[Effect of positive end-expiratory pressure on the cross-sectional area of the internal jugular vein and anatomic relationship between the internal jugular vein and the carotid artery in general anaesthesia of laryngeal mask airway].

Objective: To investigate the effect of positive end-expiratory pressure(PEEP) on the cross-sectional area (CSA) of the internal jugular vein (IJV) and anatomic relationship between the IJV and the common carotid artery (CCA) in general anaesthesia of laryngeal mask airway(LMA). Methods: Sixty American Society of Anesthesiologists (ASA) Ⅰ or Ⅱ grade patients undergoing elective operation received general anaesthesia using LMA from May to November 2017, aged 20-65, were included in this study and randomly divided into 4 groups: group P0 (PEEP: 0 cmH(2)O), group P5 (PEEP: 5 cmH(2)O), group P10 (PEEP: 10 cmH(2)O), group P15 (PEEP: 15 cmH(2)O). Following the induction of anesthesia, LMA was inserted, and mechanical ventilation was started while the right cervical vessels was imaged by ultrasonography after applying 4 different PEEPs in random order. Measurements were made after 1 min in each PEEP. The CSA, transverse diameter (TD), anteroposterior diameters (AD) of the IJV and the diameter, overlap distance and overlap index of CCA was measured. The arterial blood pressure, heart rate, and vasoactive drugs used were also recorded. Results: The CSA of group P0, P10 and P15 was (1.36±0.55), (1.80±0.54), (2.02±0.58) cm(2). The TD was (1.31±0.33), (1.61±0.49), (1.74±0.53) cm. The AD was (1.12±0.20), (1.33±0.30), (1.46±0.32) cm. Compared to group P0, the CSA, TD and AD of IJV in group P10 and P15 were significantly increased (P0/P10: t =7.81, 3.81, 4.30, all P <0.01; P0/P15: t =11.68, 5.40, 6.96, all P <0.01). There was no significant difference in the AD and TD of IJV between group P10 and P15 (all P >0.05), while the CSA of group P15 was bigger than that of group P10 ( t =2.17, P <0.05). The overlap distance of group P0, P10 and P15 was (0.51±0.12), (0.62±0.16), (0.66±0.15) cm. The overlap index was (76.80±20.03)%, (91.10±26.13)%, (96.21±25.36)%. Compared to group P0, the overlap distance and overlap index in group P10 and P15 were significantly increased (P0/P10: t =4.49, 3.41, both P <0.01; P0/P15: t =5.91, 4.63, both P <0.01). There was no significant changes in the overlap distance and overlap index between group P10 and P15 (all P >0.05). The MAP of group P15 was lower than that of group P10 [(73.35±9.73 )vs (67.58±12.58) mmHg, t =2.745, P <0.05]. No patients were given atropine or norepinephrine. Conclusions: The application of PEEP effectively increases the CSA of IJV in general anaesthesia of LMA. At the same time, it also lead to higher overlap index between the IJV and CCA.Ten cmH(2)O PEEP provides the best balance between the increase of CSA and the stability of haemodynamics.