SummaryA high-quality ultrasound system (Dyasonics Prisma) was used to study the effect of laryngeal mask airway insertion and cuff inflation on the position and relations of the internal jugular vein in eight healthy young patients undergoing elective surgery. On insertion of the laryngeal mask, with the cuff pre-inflated with 10 ml of air, some minor movement was discernible in the larynx. Neither the larynx nor surrounding structures changed significantly in position. However, on full inflation of the laryngeal mask cuff there was a more noticeable movement of the larynx, which visibly distended in an anterior direction. The mean anterior displacement was 0.8 cm (range 0.6-1.1 cm). There was no significant lateral displacement of the carotid artery or internal jugular vein and there was no significant compression of these structures. We conclude that in the presence of a laryngeal mask airway fixed landmarks such as the sternal notch and angle of the jaw should be used to identify the likely position of the internal jugular vein. Difficulty in cannulation may be experienced if the mobile laryngeal structures are used as landmarks. Since the introduction of the laryngeal mask airway (LMA) into wide clinical practice, there has been a great expansion in its clinical applications. In addition to the routine management of the airway of the anaesthetised patient, its use has been suggested in the management of the difficult airway and during cardiopulmonary resuscitation by medical and nonmedical staff [1, 2]. It has also been used during anaesthesia for coronary artery bypass grafting [3]. Anecdotal experience suggests that the insertion of the LMA and inflation of its cuff can subsequently result in difficulty in placement of a cannula into the internal jugular vein.The position of the LMA in relation to the structures of the larynx has been studied radiologically [4]. When the cuff is inflated the thyroid, arytenoid and cricoid cartilages move anteriorly and the tissues overlying the larynx bulge slightly. Cricoid pressure may be impeded by the presence of a laryngeal mask [5] but there is no information on the effect of LMA insertion on the position or patency of either the internal jugular vein or carotid artery. The pressure exerted by the cuff of the LMA can be in the region of 80-110 mmHg [6], which would be sufficient to compress or distort the vein. If this is the case, information about the effect of LMA insertion on the position of the internal jugular vein would be invaluable in cases where its cannulation is contemplated and may reduce the incidence of complications.We therefore decided to study the effect of LMA insertion and cuff inflation on the position of the internal jugular vein using a high-quality ultrasound system (Diasonics Prisma). MethodsHaving obtained written informed consent and local ethics committee approval, we recruited eight patients undergoing elective surgery. These patients were all female, of ASA grade 1 or 2 and aged between 18 and 40 years. All patients had normal anatomy ...
Patients presenting for elective anaesthesia and surgery may be suffering with, or recovering from, a recent upper respiratory tract infection (URTI). It is a frequent clinical problem as to whether to postpone surgery in such patients as they may be more likely to suffer adverse respiratory events related to administration of general anaesthesia. Using dilute ammonia vapour as a chemical stimulus, we measured upper airway reactivity in 11 healthy volunteers (six males), mean age 39.8 (range 30-58) yr, who had symptoms of an URTI. Volunteers were recruited 24-72 h after symptoms first began, and followed-up at regular intervals for the next 8 weeks. Measurements of upper airway reactivity were made on the following days (+/- 24h) after commencement of URTI symptoms: 3, 6, 9, 15, 20 and 27. Additional measurements were obtained 56 days after symptoms first began, and these were regarded as baseline measurements. Upper airway reactivity was increased on days 3, 6 and 9 compared with baseline measurements (P < 0.01, Wilcoxon). There was no significant change in airway reactivity from day 15 onwards, by which time 10 of the 11 subjects were completely devoid of symptoms. All subjects were asymptomatic by day 20 and remained so until the study ended on day 56. We conclude that upper airway reactivity was increased during the acute phase of an URTI, and that this appeared to be related to the presence of symptoms.
SummaryWe have studied changes in upper airway re¯ex sensitivity following general anaesthesia using dilute ammonia vapour as a chemical stimulant in 16 patients undergoing elective laparoscopic gynaecological surgery. We measured the threshold concentration of ammonia vapour required to elicit a transient reduction of inspiratory¯ow caused by glottic closure, de®ned as a glottic stop. Measurements of upper airway re¯ex sensitivity and auditory reaction time were obtained before surgery, and at 60 and 120 min after recovery. Auditory reaction time was depressed signi®cantly at 60 min but was similar to baseline values 120 min after recovery. Upper airway re¯ex sensitivity remained signi®cantly reduced at 60 and 120 min despite the return of auditory reaction time to normal. The lack of correlation between upper airway re¯ex sensitivity and auditory reaction time suggests that central nervous system depression alone does not explain the delayed recovery in airway reactivity.
Upper airway reactivity was measured in 13 patients with obstructive sleep apnoea (OSA), using transient reflex laryngeal closure in response to dilute inhaled ammonia vapour. Upper airway reactivity was measured before and after 3 months of treatment with nasal continuous positive airway pressure (CPAP). Upper airway reactivity decreased significantly after treatment with nasal CPAP to values which were similar to those seen in normal subjects. We hypothesise that patients with OSA have increased upper airway reactivity, secondary to inflammation of the epithelial lining of the upper airway following the repeated injury of nocturnal airway obstruction, allowing the facilitated passage of inhaled irritants to the subepithelial receptors. Treatment of OSA with nasal CPAP may reverse these changes, although in the absence of a control group, these findings are provisional.
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