Oral sucrose as an analgesic drug for procedural pain in newborn infants: a randomised controlled trial

BACKGROUND

Many infants admitted to hospital undergo repeated invasive procedures. Oral sucrose is frequently given to relieve procedural pain in neonates on the basis of its effect on behavioural and physiological pain scores. We assessed whether sucrose administration reduces pain-specific brain and spinal cord activity after an acute noxious procedure in newborn infants.

METHODS

In this double-blind, randomised controlled trial, 59 newborn infants at University College Hospital (London, UK) were randomly assigned to receive 0·5 mL 24% sucrose solution or 0·5 mL sterile water 2 min before undergoing a clinically required heel lance. Randomisation was by a computer-generated randomisation code, and researchers, clinicians, participants, and parents were masked to the identity of the solutions. The primary outcome was pain-specific brain activity evoked by one time-locked heel lance, recorded with electroencephalography and identified by principal component analysis. Secondary measures were baseline behavioural and physiological measures, observational pain scores (PIPP), and spinal nociceptive reflex withdrawal activity. Data were analysed per protocol. This study is registered, number ISRCTN78390996.

FINDINGS

29 infants were assigned to receive sucrose and 30 to sterilised water; 20 and 24 infants, respectively, were included in the analysis of the primary outcome measure. Nociceptive brain activity after the noxious heel lance did not differ significantly between infants who received sucrose and those who received sterile water (sucrose: mean 0·10, 95% CI 0·04-0·16; sterile water: mean 0·08, 0·04-0·12; p=0·46). No significant difference was recorded between the sucrose and sterile water groups in the magnitude or latency of the spinal nociceptive reflex withdrawal recorded from the biceps femoris of the stimulated leg. The PIPP score was significantly lower in infants given sucrose than in those given sterile water (mean 5·8, 95% CI 3·7-7·8 vs 8·5, 7·3-9·8; p=0·02) and significantly more infants had no change in facial expression after sucrose administration (seven of 20 [35%] vs none of 24; p<0·0001).

INTERPRETATION

Our data suggest that oral sucrose does not significantly affect activity in neonatal brain or spinal cord nociceptive circuits, and therefore might not be an effective analgesic drug. The ability of sucrose to reduce clinical observational scores after noxious events in newborn infants should not be interpreted as pain relief.

FUNDING

Medical Research Council.

An anatomical evaluation of the serratus anterior plane block

The serratus anterior plane block has been described for analgesia of the hemithorax. This study was conducted to determine the spread of injectate and investigate the anatomical basis of the block. Ultrasound-guided serratus anterior plane block was performed on six soft-fix embalmed cadavers. All cadavers received bilateral injections, on one side performed with 20 ml latex and on the other with 20 ml methylene blue. Subsequent dissection explored the extent of spread and nerve involvement. Photographs were taken throughout dissection. The intercostal nerves were involved on three occasions with dye, but not with latex. The lateral cutaneous branches of the intercostal nerve contained dye and latex on all occasions. The serratus plane block appears to be mediated through blockade of the lateral cutaneous branches of the intercostal nerves. Anatomically, serratus plane block does not appear to be equivalent to paravertebral block for rib fracture analgesia.

Subunit-selective modulation of GABAA receptors by the non-steroidal anti-inflammatory agent, mefenamic acid

Mefenamic acid (MFA) has anti-convulsant and pro-convulsant effects in vivo, and has been shown to potentiate and inhibit GABAA (gamma-aminobutyric acid) receptors in vitro. In this study, whole-cell currents were recorded from Xenopus oocytes and human embryonic kidney (HEK) cells expressing human recombinant GABAA receptors to resolve the molecular mechanisms by which MFA modulates GABAA receptor function. We demonstrate that MFA potentiated GABA-activated currents for alpha1beta2 gamma2S (EC50 = 3.2 +/- 0.5 microM), but not for alpha1beta1 gamma2S receptors. MFA also enhanced GABA-activated responses and directly activated alpha1beta2/beta3 GABAA receptors, but inhibited responses to GABA on alpha1beta1 constructs (IC50 = 40 +/- 7.2 microM). A comparison of beta1, beta2 and beta3 subunits suggested that the positive modulatory action of MFA involved asparagine (N) 290 in the second transmembrane domain (TM2) of the beta2 and beta3 subunits. Mutation of N290 to serine (S) markedly reduced modulation by MFA in alpha1beta2(N290S)gamma2S receptors, whereas alpha1beta1(S290N)gamma2S constructs revealed potentiated responses to GABA (EC50 = 7.8 +/- 1.7 microM) and direct activation by MFA. The potentiation by MFA displayed voltage sensitivity. The direct activation, potentiation and inhibitory aspects of MFA action were predominantly conferred by the beta subunits as the spontaneously active homomeric beta1 and beta3 receptors were susceptible to modulation by MFA. Molecular comparisons of MFA, loreclezole and etomidate, agents which exhibit similar selectivity for GABAA receptors, revealed their ability to adopt similar structural conformations. This study indicates that N290 in TM2 of beta2 and beta3 subunits is important for the regulation of GABAA receptor function by MFA. Our data provide a potential molecular mechanism for the complex central effects of MFA in vivo.

Purification and amino acid sequence of a highly insecticidal toxin from the venom of the brazilian spider Phoneutria nigriventer which inhibits NMDA-evoked currents in rat hippocampal neurones

A new insecticidal toxin Tx4(5-5) was isolated from the fraction PhTx4 of the venom of the spider Phoneutria nigriventer by reverse phase high performance liquid chromatography (HPLC) and anion exchange HPLC. The complete amino acid sequence determined by automated Edman degradation showed that Tx4(5-5) is a single chain polypeptide composed of 47 amino acid residues, including 10 cysteines, with a calculated molecular mass of 5175 Da. Tx4(5-5) shows 64% of sequence identity with Tx4(6-1), another insecticidal toxin from the same venom. Tx4(5-5) was highly toxic to house fly (Musca domestica), cockroach (Periplaneta americana) and cricket (Acheta domesticus ), producing neurotoxic effects (knock-down, trembling with uncoordinated movements) at doses as low as 50 ng/g (house fly), 250 ng/g (cockroach) and 150 ng/g (cricket). In contrast, intracerebroventricular injections (30 microg) into mice induced no behavioural effects. Preliminary electrophysiological studies carried out on whole-cell voltage-clamped rat hippocampal neurones indicated that Tx4(5-5) (at 1 microM) reversibly inhibited the N-methyl-D-aspartate-subtype of ionotropic glutamate receptor, while having little or no effect on kainate-, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid- or gamma-aminobutyric acid-activated currents.

An electrophysiological study of the effects of propofol on native neuronal ligand-gated ion channels

1. Pharmacological evidence suggests that some of the clinical actions of propofol may be mediated, at least in part, by positive modulation of the GABA(A) receptor chloride channel. The effect of propofol at other native neuronal ligand-gated ion channels is unclear. 2. To gain some insight into the effects of propofol at a range of native neuronal receptors, the present study has used an extracellular recording technique and determined its effects at GABA(A), 5-HT3, P2X and nicotinic acetylcholine (nACh) receptors of the rat isolated vagus nerve and the GABA(A) and strychnine-sensitive glycine receptor of the rat isolated optic nerve. In addition, we have used patch-clamp recording techniques to further investigate the effects of propofol at the GABA(A) and strychnine-sensitive glycine receptors in rat cultured hippocampal neurons. 3. Propofol (0.3-100 micromol/L) concentration-dependently potentiated submaximal GABA-evoked responses in the vagus nerve and shifted the GABA concentration-response curve to the left. In contrast, propofol at concentrations ranging from 1 to 10 micromol/L had little or no effect on 5-HT3, P2X or nACh receptor-mediated responses in the vagus nerve but, at 100 micromol/L, propofol inhibited these responses to approximately 50% of control. In the optic nerve, EC20 GABA-evoked responses were also potentiated by propofol (10 micromol/L), while EC20 glycine-evoked responses were minimally enhanced. 4. Further investigations using cultured hippocampal neurons showed that submaximal (10 micromol/L) GABA-evoked currents were potentiated by propofol (1-10 micromol/L), in a non-voltage-dependent manner, whereas submaximal (100 micromol/L) glycine-evoked currents were unaffected. 5. These data suggest that propofol, at therapeutic concentrations, exerts its principle pharmacological actions at GABA(A) receptors with relatively little effect at other neuronal ligand-gated ion channels.

Scrotal ultrasonography

Scrotal ultrasonography was performed on 43 patients with a diagnostic accuracy rate of 88 per cent. With a small parts 7.5 MHz. real-time ultrasound scanner a clear distinction between gonadal and epididymal pathologic conditions can be achieved in the majority of cases.

Student attitudes to peer physical examination: a qualitative study of changes in expressed willingness to participate

BACKGROUND

A number of studies have explored student attitudes to examining each other (peer physical examination: PPE). Differences have emerged in whether students prefer to be examined by friends or strangers. Changes have been reported in how students feel about PPE if asked before or after the PPE programme commences. RESEARCH INTENTION: Since a Grounded Theory paradigm was employed, there was no formal research hypothesis: the research intention was to explore factors which might underlie changes in student willingness to undertake PPE following familiarity with the process.

METHODS

Students who had completed an Examining Fellow Students Questionnaire at the beginning and end of the academic year, and who had indicated a change in willingness to participate, were invited to attend focus groups. Four focus groups were convened and transcripts were analysed for common themes.

RESULTS

Surprisingly, students downplayed the significance of changes. Also unexpectedly, dichotomous views emerged on familiarity, with some students preferring friends for examination and others preferring strangers. Staff embarrassment also emerged as a factor inhibiting student participation.

CONCLUSIONS

The significance of reported changes in attitudes to PPE may have been exaggerated. Proposals for increasing the willingness of students to participate in PPE are developed from the emergent themes.

Electroglottographic tracking of phonatory response to Botox

Botox injection into the thyroarytenoid muscle is thought to alter the glottal competence and laryngeal adduction of patients with adductor spasmodic dysphonia (ADSD). Hypofunctional responses to treatment have been rated subjectively and inferred from postinjection breathy voice, aphonia, midline glottal gap, or subclinical aspiration. Clinical experience suggests that temporary hypofunction varies in duration and severity among patients. This study used electroglottographic measures to examine changes over time in glottal competence during the relatively stable phonation produced by 5 patients with ADSD. Hierarchical linear modeling was used to test 3 hypotheses: (a) that reduced laryngeal adduction would occur during the first 3 weeks postinjection, followed by a reversal; (b) that patients' hypofunctional response curves would differ one from another; and (c) that changes in adduction, if present, would be related to changes in severity ratings of ADSD symptoms. For 3 participants, significant hypoadduction occurred after injection and reversed toward preinjection level over an 8-week period. Two participants demonstrated a flat or increasing vocal fold contact response curve during the early postinjection period. Observations were consistent with the previously reported differences and possibly complex relation between the resolution of breathy hypofunction and ultimate return of ADSD symptoms.

Electrophysiological measurements and analysis of nociception in human infants

Pain is an unpleasant sensory and emotional experience. Since infants cannot verbally report their experiences, current methods of pain assessment are based on behavioural and physiological body reactions, such as crying, body movements or changes in facial expression. While these measures demonstrate that infants mount a response following noxious stimulation, they are limited: they are based on activation of subcortical somatic and autonomic motor pathways that may not be reliably linked to central sensory processing in the brain. Knowledge of how the central nervous system responds to noxious events could provide an insight to how nociceptive information and pain is processed in newborns. The heel lancing procedure used to extract blood from hospitalised infants offers a unique opportunity to study pain in infancy. In this video we describe how electroencephalography (EEG) and electromyography (EMG) time-locked to this procedure can be used to investigate nociceptive activity in the brain and spinal cord. This integrative approach to the measurement of infant pain has the potential to pave the way for an effective and sensitive clinical measurement tool.

Putting the Cart Before the Horse? Developing a Blended Anatomy Curriculum Supplemented by Cadaveric Anatomy

Cadaveric anatomy is frequently described as the gold standard for anatomy education. Increasingly and especially following the COVID-19 pandemic, there is acceptance that a blended approach for anatomy curriculum delivery is optimal for learners.Setting up a new UK Medical School in 2019 necessitated building a new cadaveric anatomy facility. To enable anatomy curriculum delivery during the construction period (2019-2021), a technology-enhanced learning (TEL) anatomy curriculum was developed, as well as an anatomy laboratory suitable for TEL. Development of a TEL anatomy curriculum with the later inclusion of cadaveric anatomy is unusual since the typical model is to supplement cadaveric anatomy with TEL approaches.TEL solutions that provide digital visualisation of anatomy may support learners by reducing cognitive load. Examples include using colour and/or translucency features to highlight and signpost pertinent anatomy and constructing virtual anatomical models in real time, rather than dissection. Radiology and portable ultrasound provide clinically contextualised visualisations of anatomy; the latter offers a haptic learning experience too. A TEL anatomy laboratory can provide interactive learning experiences for engagement and outreach activities for young school children, where cadaveric anatomy is not suitable.