Alveolar target ventilation and dead space in children under anaesthesia: The proventiped cohort study.

INTRODUCTION: Ventilator settings in children under anaesthesia remain difficult because of the changes in the physiology and the high dead space. OBJECTIVE: To determine the alveolar minute-volume to sustain normocapnia in children under mechanical ventilation. DESIGN: A prospective observational study. SETTINGS: This study was performed between May and October 2019 in a tertiary care children's hospital. PATIENTS: Children between 2 months and 12 years, weighing between 5 and 40 kg, admitted for general anaesthesia. INTERVENTION: Volumetric capnography was used to estimate the alveolar and dead space volume (Vd). MAIN OUTCOME MEASURES: Total and alveolar minute ventilation in (ml kg -1  min -1 ) over 100 breaths. RESULTS: Sixty patients were included comprising 20 per group: 5 to 10 kg (group 1), 10 to 20 kg (group 2), 20 to 40 kg (group 3). Seven patients were excluded for aberrant capnographic curves. After normalisation to weight, the median [IQR] tidal volume per kilogram was similar between the three groups: 6.5 ml kg -1 [6.0 to 7.5 ml kg -1 ], 6.4  ml kg -1 [5.7 to 7.3  ml kg -1 ], 6.4  ml kg -1 [5.3 to 6.8  ml kg -1 ]; P  = 0.3. Total Vd (in ml kg -1 ) was negatively correlated to weight ( r  = -0.62, 95% confidence interval -0.41 to -0.76, P  < 0.001). The total normalised minute ventilation (ml kg -1  min -1 ) to obtain normocapnia was higher in group 1 than in group 2 and in group 3; 203  ml kg -1  min -1 [175 to 219 ml kg -1  min -1 ], 150  ml kg -1  min -1 [139 to 181  ml kg -1  min -1 ] and 128  ml kg -1  min -1 [107 to 157  ml kg -1  min -1 ]; P  < 0.001 (mean ± SD), but (mean ± SD) alveolar minute ventilation was similar between the three groups; 68 ±â€Š21  ml kg -1  min -1 . CONCLUSION: Total dead space volume (including apparatus dead space) represents a major component of tidal volume in children less than 30 kg, when using large heat and moisture exchanger filters. The total minute ventilation necessary to achieve normocapnia decreased with increasing weight, while the alveolar minute ventilation remained constant. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT03901599.

Effective dose of ephedrine for treatment of hypotension after induction of general anaesthesia in neonates and infants less than 6 months of age: a multicentre randomised, controlled, open label, dose escalation trial.

BACKGROUND: The recommended dose of ephedrine in adults (0.1 mg kg-1) frequently fails to treat hypotension after induction of general anaesthesia in neonates and infants less than 6 months of age. The aim of this study was to determine the optimal dose of ephedrine in this population for the treatment of hypotension after induction of general anaesthesia with sevoflurane. METHODS: We conducted a multicentre, prospective, randomised, open-label, controlled, dose-escalation trial. Subjects were randomised if presenting a >20% change from baseline in MAP. Six cohorts of 20 subjects each were enrolled. Ten subjects in the first cohort received 0.1 mg kg-1 i. v. (reference dose). For each subsequent cohort, 10 subjects were assigned to the next higher dose (consecutively 0.6, 0.8, 1, 1.2, and 1.4 mg kg-1 i. v.), and the other subjects were assigned to one or more doses already investigated in previous cohorts. The primary outcome was the return of MAP to >80% of baseline at least once within 10 min after ephedrine administration. RESULTS: A total of 119 infants (25% females), with a mean age (standard deviation) of 2.7 (1.3) months, received their allocated dose of ephedrine. The optimal dose of ephedrine was 1.2 mg kg-1, with a percentage of success of 65.5% (95% confidence interval, 35.6-86.4). The doses of ephedrine investigated did not induce adverse events. CONCLUSIONS: Doses of ephedrine much higher (∼10-fold) than those used in adults are necessary in neonates and infants for the treatment of hypotension after induction of general anaesthesia with sevoflurane. CLINICAL TRIAL REGISTRATION: NCT02384876.

Lost Venous Access Guidewire Identified by Its Late Cervical Protrusion: Case Report.

We report a pediatric patient who underwent a central venous catheter (CVC) insertion and presented with a sudden protrusion of a guidewire from the neck 26 months later. The guidewire was extracted via femoral venotomy. A 5-cm portion of the guidewire adhering to the superior vena cava wall was left in place. We recommend always using a CVC checklist, inspecting the guidewire before and after insertion, and carefully examining the postinsertion radiographs. This checklist should be mandatory with every CVC insertion, including the perioperative period.

Pre-operative fasting in children: A guideline from the European Society of Anaesthesiology and Intensive Care.

Current paediatric anaesthetic fasting guidelines have recommended conservative fasting regimes for many years and have not altered much in the last decades. Recent publications have employed more liberal fasting regimes with no evidence of increased aspiration or regurgitation rates. In this first solely paediatric European Society of Anaesthesiology and Intensive Care (ESAIC) pre-operative fasting guideline, we aim to present aggregated and evidence-based summary recommendations to assist clinicians, healthcare providers, patients and parents. We identified six main topics for the literature search: studies comparing liberal with conservative regimens; impact of food composition; impact of comorbidity; the use of gastric ultrasound as a clinical tool; validation of gastric ultrasound for gastric content and gastric emptying studies; and early postoperative feeding. The literature search was performed by a professional librarian in collaboration with the ESAIC task force. Recommendations for reducing clear fluid fasting to 1 h, reducing breast milk fasting to 3 h, and allowing early postoperative feeding were the main results, with GRADE 1C or 1B evidence. The available evidence suggests that gastric ultrasound may be useful for clinical decision-making, and that allowing a 'light breakfast' may be well tolerated if the intake is well controlled. More research is needed in these areas as well as evaluation of how specific patient or treatment-related factors influence gastric emptying.

Ultrasound assessment of the prevalence of increased gastric contents and volume in elective pediatric patients: A prospective cohort study.

BACKGROUND: Though pulmonary aspiration of gastric contents occurs mainly in the setting of emergency surgery, it may also occur in children scheduled for elective surgery without any obvious clinical risk factor. Increased gastric content volume is one the predisposing factors for pulmonary aspiration that could affect such children and may be identified using ultrasound examination of the gastric antrum. AIMS: We aimed to assess the prevalence of "at-risk stomach" defined by ultrasound visualization of any solid content in the antrum and/or by calculated gastric fluid volume > 1.25 mL/kg, in children scheduled for elective surgery. METHODS: Children scheduled for elective surgery were consecutively included into this prospective cohort study. Preoperative ultrasound examination of the antrum was performed in both the supine and the right lateral decubitus positions. Gastric fluid content was assessed using a 0-2 qualitative grading scale. The antral cross-sectional area was also measured in both the supine and the right lateral decubitus positions, allowing the calculation of the gastric fluid volume according to a formula previously described. RESULTS: We analyzed 200 elective children. Median duration of fasting was 4 hours for liquids and >13 hours for solids. None of the children included in this study had evidence of solid content. Six (3%) children had a Grade 2 antrum (fluid content seen in both the supine and the right lateral decubitus positions). Two children had a gastric fluid volume >1.25 mL/kg. The prevalence of "at-risk stomach" was 1% (95% confidence interval: 0.2%-3.9%). CONCLUSION: According to our results, only 1% of elective children had potentially increased risk for pulmonary aspiration. Further studies should be performed in order to define the target population of elective children for which ultrasound assessment of gastric content should be performed prior to general anesthesia.

Suprasternal notch echocardiography: a potential alternative for the measurement of respiratory variation in aortic blood flow peak velocity in mechanically ventilated children.

We conducted a prospective, observational study to investigate the relationship between the respiratory variation in aortic blood flow peak velocity (ΔVPeak) measured by echocardiography in the proximal ascending aorta from the suprasternal notch window and the ΔVPeak measured at the level of the aortic annulus from the classical apical five-chamber view. We studied children aged from 1 to 10 years referred for surgery under general anesthesia with positive pressure ventilation, after induction of general anesthesia. Twenty-two children (mean age = 5 ± 3 years) were recruited. There was a significant relationship between the ΔVPeak recorded via the suprasternal notch view and the ΔVPeak recorded via the apical five-chamber view (r = 0.62 [95% confidence interval 0.25-0.84], P = 0.003). The ΔVPeak measured using the suprasternal notch route could be considered to predict fluid responsiveness in children under mechanical ventilation, notably when the access to the chest wall is limited during surgery.

Ultrasound-guided subclavian vein cannulation in infants: supraclavicular approach.

BACKGROUND: Ultrasound (US) guidance techniques are reported to be safe for internal jugular vein catheterization, although anatomic conditions are not favorable for this approach in infants. The subclavian vein (SCV) seems to be a better site for long-term central venous catheterization in children, with a supraclavicular approach to avoid compression of the central venous catheter between the clavicle and the first rib ('pinch-off' syndrome). We describe a new US-guided approach for supraclavicular SCV cannulation in infants. METHODS: The principle of this technique is to place the US probe at the supraclavicular level to obtain a longitudinal view of the SCV, and to gain access to the vein with a total ultrasonic control (in-plane puncture) via a supraclavicular approach known since 1965, but rarely used in blind puncture. The results of 37 US-guided SCV cannulations in infants weighing <10 kg are reported. RESULTS: Forty-two infants were enrolled in this observational study, and five infants with bad visualization of SCV were excluded. The procedure duration was <5 min in all cases except one. The success rate at the first attempt was 81% and 100% after two attempts. No major complications were reported. CONCLUSIONS: This US-guided supraclavicular approach for SCV puncture is a new possibility for central venous catheterization in small infants, offering all the advantages of SCV cannulation without the risk of 'pinch-off' syndrome. This technique seems valuable for children and infants and quite easy to apply for physicians trained to US guidance punctures.

Chronobiology and anaesthesia.

PURPOSE OF REVIEW: It has been shown that biological rhythms influence the pharmacology and effects of anaesthetic agents such as local anaesthetics, hypnotics and muscle relaxants. This review discusses the latest findings and their consequences for anaesthesiological practice. RECENTS FINDINGS: Opioids and new local anaesthetics exhibit circadian changes when they are injected into spinal or epidural spaces for labour pain analgesia. Other studies have demonstrated that propofol and ketamine have maximal duration of action when they are injected during a period of rest in animals (at night in humans). It has been also shown that propofol can perturb the central circadian pacemaker and so cause a phase-shifted advance in effect on activity in rats. SUMMARY: Although studies are lacking for most newer anaesthetic agents used in humans, recent findings emphasize once again that chronobiology should be considered in studies of anaesthetic drugs. Circadian rhythms should be considered in pharmacokinetic and pharmacodynamic analyses so that proper research protocols can be designed. The implications of chronobiology for the practice of clinical anaesthesia are probably of lesser importance because of the use of patient-controlled devices for pain management, monitoring of muscle paralysis and depth of anaesthesia monitors.