Intrapulmonary Shunt and Oxygenation During One-Lung Ventilation: Influence of Dexmedetomidine Combined with Transcutaneous Acupoint Electrical Stimulation

Yinjuan Wei; Sitao Min; Hongxing Min

doi:10.20944/preprints202505.2440.v1

Submitted:

29 May 2025

Posted:

30 May 2025

You are already at the latest version

Abstract

Background: One-lung ventilation (OLV) often causes hypoxemia due to intrapulmonary shunting. This study investigated how combining dexmedetomidine with transcutaneous acupoint electrical stimulation (TAES) affects intrapulmonary shunt and oxygenation during OLV. Methods: Eighty thoracoscopic lobectomy patients were randomized into four groups: control (Group A, saline), dexmedetomidine (Group B, 1μg·kg−1 loading, 0.4μg·kg−1·h−1 maintenance), TAES (Group C, bilateral stimulation at five acupoints), and combination (Group D, both interventions). Measurements were taken at five timepoints: before anesthesia (T0), 15 min after two-lung ventilation (T1), 30 min after OLV (T2), one h after OLV (T3), and 15 min after resuming two-lung ventilation (T4). Oxygenation parameters (PaO2, OI, A-aDO2, Qs/Qt, RI) and hemodynamics were assessed. Results: During OLV (T2, T3), Groups B and C showed significantly improved oxygenation parameters compared to Group A (p<0.05), while Group D demonstrated superior improvement compared to all other groups (p<0.05). All groups experienced decreased OI and increased Qs/Qt and A-aDO2 during OLV compared to baseline, with Group A showing the most pronounced changes and Group D the least. Conclusion: Both dexmedetomidine and TAES individually improve intrapulmonary shunt and oxygenation during OLV, but their combination provides superior results compared to either intervention alone.

Keywords:

one-lung ventilation

;

transcutaneous acupoint electrical stimulation

;

dexmedetomidine

;

intrapulmonary shunt

;

oxygenation

Subject:

Medicine and Pharmacology - Anesthesiology and Pain Medicine

Introduction

One-lung ventilation (OLV) is a specialized ventilation technique used during thoracic surgeries where one lung is collapsed to provide optimal surgical exposure while ventilation is maintained in the contralateral lung. This approach prevents secretions and blood from entering the ventilated lung, and allows for different ventilation strategies according to surgical requirements while maintaining appropriate airway pressure [1,2]. Despite its clinical advantages, OLV represents a non-physiological ventilation state that can lead to significant pathophysiological changes such as ventilation/perfusion mismatch [3]. This ventilation/perfusion imbalance can lead to increased intrapulmonary shunting and a higher risk of hypoxemia, and futhermore, potentially increase patient mortality [4,5].

Hypoxic pulmonary vasoconstriction (HPV) serves as a critical protective mechanism regulating intrapulmonary shunting to avoid ventilation/perfusion mismatch during OLV [6,7]. This physiological response occurs when alveolar hypoxia triggers localized vasoconstriction in pulmonary vessels, effectively redirecting blood flow from poorly ventilated areas to well-ventilated regions of the lung. By improving ventilation/perfusion matching and decreasing shunting in the non-ventilated lung, HPV optimizes arterial oxygenation. However, despite effective HPV, some degree of intrapulmonary shunting inevitably persists, compromising systemic oxygenation. Consequently, clinical interventions that either prevent HPV suppression or enhance its effectiveness during OLV have significant therapeutic potential.

Dexmedetomidine (DEX), a highly selective

α_{2}

-adrenergic receptor agonist, has gained widespread clinical use as an anesthetic adjuvant due to its sedative, analgesic, and anxiolytic properties through central sympatholytic effects [8]. Recent basic and clinical research has demonstrated DEX’s protective effects on multiple organ systems, including the nervous system, heart, lungs, and kidneys. In pulmonary applications specifically, numerous studies have confirmed DEX’s lung-protective effects through anti-inflammatory mechanisms and stress response modulation so that to enhance HPV and improve intrapulmonary shunting and oxygenation during OLV [9]. For example, foundational studies have shown that DEX can effectively inhibit histamine-induced bronchospasm and mitigate OLV-associated lung injury through upregulation of aquaporin-1 expression and reduction of intrapulmonary shunting [10]. Furthermore, studies have reported that DEX can decrease intrapulmonary shunting and oxidative stress and improve arterial oxygenation and HPV during OLV while also reducing the requirement for inhaled anesthetics [9].

Acupuncture is one of China’s traditional medical therapies, recognized for its simplicity, effectiveness, and wide clinical application. Transcutaneous acupoint electrical stimulation (TAES) is a non-invasive electro-acupuncture method that combines the advantages of transcutaneous electrical nerve stimulation with acupoint therapy. Both basic and clinical research have demonstrated TAES’s protective effects on lung function, particularly in reducing perioperative intrapulmonary shunting and improving oxygenation [11,12,13,14,15].

Although, effects of DEX and TAES on intrapulmonary shunting and oxygenation during OLV have been widely studied before. Most studies have focused on the effects of these interventions used independently on intrapulmonary shunting during OLV, with few investigations examining the impact of combined DEX and TAES. And also, no clinical studies have yet examined the effects of the combination of different acupoints on intrapulmonary shunting during OLV. Therefore, this study aims to investigate whether transcutaneous electrical stimulation of combinations of the four different acupoints (Kongzui (LU6), Feishu (BL13), Hegu (LI4), and Zusanli (ST36)) improves intrapulmonary shunting and oxygenation during OLV and whether the combination of DEX and TAES provides greater improvement than either intervention alone, offering reference guidance for clinical practice.

Materials and Methods

Study Design, Setting, and Participants

This study was conducted at the Department of Thoracic Surgery of Ningxia Medical University General Hospital. The study protocol was approved by the hospital’s Ethics Committee (KYLL 2021-387), and written informed consent was obtained from all participants. The following inclusion criteria were implemented: (1) American Society of Anesthesiologists (ASA) physical status class II or III; (2) age between 18 and 65 years; (3) body mass index (BMI) between 18 and 24.9 kg/m²; (4) expected surgery duration between 1 and 3 hours; (5) patients with no obvious abnormalities in cardiac, cerebral, hepatic, and renal function; and (6) patients with no obvious abnormalities in pulmonary function.

Patients were excluded if they had previous surgery at acupoint meridian pathways or local skin infections at acupoints, contraindications for dexmedetomidine, previous thoracotomy history, or preoperative anemia (hemoglobin

< 120

g/L for males,

< 110

g/L for females).

Patients were withdrawn from the study if they experienced any of the following during one-lung ventilation (OLV): SpO₂

< 92 %

for more than 30 seconds requiring conversion to two-lung ventilation; mean arterial pressure

< 55

mmHg; peak airway pressure

> 35

cmH₂O; development of respiratory or metabolic acidosis; severe cardiac arrhythmias; or intraoperative blood loss exceeding 400 mL.

Randomization and Grouping

Eighty eligible patients scheduled for thoracoscopic lobectomy were randomized using a random number table into four groups with a 1:1:1:1 allocation ratio: control group (Group A), dexmedetomidine group (Group B), transcutaneous acupoint electrical stimulation group (Group C), and combined dexmedetomidine with transcutaneous acupoint electrical stimulation group (Group D).

Figure 1. Flow Chart.

Anesthetic Protocol and Intervention

Anesthetic Preparation: Patients underwent comprehensive preoperative evaluations before surgery. In the operating room, standard monitoring was established with a multifunction monitor (GE Healthcare, USA) for electrocardiogram (ECG), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and peripheral oxygen saturation (SpO₂).Anesthetic depth was monitored via bispectral index (BIS) (Vista 3.0, Aspect Medical Systems). After establishing peripheral venous access, patients with normal Allen’s test results received left radial artery catheterization under local anesthesia for continuous blood pressure monitoring and arterial blood sampling.

Group Interventions: The four groups received specific interventions as follows:

(1) Group A (Control): Patients received intravenous normal saline 10 minutes before anesthesia induction with no transcutaneous acupoint electrical stimulation (TAES).

(2) Group B (Dexmedetomidine): Patients received intravenous dexmedetomidine at a loading dose of 1

μ

g·

{kg}^{- 1}

10 minutes before anesthesia induction, followed by continuous infusion at 0.4

μ

g·

{kg}^{- 1} \cdot

h^{- 1}

until 30 minutes before the end of surgery, with no TAES.

(3) Group C (TAES): Patients received intravenous normal saline 10 minutes before anesthesia induction, with concurrent bilateral TAES at Kongzui (LU6), Feishu (BL13), Hegu (LI4), and Zusanli (ST36) acupoints. TAES was continued throughout surgery until wound closure.

(4) Group D (Dexmedetomidine & TAES): Patients received both dexmedetomidine administration as in Group B and TAES as in Group C.

Anesthesia Induction: Total intravenous anesthesia was administered using midazolam (0.05-0.1 mg·

{kg}^{- 1}

), sufentanil (0.3-0.5

μ

g·

{kg}^{- 1}

), etomidate (0.2-0.3 mg·

{kg}^{- 1}

), and rocuronium (0.6-0.9 mg·

{kg}^{- 1}

). After pre-oxygenation and confirmed neuromuscular blockade, a double-lumen endobronchial tube (37# males, 35# females) was inserted under direct laryngoscopy. Proper positioning was verified by fiberoptic bronchoscopy.

During two-lung ventilation, parameters were set as: FiO₂ = 100%, tidal volume (

V_{T}

) 6-8 mL·

{kg}^{- 1}

, respiratory rate 12-18 breaths/min, and I:E ratio 1:2. For OLV, parameters were adjusted to:

V_{T}

4-6 mL·

{kg}^{- 1}

, FiO₂ = 100%, and I:E ratio 1:2. Respiratory rate was adjusted to maintain

P_{E T}

CO₂ between 35-45 mmHg, with peak airway pressure limited to 30 cmH₂O.

Anesthesia Maintenance: Anesthesia was maintained using propofol (4-12 mg·

{kg}^{- 1} \cdot

h^{- 1}

) and remifentanil (0.2-0.5

μ

g·

{kg}^{- 1} \cdot

\min^{- 1}

). These infusion rates were titrated to maintain BIS values of 40-60 and keep blood pressure within ±20% of baseline. Rocuronium boluses were administered as needed for muscle relaxation, with vasoactive drugs used to maintain hemodynamic stability. Normal saline (Groups A, C) or dexmedetomidine (Groups B, D) was discontinued 30 minutes before surgery ended. TAES (Groups C and D) were stopped after wound closure. All anesthetic infusions were terminated at procedure completion.

Anesthesia Recovery: Residual neuromuscular blockade was antagonized with neostigmine, and flumazenil was administered to reverse the effects of midazolam. Upon meeting extubation criteria, thorough suctioning of the trachea and oral cavity was performed before removing the endobronchial tube. After confirmation of stable vital signs, patients were transferred to the post-anesthesia care unit (PACU) for continued monitoring. Postoperative analgesia was managed via patient-controlled intravenous analgesia (PCIA) for all groups, with the analgesic pump containing sufentanil (2

μ

g·

{kg}^{- 1}

) diluted to 100 mL with normal saline.

Transcutaneous Acupoint Electrical Stimulation Method

Acupoint Localization: Acupoints were located strictly according to the National Standard of the People’s Republic of China GB12346-90 "Location of Acupoints." The following bilateral acupoints were selected:

(1) Kongzui (LU6): Located on the palmar side of the forearm on the radial side, 7 cm proximal to the transverse wrist crease on the line connecting Chize (LU5) and Taiyuan (LU9).

(2) Feishu (BL13): Located approximately

1.5

inches lateral to the lower border of the spinous process of the third thoracic vertebra.

(3) Hegu (LI4): Located between the first and second metacarpal bones, at the midpoint of the radial side of the second metacarpal bone.

(4) Zusanli (ST36): Located 3 inches below the lower border of the patella, one finger-breadth lateral to the anterior crest of the tibia.

TAES Parameters and Application: We used the following parameters for transcutaneous electrical stimulation: pulse width 100

μ s

, waveform dense-disperse wave, frequency

2 - 100 H z

, and electrical current intensity generally between

6 - 12 m A

, adjusted to patient tolerance with sensations of soreness, numbness, distension, heaviness, or mild pain. After cleansing the skin at each acupoint with alcohol,

30 m m \times 30 m m

electrode pads were placed bilaterally at the LU6, BL13, LI4, and ST36 acupoints and secured with sterile adhesive film. TAES was initiated 10 minutes before anesthesia induction using an electronic acupuncture device and continued throughout surgery until wound closure.

Outcomes

The primary outcome consists of hemodynamic, blood gas analysis, and Oxygenation parameters measured for each patient throughout the intraoperative period. All values were recorded at five time points: before anesthesia (

T_{0}

), 15 min after two-lung ventilation (

T_{1}

), 30 min after OLV (

T_{2}

), one h after OLV (

T_{3}

), and 15 min after resuming two-lung ventilation (

T_{4}

). Hemodynamic parameters include systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), and bispectral index (BIS). Blood gas analysis parameters include PaCO₂, PaO₂, hemoglobin (Hb), and hematocrit (HCT). Oxygenation parameters include alveolar-arterial oxygen difference (A-aDO₂), oxygenation index (OI), respiratory index (RI), and intrapulmonary shunt fraction (Q_s/Q_t).

We also measured the baseline characteristics (patient demographic and clinical characteristics), including patient demographic and clinical characteristics, such as gender, age, weight, height, BMI, ASA classification, preoperative pulmonary function indicators (FEV1, FVC, FEV1/FVC), OLV duration, surgical duration, surgical site, and number of resected lobes.

Statistical Analysis

Statistical analysis was performed in this study using R statistical software. Normally distributed quantitative data were expressed as mean ± standard deviation (

\bar{x} \pm s

). Intergroup differences were analyzed using one-way analysis of variance (ANOVA), with post-hoc LSD-t tests for pairwise comparisons. Repeated measures data were analyzed using repeated measures ANOVA. Categorical data were expressed as frequency (percentage) and compared using chi-square tests. The significance level was set at

α = 0.05

.

Results

A total of 88 patients were initially assessed for eligibility. Flow chart are shown in Figure 2. Specifically, three patients were excluded preoperatively: one with previous surgery at acupoint locations, one with preoperative anemia, and one with preoperative bradycardia and atrioventricular block. As a consequence, 85 patients entered the study (Group A: 22 patients, Group B: 21 patients, Group C: 21 patients, Group D: 21 patients). Five patients were subsequently withdrawn: two patients in Group A with intraoperative blood loss

> 400 m L

, one patient in Group B with surgery duration

< 1

hour, one patient in Group C who developed severe acidosis, and one patient in Group D with surgery duration

> 3

hours. Ultimately, 20 patients in each group completed the study and were included in the final analysis.

The patient demographic and clinical characteristics across groups are comparable, as shown in Table 1. No statistically significant differences were observed among the four groups over gender, age, weight, height, BMI, ASA classification, preoperative pulmonary function indicators, left/right OLV ratio, number of resected lobes, surgical duration, OLV duration, or anesthesia duration (

p > 0.05

).

Comparisons of Hemodynamic Parameters

A comparison of the hemodynamic outcomes between the four groups is presented in Table 2. Our analysis encompassed both the temporal changes within each group and the between-group differences at corresponding time points. Compared with

T_{0}

, all four groups showed significant decreases in HR, SBP, DBP, MAP, and BIS values at time points

T_{1}

-

T_{4}

(

p < 0.05

). However, no statistically significant differences were observed among the four groups in HR, SBP, DBP, MAP, or BIS values at any timepoint (

p > 0.05

).

Comparisons of Blood Gas Analysis Parameters

The comparison of the blood gas analysis parameters between the four groups is presented in Table 3. No statistically significant differences were observed within or between groups regarding pH, PaCO₂, Hb, or HCT at any timepoint (p > 0.05).

Comparisons of Oxygenation Parameters

A comparison of the oxygenation parameters between the four groups is presented in Table . Similarly, we analyzed the temporal changes within each group and the differences between groups at corresponding time points.

For comparison between temporal points, relative to

T_{0}

, all groups showed significant increases in PaO₂, Q_s/Q_t, RI, and A-aDO₂ at timepoints

T_{1}

-

T_{4}

. PaO₂ and RI increases were greater at

T_{1}

and

T_{4}

than at

T_{2}

and

T_{3}

, with Group A showing the smallest increase and Group D the largest (

p < 0.05

). Conversely, Q_s/Q_t and A-aDO₂ increases were greater at

T_{2}

and

T_{3}

than at

T_{1}

and

T_{4}

, with Group A showing the largest increase and Group D the smallest (

p < 0.05

). OI increased at

T_{1}

and

T_{4}

but decreased at

T_{2}

and

T_{3}

in all groups, with Group A showing the largest decrease and Group D the smallest (

p < 0.05

).

For intergroup comparisons, at timepoint

T_{2}

, Groups B and C showed significantly higher PaO₂ and OI, along with lower A-aDO₂, Q_s/Q_t, and RI compared to Group A (

p < 0.05

). Group D demonstrated further improvements in these parameters compared to Groups B and C (

p < 0.05

). Similarly, at timepoint

T_{3}

, Groups B and C exhibited significantly higher PaO₂ and OI, with lower A-aDO₂, Q_s/Q_t, and RI compared to Group A (

p < 0.05

). Again, Group D showed superior improvements in these parameters compared to Groups B and C (

p < 0.05

).

Discussion

In this study, we evaluated the effects of dexmedetomidine (DEX), transcutaneous acupoint electrical stimulation (TAES), and their combination on intrapulmonary shunting and oxygenation during one-lung ventilation (OLV) in patients undergoing thoracoscopic surgery. Our primary finding is that the combination of DEX and TAES provided superior improvement in intrapulmonary shunting and oxygenation during OLV compared to either intervention alone, suggesting a synergistic effect that could significantly benefit patients undergoing thoracic procedures requiring OLV.

To exclude confounding factors, first, we carefully controlled for patient demographics, preoperative pulmonary function, surgical characteristics, and anesthesia management across all groups. Statistical analysis confirmed no significant differences between groups for any of these parameters as shown in Table 1. Second, as previous research suggests, intrapulmonary shunting peaks approximately

30 - 40

minutes after initiating one-lung ventilation (coinciding with lowest PaO₂), as hypoxic pulmonary vasoconstriction gradually redirects blood flow from the non-ventilated to the ventilated lung before reaching relative stability [16,17]; therefore, we verified double-lumen tube positioning bronchoscopically before and after positional changes, measured lung function parameters at five specific time points (

T_{0}

through

T_{4}

), and employed total intravenous anesthesia to eliminate anesthetic technique as a confounding factor for intrapulmonary shunting. Additionally, we continuously monitored end-tidal carbon dioxide and adjusted respiratory parameters to maintain normal carbon dioxide levels, avoiding hypercapnia or hyperventilation that could influence HPV and intrapulmonary shunting [18]. We also strictly limited intraoperative blood loss across all groups to prevent excessive hemorrhage from causing inadequate perfusion and multi-organ ischemia-hypoxia [74]. Our results showed no significant differences in pH, PaCO₂, Hb, or HCT within or between groups at any time point as shown in Table 3. This comprehensive control of potential confounding variables ensures the comparability of the four groups, thereby minimizing potential confounding effects on our primary outcomes.

We want to discuss several points from our primary results. Firstly, regarding effects on oxygenation parameters, our results showed that DEX administration in Group B decreased intrapulmonary shunt (

Q_{s} / Q_{t}

), respiratory index (RI), and alveolar-arterial oxygen difference (

{A - aDO}_{2}

) while increasing arterial oxygen partial pressure (

{PaO}_{2}

) and oxygenation index (OI) compared to Group A. These findings align with previous studies demonstrating DEX’s pulmonary protective effects during one-lung ventilation (OLV) [8,19,20,21]. The physiological mechanisms underlying DEX’s improvements may occur through: (1) enhancement of hypoxic pulmonary vasoconstriction through reduced oxidative stress and increased nitric oxide release; (2) inhibition of inflammatory responses and promotion of pulmonary fluid balance via aquaporin-1 expression; and (3) activation of

α_{2}

-receptors on vascular smooth muscle, improving ventilation/perfusion ratios [22,23]. These mechanisms collectively contribute to reduced intrapulmonary shunting and improved oxygenation during OLV. Additionally, while our findings confirm that DEX can moderately reduce intrapulmonary shunting and improve oxygenation during OLV, several factors—including surgical manipulation, OLV itself, enhanced inflammatory responses, and HPV suppression—may limit the extent of this improvement, necessitating exploration of additional therapeutic strategies.

Table 4. Comparison of Oxygenation Parameters Between Groups.

Parameter	Time	Group A n = 20	Group B n = 20	Group C n = 20	Group D n = 20
PaO₂	$T_{0}$	$73.50 \pm 5.85$	$74.06 \pm 7.77$	$75.27 \pm 5.78$	$74.81 \pm 6.16$
	$T_{1}$	$448.06 \pm 28.10$	$449.83 \pm 26.54$	$447.66 \pm 24.17$	$444.12 \pm 20.05$
	$T_{2}$	$128.46 \pm 14.67$	$171.94 \pm 23 . 63^{*}$	$166.67 \pm 23 . 54^{*}$	$206.17 \pm 32 . 10^{* † ‡}$
	$T_{3}$	$138.38 \pm 19.35$	$180.82 \pm 32 . 85^{*}$	$170.16 \pm 37 . 61^{*}$	$217.62 \pm 32 . 88^{* † ‡}$
	$T_{4}$	$452.39 \pm 26.84$	$440.14 \pm 29.23$	$453.82 \pm 26.76$	$451.59 \pm 22.29$
OI	$T_{0}$	$350.00 \pm 27.85$	$352.64 \pm 37.00$	$358.43 \pm 27.52$	$356.24 \pm 29.33$
	$T_{1}$	$448.06 \pm 28.10$	$449.83 \pm 26.54$	$447.66 \pm 24.17$	$444.12 \pm 20.05$
	$T_{2}$	$128.46 \pm 14.67$	$171.94 \pm 23 . 63^{*}$	$166.67 \pm 23 . 54^{*}$	$206.17 \pm 32 . 10^{* † ‡}$
	$T_{3}$	$138.38 \pm 19.35$	$180.82 \pm 32 . 85^{*}$	$170.16 \pm 37 . 61^{*}$	$217.62 \pm 32 . 88^{* † ‡}$
	$T_{4}$	$452.39 \pm 26.84$	$440.14 \pm 29 . 23^{*}$	$454.82 \pm 27 . 61^{*}$	$451.60 \pm 22 . 29^{* † ‡}$
RI	$T_{0}$	$0.39 \pm 0.12$	$0.38 \pm 0.13$	$0.36 \pm 0.11$	$0.36 \pm 0.12$
	$T_{1}$	$0.49 \pm 0.09$	$0.48 \pm 0 . 09^{*}$	$0.49 \pm 0 . 08^{*}$	$0.50 \pm 0 . 07^{* † ‡}$
	$T_{2}$	$4.24 \pm 0.62$	$2.95 \pm 0 . 64^{*}$	$3.07 \pm 0 . 63^{*}$	$2.30 \pm 0 . 54^{* † ‡}$
	$T_{3}$	$3.89 \pm 0.69$	$2.80 \pm 0 . 72^{*}$	$3.11 \pm 1 . 01^{*}$	$2.12 \pm 0 . 51^{* † ‡}$
	$T_{4}$	$0.47 \pm 0.09$	$0.52 \pm 0 . 10^{*}$	$0.47 \pm 0 . 09^{*}$	$0.47 \pm 0 . 07^{* † ‡}$
Q_s/Q_t	$T_{0}$	$1.70 \pm 0.40$	$1.65 \pm 0.45$	$1.61 \pm 0.38$	$1.62 \pm 0.40$
	$T_{1}$	$11.82 \pm 1.36$	$11.74 \pm 1 . 32^{*}$	$11.87 \pm 1 . 14^{*}$	$12.00 \pm 0 . 96^{* † ‡}$
	$T_{2}$	$24.93 \pm 0.55$	$23.40 \pm 0 . 89^{*}$	$23.58 \pm 0 . 88^{*}$	$22.12 \pm 1 . 20^{* † ‡}$
	$T_{3}$	$24.60 \pm 0.68$	$23.06 \pm 1 . 17^{*}$	$23.44 \pm 1 . 37^{*}$	$21.67 \pm 1 . 25^{* † ‡}$
	$T_{4}$	$11.61 \pm 1.33$	$12.19 \pm 1 . 42^{*}$	$11.49 \pm 1 . 33^{*}$	$11.65 \pm 1 . 06^{* † ‡}$
A-aDO₂	$T_{0}$	$27.95 \pm 6.75$	$27.13 \pm 7.53$	$26.37 \pm 6.34$	$26.58 \pm 6.72$
	$T_{1}$	$216.70 \pm 28.09$	$214.88 \pm 27 . 34^{*}$	$217.43 \pm 23 . 73^{*}$	$220.23 \pm 20 . 02^{* † ‡}$
	$T_{2}$	$535.82 \pm 15.74$	$492.96 \pm 24 . 65^{*}$	$497.82 \pm 24 . 30^{*}$	$458.47 \pm 31 . 99^{* † ‡}$
	$T_{3}$	$526.36 \pm 19.16$	$483.78 \pm 31 . 90^{*}$	$494.49 \pm 37 . 76^{*}$	$446.78 \pm 33 . 00^{* † ‡}$
	$T_{4}$	$212.19 \pm 27.58$	$224.29 \pm 29 . 81^{*}$	$209.73 \pm 27 . 43^{*}$	$212.87 \pm 21 . 97^{* † ‡}$

*

p < 0.05

compared with Group A; ^†

p < 0.05

compared with Group B; ^‡

p < 0.05

compared with Group C.

All time points (

T_{1}

-

T_{4}

) showed statistically significant differences compared to baseline (

T_{0}

) in all groups (

p < 0.05

).

Secondly, for group C, our results demonstrate that at timepoints

T_{2}

and

T_{3}

, Group C exhibited higher PaO₂ and OI with lower A-aDO₂, Q_s/Q_t, and RI compared to Group A (p < 0.05). This aligns with previous studies showing that TAES improves ventilation/perfusion balance, reduces intrapulmonary shunting, enhances oxygenation, and may decrease inflammatory markers during OLV [24]. Many studies support the individual benefits of the acupoints selected in our study: Feishu (Bladder Meridian) for regulating pulmonary function and ventilating the lungs [25,26], however, there is generally limited clinical evidence on the effects of combining all four of these acupoints. Our findings confirm that the acupoint combination of Feishu, Kongzui, Zusanli, and Hegu can improve ventilation/perfusion balance and oxygenation capacity during OLV, likely due to the complementary relationships between these meridians and their connections to pulmonary function. Regarding the physiological mechanisms underlying TAES (Group C), while the precise pathways remain unclear, two potential mechanisms have been identified: First, TAES may regulate the balance between endothelium-derived vasoconstrictors and vasodilators, which helps improve intrapulmonary shunting [19,27]. Second, TAES appears to enhance pulmonary function through activation of A

α

and A

β

nerve fibers, providing protection against hypoxia-induced lung injury [24].

Thirdly, our study demonstrated that Group D (combined DEX abd TAES) demonstrated significantly better improvements in all measured parameters compared to both single-intervention groups, indicating a synergistic effect of the combined therapy. Additionally, although, Groups B (DEX) and C (TAES) showed improvements compared to the control group, there were no significant differences between these two intervention groups. The physiological mechanisms underlying the superior efficacy of Group D (combined DEX abd TAES) may result from TAES enhancing DEX’s effects by stimulating acupoints to increase endothelium-derived vasoconstrictor secretion, constricting collapsed-side pulmonary vessels, reducing blood flow to collapsed lung tissue, and further improving ventilation/perfusion imbalances [11,28].

Finally, regarding hemodynamic parameters, all four groups showed decreased HR, SBP, DBP, and MAP at timepoints T1-T4 compared to T0, but no significant differences were observed between groups at any timepoint. This lack of difference may be attributed to several factors: First, although DEX typically produces biphasic effects (initial hypertension with reflex bradycardia followed by stabilization below baseline [28]), we administered ephedrine and atropine to counteract DEX’s sympatholytic effects that could cause intraoperative hypotension and bradycardia. Second, while TAES has been shown to bidirectionally regulate heart rate and reduce stress responses during lobectomy and endotracheal intubation, our use of vasoactive drugs likely masked these effects. Third, the combined therapy group showed no statistical differences compared to either the DEX or TAES groups, likely also due to vasoactive drug administration.

Our study has several important limitations to consider. First, our design included multiple groups with relatively small sample sizes, which, combined with numerous potential confounding factors, may have affected the reliability of our results. Second, we did not analyze patterns of vasoactive drug usage during anesthesia, which could have provided insights into whether TAES and DEX differently influenced hemodynamic parameters. Third, although our TAES protocol using Feishu, Kongzui, Hegu, and Zusanli acupoints showed benefits for intrapulmonary shunting during OLV, we still need additional research to identify the most effective acupoint combinations. Fourth, we did not measure changes in inflammatory mediators, which limited our understanding of how inflammation affects HPV in this context. Finally, the synergistic effects of combined DEX and TAES on intrapulmonary shunting and oxygenation during OLV under general anesthesia require further comprehensive investigation.

Conclusions

In conclusion, our study demonstrates that both dexmedetomidine and transcutaneous acupoint electrical stimulation individually improve intrapulmonary shunting and oxygenation during one-lung ventilation in thoracoscopic surgery, as evidenced by reduced Q_s/Q_t, increased OI, and decreased RI and A-aDO₂. Importantly, the combination therapy exhibits synergistic effects, providing superior improvement in these parameters compared to either intervention alone. This combined approach may represent an effective strategy for optimizing pulmonary function during OLV, potentially through enhanced HPV, reduced inflammation, and improved ventilation/perfusion matching.

Author Contributions

Conceptualization, Y.W., and H.M.; methodology, Y.W. S.M,; statistical analysis and data curation, S.M; resources, H.M.; writing—original draft preparation, Y.W., S.M.; writing—review and editing, S.M.; validation, Y.W., S.M., and H.M.; supervision, H.M.; project administration, H.M.; funding acquisition, H.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of General Hospital of Ningxia Medical University (protocol code KYLL 2021-387).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Acknowledgments

The authors would like to thank the Department of Thoracic Surgery and the Department of Anesthesiology at General Hospital of Ningxia Medical University for their support in conducting this study.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:

OLV	One-lung ventilation
TLV	Two-lung ventilation
TAES	Transcutaneous acupoint electrical stimulation
DEX	Dexmedetomidine
HPV	Hypoxic pulmonary vasoconstriction
PaO₂	Arterial oxygen partial pressure
OI	Oxygenation index
RI	Respiratory index
Q_s/Q_t	Intrapulmonary shunt fraction
A-aDO₂	Alveolar-arterial oxygen difference
ASA	American Society of Anesthesiologists
BMI	Body mass index
BIS	Bispectral index
SBP	Systolic blood pressure
DBP	Diastolic blood pressure
MAP	Mean arterial pressure
HR	Heart rate
PCIA	Patient-controlled intravenous analgesia
FEV1	Forced expiratory volume in one second
FVC	Forced vital capacity

References

Slobod, D.; Damia, A.; Leali, M.; Spinelli, E.; Mauri, T. Pathophysiology and clinical meaning of ventilation-perfusion mismatch in the acute respiratory distress syndrome. Biology 2022, 12, 67. [Google Scholar] [CrossRef] [PubMed]
Bernasconi, F.; Piccioni, F. One-lung ventilation for thoracic surgery: current perspectives. Tumori Journal 2017, 103, 495–503. [Google Scholar] [CrossRef] [PubMed]
Fischer, G.W.; Cohen, E. An update on anesthesia for thoracoscopic surgery. Current Opinion in Anesthesiology 2010, 23, 7–11. [Google Scholar] [CrossRef] [PubMed]
Huang, S.Q.; Zhang, J.; Zhang, X.X.; Liu, L.; Yu, Y.; Kang, X.H.; Wu, X.M.; Zhu, S.M. Can dexmedetomidine improve arterial oxygenation and intrapulmonary shunt during one-lung ventilation in adults undergoing thoracic surgery? A meta-analysis of randomized, placebo-controlled trials. Chinese Medical Journal 2017, 130, 1707–1714. [Google Scholar] [CrossRef]
FLEISHER, L. ANESTHESIOLOGY CLINICS. Anesthesiology Clinics 2015, 33. [Google Scholar]
Campos, J.H.; Feider, A. Hypoxia during one-lung ventilation—a review and update. Journal of cardiothoracic and vascular anesthesia 2018, 32, 2330–2338. [Google Scholar] [CrossRef]
Meggiolaro, K.; Wulf, H.; Feldmann, C.; Wiesmann, T.; Schubert, A.K.; Risse, J. Airway management for lung separation in thoracic surgery: An update. Der Anaesthesist 2018, 67, 555–567. [Google Scholar] [CrossRef]
Bao, N.; Tang, B. Organ-protective effects and the underlying mechanism of dexmedetomidine. Mediators of inflammation 2020, 2020, 6136105. [Google Scholar] [CrossRef] [PubMed]
Xia, R.; Yin, H.; Xia, Z.y.; Mao, Q.j.; Chen, G.d.; Xu, W. Effect of intravenous infusion of dexmedetomidine combined with inhalation of isoflurane on arterial oxygenation and intrapulmonary shunt during single-lung ventilation. Cell biochemistry and biophysics 2013, 67, 1547–1550. [Google Scholar] [CrossRef]
Groeben, H.; Mitzner, W.; Brown, R.H. Effects of the alpha2-adrenoceptor agonist dexmedetomidine on bronchoconstriction in dogs. Anesthesiology 2004, 100, 359–363. [Google Scholar] [CrossRef]
Pan, P.; Zhang, X.; Qian, H.; Shi, W.; Wang, J.; Bo, Y.; Li, W. Effects of electro-acupuncture on endothelium-derived endothelin-1 and endothelial nitric oxide synthase of rats with hypoxia-induced pulmonary hypertension. Experimental Biology and Medicine 2010, 235, 642–648. [Google Scholar] [CrossRef] [PubMed]
Luo, J.; Yan, R.; Ding, L.; Ning, J.; Chen, M.; Guo, Y.; Liu, J.; Chen, Z.; Zhou, R. Electroacupuncture Attenuates Ventilator-Induced Lung Injury by Modulating the Nrf2/HO-1 Pathway. Journal of Surgical Research 2024, 295, 811–819. [Google Scholar] [CrossRef] [PubMed]
Yang, J.; Huang, L.; Zhu, J.; Liu, S.; Ji, F.; Tian, W.; Zheng, Z.; Zheng, M. Effects of perioperative electroacupuncture on postoperative gastrointestinal recovery after thoracoscopic lung surgery. EXPLORE 2024, 20, 450–455. [Google Scholar] [CrossRef] [PubMed]
Tu, Q.; Yang, Z.; Gan, J.; Zhang, J.; Que, B.; Song, Q.; Wang, Y. Transcutaneous electrical acupoint stimulation improves immunological function during the perioperative period in patients with non-small cell lung cancer undergoing video-assisted thoracic surgical lobectomy. Technology in cancer research & treatment 2018, 17, 1533033818806477. [Google Scholar]
Song, X.M.; Wu, X.J.; Li, J.G.; Le, L.L.; Liang, H.; Xu, Y.; Zhang, Z.Z.; Wang, Y.L. The effect of electroacupuncture at ST36 on severe thermal injury-induced remote acute lung injury in rats. Burns 2015, 41, 1449–1458. [Google Scholar] [CrossRef]
Jin, Y.; Zhao, X.; Li, H.; Wang, Z.; Wang, D. Effects of sevoflurane and propofol on the inflammatory response and pulmonary function of perioperative patients with one-lung ventilation. Experimental and therapeutic medicine 2013, 6, 781–785. [Google Scholar] [CrossRef]
Zheng, X.; Lv, Z.; Yin, K.; Peng, M. Effects of epidural anesthesia combined with inhalation anesthesia or intravenous anesthesia on intrapulmonary shunt and oxygenation in patients undergoing long term single lung ventilation. Pakistan Journal of Medical Sciences 2018, 34, 799. [Google Scholar] [CrossRef] [PubMed]
Yamamoto, Y.; Nakano, H.; Ide, H.; Ogasa, T.; Takahashi, T.; Osanai, S.; Kikuchi, K.; Iwamoto, J. Role of airway nitric oxide on the regulation of pulmonary circulation by carbon dioxide. Journal of Applied Physiology 2001, 91, 1121–1130. [Google Scholar] [CrossRef]
Lee, S.H.; Kim, N.; Lee, C.Y.; Ban, M.G.; Oh, Y.J. Effects of dexmedetomidine on oxygenation and lung mechanics in patients with moderate chronic obstructive pulmonary disease undergoing lung cancer surgery: a randomised double-blinded trial. European Journal of Anaesthesiology| EJA 2016, 33, 275–282. [Google Scholar] [CrossRef]
Wang, S.L.; Duan, L.; Xia, B.; Liu, Z.; Wang, Y.; Wang, G.M. Dexmedetomidine preconditioning plays a neuroprotective role and suppresses TLR4/NF-κB pathways model of cerebral ischemia reperfusion. Biomedicine & Pharmacotherapy 2017, 93, 1337–1342. [Google Scholar]
Wang, Y.; Gong, C.; Yu, F.; Zhang, Q. Effect of dexmedetomidine on intrapulmonary shunt in patients with sevoflurane maintained during one-lung ventilation: A case–control study. Medicine 2022, 101, e31818. [Google Scholar] [CrossRef] [PubMed]
Erturk, E.; Topaloglu, S.; Dohman, D.; Kutanis, D.; Beşir, A.; Demirci, Y.; Kayir, S.; Mentese, A. The comparison of the effects of sevoflurane inhalation anesthesia and intravenous propofol anesthesia on oxidative stress in one lung ventilation. BioMed research international 2014, 2014, 360936. [Google Scholar] [CrossRef]
Meng, J.; Lv, Q.; Yao, J.; Wang, S.; Yang, K. [Retracted] Effect of Dexmedetomidine on Postoperative Lung Injury during One-Lung Ventilation in Thoracoscopic Surgery. BioMed Research International 2020, 2020, 4976205. [Google Scholar] [CrossRef] [PubMed]
Zhao, F.; Wang, Z.; Ye, C.; Liu, J. Effect of Transcutaneous Electrical Acupoint Stimulation on One-Lung Ventilation-Induced Lung Injury in Patients Undergoing Esophageal Cancer Operation. Evidence-Based Complementary and Alternative Medicine 2020, 2020, 9018701. [Google Scholar] [CrossRef] [PubMed]
Mei-Zhen, L.; Qiao-Mei, W.; Yu, L.; Zhang, Z.D.; Gang-Yi, P.; Chang-Xiu, W.; Xiao-Pan, W.; Ying-Rui, M.; Xiong, P.; Hui-Chao, C.; et al. Traditional Chinese medicine nursing protocols for COVID-19. Journal of Integrative Nursing 2020, 2, 40–49. [Google Scholar]
Zhang, S.; Zhu, Q.; Zhan, C.; Cheng, W.; Mingfang, X.; Fang, M.; Fang, L. Acupressure therapy and Liu Zi Jue Qigong for pulmonary function and quality of life in patients with severe novel coronavirus pneumonia (COVID-19): a study protocol for a randomized controlled trial. Trials 2020, 21, 1–11. [Google Scholar] [CrossRef]
Ngai, S.P.; Jones, A.Y.; Hui-Chan, C.W. Acu-tens and postexercise expiratory flow volume in healthy subjects. Evidence-Based Complementary and Alternative Medicine 2011, 2011. [Google Scholar] [CrossRef]
Talke, P.; Richardson, C.A.; Scheinin, M.; Fisher, D.M. Postoperative Pharmacokinetics and Sympatholytic Effects of Dexmedetomidine:. Anesthesia & Analgesia 1997, 85, 1136–1142. [Google Scholar] [CrossRef]

Table 1. Baseline Characteristics.

Variable	Group A n = 20	Group B n = 20	Group C n = 20	Group D n = 20
Gender (Male/Female)	11/9	14/7	7/13	11/9
Age (years)	$53.90 \pm 7.62$	$57.10 \pm 7.82$	$56.45 \pm 6.40$	$55.85 \pm 7.90$
Height (cm)	$166.15 \pm 7.66$	$168.00 \pm 6.67$	$165.25 \pm 4.98$	$167.45 \pm 7.03$
Weight (kg)	$63.85 \pm 8.85$	$62.98 \pm 8.72$	$61.65 \pm 6.75$	$64.00 \pm 5.40$
BMI (kg/m²)	$23.05 \pm 1.90$	$22.26 \pm 2.34$	$22.55 \pm 2.05$	$22.83 \pm 1.50$
ASA Classification (II/III)	12/8	10/10	9/11	11/9
FEV₁ (L)	$2.44 \pm 0.45$	$2.69 \pm 0.53$	$2.52 \pm 0.42$	$2.60 \pm 0.41$
FVC (L)	$3.07 \pm 0.53$	$3.22 \pm 0.55$	$3.13 \pm 0.52$	$3.23 \pm 0.52$
FEV₁/FVC (%)	$82.28 \pm 1.11$	$82.85 \pm 2.60$	$83.02 \pm 1.67$	$82.64 \pm 2.25$
Left/Right OLV Ratio	11/9	12/8	12/8	10/10
Resected Lobes (1/2/3)	20/0/0	20/0/0	20/0/0	20/0/0
Surgery Duration (min)	$141.65 \pm 38.89$	$131.50 \pm 41.64$	$138.20 \pm 41.60$	$127.65 \pm 47.80$
OLV Duration (min)	$118.70 \pm 34.52$	$105.05 \pm 38.75$	$115.40 \pm 37.60$	$117.30 \pm 46.06$
Anesthesia Duration (min)	$170.50 \pm 46.51$	$165.70 \pm 43.00$	$166.40 \pm 45.89$	$166.81 \pm 44.44$

Table 2. Comparison of Hemodynamic Parameters.

Parameter	Time	Group A n = 20	Group B n = 20	Group C n = 20	Group D n = 20
HR	$T_{0}$	$77.70 \pm 10.27$	$80.00 \pm 15.52$	$75.35 \pm 10.01$	$77.05 \pm 10.86$
	$T_{1}$	$71.40 \pm 11 . 07^{*}$	$67.00 \pm 10 . 29^{*}$	$67.00 \pm 8 . 86^{*}$	$69.95 \pm 9 . 67^{*}$
	$T_{2}$	$70.60 \pm 9 . 95^{*}$	$71.45 \pm 14 . 38^{*}$	$67.85 \pm 6 . 83^{*}$	$67.60 \pm 7 . 96^{*}$
	$T_{3}$	$68.55 \pm 9 . 31^{*}$	$68.90 \pm 11 . 86^{*}$	$68.55 \pm 8 . 95^{*}$	$67.45 \pm 8 . 43^{*}$
	$T_{4}$	$67.85 \pm 9 . 30^{*}$	$65.75 \pm 7 . 61^{*}$	$69.70 \pm 5 . 82^{*}$	$68.50 \pm 6 . 91^{*}$
SBP	$T_{0}$	$135.10 \pm 15.31$	$135.90 \pm 15.91$	$127.70 \pm 15.17$	$133.80 \pm 17.11$
	$T_{1}$	$117.45 \pm 15 . 74^{*}$	$115.50 \pm 14 . 36^{*}$	$118.25 \pm 17 . 08^{*}$	$118.25 \pm 12 . 39^{*}$
	$T_{2}$	$111.25 \pm 15 . 99^{*}$	$115.45 \pm 15 . 31^{*}$	$107.00 \pm 13 . 83^{*}$	$108.65 \pm 10 . 21^{*}$
	$T_{3}$	$109.65 \pm 14 . 58^{*}$	$109.10 \pm 11 . 39^{*}$	$105.35 \pm 12 . 39^{*}$	$107.00 \pm 9 . 93^{*}$
	$T_{4}$	$114.60 \pm 10 . 54^{*}$	$116.90 \pm 11 . 41^{*}$	$112.10 \pm 9 . 40^{*}$	$111.35 \pm 12 . 06^{*}$
DBP	$T_{0}$	$79.40 \pm 7.07$	$80.10 \pm 9.21$	$77.10 \pm 10.49$	$79.20 \pm 11.56$
	$T_{1}$	$69.45 \pm 6 . 99^{*}$	$72.00 \pm 8 . 72^{*}$	$70.30 \pm 6 . 86^{*}$	$69.60 \pm 5 . 85^{*}$
	$T_{2}$	$70.35 \pm 11 . 12^{*}$	$72.35 \pm 9 . 53^{*}$	$70.00 \pm 5 . 29^{*}$	$70.95 \pm 8 . 67^{*}$
	$T_{3}$	$70.10 \pm 8 . 84^{*}$	$69.05 \pm 7 . 24^{*}$	$69.45 \pm 6 . 84^{*}$	$69.40 \pm 6 . 70^{*}$
	$T_{4}$	$72.85 \pm 6 . 66^{*}$	$74.40 \pm 9 . 14^{*}$	$69.85 \pm 4 . 45^{*}$	$72.55 \pm 7 . 79^{*}$
MAP	$T_{0}$	$97.97 \pm 7.27$	$98.70 \pm 10.75$	$93.97 \pm 9.55$	$97.40 \pm 12.15$
	$T_{1}$	$85.45 \pm 6 . 79^{*}$	$86.50 \pm 8 . 97^{*}$	$86.28 \pm 7 . 99^{*}$	$85.82 \pm 6 . 42^{*}$
	$T_{2}$	$83.98 \pm 11 . 64^{*}$	$86.71 \pm 9 . 46^{*}$	$82.33 \pm 6 . 97^{*}$	$83.52 \pm 8 . 51^{*}$
	$T_{3}$	$83.28 \pm 9 . 47^{*}$	$82.40 \pm 6 . 26^{*}$	$81.42 \pm 7 . 40^{*}$	$81.93 \pm 6 . 22^{*}$
	$T_{4}$	$86.77 \pm 6 . 94^{*}$	$88.57 \pm 8 . 48^{*}$	$83.93 \pm 5 . 11^{*}$	$85.48 \pm 8 . 38^{*}$
BIS	$T_{0}$	$97.45 \pm 0.95$	$97.00 \pm 0.86$	$97.30 \pm 1.42$	$97.45 \pm 0.95$
	$T_{1}$	$50.25 \pm 4 . 41^{*}$	$49.70 \pm 4 . 14^{*}$	$50.35 \pm 5 . 19^{*}$	$51.05 \pm 5 . 74^{*}$
	$T_{2}$	$50.75 \pm 4 . 47^{*}$	$50.00 \pm 4 . 52^{*}$	$51.20 \pm 5 . 14^{*}$	$52.80 \pm 5 . 84^{*}$
	$T_{3}$	$51.15 \pm 4 . 26^{*}$	$50.65 \pm 3 . 88^{*}$	$52.40 \pm 4 . 50^{*}$	$52.95 \pm 4 . 69^{*}$
	$T_{4}$	$52.00 \pm 4 . 27^{*}$	$51.00 \pm 3 . 76^{*}$	$52.60 \pm 3 . 66^{*}$	$52.65 \pm 3 . 77^{*}$

*

p < 0.05

compared with

T_{0}

within the same group.

No statistically significant differences were observed between groups at any time point (

p > 0.05

).

Table 3. Comparison of Blood Gas Analysis Parameters Between Groups.

Parameter	Time	Group A n = 20	Group B n = 20	Group C n = 20	Group D n = 20
pH	$T_{0}$	$7.39 \pm 0.02$	$7.39 \pm 0.02$	$7.39 \pm 0.02$	$7.39 \pm 0.02$
	$T_{1}$	$7.39 \pm 0.02$	$7.38 \pm 0.03$	$7.39 \pm 0.02$	$7.39 \pm 0.03$
	$T_{2}$	$7.39 \pm 0.02$	$7.39 \pm 0.04$	$7.39 \pm 0.02$	$7.39 \pm 0.02$
	$T_{3}$	$7.38 \pm 0.02$	$7.38 \pm 0.03$	$7.38 \pm 0.02$	$7.38 \pm 0.03$
	$T_{4}$	$7.38 \pm 0.02$	$7.38 \pm 0.02$	$7.38 \pm 0.02$	$7.38 \pm 0.02$
PaCO₂	$T_{0}$	$38.63 \pm 1.97$	$38.84 \pm 2.35$	$38.48 \pm 1.96$	$38.67 \pm 2.17$
	$T_{1}$	$38.59 \pm 2.03$	$38.64 \pm 2.66$	$38.34 \pm 2.45$	$38.92 \pm 2.57$
	$T_{2}$	$38.98 \pm 2.86$	$38.48 \pm 2.16$	$38.81 \pm 2.47$	$38.69 \pm 2.26$
	$T_{3}$	$38.61 \pm 2.17$	$38.72 \pm 2.39$	$38.68 \pm 2.28$	$38.88 \pm 2.31$
	$T_{4}$	$38.74 \pm 2.58$	$38.86 \pm 2.29$	$38.76 \pm 2.39$	$38.83 \pm 2.72$
Hb	$T_{0}$	$14.39 \pm 2.02$	$14.54 \pm 2.00$	$14.47 \pm 1.69$	$14.52 \pm 2.58$
	$T_{1}$	$14.50 \pm 2.14$	$14.53 \pm 1.79$	$14.05 \pm 1.38$	$14.44 \pm 2.13$
	$T_{2}$	$14.38 \pm 2.08$	$14.73 \pm 2.03$	$14.08 \pm 1.36$	$14.13 \pm 1.96$
	$T_{3}$	$14.60 \pm 2.02$	$14.66 \pm 2.05$	$14.11 \pm 1.29$	$14.10 \pm 1.87$
	$T_{4}$	$14.69 \pm 2.11$	$14.86 \pm 1.98$	$14.78 \pm 1.42$	$14.56 \pm 1.75$
HCT	$T_{0}$	$41.77 \pm 9.58$	$41.95 \pm 5.98$	$41.53 \pm 7.99$	$41.95 \pm 5.86$
	$T_{1}$	$41.50 \pm 9.12$	$41.55 \pm 5.88$	$41.65 \pm 6.97$	$41.70 \pm 7.11$
	$T_{2}$	$41.05 \pm 10.27$	$41.65 \pm 6.80$	$41.40 \pm 4.41$	$41.35 \pm 6.23$
	$T_{3}$	$41.30 \pm 7.04$	$41.05 \pm 6.07$	$41.35 \pm 6.34$	$41.20 \pm 4.64$
	$T_{4}$	$41.10 \pm 7.77$	$41.25 \pm 6.10$	$41.60 \pm 6.31$	$41.90 \pm 4.75$

No statistically significant differences were observed within or between groups at any time point (

p > 0.05

).

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Copyright: This open access article is published under a Creative Commons CC BY 4.0 license, which permit the free download, distribution, and reuse, provided that the author and preprint are cited in any reuse.