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Article

Risk Index for Predicting Supplemental Oxygen Requirement upon Discharge from Postanesthetic Care in Adult Spinal Surgery Patients: A Single-Center Study

by
Edel Rafael Rodea-Montero
1,2,*,†,
Magali Yuyitzi Linarte-Guerra
3,4,†,
Ricardo Garcia-Mora
5,
Paulina Millán-Ramos
3 and
Sergio Manuel Orozco-Ramírez
3,4
1
Department of Research, Hospital Regional de Alta Especialidad del Bajío, Servicios de Salud del Instituto Mexicano del Seguro Social para el Bienestar (IMSS-BIENESTAR), León 37544, Mexico
2
UPIIG, Instituto Politécnico Nacional, Silao de la Victoria 36275, Mexico
3
Department of Anesthesiology, Hospital Regional de Alta Especialidad del Bajío, Servicios de Salud del Instituto Mexicano del Seguro Social para el Bienestar (IMSS-BIENESTAR), León 37544, Mexico
4
Faculty of Medicine, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
5
Department of Surgery, Hospital Regional de Alta Especialidad del Bajío, Servicios de Salud del Instituto Mexicano del Seguro Social para el Bienestar (IMSS-BIENESTAR), León 37544, Mexico
*
Author to whom correspondence should be addressed.
These authors have contributed equally to this work.
Anesth. Res. 2025, 2(2), 10; https://doi.org/10.3390/anesthres2020010
Submission received: 3 February 2025 / Revised: 1 April 2025 / Accepted: 15 April 2025 / Published: 24 April 2025

Abstract

Introduction: In recent years, a greater number of adults have been undergoing spinal surgery. The main complications in the postanesthetic care unit (PACU) include respiratory and cardiovascular problems, pain, and nausea or vomiting. The aim of this study was to describe the preoperative characteristics and intra-anesthetic management of adult patients who underwent elective spinal surgery with balanced general anesthesia and to identify the predictive factors associated with supplemental oxygen requirement upon discharge from the PACU. In addition, we sought to develop a risk index on the basis of multivariable analysis allowing stratification of the probability of supplemental oxygen requirement upon discharge from the PACU. Materials and Methods: In this cross-sectional, retrospective, observational study, the pre- and intra-anesthetic characteristics of adult patients who underwent spinal surgery at any vertebral level under balanced general anesthesia in a tertiary hospital were retrieved. Descriptive statistics are provided, and comparison (Kruskal–Wallis) or correlation analyses (chi-square) were conducted between the characteristics of the patients grouped according to the need for supplemental oxygen upon discharge from the PACU. Receiver operating characteristic (ROC) curves and a multivariate logistic regression model were generated. All tests were performed at the α = 0.05 level. Results: Among 349 patients initially considered, only 211 were included in the analysis. A total of 45.50% of the patients who underwent spinal surgery under balanced general anesthesia required supplemental oxygen upon discharge from the PACU; these patients had significantly greater age, body mass index (BMI), surgery time, and anesthesia time. In addition, the use of norepinephrine and the use of fentanyl were associated with the need for supplemental oxygen. Our proposed risk index for predicting the need for supplemental oxygen upon discharge from the PACU, according to the implementation of a multivariable logistic model based on three simple variables (age ≥ 48 years, BMI ≥ 26.5, and use of fentanyl infusion), achieved an area under the curve (AUC) of 0.740. Conclusions: Age, BMI, and the use of fentanyl can be used to predict the need for supplemental oxygen upon discharge from the PACU. Multicenter and/or longitudinal studies with large sample sizes are needed to confirm the results of this study and improve the prediction of the need for supplemental oxygen upon discharge from the PACU.

1. Introduction

Back pain in adults affects approximately 10–15% of the population in developed countries such as the United States and is therefore considered a global challenge [1]. Although conservative management can improve pain, in many cases, spinal surgery is more effective [2]. In the United States, approximately 900,000 spinal surgeries are performed on adults each year [3]. The number of such surgeries has increased noticeably in recent years, especially for lumbar fusions, where the number of procedures has doubled [4].
Spinal procedures can be classified into three categories according to the expected blood loss (EBL): minor (EBL < 100 mL), major (100 ≤ EBL < 1000 mL), or complex (EBL ≥ 1000 mL) [5]. This classification implies different levels (involved intervertebral spaces) of surgical instrumentation, according to which the surgeries can also be grouped: single-level surgeries, two-level surgeries, or three-or-more-level surgeries [6]. There are several approaches to intraoperative anesthetic preparation, ranging from the use of single-vessel access (medium caliber), to two-vessel access (medium and large caliber), to invasive monitoring with an arterial line and a central venous catheter. Furthermore, the various phases of anesthetic management range from neuromuscular induction and relaxation, to maintenance, analgesia, hemodynamic monitoring, and the use of fibrinolytics and blood management, to prophylaxis against nausea and vomiting.
The list of the phases and medications most commonly used and described in the literature for the intra-anesthetic management of patients undergoing spinal surgery under balanced general anesthesia is detailed in Table 1.
Currently, following both anesthetic and surgical management, patients who undergo spinal surgery under balanced general anesthesia may experience various complications in the postanesthetic care unit (PACU) [18]. The incidence of complications in the PACU has been reported to be approximately 50% [19]. The main complications in the PACU include respiratory or cardiovascular problems, pain, and nausea or vomiting [19]. Respiratory problems affect between 2.8% and 6.9% of patients [18,20], while between 9.8% and 38% of patients experience nausea or vomiting [18,20]. Factors identified to be associated with the presence of these complications in the PACU include age [18], American Society of Anesthesiologists (ASA) classification [20], and the duration of anesthesia [19,20], among others. In addition to these factors, the Enhanced Recovery After Surgery (ERAS) guidelines for spinal surgery detail the importance of optimizing other perioperative factors, such as nutritional status, smoking, alcohol consumption, hemoglobin levels, and intraoperative body temperature, to minimize postoperative complications and enhance recovery [21].
Anesthetic management during the pre- and intraoperative periods is important since the interventions of the anesthesiologist can influence the incidence of complications in the PACU, such as the need for supplementary oxygen. Identifying patients who are more likely to require oxygen supplementation in the PACU and require closer monitoring is important. However, although factors associated with this complication have been identified, there is no consensus on factors that can predict it. The implementation of risk assessment tools, such as the ARISCAT scale for predicting postoperative pulmonary complications [22], Gupta’s risk calculator for estimating postoperative respiratory failure [23], and the STOP-Bang questionnaire for identifying patients at risk of postoperative hypoxemia [24], plays a crucial role in optimizing the clinical management of patients in the PACU.
The aim of this study was to describe the preoperative characteristics and intra-anesthetic management of adult patients who underwent elective spinal surgery with balanced general anesthesia and to identify the predictive factors associated with supplemental oxygen requirement upon discharge from the PACU. In addition, we sought to develop a risk index on the basis of multivariable analysis allowing stratification of the probability of supplemental oxygen requirement upon discharge from the PACU.

2. Materials and Methods

2.1. Patients

A cross-sectional study was conducted involving 349 Mexican ethnicity patients who underwent elective spinal surgery at the Department of Neurosurgery of a tertiary care hospital between 1 January 2022, and 31 December 2023. A sample size of at least 197 patients was calculated using G*Power software (version 3.1.9.7), based on a chi-square test with one degree of freedom, a type I error rate of 0.05, a power (1—type II error) of 0.80, and a small effect size of 0.20. This calculation was based on the results of the study by Abebe et al. [19], which included 396 surgical patients, 56% of whom experienced complications in the PACU of a referral hospital, identifying associations between complications and factors such as patient sex and anesthesia duration of >2 h.
The selection of patients was carried out retrospectively via consecutive sampling on the basis of availability. The inclusion criteria were adult patients who underwent spinal surgery under balanced general anesthesia. The exclusion criteria were previous spinal surgery in the last year, paraplegia or quadriplegia, chronic lung disease (due to their predisposition to needing supplemental oxygen), chronic renal failure (because their typically lower hemoglobin and hematocrit levels increase the likelihood of needing oxygen support), use of anticoagulants (due to their heightened risk of perioperative bleeding, potentially affecting oxygen delivery), and incomplete follow-up PACU data.
Among the initial 349 patients, 283 adult patients (women and men between 18 and 81 years old) who underwent spinal surgery under balanced general anesthesia met the inclusion criteria. After applying the exclusion criteria, only 211 were considered in the final analyses (Figure 1).

2.2. Preanesthetic Characteristics

Data concerning the preanesthetic characteristics of the patients (age, sex, weight, height, BMI [and associated nutritional status], diabetes status, hypertension status, history of alcohol abuse, smoking status, use of nonsteroidal anti-inflammatory drugs (NSAIDs) or gabapentinoids, ASA performance status (PS) score, Assess Respiratory Risk in Surgical Patients in Catalonia Tool (ARISCAT) score, hemoglobin, hematocrit, platelet count, thrombin time, total thromboplastin time, international normalized index, and the allowable blood loss that was calculated based on the patient’s ideal body weight and an acceptable minimum hematocrit value of 30%) were obtained from the clinical records of the patients.

2.3. Intra-Anesthetic Characteristics

Data on the intra-anesthetic characteristics of the patients (type of spinal surgery, level of surgery, surgical position, second line placement, arterial line placement, central venous catheter placement, use of fentanyl and/or propofol for induction, use of rocuronium, cisatracurium, sugammadex, neostigmine, sevoflurane, and/or desflurane, use of infusion fentanyl, lidocaine, and/or dexmedetomidine, use of ephedrine boluses, use of infusion norepinephrine, NSAIDs, paracetamol, regional blockade, use of tranexamic acid as a bolus or via infusion, blood component transfusion, prophylactic dexamethasone, and prophylactic ondansetron) were obtained from the clinical records of the patients. In the operating room, the temperature was maintained at 23 °C, and a thermal mattress was used to ensure the patient remained normothermic throughout the procedure.

2.4. Postanesthetic Characteristics

Data concerning the postanesthetic characteristics of the patients (surgery time, anesthesia time, time in the PACU, time of postsurgical hospital stay, presence of complications in the PACU (oxygen desaturation, moderate to severe pain, nausea or vomiting) and the need for supplemental oxygen upon discharge from the PACU) were obtained from the patients’ clinical records. Pain was assessed using the Numerical Pain Rating Scale (NPRS), which ranges from 0 to 10 points: 0 indicates no pain, 1–3 mild pain, 4–6 moderate pain, and 7–10 severe pain [25]. Patients remained in the PACU for a minimum of 60 min and up to 120 min. The discharge criteria included the absence of anesthetic effects, an NPRS score of 3 or less, and the absence nausea or vomiting. The need for supplemental oxygen at discharge from the PACU was determined if the patient exhibited oxygen desaturation between 85% and 90% after being off supplemental oxygen for three minutes.

2.5. Statistical Analysis

All of the data were analyzed in R programming language (version 3.6.0, R Core Team, Vienna, Austria) [26]. Descriptive statistics of the pre, trans- and postanesthetic characteristics of the patients are presented. In addition, patients were divided on the basis of the need for supplemental oxygen upon discharge from the PACU, and its association with each of the patient characteristics was determined with nonparametric tests (Mann–Whitney U test or chi-square test according to the type of variable). For those variables for which between-group differences were identified, their predictive capacity was evaluated with univariable logistic models, yielding crude odds ratios, and receiver operating characteristic (ROC) curves were constructed to determine the cutoff points that best predicted the need for supplemental oxygen upon discharge from the PACU. Finally, a risk index for the need for supplemental oxygen upon discharge from the PACU was constructed on the basis of a multivariable logistic model. All tests were performed at the α = 0.05 level.

3. Results

A total of 349 patients who underwent spinal surgery during the study period were initially considered. After applying the exclusion criteria, only 211 patients were included in the analysis. Among the 211 patients, 111 (52.61%) were women and 100 (47.39%) were men. The mean (±SD) age of the patients was 52.15 (±14.14) years. The preanesthetic characteristics of the patients are detailed in Table 2.
The surgical procedures were performed for various spinal pathologies, with the most common being degenerative disease in 124 of 211 patients (58.77%), followed by trauma in 67 patients (31.75%). Less frequent conditions included cancer in 7 patients (3.32%), spinal deformities in 2 patients (0.95%), and infections in 2 patients (0.95%). Additionally, 4 patients (1.90%) had both degenerative disease and trauma, while another 4 patients (1.90%) had a combination of spinal deformities and congenital conditions. One patient (0.47%) presented with a complex case involving degenerative disease, spinal deformity, and a spinal lesion.
The distribution of surgeries based on the number of spinal levels involved was as follows: 79 of 211 patients (37.44%) underwent surgery at a single spinal level, 69 patients (32.70%) at two levels, 42 patients (19.91%) at three levels, 20 patients (9.48%) at four levels, and 1 patient (0.47%) at five levels.
Regarding surgical positioning, the most common approach was ventral, used in 181 of 211 cases (85.78%), followed by dorsal in 20 cases (9.48%), a double approach in 7 cases (3.32%), a triple approach in 2 cases (0.95%), and left lateral decubitus in 1 case (0.47%).
Additionally, 121 of 211 patients (57.35%) required the placement of a second intravenous line, 30 patients (14.22%) required an arterial line, and only 2 patients (0.95%) required the placement of a central venous catheter.
The intra- and postanesthetic characteristics of the patients are detailed in Table 3, which shows that 115/211 of patients (54.50%) did not require supplemental oxygen upon discharge from the PACU, whereas 96/211 (45.50%) did.
Table 4 shows the comparison of the preanesthetic characteristics of patients who did and did not require supplemental oxygen upon discharge from the PACU according to the Mann—Whitney U test. Age (56.37 vs. 48.62 years; p < 0.001) and BMI were significantly greater (28.87 vs. 27.36 kg; p = 0.005) for patients who required supplemental upon discharge from the PACU. Additionally, according to the chi-square test, an association was identified between the need for supplemental oxygen upon discharge from the PACU and age group (p = 0.011).
Furthermore, Table 5 details the comparison of the intra- and postanesthetic characteristics of the patients between the groups according to the Mann—Whitney U test, showing that the surgery time in minutes (214.54 vs. 182.00 min; p = 0.003) and the anesthesia time in minutes were significantly longer (271.21 vs. 235.43 min) for patients requiring oxygen supplementation upon discharge from the PACU (p = 0.002). Additionally, according to the chi-square test, the need for supplemental oxygen upon discharge from the PACU was associated with each of the following variables: use of infusion fentanyl in the anesthetic maintenance phase (p < 0.001), use of infusion norepinephrine in the anesthetic maintenance phase (p = 0.038), oxygen desaturation (<90%) in the PACU (p = 0.023), and moderate to severe pain (i.e., numerical rating scale (NPRS) score > 3 pts) in the PACU (p = 0.011).
Figure 2 shows the separate ROC curves for age in years, BMI, surgery time in minutes, and anesthesia time in minutes in predicting the need for supplemental oxygen upon discharge from the PACU, with areas under the curve (AUCs) of 0.653 (95% confidence interval (CI): 0.58, 0.73; p value < 0.001), 0.613 (95% CI: 0.54, 0.69; p value = 0.005), 0.619 (95% CI: 0.54, 0.70; p value = 0.003), and 0.622 (95% CI: 0.55, 0.70; p value = 0.002), respectively.
The best cutoff point for each variable was defined as the point at which efficiency = (Sensitivity + Specificity)/2 in predicting the need for supplemental oxygen upon discharge from the PACU was maximized. The cutoff points for each of the four variables mentioned above were as follows: age ≥ 48 years (sensitivity 82%, specificity 47% and balanced efficiency 65%), BMI ≥ 26.5 kg/m2 (sensitivity 75%, specificity 46% and balanced efficiency 61%), surgery time ≥ 175 min (sensitivity 69%, specificity 53% and balanced efficiency 61%), and anesthesia time ≥ 205 min (sensitivity 77%, specificity 43% and balanced efficiency 60%).
Table 6 shows the crude odds ratios for each of the predictive variables for the need for supplemental oxygen upon discharge from the PACU, according to the results of univariable logistic models, as well as the adjusted odds ratios derived from a multivariable logistic model. The only variables that remained significant in the adjusted odds ratios were age ≥ 48 years (p < 0.001), BMI ≥ 26.5 (p = 0.020), and the use of infusion fentanyl (p = 0.001). These three variables were used to construct the risk index.
Based on the above results, a risk index for predicting the need for supplemental oxygen upon discharge from the PACU for adult patients undergoing spinal surgery was developed, as detailed in Table 7, and the risk classification for the index is shown in Table 8. The classification into low-, moderate-, and high-risk categories was based on the percentage of patients requiring supplemental oxygen upon PACU discharge. Among 211 patients, 96 needed supplemental oxygen, and 10% had low-risk scores (0–5 points), 30% had moderate-risk scores (6–9 points), and 60% had high-risk scores (11 points), illustrating the increasing likelihood of the need for supplemental oxygen with higher risk scores. Finally, Figure 3 shows the graph of the ROC curve of the risk index, which yielded an AUC = 0.740 (95% CI 0.672, 0.807).

4. Discussion

In recent years, the number of adults undergoing spinal surgery has been increasing. There are several approaches to intraoperative anesthesia depending on the underlying pathology, the level of surgical instrumentation, and the type of surgery. The main complications in the PACU include respiratory or cardiovascular problems, pain, and nausea or vomiting [19]. Factors associated with these complications have been identified in various populations; however, in Mexico, such documentary evidence is relatively lacking. This study sought to describe the preoperative characteristics and specific intra-anesthetic management of adult patients who underwent elective spinal surgery under balanced general anesthesia and to evaluate their possible associations with the presence of complications upon discharge from the PACU.
In our study, 45.50% of the patients who underwent spinal surgery under balanced general anesthesia required supplemental oxygen upon discharge from the PACU. Among these patients, age was significantly greater than for those patients who did not require supplemental oxygen upon discharge from the PACU (p < 0.001), which was similar to the findings provided by Abebe et al. [19], who found that 43.32% of patients in the PACU experienced airway and respiratory complications in a study involving 396 surgical patients.
In addition, BMI was significantly greater for patients who required supplemental oxygen upon discharge from the PACU (p = 0.005), similar to the findings described by Mendoça et al. [27] in a prospective study that included 27 obese patients and 27 non-obese patients evaluated in the PACU. The surgery time in minutes was significantly longer for those patients who needed supplemental oxygen upon discharge from the PACU (p = 0.003), similar to the findings reported by Gupta et al. [28] in a prospective study involving 1170 noncardiac surgery patients. Additionally, the anesthesia time in minutes was significantly longer for patients who required supplemental oxygen upon discharge from the PACU (p = 0.002), similar to the results described by Abebe et al. [19] in a study involving 396 patients admitted to the PACU.
Furthermore, we found that age in years, BMI, surgery time in minutes, and anesthesia time in minutes could be used as predictors of the need for supplemental oxygen upon discharge from the PACU, with the following cutoff points: age ≥ 48 years, BMI ≥ 26.5 kg/m2, surgery time ≥ 175 min, and anesthesia time ≥ 205 min. Additionally, we identified an association between the need for supplemental oxygen upon discharge from the PACU and the use of norepinephrine (p = 0.038) and fentanyl (p < 0.001). This latter association can be explained by the fact that opioids are classic respiratory depressants, decreasing both the respiratory volume and rate [29]. Moreover, it is very likely that the need for oxygen administration for patients with higher BMI and older age is related to the distribution of fentanyl and its slower elimination after continuous infusion [30]. With respect to dose, Friedrich et al. [31] reported that high doses of fentanyl were associated with a greater risk of postoperative respiratory complications than low doses.
Finally, we proposed a risk index for predicting the need for supplemental oxygen upon PACU discharge according to the implementation of a multivariable logistic model, where the only variables with significant adjusted odds ratios were age ≥ 48 years (p < 0.001), BMI ≥ 26.5 (p = 0.020), and the use of infusion fentanyl (p = 0.001), achieving an AUC of 0.740. Our simple three-variable index is similar to the ARISCAT scale, which employs seven simple variables to predict postoperative pulmonary complications, with an AUC of 0.900 [22], and to the risk calculator proposed by Gupta et al. [23], which employs five simple variables to predict postoperative respiratory failure, with an AUC of 0.894. Likewise, it aligns with the STOP-Bang questionnaire, an eight-point dichotomized scale evaluated for predicting hypoxemia in patients recovering from noncardiac surgery [24].
This study has certain limitations. First, given its retrospective, cross-sectional nature, it does not allow us to infer causality. Second, the results are based on a single-center cohort with a sample of 211 patients, so the results should be interpreted with caution. Third, although associations between the need for supplemental oxygen upon discharge from the PACU and the use of infusion fentanyl and the use of infusion norepinephrine were separately identified, corresponding dose–response ROC curves could not be constructed, as the total amounts of fentanyl and norepinephrine received by the patients were not recorded. Thus, the absence of detailed dosage information could limit the precision of the findings. Fourth, excluding high-risk patients, such as those with chronic lung disease or paraplegia, may underestimate the true impact of these conditions on oxygen requirement in the PACU. While necessary for controlling confounders, these exclusions limit the generalizability of the results. Fifth, the study lacks an external validation of the proposed risk index to evaluate its applicability in diverse populations and settings.
However, the strengths of this study include the evaluation of various pre- and intra-anesthetic characteristics in a Mexican population that have been identified in other populations as potential predictors of complications in the immediate postoperative period.
Finally, this study and the proposed methodology could serve as the basis for multicenter and/or longitudinal studies with large sample sizes for evaluating the performance of our proposed index. Future studies could include the high-risk groups of patients excluded in our study to better understand their influence on PACU recovery and will focus on validating the risk index using independent cohorts. Researchers may also explore comparisons with other indices to assess its generalizability across different clinical settings. Additionally, incorporating predictive variables such as fentanyl and norepinephrine dosage information could enhance the understanding of dose–response relationships and help to identify the best characteristics for predicting complications in the PACU for patients undergoing spinal surgery.

5. Conclusions

This study expands the knowledge about the complications that occur in the PACU in patients undergoing spinal surgery and identifies associated pre- and intra-anesthetic factors that favor the need for supplemental oxygen upon discharge from the PACU. A total of 45.50% of the patients who underwent spinal surgery under balanced general anesthesia required supplemental oxygen upon discharge from the PACU, among whom age, BMI, surgery time, and anesthesia time were significantly greater. In addition, the use of norepinephrine and the use of fentanyl were associated with the occurrence of this complication. We proposed a risk index to predict the need for supplemental oxygen upon discharge from the PACU based on the implementation of a multivariable logistic model that considers three simple variables (age ≥ 48 years, BMI ≥ 26.5, and the use of infusion fentanyl), achieving an AUC of 0.74. It is necessary to conduct multicenter and/or longitudinal studies with large sample sizes to confirm the results of this study and allow us to evaluate the performance of our index in predicting the need for supplemental oxygen upon PACU discharge.

Author Contributions

Conceptualization: E.R.R.-M., M.Y.L.-G. and S.M.O.-R.; Data curation: E.R.R.-M., M.Y.L.-G., R.G.-M. and P.M.-R.; Formal analysis: E.R.R.-M., M.Y.L.-G., R.G.-M., P.M.-R. and S.M.O.-R.; Methodology: E.R.R.-M., M.Y.L.-G. and S.M.O.-R.; Project administration: E.R.R.-M. and S.M.O.-R.; Software: E.R.R.-M., M.Y.L.-G., R.G.-M. and P.M.-R.; Supervision: E.R.R.-M. and S.M.O.-R.; Validation: E.R.R.-M. and S.M.O.-R.; Writing—original draft: E.R.R.-M., M.Y.L.-G., R.G.-M., P.M.-R. and S.M.O.-R.; Writing—review and editing: E.R.R.-M., M.Y.L.-G., R.G.-M., P.M.-R. and S.M.O.-R. All authors have read and agreed to the published version of the manuscript.

Funding

This research did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Open access funding for this article was supported by Servicios de Salud del Instituto Mexicano del Seguro Social para el Bienestar (IMSS-BIENESTAR).

Institutional Review Board Statement

The study protocol was reviewed and approved by Research and Research-Ethics committees of the HRAEB (protocol codes and dates of approval: CI-HRAEB 009-2024, 13 May 2024 and CEI-015-2024, 22 May 2024). The study was conducted in accordance with the local legislation and institutional requirements.

Informed Consent Statement

The ethics committee/institutional review board waived the requirement of written informed consent for participation from the participants or the participants’ legal guardians/next of kin given the retrospective nature of the study. The confidentiality of the data was meticulously maintained, and all procedures adhered to the pertinent guidelines and regulations governing this research.

Data Availability Statement

All data underlying the findings are available upon request to the corresponding author (edel.rodea@hraeb.gob.mx).

Acknowledgments

The present work was carried out within the framework of the Servicios de Salud del Instituto Mexicano del Seguro Social para el Bienestar (IMSS-BIENESTAR). We thank the Instituto Mexicano del Seguro Social para el Bienestar (IMSS-BIENESTAR) for the support and resources provided.

Conflicts of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Patient selection flow chart.
Figure 1. Patient selection flow chart.
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Figure 2. ROC curves of the predictive variables for the need for supplemental oxygen upon discharge from the PACU. (A) Age (years). (B) BMI (kg/m2). (C) Surgery time (minutes). (D) Anesthesia time (minutes). The blue line represents the model’s performance for each variable across thresholds. The green diagonal line indicates the performance of a random classifier (reference line, AUC = 0.5).
Figure 2. ROC curves of the predictive variables for the need for supplemental oxygen upon discharge from the PACU. (A) Age (years). (B) BMI (kg/m2). (C) Surgery time (minutes). (D) Anesthesia time (minutes). The blue line represents the model’s performance for each variable across thresholds. The green diagonal line indicates the performance of a random classifier (reference line, AUC = 0.5).
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Figure 3. ROC curve of the risk index for predicting the need for supplemental oxygen upon discharge from the PACU for adult patients undergoing spinal surgery (n = 211). The blue line represents the model’s performance across thresholds. The green diagonal line indicates the performance of a random classifier (reference line, AUC = 0.5).
Figure 3. ROC curve of the risk index for predicting the need for supplemental oxygen upon discharge from the PACU for adult patients undergoing spinal surgery (n = 211). The blue line represents the model’s performance across thresholds. The green diagonal line indicates the performance of a random classifier (reference line, AUC = 0.5).
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Table 1. Phases and medications in the intra-anesthetic management of patients undergoing spinal surgery under balanced general anesthesia.
Table 1. Phases and medications in the intra-anesthetic management of patients undergoing spinal surgery under balanced general anesthesia.
PhaseMedication Options
InductionFentanyl [7]Propofol [7]
Neuromuscular relaxationCisatracurium-Neostigmine [8]Rocuronium-Sugammadex [9]
MaintenanceOpioids [10]/Local anesthetics [11]Anesthetic gas [7]
AnalgesiaNSAIDs and Paracetamol [12]Blockage [13]
Monitoring hemodynamicsNoninvasive [7]Invasive [7]
Fibrinolytics and blood managementTranexamic acid [14]Transfusion [14]
Nausea and vomiting prophylaxisDexamethasone [15]Ondansetron [16]
The maintenance phase may also include dexmedetomidine [17]. NSAIDs, non-steroidal anti-inflammatory drugs.
Table 2. Preanesthetic characteristics of the patients.
Table 2. Preanesthetic characteristics of the patients.
VariableAll
n = 211
Age (years)52.15 (14.14)
Age group
18 ≤ Age < 30, n (%)18 (8.53%)
30 ≤ Age < 60, n (%)127 (60.19%)
Age ≥ 60, n (%)66 (31.28%)
Sex
Female, n (%)111 (52.61%)
Male, n (%)100 (47.39%)
Weight (kg)73.43 (11.92)
Height (m)1.62 (0.10)
BMI (kg/m2)28.04 (4.00)
Nutritional status
Underweight
(BMI < 18.5), n (%)
1 (0.47%)
Normal weight
(18.5 ≤ BMI < 25), n (%)
50 (23.70%)
Overweight
(25 ≤ BMI < 30), n (%)
92 (43.60%)
Obesity
(BMI ≥ 30), n (%)
68 (32.23%)
Diabetes, n (%)49 (23.22%)
Hypertension, n (%)71 (33.65%)
Alcohol abuse, n (%)43 (20.38%)
Smoking, n (%)38 (18.01%)
Use of NSAIDs or
gabapentinoids, n (%)
52 (24.64%)
ASA-PS score (IVI)
I, n (%)9 (4.27%)
II, n (%)149 (70.62%)
III, n (%)53 (25.12%)
ARISCAT score n = 209
Low, n (%)65 (31.10%)
Intermediate, n (%)126 (60.29%)
High, n (%)18 (8.61%)
Hemoglobin (g/dL)14.42 (1.81)
Hematocrit (%)42.96 (5.19)
Platelet count (×103)246.28 (75.97)
Thrombin time (s)11.88 (1.41)
TTP (s)28.85 (3.76)
INR1.01 (0.10)
Allowable blood loss (mL)1189.31 (441.07)
Unless otherwise indicated, all values are given as the mean (standard deviation). BMI, body mass index. TTP, total thromboplastin time. INR, international normalized index.
Table 3. Intra- and postanesthetic characteristics of the patients.
Table 3. Intra- and postanesthetic characteristics of the patients.
VariableAll
n = 211
Induction
Fentanyl (µg)269.15 (58.78)
Propofol (mg)118.77 (33.83)
Neuromuscular relaxation
Rocuronium, n (%)193 (91.47%)
Rocuronium (mg)47.1 (10.05)n = 193
Cisatracurium, n (%)18 (8.53%)
Cisatracurium (mg)8.61 (1.69)n = 18
Sugammadex, n (%)8 (3.79%)
Neostigmine, n (%)2 (0.95%)
Maintenance
Sevoflurane, n (%)177 (83.89%)
Desflurane, n (%)34 (16.11%)
Infusion fentanyl, n (%)172 (81.52%)
Infusion lidocaine, n (%)98 (46.45%)
Infusion dexmedetomidine, n (%)17 (8.06%)
Bolus ephedrine, n (%)79 (37.44%)
Infusion norepinephrine, n (%)34 (16.11%)
Analgesia
NSAIDs, n (%)196 (93.33%)n = 210
Paracetamol, n (%)200 (94.79%)
Regional block, n (%)9 (4.27%)
Fibrinolytics and blood management
Tranexamic acid, n (%)4 (100.00%)n = 4
Blood transfusion, n (%)18 (8.53%)
Nausea and vomiting prophylaxis
Dexamethasone, n (%)193 (91.47%)
Ondansetron, n (%)184 (87.20%)
Time
Surgery time (minutes)196.8 (85.31)
Anesthesia time (minutes)251.71 (91.09)
PACU stay (minutes)97.86 (51.09)
Postoperative hospital stay (days)1.16 (0.70)
Complications in the PACU
Oxygen desaturation (<90%), n (%)205 (97.16%)
Moderate to severe pain (>3 pts), n (%)123 (58.29%)
Nausea, n (%)18 (8.53%)
Vomiting, n (%)3 (1.42%)
Supplemental oxygen
at discharge from the PACU
Not required, n (%)115 (54.50%)
Required, n (%)96 (45.50%)
Unless otherwise indicated, all values are given as the mean (standard deviation). PACU, postanesthetic care unit.
Table 4. Preanesthetic characteristics of the patients grouped by the need for supplemental oxygen upon discharge from the PACU.
Table 4. Preanesthetic characteristics of the patients grouped by the need for supplemental oxygen upon discharge from the PACU.
VariableSupplemental Oxygen
at Discharge from the PACU
Not Required
n = 115
Required
n = 96
Comparison
Age (years)48.62 (14.81) 56.37 (12.08) p < 0.001 a,*
Age group p = 0.011 a,*
18 ≤ Age < 30, n (%)15 (13.04%) 3 (3.13%)
30 ≤ Age < 60, n (%)71 (61.74%) 56 (58.33%)
Age ≥ 60, n (%)29 (25.22%) 37 (38.54%)
Sex p = 0.891 b
Female, n (%)61 (53.04%) 50 (52.08%)
Male, n (%)54 (46.96%) 46 (47.92%)
Weight (kg)72.58 (11.84) 74.44 (11.99) p = 0.587 a
Height (m)1.63 (0.10) 1.61 (0.09) p = 0.080 a
BMI (kg/m2)27.36 (4.05) 28.87 (3.81) p = 0.005 a,*
Nutritional status p = 0.081 b
Underweight
(BMI < 18.5), n (%)
1 (0.87%) 0 (0.00%)
Normal weight
(18.5 ≤ BMI < 25), n (%)
34 (29.57%) 16 (16.67%)
Overweight
(25 ≤ BMI < 30), n (%)
49 (42.61%) 43 (44.79%)
Obesity
(BMI ≥ 30), n (%)
31 (26.96%) 37 (38.54%)
Diabetes, n (%)27 (23.48%) 22 (22.92%) p = 0.999 b
Hypertension, n (%)32 (27.83%) 39 (40.63%) p = 0.058 b
Alcoholism, n (%)27 (23.48%) 16 (16.67%) p = 0.235 b
Smoking, n (%)25 (21.74%) 13 (13.54%) p = 0.151 b
Use of NSAIDs or gabapentinoids, n (%)29 (25.22%) 23 (23.96%) p = 0.833 b
ASA-PS score (IVI) p = 0.788 b
I, n (%)5 (4.35%) 4 (4.17%)
II, n (%)79 (68.70%) 70 (72.92%)
III, n (%)31 (26.96%) 22 (22.92%)
ARISCAT score n = 114 n = 95p = 0.072 b
Low, n (%)41 (35.96%) 24 (25.26%)
Intermediate, n (%)67 (58.77%) 59 (62.11%)
High, n (%)6 (5.26%) 12 (12.63%)
Hemoglobin (g/dL)14.42 (1.91) 14.42 (1.71) p = 0.796 a
Hematocrit (%)42.98 (5.55) 42.94 (4.75) p = 0.795 a
Platelet count (×103)244.17 (70.97) 248.82 (81.87) p = 0.943 a
Thrombin time (s)11.81 (1.33) 11.96 (1.51) p = 0.628 a
TTP (s)28.5 (3.85) 29.27 (3.62) p = 0.079 a
INR1.01 (0.10) 1.01 (0.10) p = 0.773 a
Allowable blood loss (mL)1197.72 (488.23) 1179.24 (379.22) p = 0.518 a
Unless otherwise indicated, all values are given as the mean (standard deviation). PACU, postanesthetic care unit. BMI, body mass index. TTP, total thromboplastin time. INR, international normalized index. a Mann—Whitney U test. b Chi-square test. * p value indicates statistical significance.
Table 5. Intra- and postanesthetic characteristics of the patients grouped by the need for supplemental oxygen upon discharge from the PACU.
Table 5. Intra- and postanesthetic characteristics of the patients grouped by the need for supplemental oxygen upon discharge from the PACU.
VariableSupplemental Oxygen
at Discharge from the PACU
Not Required
n = 115
Required
n = 96
Comparison
Induction
Fentanyl (µg)270.04 (58.85) 268.07 (58.97) p = 0.537 a
Propofol (mg)120.78 (35.37) 116.35 (31.89) p = 0.455 a
Neuromuscular relaxation
Rocuronium, n (%)105 (91.30%) 88 (91.67%) p = 0.925 b
Rocuronium (mg)46.95 (10.60)n = 10547.27 (9.40)n = 88p = 0.541 a
Cisatracurium, n (%)10 (8.70%) 8 (8.33%) p = 0.925 b
Cisatracurium (mg)8.2 (1.93)n = 109.13 (1.25)n = 8p = 0.289 a
Sugammadex, n (%)4 (3.48%) 4 (4.17%) p = 0.794 b
Neostigmine, n (%)2 (1.74%) 0 (0.00%) p = 0.194 b
Maintenance
Sevoflurane, n (%)97 (84.35%) 80 (83.33%) p = 0.842 b
Desflurane, n (%)18 (15.70%) 16 (16.70%) p = 0.842 b
Infusion fentanyl, n (%)83 (72.17%) 89 (92.71%) p < 0.001 b,*
Infusion lidocaine, n (%)51 (44.35%) 47 (48.96%) p = 0.504 b
Infusion dexmedetomidine, n (%)10 (8.70%) 7 (7.29%) p = 0.709 b
Bolus ephedrine, n (%)37 (32.17%) 42 (43.75%) p = 0.084 b
Infusion norepinephrine, n (%)13 (11.30%) 21 (21.88%) p = 0.038 b,*
Analgesia
NSAIDs, n (%)106 (92.98%)n = 11490 (93.75%) p = 0.824 b
Paracetamol, n (%)109 (94.78%) 91 (94.79%) p = 0.998 b
Regional block, n (%)6 (5.22%) 3 (3.13%) p = 0.454 b
Fibrinolytics and blood management
Tranexamic acid, n (%)2 (100.00%)n = 22 (100.00%)n = 2p = 0.999 b
Blood transfusion, n (%)9 (7.83%) 9 (9.38%) p = 0.688 b
Nausea and vomiting prophylaxis
Dexamethasone, n (%)108 (93.91%) 85 (88.54%) p = 0.164 b
Ondansetron, n (%)105 (91.30%) 79 (82.29%) p = 0.051 b
Time
Surgery time (minutes)182 (85.31) 214.52 (82.28) p = 0.003 a,*
Anesthesia time (minutes)235.43 (90.75) 271.21 (88.05) p = 0.002 a,*
PACU stay (minutes)95.65 (48.48) 100.5 (54.18) p = 0.689 a
Postoperative hospital stay (days)1.15 (0.72) 1.17 (0.68) p = 0.698 a
Complications in the PACU
Oxygen desaturation (<90%), n (%)109 (94.78%) 96 (100.00%) p = 0.023 b,*
Moderate to severe pain (>3 pts), n (%)58 (50.43%) 65 (67.71%) p = 0.011 b,*
Nausea, n (%)7 (6.09%) 11 (11.46%) p = 0.164 b
Vomiting, n (%)1 (0.87%) 2 (2.08%) p = 0.458 b
Unless otherwise indicated, all values are given as the mean (standard deviation). PACU, postanesthetic care unit. a Mann–Whitney U test. b Chi-square test. * p value indicates statistical significance.
Table 6. Results of logistic regression models for predicting the need for supplemental oxygen upon PACU discharge (n = 211).
Table 6. Results of logistic regression models for predicting the need for supplemental oxygen upon PACU discharge (n = 211).
UnivariableMultivariable
VariableCrude ORIC 95%p ValueAdjusted
OR
IC 95%p Value
Age ≥ 48 years4.112.17–7.79p < 0.001 *3.841.91–7.70p < 0.001 *
BMI ≥ 26.5 kg/m22.151.19–3.88p = 0.011 *2.171.13–4.16p = 0.020 *
Use of infusion fentanyl4.902.05–11.70p < 0.001 *4.921.86–13.01p = 0.001 *
Use of infusion norepinephrine2.201.04–4.66p = 0.041 *1.670.74–3.79p = 0.218
Surgery time ≥ 175 min2.491.41–4.38p = 0.002 *1.610.66–3.91p = 0.294
Anesthesia time ≥ 205 min2.591.42–4.72p = 0.002 *0.810.30–2.18p = 0.683
PACU, postanesthetic care unit. BMI, body mass index. OR: odds ratio. IC, confidence interval. * p value indicates statistical significance.
Table 7. Risk index for the need for supplemental oxygen upon discharge from the PACU (n = 211).
Table 7. Risk index for the need for supplemental oxygen upon discharge from the PACU (n = 211).
CharacteristicPoints
Age < 48 years0
Age ≥ 48 years4
BMI < 26.5 kg/m20
BMI ≥ 26.5 kg/m22
Infusion fentanyl not used0
Infusion fentanyl used5
PACU, postanesthetic care unit. BMI, body mass index.
Table 8. Risk of the need for supplemental oxygen upon discharge from the PACU according to the risk index score.
Table 8. Risk of the need for supplemental oxygen upon discharge from the PACU according to the risk index score.
RiskScoreNumber of Patients
(n = 211)
% of PatientsNumber of Patients Requiring
Supplemental Oxygen
(n = 96)
% of Patients Requiring
Supplemental Oxygen
Low0 to 5 points4822.75%1010.42%
Moderate6 to 9 points8339.34%2930.21%
High11 points8037.91%5759.38%
PACU, postanesthetic care unit.
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Rodea-Montero, E.R.; Linarte-Guerra, M.Y.; Garcia-Mora, R.; Millán-Ramos, P.; Orozco-Ramírez, S.M. Risk Index for Predicting Supplemental Oxygen Requirement upon Discharge from Postanesthetic Care in Adult Spinal Surgery Patients: A Single-Center Study. Anesth. Res. 2025, 2, 10. https://doi.org/10.3390/anesthres2020010

AMA Style

Rodea-Montero ER, Linarte-Guerra MY, Garcia-Mora R, Millán-Ramos P, Orozco-Ramírez SM. Risk Index for Predicting Supplemental Oxygen Requirement upon Discharge from Postanesthetic Care in Adult Spinal Surgery Patients: A Single-Center Study. Anesthesia Research. 2025; 2(2):10. https://doi.org/10.3390/anesthres2020010

Chicago/Turabian Style

Rodea-Montero, Edel Rafael, Magali Yuyitzi Linarte-Guerra, Ricardo Garcia-Mora, Paulina Millán-Ramos, and Sergio Manuel Orozco-Ramírez. 2025. "Risk Index for Predicting Supplemental Oxygen Requirement upon Discharge from Postanesthetic Care in Adult Spinal Surgery Patients: A Single-Center Study" Anesthesia Research 2, no. 2: 10. https://doi.org/10.3390/anesthres2020010

APA Style

Rodea-Montero, E. R., Linarte-Guerra, M. Y., Garcia-Mora, R., Millán-Ramos, P., & Orozco-Ramírez, S. M. (2025). Risk Index for Predicting Supplemental Oxygen Requirement upon Discharge from Postanesthetic Care in Adult Spinal Surgery Patients: A Single-Center Study. Anesthesia Research, 2(2), 10. https://doi.org/10.3390/anesthres2020010

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