Use of passive function testing in venous insufficiency: a prospective study.

In a prospective study, the results of venous function tests in 19 lower extremities with deep venous insufficiency and in seven control extremities were compared. First, the routine method of asking the patients to exercise their calves was used. Second, cuffs around the calves were rapidly inflated, producing standardized external compression to the calf muscle pump. Our aim was to decrease the influence of artifacts from involuntary muscle efforts and especially to render reproducible results of pressure reduction after passively pumping. The passive function test proved to be the only technique with which a decrease in pressure measured with strain gauges while the patient was in the standing position could significantly be discriminated between diseased and control extremities. Furthermore, the correlation of pressure decrease invasively versus measured noninvasively improved to 37% and thus became significant. Simulating calf venous pump function with the aid of inflatable cuffs is easily applicable in the vascular laboratory. It enables the vascular surgeon to reliably quantify venous recovery time and pressure reduction.

Endoluminal pulse oximetry in ischemic colon in a swine model.

BACKGROUND: Postoperative sigmoidal ischemia after aortic grafting is a severe complication. No simple methods are available to detect this entity at an early stage. This study was done to monitor for sigmoidal ischemia with a new endoluminal probe based on pulse oximetry (SmO2). STUDY DESIGN: A prospective controlled animal study was done. Five pigs with low flow in the caudal mesenteric artery (20 percent of the basal flow) and four pigs in a control group were included. General and local circulatory parameters were monitored in the carotid and pulmonary artery and in the caudal mesenteric vein (CMV). Mucosal biopsy specimens were taken for histologic examination. Statistical analysis was done with the Wilcoxon and Mann-Whitney rank sum test and with analysis of variance. RESULTS: During the first two hours of ischemia, no sigmoidal pulse was detected. During the third hour, in three pigs the pulse curve reappeared with a SmO2 of 48 to 88 percent. After two hours, the mean oxygen saturation in the CMV of the ischemic group was 64 percent (compared with the control group, 77 percent, p < 0.05). After one hour, the mean lactate concentrations were 2.0 and 1.3 mmol per L, respectively (p < 0.05). Significant histologic changes occurred with neutrophilic infiltration in the crypts, in the lamina propria, and in the submucosa. CONCLUSIONS: Low-flow sigmoidal ischemia can be detected and monitored with endoluminal pulse oximetry in this model of early sigmoidal ischemia.

Use of a mixture of medium-chain triglycerides and longchain triglycerides versus long-chain triglycerides in critically ill surgical patients: a randomized prospective double-blind study.

Twenty critically-ill surgical patients who needed total parenteral nutrition were randomly enrolled in a double-blind study comparing two intravenous fat emulsions: one containing a mixture of 50% medium-chain triglycerides and 50% long-chain triglycerides and another containing 100% longchain triglycerides. The purpose of this study was to investigate metabolic and biochemical differences between both emulsions with special reference to liver enzymes. After a baseline period of 24 h with only glucose and NaCl infusion, the lipid emulsion was added continuously during 24 h over 5 days. The parenteral nutrition was administered in mixture bags containing amino-acids, glucose and lipids together. Two-thirds of the non-protein calories were administered as glucose 40% and one third as either long-chain triglycerides or a mixture of medium-chain triglycerides and long-chain triglycerides. The total amount of non-protein calories received was the measured energy expenditure during the baseline period plus 10% and was fixed during the study. Plasma substrate concentrations, energy expenditure, and nitrogen balance were determined and arterial blood samples were taken. No toxic effects or complications attributable to one of the two emulsions were observed. There was no significant difference in energy expenditure, nitrogen balance, liver function tests, carnitine, transferrin, pre-albumin, albumin, cholesterol, triglycerides and free fatty acids. The only parameter that showed a different pattern of reaction between the two emulsions was serum bilirubin concentration. In this study no evidence of any advantageous effect of a mixture of medium-chain triglycerides and long-chain triglycerides was seen.

Local colonic blood pressure degree through aortic reconstruction procedures: a porcine model.

Sigmoideal ischemia after aortic grafting is a severe complication with high morbidity and mortality. To investigate the basics of this circulatory problem an animal model was created with sigmoideal ischemia that could be quantified. For this purpose a new pig model was developed with stable general circulatory and ventilatory parameters for several hours, while at the same time controlled sigmoideal ischemia was induced. In five pigs a left retroperitoneal approach to the aorta was performed to isolate the caudal mesenteric artery (CMA). Sigmoideal ischemia was achieved by ligating the collateral circulation and constricting the distal aorta. A flow probe was applied to the CMA. An intravascular saturation probe was introduced in the caudal mesenteric vein (CMV) and a pulse oximeter was applied to the serosal surface of the sigmoid. Every hour, blood gas analyses from the carotic artery, CMA, and CMV were completed. Registrations of all circulatory and ventilatory parameters were performed with the help of a computer. The mean flow in the CMA was 29 mL/min (13-45) and decreased to 5 mL/min (3-7) after aortic constriction. Parameters reflecting the stability of the model, such as the cardiac index (mean 89 mL/min kg-1), the mixed venous oxygen saturation (mean 67%), and the total body oxygen consumption (mean 3.3 mL/min kg-1), did not change with statistical significance during 4 h of partial aortic constriction. The conclusion is that a new model has been developed of quantitative sigmoideal ischemia in the pig that was stable for several hours.

Experimental study of the pressure-volume and pressure-time relations in the completely obstructed pelvis of the porcine kidney. Part 4: Instability and blow out.

In a series of experiments with pigs the completely obstructed renal pelvis was filled with Ringer's lactate at a constant rate of 2 ml/min until the pressure did not longer increase linearly. By means of continuous X-ray monitoring and histological examination of the infused kidneys it was found that blow out may occur at pressure levels individually varying from 60 to 180 mmHg. The histological features of this phenomenon are presented and the clinical significance is discussed.

Experimental study of the pressure-volume and pressure-time relations in the completely obstructed pelvis of the porcine kidney. Part 1: Introduction and theory.

Little is known about pressure-volume and pressure-time relations of the obstructed renal pelvis. In a series of experiments with pigs the completely obstructed renal pelvis was infused with Ringer's lactate at a constant rate of 2 ml/min. On the basis of these experiments a mathematical description is given of the pressure-volume and pressure-time relations that were recorded.

Experimental study of the pressure-volume and pressure-time relations in the completely obstructed pelvis of the porcine kidney. Part 2: The relation between actual hydrostatic pressure, intrapelvic volume and time.

In a series of experiments with pigs the completely obstructed renal pelvis was infused with Ringer's lactate at a constant rate of 2 ml/min. At various pressure levels (lower than 50 mm Hg) the relations pressure vs infused volume and pressure vs actual intrapelvic volume and the effects on the intrapelvic pressure of rapid total or partial extraction of the actual volume were measured. At pressure levels lower than 15-20 mm Hg the P-V relation is exponential; at pressure levels between approximately 20 to 50 mm Hg this relation is linear. In the pressure range from 20 to 50 mm Hg the pressure decays, at a constant or increasing volume, asymptotically to a certain stabilisation value when the infusion is stopped. The relation between stabilised pressure and intrapelvic volume is linear.

Experimental study of the pressure-volume and pressure-time relations in the completely obstructed pelvis of the porcine kidney. Part 3: Stability of the pelvicalyceal system.

In a series of experiments with pigs the completely obstructed renal pelvis was filled with Ringer's lactate at a constant rate of 2 ml/min. At various pressure levels lower than 50 mm Hg the relations pressure vs infused volume and pressure vs actual intrapelvic volume were repeatedly measured. It was concluded that the measurements were reproducible and that the pelvicalyceal system is -under these experimental conditions- a stable elastic unit.

Failure of quantitative venous photoplethysmography to assess venous insufficiency: a prospective clinical study.

The increase of deep venous reconstructive surgery necessitates reliable tests for evaluation of the results, which requires quantization of the expelled volume. This could only be done with invasive measurements, but now it seems possible to calibrate photoelectric cells, and quantize the results. Nineteen limbs of patients with deep venous disease and seven limbs of healthy volunteers were evaluated, with methods known from the literature. In addition to measurements in standing position, these methods were used in the more patient-friendly sitting position. Invasively and noninvasively measured recovery times correlated well in the standing (R = 0.83) and in the sitting position (R = 0.86). However, the quantization of expelled volume did not significantly correlate. Also, the differences between expelled volume of controls and patients were only significant with invasive measurements in the standing position (P = 0.006) as well as in the sitting position (P = 0.004). The differences were not significant with the noninvasive method. In our opinion, photoelectric cells still do not offer an alternative for invasive measurements in the evaluation of results after venous reconstructive surgery.

The effect of inhibition of renin-angiotensin system by valsartan during hypovolemic shock and low flow sigmoideal ischaemia in pigs.

The aim of this experiment was to study the effect of Renin-Angiotensin System (RAS) blockade by means of valsartan on the colonic and systemic circulation in pigs during low flow sigmoideal ischemia in combination with hypovolemic shock. This condition resembles the situation that occurs in patients suffering from a ruptured aneurysm and a compromised colonic circulation. An experimental study in pigs was performed : 6 pigs with low flow sigmoideal ischemia and hypovolemic shock were treated with valsartan and a control group of 5 pigs with low flow sigmoideal ischemia and hypovolemic shock without medical treatment.Valsartan, 3 mg/kg, was administered intravenously. The operation was performed via left sided lumbotomy. The distal aorta was partially occluded to a flow reduction of 30% of the initial value. Hypovolemic shock was induced by withdrawing 20 ml/kg blood in 45 min. Resuscitation with 30 ml/kg haemaccel was iniated after 2 h of shock. The following parameters were measured: blood pressure, cardiac output; hemoglobin, lactate, angiotensin II in mixed venous blood (obtained from pulmonary artery) and in splanchnic blood (obtained from caudal mesenteric vein); and endoluminal pulse oximetry of the sigmoideal mucosa. Statistical analysis was performed by ANOVA and Wilcoxon signed rank test. There was a significant increase of lactate levels both in systemic and splanchnic circulation (P<0.05) in both groups. In the control group, the mean angiotensin II concentrations in the systemic circulation increased, after induction of ischaemia and shock. In the experimental group, the increase in angiotensin concentrations after resuscitation was significantly more prominent. In the colonic circulation, in both groups, there was a significant increase in angiotensin II levels in the splanchnic circulation following ischaemia and reperfusion (P<0.05), but there was no significant difference between the groups. There were no detectable mucosal signals measured by pulse oximetry after induction of shock throughout the experiment, whereas in the experimental group, median mucosal oxygen saturations of 81, 74.5 and 85% were achieved after resuscitation and declamping (P<0.01).In conclusion, angiotensin II inhibition during hypovolemic shock improves the colonic circulation, measured by pulse oximetry. However, other parameters of tissue ischaemia did not improve.

Endoluminal aortic shunting for distal perfusion during thoracic aortal cross-clamping in a pig model.

PURPOSE OF THE STUDY: To investigate the haemodynamic properties of a direct endovascular aortic shunt to maintain distal aortic perfusion as an alternative of a distal shunt (left-left-, Gott shunt) in thoracic aortic aneurysm repair. METHODS: A shunt was developed and tested in an in vitro model which should be capable of transporting a flow of 3-4 L/min with a decrease in blood pressure < 20 mmHg. Thereupon the shunt was tested in an in vivo experiment in six pigs to assess the possibility of its use with normal distal blood pressure. The shunt was inserted in the thoracic aorta and stayed in place for 1.5 h. Parameters were measured at six time intervals to assess organ perfusion, -function, cardiac output, proximal- and distal blood pressure and aortic- and shunt flow. PRINCIPLE FINDINGS: The mean blood flow through the shunt was 2.5 L/min. The difference of the mean blood pressure over the shunt was on average 14.20 mmHg. Parameters for coagulation disturbance and organ ischaemia were tested. The decrease in mean thrombocyte count was 299-158 (p<0.02). The venous lactate and the venous mesenteric lactate as parameters for intestinal ischemia did not increase significantly. No significant changes occurred in angiotensin II levels. Pulsatile flow was maintained but significantly suppressed (60%) distal from the shunt. The clamp time needed to insert the shunt and the venous mesenteric lactate, as well as the venous lactate, showed high correlation, r(s) = 0.9 (p<0.05) and r(s) = 0.94 (p<0.01). This also accounted for the 2nd clamp time, both r(s) = 0.95 (p<0.05). CONCLUSION: The shunt is capable of transporting a blood flow of 2-4 L/min with an acceptable decrease in distal blood pressure. However, the time, needed to insert the shunt, was significantly associated with parameters of organ ischaemia.

Sigmoidal ischaemia after aortic grafting, detected by endoluminal pulse oximetry.

Colonic ischaemia after abdominal aortic grafting is a severe complication. Late detection of transmural ischaemia will result in a high mortality rate. No simple specific methods are available to detect the early stage. The aim of this pilot study was to detect and monitor sigmoidal ischaemia after aortic surgery with a new endoluminal sigmoidal probe, based on pulse oximetry. Twelve patients with sigmoidal ischaemia were included, the endoluminal probe being introduced into the sigmoid at least 25 cm proximal to the anal verge. It is shown that with this method, mucosal and transmural ischaemia can be graded and differentiated. Patients who showed no wave-form had transmural ischaemia; those with mucosal ischaemia showed reliable wave-forms with oxygen saturation from 40-85%. Colonic ischaemia after aortic grafting can be detected by endoluminal pulse oximetry but the clinical outcome will only improve by early detection in the preclinical stage.

The renin-angiotensin system in swine during hypovolaemic shock combined with low-flow ischaemia of the sigmoid colon.

Colonic ischaemia is a serious complication after aortic surgery, and is most frequent after repair of ruptured aortic aneurysms. It was felt that the increased risk of colonic ischaemia during shock might be the result of a local effect of the renin-angiotensin system in the splanchnic circulation, which is exacerbated by poor perfusion. In order to evaluate the activity of the renin-angiotensin system in the colonic circulation, a subtotal occlusion of the distal aorta was induced in nine pigs. A colonic flow reduction of 70% was created for 4 hours. In the experimental group (n = 6), induce hypovolaemic shock, 20 cm3/kg blood was sampled at 45 min before resuscitation was performed with 20 cm3/kg haemaccel. The sham group (n = 3) did not have hypovolaemic shock induced. Blood samples were taken for determinations of angiotensin II, haemoglobin and lactate. Blood gas was obtained from the pulmonary artery and the caudal mesenteric vein for blood gas analysis and lactate determinations. ANOVA and the Wilcoxon sum rank test were used for statistical analysis. There was a significant increase in angiotensin II after induction of ischaemia in both groups. The increase in angiotensin II in the splanchnic circulation was more prominent than the increase in the systemic circulation (P < 0.01). In the experimental group, there was a sustained increase in angiotensin II levels in the splanchnic circulation following shock and reperfusion (P < 0/01). The increase in lactate concentrations, which was significantly higher in the experimental group (P < 0.05), was evidence of intestinal ischaemia. There was a significant decline in cardiac output and blood pressure during the period of shock (P < 0.05). The combination of colonic ischaemia and hypovolaemic shock followed by reperfusion leads to an increase in angiotensin II activity. The increase of the local activity of the renin-angiotensin system in the splanchnic circulation is more prominent after ischaemia and reperfusion. This is probably caused by a selective response of the splanchnic vasculature to shock, ischaemia and reperfusion.

A modified scintigraphic technique for amputation level selection in diabetics.

A modified 123I-antipyrine cutaneous washout technique for the selection of amputation levels is described. The modifications imply a reduction of time needed for the examination by simultaneous recordings on different levels, and a better patient acceptance by reducing inconvenience. Furthermore, both skin perfusion pressure (SPP) and skin blood flow (SBF) are determined from each clearance curve. In a prospective study among 26 diabetic patients presenting with ulcers or gangrene of the foot, both SPP and SBF were determined preoperatively on the selected level of surgery and on adjacent amputation sites. These 26 patients underwent 12 minor foot amputations and 17 major lower limb amputations. Two of these amputations failed to heal. SBF values appeared indicative for the degree of peripheral vascular disease, as low SBF values were found with low SPP values. SPP determinations revealed good predictive values: all surgical procedures healed when SPP greater than 20 mmHg, but 2 out of 3 failed when SPP less than 20 mmHg. If SPP values would have been decisive, the amputation would have been converted to a lower level in 6 out of 17 cases. This modified scintigraphic technique provides accurate objective information for amputation level selection.