Doppler flow velocimetry of the splenic artery in the human fetus: is it a marker of chronic hypoxia?

OBJECTIVE

The aim of this investigation was to describe splenic artery flow velocity waveforms in the appropriate- and small-for-gestational-age human fetus.

STUDY DESIGN

Splenic artery flow velocity waveforms were prospectively obtained from 95 appropriate- and 15 small-for-gestational-age fetuses with pulsed Doppler ultrasonography. The resistance index was used to quantify the Doppler waveform.

RESULTS

A second-degree polynomial model expressed the changes of the resistance index in appropriate-for-gestational-age fetuses with advancing gestation (y = 0.057x [Weeks] - 0.001x2, r = 0.53, p < 0.001). In 14 of 15 (93%) small-for-gestational-age fetuses the splenic artery resistance index was below the mean for gestational age. In five of 15 (33%) small-for-gestational-age fetuses the resistance index of the splenic artery was < 2 SEMs. A trend toward a higher hematocrit was noted in the five fetuses with splenic artery resistance index values < 2 SEMs (50.2%) compared with other small-for-gestational-age fetuses (43.0%).

CONCLUSION

Our results suggest that some small-for-gestational-age fetuses have decreased resistance at the level of the splenic artery. We postulate that the increased erythropoietin level, stimulated by hypoxia, results in decreased resistance at the level of the splenic artery in small-for-gestational-age fetuses. Finally, management of the small-for-gestational-age fetus may be aided by the study of the splenic artery waveforms.

Hemodynamic study of splenic artery aneurysm in portal hypertension

In our ongoing studies on the hemodynamics of splenic artery aneurysms (SAA) in portal hypertension, 32 patients with portal hypertension were examined by duplex sonography and angiography. Four out of 32 (12.5%) had SAA, and SAA(+) and SAA(-) groups were formed. On duplex sonography, splenic venous blood flow in the SAA(+) group (1058 +/- 211 ml/min) increased more than in the SAA(-) group (423 +/- 173 ml/min, p < 0.01), but there was no significant difference in portal venous flow. On angiography, there were significant differences in the diameters of the splenic arteries between the SAA(+) group (7.5 +/- 0.5 mm) and the SAA(-) group (5.6 +/- 1.0 mm, p < 0.01). All patients (100%) in the SAA(+) group had prominent portosystemic shunts, while 8 out of 28 (28.6%) in the SAA(-) group had these shunts (p < 0.05). Thus, there seems to be a splenic hyperkinetic state in patients with SAA and portal hypertension, a finding which may closely relate to the pathogenesis of SAA.

[Evolutive aneurysms in type IV Ehlers-Danlos' syndrome]

Ehlers-Danlos syndrome is one of the most frequent hereditary connective tissue diseases. Type 4 or Sack-Barabas syndrome differs by the seventy of arterial complications. The authors report a case of severely progressive aneurysms since thrombosis of the aneurysm of the left hepatic artery, splenic artery, and small aneurysms of the lower pancreatic artery and rapid development of severe ectasia of the coeliac trunk and the commun hepatic artery all occurred over a period of three months.

Effects of splenectomy and splenic artery ligation on the portal pressure in portal hypertensive rats

Immediate, short-, and long-term effects of splenectomy and splenic artery ligation on the portal pressure were studied in animal models experimentally created by partial portal vein ligation. The portal pressure of these animals would usually elevate immediately after partial ligation of the portal vein from a normal level of 6.0 +/- 0.5 to 14.8 +/- 1.3 mm Hg (P < 0.005), which could be maintained at least for 6 months. The portal pressure measured at 2 weeks, 4 weeks, and 6 months after portal vein ligation was 14.0 +/- 2.7, 15.2 +/- 2.7, and 12.7 +/- 2.0 mm Hg, respectively (P < 0.005, as compared with the normal). When splenectomy was performed on these animals at 2 weeks after partial portal vein ligation, the pressure dropped immediately but only transiently from 14.0 +/- 2.7 to 11.0 +/- 3.0 mm Hg, and bounced back to the presplenectomy level in 20 sec. After an additional 2 weeks, the portal pressure in these splenectomized rats was usually at 15.2 +/- 4.2 mm Hg, which was indistinguishable from that of rats whose portal vein was ligated but the spleen was not removed. Six months after splenectomy, however, the portal hypertensive rats had a portal pressure of 17.1 +/- 6.4 mm Hg, which was significantly higher than that of the controls. Splenic artery ligation, on the other hand, did not result in any immediate decrease in portal pressure (14.0 +/- 2.7 mm Hg vs 14.6 +/- 1.4 mm Hg; P > 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Splenic artery stump back pressure

Splenic arterial collateral hemodynamics were measured during splenic artery occlusion in 15 patients who had splenic to left renal artery bypass. The mean splenic artery stump back pressure during proximal splenic artery clamping was 48.0 +/- 9.8 mmHg (mean +/- ISD) and the mean collateral splenic perfusion pressure was 34.3 +/- 9.4 mmHg. The lowest measured back pressure was 39 mmHg and the lowest perfusion pressure was 30 mmHg. There were no spleen complications after operation. These measurements establish a normal range for collateral splenic perfusion pressure. These results may be helpful in clinical decisions about the adequacy of splenic circulation in operations that require division of the splenic artery or the short gastric arteries when there is celiac axis or splenic artery occlusive disease.

[The splenic steal syndrome and the gastroduodenal steal syndrome in patients before and after liver transplantation]

The study describes new pathologic entities, the splenohepatic steal-syndrome and the gastroduodenal steal-syndrome, which could be demonstrated by angiography in 17 patients before and after liver transplantation. After the first observation of a splenohepatic steal-syndrome in a patient with unexplained elevation of hepatic enzymes after liver transplantation, a prospective angiographic study was performed, including all liver transplant recipients and patients after liver transplantation with unexplained impaired liver function tests. 9 splenohepatic steal-syndromes could be demonstrated before and 7 after hepatic transplantation, one gastroduodenal steal was seen after liver transplantation. The different therapeutic modalities are discussed.

Pneumatic antishock garment decreases hemorrhage and mortality from splenic injury

The effect of the pneumatic antishock garment (PASG) in controlling hemorrhage and death from splenic injury was studied in a canine model. Twelve (two groups of 6) anesthetized dogs had their spleens crushed. Carotid blood pressure, carotid blood flow, splenic artery flow and abdominal aortic flow, as well as the death rate and blood loss, were measured. Group 1 dogs did not have PASG inflation, but group 2 dogs had PASG inflation to an intraperitoneal pressure of 60 mm Hg. All group 1 dogs died within 27 to 58 minutes, but all group 2 dogs survived. Blood loss was 9.4 +/- 1.4 mL/min in group 1 and 1.6 +/- 0.9 mL/min in group 2. In group 1 carotid artery blood pressure, carotid artery flow, splenic artery flow and abdominal aortic flow fell from 120 +/- 10 mm Hg, 284 +/- 12 mL/min, 194 +/- 18 mL/min and 285 +/- 10 mL/min respectively to 0 with death of the animals. By 2 hours in group 2 dogs the carotid artery blood pressure had dropped from 116 +/- 12 to 99 +/- 12 mm Hg, and over the same period carotid artery flow, splenic artery flow and abdominal aortic flow fell from 296 +/- 8 mL/min, 190 +/- 26 mL/min and 279 +/- 16 mL/min respectively to 259 +/- 14 mL/min, 39.0 +/- 6 mL/min and 45 +/- 11 mL/min respectively. Thus, inflation of the PASG maintained carotid artery blood pressure wh ile decreasing splenic, abdominal and aortic flow as well as splenic hemorrhage, with a decrease in the death rate, over a 2-hour period.

Hemodynamic changes in splenic blood flow during and after distal splenorenal shunt

The purpose of this study was to examine the hemodynamic changes of the spleen and the subsequent influence on the numbers of blood cells both during and 1 month after distal splenorenal shunt (DSRS) with splenopancreatic disconnection in 20 patients with portal hypertension. The intraoperative splenic blood flow, measured with an electromagnetic flowmeter, significantly increased after shunt insertion: the mean percentage increases within the splenic vein and artery were 60% (p less than 0.01) and 37% (p less than 0.05), respectively. The splenic venous blood flow, measured with a pulsed Doppler flowmeter, had not changed significantly 1 month postoperatively (676 +/- 501 to 540 +/- 306 ml/min). The WBC and platelet counts significantly (p less than 0.05 and p less than 0.01, respectively) increased 1 month postoperatively, whereas there was a small, but significant (p less than 0.05), decrease in RBC count. We concluded that splenic blood flow increases immediately after DSRS with splenopancreatic disconnection, but this increase may be only short term. The influence of the postoperative hemodynamic changes on blood cell count is uncertain.

Pancreatic transplant rejection: assessment with duplex US

The value of duplex ultrasonography (US) in the assessment of pancreatic transplants was studied in 22 patients over a 1 1/2-year period. Ninety-eight duplex US examinations were performed, and the Doppler arterial resistive indexes (RIs) correlated with clinical events after transplantation. The RI was 0.70 or less in the parenchymal vessels in all instances of normal transplant function and greater than 0.70 in seven of eight clinical episodes of rejection (87.5%). In all studies performed during these eight cases of rejection, the positive predictive value of an RI exceeding 0.70 was 100%. The negative predictive value of an RI of less than 0.70 in excluding rejection was 90%. High RI values were not found in isolated episodes of cyclosporine toxicity, pancreatitis, peripancreatic hemorrhage, or infection. Duplex US may prove to be more accurate in the diagnosis of rejection of pancreatic transplants versus renal transplants because the former cases have fewer causes of increased vascular impedance and diminished perfusion.

[Blood flow dynamics of the portal venous system in liver cirrhosis using pulse Doppler method]

Blood flow dynamics of the portal venous system including portal vein, splenic and superior mesenteric arteries, in thirty seven cases with liver cirrhosis and 32 controls were studied by means of the pulse doppler method. Maximum blood flow velocity of the main portal vein in liver cirrhosis was 0.21 m/sec in mean, significantly lower than in controls. Blood flow volume of the portal vein in liver cirrhosis was 18.9 ml/min.kg, which was a significant increase compared with that of controls. The cases of liver cirrhosis showed an increased blood flow volume of the splenic and superior mesenteric arteries, showing an increased pre-load to the spleen. In 5 cases, liver volume measured by computed tomography was not changed despite of an increase of the main portal venous flow volume. Three of these 5 cases were of more advanced liver cirrhosis with over 40 percent of ICG value. They bend to have higher portal venous velocity than the other cases with less advanced liver cirrhosis. No correlation of the splenic arterial flow volume and the spleen volume was thought to indicate after-load to the spleen as a factor of splenic enlargement.

Splanchnic hemodynamics in idiopathic portal hypertension: comparison with chronic persistent hepatitis

A comparative study of splanchnic hemodynamics was made in 12 patients with idiopathic portal hypertension and in eight patients with chronic persistent hepatitis, but without portal hypertension, who served as the control. Venous pressures were measured by portal and hepatic vein catheterizations, blood flow by the pulsed Doppler flowmeter, and organ volume by computed tomography. Splenic artery blood flow was 788 +/- 242 ml/min in idiopathic portal hypertension and about four times that in chronic persistent hepatitis (215 +/- 42 ml/min), whereas there was no difference in superior mesenteric artery blood flow between the former and the latter (408 +/- 142 vs. 389 +/- 32 ml/min). Spleen volume in idiopathic portal hypertension was six times that in chronic persistent hepatitis, and splenic artery blood flow showed a significant linear correlation with spleen volume in idiopathic portal hypertension (r = 0.71, p less than 0.02). The sum of splenic artery blood flow and superior mesenteric artery blood flow in idiopathic portal hypertension was 1195 +/- 294 ml/min, twice that in chronic persistent hepatitis (603 +/- 109 ml/min). Portal vascular resistance and intrahepatic portal vascular resistance were three times and four times those in chronic persistent hepatitis, respectively. These results indicate that both increased intrahepatic portal vascular resistance and increased splenic artery blood flow may play roles in the development of portal hypertension in idiopathic portal hypertension.

[Splenic vein occlusion due to pancreatic disease: regional portal hypertension from hemodynamic points of view]

The purpose of this study is to clarify the clinicopathophysiology of splenic vein occlusion due to pancreatic disease from hemodynamic points of view. We reviewed the angiographic findings and medical records of 82 patients who had pancreatitis, pancreatic cyst or pancreatic cancer in the pancreatic body and tail. According to the site of occlusion in 16 patients with complete splenic vein occlusion, this entity may be divided into two categories: Type A, an occlusion close to the spleen in which short-gastric system seems to be major collateral, and Type B, an occlusion distant from splenic hilum in which gastroepiploic system becomes prominent as collateral. As compared to 7 patients with incomplete splenic vein occlusion, gastric varices and splenomegaly were frequently observed with the patients having complete occlusion. Among these 16 patients, splenic arterial occlusion was superimposed in 3 patients with pancreatic cancer in whom gastric varices were not detected. Thus, clinical features of this entity must be carefully assessed according to the nature of the underlying disease. Based on these observations, three consecutive phases: Phase 1 Insiduous or latent phase, Phase 2 Collateral developing phase, Phase 3 Vanishing phase may be distinguished for splenic vein occlusion secondary to pancreatic disease.

Splenic artery and superior mesenteric artery blood flow: nonsurgical Doppler US measurement in healthy subjects and patients with chronic liver disease

The accuracy of the duplex Doppler ultrasound system in the measurement of blood flow in the splenic artery and the superior mesenteric artery was evaluated in seven anesthetized dogs by comparing blood flow recordings obtained simultaneously with the electromagnetic flowmeter, with those obtained with the combination of B-mode and M-mode scanning. Various flow rates were produced by the infusion of dopamine. Splenic artery blood flow and superior mesenteric artery blood flow measured with the duplex system exhibited significant correlations with corresponding values obtained with electromagnetic flow measurements (r = .93 and r = .93, respectively). Changes in splanchnic circulation with the progression of chronic liver disease in humans were then investigated with the use of the duplex system. Splenic artery blood flow and superior mesenteric artery blood flow were significantly increased in patients with cirrhosis compared with patients with chronic hepatitis and healthy subjects. These results indicate that a hyperdynamic circulatory state may develop in the splanchnic circulation of the intestine and spleen in cirrhotic patients.

Splenic conservation and the management of splenic artery aneurysm

We report two patients with splenic artery aneurysm diagnosed by CT, treated by proximal and distal ligation of the splenic artery and followed for two years by CT to assess splenic size and pitted erythrocyte counting to assess function. Literature review shows that excision of the aneurysm and splenectomy is usual but with growing regard for conservation of splenic tissue we suggest that proximal and distal ligation of the artery is a preferable alternative as shown by splenic function tests in these patients.

Hemodynamics of splenic artery aneurysm

Blood flow volume of the portal venous system of 3 patients with splenic artery aneurysm, an uncommon disease, was measured using an ultrasonic duplex system. A huge increase in splenic blood flow volume was found in each case. A large portasystemic shunt through which the portal blood flowed hepatofugally was present in 2 cases. We suspect the shunt is partially responsible for an increase in splenic blood flow volume, which would lead to the formation of splenic artery aneurysm together with portal hypertension.

Measurement of blood flow by ultrasound: accuracy and sources of error

Doppler ultrasound has now developed to the point where the rate of flow of blood in a given vessel can be measured with appropriate instrumentation. The theoretical basis of Doppler flow measurement is reviewed in this paper, with particular emphasis on the potential and actual sources of error. Three distinct approaches are identified, and the strengths and weaknesses of each discussed. The separate errors involved in estimating the vessel cross-sectional area, the angle of approach, and the Doppler shift are analyzed, together with the question of the uniformity of scattering from the blood. In vivo and in vitro tests of the accuracy obtained using a number of Doppler flow measuring instruments are then reviewed. It is concluded that the Doppler methods are capable of good absolute accuracy when suitably designed equipment is used in appropriate situations, with systematic errors of 6% of less. There are, however, considerable random errors, attributable primarily to errors in measuring the cross-sectional area and the angle of approach. Repeating the measurement of flow several times and averaging the results can reduce these random errors to an acceptable level.

[Measurement of the pancreatic blood supply before and after duct occlusion]

Blood flow measurements in the pancreas were performed in 12 pigs in situ, after the splenectomy, and then after the occlusion of the pancreatic duct by means of prolamin as well during a relaparotomy after 6 weeks. No change was pointed out immediately after the occlusion in face of the state following the splenectomy. The flow in the splenic artery was reduced significantly (p less than or equal to 0.0001) by 62% after 6 weeks.

Rheological properties of erythrocytes in heterozygous and homozygous beta thalassaemia

The rheological properties of erythrocytes were studied in 12 heterozygous and nine homozygous beta thalassaemia patients, using filtration of erythrocytes through polycarbonate sieves with a pore diameter of 5 micron and viscosity measurements of erythrocyte and ghost suspensions. Erythrocyte deformability of all patients was decreased. In the heterozygous patients moderately diminished flexibility of cells was due to microcytosis of erythrocytes. Rigidity of erythrocytes in homozygous patients was due to altered cell shape, diminished fluidity of haemoglobin, and in splenectomized patients to the presence of inclusion bodies. Membrane flexibility of erythrocytes remained unaltered. We suggest that the decreased fluidity of haemoglobin as well as the presence of inclusion bodies result from the excess of alpha chains in erythrocytes of homozygous patients. The haemoglobin fluidity of erythrocytes of one patient with thalassaemia intermedia was unchanged. The flexibility of these cells was only moderately altered. In four patients who needed transfusions every 1--4 weeks deformability of transfused erythrocytes was likewise decreased when compared to controls. Erythrocyte suspensions obtained from the splenic artery and vein during splenectomy showed decreased flexibility of transfused cells after their passage through the spleen.

Hemodynamic and morphologic evaluation of the spleen after splenic vein ligation in the dog

The splenic vein was ligated in ten dogs in order to evaluate the time course of changes in splenic size and to relate them to splenic arterial flow, splenic pressure and development of venous collaterals. Following ligation of the splenic vein, splenic size and venous pressure immediately rose in all dogs. Arterial flow to the spleen simultaneously fell in roughly inverse proportion to the elevation of venous pressure. During the following weeks, the splenic parenchymal pressure decreased to basline levels in all but one dog, as collateral veins developed through the gastric venous network to the portal vein. Splenic size gradually decreased toward normal in eight of the ten dogs. At the time of sacrifice, 8-16 weeks after splenic vein ligation, pathologic examination demonstrated fibrosis from healed infarction. Recent hemorrhage, indicating persistence of the congestive process, we also present, although difficult to explain in view of normal splenic parenchymal pressure.

Renal revascularization by splenic artery implantation in the dog

36 mongrels were subjected to splenic artery implantation into the left kidney. A stenosis of the left renal artery was created in 33 of the dogs. The revascularization process from the implanted artery was studied by angiography in vivo and ex vivo, by histological examination and by blood flow measurements. After creation of the stenosis and eventual occlusion of the left renal artery, newly formed intrarenal vessels could be demonstrated next to the implanted artery. These vessels formed communications between the splenic and intrarenal arteries. The experimental animals survived contralateral nephrectomy and ligature of the ipsilateral renal artery with a slight or moderate elevation of the serum creatinine level, provided that a slowly progressing stenosis of the renal artery was created.

Contrasting hemodynamic patterns of portal hypertension

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Vascular responses of the spleen to rapid haemorrhage in the anaesthetized cat

1. Splenic blood flow, splenic weight and arterial pressure were recorded in cats anaesthetized with sodium pentobarbitone. The mechanisms of the splenic contraction and vasoconstriction which followed rapid haemorrhage were investigated.2. When splenic arterial pressure was decreased progressively by mechanical occlusion of the coeliac artery, the decrease in splenic blood flow was proportional to the decrease in pressure; splenic weight did not change.3. After denervation of the spleen and adrenalectomy, haemorrhage resulted in a decrease in splenic flow which was similar to but slower than that in the innervated spleen; there was no splenic contraction. After splenic denervation, adrenalectomy and nephrectomy, haemorrhage caused a smaller decrease in flow but this response was still greater than that expected as a consequence of the reduced arterial pressure.4. Infusions of small doses of angiotensin caused splenic vasoconstriction with little change in splenic weight. Larger doses reduced both flow and weight.5. The splenic flow and weight responses to stimulation of the sympathetic nerves remained unimpaired when splenic blood flow was substantially reduced for 1-2 hr by haemorrhage.6. It is concluded that after a rapid haemorrhage, the splenic contraction is due only to activity of the splenic nerves and the adrenal medullae. The decrease in splenic flow is due to the reduction in arterial pressure, activity of the splenic nerves and the adrenal medullae, and the actions of angiotensin and some unidentified vasoconstrictor substance.