The influence of different patient positions during rapid induction with severe regurgitation on the volume of aspirate and time to intubation: a prospective randomised manikin simulation study

Abstract

Background: Aspiration is a main contributor to morbidity and mortality in anaesthesia. The ideal patient positioning for rapid sequence induction remains controversial. A head-down tilt and full cervical spine extension (Sellick) might prevent aspiration but at the same time compromise airway management. We aimed to determine the influence of three different positions during induction of general anaesthesia on the volume of aspirate and on participants' airway management.

Methods: Eighty-four anaesthetic trainees and consultants participated in a prospective randomised simulation study. Anaesthesia was induced in reverse Trendelenburg position (+ 15°) in a manikin capable of dynamic fluid regurgitation. Participants were randomised to change to Trendelenburg position (- 15°) a) as soon as regurgitation was noticed, b) as soon as 'patient' had been anaesthetised, and c) as soon as 'patient' had been anaesthetised and with full cervical spine extension (Sellick). Primary endpoints were the aspirated volume and the time to intubation. Secondary endpoints were ratings of the laryngoscopic view and the intubation situation (0-100 mm).

Results: Combining head-down tilt with Sellick position significantly reduced aspiration (p < 0.005). Median time to intubate was longer in Sellick position (15 s [8-30]) as compared with the head in sniffing position (10 s [8-12.5]; p < 0.05). Participants found laryngoscopy more difficult in Sellick position (39.3 ± 27.9 mm) as compared with the sniffing position (23.1 ± 22.1 mm; p < 0.05). Both head-down tilt intubation situations were considered equally difficult: 34.8 ± 24.6 mm (Sniffing) vs. 44.2 ± 23.1 mm (Sellick; p = n.s).

Conclusions: In a simulated setting, using a manikin-based simulator capable of fluid regurgitation, a - 15° head-down tilt with Sellick position reduced the amount of aspirated fluid but increased the difficulty in visualising the vocal cords and prolonged the time taken to intubate. Assessing the airway management in the identical position in healthy patients without risk of aspiration might be a promising next step to take.

Keywords: Airway management; Aspiration; Patient safety; Rapid sequence induction; Simulation.

Fig. 1

CONSORT flow chart of recruitment, randomisation, and analysis

Fig. 2

The three positions of the manikin used: (a) Reverse Trendelenburg position (+ 15°) and head supported by a pillow (‘sniffing position’); (b) Trendelenburg position (− 15°) and ‘sniffing position’; (c) Trendelenburg position (− 15°) and full cervical spine extension (‘Sellick’). Sellick position was determined by tilting the head rest until the head started to suspend in mid-air

Fig. 3

Setup of the manikin: (a) The tracheal tree was modified by inserting two detachable reservoirs that collected the aspirated fluid while leaving ventilation unchanged. The oesophagus was connected to the pneumatically driven liquid reservoir with a flexible hose; (b) Operational manikin. During simulations, the pneumatic system and liquid reservoir were hidden from the participants by surgical drapes

Fig. 4

Intubation position and the resulting time to intubate. Intubation times ranged from 5 to 30 s in the sniffing position as compared to 7 to 120 s in full cervical spine extension