DOI: https://doi.org/10.21203/rs.3.rs-1568943/v1
Shoulder arthroscopic surgery has become the first choice for the surgical treatment of a variety of shoulder diseases. In previous studies, the incidence of hypoxemia after shoulder arthroscopic surgery was 12.6% and 16%, which is usually accompanied by several unfavourable consequences, including prolonged ventilator support, increased hospital length of stay, increased intensive care unit length of stay, and higher perioperative mortality. The Purpose of this study is to identify independent risk factors of postoperative hypoxemia in the post anesthesia care unit(PACU)after shoulder arthroscopic surgery.
This was a single-center retrospective study including 358 patients undergoing shoulder arthroscopic surgery between January 2020 and January 2021 at LuoYang Orthopedic Hospital of Henan Province Orthopedic Hospital of Henan Province. The relative factors of postoperative hypoxemia were tested through descriptive analysis and logistic regression, and the independent risk factors were obtained.
The incidence of postoperative hypoxemia was 14.0% in our study. Through descriptive analysis and logistic regression, the independent risk factors of postoperative hypoxemia were as follows: age[odd ratio(OR)=1.069, 95% confidence interval (CI) = 1.012–1.129,P = 0.018]、body mass index (BMI) (OR = 1.425,95% CI = 1.250–1.626,P = 0.000、operating time (OR = 1.011,95%CI = 1.000-1.021,P = 0.041) irrigation fluid volume (OR = 1.093,95%CI 1.033–1.156,P = 0.002) .
Age, BMI, operating time, irrigation fluid volume were 4 independent risk factors for postoperative hypoxemia in the PACU after shoulder arthroscopic surgery.
Shoulder arthroscopic surgery has become the first choice for the surgical treatment of a variety of shoulder diseases due to the advantages of minimally invasive, decreasing morbidity rate, early functional rehabilitation and improving range of motion [1]. As a dangerous complication, hypoxemia is usually accompanied by several unfavourable consequences, including prolonged ventilator support, increased hospital length of stay, increased intensive care unit (ICU) length of stay, and higher perioperative mortality [2]. However, there were no studies on the risk factors of postoperative hypoxemia after shoulder arthroscopic surgery. From the perspective of the anesthesiologists, this study aims to investigate independent risk factors of postoperative hypoxemia in the post anesthesia care unit(PACU)with patients undergoing shoulder arthroscopic surgery, to prevent and treat postoperative hypoxemia.
The study was in accordance with the Declaration of Helsinki [3]. Institutional review board (IRB) approval was obtained prior to this study by the LuoYang Orthopedic Hospital of Henan Province Orthopedic Hospital of Henan Province IRB (IRB number:2019HL039). All patients provided written informed consent. We began a single-center, retrospective study of risk factors of postoperative hypoxemia in the in the PACU after shoulder arthroscopic surgery. From January 2020 to January 2021, electronic medical records and laboratory results were reviewed for a total of 358 patients undergoing shoulder arthroscopic surgery. Inclusion criteria included patients aged 18–75 years old, American society of anesthesiologists (ASA) physical status classification I-III. All the patients were resuscitated in the PACU after operation. We excluded the patients with preoperative hypoxemia [saturation of peripheral oxygen (SpO2) ≤ 90%], combined surgery of other parts, and those who were directly sent to general ICU after operation.
Standard general anaesthetic management with endotracheal intubation was used. 0.25% ropivacaine 15 ml was given to patients combined with ultrasound guided interscalene block (ISB). Some patients were given tranexamic acid (TXA) intravenously to reduce the intraoperative bleeding before the surgery. After anesthesia the patients were placed in the lateral decubitus position, we taken a brace with a bandage aligned for support. We placed the operative arm into a foam traction sleeve connected to a traction device. By a gravity fluid control system, 0.9% normal saline(3L/bag) without epinephrine was used for intraarticular irrigation. We increased the irrigation fluid pressure if the bleeding affected the surgical field and couldn't be controlled by ablation. The blood pressure was strictly controlled by using a combination of hypotensive agents and analgesics. The arthroscopic approaches were standardized to all patients. The patients were transferred to PACU for resuscitation after the recovery of spontaneous breathing, some anesthesiologists given muscle relaxation antagonists as appropriate. The patients were monitored with a pulse oximeter continuously from arrival in the PACU until discharge. We placed the sensor on a finger of the arm opposite the blood pressure cuff. An anesthesia nurse observed the patient and monitoring apparatus constantly to ensure the presence of an adequate pulse signal and to eliminate artifacts produced by such events as sensor dislodgement or patient movement. The tracheal tube was removed when the extubation indications were satisfied. All the patient were given oxygen inhalation (2–3 L/minute) through a nasal cannula after extubation, and they were monitored without oxygen inhalation for 15 minutes before they were transferred out of PACU. According to the lowest SpO2 recorded in the PACU, patients were divided into non-hypoxemia group (SpO2 > 90%, 308 cases) and hypoxemia group (SpO2 ≤ 90%, 50 cases).
All data were analyzed by SPSS 25.0 software. The numeration datas were expressed as numbers and percentages (n, %), and analysed by χ2-test. The variables with normal distribution were expressed as mean ± standard deviation ( ± s), and analysed by Student's t test. Datas with a skewed distribution were presented as median (interquartile range) [M (Q1, Q3)], and analysed by Mann–Whitney U-test. All variables with a P value < 0.05 in single-factor analysis were performed for further multivariate analysis using a logistic regression model. A P value < 0.05 was considered statistically significant.
Of the 358 subjects examined in this study, 192 were male and 166 were female. The average age was 59 ± 14 years, the average body mass index (BMI) was 22.7 ± 3.0 kg/m2, and ASA classification was I to III. 50 cases developed postoperative hypoxemia, accounting for 14%. The descriptive analysis of preoperative factors is presented in Tables 1 and intraoperative factors in Table 2.
|
Factor |
Hypoxemia group (n = 50) |
Non-hypoxemia group(n = 308) |
P value |
||
|---|---|---|---|---|---|
|
Gender |
male [n (%)] |
23(46.0) |
169(54.9) |
0.243 |
|
|
Age (y, ±s) |
58 ± 7 |
56 ± 7 |
0.045* |
||
|
BMI (kg/m2, ±s) |
25.7 ± 4.2 |
22.9 ± 2.4 |
0.000* |
||
|
Smoking history [n (%)] |
15(30.0) |
51(16.6) |
0.023* |
||
|
Hypertension history [n (%)] |
24(48.0) |
149(48.4) |
0.961 |
||
|
Heart disease history [n (%)] |
19(38.0) |
71(30.2) |
0.270 |
||
|
Chronic pulmonary disease history [n (%)] |
26(50.0) |
50(16.2) |
0.000* |
||
|
Hemoglobin (g/l, ±s) |
138 ± 16 |
134 ± 15 |
0.104 |
||
|
Platelet count (*109/L, ±s) |
190 ± 54 |
194 ± 61 |
0.635 |
||
|
Abnormal lung CT [n (%)] |
25(50.0) |
51(16.6) |
0.000* |
||
|
ASA classification |
Ⅰ [n (%)] |
18(36.0) |
108(35.1) |
0.086 |
|
|
Ⅱ [n (%)] |
28(56.0) |
193(62.7) |
|||
|
Ⅲ [n (%)] |
4(8.0) |
7(2.0) |
|||
| Note: * represents P < 0.05 | |||||
|
Factor |
Hypoxemia group (n = 50) |
Non-hypoxemia group (n = 308) |
P value |
|
|---|---|---|---|---|
|
Methods |
General anesthesia [n (%)] |
9(18.0) |
36(11.7) |
0.212 |
|
Combined ISB [n (%)] |
41(82.0) |
272(88.3) |
||
|
Operating time (min) |
113(90,153) |
95(78,121) |
0.000* |
|
|
Irrigation fluid volume [l, M (Q1, Q3)] |
20.5(18.0,23.3) |
15.0(11.0,19.0) |
0.000* |
|
|
Infusion volume [ml, M (Q1, Q3)] |
700(500,800) |
700(600,800) |
0.810 |
|
|
Sufentanil concentration [ug/kg/h, M (Q1, Q3)] |
0.22(0.20,0.25) |
0.21((0.20,0.22) |
0.498 |
|
|
Remifentanil concentration [ug/kg/h, M (Q1, Q3)] |
3.70((3.26,3.26) |
3.60(3.96,3.86) |
0.167 |
|
|
Intravenous tranexamic acid [n (%)] |
12(76.0) |
190(84.8) |
0.178 |
|
|
Muscle relaxant antagonist [n (%)] |
15(30.0) |
82(26.6) |
0.618 |
|
|
Controlled hypotension [n (%)] |
36(72.0) |
193(62.7) |
0.202 |
|
| Note: * represents P < 0.05 | ||||
There were statistically significant differences in age, BMI, smoking history of lung disease, chronic pulmonary disease history, abnormal chest computed tomography, operating time and irrigation fluid volume (p < 0.05). These factors were used as independent variables to conduct multivariate Logistic regression analysis. The results showed that age, BMI, operating time, and irrigation fluid volume were independent risk factors for postoperative hypoxemia to patients undergoing shoulder arthroscopy (p < 0.05) (Table 3).
|
Factor |
β |
OR |
95%CI |
P value |
|---|---|---|---|---|
|
Age |
0.066 |
1.068 |
1.012–1.128 |
0.017* |
|
BMI |
0.369 |
1.446 |
1.262–1.658 |
0.000* |
|
Smoking history |
0.289 |
1.335 |
0.613–2.908 |
0.468 |
|
Chronic pulmonary disease history |
1.287 |
3.622 |
0.851–15.421 |
0.082 |
|
Abnormal chest computed tomography |
0.683 |
1.981 |
0.456–8.596 |
0.362 |
|
Operating time |
0.011 |
1.011 |
1.000-1.021 |
0.041* |
|
Irrigation fluid volume |
0.057 |
1.059 |
1.014–1.105 |
0.009* |
| Note: * represents P < 0.05 | ||||
β,coefficient; OR, odds ratio; CI, confidence interval
Many cases reported complications such as respiratory distress, tracheal displacement, pleural effusion, pulmonary edema, pneumothorax and possibly death after the shoulder arthroscopy surgery [4]. Postoperative hypoxemia, as a life-threatening postoperative complication, might be attributed to prolonged mechanical ventilation and PACU length of stay, which shouldn't be ignored after shoulder arthroscopic surgery. To the different purposes and methods of the research, the incidence of hypoxemia after shoulder arthroscopic surgery was 12.6% [5]and 16% [6], while it was 14% in our study. Through univariate analysis, the risk factors were age, BMI, smoking history, chronic pulmonary disease history, abnormal chest computed tomography, operating time and irrigation fluid volume. Furthermore, through logistic regression, the independent risk factors of hypoxemia in the PACU after shoulder arthroscopic surgery were as follows: age, BMI, operating time, irrigation fluid volume.
Among the preoperative factors, age and BMI were independent risk factors for hypoxemia. Khirfan G et al confirmed that patients with hypoxemia had older age, greater body mass index, higher prevalence of cardiovascular risk factors, worse functional capacity and pulmonary function [7]. Lumachi et al also indicated that in obese patients, the severity of hypoxemia was mainly related to age. Age was associated with postoperative hypoxemia, which might be due to the increasing of cardiopulmonary complications with older age [8]. For obese patients, respiratory resistance was increasing, lung compliance was worse, and cardiovascular system and respiratory complications were often accompanied. At the same time, proinflammatory factor and vascular active substances were releasing more, oxidative stress might lead to alveolar damage directly. Compared with normal patients, obese patients were more likely to suffer postoperative hypoxemia [9]. Smoking, chronic pulmonary disease, and abnormal lung computed tomography were not independent risk factors for hypoxemia in our study, but they were risk factors through univariate analysis. Decreased lung compliance, decreased vital capacity and maximal ventilation and alveolar damage, might cause restrictive or obstructive ventilation disorders, which could also influence ventilation/perfusion imbalance, ultimately impairing the gas exchange function, leading to the occurrence of hypoxemia [10]. In conclusion, we could reduce the incidence of postoperative hypoxemia by lowering preoperative BMI and optimizing the pulmonary condition of patients with chronic pulmonary diseases.
Among the intraoperative factors, operative time and irrigation fluid volume were independent factors for hypoxemia. Irrigation fluid accumulated in the neck, flowed into the para-tracheal space and the para-carotid space, obstructed lymphatic return, and formed edema in these areas, resulting in airway compression and even obstruction [11]. Edema of chest wall tissue might reduce the compliance of the lung and affect the function of respiratory muscles. Irrigation fluid accumulating in the chest and neck might also spread into the thoracic cavity or the lung interstitium, leading to limited oxygen diffusion function, even life-threatening pulmonary edema [12].While there was no established upper limit regarding the amount of irrigation fluid to be used during shoulder arthroscopic surgery, studies of symptomatic patients reported a range of volumes from 20 to 36 L, and as such, volumes lower than 20 L might be considered safe until more precise estimates were determined [4]. Total operative time was directly proportional to the volume of irrigation fluid used and subsequent weight gain by the patient, presumably from absorption of the irrigation fluid. Although there was no clear safe upper limit for operative times, some authors suggested limiting surgical time to between 90 and 120 minute to reduce this risk [13].
Continuous high-pressure perfusion was used for intraarticular irrigation by a gravity fluid control system for visual clarity in the surgery. We conducted a relative analysis on factors related to postoperative edema, although these factors were not risk factors for postoperative hypoxemia. There was a direct correlation between systolic blood pressure (SBP), subacromial space pressure (SASP), and the clarity of the visual field. Maintaining a pressure difference (SBP-SASP) of 49 mm Hg on average could less bleeding and permit good visual clarity. Furthermore, hypotensive anesthesia permitted lower irrigation pressure and reduced the risk of fluid extravasation into the subcutaneous tissues of the shoulder significantly [14]. Since the exact pressure of the irrigation fluid could not be recorded in our study, it was not statistically analyzed as a variable. It was an alternative way of intravenous administration of TXA to reduce the bleeding and improve visual clarity in arthroscopic shoulder surgery, in the meantime, administration of TXA could also reduce edema caused by fluid extravasation [15] to reduce the incidence of hypoxemia. In patients undergoing arthroscopic shoulder surgery, general anesthesia combined with ISB was associated with a lower heart rate, lower pain scores, lower intraoperative systolic blood pressure, shorter extubation time and lower incidence of adverse events compared with general anesthesia alone [16]. But for patients with BMI ≥ 30 kg/m2 undergoing arthroscopic shoulder surgery, high volume ISB was found to be responsible for diaphragmatic paralysis, dyspnea, occurrence of hypoxic episodes. In our anesthesiology department, lower volume and concentration ISB was used, and the injection site was as far away as possible from the location of the phrenic nerve, which might be helpful to reduce diaphragmatic paralysis.
There were some limitations to this study. First, routine blood gas analysis after surgery was not available for every patient, the SpO2 was the only indicator for evaluating hypoxemia. There might be errors and inaccuracies. Second, not every patient got routine blood test after the surgery, the effect of hemoglobin reduction to hypoxemia was not analyzed in this study. At last, this was a single-center retrospective study. It was impossible to collect and analyze all the relevant factors, multi-center, large sample, randomized controlled clinical trials are needed for further confirmation.
Age, BMI, operating time, irrigation fluid volume are 4 independent risk factors for postoperative hypoxemia in the PACU after shoulder arthroscopic surgery.
increased intensive care unit
post anaesthesia care unit
odd ratio
confidence interval
saturation of peripheral oxygen
American society of anesthesiologists
interscalene block
body mass index
median (interquartile range)
systolic blood pressure
subacromial space pressure
tranexamic acid
Ethics approval and consent to participate
The study was in accordance with the Declaration of Helsinki. Institutional review board (IRB) approval was obtained prior to this study by the LuoYang Orthopedic Hospital of Henan Province Orthopedic Hospital of Henan Province IRB (IRB number:2019HL039). All patients provided written informed consent.
Consent for publication
Not applicable.
Availability of data and materials
The datasets used and analysed during the current study are available from the corresponding author on reasonable request.
Competing interests
The authors declare that they have no conflict of interest.
Funding
We hereby confirm that no outside funding or grants were received in support of the research or the preparation of the paper. Furthermore, we also confirm that none of the authors or any of their immediate families received any payments or commitments from any commercial entity.
Authors' contributions
Wenchao Chen and Guojun Yu desinged the study, Wenchao Chen, Fanyou Ning and Zhe Yuan analysed the datas ; Wenchao Chen wrote the main manuscript. All authors reviewed and approved the manuscript.
Acknowledgements
We thank all patients involved in the study.
Author details
1 Department of Anesthesiology and Perioperative Medicine, LuoYang Orthopedic Hospital of Henan Province Orthopedic Hospital of Henan Province, Luoyang, Henan Province, 471002, China.
2 Department of Shoulder and Elbow, LuoYang Orthopedic Hospital of Henan Province Orthopedic Hospital of Henan Province, Luoyang, Henan Province, 471002, China.