Pulmonary atelectasis after anaesthesia: pathophysiology and management

Efficacy of ventilator for patients with atelectasis: A systematic review protocol of randomized controlled trials

BACKGROUND

This study aims to assess the efficacy and safety of ventilator for the treatment of atelectasis.

METHODS

We will search Cochrane Library, MEDLINE, EMBASE, CINAHL, EBSCO, Chinese database Chinese Biomedical Literature Database, China National Knowledge Infrastructure, and Wanfang data from inceptions to June 30, 2019 without language limitations. We will include randomized controlled trials (RCTs) of ventilator on evaluating the efficacy and safety of ventilator for atelectasis. We will use Cochrane risk of bias tool to assess the methodological quality for all included RCTs. RevMan 5.3 software will be used for statistical analysis.

RESULTS

The primary outcome is lung function. The secondary outcomes comprise of airway pressure, mean arterial pressure, arterial blood gas, heart rate, respiratory rate, oxygen saturation, and adverse events.

CONCLUSION

The findings of this study will provide most recent evidence of ventilator for the treatment of atelectasis.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019139329.

Augmented breaths ('sighs') are suppressed by morphine in a dose-dependent fashion via naloxone-sensitive pathways in adult rats

Morphine treatment can eliminate augmented breaths (ABs; 'sighs') during spontaneous breathing. In the present study, unanesthetized rats were studied to: (1) determine the involvement of naloxone-sensitive receptor pathways, and (2) establish the dose-response relationship of this side effect. At a dosage of 5mg/kg (2-10mg/kg is recommended range for analgesia) morphine eliminated ABs from the breathing rhythm across nearly 100 min post-administration (vs. 6.2 ± 1.6 ABs in 15 min, control condition, p<0.001). This occurred despite no apparent effect on indices of ventilation. By contrast, when naloxone was co-administered with morphine, the occurrence of ABs was not different compared to control. The suppression of ABs by morphine followed a sigmoidal pattern across the low-mid dosage range (R(2)=0.83), whereas tidal volume and breathing frequency were unaffected. We conclude that the opioid-induced suppression of ABs is mediated by naloxone-sensitive opioid receptor pathways, and that this side effect is potent across the low-mid dosage range, and cannot be simply avoided by restricting dosage.

Activation of opioid micro-receptors in medullary raphe depresses sighs

Sighs, a well-known phenomenon in mammals, are substantially augmented by hypoxia and hypercapnia. Because (d-Ala(2),N-Me-Phe(4),Gly-ol)-enkephalin (DAMGO), a mu-receptor agonist, injected intravenously and locally in the caudal medullary raphe region (cMRR) decreased the ventilatory response to hypoxia and hypercapnia, we hypothesized that these treatments could inhibit sigh responses to these chemical stimuli. The number and amplitude of sighs were recorded during three levels of isocapnic hypoxia (15%, 10%, and 5% O(2) for 1.5 min) or hypercapnia (3%, 7%, and 10% CO(2) for 4 min) to test the dependence of sigh responses on the intensity of chemical drive in anesthetized and spontaneously breathing rats. The role of mu-receptors in modulating sigh responses to 10% O(2) or 7% CO(2) was subsequently evaluated by comparing the sighs before and after 1) intravenous administration of DAMGO (100 microg/kg), 2) microinjection of DAMGO (35 ng/100 nl) into the cMRR, and 3) intravenous administration of DAMGO after microinjection of d-Phe-Cys-Tyr-d-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP, 100 ng/100 nl), a micro-receptor antagonist, into the cMRR. Hypoxia and hypercapnia increased the number, but not amplitude, of sighs in a concentration-dependent manner, and the responses to hypoxia were significantly greater than those to hypercapnia. Systemic and local injection of DAMGO into the cMRR predominantly decreased the number of sighs, while microinjection into the rostral and middle MRR had no or limited effects. Microinjecting CTAP into the cMRR significantly diminished the systemic DAMGO-induced reduction of the number of sighs in response to hypoxia, but not to hypercapnia. Thus we conclude that hypoxia and hypercapnia elevate the number of sighs in a concentration-dependent manner in anesthetized rats, and this response is significantly depressed by activating systemic mu-receptors, especially those within the cMRR.

Chest physiotherapy during immediate postoperative period among patients undergoing upper abdominal surgery: randomized clinical trial

CONTEXT AND OBJECTIVE

Abdominal surgical procedures increase pulmonary complication risks. The aim of this study was to evaluate the effectiveness of chest physiotherapy during the immediate postoperative period among patients undergoing elective upper abdominal surgery.

DESIGN AND SETTING

This randomized clinical trial was performed in the post-anesthesia care unit of a public university hospital.

METHODS

Thirty-one adults were randomly assigned to control (n = 16) and chest physiotherapy (n = 15) groups. Spirometry, pulse oximetry and anamneses were performed preoperatively and on the second postoperative day. A visual pain scale was applied on the second postoperative day, before and after chest physiotherapy. The chest physiotherapy group received treatment at the post-anesthesia care unit, while the controls did not. Surgery duration, length of hospital stay and postoperative pulmonary complications were gathered from patients' medical records.

RESULTS

The control and chest physiotherapy groups presented decreased spirometry values after surgery but without any difference between them (forced vital capacity from 83.5 +/- 17.1% to 62.7 +/- 16.9% and from 95.7 +/- 18.9% to 79.0 +/- 26.9%, respectively). In contrast, the chest physiotherapy group presented improved oxygen-hemoglobin saturation after chest physiotherapy during the immediate postoperative period (p < 0.03) that did not last until the second postoperative day. The medical record data were similar between groups.

CONCLUSIONS

Chest physiotherapy during the immediate postoperative period following upper abdominal surgery was effective for improving oxygen-hemoglobin saturation without increased abdominal pain. Breathing exercises could be adopted at post-anesthesia care units with benefits for patients.

Prone equals prone? Impact of positioning techniques on respiratory function in anesthetized and paralyzed healthy children

OBJECTIVES

Although the prone position is effectively used to improve oxygenation, its impact on functional residual capacity is controversial. Different techniques of body positioning might be an important confounding factor. The aim of this study was to determine the impact of two different prone positioning techniques on functional residual capacity and ventilation distribution in anesthetized, preschool-aged children.

DESIGN

Functional residual capacity and lung clearance index, a measure of ventilation homogeneity, were calculated using a sulfur-hexafluoride multibreath washout technique. After intubation, measurements were taken in the supine position and, in random order, in the flat prone position and the augmented prone position (gel pads supporting the pelvis and the upper thorax).

SETTING

Pediatric anesthesia unit of university hospital.

PATIENTS AND PARTICIPANTS

Thirty preschool children without cardiopulmonary disease undergoing elective surgery.

MEASUREMENTS AND RESULTS

Mean (range) age was 48.5 (24-80) months, weight 17.2 (10.5-26.9) kg, functional residual capacity (mean +/- SD) 22.9+/- 6.2 ml.kg (-1) in the supine position and 23.3 +/- 5.6 ml.kg (-1) in the flat prone position, while lung clearance indices were 8.1 +/- 2.3 vs. 7.9 +/- 2.3, respectively. In contrast, functional residual capacity increased to 27.6 +/- 6.5 ml.kg (-1) (p< 0.001) in the augmented prone position while at the same time the lung clearance index decreased to 6.7 +/- 0.9 (p< 0.001).

CONCLUSIONS

Functional residual capacity and ventilation distribution were similar in the supine and flat prone positions, while these parameters improved significantly in the augmented prone position, suggesting that the technique of prone positioning has major implications for pulmonary function.

Pulmonary atelectasis manifested after induction of anesthesia: a contribution of sinobronchial syndrome?

A 31-year-old man underwent general anesthesia for sinus surgery. Anesthesia was induced with midazolam and butorphanol, and an endotracheal tube was orally placed with a bronchoscope, due to difficulty with temporomandibular joint opening. Ventilation difficulty and increased peak inspiratory pressure were noticed shortly after tracheal intubation, and bronchoscopy was performed for diagnosis. The bronchi were filled with a clear mucous secretion. Removal of the secretion improved respiration and decreased the peak inspiratory pressure. A chest roentgenogram taken prior to extubation showed right upper lobe atelectasis. A diagnosis of sinobronchial syndrome was made postoperatively. The etiology of the acutely developed atelectasis was unclear. However, the latent syndrome may have induced excessive airway secretion with stimuli such as endotracheal intubation.

Comparison of perioperative spirometric data following spinal or general anaesthesia in normal-weight and overweight gynaecological patients

BACKGROUND

There is limited data comparing the impact of spinal anaesthesia (SA) and general anaesthesia (GA) on perioperative lung function. Here we assessed the differences of these two anaesthetic techniques on perioperative lung volumes in normal-weight (BMI < 25) and overweight (BMI 25-30) patients using spirometry.

METHODS

We prospectively studied 84 consenting patients having operations in the vaginal region receiving either GA (n = 41) or SA (n = 43). Both groups (GA and SA) were further divided into two subgroups each (normal-weight vs. overweight). We measured vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), midexpiratory (MEF25-75) and peak expiratory flow rates (PEFR) at the preoperative assessment (baseline), after premedication, after effective SA, and 20 min, 1 h, 2 h and 3 h after the operation (last measurement after patient mobilization).

RESULTS

Premedication was associated with a small but significant decrease in lung volumes in direct correlation with BMI (-5%). Spinal anaesthesia resulted in a significant reduction in lung volumes in overweight as opposed to normal-weight patients. Postoperatively, lung volumes were significantly more reduced following GA than SA as indicated by differences in mean VC (SD) of -12 (6)% vs. -6 (5)% 20 min after the end of the operation in the normal-weight and -18 (5)% vs. -10 (5)% in the overweight patients. There was a significant impact of BMI on postoperative respiratory function, which was significantly more important in the GA group than in the SA group, and recovery of lung volumes was more rapid in the normal-weight patients than in the overweight patients, particularly in the SA group.

CONCLUSION

In gynaecological patients undergoing vaginal surgery, the impact of anaesthesia on postoperative lung function as assessed by spirometry was significantly less after SA than GA, particularly in overweight patients.

Effect of obesity and thoracic epidural analgesia on perioperative spirometry

BACKGROUND

Lung volumes in obese patients are reduced significantly in the postoperative period. As the effect of different analgesic regimes on perioperative spirometric tests in obese patients has not yet been studied, we investigated the effect of thoracic epidural analgesia and conventional opioid-based analgesia on perioperative lung volumes measured by spirometry.

METHODS

Eighty-four patients having midline laparotomy for gynaecological procedures successfully completed the study. Premedication, anaesthesia and analgesia were standardized. The patients were given a free choice between epidural analgesia (EDA) (n=42) or opioids (n=42) for postoperative analgesia. We performed spirometry to measure vital capacity (VC), forced vital capacity, peak expiratory flow, mid-expiratory flow and forced expiratory volume in 1 s at preoperative assessment, 30-60 min after premedication and 20 min, 1 h, 3 h and 6 h after extubation.

RESULTS

Baseline values were all within the normal range. All perioperative spirometric values decreased significantly with increasing body mass index (BMI). The greatest reduction in VC occurred directly after extubation, but was less in the EDA group than in the opioid group: mean of -23(sd 8)% versus -30(12)% (P<0.001). In obese patients (BMI>30) the difference in VC was significantly more pronounced than in patients of normal weight (BMI<25): -45(10)% versus -33(4)% (P<0.001). Recovery of spirometric values was significantly quicker in patients receiving EDA, particularly in obese patients.

CONCLUSION

We conclude that EDA should be considered in obese patients undergoing midline laparotomy to improve postoperative spirometry.

Effect of obesity and site of surgery on perioperative lung volumes

BACKGROUND

Although obese patients are thought to be susceptible to postoperative pulmonary complications, there are only limited data on the relationship between obesity and lung volumes after surgery. We studied how surgery and obesity affect lung volumes measured by spirometry.

METHODS

We prospectively studied 161 patients having either breast surgery (Group A, n=80) or lower abdominal laparotomy (Group B, n=81). Premedication and general anaesthesia were standardized. Spirometry was measured with the patient supine, in a 30 degrees head-up position. We measured vital capacity (VC), forced vital capacity, peak expiratory flow and forced expiratory volume in 1 s at preoperative assessment (baseline), after premedication (before induction of anaesthesia) and 10-20 min, 1 h and 3 h after extubation.

RESULTS

Baseline spirometric values were all within the normal range. All perioperative values decreased significantly with increasing body mass index (BMI). The greatest reduction of mean VC (expressed as percentage of baseline values) occurred after extubation, and was more marked after laparotomy than after breast surgery (23 (SD 14)% vs 20 (14)%). Considering patients according to BMI (<25, 25-30, >30), VC decreased after surgery by 12 (7)%, 24 (8)% and 40 (10)%, respectively. VC recovered more rapidly in Group A.

CONCLUSION

Postoperative reduction in spirometric volumes was related to BMI. Obesity had more effect on VC than the site of surgery.

Pulmonary atelectasis after reconstruction with a latissimus dorsi myocutaneous flap

Atelectasis is the most common postoperative complication encountered in head and neck surgery. Risk factors include preexisting pulmonary disease, type of surgery performed, and the length of anesthetic. It is controversial whether reconstruction of defects with regional myogenous flaps predisposes to atelectasis. The latissimus dorsi myocutaneous flap requires the patient to be placed on his side for a period of time. Whether it is the position or the surgery that contributes to the development of atelectasis has not been examined. Eighteen patients underwent latissimus dorsi myocutaneous flap reconstruction following major ablative procedures for head and neck cancer. The cutaneous area transferred ranged from 70 to 225 cm2 (mean, 128 cm2). The flap size ranged from 7 x 10 to 15 x 15 cm. The majority of flaps were 10 x 15 cm or greater. These patients were compared to 18 patients who did not undergo pedicled myocutaneous chest flap reconstruction. Patients were matched for age, sex, length of operation, site of primary, and stage of disease. Postoperative atelectasis was radiographically detected in 89% of flap patients vs. 79% of controls. Major atelectasis was encountered in 16% of patients undergoing flap surgery vs. 11% of patients in the control group. Patients with large cutaneous paddles on the flaps (> 120 cm2) had significantly more atelectasis than patients with smaller cutaneous paddles (P<.05, chi-squared). The incidence of radiographic postoperative atelectasis in patients having a latissimus dorsi myocutaneous flap is high. The size of the skin paddle harvested as well as the position change may contribute to this.

The effect of thoracic epidural analgesia on respiratory function after cholecystectomy

To assess the effect of thoracic epidural analgesia (TEA) on postoperative respiratory function and pulmonary complications, a prospective randomized trial was conducted in patients undergoing cholecystectomy. One hundred patients were allocated to TEA (n = 30), TEA + general anesthesia (TEA + GA) (n = 30), or general anaesthesia (GA) (n = 40) groups. Respiratory function was analysed by measuring forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), functional residual capacity (FRC), total lung capacity (TLC), peak expiratory flow (PEF) in the supine and sitting postures, and arterial blood gases. Postoperative pulmonary complications were carefully documented. TEA significantly prevented the postoperative deterioration of respiratory function as compared with general anaesthesia. FVC, FEV1 and PEF decreased by 20% in patients receiving TEA, in contrast to 55% in patients after GA on the day of operation. This improvement continued until the 2nd day after operation, when FVC, FEV1 and PEF and their recovery rates were equal in all groups. In the sitting posture the preoperative FVC, FEV1 and PEF were about 10% greater than in the supine position. After operation, this difference was further increased. The preoperative difference of 27% in FRC between the sitting and supine postures was maintained after operation. PaO2 decreased by 0.8 kPa after TEA, by 1.5 kPa after TEA + GA with the lowest value on the 2nd postoperative day and by 1.5 kPa after GA, with the lowest value immediately after operation. Simultaneous hypercarbia indicated hypoventilation, which may have contributed to impaired respiratory function on the following days.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaesthetic management of posterior lumbar osteotomy

Sixty-four cases of posterior lumbar extension osteotomy performed at the Toronto East General Hospital between 1969 and 1983 are reviewed. The anaesthetic management is presented. The procedure was performed with local infiltration anaesthesia, heavy sedation and a brief period of general anaesthesia induced with nitrous oxide, halothane or ketamine. Five stages in the anaesthetic management are distinguished, each in relation to a phase of the surgical procedure and drug usage. A method of supporting these deformed patients in the prone position in moulded plaster casts is described. Anaesthetic and surgical complications and postoperative psychological disturbances are described and discussed. It is suggested that caudal epidural opioid or local anaesthetic analgesia be explored as an aid in the management of these patients.

[Postoperative weaning from mechanical ventilation in adults]

Pulmonary complications remain the most frequent of postoperative complications (32-60), especially after upper abdominal surgery (14-41). Chronic respiratory insufficiency (80) also continues to be a major risk factor, in spite of the progress made in both anesthesiology and postoperative care. In the immediate postoperative period, weaning from mechanical ventilation is one of the most dangerous phases of anesthesia (84). We discuss the importance of weaning procedures, in particular, in patients with a high risk of pulmonary complications.