Editor's Choice - Nationwide Analysis of Patients Undergoing Iliac Artery Aneurysm Repair in the Netherlands

OBJECTIVE

The new 2019 guideline of the European Society for Vascular Surgery (ESVS) recommends consideration for elective iliac artery aneurysm (eIAA) repair when the iliac diameter exceeds 3.5 cm, as opposed to 3.0 cm previously. The current study assessed diameters at time of eIAA repair and ruptured IAA (rIAA) repair and compared clinical outcomes after open surgical repair (OSR) and endovascular aneurysm repair (EVAR).

METHODS

This retrospective observational study used the nationwide Dutch Surgical Aneurysm Audit (DSAA) registry that includes all patients who undergo aorto-iliac aneurysm repair in the Netherlands. All patients who underwent primary IAA repair between 1 January 2014 and 1 January 2018 were included. Diameters at time of eIAA and rIAA repair were compared in a descriptive fashion. The anatomical location of the IAA was not registered in the registry. Patient characteristics and outcomes of OSR and EVAR were compared with appropriate statistical tests.

RESULTS

The DSAA registry comprised 974 patients who underwent IAA repair. A total of 851 patients were included after exclusion of patients undergoing revision surgery and patients with missing essential variables. eIAA repair was carried out in 713 patients, rIAA repair in 102, and symptomatic IAA repair in 36. OSR was performed in 205, EVAR in 618, and hybrid repairs and conversions in 28. The median maximum IAA diameter at the time of eIAA and rIAA repair was 43 (IQR 38-50) mm and 68 (IQR 58-85) mm, respectively. Mortality was 1.3% (95% CI 0.7-2.4) after eIAA repair and 25.5% (95% CI 18.0-34.7) after rIAA repair. Mortality was not significantly different between the OSR and EVAR subgroups. Elective OSR was associated with significantly more complications than EVAR (intra-operative: 9.8% vs. 3.6%, post-operative: 34.0% vs. 13.8%, respectively).

CONCLUSION

In the Netherlands, most eIAA repairs are performed at diameters larger than recommended by the ESVS guideline. These findings appear to support the recent increase in the threshold diameter for eIAA repair.

There is no attentional global effect: Attentional shifts are independent of the saccade endpoint

Many studies have found a strong coupling between selective attention and eye movements. The premotor theory of attention suggests that saccade preparation is directly responsible for such attentional shifts. While it has already been shown that the attentional shift is not directly coupled to the final stages of motor execution, it is currently unknown to what aspect of the earlier stages of saccade preparation the attentional shift is coupled. An important step in this preparation process is resolving the landing point when multiple elements compete for the saccade. Here we ask how such a competition influences the presaccadic attentional locus and whether the presaccadic shift of attention is coupled to the saccade landing position or the possible saccade goals. To this end, we adopt a global effect paradigm where a target is accompanied by a salient distractor resulting in the majority of eye movements landing in between target and distractor. To determine the allocation of attention, participants are presented with a discrimination task shortly before the execution of the saccade. Despite a strong global effect obtained for saccade endpoints, we find little evidence for attentional facilitation at the location between target and distractor, but strong attentional facilitation at the location of the target and distractor. We argue that attention is coupled to active oculomotor programs, but not part of the resolution of these programs towards the execution of the saccade.

A global effect of capture saccades

When two target elements are presented in close proximity, the endpoint of a saccade is generally positioned at an intermediate location (‘global effect’). Here, we investigated whether the global effect also occurs for eye movements executed to distracting elements. To this end, we adapted the oculomotor capture paradigm such that on a subset of trials, two distractors were presented. When the two distractors were closely aligned, erroneous eye movements were initiated to a location in between the two distractors. Even though to a lesser extent, this effect was also present when the two distractors were presented further apart. In a second experiment, we investigated the global effect for eye movements in the presence of two targets. A strong global effect was observed when two targets were presented closely aligned, while this effect was absent when the targets were further apart. This study shows that there is a global effect when saccades are captured by distractors. This ‘capture global’ effect is different from the traditional global effect that occurs when two targets are presented because the global effect of capture saccades also occurs for remote elements. The spatial dynamics of this global effect will be explained in terms of the population coding theory.

Impedance cardiography in cardiac surgery patients: abnormal body weight gives unreliable cardiac output measurements

BACKGROUND

To study the accuracy of cardiac output measurement by means of Electrical Impedance Cardiography (EIC) in post-cardiac surgery patients.

METHODS

In a prospective study, we compared cardiac output measurements by means of thermodilution (COTD) with impedance cardiographic-derived values (COEIC) in 37 mechanically ventilated patients after cardiac surgery. Both methods were used simultaneously.

RESULTS

COEIC values were weakly correlated with COTD in the total group when the equation of Sramek-Bernstein was employed to calculate COEIC (r = 0.60, P < 0.001, mean difference and standard deviation: -0.06 +/- 1.25 l.min-1). After exclusion of the 12 patients whose body weight differed > 15% from their ideal body weight, no significant difference was found between the mean values (5.40 +/- 1.80 l.min-1 (COEIC) vs 5.31 +/- 1.69 l.min-1, n = 25) while the correlation coefficient increased substantially (r = 0.85, P < 0.001, mean difference and standard deviation: 0.09 +/- 0.96 l.min-1).

CONCLUSIONS

The results of this study indicate that weight is a very important factor in unreliable measurement of CO by impedance cardiography in cardiac surgery patients. The calculation equation as proposed by Sramek and Bernstein is not accurate enough in patients with more than 15% of weight deviation. Therefore, the use of impedance cardiography in these patients is of limited value until an accurate correction factor has been developed.

Interstitial fluid volume during cardiac surgery measured by means of a non-invasive conductivity technique

Fluid accumulation in the interstitium is frequently found after cardiac surgery. In extreme this can lead to pulmonary and myocardial oedema. The origin of this accumulation is not exactly known and may be twofold. It is probably a combination of the noninfectious whole body inflammatory response and a change in Starling forces due to a decrease in colloid osmotic pressure (COP) which is caused by the primed extracorporeal circuit. To study the changes in interstitial fluid volume (ISFV) a non-invasive conductivity technique was used. The relationship between temperature and conductivity was first investigated in vitro. A linear relationship was found between conductivity and different saline solutions and temperature. From the in vitro experiments it can be concluded that temperature corrected conductivity does not depend on haematocrit. After the in vitro experiments eleven patients undergoing cardiac surgery were studied. During the first minutes of cardiopulmonary bypass (CPB) a steep significant decrease in COP to 61.4 +/- 6.9% (from 19.6 +/- 1.1 to 12.0 +/- 1.2 mmHg), and a rise in ISFV to 105.5 +/- 2.8% (from 12.3 +/- 1.4 mS to 14.0 +/- 1.3 mS) was noticed. After this decrease COP increased significantly, till the end of the operation, but did not reach the pre-operative level. An increase in ISFV was noticed till the rewarming point. After this point no significant change in ISFV was noticed. Furthermore, a significant correlation was found between the fluid balance and the ISFV increase at the start, at the end of CPB, and at the end of the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of Ringer's lactate and gelatin infusion on the internal fluid balance of healthy volunteers measured by a non-invasive conductivity technique

Eight healthy male volunteers received in random order at an interval of 1 week 2 litres of Ringer's lactate or 0.8 litre of gelatin (Gelofusine) over half an hour, after overnight fasting. At the end of the infusion period, blood volume and mean arterial pressure had increased significantly in both groups but the increase in blood volume was more pronounced with the colloid. Extracellular fluid volume increased significantly after Ringer's lactate, while a significant decrease was noticed after gelatin. A small decrease in intracellular fluid volume was noted after infusion of Gelofusine, whereas it did not change after infusion of Ringer's lactate. During the 30 min after infusion, blood volume decreased significantly after both treatments but after the colloid it remained higher than the initial value. During the post-infusion period, no significant changes in either intra- or extracellular volume were seen after either treatments. At the end of the study, urine production was significantly more after the Ringer's lactate. It can be concluded that infusion of 0.8 litre of gelatin results in a larger and longer lasting increase in blood volume than 2 litres of Ringer's lactate, probably due to mobilization of extracellular fluid volume. It also leads to extracellular fluid accumulation. The decrease in blood volume after infusion is caused by increased urine production, since no changes were seen in intra- and extracellular fluid volume during this period.

Non-invasive monitoring of blood volume during hemodialysis: its relation with post-dialytic dry weight

Hemodialysis has a profound effect on fluid balance. Since fluid is initially withdrawn from the intravascular compartment, blood volume will decrease rapidly. A fluid shift (refill) from the overhydrated interstitium towards the intravascular compartment counteracts hypovolemia. Underestimation of postdialytic dry weight will cause interstitial dehydration and consequently a low refill capacity. This can cause hypovolemia-induced hypotension, a serious problem in the daily practice of hemodialysis: during one out of three sessions a hypotensive episode occurs. Clinical criteria to estimate post-dialytic dry weight are insensitive. We have developed non-invasive methods to estimate dry weight and changes in blood volume (BV) more accurately. The aim of this study was to investigate the relation between hydration state of the patient and changes in BV during treatment. Therefore, 37 hemodialysis patients were divided into three groups according to their post-dialytic extracellular fluid volume (EFV), which was measured by means of the non-invasive conductivity method: de- (N = 11), normo- (N = 18), and overhydrated (N = 8). Using an on-line optical reflection method, changes in BV were measured continuously during hemodialysis. BV decrease, corrected for ultrafiltration, was stronger in the dehydrated (4.4 +/- 1.5%/liter) than in the normohydrated (3.3 +/- 1.5%/liter) and overhydrated (2.7 +/- 1.9%/liter) groups. In the dehydrated group, the frequency of hypotensive episodes (48.5 +/- 20.2%) was significantly greater compared to the normohydrated (20.5 +/- 23.5%) or overhydrated (6.5 +/- 6.5%) group, P < 0.005.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous measurement of blood volume during hemodialysis by an optical method

A new method is described to noninvasively and continuously measure changes in blood volume (BV) during hemodialysis by means of an optical reflection method with an optical monitor (950 nm) clipped onto the arterial blood line. The amount of reflected light (L) appeared to be linearly proportional to the erythrocyte concentration (r = 0.91). Changes in L correlated well with changes in erythrocyte concentration during hemodialysis (r = 0.94). A study in 10 patients on regular dialysis was done. The BV decrease after 3 hr of treatment was 17.0 +/- 5.2%, and it correlated with the amount of fluid withdrawn by ultrafiltration (mean, 2,519 +/- 589 ml). Five hypotensive episodes were seen that were characterized by a higher rate of BV fall during the preceding 15 min (9.9 +/- 1.9 versus 3.6 +/- 4.3%/hrp; p < 0.05) and by a lower BV value at that moment (78.2 +/- 3.4 versus 84.5 +/- 4.5%; p < 0.025) than in the other five patients at comparable times. It was concluded that this optical method was a means to detect hypovolemia at an early stage and to prevent ultrafiltration induced hypotension.