Malignant hyperthermia 2020: Guideline from the Association of Anaesthetists.

Malignant hyperthermia is defined in the International Classification of Diseases as a progressive life-threatening hyperthermic reaction occurring during general anaesthesia. Malignant hyperthermia has an underlying genetic basis, and genetically susceptible individuals are at risk of developing malignant hyperthermia if they are exposed to any of the potent inhalational anaesthetics or suxamethonium. It can also be described as a malignant hypermetabolic syndrome. There are no specific clinical features of malignant hyperthermia and the condition may prove fatal unless it is recognised in its early stages and treatment is promptly and aggressively implemented. The Association of Anaesthetists has previously produced crisis management guidelines intended to be displayed in all anaesthetic rooms as an aide memoire should a malignant hyperthermia reaction occur. The last iteration was produced in 2011 and since then there have been some developments requiring an update. In these guidelines we will provide background information that has been used in updating the crisis management recommendations but will also provide more detailed guidance on the clinical diagnosis of malignant hyperthermia. The scope of these guidelines is extended to include practical guidance for anaesthetists dealing with a case of suspected malignant hyperthermia once the acute reaction has been reversed. This includes information on care and monitoring during and after the event; appropriate equipment and resuscitative measures within the operating theatre and ICU; the importance of communication and teamwork; guidance on counselling of the patient and their family; and how to make a referral of the patient for confirmation of the diagnosis. We also review which patients presenting for surgery may be at increased risk of developing malignant hyperthermia under anaesthesia and what precautions should be taken during the peri-operative management of the patients.

Logistic early warning scores to predict death, cardiac arrest or unplanned intensive care unit re-admission after cardiac surgery.

NHS England recently mandated that the National Early Warning Score of vital signs be used in all acute hospital trusts in the UK despite limited validation in the postoperative setting. We undertook a multicentre UK study of 13,631 patients discharged from intensive care after risk-stratified cardiac surgery in four centres, all of which used VitalPACTM to electronically collect postoperative National Early Warning Score vital signs. We analysed 540,127 sets of vital signs to generate a logistic score, the discrimination of which we compared with the national additive score for the composite outcome of: in-hospital death; cardiac arrest; or unplanned intensive care admission. There were 578 patients (4.2%) with an outcome that followed 4300 sets of observations (0.8%) in the preceding 24 h: 499 out of 578 (86%) patients had unplanned re-admissions to intensive care. Discrimination by the logistic score was significantly better than the additive score. Respective areas (95%CI) under the receiver-operating characteristic curve with 24-h and 6-h vital signs were: 0.779 (0.771-0.786) vs. 0.754 (0.746-0.761), p < 0.001; and 0.841 (0.829-0.853) vs. 0.813 (0.800-0.825), p < 0.001, respectively. Our proposed logistic Early Warning Score was better than the current National Early Warning Score at discriminating patients who had an event after cardiac surgery from those who did not.

Fibreoptic-guided tracheal intubation through i-gel® and LMA® ProtectorTM supraglottic airway devices - a randomised comparison.

Fibreoptic-guided tracheal intubation using a supraglottic airway device as a conduit is a technique that can be used in anticipated and unanticipated difficult airway management. Although the i-gel® supraglottic airway device has been examined for this purpose, the LMA® ProtectorTM , a recently introduced second-generation supraglottic airway device, has not been evaluated for this use in clinical trials. This prospective, randomised clinical trial compared fibreoptic-guided tracheal intubation via i-gel and LMA Protector supraglottic airway devices in two UK hospitals. Patients who were ASA physical status 1 or 2 and undergoing elective surgery requiring tracheal intubation were recruited to the study. A block randomisation list was generated for each study site. The primary outcome measure was time to successful tracheal intubation and secondary outcomes were tracheal intubation success rate, glottic view through flexible fibrescope, ease of tracheal intubation using operator visual analogue score, supraglottic airway device insertion time and insertion success rate. Ninety patients were randomly allocated to each device, and final data analysis was carried out for 92 patients in the i-gel group and 86 patients in the LMA Protector group. Mean (SD) tracheal intubation time in the i-gel and LMA Protector groups were 54.3 (13.8) s and 52.0 (13.0) s, respectively (p = 0.240). There were no significant differences in tracheal intubation success rate, glottic view and ease of tracheal intubation between the two groups. This study demonstrates that the LMA Protector supraglottic airway device is comparable to the i-gel supraglottic airway device as a conduit for fibreoptic-guided tracheal intubation.

Evaluation of changes in tidal volume during mask ventilation following administration of neuromuscular blocking drugs.

The practice of checking the ability to mask ventilate before administering neuromuscular blocking drugs remains controversial. We prospectively evaluated the changes in the expired tidal volume during pressure-controlled ventilation (two-handed mask ventilation technique) as a surrogate marker to assess the ease of mask ventilation following administration of rocuronium. After informed consent, 125 patients were anaesthetised using a standard induction technique consisting of fentanyl, propofol and rocuronium, with anaesthesia then maintained with isoflurane in oxygen. The mean (SD) expired tidal volume before administration of rocuronium increased by 61 (13) ml at 2 min following onset of neuromuscular block (p < 0.001). This supports the concept that neuromuscular blockade induced by rocuronium facilitates mask ventilation.

Puerperal uterine inversion and shock.

Uterine inversion is an unusual and potentially life-threatening event occurring in the third stage of labour. It is associated with significant blood loss, and shock, which may be out of proportion to the haemorrhage, although this is questionable. When managed promptly and aggressively, uterine inversion can result in minimal maternal morbidity and mortality. A recent case is described, followed by a short review of the literature.

Functional iron deficiency, infection and systemic inflammatory response syndrome in critical illness.

To investigate the prevalence and clinical relevance of functional iron deficiency in the critically ill, we performed a prospective observational study in a university hospital general intensive care unit. We collected patient demographics, severity of illness data, haematological and biochemical variables in 51 consecutive admissions. We recorded episodes of culture-positive infection. Functional iron deficiency (FID), measured by red cell hypochromasia on flow cytometry, was present in 35% of patients at admission to intensive care. FID patients were of similar age, diagnosis, APACHE score, sequential organ failure assessment (SOFA) score, haemoglobin, serum B12, folate and ferritin to patients without FID. However, patients with FID had a prolonged intensive care stay compared with non-FID patients (P<0.001) and increased time to hospital discharge (P=0.09). Duration of intensive care stay correlated with severity of FID (r=0.33, P<0.02). Systemic inflammatory response syndrome (SIRS) was present for longer in those with FID (P<0.02). Overall mortality did not differ between groups. No difference was seen in the incidence of positive cultures between those with FID (9/18 patients) and those without FID (15/33 patients). FID was independently associated only with abnormal white blood cell count (WBC < 4 or > 11 x 10(9) x l(-1)) at admission to ICU, P=0.007, but not with positive cultures. There is a high prevalence of FID in intensive care, associated with an increased duration of stay and duration of SIRS. We have been unable to demonstrate a link with infection, either as a predisposing factor or as an acute response.