Intraoperative hypotension (IOH) is common in non-cardiac surgery and may directly induce ischemic injury to vital organs such as the heart, brain, and kidneys, potentially leading to multiorgan dysfunction [1–3]. Neonates are a vulnerable population with immature neurological and cardiovascular systems under general anesthesia, and the incidence of IOH can exceed 50% [4]. Anesthetic agents may suppress myocardial contractility, induce peripheral vasodilation, and reduce sympathetic tone, thereby lowering cardiac output and systemic vascular resistance, ultimately resulting in IOH [5,6]. Beyond compromising intraoperative organ perfusion, IOH substantially elevates the risks of postoperative acute kidney injury, brain injury, and necrotizing enterocolitis, and may adversely affect long-term neurodevelopmental outcomes [7]. Hence, evaluating the occurrence of intraoperative hypotension in neonates, identifying its risk factors, and verifying its impact on prognosis carry important clinical value and practical significance.

Existing studies on neonatal intraoperative hypotension are predominantly limited to small sample sizes [8,9]. Most investigations only focus on the incidence or individual risk factors, without a comprehensive evaluation of preoperative baseline profiles, intraoperative events, and postoperative clinical outcomes [10]. Moreover, there is currently no universally accepted definition of IOH in neonates. The absence of standardized diagnostic criteria for IOH hinders the comparability and generalizability of research results [7,11]. Thus, a large-sample study that can explore the prevalence, preoperative risk factors, and outcome implications of IOH in neonates undergoing general anesthesia is clinically meaningful for optimizing perioperative hemodynamic management and mitigating adverse postoperative outcomes.

Study subjects were stratified into an IOH group and a non-IOH group based on the occurrence of intraoperative hypotension. Continuous variables with normal distribution were reported as mean ± standard deviation, and compared by Student t-tests. Non-normally distributed continuous variables were described as median (interquartile range), with intergroup differences assessed via the Mann-Whitney U test. Categorical variables were presented as counts (percentages), and compared by the chi-square test or Fisher’s exact test. Variables with a P-value < 0.10 in univariate analysis were included in the multivariate logistic regression model (Forward, Likelihood Ratio). Results were expressed as odds ratios with corresponding 95% confidence intervals. A two-sided P < 0.05 was considered statistically significant. All statistical analyses were performed using IBM SPSS 26.0 software.

This large-sample retrospective cohort study including 1712 cases found a high incidence of intraoperative hypotension in neonates undergoing non-cardiac surgery with general anesthesia. IOH was significantly associated with prolonged postoperative recovery and an increased risk of complications. Higher ASA classification, emergency surgery, preoperative congenital heart disease, preoperative acidosis, surgery duration >60 min, and thoracic surgery were independent risk factors, while greater gestational age and neurosurgery were protective factors. Therefore, close monitoring and timely intervention of IOH are warranted in clinical practice, particularly for neonates with the aforementioned risk factors.

The definition of IOH in neonates remains controversial, mainly because blood pressure varies with gestational age, postnatal age, and birth weight [12]. In neonatal practice, hypotension is commonly defined using absolute or age-related thresholds, such as MAP below gestational age in weeks, MAP < 35 mmHg, or values below postnatal age-specific percentiles [4,11,13]. However, these criteria are primarily applied to circulatory assessment during the first 72 h or the first week after birth. Relative reductions from baseline blood pressure have also been used as diagnostic criteria [7,10]. Because the studied cohort included neonates from birth to 28 days of age, a relative reduction from each patient’s own preoperative baseline was considered more appropriate than a fixed absolute threshold. Therefore, the authors defined IOH as a ≥ 20% decrease in MAP from preoperative baseline. Future studies are needed to establish a standardized definition of neonatal IOH.

The incidence of intraoperative hypotension in neonates undergoing general anesthesia exceeded 50%, consistent with previous reports [5,9,14]. This can be attributed to the physiological immaturity of the neonatal cardiovascular system, limited autonomic regulation, and high sensitivity to anesthetic agents. Neonates have minimal myocardial contractile reserve and immature sympathetic control; anesthetics may further suppress myocardial function, vasodilate peripheral vessels, and reduce vascular tone, collectively decreasing cardiac output and systemic vascular resistance [15]. These factors form the pathophysiological basis for the high prevalence of IOH in this population. The present findings clinically confirm that neonates are at extremely high risk for IOH and warrant prioritized perioperative hemodynamic monitoring and management.

Univariate analysis showed that the IOH group had significantly smaller gestational age, lower postnatal age, lower body weight, more preterm birth, and higher ASA classification. These findings suggest that poorer preoperative baseline status is associated with higher risk of IOH, which aligns with previous findings [16,17]. Gestational age is considered a protective factor against IOH, which is consistent with the physiological characteristics of newborns, as preterm infants exhibit immature systemic circulatory regulation and baroreflex development [18]. A higher ASA classification suggests more severe underlying diseases, more comorbidities, and insufficient organ reserve capacity, making these neonates more susceptible to hemodynamic decompensation following anesthesia and surgical operation [16]. Compared with healthy newborns, those with CHD often have intracardiac shunts, ventricular hypertrophy, pulmonary hypertension, or cardiac dysfunction, resulting in significantly lower myocardial compliance and cardiac output regulation capacity that predispose them to greater intraoperative hypotension [19]. This study also identified preoperative acidosis as a risk factor for IOH, indicating that internal environment homeostasis and tissue perfusion status are closely associated with IOH. Therefore, for critically ill newborns with preoperative CHD, especially preterm infants, cardiac function should be optimized and acidosis corrected preoperatively, and more rigorous intraoperative monitoring of blood pressure and cardiac output should be implemented to prevent and promptly correct IOH.

In this study, emergency surgery, operation duration more than 60 min, and thoracic surgery were independent risk factors for IOH, whereas neurosurgery was a protective factor. Pediatric patients undergoing emergency surgery often present with preoperative fasting, volume depletion, and heightened stress, increasing hemodynamic lability [20]. Prolonged surgery increases anesthetic exposure, surgical stress, fluid fluctuations, and hypothermia risk, collectively predisposing to IOH [16]. Thoracic surgery may influence intrathoracic pressure and cardiopulmonary interactions, compromising circulatory stability [21]. Neurosurgery was protective, likely because most procedures in the studied center were minimally invasive and did not affect intrathoracic pressure, intra-abdominal pressure, or venous return, thereby minimizing interference with cardiac preload and afterload.

From a prognostic perspective, the IOH group experienced significantly longer postoperative mechanical ventilation duration, length of ICU stay and postoperative hospital stay. IOH was also associated with acute kidney injury, intraventricular hemorrhage, and respiratory complications, indicating its adverse impact on postoperative recovery [11,22]. The neonatal brain, kidneys, and intestines are extremely sensitive to ischemia. Intraoperative hypotension can lead to decreased perfusion pressure and microcirculatory dysfunction, which may precipitate acute organ injury and potentially affect long-term neurodevelopmental outcomes [23,24]. However, previous studies have reported inconsistent findings regarding the relationship between IOH and postoperative AKI or adverse neurodevelopment [25,26]. This discrepancy may be attributed to differences in study populations, IOH definitions, perioperative management, follow-up periods, and confounding adjustment strategies. Further multicenter prospective studies are needed to clarify this relationship.

This study has several limitations. First, as a single-center retrospective study, it is subject to potential selection and information biases. Second, measurement discrepancies between noninvasive and invasive blood pressure monitoring may have introduced additional error [27]. Third, long-term outcomes such as neurodevelopmental follow-up were not collected. Future multicenter prospective cohort studies are needed to establish individualized IOH warning thresholds for neonates and to develop risk prediction models integrating preoperative risk factors and intraoperative monitoring parameters, thereby enabling precise early warning and individualized management.

This study confirms that intraoperative hypotension is a common intraoperative event and was associated with a series of postoperative complications and severely affects neonatal recovery, highlighting the importance of maintaining intraoperative hemodynamic stability. In neonates undergoing general anesthesia, independent risk factors for IOH include high American Society of Anesthesiologists physical status, emergency surgery, preoperative congenital heart disease, preoperative acidosis, longer surgery duration, and thoracic surgery. Higher gestational age and neurosurgery were identified as protective factors. Optimizing preoperative management and intraoperative monitoring, along with shortening operative time, may reduce the risk of IOH and potentially improve neonatal outcomes.

This work was supported by the National Natural Science Foundation of China (grant numbers 82372159).

Jialian Zhao: Conceptualization, Data curation, Formal analysis, Methodology, Writing – original draft. Chunyi Jin: Data curation. Guihang An: Data curation. Mei Guo: Data curation. Wenyuan Zhang: Data curation, Formal analysis. Yang Li: Data curation. Dengming Lai: Formal analysis. Jinfa Tou: Conceptualization, Writing – review & editing. Yue Jin: Conceptualization, Methodology, Writing – review & editing.