Duplex ultrasound (DU) is recognised as a valuable tool for the assessment of blood flow in many vascular territories. The application of this technique to the superior mesenteric artery (SMA) has increased rapidly throughout the last decade. The purpose of this review is to collate currently available information on the utility of SMA DU, both in terms of research and clinical practice. Research investigations have revealed low intra- and interobserver variability in the estimation of Doppler variables, while reliable evaluation of B-mode dimensions requires repeated measurements. SMA blood flow velocity has been found to be dependent upon changes in central haemodynamics and in peripheral resistance, which was documented in studies with hypotension, medication and post-prandially. Food intake induces mesenteric vasorelaxation reflected by a 10-fold increase in the diastolic velocity. This feature has been utilised in studies on mesenteric physiology, which confirmed parasympathetic activity during hypovolaemia, and showed that exercise increases splanchnic resistance and reduces its blood flow following a 50% reduction in the hepato-splenic and a 25% reduction in the mesenteric blood flow. Clinical studies have documented high sensitivity and specificity of DU in detection of disease in splanchnic arteries. Diastolic velocity was found to be the most accurate indicator of SMA stenosis, while an absent Doppler signal from a well visualised vessel has been found to be a reliable predictor of occlusion. The high predictive value of DU in the detection of mesenteric artery disease, together with its simplicity and non-invasiveness, suggests that DU should take precedence over arteriography in both clinical practice and laboratory investigations.

Central hypovolaemia induced by head-up tilt evokes a reduction in superior mesenteric artery resistance resulting in maintenance of regional blood flow. Mechanisms of importance for this response are not known, but a parasympathetic contribution could be expected. To evaluate this hypothesis, superior mesenteric artery blood flow and resistance were evaluated by duplex ultrasound in eight healthy volunteers during postprandial head-up tilt with and without cholinergic blockade. During supine rest, cholinergic blockade did not influence the postprandial reduction in peripheral mesenteric artery resistance as expressed by analogous elevations in the diastolic blood velocity (to 62 +/- 9 vs. 56 +/- 7 cm s-1 with placebo). Throughout the normotensive and hypotensive phases of head-up tilt, cholinergic blockade reduced mesenteric artery mean blood velocity by 39 and 42%, respectively, corresponding to volume flow reductions by 35 and 41% (0.62 +/- 0.10 vs. 0.96 +/- 0.13 L min-1 and 0.52 +/- 0.07 vs. 0.88 +/- 0.16 L min-1; P < 0.05). Also, during both phases of head-up tilt, cholinergic blockade increased mesenteric artery resistance as reflected in a reduction in the diastolic blood velocity by 41 and 56%, respectively (44 +/- 4 vs. 74 +/- 13 cm s-1 and 24 +/- 6 vs. 54 +/- 8 cm s-1). These results support a cholinergic contribution to the mesenteric artery vasorelaxing response to central hypovolaemia induced by head-up tilt.

The influence of muscarinic blockade on the superior mesenteric artery (SMA) response to head-up tilt (HUT) was assessed by Doppler ultrasound in eight healthy adults pretreated with i.v. glycopyrron. During supine rest, cholinergic blockade increased heart rate from 58 +/- 3 to 106 +/- 6 beats min-1 (mean +/- SE) and mean arterial pressure from 81 +/- 3 to 97 +/- 4 mmHg (P < 0.01) and it reduced the cardiac stroke volume from 89 +/- 6 to 59 +/- 7 ml (P < 0.01) with no significant effect on the SMA diameter and blood flow velocities. HUT provoked a further increase in heart rate to 134 +/- 5 beats min-1 (P < 0.01) and a reduction in stroke volume to 45 +/- 4 ml (P < 0.01). The early diastolic velocity increased from -51 +/- 4 to 6 +/- 8 cm s-1 during the normotensive stage of HUT and further to 21 +/- 9 cm s-1 during the hypotensive stage with a reduction in mean arterial pressure from 97 +/- 4 to 73 +/- 7 mmHg (P < 0.01) but, in contrast to control HUT (without cholinergic blockade), the end-diastolic velocity did not change significantly. Maintenance of blood velocity and diameter in spite of an increase in arterial pressure at rest indicates increased SMA impedance. Likewise, during hypovolaemia, a glycopyrron-induced inhibition in diastolic velocity supports an increase in SMA impedance. The results indicate cholinergic vasorelaxing influence on the superior mesenteric artery both at rest and during normotensive central hypovolaemia.

Exercise reduces splanchnic blood flow, but the mesenteric contribution to this response is uncertain. In nineteen humans, superior mesenteric and coeliac artery flows were determined by duplex ultrasonography during fasting and postprandial submaximal cycling and compared with the splanchnic blood flow as assessed by the Indocyanine Green dye‐elimination technique. Cycling increased arterial pressure, heart rate and cardiac output, while it reduced total vascular resistance. These responses were not altered in the postprandial state. During fasting, cycling increased mesenteric, coeliac and splanchnic resistances by 76, 165 and 126%, respectively, and it reduced corresponding blood flows by 32, 50 and 43% (by 0.18 ± 0.04, 0.42 ± 0.03 and 0.60 ± 0.04 l min−1). Postprandially, mesenteric and splanchnic vascular resistances decreased, thereby elevating regional blood flow, while the coeliac circulation was not influenced. Postprandial cycling did not influence the mesenteric resistance significantly, but its blood flow decreased by 22% (0.46 ± 0.28 l min−1). Coeliac and splanchnic resistance increased by 150 and 63%, respectively, and the corresponding regional blood flow decreased by 51 and 31% (0.49 ± 0.07 and 0.96 ± 0.28 l min−1). Splanchnic blood flow values assessed by duplex ultrasound and by dye‐elimination techniques were correlated (r= 0.70; P < 0.01). During submaximal exercise in humans, splanchnic resistance increases and blood flow is reduced following a 50% reduction in the hepato‐splenic and a 25% reduction in the mesenteric blood flow.

Purpose: To assess the predictive value of ultrasound duplex scanning in the detection of superior mesenteric artery (SMA) and celiac artery (CA) occlusive disease,Methods: Thirty-nine patients in whom mesenteric ischemia was suspected were examined with duplex scan and arteriography.Results: Duplex scan visualized both vessels in all examined patients. An absent Doppler signal from an adequately visualized SMA or CA was a pathognomonic sign for total occlusion of the arteries. Elevated diastolic velocities (peak diastolic velocity >70 cm/sec for SMA and >100 cm/sec for CA) were accurate predictors of arteriographically confirmed stenoses greater than or equal to 50%. Increased blood velocity was occasionally observed in a thyrotoxic patient with malabsorption-induced weight loss and abdominal pain but arteriographically-normal SMA. Further examinations of hyperthyroid patients showed systematic elevation of peak systolic velocity in the SMA greater than 300 cm/sec but normal diastolic velocities and resistivity indexes.Conclusion: Duplex ultrasound is a highly selective and specific method for detection of SMA and CA occlusive disease, The most accurate predictors of the disease were increased diastolic velocities, which in contrast to peak systolic velocity also correctly classified thyrotoxic patients, The method can be used before arteriographic evaluation as a screening examination of patients in whom mesenteric ischemia is suspected.

Superior mesenteric artery (SMA) blood flow and impedance were evaluated by duplex ultrasound during head-up tilt (HUT)-induced central hypovolaemia and hypotension in eight healthy volunteers. HUT induced a reduction in cardiac stroke volume from 88.8 +/- 6.3 to 64.7 +/- 6.3 ml (mean +/- SEM; P < 0.01) and an increase in thoracic electric impedance from 38.6 +/- 2.1 to 42.6 +/- 2.1 omega (P < 0.01) reflecting a reduced central blood volume. Maintained tilt provoked a 30% reduction in mean arterial pressure (from 87.1 +/- 3.3 to 63.4 +/- 3.6 mmHg: P < 0.01) and the appearance of presyncopal symptoms. During both the normotensive and the hypotensive phase of HUT, the SMA diameter (5.7 +/- 0.03 mm) and blood flow (514 +/- 75 ml min-1) did not change significantly, although the end-diastolic velocity increased from 9.7 +/- 4.8 to 39.7 +/- 4.0 cm s-1 (P < 0.01). The increase in diastolic velocity, despite a maintained or reduced arterial pressure, supports a reduction in the SMA impedance as it was reproduced during a meal test when a moderate reduction in mean arterial pressure (87 +/- 4 to 80 +/- 4 mm Hg; P = 0.04) was accompanied by a ninefold increase in the end-diastolic velocity (P < 0.01). The results indicate a reduction in the mesenteric vascular impedance to the extent that superior mesenteric artery blood flow is maintained during HUT-induced central hypovolaemia and hypotension.

Influence of stroke volume reduction and hypotension on the superior mesenteric artery (SMA) Doppler waveform was evaluated during head-up tilt-induced central hypovolemia in 11 healthy volunteers. During normotensive reduction in stroke volume, peak systolic velocity (pV), mean velocity, pulsatility and resistivity indices decreased, while diastolic velocities increased. During hypotension, a further decrease in pV was accompanied by maintained elevation of diastolic velocities and reduction in pulsatility and resistivity indices. Power of backscattered Doppler wave was elevated throughout the hypovolemia. Alterations in pV and pulsatility indices were closely related to changes in stroke volume, and a negative correlation was found between diastolic velocities and stroke volume. regression analysis showed no significant relation between variations in velocity parameters and blood pressure. Results of the study indicate that alterations in stroke volume induce consequential changes in the SMA Doppler waveform. These changes originate from both direct influence of stroke volume and/or pressure on blood flow velocity, and alterations in SMA peripheral resistance that follow variations in stroke volume. Presented interdependencies should be taken into consideration while studying mesenteric physiology with the use of Doppler technique and while interpreting the duplex results in patients suffering from diseases that may influence flow velocity and mimic or obscure Doppler effects of the SMA stenosis.

Clinical outcome and hemodynamic effects of unilateral mechanical ventricular support (UMVS) were evaluated in 19 patients with postcardiotomy heart failure refractory to conventional treatment. Adequate circulation with UMVS was maintained in about 75% of the patients. UMVS initiated circulatory stabilization in 5 of 6 patients with biventricular failure, in 2 of 3 patients with right ventricular failure, and in 7 of 10 patients with left ventricular failure. Eight (42%) patients were successfully weaned from UMVS and discharged from hospital. Six (32%) patients died despite a prolonged, stabilized circulation by UMVS. In 5 (26%) patients, the UMVS could not secure stable circulation. Application of the left UMVS induced increases in cardiac output and systemic blood pressure and a decrease in left atrial pressure without changes in pre- and afterload of the right ventricle. It is concluded that application of UMVS may induce adequate circulation in patients with postcardiotomy heart failure refractory to treatment with inotropes and intraaortic counterpulsation. The outcome of UMVS in left, right, and biventricular failure is acceptable. Thus, this treatment may be recommended for patients with postcardiotomy heart failure.

From 1984 to 1993, 1,053 patients were admitted with aortic aneurysm (AA) and 170 (15%) were not operated on. The most frequent reason for nonoperative management was presumed technical inoperability. Survivals for patients with thoracic, thoracoabdominal, and abdominal AA were comparable. No significant differences in survival for patients with dissecting and nondissecting AA were detected. In all, 132 patients (78%) died and 78 (59%) of them died of rupture. Mean time to rupture was 1,300 +/- 8 days. Cumulative 5-year hazard of rupture for the dissecting AA was twice that of the nondissecting (p < 0.001). Hazards of rupture for type A and B dissections were comparable. Diameter of 6 cm or greater was associated with a fivefold increase in cumulative hazard of rupture (p < 0.001). Diameter of AA, incidence of renal failure, and arterial hypertension were predictive of mortality, whereas the first two variables were predictive of rupture. In conclusion, because the majority of patients in all subgroups died of rupture, all patients should be recognized as candidates for surgical treatment. Present data justify aggressive approach to the patient with AA 6 cm or more in diameter and type A dissections. The results suggest that type B dissections may have a more favorable course if operated on, but a prospective, randomized study is necessary to confirm this observation. We believe that older patients and those with a small aneurysm may benefit from early, elective operation.

Le but de ce travail etait d'identifier les malades necessitant un sejour prolonge (plus de 48 heures) en unite de soins intensifs (USI) apres cure chirurgicale d'un anevrysme de l'aorte abdominale (AAA) et d'evaluer l'influence des complications peri-operatoires sur la survie et la qualite de vie a court et a long terme. Sur 553 malades operes d'un AAA, 51 (9 %) sont decedes au cours des 48 premieres heures. Parmi les 502 malades ayant survecu plus de 48 heures, 109 necessiterent un sejour en USI de plus de 48 heures, ce sejour etant inferieur a 48 heures chez 393 malades. La repartition des facteurs de risque pre-operatoires etait analogue dans les deux groupes

During a ten-year period 735 patients with abdominal aortic aneurysm were admitted of whom 656 patients were operated on. The perioperative mortality was 18%: 5% in cases electively operated on, 17% in acute not ruptured cases, and 37% in patients presenting with rupture. Age significantly affected perioperative (< 31 days) mortality-both considered alone and assessed together with other risk factors. Further analysis indicated that the perioperative mortality of octogenarians did not differ from the mortality of septuagenarians, who on the other hand experienced a perioperative mortality rate twice that of patients younger than seventy years. Survival beyond the perioperative period was adversely affected only by age and ischemic heart disease.

The aim of this study was to evaluate the interobserver variability during duplex ultrasonographic investigation of the SMA. Eleven healthy volunteers were examined twice under the same conditions by two independent observers. Three basic Doppler wave parameters were assessed for the SMA: pV, edV, and rT. The tD was recorded for SMA and abdominal aorta (AotD) with B-mode imaging. The interobserver variability was very low for all parameters: pV = 13.5 cm/s; edV = 3.4 cm/s; rT = 0.01 s; tD = 0.3 mm; AotD = 0.5 mm, with corresponding 95% confidence intervals as follows: pV = 19 cm/s; edV = 4.7 cm/s; rT = 0.015 s; tD = 0.4 mm; and AotD = 0.75 mm. Coefficients of variation also showed very low dispersion for results obtained. Under the appropriate standard conditions for duplex sonographic examination of the mesenteric artery, assessments of basic Doppler wave parameters do not differ significantly between independent investigators. Reliable evaluation of B-mode distances can be obtained by replication of measurements.

Thoracic impedance at 2.5 (TI2.5) and 100 kHz (TI100), central venous pressure (CVP), and body fluid balance were recorded together with rectal temperature and arterial haematocrit in 15 consecutive patients subjected to coronary artery bypass grafting. I.v. fluid and blood were administered in an excess of 3.18 (1.38-9.35) 1 during the operation. TI2.5 decreased from 51.7 (39.2-66.4) to 34.9 (21.1-45.7) ohm (P = 0.001), while TI100 decreased from 41.9 (31.4-55.0) to 30.3 (18.3-40.8) ohm (P = 0.002). CVP, 6 (3-11) mmHg [0.8 (0.4-1.5) kPa], was the same before and after surgery. Temperature decreased during cardiopulmonary bypass from 35.4 (34.1-36.6) to 26.7 (22.9-3 1.0)-degrees-C and haematocrit from 39 (34-46)% to a lowest value of 27 (23 32)% (P = 0.0001). A close linear correlation between TI and body fluid balance was observed (TI2.5: r = -0.96, TI100: r = -0.95, P = 0.0001). Corrections of TI for temperature and/or haematocrit improved the correlation between TI and fluid balance to 0.99 (TI2.5) and 0.98 (TI100). The data indicate that changes in thoracic impedance can be used to monitor body fluid balance during cardiac surgery.

From 1979-1988, 656 patients were operated for abdominal aortic aneurysm. The perioperative mortality was 18%. The mortalities for elective, symptomatic and ruptured aneurysms were 5%, 17% and 38% respectively. The overall five year survival rate was 58%. In 87% of the patients one or more risk factor was found. Survival was unaffected in patients with a single risk factor, whereas patients with two or more risk factors had lower five year survival. Postoperative organ failure increased the perioperative mortality and the five year survival in patients with multiorgan failure was 20%. In view of the fact that 56% of the patients are operated on as emergencies, this study stresses the importance of early diagnosis and elective treatment.