Influence of moderate hypothermic circulatory arrest on outcome in patients undergoing elective replacement of thoracic aorta

Sex-based disparities in ascending aortic aneurysm surgery outcomes: a comprehensive analysis of 1148 consecutive patients with propensity-score matching

BACKGROUND

Women undergoing cardiac surgery have been historically recognized to carry higher periprocedural mortality risk. We aimed to investigate the influence of sex on clinical presentation, perioperative, and long-term outcomes in patients who undergo surgery for ascending aortic aneurysm.

METHODS

We conducted a retrospective review of 1148 consecutive patients (380 [33.1%] female) who underwent thoracic aortic surgery under moderate hypothermic circulatory arrest for ascending aortic aneurysms between 2001 and 2021. Baseline and operative characteristics, in-hospital mortality, and survival were compared between male and female patients before and after propensity-score-matched (PSM) analysis.

RESULTS

Women were significantly older (median age: 69 [IQR: 63-75] vs. 67 [IQR: 58-73]; P < 0.001), while men had a higher prevalence of aortic valve stenosis, bicuspid valve and coronary artery disease at the time of surgery (P < 0.05). After PSM, EuroSCORE II (4.36 [2.68; 6.87] vs. 3.22 [1.85; 5.31]; p < 0.001), and indexed aortic diameter were significantly higher in female patients (2.94 [2.68; 3.30] vs. 2.58 [2.38; 2.81] cm/m2, p < 0.001). In the matched cohort, men were more likely to experience postoperative delirium (18.1% vs. 11.5%; P = 0.002), and postoperative neurological deficits (6.7% vs. 3.0%, P = 0.044),. Female patients were more likely to receive postoperative packed red blood cells (p = 0.036) and fresh frozen plasma (p = 0.049). In-hospital and 30-day mortality was similar between both groups. Long-term survival was comparable between both groups with 88% vs. 88% at 5 years, 76% vs. 71% at 10 years, and 59% vs. 47% at 15 years.

CONCLUSION

Female patients required more transfusions, while males had a higher incidence of postoperative delirium and neurological deficits. Differences in preoperative age and timing of surgery between the sexes could be attributed to variations in comorbidity profiles and the greater prevalence of concomitant surgery indications in males.

Temperature dependence of dielectric properties of blood at 10 Hz-100 MHz

The temperature dependence of the dielectric properties of blood is important for studying the biological effects of electromagnetic fields, electromagnetic protection, disease diagnosis, and treatment. However, owing to the limitations of measurement methods, there are still some uncertainties regarding the temperature characteristics of the dielectric properties of blood at low and medium frequencies. In this study, we designed a composite impedance measurement box with high heat transfer efficiency that allowed for a four/two-electrode measurement method. Four-electrode measurements were carried out at 10 Hz-1 MHz to overcome the influence of electrode polarization, and two-electrode measurements were carried out at 100 Hz-100 MHz to avoid the influence of distribution parameters, and the data was integrated to achieve dielectric measurements at 10 Hz-100 MHz. At the same time, the temperature of fresh blood from rabbits was controlled at 17-39°C in combination with a temperature-controlled water sink. The results showed that the temperature coefficient for the real part of the resistivity of blood remained constant from 10 Hz to 100 kHz (-2.42%/°C) and then gradually decreased to -0.26%/°C. The temperature coefficient of the imaginary part was positive and bimodal from 6.31 kHz to 100 MHz, with peaks of 5.22%/°C and 4.14%/°C at 126 kHz and 39.8 MHz, respectively. Finally, a third-order function model was developed to describe the dielectric spectra at these temperatures, in which the resistivity parameter in each dispersion zone decreased linearly with temperature and each characteristic frequency increased linearly with temperature. The model could estimate the dielectric properties at any frequency and temperature in this range, and the maximum error was less than 1.39%, thus laying the foundation for subsequent studies.