Impact of Postinduction Hypotension on Postoperative Outcomes in TAVR Patients: A Retrospective Study

Introduction

Postinduction hypotension (PIH) is a decrease in blood pressure after anesthesia induction and before skin incision. This condition primarily results from the vasodilatory effects of anesthetic drugs, lowering systemic vascular resistance. The incidence of PIH varies widely, from 9% to 60%. Brief episodes of hypotension can restrict blood flow to tissues and lead to serious postoperative complications, increasing the risk of morbidity and mortality. PIH is notable among anesthesiologists as it is both detectable and treatable.

Defining hypotension is inconsistent across studies, complicating the identification of significant clinical events. Absolute thresholds provide one framework, while relative thresholds, such as a 30% drop from baseline, may offer a more personalized assessment of risk. This study examines the link between PIH and postoperative results in patients undergoing transcatheter aortic valve replacement (TAVR), focusing on how different thresholds impact outcomes.

PIH’s influence on postoperative outcomes following TAVR has not been extensively studied. This retrospective cohort analysis investigates the connection between PIH incidence and severity and a set of adverse outcomes, including postoperative mortality, stroke, acute kidney injury (AKI), and myocardial infarction (MI).

Materials and Methods

Approvals

The study received ethical approval from The Second Affiliated Hospital of Zhejiang University School of Medicine (Approval No. 2022–0521, June 26, 2022). Written consent was obtained from participants or their guardians. The study followed STROBE guidelines and adhered to the Declaration of Helsinki principles.

Study Participants

The study included adult patients (age ≥18 years) classified as ASA III–IV, who had TAVR with either general anesthesia (GA) or deep sedation at our institution between January 1, 2020, and February 28, 2023. Exclusion criteria included: (1) TAVR via carotid or apical approaches, (2) use of circulatory assist devices prior to surgery, and (3) missing invasive arterial measurements for over 10 continuous minutes. Data was collected by two independent investigators who were unaware of the study hypothesis, classifying patients into PIH and non-PIH groups based on mean arterial pressure (MAP) after anesthesia induction.

Data Sources and Collection

Data were obtained from the electronic medical records (EMR) and the Docare anesthesia system, covering a variety of patient information, including notes, consultations, lab results, and surgical records.

Preoperative Evaluation

Patients underwent preoperative evaluation by a cardiac team at least one day before TAVR. The study team collected data from these assessments.

Monitoring

We continuously monitored heart rate, invasive blood pressure, ECG, oxygen saturation, and body temperature. Two defibrillator pads were placed for emergency use. Cerebral oxygen saturation was tracked using INVOS 5100c surface pads. Cardiac index, systemic vascular resistance, and stroke volume variation were measured using the ProAQT/Pulsioflex system.

Anesthesia Administration

Patients could choose between GA with intubation or deep sedation based on their condition. For GA, induction involved propofol or etomidate combined with sufentanil or rocuronium. Maintenance used propofol and remifentanil. Deep sedation involved lower doses of propofol and fentanyl with supplementation as needed.

TAVR Procedure

TAVR procedures utilized the transfemoral approach in the cardiac catheterization laboratory. A team comprising cardiologists, surgeons, and anesthesiologists conducted the procedures, each having experience with at least 50 TAVR operations.

Blood Pressure Assessment

Four MAP thresholds were identified through literature review. PIH was defined as a MAP drop exceeding 30% from baseline, lasting over one minute from anesthesia induction until surgery commenced. The study categorized hypotension into three groups: no hypotension, short duration (≤10 minutes), and prolonged (≥10 minutes).

Outcomes

The primary outcome comprised all-cause in-hospital mortality, stroke, AKI, and MI. Secondary outcomes were postoperative delirium, ICU admission, and new-onset postoperative atrial fibrillation.

Statistical Analysis

Continuous variables were reported as means and standard deviations or as medians and percentiles. Categorical variables appeared as counts. We analyzed differences via independent t-tests or Mann-Whitney tests, with the chi-square test for categorical data.

We employed propensity score methods, including inverse probability of treatment weighting (IPTW) and propensity score matching (PSM), to adjust for confounding variables. The matching was achieved at a 1:1 ratio based on propensity scores. For the primary analysis, we estimated the association between PIH and outcomes using log-binomial regression.

Results

Cohort Characteristics

Of 777 patients who underwent TAVR, 643 were included after exclusions. The mean patient age was 74.6 years, with a male percentage of 42.3%. The cohort had a 63.0% incidence of PIH based on a 30% MAP decrease.

A total of 61 patients (9.5%) experienced adverse outcomes: three (0.5%) deaths, 13 (2.0%) strokes, 40 (6.2%) AKIs, and 10 (1.6%) MIs. Secondary outcomes included 56 cases of postoperative delirium (8.7%) and 53 ICU admissions (8.2%).

IPTW Analysis

The IPTW analysis revealed that patients with PIH had significantly higher risks for primary composite outcomes. The relative risk (RR) for a MAP decrease greater than 30% was 2.12, while it rose to 3.64 for a MAP below 60 mmHg.

In IPTW-adjusted analyses, experiencing PIH was linked to increased composite outcomes (RR = 1.66) for a MAP drop of more than 30% and (RR = 2.47) for a MAP below 60 mmHg.

Propensity Score Matching Results

Following PSM, patients with PIH had higher odds of primary composite outcomes (RR = 1.87) when a 30% MAP drop threshold was applied. A MAP below 60 mmHg was also strongly associated with increased risks of stroke (RR = 4.89) and AKI (RR = 3.27).

Discussion

This study demonstrates a clear connection between PIH during TAVR and increased risks of mortality, stroke, AKI, and MI across various thresholds. The risks intensified at lower MAP thresholds and prolonged hypotension.

Promptly addressing hypotension can potentially minimize the risk of delirium, as low blood pressure affects cerebral perfusion. The one-year mortality rate observed aligns with previous studies.

The occurrence of PIH is important in analyzing postoperative outcomes. Employing multiple definitions of hypotension validated the correlation with adverse events.

This study had limitations, including its single-center design which might affect broader applicability, and focusing solely on MAP values during specific periods. Future prospective research is warranted to assess whether managing PIH can improve postoperative outcomes effectively.

Conclusion

This cohort study found varying rates of PIH during TAVR based on defined thresholds, ranging from 32.7% to 63.0%. PIH correlates with heightened risks of all-cause in-hospital mortality, stroke, AKI, and MI. Early detection and management of PIH may help reduce its severity and improve patient outcomes.