Superior Vena Cava Pressure Research Articles

Continuous retrograde cerebral perfusion for protection of the brain during aortic arch surgery.

Hypothermic circulatory arrest and selective cerebral perfusion for aortic arch surgery have been reported, but these procedures are of limited duration, require hazardous and complicated techniques and can cause clamp injury. Continuous retrograde cerebral perfusion (CRCP) is a new and simple technique for the protection of the brain during hypothermic circulatory arrest. We applied CRCP in 26 patients who underwent aortic arch surgery. Continuous retrograde cerebral perfusion was performed with a mean blood flow of 383 +/- 176, range 120-800, ml/min. The mean duration of CRCP was 63 +/- 15, range 32-92, min with the superior vena cava pressure at 15-42 mm Hg. No neurologic deficit was observed in 20 patients (90%) and only minor deficits in 2 out of the 22 cases without severe postoperative complications, allowing evaluation of the effectiveness of CRCP. Four patients had other severe complications, and the effectiveness of the method could not be evaluated. Continuous retrograde cerebral perfusion can be an excellent and safe technique which avoids clamp injury during aortic arch surgery.

The effect of the prone position on venous pressure and blood loss during lumbar laminectomy

Study Objective: To determine the effects of three different prone support systems (Andrews spinal surgery frame, Cloward surgical saddle, and longitudinal bolsters) on inferior vena cava (IVC) and superior vena cava (SVC) pressures; the validity of measuring central venous pressure (CVP) for the determination of ideal positioning of the patient; and the relationship among frame type, blood loss, and hemodynamic measurements. Design: Prospective, randomized study of the hemodynamic effects of the prone position. Setting: Inpatient surgery at a university hospital (regional spinal cord injury treatment center). Patients: Eighteen patients free of significant coexisting disease (ASA physical status I and II) undergoing elective lumbar Laminectomy. Interventions: Patients were assigned to one of three support frames and measurement of SVC pressure, IVC pressure, and mean arterial pressures (MAP) were obtained supine, prone, and after repositioning. These pressures and measured blood loss were obtained every 15 minutes during the surgical Laminectomy portion of the procedure. Measurements and Main Results: Patients positioned on the Andrews frame had decreased mean SVC and IVC pressures from 8.7 mmHg and 8.4 mmHg in the supine position to 3.3 mmHg and 1.8 mmHg in the prone position, respectively ( p < 0.001). Prone Position CVP also was significantly lower in the Andrews group compared with that in the other two groups ( p < 0.001). Repositioning efforts did not significantly decrease CVP. Blood loss was higher in the Cloward group (1,150 ± 989 ml) than in the Andrews (245 ± 283 ml) and bolsters (262 ± 188 ml) groups ( p < 0.02). Conclusions: Increased blood loss was not associated with increased SVC or IVC pressure, nor was there any significant correlation between any demographic or hemodynamic variable and blood loss. There was no evidence that CVP is useful in determining the ideal prone position in patients undergoing lumbar Laminectomy.

Accuracy of central venous pressure monitoring in the intraabdominal inferior vena cava: A canine study

To test the hypotheses that in multiple pathophysiologic settings (1) end-expiratory central venous pressure measurements in the intraabdominal inferior vena cava accurately reflect those in the superior vena cava and (2) mean central venous pressure monitoring is as reliable in the inferior vena cava as it is in the superior vena cava. Simultaneous inferior vena caval and superior vena caval pressures were measured during five ventilatory phases: apnea, end-expiratory mechanical ventilation, maximal inspiratory mechanical ventilation, end-expiratory spontaneous ventilation, and maximal inspiratory spontaneous ventilation. Measurements were repeated after progressive intravascular volume depletion. Eight puppies. Simultaneous inferior vena caval and superior vena caval end-expiratory pressures did not differ significantly (mean differences 0 to 0.1 mm Hg) and the limits of agreement of these measurements were within 2 mm Hg. Differences between mean maximal inspiratory pressures in the inferior vena cava and superior vena cava during mechanical and spontaneous ventilation were -0.7 and 3.6 mm Hg, respectively (p less than 0.01), and the limits of agreement extended beyond 2 mm Hg. Furthermore, mean maximal inspiratory pressures in the superior vena cava differed from end-expiratory pressures in the superior vena cava (1.1 and -3.6 mm Hg, p less than 0.01), whereas those in the inferior vena cava did not differ from end-expiratory superior vena caval pressures. Under the experimental conditions studied (1) end-expiratory intraabdominal inferior vena caval pressures accurately reflected end-expiratory superior vena caval pressures and (2) mean central venous pressure monitoring was as reliable in the inferior vena cava as in the superior vena cava.

CONTINUOUS RETROGRADE CEREBRAL PERFUSION DURING PROFOUND HYPOTHERMIC CIRCULATORY ARREST AT OPERATION FOR STANFORD TYPE A DISSECTING ANEURYSM

Three patients with chronic Stanford type A dissecting aneurysm were successfully operated upon using continuous retrograde cerebral perfusion (CRCP) during profound hypothermic circulatory arrest. Following profound hypothermic (14-15°C) circulatory arrest for 30-40 minutes, CRCP was started with a flow rate of 120-550ml/min to maintain a superior vena caval pressure of 15-20 mmHg. The circulatory arrest time was 56-101 minutes. The longer retrograde cerebral perfusion time induced prolonged wakefullness, but no serious neurological complications were encountered. In conclusion, CRCP is useful for cerebral protection during profound hypothermic circulatory arrest.

Effect of superior vena caval hypertension on alloxan-induced lung injury in dogs

To investigate how fast and to what extent superior vena caval hypertension (SVCH) increases lung water in acute increased-permeability state, we studied the time course of lung water accumulation for 3 h in anesthetized dogs under different treatments: 1) controls without intervention (5 dogs), 2) SVCH alone (5 dogs), 3) mild lung microvascular injury induced by low-dose alloxan (75 mg/kg) alone (5 dogs), and 4) SVCH coupled with low-dose alloxan (5 dogs). Neither low-dose alloxan alone nor SVCH alone [superior vena caval pressure (Psvc) = 11.0 +/- 3.1 (SD) mmHg] increased lung water significantly. The SVCH coupled with low-dose alloxan (Psvc = 11.3 +/- 2.7 mmHg) doubled extravascular lung thermal volume measured by the thermal-dye dilution technique within 1 h (5.3 +/- 0.9 ml/kg at base line and 10.9 +/- 4.7 ml/kg at 1 h), then remained unchanged (12.5 +/- 5.7 ml/kg at 3 h). This increase in lung water was confirmed by gravimetric method (5.69 +/- 1.71 g/g blood-free dry wt). We conclude that SVCH is one of the factors that may promote lung water accumulation in increased-permeability state.

Autoregulation of cardiac output by passive elastic characteristics of the vascular capacitance system.

After a change in cardiac output, the magnitude of potential blood volume redistribution was investigated in 10 dogs anesthetized with chloralose. All of the venous return was pumped into a reservoir, using servocontrolled pumps to maintain fixed superior and inferior vena cava pressures. The cardiac output was set at various levels by pumping from the reservoir into the right atrium. Changes in reservoir volume were assumed to reflect the changes in vascular blood volume. After measuring the control responses, cardiovascular reflexes were blocked with hexamethonium. Reducing the cardiac output, for example, from 110 to 80 ml/(min.kg) with reflexes intact, caused a 9.2-ml/kg transfer of blood from the dog to the reservoir. With reflexes blocked, the same change in cardiac output caused 6.8 ml/kg of the blood to be transferred. Under the control conditions, throughout the range of 50-140 ml/(min.kg), an increase or decrease of cardiac output of 1 ml/(min.kg) elicited a 0.304 +/- 0.086 (mean +/- SD) ml/kg change in dog blood volume; with reflexes blocked, the flow sensitivity was 0.239 +/- 0.062 ml/kg. Thus, only 21% of the total blood volume redistribution was attributable to active reflex responses. Deterioration of the preparation may have attenuated the magnitude of active reflex activity. Neither the systemic vascular compliance of 1.80 +/- 0.35 ml/mm Hg.kg nor the fraction of venous return from the superior vena cava of 26.5 +/- 4.6% was significantly changed by reflex blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Superior vena caval pressure elevation causes pleural effusion formation in sheep

Superior vena caval pressure elevation causes pleural effusion formation in sheep

Superior vena caval pressure elevation causes pleural effusion formation in sheep.

The effect of superior vena caval pressure (SVCP) elevation on the formation of pleural effusions (PE) was studied in sheep. Through a right thoracotomy, a Silastic cuff was placed around the superior vena cava. Catheters for monitoring SVCP and pulmonary artery pressure (PAP) were also placed. After a 1- to 3-wk recovery period, we measured the SVCP, PAP, cardiac output, and plasma protein concentration (Cp). We then elevated the SVCP to various levels from base line [5.3 +/- 2.6 (SD) mmHg] to 33 mmHg. The cardiac output, PAP, and Cp were remeasured 1-2 h and 24 h after SVCP elevation. At the end of the 24-h period, the animals were killed. The PE volume and pleural fluid protein concentration (Cpl) were measured, and the Cpl/Cp was calculated. PE generally did not occur until the SVCP was elevated above 15 mmHg. To study the effect of the thoracotomy on the subsequent pleural effusion, we studied six additional sheep in which we did not perform a thoracotomy. In these animals, the SVCP was elevated to between 5 and 28 mmHg for 24 h by use of a 16-Fr balloon catheter placed via a left external jugular vein and a right carotid-external jugular shunt. We found that the PE volume, for a given SVCP elevation, was similar to that present in sheep that received a thoracotomy. For all sheep the volume of PE was related to SVCP by the equation PE (ml) = 0.24e0.26SVCP, r = 0.85. In the sheep without a thoracotomy, Cpl/Cp rose with increasing volume of PE. Our data demonstrate that elevation of SVCP greater than 15 mmHg for 24 h results in the formation of PE. The rise in Cpl/Cp with PE volume suggests that filtration through the pleural vessels is not the major contributor to PE formation.

Embolized Air Collection in the Superior Vena Cava of ???Upright??? Sheep

In 34 studies on six "upright" anesthetized sheep central venous pressure from sites in the upper and lower superior vena cava (SVC) was recorded before, during, and after the injection into a neck vein of 1-ml increments of air every minute for 15 min. After the injection of air, the pressure recorded from the upper site increased significantly. This increase was the result of air collecting in the SVC with a consequent loss or partial loss of the SVC hydrostatic pressure difference. The time of onset and the duration of collection were not influenced by hyper- or hypovolemia nor by 1 kPa positive end-expiratory pressure. The readily identifiable change in the venous pressure in the upper SVC provided an earlier and more reliable warning of these small-volume air emboli than did a Doppler probe directed at the right side of the heart.

Elevation of superior vena caval pressure increases extravascular lung water after endotoxemia.

In many sheep Escherichia coli endotoxin results in pulmonary hypertension, increased microvascular permeability, pulmonary edema, and increased central venous pressure. Since lung lymph drains into the systemic veins, increases in venous pressure may impair lymph flow sufficiently to enhance the accumulation of extravascular fluid. We tested the hypothesis that, following endotoxin, elevating the venous pressure would increase extravascular fluid. Thirteen sheep were chronically instrumented with catheters to monitor left atrial pressure (LAP), pulmonary arterial pressure (PAP), and superior vena caval pressure (SVCP) as well as balloons to elevate LAP and SVCP. These sheep received 4 micrograms/kg endotoxin, and following the pulmonary hypertensive spike the left atrial balloon was inflated so that (PAP + LAP)/2 = colloid osmotic pressure. It was necessary to control PAP + LAP in this way to minimize the sheep-to-sheep differences in the pulmonary hypertension. We elevated the SVCP to 10 or 17 mmHg or allowed it to stay low (3.2 mmHg). After a 3-h period, we killed the sheep and removed the right lungs for determination of the extravascular fluid-to-blood-free dry weight ratio (EVF). Sheep with SVCP elevated to 10 or 17 mmHg had significant increases in EVF (5.2 +/- 0.1 and 5.6 +/- 1.2) compared with the sheep in which we did not elevate SVCP (EVF = 4.5 +/- 0.4). These results indicate that sustained elevation in central venous pressure in patients contributes to the amount of pulmonary edema associated with endotoxemia.

Comparison of Flow Differences among Venous Cannulas

The efficiency of four methods of venous drainage during cardiopulmonary bypass was evaluated. Superior vena caval (SVC), inferior vena caval (IVC), right atrial (RA), and right ventricular (RV) pressures as well as RV blood flow were measured for cannulation with a single USCI 40F atrial cannula, a single Sarns 51F cavoatrial cannula, and double USCI 32F caval cannulas with and without caval tourniquets. Measurements for all cannulas were recorded in conditioned dogs during nor-mothermic cardiopulmonary bypass with the heart beating, with the heart fibrillated, and with the apex of the heart elevated in the circumflex position. Venous drainage using double caval cannulas with caval snares provided maximum decompression of the venous system (SVC pressure, − 3 ± 1.52 mm Hg [standard deviation]; IVC pressure, −1.67 ± 2.67 mm Hg to 0.4 ± 2.09 mm Hg). However, decompression of the right side of the heart with this method was the poorest (RA pressure, 5 ± 1.46 mm Hg to 9.60 ± 2.78 mm Hg; RV pressure, 5.67 ± 0.82 mm Hg to 12.5 ± 1.51 mm Hg; RV vent flow, 96 ± 4 ml/min to 370 ± 50 ml/min). The caval cannulas without tapes provided similar venous decompression but with better right-heart decompression (RA pressure, −0.71 ± 1.95 mm Hg to 0.60 ± 2.51 mm Hg; RV pressure, 2.13 ± 2.23 mm Hg to 11.6 ± 0.89 mm Hg; RV vent flow, 29 ± 5 ml/min to 75 ± 4.5 ml/min). The USCI 40F atrial cannula provided less efficient decompression of the inferior vena cava (IVC pressure, 4.33 ± 1.96 mm Hg to 7.17 ± 3.46 mm Hg). The Sarns 51F cavoatrial cannula had the most efficient right-heart decompression (RA pressure, −11.6 ± 2.19 mm Hg to −4.1 ± 1.7 mm Hg; RV pressure, −2.5 ± 1.57 mm Hg to 4.6 ± 1.2 mm Hg; RV vent flow, 0 ± 7 ml/min to 26 ± 9 ml/min). Placing the heart in the circumflex position adversely affected right heart decompression in all techniques except single cannulation with the 51F cavoatrial cannula. Likewise, venous decompression was affected adversely in all techniques except double cannulation with caval snares. With the single 40F atrial cannula, SVC and IVC pressures were both elevated. Only the SVC pressure was affected when the cavoatrial cannula was used.

A Starling resistor regulates cerebral venous outflow in dogs.

This investigation was undertaken to determine whether a Starling resistor or venous waterfall effect exists between the sagittal sinus and the cerebral veins such that increases in sagittal sinus pressure (Pss) do not abolish cerebral venous outflow and to examine two possible contributions of extracranial venous valves in regulating outflow. Anesthetized dogs were subjected to positive end-expiratory pressure (PEEP) before and after intracranial pressure (Pic) was elevated by inflation of an epidural balloon. PEEP raised Pss equally in all animals, but Pic and cerebral venous pressure (Pcv) increased less in the presence of intracranial hypertension. When Pss was low, passage of a catheter in the cerebral vein in and out of the sagittal sinus demonstrated an abrupt drop in pressure as the sinus was entered. When Pss was raised and lowered independently of superior vena caval pressure (Psvc) the changes in Pic and Pcv were less when Pss was decreased than when it was increased. Sustained increases and decreases in Psvc caused increases and decreases in Pcv, Pic, Pss, and external jugular venous pressure (Pejv) regardless of whether external jugular venous valves were present or absent. We conclude that a Starling resistor between the sagittal sinus and the cerebral veins regulates cerebral venous outflow when Pss is increased by PEEP and other maneuvers that raise Psvc. The waterfall maintains Pcv and Pic at normal levels when Psvc and Pss are reduced. Extracranial venous valves are not essential to this mechanism.

Communicating hydrocephalus secondary to venous complications following intraatrial baffle operation (mustard procedure) for d-Transposition of the great arteries

A 39-month-old male had macrocephaly and communicating hydrocephalus secondary to superior vena cava (SVC) obstruction which was a postoperative complication of an intraatrial baffle operation (Mustard procedure) performed at age 10 months. Computerized tomography revealed progressive hydrocephalus. Cardiac catheterization showed an SVC pressure of 24 mm Hg. IVC and systemic vein atrium pressures were 5 mm Hg. Cineangiograms showed huge azygos collaterals from SVC to IVC. The operation was revised using a Dacron baffle instead of the original pericardial baffle. Nine months postoperatively, the head circumference was 55.0 cm and there was no clinical evidence of SVC obstruction.

Hemodynamic effects of hydralazine in infants with a large ventricular septal defect.

To evaluate the effects of acute afterload reduction, hydralazine, 0.2 mg/kg, was administered at cardiac catheterization to seven infants who had a large ventricular septal defect (VSD). The infants were 2.5 - 11 months old (mean 5.1 months). Before and 5, 15, 25 and 35 minutes after hydralazine, aortic, pulmonary capillary wedge, pulmonary artery, right atrial and superior vena caval pressures and saturations, heart rate and oxygen consumption were measured. Hemodynamic effects were noted after 5 minutes but were most pronounced 35 minutes after hydralazine. Prehydralazine baseline data were therefore compared with values 35 minutes after hydralazine. Pulmonary flow did not changes, but systemic flow increased significantly (4.5 +/- 0.2 to 6.7 +/- 0.5 liters/min/m2 [mean +/- SEM], p less than 0.001). The pulmonary-to-systemic flow ratio decreased by 32% (3.4 +/- 0.4 to 2.3 +/- 0.2, p less than 0.001) and the absolute left-to-right shunt decreased by 24% (10.8 +/- 1.3 to 8.2 +/- 1.2 liters/min/m2, p less than 0.01). Hydralazine caused a significant decrease in systemic resistance (13.9 +/- 0.7 to 9.5 +/- 0.7 U, p less than 0.001). Pulmonary resistance, aortic, pulmonary artery and pulmonary capillary wedge pressures, heart rate and oxygen consumption did not change after hydralazine. Right atrial pressure decreased slightly (4.0 +/- 0.6 to 2.4 +/- 0.6 mm Hg, p less than 0.05). In conclusion, hydralazine caused a significant increase in systemic blood flow and a significant decrease in both pulmonary-to-systemic flow ratio and absolute left-to-right shunt in seven infants with a large VSD. These effects appear to be related to the decrease in systemic resistance that occurred with hydralazine. Although limited to the acute setting, these findings suggest that hydralazine may be beneficial in the management of infants with a large VSD.

The role of cava-pulmonary (Glenn) anastomosis in the palliative treatment of congenital heart disease

The value of the cava-pulmonary anastomosis (Glenn procedure) was assessed by reviewing the entire experience with this procedure in 83 children at The Hospital for Sick Children, Toronto, from 1961 to 1980. The over-all operative mortality rate was 9.6%, but only 2% in the second half of the series. The average follow-up is 9.4 years per patient. The late mortality rate has been 20%. By actuarial analysis, 84% of survivors were alive 9 years after operation; 54% had adequate palliation and 46% had required further operation. Long-term palliation was significantly better when the anastomosis was performed after 5 years of age. A previous arterial pulmonary artery shunt had no effect on either patient or shunt survival. Patients with tricuspid atresia had a better long-term survival rate than, but similar shunt survival to, those children with transposition, single ventricle, or miscellaneous cardiac anomalies. Angiography in 36 survivors showed patent shunts in 35 and no arteriovenous fistulas. Clinical status was not related to superior vena caval pressure or angiographic findings, indicating that Glenn shunt failure is a functional problem. The procedure is most useful for patients over 5 years of age who have complex heart disease not amenable to total repair. It is also on appropriate initial procedure in young patients over 18 months of age for whom direct atrium--pulmonary artery anastomosis is proposed as the future definitive treatment.

Mechanism by which positive end-expiratory pressure increases cerebrospinal fluid pressure in dogs.

We investigated possible mechanisms by which positive end-expiratory pressure (PEEP) increased cerebrospinal fluid pressure (PCSF) in anesthetized mechanically ventilated dogs. In part I of the study, PEEP was applied in 5 cmH2O increments each lasting 1-2 min, before and after a snare separated the spinal from the cerebral subarachnoid space in each animal. Next, with the spinal cord still ligated, the dogs were ventilated without PEEP while superior vena cava pressure (PSVC) was raised in 5 cmH2O increments by means of a fluid reservoir connected with the superior vena cava. Cerebrospinal fluid pressure in the cisterna magna increased immediately and in parallel with PEEP before and after the spinal subarachnoid space was occluded and also increased when PSVC was raised independently; in all circumstances the increase in PCSF correlated closely with PSVC (r = 0.926). In part II of the study, arterial blood gases were drawn before and after PEEP was applied in the same increments and for the same duration as in part I. Cerebrospinal fluid pressure measured with a hollow skull screw again rose in parallel with PEEP, whereas arterial carbon dioxide tension rose only slightly at 60 s. In part III of the study, mean arterial pressure (Pa) was allowed to decrease with PEEP or was held constant by distal aortic obstruction and volume infusion. Cerebrospinal fluid pressure increased regardless of Pa, but the increase was greater when Pa was held constant than when it fell with PEEP. We conclude that PEEP increases PCSF primarily by increasing PSVC and decreasing cerebral venous outflow. This effect is augmented if cerebral arterial inflow is increased as well.

Identifikation der Dynamik des Blutdruckregelkreises beim Hund

In a previous paper we presented a simple dynamic model of the blood pressure control system in man based on measurements of the peripheral arterial blood pressure. Because data on the central venous, aortic and carotid pressure had not been available from the respective experiments in man. We repeated our investigations on mongrel dogs, anaesthetized by alpha-chloralose. The dogs were tied supine on a tilt table. For identification of the closed loop system binary test sequences were impressed into the dogs cardiovascular system in form of orthostatic stresses. The dogs were tilted head-up between 10° and 55° (With the sines of these angles beeing the real test quantity the amount of the amplitudes related to 30° had to be equal). Table position, aortic pressure, carotid pressure, superior vena caval pressure and electrocardiogram were recorded continously. With the measured input-output data the parameter estimation of the blood pressure control system was done by using the method of recursive generalized-least squares.

Long-term effect of the superior vena cava—pulmonary artery anastomosis on pulmonary blood flow

The long-term effects of the superior vena cava-pulmonary artery anastomosis were evaluated in 15 patients a mean of 8.5 years postoperatively. There were eight patients with tricuspid atresia and seven with other complex anomalies. Ten patients underwent 133xenon ventilation scans and 99mtechnetium perfusion scans in the upright and suprine positions. Perfusion scans showed decreased perfusion of the right upper lobe which improved in the supine position. Shunt flow, measured by thermodilution in nine patients, was a mean of 1.7 L. per minute per square meter, with a mean superior vena caval pressure of 8 mm. Hg and a resistance of 3.0 units. Right and left pulmonary venous saturations were 94 and 96 percent, respectively, showing little intrapulmonary shunting. Venous collaterals were the major cause for shunt failure. Six patients underwent a left Blalock-Taussig shunt and division of venous collaterals a mean of 6 years after the Glenn shunt and are all doing well. The superior vena cava-pulmonary artery anastomosis did not result in progressive pulmonary deterioration in the patients studied. The staged treatment of tricuspid atresia by the Glenn shunt followed by a systemic-pulmonary artery shunt and ligation of venous collaterals gives prolonged effective palliation.

Right atrial partition and right ventricular exclusion: Another surgical approach for complex cyanotic congenital heart disease

A 5-year-old child with asplenia, situs inversus, single ventricle, common atrium, severe subvalvular pulmonary stenosis, 1-transposition of the great arteries, and absent inferior vena cava presented with severe limitation (resting arterial saturation 74 per cent). At operation, the systemic venous atrium was partitioned with a Dacron baffle, so that hepatic venous and coronary sinus blood was enabled to drain with the pulmonary venous blood into the single ventricle and aorta. The superior portion of this atrium was anastomosed to the divided main pulmonary artery, so that most of the systemic venous blood was allowed to flow directly to the lungs. Intraoperative hemodynamic studies revealed a pulmonary artery pressure of 12/9 mm. Hg and a superior vena caval flow that was 88 per cent of the ascending aortic blood flow. Follow-up catheterization studies revealed an intact partition, no anastomotic gradient, superior vena cava pressure of 20 mm. Hg, arterial saturation of 84 per cent, and excellent flow of contrast from superior vena cava to atrium to pulmonary artery. Exercise tolerance was markedly improved, and chronic fluid retention was not observed. This operation offers a new alternative for long-term palliation of complex lesions amenable to exclusion of the right ventricle, such as single or common ventricle with unreconstructable anomalies of the atrioventricular valves.

Hemodynamics of the interposition mesocaval shunt.

Eighty interposition mesocaval shunts, using a knitted Dacron large diameter prosthesis, have been performed during the past five and one-half years. Patients were evaluated from the standpoint of protection from recurrent esophageal hemorrhage, shunt patency, encephalopathy and cumulative survival analysis. In a selected group of patients, hemodynamic measurements were also obtained in the pre, intra, and postoperative periods. These included measurements of wedged hepatic vein pressure, superior mesentric venous blood flow, and residual superior mesenteric, hepatic sinusoidal and inferior vena cava pressures following the shunt procedure. Additionally, direct shunt flow measurements utilizing a square wave of electromagnetic flowmeter were also performed. Results indicate that the shunt patency is 95%; adequate decompression of the portal system was accomplished; recurrent variceal hemorrhage did not occur if the shunt remained patent; the incidence of encephalopathy was low (11%); and the operative mortality for the entire series was 9%. Continued perfusion of the liver was documented in 44% of patients and appears to be a function of the residual total portal resistance largely controlled by inferior vena caval pressure at the level of graft replacement. Life survivhat the interposition mesocaval shunt appears to be an effective technique for the control of variceal hemorrhage, has important hemodynamic advantages and can be applied to most patients for the control of variceal hemorrhage due to portal hypertension.