Physiology Regarding Apnoeic Oxygenation During Nasal Cannula Therapy at Different Flow Rates (PHARAO)

Insel Gruppe AG, University Hospital Bern

Status: Completed

Conditions: Apnoeic Oxygenation

Treatments: Drug: Oxygen 10 l/min; Procedure: Jaw thrust; Drug: Oxygen 70l/min; Drug: Oxygen 2l/min; Procedure: Videolaryngoscopy; Drug: oxygen 0.25l/min

Study type: Interventional

Funder types: Other

Identifiers

NCT03478774

2018-00293

Details and patient eligibility

About

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.

Full 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.

Enrollment: 125 patients

Sex: All

Ages: 18+ years old

Volunteers: No Healthy Volunteers

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

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Single Group Assignment

Masking: Single Blind

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125 participants in 5 patient groups

Control

Active Comparator group

Description:

These patients will receive HFNCT with oxygen 70l/min after induction of general anesthesia. Throughout the entire measurement period of 15 or 30 minutes, continuous videolaryngoscopy will be performed.

Treatment:

Procedure: Videolaryngoscopy

Drug: Oxygen 70l/min

High flow

Experimental group

Description:

These patients will receive HFNCT with oxygen 70l/min after induction of general anesthesia. Throughout the entire measurement period of 15 or 30 minutes, jaw thrust will be performed.

Treatment:

Procedure: Jaw thrust

Drug: Oxygen 70l/min

medium flow

Experimental group

Description:

These patients will receive oxygen 10l/min after induction of general anesthesia. Throughout the entire measurement period of 15 or 30 minutes, jaw thrust will be performed.

Treatment:

Procedure: Jaw thrust

Drug: Oxygen 10 l/min

low flow

Experimental group

Description:

These patients will receive oxygen 2l/min after induction of general anesthesia. Throughout the entire measurement period of 15 or 30 minutes, jaw thrust will be performed.

Treatment:

Procedure: Jaw thrust

Drug: Oxygen 2l/min

minimal flow

Experimental group

Description:

These patients will receive a standard tracheal tubes after induction of general anesthesia, with 100% Oxygen and Minimum-flow 0.25l/min. The measurement period is 15 or 30 minutes.

Treatment:

Drug: oxygen 0.25l/min