Low-flow apnoeic oxygenation for laryngeal surgery: a prospective observational study.

Laryngeal surgery requires a shared airway and close collaboration between surgeon and anaesthetist in order to optimise operating conditions. Apnoeic oxygenation uses the principle of aventilatory mass flow to maintain oxygenation of pulmonary capillary blood under apnoeic conditions while minimising laryngeal movement. Concerns regarding accumulation of carbon dioxide and resultant acidaemia have limited the use of the technique. We performed a prospective study of low-flow apnoeic oxygenation for patients undergoing microlaryngoscopy under general anaesthesia in order to evaluate the ability of the technique to maintain oxygenation and determine the resultant rate of carbon dioxide accumulation. Sixty-four patients undergoing microlaryngoscopy under general anaesthesia were studied between November 2016 and December 2018. Intra-operative oxygenation was provided via a 10-French oxygen catheter placed into the trachea delivering oxygen at 0.5-1.0 l.min-1 . Data regarding apnoea time, peripheral oxygen saturation and venous blood gas concentrations were recorded. The mean (SD) duration of apnoea was 18.7 (7.2) min. Apnoeic oxygenation allowed successful completion of the surgical procedure in 62/64 patients. Mean (SD) rate of rise of the venous partial pressure of carbon dioxide was 0.15 (0.10) kPa.min-1 . Operating conditions were recorded qualitatively as being adequate in all cases. No adverse effects were reported. Low-flow intra-tracheal apnoeic oxygenation is a simple, effective and inexpensive technique to maintain oxygenation for laryngeal surgery.

Frequency and prognostic significance of p16(INK4A) protein overexpression and transcriptionally active human papillomavirus infection in laryngeal squamous cell carcinoma.

BACKGROUND: Human papillomavirus (HPV) infection is a powerful prognostic biomarker in a subset of head and neck squamous cell carcinomas, specifically oropharyngeal cancers. However, the role of HPV in non-oropharyngeal sites, such as the larynx, remains unconfirmed. METHODS: We evaluated a cohort of 324 laryngeal squamous cell carcinoma (LSCC) patients for the expression of p16(INK4A) (p16) protein by immunohistochemistry (IHC) and for high-risk HPV E6 and E7 mRNA transcripts by RNA in situ hybridisation (ISH). p16 expression and HPV status were correlated with clinicopathological features and outcomes. RESULTS: Of 307 patients assessable for p16 IHC, 20 (6.5%) were p16 positive. Females and node-positive patients were more likely to be p16 positive (P<0.05). There were no other significant clinical or demographic differences between p16-positive and -negative cases. There was no difference in overall survival (OS) between p16-positive and -negative patients with 2-year survival of 79% in each group (HR=0.83, 95% CI 0.36-1.89, P=0.65). There was no statistically significant difference in failure-free survival (FFS) with 2-year FFS of 79% and 66% for p16-positive and -negative patients, respectively (HR=0.60, 95% CI 0.26-1.36, P=0.22). Only seven cases were found to be HPV RNA ISH positive, all of which were p16 IHC positive. There was no statistically significant difference in OS between patients with HPV RNA ISH-positive tumours compared with -negative tumours with 2-year survival of 86% and 71%, respectively (HR=0.76, 95% CI 0.23-2.5, P=0.65). The 2-year FFS was 86% and 59%, respectively (HR=0.62, 95% CI 0.19-2.03, P=0.43). CONCLUSIONS: p16 overexpression is infrequent in LSCC and the proportion of cases with high-risk HPV transcripts is even lower. There are no statistically significant correlations between p16 IHC or HPV RNA ISH status and OS or disease outcomes.

Prevalence and nature of connexin 26 mutations in children with non-syndromic deafness.

OBJECTIVE: To determine (1) the prevalence and nature of connexin 26 mutations in a cohort of Australian children with non-syndromic hearing loss, and (2) the carrier frequency of the common connexin 26 mutation (35delG) in the general population. DESIGN: A cohort, case-finding study. Mutation analysis was performed on DNA extracted from white blood cells, buccal cells, or Guthrie blood spots. SETTING: A hearing loss investigation clinic and a deafness centre in two Australian capital cities, 1 January 1998 to 31 October 2000. PARTICIPANTS: (1) 243 children (age range, 4 weeks to 16 years; median, 4 years), attending hearing loss clinics in Sydney and Melbourne; (2) 1000 blood samples obtained from anonymous Guthrie card blood spots collected in 1984 [corrected] by the Victorian Clinical Genetics Service as part of the newborn screening program. MAIN OUTCOME MEASURES: (1) The prevalence and types of connexin 26 mutations in a cohort of children with prelingual deafness; (2) the carrier frequency of the common connexin 26 mutation, 35delG, in the general population. RESULTS: Connexin 26 mutations were identified and characterised in 52 (21%) of the 243 children; 14 different mutations, including four previously unreported mutations (135S, C53R, T123N and R127C), were identified. The common 35delG mutation was found in 56 of the 104 alleles (ie, 86 of the connexin 26 alleles in which a mutation was positively identified). The mutations V371 and M34T were also relatively common. The carrier frequency of connexin 26 mutations and of the common 35delG connexin 26 mutation in the Victorian population was estimated to be 1 in 54 and 1 in 100, respectively. CONCLUSIONS: Mutations in the connexin 26 gene (especially the 35delG mutation) are a common cause of prelingual hearing loss in Australia.