Risk Factors for Hypoxemia After Surgery for Acute Type A Aortic Dissection

Study on risk factors and treatment strategies of hypoxemia after acute type a aortic dissection surgery

Acute type A aortic dissection is a life-threatening cardiovascular disease characterized by rapid onset and high mortality. Emergency surgery is the preferred and reliable treatment option. However, postoperative complications significantly impact patient prognosis. Hypoxemia, a common complication, poses challenges in clinical treatment, negatively affecting patient outcomes and increasing the risk of mortality. Therefore, it is crucial to study and comprehend the risk factors and treatment strategies for hypoxemia following acute type A aortic dissection to facilitate early intervention.

The impact of prolonged mechanical ventilation after acute type A aortic dissection repair

OBJECTIVE

Patients with type A aortic dissection have increased resource use. The objective of this study was to describe the relationship between prolonged mechanical ventilation and longitudinal survival in patients undergoing type A aortic dissection repair.

METHODS

We conducted a retrospective analysis of patients with type A aortic dissection undergoing repair from 2010 to 2018; Kaplan-Meier function and adjusted Cox regression analysis were used to compare in-hospital mortality and longitudinal survival accounting for time on mechanical ventilatory support.

RESULTS

A total of 552 patients were included. The study population was divided into 12 hours or less (n = 291), more than 12 to 24 or less hours (n = 101), more than 24 to 48 hours or less (n = 60), and more than 48 hours (n = 100) groups. Patients within the 12 or less hours group were the youngest (60.0 vs 63.5 years vs 63.6 vs 62.8 years; P = .03) and less likely to be female (31.6% vs 43.6% vs 46.7% vs 56.0%; P < .001). On the other hand, the more than 48 hours group presented with malperfusion syndrome at admission more often (24.4% vs 29.7% vs 28.3% vs 53.0%; P < .001) and had longer cardiopulmonary and ischemic times (P < .05). In-hospital mortality was significantly higher in the more than 48 hours group (5.2% vs 6.9% vs 3.3% vs 30.0%; P < .001). Multivariable analysis demonstrated worse longitudinal survival for the 24 to 48 hours group (hazard ratio, 1.94, confidence interval, 1.10-3.43) and more than 48 hours ventilation group (hazard ratio, 2.25, confidence interval, 1.30-3.92).

CONCLUSIONS

The need for prolonged mechanical ventilatory support is prevalent and associated with other perioperative complications. More important, after adjusting for other covariates, prolonged mechanical ventilation is an independent factor associated with increased longitudinal mortality.

Impact of body mass index on perioperative mortality of acute stanford type A aortic dissection: a systematic review and meta-analysis

BACKGROUND

Obesity may increase perioperative mortality of acute Stanford type A aortic dissection (ATAAD). However, the available evidence was limited. This study aimed to systematically review published literatures about body mass index (BMI) and perioperative mortality of ATAAD.

METHODS

Electronic literature search was conducted in PubMed, Medline, Embase and Cochrane Library databases. All observational studies that investigated BMI and perioperative mortality of ATAAD were included. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using a random-effects model. Meta-regression analysis was performed to assess the effects of different clinical variables on BMI and perioperative mortality of ATAAD. Sensitivity analysis was performed to determine the sources of heterogeneity. Egger's linear regression method and funnel plot were used to determine the publication bias.

RESULTS

A total of 12 studies with 5,522 patients were eligible and included in this meta-analysis. Pooled analysis showed that perioperative mortality of ATAAD increased by 22% for each 1 kg/m2 increase in BMI (OR = 1.22, 95% CI: 1.10-1.35). Univariable meta-regression analysis indicated that age and female gender significantly modified the association between BMI and perioperative mortality of ATAAD in a positive manner (meta-regression on age: coefficient = 0.04, P = 0.04; meta-regression on female gender: coefficient = 0.02, P = 0.03). Neither significant heterogeneity nor publication bias were found among included studies.

CONCLUSIONS

BMI is closely associated with perioperative mortality of ATAAD. Optimal perioperative management needs to be further explored and individualized for obese patient with ATAAD, especially in elderly and female populations.

TRIAL REGISTRATION

PROSPERO (CRD42022358619). BMI and perioperative mortality of ATAAD.

Postoperative pulmonary complications in patients undergoing aortic surgery: A single-center retrospective study

Postoperative pulmonary complications (PPCs) are among the most common complications after cardiovascular surgery. This study aimed to explore the real incidence of and risk factors for PPC in patients with acute type A aortic dissection (ATAAD) who underwent total aortic arch replacement combined with the frozen elephant trunk (TAR + FET). In total, 305 ATAAD patients undergoing TAR + FET from January 2021 to August 2022 in a single-center were divided into PPCs or non-PPCs group. The incidence of PPCs was calculated, risk factors of PPCs were analyzed, and postoperative outcomes were compared between these 2 groups. The incidence of any PPC was 29.2%. And the incidence of respiratory infection, respiratory failure, pleural effusion, atelectasis, pneumothorax, acute respiratory distress syndrome, aspiration pneumonitis, pulmonary edema and bronchospasm was 23.0%, 12.5%, 10.5%, 1.0%, 0.7%, 1.0%, 0%, 0.7%, 0%, respectively. The logistic regression analysis revealed that the history of diabetes, history of renal dysfunction, preoperative SpO2 <90%, cardiopulmonary bypass duration, fresh frozen plasma volume and platelet concentrates volume were independent risk factors for PPCs. Among 2 groups, postoperative ventilation duration, postoperative length of stay in intensive care unit and hospital were (73.5 ± 79.0 vs 24.8 ± 35.2 hours; P < .001), (228.3 ± 151.2 vs 95.2 ± 72.0 hours; P < .001) and (17.9 ± 8.8 vs 11.5 ± 6.2 days; P < .001). There was no difference between 2 groups of in-hospital mortality rate. Additionally, other short-term outcomes were also significantly poorer in patients with PPCs. PPCs are common in ATAAD patients undergoing TAR + FET, and could be multifactorial. PPCs occurrence are associated with poor patient outcomes postoperatively and worth further investigation.

Association of preoperative monocyte/lymphocyte ratio with postoperative oxygenation impairment in patients with acute aortic syndrome

BACKGROUND

Postoperative oxygenation impairment represents a common complication in patients with the acute aortic syndrome (AAS). The study aimed to explore the relationship between inflammatory indicators and AAS patients with oxygenation impairment after operation.

METHODS

In this study, 330 AAS patients who underwent surgery were enrolled and divided into 2 groups based on postoperative oxygenation impairment (non-oxygenation impairment group and oxygenation impairment group). Regression analysis was performed to assess the relationship between inflammatory indicators and postoperative oxygenation impairment. A smooth curve and interaction analysis were further conducted. Stratified analysis was used according to preoperative monocyte/lymphocyte ratio (MLR) (Tertiles).

RESULTS

Multivariate analysis showed that preoperative MLR was independently related to oxygenation impairment after surgery in AAS patients (OR, 95% CI, P: 2.77, 1.10-7.00, 0.031). The smooth curve indicated the risk of postoperative oxygenation impairment was higher with the elevated preoperative MLR. Interaction analysis revealed that patients with AAS with high preoperative MLR who had coronary artery disease (CAD) had a higher risk of oxygenation impairment after operation. Moreover, stratified analysis was performed according to baseline MLR (Tertiles), and a higher baseline MLR level in AAS patients was correlated with a lower arterial oxygen tension (P_aO2) / inspiratory oxygen fraction (F_iO2) ratio perioperatively.

CONCLUSIONS

In AAS patients, preoperative MLR level was independently related to postoperative oxygenation impairment.

Hotspots and development frontiers of postoperative complications of AD: Bibliometric analysis - a review

The research on the postoperative complications of aortic dissection (AD) has received great attention from scholars all over the world, and the number of research articles in this field has consistently increased year after year. However, no bibliometric reports have been published yet to analyze the scientific output and the current situation in this field. The Bibliometrix R-package, VOSviewer, and CiteSpace software were used to conduct a bibliometric analysis of the hotspots and development frontiers of AD. A total of 1242 articles were retrieved. The USA, China, and Japan had the highest number of publications. The five keywords with the highest frequency were "analysis," "incidence," "acute type," "graft," and "risk factor." The results also indicated that the research in related fields had shifted from surgical treatment and utilizing experience to the evidence-based exploration of risk factors and the construction of prediction models to help better manage postoperative complications of AD. This is the first bibliometric analysis of global publications on the postoperative complications of AD. The current research hotspots focus on three areas: common postoperative complications of AD, exploration of the related risk factors, and management of complications. Future research could focus on identifying risk factors through meta-analysis and using a multicenter database for AD as well as building relevant models to predict the development of complications to better facilitate the clinical management of AD patients.

Impact of body mass index on postoperative oxygenation impairment in patients with acute aortic syndrome

Objective: Oxygenation impairment is a common complication of acute aortic syndrome (AAS) patients after surgical repair. The aim of this study is to identify the relationship between body mass index (BMI) and the risk of postoperative oxygenation impairment in AAS patients.

Methods: A total of 227 consecutive patients who were diagnosed as AAS and underwent surgical repair were recruited. They were divided into two groups based on the postoperative oxygenation impairment (non-oxygenation impairment group and oxygenation impairment group). Logistic regression was conducted to evaluate the association between BMI and the risk of oxygenation impairment after surgery. Dose-response curve and subgroup analysis were used to test the reliability of the results of regression analysis. A meta-analysis was then performed to further confirm these results using Pubmed, Embase, and Web of Science databases.

Results: For the retrospective study, a significant association was observed after adjusting for a series of variables. BMI was significantly correlated with postoperative oxygenation impairment in patients with AAS (OR, 95% CI, P: 1.27, 1.17–1.46, 0.001). Compared with the normal weight group (18.5 kg/m² ≤ BMI <23.0 kg/m²), patients with excessive BMI were at a higher risk of oxygenation impairment for the overweight group (23.0 kg/m² ≤ BMI <25 kg/m²) and obesity group (BMI ≥25 kg/m²) (OR, 95% CI, P: 4.96, 1.62–15.15, 0.005; 9.51, 3.06–29.57, <0.001). The dose-response curve showed that the risk of oxygenation impairment after surgery increased with the increased BMI. Besides, subgroup analysis showed that AAS patients who have an excess weight with a TNF-α ≥ 8.1 pg/ml carried an excess risk of postoperative oxygenation impairment. For the meta-analysis, the pooled result also indicated that AAS patients with high BMI had a significantly increased risk of oxygenation impairment after surgery (OR, 95% CI, P: 1.40, 1.18–1.66, 0.001).

Conclusion: Excessive BMI was an independent risk factor for AAS with postoperative oxygenation impairment.

Nomogram and risk calculator for severe hypoxemia after heart valve surgery

Background

Hypoxemia is a very common issue in patients undergoing heart valve surgery (HVS), related to poor clinical outcomes. However, studies on severe hypoxemia (SH) after HVS have not been reported. The aims of this study were to identify predictors for SH in patients undergoing HVS and to develop and validate a risk prediction model.

Methods

Patients undergoing HVS between 2016 and 2019 in a cardiovascular center were enrolled and were assigned to training and validation sets by a 7:3 ratio. Based on whether patients developed SH, they were divided into two groups. By univariate and multivariate analysis, predictors for SH were identified. Based on the predictors and logistic rule, a nomogram and a risk calculator were generated. The model was evaluated using calibration, discrimination and clinical utility.

Results

The incidence rates of SH, moderate hypoxemia and mild hypoxemia were respectively 2.4, 23.9, and 58.2%. By multivariate analysis, seven independent risk factors for SH after HVS were identified, including body mass index, chronic obstructive pulmonary disease, renal insufficiency, white blood cell count, serum globulin, cardiopulmonary bypass time, and surgical types. The logistic model demonstrated satisfactory discrimination, calibration and clinical utility in both the training and validation sets. A nomogram and a risk calculator based on the logistic model were generated for easy application. Risk stratification was performed and three risk intervals were defined according to the nomogram and clinical practice. In addition, compared to patients without SH, patients with SH had significantly poorer clinical outcomes.

Conclusions

Postoperative hypoxemia was prevalent after HVS, related to poor clinical outcomes. A logistic model including seven independent predictors for SH after HVS were established and validated, which demonstrated satisfactory discrimination, calibration and clinical utility. The results of this study may provide help to individualized risk assessment, early prevention and perioperative management.

Incidence, Risk Factors, and Outcomes of Severe Hypoxemia After Cardiac Surgery

Background

Hypoxemia is common in patients undergoing cardiac surgery, however, few studies about severe hypoxemia (SH) after cardiac surgery exist. The objectives of this study were to clarify the incidence, risk factors, and outcomes of SH after cardiac surgery.

Methods

Patients undergoing cardiac surgery from 2016 to 2019 in a single center were enrolled and were divided into two groups based on whether postoperative SH developed. Independent risk factors for SH were identified by univariate and multivariate analysis. Model selection statistics were applied to help determine the most parsimonious final model.

Results

Severe hypoxemia developed in 222 of the 5,323 included patients (4.2%), was associated with poorer clinical outcomes. Six independent risk factors for SH after cardiac surgery were identified by multivariate analysis, such as surgical types, white blood cell (WBC) count, body mass index (BMI), serum albumin, cardiopulmonary bypass (CPB) time, and intraoperative transfusion of red blood cells (RBCs). After comprehensively considering the discrimination, calibration, and simplicity, the most appropriate and parsimonious model was finally established using four predictors, such as WBC count, BMI, CPB time, and intraoperative transfusion of RBCs. A nomogram and a web-based risk calculator based on the final model were constructed to facilitate clinical practice. Patients were stratified into three risk groups based on the nomogram and clinical practice.

Conclusion

Severe hypoxemia was common after cardiac surgery and was associated with poorer clinical outcomes. A parsimonious final model with good discrimination, calibration, and clinical utility was constructed, which may be helpful for personalized risk assessment and targeted intervention.

Preoperative Nomogram and Risk Calculator for Postoperative Hypoxemia and Related Clinical Outcomes Following Stanford Type A Acute Aortic Dissection Surgery

Background

Hypoxemia is a common complication after Stanford type A acute aortic dissection surgery (AADS), however, few studies about hypoxemia after AADS exist. The aims of this study were to identify independent risk factors for hypoxemia after AADS and to clarify its association with clinical outcomes.

Methods

Patients undergoing AADS from 2016 to 2019 in our hospital were identified and used as a training set. Preoperative variables were first screened by univariate analysis and then entered into a multivariate logistic regression analysis to identify independent risk factors. A nomogram and an online risk calculator were constructed based on the logistic model to facilitate clinical practice and was externally validated in an independent dataset.

Results

Severe hypoxemia developed in 119 of the 492 included patients (24.2%) and poorer clinical outcomes were observed in these patients. Five independent risk factors for severe hypoxemia after AADS were identified by multivariate analysis, including older age, smoking history, renal insufficiency, higher body mass index, and white blood cell count. The model showed good calibration, discrimination, and clinical utility in the training set, and was well validated in the validation set. Risk stratification was performed and three risk groups were defined as low, medium, and high risk groups. Hypertension was identified as an independent risk factor for moderate hypoxemia besides the five predictors mentioned above, and renal insufficiency was not significant for mild hypoxemia by multivariate analysis. In addition, although frozen elephant trunk was associated with increased risk of postoperative hypoxemia in the univariate analysis, frozen elephant trunk was also not identified as an independent risk factor for postoperative hypoxemia in the multivariate analysis.

Conclusion

Hypoxemia was frequent following AADS, related to poorer clinical outcomes. Predictors were identified and a nomogram as well as an online risk calculator predicting severe hypoxemia after AADS was developed and validated, which may be helpful for risk estimation and perioperative management.

Is obstructive sleep apnoea associated with hypoxaemia and prolonged ICU stay after type A aortic dissection repair? A retrospective study in Chinese population

Background

Although obstructive sleep apnoea (OSA) is prevalent among patients with aortic dissection, its prognostic impact is not yet determined in patients undergoing major vascular surgery. We aimed to investigate the association of OSA with hypoxaemia and with prolonged intensive care unit (ICU) stay after type A aortic dissection (TAAD) repair.

Methods

This retrospective study continuously enrolled 83 patients who underwent TAAD repair from January 1 to December 31, 2018. OSA was diagnosed by sleep test and defined as an apnoea hypopnea index (AHI) of ≥ 15/h, while an AHI of > 30/h was defined severe OSA. Hypoxaemia was defined as an oxygenation index (OI) of < 200 mmHg. Prolonged ICU stay referred to an ICU stay of > 72 h. Receiver operating characteristic curve analysis was performed to evaluate the predictive value of postoperative OI for prolonged ICU stay. Multivariate logistic regression was performed to assess the association of OSA with hypoxaemia and prolonged ICU stay.

Results

A total of 41 (49.4%) patients were diagnosed with OSA using the sleep test. Hypoxaemia occurred postoperatively in 56 patients (67.5%). Postoperatively hypoxaemia developed mostly in patients with OSA (52.4% vs. 83.0%, p = 0.003), and particularly in those with severe OSA (52.4% vs. 90.5%, p = 0.003). The postoperative OI could fairly predict a prolonged ICU stay (area under the receiver-operating characteristic curve, 0.72; 95% confidence intervals [CI] 0.60–0.84; p = 0.002). Severe OSA was associated with both postoperative hypoxaemia (odds ratio [OR] 6.65; 95% CI 1.56–46.26, p = 0.008) and prolonged ICU stay (OR 5.58; 95% CI 1.54–20.24, p = 0.009).

Conclusions

OSA was common in patients with TAAD. Severe OSA was associated with postoperative hypoxaemia and prolonged ICU stay following TAAD repair.

Association of body mass index with outcomes after thoracic endovascular aortic repair in the vascular quality initiative

OBJECTIVE

Although several studies have evaluated the impact of obesity on outcomes after abdominal aortic aneurysm repair, literature examining this association in thoracic endovascular aortic repair (TEVAR) is sparse. Here, we use a multi-institutional, international database to assess the role of body mass index (BMI) on adverse outcomes in patients who underwent TEVAR for descending thoracic aortic aneurysms (DTAA) and type B dissections (TBD).

METHODS

A retrospective review of all patients who underwent TEVAR for DTAA or TBD from August 2014 to August 2020 was performed. Patients who were underweight (BMI <18.5 kg/m²) or obese (BMI ≥30 kg/m²) were compared with those of normal weight (≥18.5 to <30 kg/m²). Adjustment for confounding was done with multivariable logistic regression or Cox proportional hazards regression as appropriate for studying postoperative or 1-year outcomes. Primary outcomes were 30-day and 1-year mortality. Other outcomes included any postoperative complication, stroke, and spinal cord ischemia.

RESULTS

A total of 3423 participants were included in the study, of whom 3.3% (n = 113) were underweight, 65.9% (n = 2253) had normal weight, and 30.8% (n = 1053) were obese. Compared with normal weight, there was no significant difference in 30-day mortality in underweight patients (odds ratio [OR], 1.81; 95% confidence interval [CI], 0.80-4.14; P = .156). Obese patients who underwent TEVAR for TBD had a 2.7-fold increase in the odds of 30-day mortality compared with normal weight (OR, 2.67; 95% CI, 1.52-4.68; P = .001). Obese and normal weight patients with DTAA had equivalent odds of 30-day mortality (OR, 1.32; 95% CI, 0.79-2.23; P = .292). The adjusted hazard of 1-year mortality was 2-fold higher in underweight patients compared with normal weight (hazard ratio, 2.15; 95% CI, 1.41-3.29; P < .001), driven by a higher risk of mortality among patients with thoracic aortic aneurysm (OR, 2.62; 95% CI, 1.63-4.21; P < .001). There was no significant difference in 1-year mortality risk between normal weight and obesity in both DTAA (OR, 0.77; 95% CI, 0.54-1.09; P = .146) and TBD (OR, 1.26; 95% CI, 0.85-1.86; P = .248).

CONCLUSIONS

In this study, obese patients who underwent TEVAR for DTAA had comparable 30-day and 1-year mortality risk as normal weight individuals. Obese patients who underwent TEVAR for TBD demonstrated a 2.7-fold increase in the odds of 30-day mortality, but equivalent mortality risk as normal weight patients at 1 year. TEVAR represents a safe minimally invasive option for treatment of DTAA in obese patients. Future work should be directed toward minimizing perioperative mortality among patients with TBD to optimize TEVAR outcomes.

Inhaled nitric oxide reduces the intrapulmonary shunt to ameliorate severe hypoxemia after acute type A aortic dissection surgery

BACKGROUND

To assess the relationship between the intrapulmonary shunt and PaO₂/FiO₂ in severe hypoxemic patients after acute type A aortic dissection (ATAAD) surgery and to evaluate the effect of inhaled nitric oxide (iNO) on intrapulmonary shunt.

METHODS

Postoperative ATAAD patients with PaO₂/FiO₂ ≤ 150 mmHg were enrolled. Intrapulmonary shunt was calculated from oxygen content of different sites (artery [CaO₂], mixed venous [CvO₂], and alveolar capillary [CcO₂]) using the Fick equation, where intrapulmonary shunt = (CcO₂-CaO₂)/(CcO₂-CvO₂). Related variables were measured at baseline (positive end expiratory pressure [PEEP] 5 cm H₂O), 30 min after increasing PEEP (PEEP 10 cm H₂O), 30 min after 5 ppm iNO therapy (PEEP 10 cm H₂O + iNO), and 30 min after decreasing PEEP (PEEP 5 cm H₂O + iNO).

RESULTS

A total of 20 patients were enrolled between April 2019 and December 2019. Intrapulmonary shunt and PaO₂/FiO₂ were correlated in severe hypoxemic, postoperative ATAAD patients (adjusted R² = 0.467, p < 0.001). A mixed model for repeated measures revealed that iNO, rather than increasing PEEP, significantly decreased the intrapulmonary shunt (by 15% at a PEEP of 5 cm H₂O and 16% at a PEEP of 10 cm H₂O, p < 0.001 each) and increased PaO₂/FiO₂ (by 63% at a PEEP of 5 cm H₂O and 65% at a PEEP of 10 cm H₂O, p < 0.001 each). After iNO therapy, the decrement of intrapulmonary shunt and the increment of PaO₂/FiO₂ were also correlated (adjusted R² = 0.375, p < 0.001).

CONCLUSIONS

This study showed that intrapulmonary shunt and PaO₂/FiO₂ were correlated in severe hypoxemic, postoperative ATAAD patients. Furthermore, iNO, rather than increasing PEEP, significantly decreased the intrapulmonary shunt to improve severe hypoxemic conditions.

Perioperative risk factors for delayed extubation after acute type A aortic dissection surgery

Background

Delayed extubation after cardiac surgery is associated with high morbidity and mortality, increased intensive care unit length of stay, and healthcare cost. Acute type A aortic dissection (ATAAD) generally results in prolonged mechanical ventilation due to the complexity of surgical management and some postoperative complications. This study aimed to elucidate the perioperative risk factors for delayed extubation in patients undergoing ATAAD surgery.

Methods

A retrospective cohort study including 239 patients who were diagnosed with ATAAD and underwent emergency surgery from October 2004 to January 2018 was performed. The potential perioperative risk factors for delayed extubation were collected. This study defined delayed extubation as the time to commence extubation being greater than 48 hours. The clinical data were analyzed with univariate and multivariate analyses to identify risk factors for delayed extubation following ATAAD surgery.

Results

The incidence of delayed extubation was 48.5% (n=116). Multiple logistic regression analysis showed perioperative risk factors for delayed extubation included preoperative cardiac tamponade [odds ratio (OR) 3.94, 95% confidence interval (CI) 1.39–11.17, P=0.010], central arterial cannulation (ascending aorta and proximal aortic arch) for cardiopulmonary bypass (CPB) (OR 4.04, 95% CI: 1.03–15.91, P=0.046), postoperative stroke (OR 10.58, 95% CI: 2.65–42.25, P=0.001), postoperative renal dysfunction that required temporary hemodialysis (OR 6.60 95% CI: 1.97–22.11, P=0.002), and re-exploration to stop bleeding (OR 2.65, 95% CI: 1.00–6.99, P=0.050).

Conclusions

Preoperative cardiac tamponade, central arterial cannulation for CPB, postoperative stroke, postoperative renal dysfunction that required temporary hemodialysis, and re-exploration to stop bleeding are perioperative risk factors for delayed extubation. Identification of the potential risk factors for delayed extubation may help optimize the perioperative management and improve postoperative outcomes of patients undergoing ATAAD surgery.

Risk factors for and predictive nomogram of postoperative hypoxaemia in elderly patients with femoral neck fractures

Objective

To investigate the related risk factors and predictive nomogram of postoperative hypoxaemia in elderly patients with femoral neck fractures.

Methods

This study included patients aged ≥65 years who underwent surgical treatment of acute femoral neck fractures. Univariate and multivariate logistic analyses were performed to determine the incidence of and risk factors for postoperative hypoxaemia. A predictive nomogram was constructed based on the multivariable model. Using the bootstrap method, discrimination was determined by the C-index and calibration plot.

Results

The logistic regression analysis showed that the anaesthesia type, surgical procedure, American Society of Anesthesiologists (ASA) classification, preoperative hypoxaemia occurrence, and age were independent predictors of development of postoperative hypoxaemia. The predictive formula for hypoxaemia was established as follows: hypoxaemia=−0.8668×spinal anaesthesia (whether)+0.1162×nerve anaesthesia (whether)+1.9555×plate/screw fixation (whether)+1.4950×hip replacement (whether)+0.4883×ASA classification+1.7153×preoperative oxygenation index+0.1608×age. With the bootstrap method, the prediction curve fit well with the ideal curve, suggesting that the prediction curve constructed in this study has good predictive ability.

Conclusions

Anaesthesia type, surgical procedure, ASA classification, preoperative hypoxaemia occurrence, and age were risk factors for postoperative hypoxaemia in elderly patients with femoral neck fractures. The predictive nomogram was designed for preoperative assessment of the risk of postoperative hypoxaemia by calculating the risk score.

Obesity is a risk factor for preoperative hypoxemia in Stanford A acute aortic dissection

Obese individuals are apt to develop Stanford A acute aortic dissection (AAD) complicated with acute lung injury (ALI), but the mechanism is still not well defined. We aim to investigate whether oxidative stress and inflammatory are involved in the aortic dissection lung injury caused by obesity.Seventy-nine patients were categorized into AAD with obesity group (n = 17) and AAD without obesity group (n = 62) according to body mass index (BMI). Inflammatory reactions including interleukin 1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-6, C-reactive protein (CRP) and white blood cell (WBC) count, and oxidative stress including malondialdehyde (MDA), superoxide dismutase were determined using enzyme-linked immunosorbent assays and chemiluminescence. All the patients received ascending aorta replacement combined with total arch replacement and stented elephant trunk. The postoperative complications were recorded.The incidence of preoperative hypoxemia (94.1% vs 35.5%, P < .01) and postoperative ALI (88.2% vs 40.3%, P < .01) in obese patients was significantly higher than that in non-obese patients. Besides, the ICU stay (119.2 ± 59.2 vs 87.8 ± 31.2 h, P < .01) and hospitalization duration (18.8 ± 8.5 vs 14.3 ± 8.1d, P = .048) were increased in the obese patients with AAD. The expression of IL-1β, TNF-α, IL-6, CRP, and WBC was remarkably increased (P < .01) in obese group compared with non-obese group.Oxidative stress and inflammatory response may be involved in the process of ALI of aortic dissection caused by obesity, which provides new ideas for the treatment of ALI of the aortic dissection.

Outcomes and risk factors of postoperative hepatic dysfunction in patients undergoing acute type A aortic dissection surgery

Background

Postoperative hepatic dysfunction (HD) increases the morbidity and mortality risk after cardiac surgery; however, only a few studies have specifically focused on acute type A aortic dissection (AAAD) surgery. We explored the possible risk factors and outcomes of early postoperative HD in patients with AAAD undergoing surgery.

Methods

All patients who underwent AAAD surgery at our institution from April 2015 to April 2017 were retrospectively evaluated. Postoperative model for end-stage liver disease (MELD) score was used to define HD. Independent risk factors for HD were determined by multivariate logistic analysis.

Results

Two hundred fifteen patients with AAAD met the inclusion criteria. The incidence rate of early postoperative HD was 60.9%, and the rate of in-hospital mortality was 16.8%. Patients with a high postoperative MELD score had longer mechanical ventilation time, longer durations of intensive care unit (ICU) stay, and higher in-hospital mortality. During the postoperative period, patients with AAAD complicated by HD needed continuous renal replacement therapy (CRRT), reintubation, tracheostomy, and blood transfusion more frequently. Aortic cross clamp (ACC) time [per 10 min higher; odds ratio (OR): 1.216, 95% confidence interval (CI): 1.017-1.454, P=0.032], postoperative leucocytes (per 2×10⁹/L higher; OR: 1.161, 95% CI: 1.018-1.324, P=0.026), postoperative respiratory dysfunction (OR: 3.176, 95% CI: 1.293-7.803, P=0.012), and postoperative low cardiac output syndrome (LCOS) (OR: 12.663, 95% CI: 1.432-111.998, P=0.022) were independent risk factors associated with HD in patients undergoing AAAD surgery.

Conclusions

Postoperative HD prolongs mechanical ventilation time and ICU stay, and is associated with increased in-hospital mortality among patients who undergo AAAD surgery. Several factors are associated with a high postoperative MELD score.

Oxygenation impairment in patients with acute aortic dissection is associated with disorders of coagulation and fibrinolysis: a prospective observational study

Background

Stanford type-A acute aortic dissection (AAD) is typically accompanied by oxygenation impairment before surgery. In addition, inflammation, coagulation and fibrinolysis also impair blood oxygenation. However, our understanding of the concentration of these factors in bronchoalveolar lavage fluid (BALF) has not been reported. The objective of the study was to investigate the impact of preoperative acute lung injury (ALI) on postoperative oxygenation impairment and to explore the effect of coagulation and fibrinolysis in blood and BALF.

Methods

This investigation utilized a prospective observational study design, which was registered at www.clinicaltrials.gov (identifier NCT01894334). The study included 53 patients undergoing surgery for Stanford type-A AAD at an academic hospital in China between October 2013 and July 2014. Preoperative ALI was identified according to the oxygenation index calculated by the PaO₂/FiO₂ ratio. The subjects were divided into the ALI group (oxygenation index ≤300 mmHg) or the control group (oxygenation index >300 mmHg). The primary outcome was patient oxygenation index, while secondary outcomes were concentrations of tissue factor (TF), tissue factor pathway inhibitor (TFPI), and plasminogen activator inhibitor-1 (PAI-1) in serum and BALF.

Results

The incidence of preoperative ALI for Stanford type-A AAD patients was 41.5%. Stanford type-A AAD patients with preoperative ALI had a lower postoperative oxygenation index (104.6±31.7 vs. 248.7±48.0 mmHg, P<0.001), higher concentrations of TF in serum and BALF (F=133.67, P<0.001; F=68.14, P<0.001), higher concentrations of TFPI in serum and BALF (F=31.98, P<0.001; F=45.58, P<0.001), and higher concentrations of PAI-1 in serum and BALF (F=213.88, P<0.001; F=107.95, P<0.001) when compared with those without preoperative ALI. Type-A AAD patients also showed a greater loss of blood (1,524±458 vs. 1,175±327 mL, P=0.040), longer mechanical ventilation time in the ICU (27.24±8.37 vs. 17.33±7.36 h, P<0.001), longer total stay in the ICU (42.27±10.85 vs. 33.45±9.05 h, P=0.002), and longer total hospital stay (17.77±5.00 vs. 13.48±3.97 days, P=0.001). Multivariate linear regression analysis indicated that preoperative PAI-1 in BALF, and TF in both serum and BALF were significantly associated with preoperative oxygenation impairment in patients with Stanford type-A AAD.

Conclusions

Preoperative ALI caused more serious postoperative oxygenation impairment for Stanford type-A AAD, and coagulation and fibrinolysis appear to play critical roles in this process. Preoperative PAI-1 in BALF and TF in both serum and BALF were significant factors related to the occurrence of preoperative oxygenation impairment for Stanford type-A AAD.

Increased risk for the development of postoperative severe hypoxemia in obese women with acute type a aortic dissection

Background

The purpose of this study is to identify the risk factors for postoperative severe hypoxemia after surgery for acute type A aortic dissection.

Methods

This was a single-center retrospective study including 112 consecutive patients undergoing urgent aortic arch surgery for acute type A aortic dissection between December 2016 and April 2017 at Beijing Anzhen Hospital.

Results

Multivariate logistic regression analysis identified female (OR, 12.978; 95% CI, 3.332 to 50.546; p < 0.001) and increased body mass index (OR, 1.473; 95% CI, 1.213 to 1.789; p < 0.001) as independent predictors of postoperative severe hypoxemia in patients with acute type A aortic dissection.

Conclusions

Obesity and female were independent risk factors for postoperative severe hypoxemia in patients with acute type A aortic dissection. More attention should be paid to preventing postoperative severe hypoxemia in obese women with acute type A aortic dissection.

Initial clinical impact of inhaled nitric oxide therapy for refractory hypoxemia following type A acute aortic dissection surgery

BACKGROUND

To evaluate the effect of inhaled nitric oxide (iNO) therapy on oxygenation and clinical outcomes in patients with refractory hypoxemia after surgical reconstruction for acute type A aortic dissection (TAAD).

METHODS

A before-and-after interventional study was conducted in patients with refractory hypoxemia after surgical reconstruction for TAAD. Postoperative refractory hypoxemia was defined as a persistent PaO₂/FiO₂ ratio ≤100 mmHg despite conventional therapy. From January to November 2016, conventional treatment was carried out for refractory hypoxemia. From December 2016 to October 2017, on the basis of conventional therapy, we explored the use of iNO to treat refractory hypoxemia.

RESULTS

Fifty-three TAAD patients with refractory hypoxemia were enrolled in this study. Twenty-seven patients received conventional treatment (conventional group), while the remaining 26 patients received iNO therapy. The PaO₂/FiO₂ ratio was significantly higher in the iNO group after treatment than in the conventional group when analyzed over the entire 72 hours. The duration of invasive mechanical ventilation was significantly reduced in the iNO group (69.19 vs. 104.56 hours; P=0.003). Other outcomes, such as mortality (3.85% vs. 7.41%, P=1.000), intensive care unit (ICU) duration (9.88 vs. 12.36 days, P=0.059) and hospital stay (16.88 vs. 20.76 days, P=0.060), were not significantly different between the two groups.

CONCLUSIONS

iNO therapy might play an ameliorative role in patients with refractory hypoxemia after surgical reconstruction for TAAD. This therapy may lead to sustained improvement in oxygenation and reduce the duration of invasive mechanical ventilation.

Nomogram for the prediction of postoperative hypoxemia in patients with acute aortic dissection

BACKGROUND

Postoperative hypoxemia is quite common in patients with acute aortic dissection (AAD) and is associated with poor clinical outcomes. However, there is no method to predict this potentially life-threatening complication. The study aimed to develop a regression model in patients with AAD to predict postoperative hypoxemia, and to validate it in an independent dataset.

METHODS

All patients diagnosed with AAD from December 2012 to December 2017 were retrospectively screened for potential eligibility. Preoperative and intraoperative variables were included for analysis. Logistic regression model was fit by using purposeful selection procedure. The original dataset was split into training and validating datasets by 4:1 ratio. Discrimination and calibration of the model was assessed in the validating dataset. A nomogram was drawn for clinical utility.

RESULTS

A total of 211 patients, involving 168 in non-hypoxemia and 43 in hypoxemia group, were included during the study period (incidence: 20.4%). Duration of mechanical ventilation (MV) was significantly longer in the hypoxemia than non-hypoxemia group (41(10.5140) vs. 12(3.75,70.25) hours; p = 0.002). There was no difference in the hospital mortality rate between the two groups. The purposeful selection procedure identified 8 variables including hematocrit (odds ratio [OR]: 0.89, 95% confidence interval [CI]: 0.80 to 0.98, p = 0.011), PaO₂/FiO₂ ratio (OR: 0.99, 95% CI: 0.99 to 1.00, p = 0.011), white blood cell count (OR: 1.21, 95% CI: 1.06 to 1.40, p = 0.008), body mass index (OR: 1.32, 95% CI: 1.15 to 1.54; p = 0.000), Stanford type (OR: 0.22, 95% CI: 0.06 to 0.66; p = 0.011), pH (OR: 0.0002, 95% CI: 2*10^- 8 to 0.74; p = 0.048), cardiopulmonary bypass time (OR: 0.99, 95% CI: 0.98 to 1.00; p = 0.031) and age (OR: 1.03, 95% CI: 0.99 to 1.08; p = 0.128) to be included in the model. In an independent dataset, the area under curve (AUC) of the prediction model was 0.869 (95% CI: 0.802 to 0.936). The calibration was good by visual inspection.

CONCLUSIONS

The study developed a model for the prediction of postoperative hypoxemia in patients undergoing operation for AAD. The model showed good discrimination and calibration in an independent dataset that was not used for model training.

Independent factors related to preoperative acute lung injury in 130 adults undergoing Stanford type-A acute aortic dissection surgery: a single-center cross-sectional clinical study

Background

Previous retrospective study suggested that acute lung injury (ALI) is frequent (78.49%) in patients undergoing aortic dissection surgery, and accompanied by a number of untoward consequences, and even induces death.

Methods

This prospective single-center cross-sectional study, registered in the ClinicalTrials.gov (Identifier: NCT01894334), assessed the preoperative clinical variables and serological results from 130 adult patients scheduled for Stanford type-A acute aortic dissection (AAD) surgery at Beijing Anzhen Hospital between January 2013 and July 2014. Exclusion criteria included patients with coronary heart disease, severe heart failure, severe cardiac tamponade and severe nervous system abnormalities. Preoperative ALI was identified according to oxygenation index (OI) calculated by PaO₂/FiO₂ ratio after anesthesia induction, and all the patients were divided into two groups: non-ALI (OI ≥300 mmHg) and ALI (OI <300 mmHg). The primary endpoint was the incidence of preoperative ALI. The secondary endpoints were the independent factors affecting the occurrence of preoperative ALI.

Results

The incidence of preoperative ALI was 53.8%. With adjusted multiple logistic regression analysis, age [odds ratio (OR) 1.14, confidence interval (CI), 1.06-1.22; P=0.0002], body mass index (BMI) (OR 1.31, CI, 1.09-1.56; P=0.0033), preoperative diastolic blood pressure (DBP) (OR 0.94, CI, 0.89-0.99; P=0.0109), interleukin-6 (IL-6) (OR 1.03, 95% CI, 1.01-1.06; P=0.0053), and prostaglandin I₂/thromboxane B₂ (PGI₂/TXB₂) ratio (OR 0.25, 95% CI, 0.09-0.67; P=0.0055) were significantly related to the occurrence of preoperative ALI. The decreased risk of ALI was related to the preoperative DBP value up to 44 mmHg (OR 0.935, 95% CI, 0.895-0.978; P=0.0033). Interactions analysis revealed that serum lactic acid mediated the relationship between DBP and ALI before Stanford type-A AAD surgery.

Conclusions

In adults undergoing Stanford type-A AAD surgery, the incidence of preoperative ALI was 53.8%, and age, BMI, preoperative DBP, IL-6, and PGI2/TXB2 ratio were independent factors related to the occurrence of pre-operative ALI. Trial Registration: ClinicalTrials.gov, Identifier: NCT01894334.

Oxygenation impairment after total arch replacement with a stented elephant trunk for type-A dissection

OBJECTIVE

To study the risk factors of oxygenation impairment in patients with type-A acute aortic dissection who underwent total arch replacement with a stented elephant trunk.

METHODS

In this study, 169 consecutive patients were enrolled who were diagnosed with type-A acute aortic dissection and underwent a total arch replacement procedure at the Qilu Hospital of Shandong University between January 2015 and February 2017. Postoperative oxygenation impairment was defined as arterial oxygen partial pressure/inspired oxygen fraction ≤ 200 with positive end expiratory pressure ≥ 5 cm H₂O that occurred within 72 hours of surgery. Perioperative clinical characteristics of all patients were collected and univariable analyses were performed. Risk factors associated with oxygenation impairment identified by univariable analyses were included in the multivariable regression analysis.

RESULTS

The incidence of postoperative oxygenation impairment was 48.5%. Postoperative oxygenation impairment was associated with prolonged mechanical ventilation time, intensive care unit stay, and hospital stay. Multivariable regression analysis demonstrated that body mass index (odds ratio [OR], 1.204; 95% confidence interval [CI], 1.065-1.361; P = .003), preoperative oxygenation impairment (OR, 9.768; 95% CI, 4.159-22.941; P < .001), preoperative homocysteine (OR, 1.080; 95% CI, 1.006-1.158; P = .032), circulatory arrest time (OR, 1.123; 95% CI, 1.044-1.207; P = .002), and plasma transfusion (OR, 1.002; 95% CI, 1.001-1.003; P = .002) were significantly associated with postoperative oxygenation impairment.

CONCLUSIONS

Postoperative oxygenation impairment is a common complication of surgery for type-A acute aortic dissection. Body mass index, preoperative oxygenation impairment, preoperative homocysteine, circulatory arrest time, and plasma transfusion were independent risk factors for oxygenation impairment after a total arch replacement procedure.

Impact of Presurgical Mild Acute Respiratory Distress Syndrome on Surgical Mortality After Surgical Repair of Acute Type A Aortic Dissection

To evaluate the impact of presurgical mild acute respiratory distress syndrome (ARDS) on surgical mortality in patients undergoing surgical repair of acute type A aortic dissection by means of deep hypothermic circulatory arrest (DHCA) in a single-center, retrospective study.From January 2011 to December 2015, 333 eligible patients were divided into either a mild-ARDS group (n = 136) or a no-ARDS group (n = 197). The definition of mild ARDS referred to the recent revision of ARDS definition (Berlin criteria). The surgical mortality and major postoperative morbidity were investigated and analyzed.A total of 136 patients developed presurgical mild ARDS, with an incidence of 40.8%. No significant difference emerged between the 2 groups in major postoperative morbidity except for pulmonary complications. Multivariate logistic regression displayed that the risk of postoperative pulmonary complications in patients with presurgical mild ARDS was 4.25 times that in patients without presurgical ARDS (OR = 4.25, 95% CI 2.05-7.72). Twenty-four patients died after surgery, with significantly higher surgical mortality in the mild-ARDS group compared with the no-ARDS group (12.5% versus 3.6%, P = 0.002). Kaplan-Meier curves showed a poor surgical survival in the mild-ARDS group (χ²=12.958, Log-Rank P < 0.001). And Cox regression revealed the hazard ratio for surgical mortality in the mild-ARDS group compared with the no-ARDS group was 2.52 (95%CI 1.41-5.32, P = 0.016).Presurgical mild ARDS increased postoperative respiratory morbidity, and then increased surgical mortality after surgical repair of acute type A aortic dissection by means of DHCA.

Risk factors for hypoxemia following surgical repair of acute type A aortic dissection

Objectives

To identify the risk factors for hypoxaemia following surgical repair of acute type A aortic dissection.

Methods

This was a retrospective study of patients treated between October 2013 and December 2014 at the Department of Cardiovascular Surgery, Anzhen Hospital, China. Univariable and multivariable analyses were performed on the clinical data of 160 patients with acute type A dissection and who underwent ascending aortic and arch replacement under deep hypothermic circulatory arrest.

Results

Hypoxaemia occurred in 30% (48/160) of patients (age: 49 ± 7.9 years; 40 males, 83.3%). The duration of ventilation and the lengths of intensive care unit and hospital stays were significantly longer in patients with hypoxemia (77.9 ± 56.0 vs 16.5 ± 11.5 h, P < 0.0001; 6.0 ± 2.3 vs 2.0 ± 1.2 days, P = 0.001; 18.1 ± 6.3 vs 13.5 ± 4.7 days, P = 0.0012; respectively). The difference in operative mortality was not statistically significant between the hypoxaemia and non-hypoxaemia groups (6.25% vs 3.57%, P = 0.351). The independent risk factors of postoperative hypoxaemia were time from symptom onset to surgery ≤72 h [odds ratio, 3.63; 95% confidence interval, 1.31-10.02; P = 0.013], preoperative PaO2/FiO2 ≤300 (odds ratio, 15.30; 95% CI, 5.52-42.43; P < 0.001), preoperative white blood cell count >15 000/μl (odds ratio, 9.79; 95% CI, 2.47-38.87; P = 0.001); and deep hypothermic circulatory arrest time >25 min (odds ratio, 3.26; 95% CI, 1.18-8.99; P = 0.023).

Conclusions

Time from symptom onset to surgery ≤72 h, preoperative PaO2/FiO2 ≤300, white blood cell count >15 000/μl and deep hypothermic circulatory arrest time >25 min were found to be independently associated with hypoxaemia after surgery for acute type A aortic dissection.

Independent risk factors for hypoxemia after surgery for acute aortic dissection

Objectives:

To determine risk factors associated with postoperative hypoxemia after surgery for acute type A aortic dissection.

Methods:

We retrospectively analyzed the clinical data of 192 patients with acute type A aortic dissection who underwent surgery in Qingdao Municipal Hospital, Medical College of Qingdao University, Qingdao, China between January 2007 and December 2013. Patients were divided into hypoxemia group (n=55) [arterial partial pressure of oxygen (PaO₂)/fraction of inspired oxygen (FiO₂) ≤200 mm Hg] and non-hypoxemia group (n=137) [PaO₂/FiO₂ >200 mm Hg]. Perioperative clinical data were analyzed and compared between the 2 groups.

Results:

The incidence of postoperative hypoxemia after surgery for acute aortic dissection was 28.6% (55/192). Perioperative death occurred in 13 patients (6.8%). Multivariate regression identified body mass index (BMI) >25 kg/m² (OR=21.929, p=0.000), deep hypothermic circulatory arrest (DHCA) (OR=11.551, p=0.000), preoperative PaO₂/FiO₂ ≤300 mm Hg (OR=7.830, p=0.000) and blood transfusion >6U in 24 hours postoperatively (OR=12.037, p=0.000) as independent predictors of postoperative hypoxemia for patients undergoing Stanford A aortic dissection surgery.

Conclusion:

Our study demonstrated that BMI >25 kg/m², DHCA, preoperative PaO₂/FiO₂ ≤300 mm Hg, and blood transfusion in 24 hours postoperatively >6U were independent risk factors of the hypoxemia after acute type A aortic dissection aneurysm surgery.

A Retrospective Observational Study to Assess Prescription Pattern in Patients with Type B Aortic Dissection and Treatment Outcome

Aortic dissection is a life-threatening condition. However, the use of medication to treat it remains unclear in our population, particularly in patients with a type B aortic dissection (TBAD) who do not receive surgery. This retrospective cohort study evaluated antihypertensive prescription patterns and outcomes in patients with nonsurgical TBAD. We reviewed the hospital records of patients with TBAD at a medical center in Taiwan from January 2008 to June 2013 to assess the baseline information, prescribing pattern, event rate, and clinical effectiveness of different antihypertensive treatment strategies. A Cox proportional hazards model was used to estimate outcomes in different antihypertensive strategies. The primary endpoints were all-cause mortality and hospital admission for an aortic dissection. We included 106 patients with a mean follow-up period of 2.75 years. The most common comorbidity was hypertension followed by dyslipidemia and diabetes mellitus. Study endpoints mostly occurred within 6 months after the index date. Over 80% of patients received dual or triple antihypertensive strategies. Patients treated with different treatment strategies did not have a significantly increased risk of a primary outcome compared with those treated with a monotherapy. We found no significant difference in the primary outcome following the use of different antihypertensive medication regimes.

Noninvasive Positive-Pressure Ventilation in Treatment of Hypoxemia After Extubation Following Type-A Aortic Dissection

OBJECTIVES

To assess the efficacy of noninvasive positive-pressure ventilation (NPPV) in improving hypoxemia after extubation for Stanford type-A aortic dissection and to compare NPPV using a mask or a helmet.

DESIGN

Prospective, interventional study.

SETTING

Department of Cardiac Surgery of the Beijing Anzhen Hospital, a tertiary university hospital.

PARTICIPANTS

Patients experiencing hypoxemia within 24 hours after extubation for Stanford type-A aortic dissection.

INTERVENTIONS

The patients were divided into the following 3 groups: high-flux inhalation of oxygen with a Venturi mask (control patients), NPPV with a mask (mask group), and NPPV with a helmet (helmet group) (n = 25/group).

MEASUREMENTS AND MAIN RESULTS

Data for blood gas analysis, vital signs, heart function, and complications were collected before the treatment, after 1 and 6 hours of treatment, and at the end of treatment. The oxygen partial pressure/fraction of inspired oxygenation index or PaO₂/FIO₂ ratio and the oxygen partial pressure were higher and carbon dioxide partial pressure was lower in the mask and helmet groups compared with that of control patients. Compared with control patients and the mask group, the helmet group showed a slower heart rate, lower average arterial pressure, and improved left ventricular ejection fraction, leading to a lower incidence of reintubation and a shorter hospital stay.

CONCLUSIONS

NPPV with a helmet may quickly improve oxygen partial pressure, decrease carbon dioxide partial pressure, decrease the reintubation rate, and effectively shorten the hospital stay after extubation for Stanford type-A aortic dissection.

Effects of Noninvasive Positive-Pressure Ventilation with Different Interfaces in Patients with Hypoxemia after Surgery for Stanford Type A Aortic Dissection

Background

Hypoxemia is a severe perioperative complication that can substantially increase intensive care unit and hospital stay and mortality. The aim of this study was to determine the effects of non-invasive positive-pressure ventilation (NIPPV) in patients with hypoxemia after surgery for Stanford type A aortic dissection, and to compare the effects of helmet and mask NIPPV.

Material/Methods

We recruited 40 patients who developed hypoxemia within 24 h after extubation after surgery for Stanford type A aortic dissection in the Beijing Anzhen Hospital. The patients were randomly divided into the helmet and mask NIPPV groups. The primary endpoints were blood oxygenation levels at 1 and 6 h after initiation and at the end of the treatment. The secondary endpoint was patient outcome, including mortality; incidence of pulmonary atelectasis, pneumonia, re-intubation, and sepsis; and length of ICU and hospital stays.

Results

NIPPV improved oxygenation in both groups. Compared with pretreatment levels, the oxygenation index (PaO₂/FiO₂), PaO₂, PaCO₂, and respiratory rate (RR) improved in the initial (0–1 h), maintenance (1–6 h), and end stages of the treatment (P<0.05). Compared with mask ventilation, helmet ventilation better improved pH, PaO₂, SpO₂, PaO₂/FiO_2, and decreased PaCO₂ in the 3 stages (P<0.05). The incidence of major complications, including flatulence, intolerance, and facial pressure sores, was significantly lower with helmet ventilation.

Conclusions

NIPPV effectively improved oxygenation and reduced PaCO₂ in patients who developed hypoxemia soon after extubation following surgery for Stanford type A aortic dissection. Compared with mask NIPPV, helmet NIPPV more rapidly increased PaO₂ and reduced PaCO₂, increased patient tolerance and comfort, and reduced complications.

Risk factors for postoperative hypoxemia in patients undergoing Stanford A aortic dissection surgery

Background

The purpose of this study is to identify the risk factors for postoperative hypoxemia in patients with Stanford A aortic dissection surgery and their relation to clinical outcomes.

Methods

Clinical records of 186 patients with postoperative hypoxemia in Stanford A aortic dissection were analyzed retrospectively. The patients were divided into two groups by postoperative oxygen fraction (PaO2/FiO2):hypoxemia group (N=92) and non-hypoxemia group (N=94).

Results

We found that the incidence of postoperative hypoxemia was 49.5%. Statistical analysis by t-test and χ2 indicated that acute onset of the aortic dissection (p=0.000), preoperative oxygen fraction (PaO2/FiO2) ≤200 mmHg(p=0.000), body mass index (p=0.008), circulatory arrest (CA) time (p=0.000) and transfusion more than 3000 ml(p=0.000) were significantly associated with postoperative hypoxemia. Multiple logistic regression analysis showed that preoperative hypoxemia, CA time and transfusion more than 3000 ml were independently associated with postoperative hypoxemia in Stanford A aortic dissection.

Conclusion

Our results suggest that postoperative hypoxemia is a common complication in patients treated by Stanford A aortic dissection surgery. Preoperative oxygen fraction lower than 200 mmHg, longer CA time and transfusion more than 3000 ml are predictors of postoperative hypoxemia in Stanford A aortic dissection.