placed around the umbilical veins. Ultrasound measurements of the diameter of the fetal DV during normoxic baseline conditions [fetal arterial PO(2) (PaO(2)) 24 mmHg] were compared with measurements during infusion of sodium nitroprusside (SNP; 1.3, 2.6, and 6.5 microg. kg(-1). min(-1)) or the alpha(1)-adrenergic agonist phenylephrine (6.5 microg. kg(-1). min(-1)) into the umbilical vein or during hypoxemia (fetal Pa(O(2)) reduced to 10 mmHg). SNP increased the DV inlet diameter by 23%, but phenylephrine had no effect. Hypoxemia caused a 61% increase of the inlet diameter and a distension of the entire vessel. We conclude that the DV inlet is tonically constricted, because nitric oxide dilates it but an alpha(1)-adrenergic agonist does not potentiate constriction. Hypoxemia causes a marked distension of the entire DV.     

Autotransplantation of islands of Langerhans in dogs

Six dogs received intraportally an autograft of isolated non purified pancreatic islets after total pancreatectomy. The isolation was made by collagenase technique, using a quarter to a half of the total pancreatic mass. The results of different transplantation technics are discussed. We conclude the necessity of: 1) a good venous distension of the pancreas, 2) the use of at least a third of the pancreatic gland to prepare the islets, 3) a tissue reinjection the closest as possible of the portal vein.     

Control of breathing in anesthetized dogs by a left-heart baroreflex

Anesthetized open-chest dogs on cardiopulmonary bypass were used to test the hypothesis that breathing reflexly responds to distension of the left-heart chambers. Bypass perfusion withdrew systemic flow from the right atrium and returned it to the aorta after gas exchange. Ventricles were fibrillated. The left heart was isolated by tying all pulmonary veins, and it was perfused separately at low flow admitted through one pulmonary vein and withdrawn from the ventricle. Left-heart pressure was intermittently raised abruptly from a nominal base line of 0 by partial occlusion of outflow. Pressures from approximately 10 to 50 cmH2O caused proportional increases in breathing frequency and decreases in expiratory and inspiratory times. Changes occurred immediately, reached a plateau within approximately 20 s, and were sustained for periods of observation as long as 3 min. Recovery to base line followed stimulus removal. Vagal cooling to 8 degrees C prevented responses, but autonomic ganglion blockade with hexamethonium had no effect. I conclude that breathing may be stimulated by left-heart distension and that this is mediated by large myelinated vagal afferents.     

Prevention of Early Postoperative Deep Vein Thrombosis by Intermittent Compression of the Leg during Surgery

A clinical trial is described in which the effect of intermittent compression of the lower limb during surgery on the incidence of early postoperative deep vein thrombosis was assessed. Deep vein thromboses were diagnosed by the ¹²⁵I-fibrinogen uptake test. Peroperative intermittent compression was achieved by means of an inflatable plastic splint coupled to a pneumatic controller. By compressing only one leg of each patient, each patient acted as his own control.With a sequential statistical analysis, 39 patients were required to pass the 5% level of significance. Eleven thrombi were detected in the control (uncompressed) legs and two occurred in the compressed legs; one of the latter was bilateral. The investigation shows that increasing the pulsatility of the venous flow in the leg is a potent prophylactic against postoperative deep vein thrombosis.     

Safety of withholding anticoagulation in pregnant women with suspected deep vein thrombosis following negative serial compression ultrasound and iliac vein imaging

Background:

Compression ultrasonography performed serially over a 7-day period is recommended for the diagnosis of deep vein thrombosis in symptomatic pregnant women, but whether this approach is safe is unknown. We evaluated the safety of withholding anticoagulation from pregnant women with suspected deep vein thrombosis following negative serial compression ultrasonography and iliac vein imaging.

Methods:

Consecutive pregnant women who presented with suspected deep vein thrombosis underwent compression ultrasonography and Doppler imaging of the iliac vein of the symptomatic leg(s). Women whose initial test results were negative underwent serial testing on 2 occasions over the next 7 days. Women not diagnosed with deep vein thrombosis were followed for a minimum of 3 months for the development of symptomatic deep vein thrombosis or pulmonary embolism.

Results:

In total, 221 pregnant women presented with suspected deep vein thrombosis. Deep vein thrombosis was diagnosed in 16 (7.2%) women by initial compression ultrasonography and Doppler studies; none were identified as having deep vein thrombosis on serial testing. One patient with normal serial testing had a pulmonary embolism diagnosed 7 weeks later. The overall prevalence of deep vein thrombosis was 7.7% (17/221); of these, 65% (11/17) of cases were isolated to the iliofemoral veins and 12% (2/17) were isolated iliac deep vein thromboses. The incidence of venous thromboembolism during follow-up was 0.49% (95% confidence interval [CI] 0.09%–2.71%). The sensitivity of serial compression ultrasonography with Doppler imaging was 94.1% (95% CI 69.2%–99.7%), the negative predictive value was 99.5% (95% CI 96.9%–100%), and the negative likelihood ratio was 0.068 (95% CI 0.01–0.39).

Interpretation:

Serial compression ultrasonography with Doppler imaging of the iliac vein performed over a 7-day period excludes deep-vein thrombosis in symptomatic pregnant women.Over the last 2 decades, venous compression ultrasonography has become the imaging test of choice for diagnosing deep vein thrombosis in the lower extremities of men and nonpregnant women.^1–4 Although this test is highly sensitive (about 97%) for deep vein thrombosis involving the femoral and popliteal veins, compression ultrasonography is less sensitive for the detection of isolated deep vein thrombosis in the calf.⁵ Because proximal propagation of isolated calf deep vein thrombosis occurs in about 20% of cases, serial compression ultrasonography performed over a 7-day period is recommended to definitely exclude such thromboses if the results of the initial compression ultrasound are negative.⁶The use of serial compression ultrasonography in symptomatic men and nonpregnant women has been validated in prospective studies,^1,7 suggesting that withholding anticoagulation from symptomatic patients whose serial compression ultrasound results are negative is safe, with less than 2% of patients subsequently being diagnosed with deep vein thrombosis.^1,7,8 Although the use of serial compression ultrasonography has not been validated in pregnant women, this strategy is also advocated for symptomatic pregnant women.⁹The appeal of using compression ultrasonography for diagnosing deep vein thrombosis in pregnant women is obvious: it is noninvasive, widely available and does not expose the fetus to ionizing radiation. However, generalizing results from studies involving men and nonpregnant women to pregnant women is problematic because of differences in clinical presentation and anatomic distribution of deep vein thromboses.¹⁰ Compared with men and nonpregnant women, pregnant women more often present with very proximal deep vein thrombosis (including isolated iliac vein deep vein thrombosis); isolated distal calf deep vein thromboses are infrequent.¹⁰ In a recent review of the literature, we found that 62% of all deep vein thromboses in symptomatic pregnant women were in the iliofemoral veins, 17% were in the iliac vein alone, and 6% were in the calf veins.¹⁰ In contrast, in the general population, more than 80% of deep vein thromboses involved calf veins, and iliofemoral deep vein thromboses or isolated iliac veins are uncommon (< 5%).^1–4Physiologic changes associated with pregnancy might affect blood flow patterns and normal compressibility of the proximal veins, thereby affecting the diagnostic accuracy of compression ultrasonograpy. This technique cannot be used to detect isolated deep vein thromboses in the iliac vein; these veins are not compressible because of their intrapelvic location. Whether Doppler studies are sensitive for detecting deep vein thromboses in these high proximal veins (i.e., iliac veins) has not been well studied, but data suggest that this method of detection compares favourably to compression ultrasonography in men and nonpregnant women for proximal deep vein thromboses.¹¹ The use of Doppler imaging in pregnant women for the purpose of detecting iliac vein deep vein thromboses has been reported in the literature,^12,13 but it has not been adequately evaluated.Currently, the standard practice of diagnosing deep vein thrombosis in symptomatic pregnant women is by compression ultrasonography. If the results of the compression ultrasound are negative, Doppler imaging of the iliac vein (with or without vagal manoeuvres) is recommended, particularly for women with a high clinical probability of deep vein thrombosis in the iliac vein.^9,12,13 This diagnostic approach is advocated despite the absence of any prospective studies validating its use. In this study, we evaluated the diagnostic accuracy of serial compression ultrasonography and Doppler imaging of the iliac veins over a 7-day period among symptomatic pregnant women.     

Morphologic and surgical indications for temporary partial occlusion of the inferior vena cava by soft clipping

In the experiment performed on 72 dogs peculiarities of morphological changes in the posterior vena cava wall have been studied at a temporal disturbance of blood flow in it by means of a complete or partial ligation of the vessel with catgut, a complete or partial closing of the lumen of the vein by means of a wavy catgut clip, covered with glue MK-6. Predominance of the soft clipping at the temporal disturbance of the blood flow in the vein with the aim of prophylaxis of thromboembolism of the pulmonary artery has been demonstrated. At the soft clipping in the place of the vascular compression, the blood flow partially remains, thrombi in the lumen do not form, rough dystrophic and necrotic changes in the vein are absent, that is the organ preservation of the vein is ensured. In 1.5 months the vascular lumen is completely restored, and structure of its wall at the place of compression does not differ from the normal one.     

Enteric descending and afferent neural signaling stimulated by giant migrating contractions: essential contributing factors to visceral pain

We investigated whether strong compression of an intestinal segment by giant migrating contractions (GMCs) initiates pseudoaffective signals from the gut, similar to those initiated by its distension with a balloon. The experiments were performed on conscious dogs by using close intra-arterial infusions of test substances that affect the receptors only in the infused segment. The stimulation of GMCs by close intra-arterial infusion of CGRP or distension of an intestinal segment by balloon increased the heart rate; the increase in heart rate was greater when the balloon distension and GMCs occurred concurrently in separate intestinal segments. The suppression of contractility in the distended segment blocked the increase in heart rate. By contrast, the stimulation of rhythmic phasic contractions (RPCs) or their spontaneous occurrence did not increase the heart rate. The occurrence of GMCs as well as intestinal distension also produced descending inhibition. The descending inhibition was blocked by the inhibition of nitric oxide synthase, but it was unaffected by the inhibition of adenylyl cyclase, purinergic receptors P2X and P2Y, and muscarinic receptors M(1) and M(2). The synaptic transmission for descending inhibition was mediated primarily by nicotinic receptors and activation of nitric oxide synthase. It was unaffected by the inhibition of tachykinin receptors NK(1), NK(2), and NK(3); serotonin receptors 5-HT(1A), 5-HT(2)/5-HT(1C), 5-HT(3), and 5-HT(4); and muscarinic receptors. Our findings show that GMCs, but not RPCs, initiate pseudoaffective signals from the gut. In the presence of visceral hypersensitivity or impaired descending inhibition, the GMCs may become a noxious stimulus.     

Prevention of Deep Vein Thrombosis by Intermittent Pneumatic Compression of Calf

A consecutive, randomly allocated, controlled clinical trial of the prophylactic effect of intermittent pneumatic compression of the calf on the incidence of postoperative deep vein thrombosis showed that in patients without malignant disease there was a highly significant reduction in the incidence of thrombosis. In patients with malignant disease the incidence of thrombosis was higher than in those without, and there was no reduction in incidence by the application of intermittent compression. In the absence of malignant disease, severity of operation and the age of the patient were the most significant aetiological factors. We found no relation between the incidence of deep venous thrombosis and obesity, length of preoperative stay, location of hospital, or duration of anaesthesia. We suggest that intermittent pneumatic compression as used in this trial is a safe, effective, and extremely practical method of preventing postoperative deep vein thrombosis in patients not suffering from malignant disease.     

Biomechanics of the venous wall under simulated arterial conditions

The failure of vein graft conduits implanted in the arterial circulation has been hypothesized to occur in part due to the exposure of the graft to altered biomechanical and fluid shearing forces. In the present study, these forces are characterized for canine internal jugular veins (IJV) exposed to realistic arterial flow dynamics. Freshly excised vein segments were mounted into a pulsatile perfusion apparatus and exposed to arterial flow conditions (P = 115/75 mmHg and Q = 110 ml min-1) for 2 h. Dynamic measurements of intraluminal pressure and flow rate and vessel wall radial distension were acquired to accurately quantitate the incremental modulus of elasticity; hoop, axial and radial wall stresses; and fluid shearing forces within the vessel. Identical measurements were performed on canine carotid arteries (CCA) to serve as a comparison. Under arterial conditions, IJV segments demonstrated a significant elevation (p less than 0.05) over the CCA in the incremental elasticity modulus, along with a corresponding elevation in hoop and axial wall stresses. Additionally the average wall shearing rate to which the IJV endothelial surface was exposed was a factor of six less than that observed in the CCA. These results are discussed in relationship to the clinical situation of vein graft adaptation to arterial hemodynamics.     

椎体静脉稀疏区注入骨水泥对PVP术中骨水泥渗漏的影响

目的:探讨椎体静脉稀疏区注入骨水泥对骨质疏松椎体压缩性骨折患者行经皮穿刺椎体成形术(percutaneous vertebroplasty,PVP)术中骨水泥渗漏的影响。方法:选择西安交通大学第二附属医院2014年1月至2018年6月收治的61例骨质疏松椎体压缩性骨折患者,根据骨水泥注入区域的不同,将所有患者分为A组(30例)及B组(31例),A组骨水泥注入区域为椎体静脉密集区(椎体中1/3平面处),B组骨水泥注入区域为椎体静脉稀疏区(椎体上1/3及下1/3平面处),对比两组的骨水泥渗漏率,术前、术后6个月时的视觉模拟评分(Visual analogue scale,VAS),治疗中的骨水泥用量、椎体高度恢复率及cobb角恢复度数。结果:B组的骨水泥渗漏率及骨水泥用量均明显低于A组(P0.05)。两组的VAS评分、椎体高度恢复率、cobb角恢复情况对比差异无统计学意义(P0.05)。结论:与椎体静脉密集区相比,在椎体静脉稀疏区注入骨水泥可显著降低骨质疏松椎体压缩性骨折患者PVP术中骨水泥渗漏率,椎体静脉稀疏区可作为PVP术中骨水泥注射的一个相对安全区域。     

Effect of Externally Applied Pressure on Femoral Vein Blood Flow

The effect of incremental increases in external pressure, applied to the leg, on blood volume flow in the femoral vein was studied in dogs. Clinical investigation of external pressure increases was also carried out on nine patients undergoing surgery for varicose veins. An external pressure between 5 and 15 mm. Hg caused a sustained increase in mean femoral vein flow both in a control and in the compressed limb. Above 15 mm. Hg external pressure flow decreased in the compressed limb but was maintained at an increased level in the control limb.If external compression is to be used to prevent and treat deep vein thrombosis its application must be carefully controlled.     

Altered temporal characteristics of the rectoanal inhibitory reflex in patients with abdominal distension

The rectoanal inhibitory reflex (RAIR) is important in gas and stool evacuation. We examined RAIR features in patients with chronic constipation who exhibited bloating with and without abdominal distension, to determine whether alterations in RAIR may be a factor in the pathogenesis of abdominal distension. Seventy-five female patients with chronic constipation with or without abdominal distension were included in the study. The presence or absence of abdominal distension was assessed according to the Rome II questionnaire. All patients underwent both RAIR and rectal sensitivity testing, and specific RAIR parameters were analyzed. Patients were divided into two groups: abdominal bloating with distension (D, n = 55) and abdominal bloating without distension (ND, n = 20). D had a longer time to the onset of anal sphincter inhibition (latency of inhibition) (P = 0.03) compared with ND. In logistic regression analysis, a combination of age, latency of inhibition and the time measured from onset of inhibition to the point of maximum inhibition predicted abdominal distension (P = 0.002). There were no differences between groups for the time from point of maximum inhibition to recovery and for the percentage of internal anal sphincter relaxation. This is the first study to examine the role of RAIR in patients with abdominal distension. Female patients with constipation and abdominal distension exhibited differences in the temporal characteristics of, but not in the degree of, anal sphincter relaxation compared with patients without distension. Since this study was uncontrolled, further studies are necessary to determine the contribution of altered anorectal reflexes to abdominal distension.     

Characteristics of distension-induced release of immunoreactive atrial natriuretic peptide in isolated perfused rabbit atria

Atrial pressure- or distension-induced release of atrial natriuretic peptide (ANP) has been considered as an important regulatory mechanism of ANP release in cardiac atria. A new technique to permit graded continuous atrial distension has been developed in an isolated perfused single rabbit atrium. Graded atrial distension was induced by changing the elevation of the outflow catheter tip. Intra-atrial volume expansion resulted in an increase in immunoreactive ANP release. The graded increase in atrial distension from 43.9 +/- 10.2 to 207.7 +/- 29.1 microliter resulted in 6.2-27.1-fold increases in volume-dependent immunoreactive ANP release. A rise in immunoreactive ANP release induced by increasing atrial distension did not occur in the state of atrial distension but occurred only after return to the reduced distension. However, in the case of atrial distension with pacing, an increase in immunoreactive ANP release was observed during atrial distension with pacing and after return to the basal level. The present study shows that the new technique is applicable to the study of the 'stretch-secretion coupling' mechanism of ANP release in vitro, and that the more important factor involved in the release of immunoreactive ANP induced by atrial distension may be the atrial reduction to basal level after distension rather than the stretch itself.     

Graduated compression and its relation to venous refilling time.

Graduated compression is important in improving venous function, but the pressure profiles of different brands of stockings in situ and effects on a direct measure of venous function have not been investigated. The pressure profiles of 15 different types of below knee compression stockings were established with a medical stocking tester in 13 healthy volunteers. Analysis of variance was performed for each stocking separately, considering the factors of size of stocking, site of measurement, and their interaction. The criteria used to define satisfactory function were that the stockings should have a significant linear trend with site--that is, graduation--and no other significant effects. Only five types of stockings met these standards. Venous function was then assessed by photoplethysmography in 19 patients with defined venous abnormalities. For each patient the effect on venous refilling time of three satisfactory and three unsatisfactory stockings was assessed. The three satisfactory stockings gave refilling times that were not significantly different from normal in patients with both superficial and deep vein incompetence, while refilling times with the three unsatisfactory stockings remained significantly below normal in all patients with deep vein incompetence; one stocking had no significant effect on refilling times in either group. Functional testing of compression hosiery should form part of future British Standards specifications.