Nerve stimulator for regional anaesthesia procedures with automatic interactive closed-loop control

Abstract

Peripheral nerve stimulators have widespread among anaesthesiologists and remain a popular technique. However, in commercial devices, the user has to manually adjust stimulus intensity. Thus, the aim of this study is to propose a method that allows automating the current intensity control. An earlier nerve stimulator prototype was modified to add an accelerometer and an sEMG module. The choice of these two sensors is aimed at the possibility of observing the mechanical and electrical responses of the muscle contraction evoked by the stimulation. The tests were performed in two steps. The first step was to observe how the sensors behave during stimulation and muscle contraction. The second step was to implement a control algorithm and to validate the automation technique. Comparing the two methods, no significant differences were found on procedure time (manual: 12.5?±?2.3; automatic: 11.6?±?1.9; ρ?=0.380) and blockade latency time (manual: 11.6?±?1.1; automatic: 11.9?±?1.2; ρ?=0.524). Comparing needle-nerve distance in manual or automatic mode, no significant differences were found for 1.0?mA, 0.8?mA, 0.5?mA and 0.3?mA. We conclude that the technique for automating the current intensity update, using accelerometer and/or electromyography, is satisfactory. Furthermore, we conclude that the use of the accelerometer alone is sufficient for detection of muscle contraction.     

The value of surveys in obstetric anaesthesia

BackgroundThe Obstetric Anaesthetists’ Association (OAA) has facilitated national surveys in obstetric anaesthesia since 1998. We wanted to examine trends in OAA-approved surveys since this time.MethodsOAA-approved surveys performed between January 1998 and December 2012 were examined for the year they were carried out, the format (postal or electronic), the target group and the response rate. We determined whether each survey was presented or published. For each survey published as a substantive paper, we identified the number of times the publication had been cited. We also surveyed lead obstetric anaesthetists and expert witnesses practising in obstetric anaesthesia on the perceived usefulness of OAA-approved surveys.ResultsOne hundred and thirty-five surveys approved by the OAA were carried out between 1998 and 2012. Response rates have fallen over the years, reaching a current plateau of 65%. Response rates varied with the target group. Seventy-eight percent of surveys were presented and 83% were published in some form. For surveys published as substantive papers (n=34, 25%), the median [IQR (range)] number of citations was 6 [3–11 (0–36)] per publication. Our survey of lead obstetric anaesthetists had a response rate of 62%. Those who replied rated OAA surveys a median [IQR (range)] of 6 [5–7 (1–9)] on a 0–10 scale of usefulness to their clinical practice.ConclusionsResponse rates to OAA-approved surveys have declined but remain acceptable despite an increase in the number of surveys performed. Most surveys were presented or published in some form.     

Failed tracheal intubation during obstetric general anaesthesia: a literature review

We reviewed the literature on obstetric failed tracheal intubation from 1970 onwards. The incidence remained unchanged over the period at 2.6 (95% CI 2.0 to 3.2) per 1000 anaesthetics (1 in 390) for obstetric general anaesthesia and 2.3 (95% CI 1.7 to 2.9) per 1000 general anaesthetics (1 in 443) for caesarean section. Maternal mortality from failed intubation was 2.3 (95% CI 0.3 to 8.2) per 100 000 general anaesthetics for caesarean section (one death per 90 failed intubations). Maternal deaths occurred from aspiration or hypoxaemia secondary to airway obstruction or oesophageal intubation. There were 3.4 (95% CI 0.7 to 9.9) front-of-neck airway access procedures (surgical airway) per 100 000 general anaesthetics for caesarean section (one procedure per 60 failed intubations), usually carried out as a late rescue attempt with poor maternal outcomes. Before the late 1990s, most cases were awakened after failed intubation; since the late 1990s, general anaesthesia has been continued in the majority of cases. When general anaesthesia was continued, a laryngeal mask was usually used but with a trend towards use of a second-generation supraglottic airway device. A prospective study of obstetric general anaesthesia found that transient maternal hypoxaemia occurred in over two-thirds of cases of failed intubation, usually without sequelae. Pulmonary aspiration occurred in 8% but the rate of maternal intensive care unit admission after failed intubation was the same as that after uneventful general anaesthesia. Poor neonatal outcomes were often associated with preoperative fetal compromise, although failed intubation and lowest maternal oxygen saturation were independent predictors of neonatal intensive care unit admission.     

Patient blood management in orthopaedic surgery: a four-year follow-up of transfusion requirements and blood loss from 2008 to 2011 at the Balgrist University Hospital in Zurich,Switzerland

Background

The aim of this study was to investigate the impact of the introduction of a Patient Blood Management (PBM) programme in elective orthopaedic surgery on immediate pre-operative anaemia, red blood cell (RBC) mass loss, and transfusion.

Materials and methods

Orthopaedic operations (hip, n=3,062; knee, n=2,953; and spine, n=2,856) performed between 2008 and 2011 were analysed. Period 1 (2008), was before the introduction of the PBM programme and period 2 (2009 to 2011) the time after its introduction. Immediate pre-operative anaemia, RBC mass loss, and transfusion rates in the two periods were compared.

Results

In hip surgery, the percentage of patients with immediate pre-operative anaemia decreased from 17.6% to 12.9% (p<0.001) and RBC mass loss was unchanged, being 626±434 vs 635±450 mL (p=0.974). Transfusion rate was significantly reduced from 21.8% to 15.7% (p<0.001). The number of RBC units transfused remained unchanged (p=0.761). In knee surgery the prevalence of immediate pre-operative anaemia decreased from 15.5% to 7.8% (p<0.001) and RBC mass loss reduced from 573±355 to 476±365 mL (p<0.001). The transfusion rate dropped from 19.3% to 4.9% (p<0.001). RBC transfusions decreased from 0.53±1.27 to 0.16±0.90 units (p<0.001). In spine surgery the prevalence of immediate pre-operative anaemia remained unchanged (p=0.113), RBC mass loss dropped from 551±421 to 404±337 mL (p<0.001), the transfusion rate was reduced from 18.6 to 8.6% (p<0.001) and RBC transfusions decreased from 0.66±1.80 to 0.22±0.89 units (p=0.008).

Discussion

Detection and treatment of pre-operative anaemia, meticulous surgical technique, optimal surgical blood-saving techniques, and standardised transfusion triggers in the context of PBM programme resulted in a lower incidence of immediate pre-operative anaemia, reduction in RBC mass loss, and a lower transfusion rate.     

Avulsion and replantation of a primary incisor tooth

Avulsion of a primary tooth is a serious dental trauma, and the guidelines of the International Association of Dental Traumatology and textbooks in paediatric dentistry do not recommend replantation. Such management can result in severe damage to the supporting structures, and together with avulsion itself is commonly associated with developmental disturbances of the permanent tooth. We report the case of replantation in a 9‐month‐old child with a successful outcome, in a unique situation where conditions were optimal and careful long‐term follow up was possible.     

Increased hippocampal CD38 and systemic inflammation after partial hepatectomy does not induce impairment of spatial cognition

Objective: The role of inflammation in cognitive alterations in a post-operative setting is still not fully understood. Surgical interventions can cause systemic inflammations which eventually can induce neuroinflammation. However, the main causes of functional changes after surgery are still elusive. In this study, we investigated the role of CD38, a TNFα-inducible NADH⁺ cyclase and hydrolase. We assume that CD38 overexpression impairs mitochondrial ATP synthesis. Within the hippocampus, the resulting cellular death could lead to cognitive impairment.

Methods: Seventy-nine Wistar-HAN rats were subjected for three hours either to partial hepatectomy under sevoflurane anaesthesia (‘surgery’), sevoflurane anaesthesia alone (‘anaesthesia’) or control. Rats were randomly selected to determine levels of CD38, TNFα, IL-6, and ATP, for GFAP immunohistochemistry and for Morris Water Maze testing.

Results: Plasma TNFα and IL-6 levels were significantly higher in the surgery group in the immediate post-operative phase. GFAP expression and hippocampal CD38 concentration were significantly elevated 24 h after the intervention in the surgery group as compared to anaesthesia alone and controls. ATP levels did not differ significantly between the three groups. No treatment differences in spatial cognition parameters were found.

Conclusions: Surgery in the form of partial hepatectomy activated the peripheral immune system and induced hippocampal glial activation and a CD38 increase. These changes, however, were not associated with rats’ cognitive impairment ≥24 h after surgery.     

Intravenous anaesthetic agents

This article gives an overview of drugs frequently used for intravenous anaesthetic induction, as well as a brief overview of total intravenous anaesthesia. Physicochemical properties of intravenous anaesthetic drugs and their clinical and adverse effects are summarized. The article also discusses the historical context on the introduction of intravenous anaesthetic agents and highlights developments of novel agents.