This educational review outlines the pathophysiology of asthma, key aspects of preoperative evaluation of children with asthma, and provides updates in asthma treatment from multinational guidelines, including recommendations for the treatment of bronchospasm under anaesthesia.

This review focuses on the ‘Th2’ or ‘atopic, aspirin exacerbated respiratory disease’ (AERD) endotype, as it is by far the most common in paediatric asthma, where sensitisation to aeroallergens results in CD4 activation and release of interleukins IL4, IL5 and IL13.

Preoperative evaluation:

Spirometry and peak expiratory flow rate (PEFR) cannot be reliably performed in children under 5 years, therefore history and examination findings may be more pragmatic in the perioperative setting.

This small, randomized control study of 40 patients investigated the utility of erector spinae plane blocks (ESPB) in paediatric sternotomy for cardiac procedures. The primary outcome was cumulative morphine consumption in the first 24 hours post-operatively. Secondary outcomes included pain & sedation, time to extubation and ICU length of stay.

The mean age of patients presenting for cardiac surgery was 6 years (range 2 – 10 years), with procedures limited to ASD or VSD closures & aortic membrane excision. Notably the duration of surgery was significantly longer in the ESPB group, and this group also received 2 microg/kg more fentanyl than the control group despite an apparent set timing and dose protocol for the administration of Fentanyl intra-op. This was not significant, but no explanation was offered in the paper either.

Strengths and weaknesses

Strengths of the study included that there were only 2 people experienced with performing ESPB doing the blocks in a standardized manner. The assessor measuring pain scores in the first 24 hours was blinded. Blocks were performed at a standardized period in the perioperative journey (prior to surgery & after induction of anaesthesia).

What?

• A retrospective chart review of 94 patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis between 2015 and 2020 at the American Family Children’s Hospital, University of Wisconsin, USA.
• Three patient groups:
  • Group PCA received a hydromorphone PCA without methadone
  • Group PCA + Methadone received pre-incisional methadone and a hydromorphone PCA
  • Group Methadone received pre-incisional methadone, scheduled postoperative methadone, and no PCA
• Methadone dosing:
  • Pre-incisional methadone 0.2 mg/kg (max 20 mg)
  • Post-operative methadone 0.1mg/kg (max 5 mg) IV in the PACU at first request for analgesia, and methadone 0.1 mg/kg (max 5 mg) IV 6 h after the PACU dose, with backup rescue hydromorphone IV boluses available on request.
• The primary outcome was postoperative opioid use over 72hrs. Secondary outcomes included pain scores, sedation scores and length of stay.
• Intraoperatively all patients received TIVA with remifentanil or fentanyl infusion and additional opioid boluses at the anaesthetist’s discretion.
• The study period included post-operative days 0-3.

Study Design

• Prospective, double-blinded, randomized, placebo-controlled trial. Single centre in USA where intrathecal morphine (ITM) is commonly utilised.
• Ondansetron 0.1mg/kg (max 16mg) or placebo given IV just prior and q6hrly for 24 hours after ITM (4-5mcg/kg) for urological or orthopaedic surgery.
• Inclusion criteria: age 3-17 years; ≤100kg weight; able to use pain assessment tool.
• Exclusion criteria: posterior spinal fusion operations; hypersensitivity or contraindications to any anti-pruritic and anti-emetic in the study protocol; regular 5-HT₃ antagonist or SSRI use.
• Routine anti-emetics given: dexamethasone 0.15mg/kg (max 4mg) and diphenhydramine 0.3mg/kg (max 12.5mg).
• Postoperatively:
  • Treatment of pruritus: 1^st nalbuphine, 2^nd diphenhydramine
  • Treatment of PONV: 1^st prochlorperazine, 2^nd promethazine
• Power calculation suggested 56 patients in each group (total N=112) would be adequate to detect reduction in pruritus from 40% to 20%.

An animal study (rats), investigating whether pre-treatment with dexmedetomidine (DEX) can reduce sevoflurane-induced neuronal hyperexcitation and corticosterone release at the time of exposure, as well as the long-term neurodevelopmental effects of sevoflurane (SEVO).

Methods:

Rats were randomized into:

• DEX (25 mcg/kg intraperitoneal) before exposure to 2.1% SEVO for 6 hours
• Vehicle (intraperitoneal) before exposure to 2.1% SEVO for 6 hours
• DEX-only group received DEX without exposure to SEVO
• Control group received the vehicle only

An RCT of adult patients undergoing surgery (urology, gynaecology, peripheral) with mandatory ventilation via a Proseal LMA mask randomised to PEEP 8.2 cmH₂O (PEEP group) or PEEP 0 cmH₂O (ZEEP group). Does this result in a higher incidence of gas leakage?

Methods

Adult ASA I/II patients were anaesthetised with Proseal LMA placed then given a mandatory ventilation protocol with no spontaneous breathing for the first 30 minutes of the case.

527 patients randomised: 174 ZEEP vs 208 PEEP

This review article addresses key questions about regional anaesthesia in paediatric practice.

1. Blocks under GA or deep sedation are safe in children and should be the default.

•  The benefit of an awake patient (ability to alert the practitioner to early signs of local anaesthetic toxicity or intraneural injection) is greatly outweighed by the risk of damage when the target is moving, or the patient is uncooperative.
• In 2018, a published registry of 100,000 cases confirmed the safety of this practice. They reported zero cases of permanent nerve damage, an incidence of 2.4:100,000 of temporary nerve damage and 0.76:100,000 of local anaesthetic systemic toxicity.

What?

A review of 1438 lower limb nerve blocks in 1038 children.

Where?

Royal Children’s Hospital, Melbourne

How?

Retrospective review of prospective data from 2016-2021 in children who had had lower limb surgery. Data obtained from the electronic record included demographics, type of block, technique, catheter use, adjuvant drugs used.

Findings

There were a wide range of surgical indications.

This paper is a systematic review to assess the safety and efficacy of levosimendan use in paediatric cardiac surgery. It was done by the anaesthesiology department of Leuven, Belgium.

Children are known to potentially suffer negative behavioural changes (NBC) following general anaesthesia and surgical/diagnostic procedures. These may be new or a worsening of pre-existing behaviour. Premedications such as midazolam and clonidine are thought to not only help allay preoperative anxiety, but possibly reduce the incidence of NBCs. Clonidine’s longer lasting sedative effect may make it better at limiting postoperative NBCs.