B.S. von Ungern-Sternberg

Impact of spinal anaesthesia and obesity on maternal respiratory function during elective Caesarean section

Spinal anaesthesia for Caesarean section has gained widespread acceptance. We assessed the impact of spinal anaesthesia and body mass index (BMI) on spirometric performance. In this prospective study, we consecutively assessed 71 consenting parturients receiving spinal anaesthesia with hyperbaric bupivacaine and fentanyl for elective Caesarean section. We performed spirometry during the antepartum visit (baseline), immediately after spinal anaesthesia, 10–20 min, 1 h, 2 h after the operation, and after mobilisation (3 h). Baseline values were within normal ranges. There was a significant decrease in all spirometric parameters after effective spinal anaesthesia that persisted throughout the study period. The decrease in respiratory function was significantly greater in obese (BMI > 30 kg.m−2) than in normal‐weight parturients (BMI < 25 kg.m−2), e.g. median (IQR) vital capacity directly after spinal anaesthesia; −24 (−16 to −31)% vs. −11 (−6 to −16)%, p < 0.001 and recovery was significantly slower. We conclude that both spinal anaesthesia and obesity significantly impair respiratory function in parturients.

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.

The impact of head position on the cuff and tube tip position of preformed oral tracheal tubes in young children

Head and neck movements affect both the length of the trachea and the position of tracheal tubes. This is of relevance when using cuffed tubes because changes in the position of the tube tip may not be equal to changes in the position of the cuff. The aim of the study was to assess the impact of head and neck movement on the position of the tube tip and the cuff of newly designed, oral preformed tracheal tubes in children. The tracheas of 128 children aged 1–8 years were intubated with preformed oral tubes. The distances ‘carina‐to‐tracheal tube tip’ and ‘vocal cords‐to‐tube tip’ were measured endoscopically. These measurements were performed with the head and neck in a functional neutral position (110°), during neck flexion (80°) and neck extension (130°). Tracheal length was dependent on head and neck position: neck extension elongated the trachea (p < 0.0001), and neck flexion shortened the trachea (p < 0.0001). Neck flexion moved the tube inward and resulted in endobronchial displacement in two patients. Neck extension moved the tube outwards. While no cuff was positioned between the vocal cords, cuff movement to the cricoid area occurred frequently. Complex interactions during head and neck movement along with the fixed insertion depth of preformed tubes often cause inadvertent malpositioning of the tube tip and cuff. Further changes to tube and cuff lengths might improve the safety of oral preformed tubes in children.

The effect of epidural analgesia in labour on maternal respiratory function

Lumbar epidural analgesia during labour has gained widespread acceptance. The impact of epidural analgesia based on mixtures of low‐dose local anaesthetic solutions and lipophilic opioids on most clinically relevant obstetric outcomes is minimal. Since the pregnant state per se is associated with important alterations in respiration, we assessed whether a subtle degree of motor blockade brought about by epidural analgesia might compromise respiratory function as assessed by spirometry. Sixty consenting parturients receiving epidural analgesia were consecutively included in this prospective study. We performed spirometry during the antepartum visit and in labour after effective epidural analgesia was established; at both assessments the women were pain‐free. Values were within normal ranges but increased significantly after effective epidural analgesia; median (IQR [range]) increase for vital capacity 7.4 (3.0–13 [−12–27])% (p < 0.001); forced vital capacity 4.4 (1.7–9.8 [−13–26])% (p < 0.001); forced expiratory volume in 1 s 5.5 (1.7–8.6 [−14–28])% (p < 0.001); and peak expiratory flow rate 2.3 (−1.6–5.8 [−18–16])% (p = 0.01)). We conclude that epidural analgesia for labour significantly improved respiratory function.

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children

Caudal block results in a motor blockade that can reduce abdominal wall tension. This could interact with the balance between chest wall and lung recoil pressure and tension of the diaphragm, which determines the static resting volume of the lung. On this rationale, we hypothesised that caudal block causes an increase in functional residual capacity and ventilation distribution in anaesthetised children. Fifty‐two healthy children (15–30 kg, 3–8 years of age) undergoing elective surgery with general anaesthesia and caudal block were studied and randomly allocated to two groups: caudal block or control. Following induction of anaesthesia, the first measurement was obtained in the supine position (baseline). All children were then turned to the left lateral position and patients in the caudal block group received a caudal block with bupivacaine. No intervention took place in the control group. After 15 min in the supine position, the second assessment was performed. Functional residual capacity and parameters of ventilation distribution were calculated by a blinded reviewer. Functional residual capacity was similar at baseline in both groups. In the caudal block group, the capacity increased significantly (p < 0.0001) following caudal block, while in the control group, it remained unchanged. In both groups, parameters of ventilation distribution were consistent with the changes in functional residual capacity. Caudal block resulted in a significant increase in functional residual capacity and improvement in ventilation homogeneity in comparison with the control group. This indicates that caudal block might have a beneficial effect on gas exchange in anaesthetised, spontaneously breathing preschool‐aged children with healthy lungs.

Jaw thrust can deteriorate upper airway patency

Upper airway obstruction is a frequent problem in spontaneously breathing children undergoing anesthesia or sedation procedures. Failure to maintain a patent airway can rapidly result in severe hypoxemia, bradycardia, or asystole, as the oxygen demand of children is high and oxygen reserve is low.

Impact of Trendelenburg positioning on functional residual capacity and ventilation homogeneity in anaesthetised children

Trendelenburg positioning, a head‐down tilt, is routinely used in anaesthesia when inserting a central venous catheter to increase the calibre of the jugular or subclavian veins and to prevent an air embolism. We investigated the impact of Trendelenburg positioning on functional residual capacity and ventilation homogeneity as well as the potential reversibility of these changes by repositioning and/or a recruitment manoeuvre in children with congenital heart disease.

Value of eosinophil cationic protein and tryptase levels in bronchoalveolar lavage fluid for predicting lung function impairment in anaesthetised, asthmatic children

Bronchial hyperactivity, a key feature of active asthma in children, is a risk factor for respiratory adverse events in the peri‐operative period. The presence of activated eosinophils in the lungs and mast cell degranulation can contribute to bronchial hyperreactivity. Eosinophil cationic protein is released by activated eosinophils and tryptase reflects mast cell degranulation. This study focused on the relationship of respiratory mechanics, eosinophil cationic protein and tryptase levels in bronchoalveolar lavage fluid in asthmatic and healthy children under general anaesthesia. We measured eosinophil cationic protein and tryptase levels in bronchoalveolar lavage fluid from 21 asthmatic and 21 healthy children following induction of general anaesthesia. Respiratory system resistance and dynamic compliance were measured during mechanical ventilation. Eosinophil cationic protein was more common in bronchoalveolar lavage fluid from asthmatics (12/21) than from controls (4/21, p = 0.01) and was present at higher levels (p = 0.002). Tryptase was also more common in the asthmatics (8/21 vs 1/21, p = 0.01). Respiratory resistance was significantly higher in asthmatic children with detectable eosinophil cationic protein levels than in those with undetectable eosinophil cationic protein levels (p = 0.019). Furthermore, 50% of the asthmatics with detectable eosinophil cationic protein exhibited bronchospasm after sampling their bronchoalveolar lavage fluid. These findings suggested that high levels of eosinophil cationic protein in the bronchoalveolar lavage fluid are associated with irritable airways, presumably secondary to airway inflammation, and this might be a useful marker for respiratory adverse events in the peri‐operative period.

Cuffed vs. uncuffed tracheal tubes in children: a randomised controlled trial comparing leak, tidal volume and complications

Cuffed tracheal tubes are increasingly used in paediatric anaesthetic practice. This study compared tidal volume and leakage around cuffed and uncuffed tracheal tubes in children who required standardised mechanical ventilation of their lungs in the operating theatre. Children (0–16 years) undergoing elective surgery requiring tracheal intubation were randomly assigned to receive either a cuffed or an uncuffed tracheal tube. Assessments were made at five different time‐points: during volume‐controlled ventilation 6 ml.kg−1, PEEP 5 cmH2O and during pressure‐controlled ventilation 10 cmH2O / PEEP 5 cmH2O. The pressure‐controlled ventilation measurement time‐points were: just before a standardised recruitment manoeuvre; just after recruitment manoeuvre; 10 min; and 30 min after the recruitment manoeuvre. Problems and complications were recorded. During volume‐controlled ventilation, leakage was significantly less with cuffed tracheal tubes than with uncuffed tracheal tubes; in ml.kg−1, median (IQR [range]) 0.20 (0.13–0.39 [0.04–0.60]) vs. 0.82 (0.58–1.38 [0.24–4.85]), respectively, p < 0.001. With pressure‐controlled ventilation, leakage was less with cuffed tracheal tubes and stayed unchanged over a 30‐min period, whereas with uncuffed tracheal tubes, leakage was higher and increased further over the 30‐min period. Tidal volumes were higher in the cuffed group and increased over time, but in the uncuffed group were lower and decreased over time. Both groups showed an increase in tidal volumes following recruitment manoeuvres. There were more short‐term complications with uncuffed tracheal tubes, but no major complications were recorded in either group at long‐term follow‐up. With standardised ventilator settings, cuffed tracheal tubes produced better ventilation characteristics compared with uncuffed tracheal tubes during general anaesthesia for routine elective surgery.

The efficacy of GlideScope ® videolaryngoscopy compared with direct laryngoscopy in children who are difficult to intubate: An analysis from the paediatric difficult intubation registry

Background We analysed data from the Paediatric Difficult Intubation Registry examining the use of direct laryngoscopy and GlideScope® videolaryngoscopy. Methods Data collected by a multicentre, paediatric difficult intubation registry from 1295 patients were analysed. Rates of success and complications between direct laryngoscopy and GlideScope videolaryngoscopy were analysed. Results Initial (464/877 = 53% vs 33/828 = 4%, Z-test = 22.2, P < 0.001) and eventual (720/877 = 82% vs. 174/828 = 21%, Z-test = 25.2, P < 0.001) success rates for GlideScope were significantly higher than direct laryngoscopy. Children weighing <10 kg had lower success rates with the GlideScope than the group as a whole. There were no differences in complication rates per attempt between direct laryngoscopy and GlideScope. The direct laryngoscopy group had more complications associated with the greater number of attempts needed to intubate. There were no increased risks of hypoxia or trauma with GlideScope use. Each additional attempt at intubation with either device resulted in a two-fold increase in complications (odds ratio: 2.0, 95% confidence interval: 1.5-2.5, P < 0.001). Conclusions During difficult tracheal intubation in children, direct laryngoscopy is an overly used technique with a low chance of success. GlideScope use was associated with a higher chance of success with no increased risk of complications. GlideScope use in children with difficult tracheal intubation has a lower success rate than in adults with difficult tracheal intubation. Children weighing less than 10 kilograms had lower success rates with either device. Attempts should be minimized with either device to decrease complications.