Apnoeic Oxygenation
Conditions
Brief summary
This study compares under controlled conditions if different flow rates affect apnoea time after induction of anaesthesia and how CO2 clearance is influenced. Furthermore, this study enables to quantify the effects of increased pCO2 on vital parameters (e.g. blood pressure, cardiac output, cerebral perfusion, etc.) The investigators will enroll patients undergoing elective surgery at the University Hospital of Bern, Switzerland. Once anesthesia has been induced, apnoea will set it. During this period, the investigators will compare different methods of apnoeic oxygenation for a maximum of 15 or 30 minutes. Before discharge, an interview will be conducted, assessing complications and patient satisfaction.
Detailed description
Eligible, consenting adults will be prepared for general anaesthesia in the usual way consisting of ECG, pulse-oximetry, NarcotrendTM, a venous cannula and an arterial line for continuous blood pressure monitoring. They will receive additional monitoring such as transcutaneous measurement of pCO2 and O2, NIRS, and thoracic electrical impedance tomography (EIT, PulmoVista® 500, Draeger, Luebeck, Germany). Normal pre-oxygenation (until etO2 is \> 90% or time \> 3 minutes) will occur. Anaesthesia will be started (= induction) using Propofol and Fentanyl, using NarcotrendTM to measure depth of anaesthesia. All patients will receive a standard dose of neuromuscular blockage to facilitate airway management and total intravenous anaesthesia will be installed. Using the train of four measurement (TOF) full neuromuscular blockage with Rocuronium will be confirmed every 30 seconds. If necessary, additional dosage of neuromuscular blockage will be administered. After administration of Rocuronium, possibility of mask ventilation will be confirmed and the sealed envelope with the randomization will then be opened. As a study intervention, the assigned method (HFNCT 70 l/min with either jaw thrust or laryngoscopy, or 10 l/min or 2l/min with the standard nasal canula, or 0.25l/min delivery of oxgen via a tracheal tube) will be installed and mask ventilation discontinued starting the apnoea period. Nasopharyngoscopy (EF-N slim, Acutronic, Hirzel, Switzerland) will confirm upper airway patency. Blood gas analysis will be conducted: baseline awake, start of apnoea, first minute after apnoea start, and every 2 minutes thereafter with a maximum of 75ml 150 ml in total. Other measurements (ECG, pulse-oximetry, blood pressure, NIRS, thoracic EIT, NarcotrendTM, PtcO2, PtcCO2) will be measured continuously over the study period The study intervention will end when one of the following criteria (study end-points) is met: SpO2 \<92%, PtcCO2 \> 100 mmHg or time \> 30 minutes. When any of the end points is reached, patient-centred standard anaesthesia care will be continued, as planned for the case. A post-operative interview will be conducted before discharge to evaluate injuries during airway management (bleeding, sore throat, hoarseness), pain, postoperative nausea and vomiting.
Interventions
DRUGOxygen 70l/min
HFNCT will be provided using OptiFlow by Fisher&Paykel.
DRUGOxygen 10 l/min
Medium flow will be applied with a humidifier (Hudson RCI) and a standard nasal cannula.
DRUGOxygen 2l/min
Low flow will be applied with a humidifier (Hudson RCI) and a standard nasal cannula.
PROCEDUREJaw thrust
Continuous
PROCEDUREVideolaryngoscopy
Continuous
DRUGoxygen 0.25l/min
0.25l/min of oxygen via an endotracheal tube
Sponsors
Insel Gruppe AG, University Hospital Bern
Study design
Allocation
RANDOMIZED
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
SINGLE (Subject)
Masking description
Patients will be blinded as they receive general anesthesia. Care providers cannot be blinded, due to obvious differences in set-up of the different interventions.
Intervention model description
single centre, prospective, randomized-controlled trial
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* \> 18 years * Written informed consent * Undergoing elective surgery * Requiring general anesthesia
Exclusion criteria
* Any Indication for fibre optic intubation * Expected impossible mask ventilation * Known coronary heart disease * Known heart failure, NYHA classification ≥ 2 * Therapy including β-receptor antagonists * Arrhythmias in need of anti-arrhythmic therapy (e.g. implanted cardio defibrillator) * Peripheral occlusive arterial disease, Fontaine ≥ 2b * Known stenosis of the (common or internal) carotid or vertebral arteries * BMI \> 35kg/m2 and BMI \< 16kg/m2 * Hyperkalaemia (K \> 5.5 mmol/l) * Known COPD Gold classification ≥ 2 * Known pulmonary arterial hypertension, systolic \> 35mmHg * Known obstructive sleep apnoea syndrome in need of therapy * High risk of aspiration (requiring rapid sequence induction intubation) * Increased intracranial pressure * Intracranial surgery * Limited knowledge of German language * Absent power of judgement * Anaemia, Hb \< 100 g/l * Pregnancy (pregnancy test in all female patients) * Neuromuscular disorder * Known or suspected cervical spine instability * Nasal obstruction, impossibility of nasal ventilation (both sides patent) * Allergies or contra-indications to one or more of the used anaesthesia agents
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| pCO2 increase in kPa/min | 15 or 30 minutes (maximum apnea time) | pCO2 will be measured transcutaneously throughout the apnea period |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in PaO2 in kPa | During apnea period (until end-point is met or max. 15 or 30 minutes) | Blood gas analyses as well as transcutaneous measurement |
| Change in cardiac output in L/min | During apnea period (until end-point is met or max. 15 or 30 minutes) | Cardiac output will be measured using pulse pressure measurement |
| Change in cerebral perfusion in % | During apnea period (until end-point is met or max. 15 or 30 minutes) | Near infrared spectroscopy will be measured continuously |
| Changes in end-expiratory lung impedance | During apnoea time (until end-point is met or max. 15 or 30 minutes) | To quantify atelectasis during apnoeic oxygenation |
| Change in invasive blood pressure | During apnoea time (until end-point is met or max. 15 or 30 minutes) | Measurement of change due to hypercarbia |
| Lowest Saturation | During apnea period (until end-point is met or max. 15 or 30 minutes) | Lowest SpO2 in % |
| Depth of anaesthesia | During apnoea time (until end-point is met or max. 15 or 30 minutes) | Using Narcotrend-EEG |
| Bilateral brain oxygenation | During apnoea time (until end-point is met or max. 15 or 30 minutes) | Using NIRS |
| Arterial blood gas analyses | At 0, 1, 3, 5, 7, 9, 11, 13 and 15 minutes of apnoea or 0,1,3,5,7,9,13,15,17,19,21,23,25,27,29 and 30 min of apnoea. | pH |
| Postoperative questionnaire | Morning of first postoperative day | Visual analogue scale (VAS) : pain, nausea, vomiting, feeling worried or anxious, feeling sad or depressed, injuries, discomfort, any complications |
| Standard monitoring | During apnoea time (until end-point is met or max. 15 or 30 minutes) | 3 pole ECG |
Countries
Switzerland
Outcome results
None listed