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.

Chiral spin liquid and emergent anyons in a Kagome lattice Mott insulator

Topological phases in frustrated quantum spin systems have fascinated researchers for decades. One of the earliest proposals for such a phase was the chiral spin liquid, a bosonic analogue of the fractional quantum Hall effect, put forward by Kalmeyer and Laughlin in 1987. Elusive for many years, recent times have finally seen this phase realized in various models, which, however, remain somewhat artificial. Here we take an important step towards the goal of finding a chiral spin liquid in nature by examining a physically motivated model for a Mott insulator on the Kagome lattice with broken time-reversal symmetry. We discuss the emergent phase from a network model perspective and present an unambiguous numerical identification and characterization of its universal topological properties, including ground-state degeneracy, edge physics and anyonic bulk excitations, by using a variety of powerful numerical probes, including the entanglement spectrum and modular transformations.

Comparison of end-tidal and transcutaneous measures of carbon dioxide during general anaesthesia in severely obese adults

BACKGROUND

Patients with severe obesity (body mass index (BMI) greater than 35 kg x m(-2)) present difficulties for end-tidal carbon dioxide (FE'(CO(2))) monitoring. Previous studies suggest that transcutaneous (TC) carbon dioxide measurements could be valuable, so we compared FE' and TC measures with Pa(CO(2)) in severely obese patients during anaesthesia.

METHODS

We studied patients with severe obesity (BMI >or=40 kg x m(-2)) undergoing gastric bypass surgery. Carbon dioxide was measured with both FE' and TC devices. The difference between each measure (FE'(CO(2)) and TC-CO(2)) and the Pa(CO(2)) was averaged for each patient to provide one value, and data compared with a non-paired, two-way t-test, Fisher's exact test.

RESULTS

We studied 30 adults (aged 18-54 yr, mean 41, SD 8.0 yr; weight: 115-267 kg, mean 162, SD 35 kg). The absolute difference between the TC-CO(2) and Pa(CO(2)) was 0.2 (0.2) (mean, SD) kPa while the absolute difference between the FE'(CO(2)) and Pa(CO(2)) was 0.7 (0.4) kPa (P<0.0001). The bias and precision were +0.1 (0.3) kPa for TC vs arterial carbon dioxide and -0.7 (0.4) kPa for FE' vs arterial carbon dioxide.

CONCLUSIONS

Transcutaneous carbon dioxide monitoring provides a better estimate of Pa(CO(2)) than FE'(CO(2)) in patients with severe obesity.

Suppression of spinal and cortical somatosensory evoked potentials by desflurane anesthesia

The effect of the volatile anesthetic desflurane on spinal and cortical somatosensory evoked potentials (SEPs) was examined in 11 Sprague-Dawley male rats. Platinum recording electrodes were placed stereotactically over the left somatosensory cortex and dorsal midline of the T11-12 spinal cord while the right posterior tibial nerve was stimulated at twice motor threshold. The effect of desflurane was examined at various concentrations ranging from 0.7 to 11.4% (2 MAC). Mean arterial blood pressure (MAP) decreased (p = 0.001) progressively with increasing end-tidal desflurane concentrations. Concentrations of 1.4% (1/4 MAC) and 2.8% (1/2 MAC) did not significantly affect the spinal SEP (SSEP) amplitude or the latency. With higher concentrations, there was a progressive decrease in amplitude of the cortical SEPs (CSEPs; p = 0.002) and SSEPs (p = 0.008). However, CSEP and SSEP latencies did not change. At 5.7% (1 MAC), three animals (33%) lost CSEPs while SSEPs remained intact. At 11.4% (2 MAC), the CSEPs were lost in all animals. Only one rat lost the SSEPs at the 2 MAC concentration of desflurane, indicating the resistance of the SSEPs to desflurane anesthesia. We conclude that desflurane anesthesia significantly alters the amplitude of SSEPs and CSEPs without a significant change in the peak latency.

Effect of desflurane anesthesia on transcortical motor evoked potentials

The effect of the volatile anesthetic desflurane on motor evoked potentials was examined in male rats. Animals underwent cortical stimulation using small platinum ball stimulating electrodes secured on the motor cortex. To record evoked compound muscle action potentials (CMAPs), single-shock electrical stimulation was delivered to the forelimb representation of the motor cortex. Muscle responses were readily obtained in the contralateral extensor muscles. The effect of desflurane was examined at various concentrations ranging from 0.7 to 11.4%. With increasing concentrations of desflurane, there was a progressive decrease in the CMAP amplitude and systemic blood pressure over the baseline values. This decrease became statistically significant (p = 0.0078) at 5.7% [1 maximum alveolar concentration (MAC)] concentration of desflurane. Although there was a decrease in heart rate, the results were not statistically significant (p = 0.03). No significant difference in the onset latency or the duration of the CMAP was noted at different concentrations of the anesthetic. We conclude that desflurane anesthesia significantly alters the amplitude of the muscle response evoked by motor cortex stimulation in experimental animals.

Late outcomes of limb loss after failed infrainguinal bypass

PURPOSE

Most reports regarding infrainguinal bypass surgical procedures demonstrate benefits well but pay less attention to adverse outcomes and consequences of failure for the patient. For a wider scope of infrainguinal bypass surgical procedures, we evaluated patient-oriented outcomes of limb loss occurring after failed infrainguinal bypass operations.

METHODS

Eighty-one patients with vascular amputations were identified in a retrospective study. Follow-up was complete with a mean of 3.6 years. Life-table and multivariate analyses were used to assess factors influencing the desired outcome goals of rehabilitation. Mortality rates, social function, risk of contralateral amputation, and the ability to walk were used to measure the late outcome.

RESULTS

The long-term survival rate was poor (72% at 1 year; 53% at 3 years) and was not related to traditional risk factors for atherosclerosis. Moreover the risk for contralateral amputation was 10% per year. One year after amputation 81% (47 of 58) of the surviving amputees were walking independently, and 73% (42 of 58) were living at home, 32 with their spouse. At 3 years these results were 73% (27 of 37) and 78% (29 of 37), respectively. In addition, the level of self-care changed significantly (p < 0.001) after amputation. Advanced age (older than 65 years), self-care performance, and living with someone were important predictors of late outcome.

CONCLUSIONS

It is possible for a high percentage of patients with vascular amputations to return home successfully, either walking or in a wheelchair. Moreover this result can be predicted based on preoperative clinical variables. These data may be helpful to guide fitting of prosthetic devices, planning of discharge home, and use of health care resources.

Motor-evoked potential changes during hypoxic hypoxia

Motor-evoked potentials (MEPs) from forearm muscles were recorded in response to single-shock electrical stimulation of motor cortex of rats (n = 15) under pentobarbital anesthesia and controlled room air ventilation. In addition, electroencephalograms (EEGs) were recorded for all animals. Following baseline MEP recording in room air (21% O2), animals were subjected to graded hypoxia of either 15.75%, 10.5%, or 5.25% oxygen for 10 minutes, then followed by room air ventilation for 15 minutes. The mean baseline latency, amplitude, and duration of the evoked muscle response were 4.3 +/- 0.4 mseconds, 556 +/- 476 microV, and 9.6 +/- 2.3 mseconds, respectively. At moderate hypoxia (15.75%), the latency was 4.2 +/- 0.5 mseconds and the amplitude and the duration were 530 +/- 356 microV (n = 14), and 9.5 +/- 2.2 mseconds, (n = 14). These values did not deviate significantly from baseline (p > 0.56). Only one animal lost MEPs at the 15.75% hypoxia level. At 10.5% hypoxia, 27% of animals (n = 4) lost MEP within minutes. In the remaining animals (n = 11), there was a trend toward a prolongation of latency and a decrease of both amplitude and duration. All animals lost MEPs under extreme hypoxia (5.25%) within 2 minutes. No change was seen in the EEG recording until the level of extreme hypoxia was reached. The loss of MEPs at this level of hypoxia was concurrent with the loss of EEGs. We conclude that hypoxia effects MEPs in experimental animals.

The effects of propofol anesthesia on transcortical electric evoked potentials in the rat

The effects of halogenated anesthetic agents on somatosensory and motor evoked potentials (MEP) have been documented previously. Intravenous anesthetic propofol has not yet been used during MEP monitoring. This study investigates the effects of propofol on transcortical MEP in rats during bolus, infusion, and recovery conditions. After baseline MEP recordings, animals received a hetastarch bolus, followed by a propofol (10 mg/kg) bolus dose. A propofol infusion (10 mg/kg/h) and a hetastarch infusion were then begun. MEP recordings were obtained after the propofol bolus, during the infusion, and after a 30-minute recovery phase. Blood pressure readings remained stable. MEP onset latency increased, and amplitude decreased. Response duration diminished. All values returned towards the baseline during recovery. Our results show that the effects of propofol on MEPs are similar to its effects on somatosensory evoked potentials. Propofol seems to be a reasonable agent for use during intraoperative MEP monitoring and should be further investigated for use during spinal cord monitoring in humans.