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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 44  |  Issue : 2  |  Page : 58-63

Influence of severity of obstructive sleep apnea on postoperative pulmonary complications in patients undergoing gastroplasty


Department of Anesthesia and Surgical Intensive care, Faculty of Medicine, Tanta University, Tanta, Egypt

Date of Submission05-Jan-2016
Date of Acceptance19-May-2016
Date of Web Publication29-Aug-2016

Correspondence Address:
Rehab S EL-kalla
Department of Anesthesia and Surgical Intensive care, Faculty of Medicine, Tanta University, EL Gheish street, Tanta 31257
Egypt
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DOI: 10.4103/1110-1415.189347

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  Abstract 

Introduction
Obstructive sleep apnea (OSA) is a common comorbidity in morbid obese patients scheduled for gastroplasty. The objective of our study was to determine the relationship between postoperative pulmonary complications and the severity of OSA in patients undergoing gastroplasty, who were evaluated preoperatively by using polysomnography.
Methods
All patients with BMI greater than or equal to 50 kg∕m2 were selected and referred to the sleep lab to detect OSA. Patients with apnea hypopnea index (AHI) less than 16 were excluded. Patients with AHI greater than or equal to 16 were divided into two groups according to the severity of AHI: patients with AHI in the range 16–30 were classified as having moderate OSA (group I) and patients with AHI greater than 30 were classified as having severe OSA (group II). In total, 40 patients were divided into two equal groups. Pulmonary complications in the first 24 h were analyzed according to the AHI.
Results Overall, 15% patients of group I and 25% of group II received preoperative continuous positive airway pressure therapy, and postoperatively, all patients were closely monitored either in the Postanesthetic Care Unit or in the ICU. The rate of incidence of the postoperative pulmonary complications was not increased with increased the severity of OSA.
Conclusion In obese patients with OSA, the severity of which was assessed by using the AHI, the incidence of postoperative pulmonary complications did not increase with increased severity of OSA. Appropriate preoperative evaluation and preparation with meticulous perioperative monitoring lead to a decrease in pulmonary complications, despite the severity of OSA.

Keywords: apnea hypopnea index, gastroplasty, morbid obesity, obstructive sleep apnea, polysomnography, pulmonary complication


How to cite this article:
Dowidar ARM, Basuni AS, EL-kalla RS, Eid GM. Influence of severity of obstructive sleep apnea on postoperative pulmonary complications in patients undergoing gastroplasty. Tanta Med J 2016;44:58-63

How to cite this URL:
Dowidar ARM, Basuni AS, EL-kalla RS, Eid GM. Influence of severity of obstructive sleep apnea on postoperative pulmonary complications in patients undergoing gastroplasty. Tanta Med J [serial online] 2016 [cited 2019 Nov 17];44:58-63. Available from: http://www.tdj.eg.net/text.asp?2016/44/2/58/189347


  Introduction Top


Obstructive sleep apnea (OSA) is a common comorbidity in morbid obese patients scheduled for gastroplasty. More than 70% of morbidly obese patients suffer from OSA, and there is a particular association between OSA and the visceral pattern of obesity [1].

OSA is a repetitive partial (hypopnea) or complete (apnea) obstruction of the upper airway and is accompanied by episodes of cessation of respiration during sleep for more than 10 s, despite respiratory effort [2]. The main symptoms of sleep apnea are heavy snoring, sudden arousal from sleep, which may be accompanied by chocking, apneas witnessed by a bed partner, and excessive daytime sleepiness [3],[4]. Patients, usually, have a thick, short neck, and limited space in the oropharynx, with prominent tonsils and bulky tongue [2].

The apnea hypopnea index (AHI) is the number of apneas and hypopneas per hour of sleep; it is the current gold standard test for assessing the severity of OSA [4]. OSA was classified according to the AHI as none (AHI≤4), mild (AHI 5–15), moderate (AHI 16–30), and severe (AHI≥31) [1].

After a major surgery, obese patients are at an increased risk for pulmonary complications such as aspiration, pneumonia, and requirement for continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) in patients who did not use it before operation, postoperative tracheal intubation, and mechanical ventilatory support after discharge from the recovery room. But the severity of OSA and relationship between the frequency of these complications is still under investigation.

The present study was designed to evaluate the relation between the severity of OSA and postoperative pulmonary complications in morbidly obese patients undergoing gastroplasty.


  Methods Top


The study was carried out at Tanta University Hospital, Tanta, Egypt. After the Institutional Review Board approval (code number: 500/03/11), a written informed consent was obtained from the patients. Forty patients of both sexes who were scheduled for gastroplasty, in addition to being above 187 years of age, belonging to American Society of Anesthesiologists physical status II and III, with BMI of atleast 50 kg/m2 and AHI of atleast 16 and failing in weight reduction by physical and medical means, were enrolled in the study. They were allocated into two groups: group I (moderate OSA), which comprised 20 patients with AHI in the range 16–30, and group II (severe OSA), which comprised 20 patients with AHI greater than 30. Patients with BMI of less than 50 kg/m2, AHI of less than 16, history of drug abuse, mental disorder, or any uncontrolled neurologic, cardiovascular, renal, or hepatic diseases were excluded from the study.

Preoperatively, patients were subjected to careful history taking and clinical examination; investigations included complete blood picture, prothrombin time and activity, liver and renal function tests, chest radiography, ECG, echocardiography, and polysomnography (PSG). The PSG (Nicolet, New York, United States) was carried out 1 week before surgery; patients were admitted to the sleep laboratory 2 h before their usual time of sleep so as to give them time to get accustomed to the place. They were asked to stop any sedative or hypnotic medications two days before the date of admission; only their essential drugs (e.g. antihypertensive, antidiabetics) were allowed.

Patients were fasted (6 h for solid matter and 2 h for clear fluids) before the time of surgery according to the American Society of Anesthesiologists preprocedure fasting guidelines. Pantoperazole (Controloc; Bayer, Leverkusen, Germany) 40 mg was administered intravenously 2 h before surgery to reduce the risk for aspiration.

Patients were monitored using ECG, SaO2%, end-tidal CO2, heart rate, noninvasive blood pressure, and arterial blood gas (ABG) analysis. Anesthesia was induced with propofol (Fresenius, Bad Homburg, Germany) 2 mg/kg ideal body weight (IBW), cis-atracurium (Nimbex; GlaxoSmithkline, Brentford, UK) 0.15–0.2 mg/kg low birth weight, and fentanyl (Janssen-Pharmaceutica, Geel, Belgium) 1–2 μg/kg IBW. Trachea was intubated with cuffed endotracheal tube with appropriate size as per the patient’s sex. Anesthesia was maintained with 60% oxygen, with air and isoflorane (AIT) 1.2–2%. Tidal volume and respiratory rate were adjusted to maintain minute ventilation between 7 and 9 l/min, with a positive endexpiratory pressure of 5–10 cm H2O.

At the end of surgery, anesthesia was discontinued; muscle relaxation was reversed using neostigmine (0.04 mg/kg IBW) and atropine (0.01–0.02 mg/kg IBW), and patients were extubated in the semisitting position. They were transferred to the Postanesthetic Care Unit (PACU). CPAP or BiPAP was routinely used for all patients preoperatively. Oxygen face mask (4–6 l/min) was used for those who were not put on CPAP/BiPAP preoperatively, and they were evaluated every 10 min. If desaturation persisted (O2%<90% on O2 mask), CPAP was used. Patients’ condition was assessed every 30 min; if desaturation persisted after using CPAP, BiPAP was used. Aspiration was managed through suction, or tracheal reintubation and mechanical ventilation. Respiratory depression was managed through a mechanical ventilator support. Respiratory arrest was managed through tracheal reintubation and mechanical ventilation.

The following data were recorded: oxygen saturation (SaO2) and ABG, immediately on admission at the PACU, and then continuously monitored and recorded every 4 h during the first 24 h preoperatively; and pulmonary complications including episodes of hypoxia (persistent SaO2<95% for 5 min despite O2 supplement), aspiration, need for noninvasive ventilation in patients who did not use it preoperatively or tracheal reintubation and invasive mechanical ventilation postoperatively, admission to ICU, and mortality.

Statistical analysis

The collected data analyzed using SPSS, version 19 (SPSS Inc., Chicago, Illinois, USA). Numerical variables were presented as range, mean and SD. The difference of mean value between groups I and II were tested by Student’s test. Categorical variables were presented as number and percentages. Differences between observations of different categories of each variable were statistically analyzed using χ2-test. When χ2 was not found appropriate due to presence of small observation with expected value less than 5, Fisher exact test was used. The level of significance was adopted at P less than 0.05.


  Results Top


Results were presented only for 40 patients. In total, 44 patients were enrolled in this study; four of them were eliminated from data analysis for the following reasons: surgery was cancelled for two patients and the remaining two patients had incomplete data and thus were excluded from data analysis.

In comparison between the two groups, there was no significant difference as regards the mean values of age, sex, height, surgical approach, and duration of surgery (P>0.05) [Table 1], but there was a significant difference as regards weight, BMI, and AHI (P<0.05).
Table 1 Demographic data

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Higher BMI was associated with an increased incidence of associated comorbidities (P<0.05).

Despite using oxygen face mask for all patients, during emergency, three patients in group I and six patients in group II developed laryngospasm [Figure 1]. There was an insignificant difference as regards oxygen saturation (P>0.05). In group II, two patients had a persistent desaturation 30 min after arrival to PACU. There was insignificant difference in the mean values of pH of both groups [Figure 2] at all the predetermined times (P>0.05). In both groups, patients with low PaO2 on room air were given O2 mask so as to improve PaO2. There was insignificant difference in the mean values of the partial arterial oxygen tension (PaO2) [Figure 3] between the two groups at all the predetermined times (P>0.05). There was an insignificant difference in the partial carbon dioxide (PaCO2) tension [Figure 4] of the two groups at all the predetermined times (P>0.05).
Figure 1 postoperative oxygen saturation changes: there was insignificant difference in the oxygen saturation (P>0.05).

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Figure 2  pH changes: there was an insignificant difference in the mean values of pH (P>0.05).

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Figure 3 The PaO2 changes: there was an insignificant difference in the partial arterial oxygen tension (P>0.05).

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Figure 4 The PaCO2 changes: there was an insignificant difference in the partial carbon dioxide tension (P>0.05).

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There was an insignificant difference as regards using CPAP [Table 2] between patients of the two groups, either preoperatively or postoperatively (P>0.05).
Table 2 Application of CPAP

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As regards the incidence of postoperative pulmonary complications [Table 3], 15 (75%) patients in group I and 17 (85%) patients in group II developed postoperative hypoxemia (SaO2<95%) on O2 mask; one patient (5%) in group I and three (15%) patients in group II required noninvasive ventilation; whereas of the patients developed aspiration or needed tracheal reintubation and mechanical ventilation.
Table 3 Pulmonary complications and clinical outcome

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In group I, four (20%) patients were admitted to ICU and 16 (80%) patients were transferred to the ward from PACU. In group II, 7 (35%) patients were admitted to the ICU, whereas 13 (65%) patients were transferred to the ward from PACU.


  Discussion Top


The prevalence of obesity is rapidly increasing worldwide. Anesthesiologists consider morbidly obese patients with central fat distribution a challenge [5]. Obesity may be associated with OSA, hypertension, stroke, depression, and diabetes [6]. OSA may have serious implications for anesthetic management [7],[8].

In the present study, all patients were referred for PSG. Information reported from preoperative PSG included AHI according to which the OSA severity was categorized. Patients who used CPAP before operation were instructed to bring their CPAP device to the hospital. Three patients from group I and five patients from group II were prescribed CPAP preoperatively, and were advised to routinely use it postoperatively.

In agreement with our results, Huerta et al. [9] recommended the routine use of postoperative CPAP for Roux-en-Y gastric bypass patients with CPAP-dependant OSA. In addition, Weingarten et al. [1] reported that CPAP or BiPAP should be reinstituted at admission to the PACU in all patients who had them prescribed before operation.

We observed the complications that might occur in OSA patients in the first 24 h postoperatively, which included hypoxemia, aspiration, respiratory depression, and need for tracheal reintubation and invasive mechanical ventilation. Postoperative hypoxemia was the most frequently occuring pulmonary complication in all patients. Hypoxemia, in most cases, was managed by providing supplemental oxygen via a face mask (4–6 l/min), except for those using CPAP preoperatively.

In agreement with our results, Nagle et al. [10] reported that when supplemental oxygen was administered during the 24 h postoperatively, it reduced the frequency and severity of hypoxemic attack and improved oxygen saturation.

Liao et al. [11] and Pereira et al. [12] noted that hypoxemia (oxygen desaturaion) was the most common postoperative complication in patients with OSA.

As regards oxygen saturation, there was no significant difference between the two groups either preoperatively or intraoperatively. Postoperatively, oxygen saturation was decreased (SaO2<95%) after emergence from anesthesia in both groups.

In agreement with our results, Ahmad et al. [10] postulated that there was a significantly greater risk for postoperative hypoxemic episodes in the first 24 h after the bariatric surgery.

Our results revealed that 17 patients from group I (moderate OSA) and 15 patients from group II (severe OSA) improved on oxygen mask 1 h after extubation, except that one patient from each group showed persistent hypoxemia, which was accompanied by decreased peripheral oxygen saturation and PaO2. For these two patients, initiation of CPAP was a must and they improved after 1 h (CPAP at 5 cm H2O at first, then the pressure increased gradually. If CPAP, set at a high pressure of 12 cmH2O, failed to improve the condition, BIPAP was used). In group II, five patients were prescribed CPAP: two patients deteriorated and hypoxemia persisted. Therefore, BIPAP therapy (inspiratory pressure 10–12 cm H2O, expiratory pressure 4–8 cm H2O) was planed. Hypoxemia was significantly improved after 2 h of BiPAP therapy, there was an improvement in gas exchange, atelectasis was minimized, and there was an increase in the functional residual capacity. It has been shown previously that pre-emptive initiation of either mode reduces the overall pulmonary complications [13]. BiPAP in the spontaneous mode prevents both complete upper airway obstruction and the desaturations events associated with persistent partial obstructions at a mean pressure lower than that of CPAP [14]. After the initial failure of CPAP, BiPAP leads to a sufficient treatment of the apnea-hypopnea and hypoventilation [15].

In contrast to our results, Chung et al. [16] concluded that the use of noninvasive positive pressure ventilation for postoperative prevention of airway obstruction in patients with OSA gives contradictory results.

None of the cases included in our study needed endotracheal intubation or mechanical ventilation.

In agreement with our results, Schumann et al. [17] revealed that early treatment of postoperative hypoxemia with noninvasive positive pressure ventilation reduces the incidence of reintubation.

In contrast to our results, Memtsoudis et al. [18] reported a five-fold increase in the intubation and mechanical ventilation among OSA patients undergoing noncardiac surgery, and, also, acute respiratory distress syndrome was reported as a complication for the first time. They attributed this to the higher incidence of aspiration and acute respiratory distress syndrome, which partially explain the increased need for postoperative intubation and ventilation among sleep apnea patients.

Our results revealed no significant difference in the ABGs as regards Ph, PaO2, and PaCO2 between the studied groups. A significant increase was observed in PaO2 after starting mechanical ventilation intraoperatively in each group, and then it significantly decreased after emergence from anesthesia and began to increase after starting oxygen face mask, and CPAP or BiPAP therapy for each group. All patients were normocapenic and there were no significant difference in PaCO2 between the studied groups.

In agreement with this, Zoremba et al. [19] noted that at first assessment in the PACU, the groups showed a similar reduction in the oxygen partial pressure and that there was no hypercapenia. In contrast to our results, Mador et al. [20] reported acute hypercapenia and PaCO2 of atleast 45 mmHg or increase of 5 mmHg after the baseline ABG analysis.

Patients were transferred from the operating room to the PACU for re-evaluation. Most patients were stable and were transferred to the ward (most of them underwent laparoscopic surgery). These patients had the least BMI, AHI, and fewer comorbidities. Only four patients from group I and seven from group II stayed in the ICU for the night of the operation.

Moreover, Weingarten et al. [1] reported that patients with more severe OSA had a greater BMI and were in need of an open operation, and, also, that laparoscopic operations were associated with a lesser complication rate.

In our study, there was no clinically significant difference in the incidence of postoperative pulmonary complications between the two groups. In other words, there was no increase in the occurrence of postoperative pulmonary complications with increasing severity of OSA.

In agreement with our results, Gupta et al. [21] postulated that patients who were using CPAP preoperatively had a lower incidence of postoperative pulmonary complications and shorter hospital stay compared with those who were not using CPAP therapy, and also that the severity of OSA, as measured by using the total respiratory disturbance index, was not associated with postoperative complications.


  Conclusion Top


Assessment of the severity of OSA using AHI is better than by using the old standard techniques, as was evident in our study. The incidence of postoperative pulmonary complications did not increase with increased severity of OSA. Appropriate preoperative evaluation and preparation with meticulous perioperative monitoring lead to a lessening in pulmonary complications, despite the severity of OSA.

Acknowledgements

The researchers supported this work fund.

Authors’ Contributions: All authors had equal role in design, work, statistical analysis and manuscript writing. All authors have approved the final article work.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]


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