Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

SummaryBackground Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatoryactions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19.Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospitalwith COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients wererandomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once perday by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatmentgroups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment andwere twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants andlocal study staff were not masked to the allocated treatment, but all others involved in the trial were masked to theoutcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treatpopulation. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) wereeligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomlyallocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall,561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days(rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days(rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, nosignificant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilationor death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24).Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or otherprespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restrictedto patients in whom there is a clear antimicrobial indication

Expiratory-modulated laryngeal motoneurons exhibit a hyperpolarization preceding depolarization during superior laryngeal nerve stimulation in the in vivo adult rat

Swallowing requires the sequential activation of tongue, pharyngeal and esophageal muscles to propel the food bolus towards the stomach. Aspiration during swallow is prevented by adduction of the vocal cords during the oropharyngeal phase. Expiratory-modulated laryngeal motoneurons (ELM) exhibit a burst of action potentials during swallows elicited by electrical stimulation of the superior laryngeal nerve (SLN). Here we sought to investigate changes in membrane potential in ELM during superior laryngeal nerve stimulation in the anaesthetised, in vivo adult rat preparation. Intracellular recordings of ELM in the caudal nucleus ambiguus (identified by antidromic activation from the recurrent laryngeal nerve) demonstrated that ELM bursting activity following SLN stimulation is associated with a depolarization that is preceded by a small hyperpolarization. During spontaneous ELM bursts, the preceding hyperpolarization separated the bursting activity from its usual post-inspiratory activity. These findings demonstrate that the in vivo adult rat preparation is suitable for the study of swallow-related activity in laryngeal motoneurons.10 page(s

Recurrent laryngeal nerve activity exhibits a 5-HT-mediated long-term facilitation and enhanced response to hypoxia following acute intermittent hypoxia in rat

A progressive and sustained increase in inspiratory-related motor output ("long-term facilitation") and an augmented ventilatory response to hypoxia occur following acute intermittent hypoxia (AIH). To date, acute plasticity in respiratory motor outputs active in the postinspiratory and expiratory phases has not been studied. The recurrent laryngeal nerve (RLN) innervates laryngeal abductor muscles that widen the glottic aperture during inspiration. Other efferent fibers in the RLN innervate adductor muscles that partially narrow the glottic aperture during postinspiration. The aim of this study was to investigate whether or not AIH elicits a serotonin-mediated long-term facilitation of laryngeal abductor muscles, and if recruitment of adductor muscle activity occurs following AIH. Urethane anesthetized, paralyzed, unilaterally vagotomized, and artificially ventilated adult male Sprague-Dawley rats were subjected to 10 exposures of hypoxia (10% O 2 in N 2, 45 s, separated by 5 min, n = 7). At 60 min post-AIH, phrenic nerve activity and inspiratory RLN activity were elevated (39 ± 11 and 23 ± 6% above baseline, respectively). These responses were abolished by pretreatment with the serotonin-receptor antagonist, methysergide (n = 4). No increase occurred in time control animals (n = 7). Animals that did not exhibit postinspiratory RLN activity at baseline did not show recruitment of this activity post-AIH (n = 6). A repeat hypoxia 60 min after AIH produced a significantly greater peak response in both phrenic and RLN activity, accompanied by a prolonged recovery time that was also prevented by pretreatment with methysergide. We conclude that AIH induces neural plasticity in laryngeal motoneurons, via serotonin-mediated mechanisms similar to that observed in phrenic motoneurons: the so-called "Q-pathway". We also provide evidence that the augmented responsiveness to repeat hypoxia following AIH also involves a serotonergic mechanism.13 page(s

Cholinergic inputs to laryngeal motoneurons functionally identified in vivo in rat : a combined electrophysiological and microscopic study

The intrinsic laryngeal muscles are differentially modulated during respiration as well as other states and behaviors such as hypocapnia and sleep. Previous anatomical and pharmacological studies indicate a role for acetylcholine at the level of the nucleus ambiguus in the modulation of laryngeal motoneuron (LMN) activity. The present study investigated the anatomical nature of cholinergic input to inspiratory- (ILM) and expiratory-modulated (ELM) laryngeal motoneurons in the loose formation of the nucleus ambiguus. Using combined in vivo intracellular recording, dye filling, and immunohistochemistry, we demonstrate that LMNs identified in Sprague–Dawley rat receive several close appositions from vesicular acetylcholine transporter-immunoreactive (VAChT-ir) boutons. ELMs receive a significantly greater number of close appositions (mean ± standard deviation [SD]: 47 ± 11; n = 5) than ILMs (32 ± 9; n = 8; t-test P < 0.05). For both LMN types, more close appositions were observed on the cell soma and proximal dendrites compared to distal dendrites (two-way analysis of variance [ANOVA], P < 0.0001). Using fluorescence confocal microscopy, almost 90% of VAChT-ir close appositions (n = 45 boutons on n = 4 ELMs) were colocalized with the synaptic marker synaptophysin. These results support a strong influence of cholinergic input on LMNs and may have implications in the differential modulation of laryngeal muscle activity.14 page(s

The Brainstem respiratory network

The respiratory system works with the cardiovascular system to supply tissues with oxygen, to remove carbon dioxide, and to maintain a normal acid-base balance (i.e. blood gas homeostasis). The basic breathing rhythm is generated in the ventrolateral medulla in a column of cells that extends in the caudal direction from the caudal pole of the facial motor nucleus (VIIn) to the spino-medullary junction. The breathing networks are also vitally important in a host of other behaviors, such as swallow, cough, emesis, expiration reflex, micturition, defecation, parturition, suckling, locomotion, and vocalization. These networks control the primary muscle of inspiration, the diaphragm, as well as a host of upper airway and abdominal muscles, to accomplish these tasks without compromising blood gas homeostasis. The core respiratory networks are also modulated by many sensory inputs from the periphery as well as modulatory inputs from other brain regions, notably the dorsolateral-pontine and midline-raphé nuclei.11 page(s

Intermittent activation of peripheral renin-angiotensin system (RAS) elicits sympathetic long term facilitation (LTF)

We recently reported that acute intermittent hypoxia (AIH, 10x45s of 10% O₂, 5 min intervals) produces LTF of splanchnic sympathetic nerve activity (sSNA), independent of respiratory LTF (Xing & Pilowsky, 2010, J Physiol, 588:3075). We hypothesised that sympathetic LTF (sLTF) is the result of intermittent activation of RAS, by renal hypoxia caused by AIH-evoked hypotension. We recorded phrenic nerve activity (PNA) and sSNA, in anesthetised (pentobarbitone, 60mg/kg, ip), vagotomised, and ventilated Sprague-Dawley rats. Intermittent bolus injections of angiotensin II (Ang, 10x35pmol in 0.1ml, iv), at the same 5 min intervals as AIH, elicited sLTF (+42.4 ±11.5%, n=5). Intermittent phenylephrine (PE, 10x 25μg in 0.1mL, iv) also produced sLTF (+72.4±21.6%, n=5), possibly via renal vasoconstriction induced renin release. Intermittent sodium nitroprusside induced hypotension (10x50μg in 0.1mL, iv) did not elicit sLTF (+2.4±5.6%, n=5). Infusion of Ang (350pmol in 1mL) or PE (250μg in 1mL) over 10 mins, also did not cause sLTF, indicating that intermittent stimulation of RAS is essential for sLTF to develop. PNA was unchanged in all groups. This data supports the idea that sLTF and respiratory LTF are mediated by separate mechanisms and that intermittent stimulation of peripheral RAS may be sufficient to elicit sLTF. This data may be relevant to sympathetic overactivity in sleep apnea patients. Funded by NH&MRC, ARC.1 page(s

The Generation of post-inspiratory activity in laryngeal motoneurons : a review

Breathing is a vegetative function that is altered during more complex behaviours such as exercise, vocalisation and respiratory protective reflexes. Recent years have seen recognition of the importance of respiratory pattern generation in addition to rhythm generation. Respiratory-modulated cranial motoneurons (laryngeal, pharyngeal, hypoglossal, facial) offer a unique insight into the control of respiration since: (1) they receive rhythmic respiratory inputs but; (2) their respiratory-modulated firing pattern differs to that of phrenic neurons to suit their function, (for example, hypoglossal motoneurons begin firing and thus the tongue depresses before the onset of phrenic nerve discharge and diaphragmatic during inspiration) and; (3) their activity is often altered in parallel with changes in respiration during stereotypical non-respiratory behaviours such as coughing, swallowing and sneeze. Here we review some mechanisms that modulate the respiratory-related activity of laryngeal motoneurons with an emphasis on the generation of post-inspiratory activity.7 page(s

Neuronal mechanisms underlying the laryngeal adductor reflex

Objectives: Electromyographic studies of the laryngeal adductor reflex, glottal closure occurring in response to laryngeal stimulation, have demonstrated an early ipsilateral response (R1) and a late bilateral response (R2). To better define the physiologic properties of these responses, we recorded responses from expiratory laryngeal motoneurons (ELMs) in rats during stimulation of the superior laryngeal nerve (SLN). Methods: Single unit extracellular recordings were obtained from 5 ELMs, identified by their antidromic responses to recurrent laryngeal nerve stimulation and postinspiratory firing pattern, in 4 Sprague-Dawley rats. Results: Unilateral stimulation of the SLN (at 20 Hz) stopped both phrenic nerve inspiratory activity and ELM postinspiratory activity. However, the ELMs displayed robust tonic firing, consisting of non-respiratory burst activity and single action potentials. The single action potentials were identified as short-latency ones (5 to 10 ms) activated by ipsilateral SLN stimulation, with an occurrence rate of 90%, and long-latency ones (20 to 50 ms) activated by bilateral SLN stimulation, with occurrence rates of 47% on the ipsilateral side and 58% on the contralateral side. Conclusions: The R1 response appears to be the result of the short-latency action potentials, orthodromically activated by ipsilateral stimulation of the SLN. The R2 response is likely to be a result of the long-latency action potentials that can be recorded from ELMs on both sides.6 page(s

The physiological significance of postinspiration in the respiratory system

The term postinspiration is commonly used in the scientific literature concerned with neural generation and the control of breathing movements. Because postinspiration belongs functionally to the mechanical act of expiration, the physiological significance of postinspiration as a distinct phase of the breathing cycle is often underappreciated. The present review will give an overview of the physiological significance of postinspiratory motor activity in laryngeal adductor (constrictor) muscles and the crural diaphragm. The functional importance of postinspiratory motor activity is discussed for the eupneic respiratory cycle, and for various protective respiratory reflex mediations (e.g., sneeze, cough, and breath-hold). Also, the implications of recruited postinspiratory activity during nonventilatory behaviors such as vocalization, swallowing, or vomiting are underpinned. Finally, we describe the impact of absence or malfunction of postinspiratory motor function in neurological diseases

Brainstem-mediated sniffing and respiratory modulation during odor stimulation

The trigeminal and olfactory systems interact during sensory processing of odor. Here, we investigate odor-evoked modulations of brainstem respiratory networks in a decerebrated perfused brainstem preparation of rat with intact olfactory bulbs. Intranasal application of non-trigeminal odors (rose) did not evoke respiratory modulation in absence of cortico-limbic circuits. Conversely, trigeminal odors such as menthol or lavender evoked robust respiratory modulations via direct activation of preserved brain stem circuits. Trigeminal odors consistently triggered short phrenic nerve bursts (fictive sniff), and the strong trigeminal odor menthol also triggered a slowing of phrenic nerve frequency. Phrenic and vagal nerve recordings reveal that fictive sniffs transiently interrupted odor evoked tonic postinspiratory vagal discharge. This motor pattern is significantly different from normal (eupneic) respiratory activity. In conclusion, we show for the first time the direct involvement of brainstem circuits in primary odor processing to evoke protective sniffs and respiratory modulation in the complete absence of forebrain commands. (C) 2016 Elsevier B.V. All rights reserved