Exposure to halogenated ethers causes neurodegeneration and behavioural changes in young healthy experimental animals: a systematic review and meta analyses

The FDA issued a warning that repeated and prolonged use of inhalational anaesthetics in children younger than 3 years may increase the risk of neurological damage. Robust clinical evidence supporting this warning is however lacking. A systematic review of all preclinical evidence concerning isoflurane, sevoflurane, desflurane and enflurane exposure in young experimental animals on neurodegeneration and behaviour may elucidate how severe this risk actually is PubMed and Embase were comprehensively searched on November 23, 2022. Based on predefined selection criteria the obtained references were screened by two independent reviewers. Data regarding study design and outcome data (Caspase-3 and TUNEL for neurodegeneration, Morris water maze (MWM), Elevated plus maze (EPM), Open field (OF) and Fear conditioning (FC)) were extracted, and individual effect sizes were calculated and subsequently pooled using the random effects model. Subgroup analyses were predefined and conducted for species, sex, age at anesthesia, repeated or single exposure and on time of outcome measurement. Out of the 19.796 references screened 324 could be included in the review. For enflurane there were too few studies to conduct meta-analysis (n = 1). Exposure to sevoflurane, isoflurane and desflurane significantly increases Caspase-3 levels and TUNEL levels. Further, sevoflurane and isoflurane also cause learning and memory impairment, and increase anxiety. Desflurane showed little effect on learning and memory, and no effect on anxiety. Long term effects of sevoflurane and isoflurane on neurodegeneration could not be analysed due to too few studies. For behavioural outcomes, however, this was possible and revealed that sevoflurane caused impaired learning and memory in all three related outcomes and increased anxiety in the elevated plus maze. For isoflurane, impaired learning and memory was observed as well, but only sufficient data was available for two of the learning and memory related outcomes. Further, single exposure to either sevoflurane or isoflurane increased neurodegeneration and impaired learning and memory. In summary, we show evidence that exposure to halogenated ethers causes neurodegeneration and behavioural changes. These effects are most pronounced for sevoflurane and isoflurane and already present after single exposure. To date there are not sufficient studies to estimate the presence of long term neurodegenerative effects. Nevertheless, we provide evidence in this review of behavioral changes later in life, suggesting some permanent neurodegenerative changes. Altogether, In contrast to the warning issued by the FDA we show that already single exposure to isoflurane and sevoflurane negatively affects brain development. Based on the results of this review use of sevoflurane and isoflurane should be restrained as much as possible in this young vulnerable group, until more research on the long term permanent effects have been conducted.

Muscle Ultrasound Abnormalities in Individuals with RYR1-Related Malignant Hyperthermia Susceptibility

BACKGROUND

Variants in RYR1, the gene encoding the ryanodine receptor-1, can give rise to a wide spectrum of neuromuscular conditions. Muscle imaging abnormalities have been demonstrated in isolated cases of patients with a history of RYR1-related malignant hyperthermia (MH) susceptibility.

OBJECTIVE

To provide insights into the type and prevalence of muscle ultrasound abnormalities and muscle hypertrophy in patients carrying gain-of-function RYR1 variants associated with MH susceptibility and to contribute to delineating the wider phenotype, optimizing the diagnostic work-up and care for of MH susceptible patients.

METHODS

We performed a prospective cross-sectional observational muscle ultrasound study in patients with a history of RYR1-related MH susceptibility (n = 40). Study procedures included a standardized history of neuromuscular symptoms and a muscle ultrasound assessment. Muscle ultrasound images were analyzed using a quantitative and qualitative approach and compared to reference values and subsequently subjected to a screening protocol for neuromuscular disorders.

RESULTS

A total of 15 (38%) patients had an abnormal muscle ultrasound result, 4 (10%) had a borderline muscle ultrasound screening result, and 21 (53%) had a normal muscle ultrasound screening result. The proportion of symptomatic patients with an abnormal result (11 of 24; 46%) was not significantly higher compared to the proportion of asymptomatic patients with an abnormal ultrasound result (4 of 16; 25%) (P = 0.182). The mean z-scores of the biceps brachii (z = 1.45; P <  0.001), biceps femoris (z = 0.43; P = 0.002), deltoid (z = 0.31; P = 0.009), trapezius (z = 0.38; P = 0.010) and the sum of all muscles (z = 0.40; P <  0.001) were significantly higher compared to 0, indicating hypertrophy.

CONCLUSIONS

Patients with RYR1 variants resulting in MH susceptibility often have muscle ultrasound abnormalities. Frequently observed muscle ultrasound abnormalities include muscle hypertrophy and increased echogenicity.

Low intra-abdominal pressure in laparoscopic surgery: a systematic review and meta-analysis

BACKGROUND

Guidelines do not provide clear recommendations with regard to the use of low intra-abdominal pressure (IAP) during laparoscopic surgery. The aim of this meta-analysis is to assess the influence of low versus standard IAP during laparoscopic surgery on the key-outcomes in perioperative medicine as defined by the StEP-COMPAC consensus group.

MATERIALS AND METHODS

We searched the Cochrane Library, PubMed, and EMBASE for randomized controlled trials comparing low IAP (<10 mmHg) with standard IAP (10 mmHg or higher) during laparoscopic surgery without time, language, or blinding restrictions. According to the PRISMA guidelines, two review authors independently identified trials and extracted data. Risk ratio (RR), and mean difference (MD), with 95% CIs were calculated using random-effects models with RevMan5. Main outcomes were based on StEP-COMPAC recommendations, and included postoperative complications, postoperative pain, postoperative nausea and vomiting (PONV) scores, and length of hospital stay.

RESULTS

Eighty-five studies in a wide range of laparoscopic procedures (7349 patients) were included in this meta-analysis. The available evidence indicates that the use of low IAP (<10 mmHg) leads to a lower incidence of mild (Clavien-Dindo grade 1-2) postoperative complications (RR=0.68, 95% CI: 0.53-0.86), lower pain scores (MD=-0.68, 95% CI: -0.82 to 0.54) and PONV incidence (RR=0.67, 95% CI: 0.51-0.88), and a reduced length of hospital stay (MD=-0.29, 95% CI: -0.46 to 0.11). Low IAP did not increase the risk of intraoperative complications (RR=1.15, 95% CI: 0.77-1.73).

CONCLUSIONS

Given the established safety and the reduced incidence of mild postoperative complications, lower pain scores, reduced incidence of PONV, and shorter length of stay, the available evidence supports a moderate to strong recommendation (1a level of evidence) in favor of low IAP during laparoscopic surgery.

Neuromuscular symptoms in patients with RYR1-related malignant hyperthermia and rhabdomyolysis

Malignant hyperthermia and exertional rhabdomyolysis have conventionally been considered episodic phenotypes that occur in otherwise healthy individuals in response to an external trigger. However, recent studies have demonstrated a clinical and histopathological continuum between patients with a history of malignant hyperthermia susceptibility and/or exertional rhabdomyolysis and RYR1-related congenital myopathies. We hypothesize that patients with a history of RYR1-related exertional rhabdomyolysis or malignant hyperthermia susceptibility do have permanent neuromuscular symptoms between malignant hyperthermia or exertional rhabdomyolysis episodes. We performed a prospective cross-sectional observational clinical study of neuromuscular features in patients with a history of RYR1-related exertional rhabdomyolysis and/or malignant hyperthermia susceptibility (n = 40) compared with healthy controls (n = 80). Patients with an RYR1-related congenital myopathy, manifesting as muscle weakness preceding other symptoms as well as other (neuromuscular) diseases resulting in muscle weakness were excluded. Study procedures included a standardized history of neuromuscular symptoms, a review of all relevant ancillary diagnostic tests performed up to the point of inclusion and a comprehensive, standardized neuromuscular assessment. Results of the standardized neuromuscular history were compared with healthy controls. Results of the neuromuscular assessment were compared with validated reference values. The proportion of patients suffering from cramps (P < 0.001), myalgia (P < 0.001) and exertional myalgia (P < 0.001) was higher compared with healthy controls. Healthcare professionals were consulted because of apparent neuromuscular symptoms by 17/40 (42.5%) patients and 7/80 (8.8%) healthy controls (P < 0.001). Apart from elevated creatine kinase levels in 19/40 (47.5%) patients and mild abnormalities on muscle biopsies identified in 13/16 (81.3%), ancillary investigations were normal in most patients. The Medical Research Council sum score, spirometry and results of functional measurements were also mostly normal. Three of 40 patients (7.5%) suffered from late-onset muscle weakness, most prominent in the proximal lower extremity muscles. Patients with RYR1 variants resulting in malignant hyperthermia susceptibility and/or exertional rhabdomyolysis frequently report additional neuromuscular symptoms such as myalgia and muscle cramps compared with healthy controls. These symptoms result in frequent consultation of healthcare professionals and sometimes in unnecessary invasive diagnostic procedures. Most patients do have normal strength at a younger age but may develop muscle weakness later in life.

Personality in anaesthesiologists, a systematic review of the literature

BACKGROUND

As a central part of their job, anaesthesiologists often have to perform demanding tasks under high-stakes conditions. Yet, some anaesthesiologists seem better able to deal with the demands of the profession than others.

OBJECTIVES

This review aims to answer the following questions. What are the necessary or desirable qualities of an anaesthesiologist? Which personality traits or characteristics have been found in anaesthesiologists? How does personality relate to job performance and work stress among anaesthesiologists?

DESIGN

Systematic review of studies that examined anaesthesiologists' personality or personality characteristics. We performed our synthesis in terms of the five-factor model of personality.

DATA SOURCES

The search was conducted in the PubMed, EMBASE and Web of Science databases. Literature was included until December 2020.

ELIGIBILITY CRITERIA

We included qualitative and quantitative studies that examined anaesthesiologists' personality; also, we included studies that focused on anaesthesiologists' stress, performance or mental health but only if these topics were examined from the perspective of personality.

RESULTS

We included 6 qualitative and 25 quantitative articles. Synthesis of the qualitative articles revealed two classes of desirable technical and nontechnical personality characteristics. Synthesis of the quantitative articles suggested that anaesthesiologists do not essentially differ from other medical specialists. Moreover, our synthesis revealed several personality traits that predict good performance, low stress and good mental health among anaesthesiologists: lower Neuroticism, higher Extraversion, higher Openness and higher Conscientiousness.

CONCLUSION

Those personality traits that predict performance, stress or mental health in anaesthesiologists, also predict performance, stress or mental health in other high demand/high stakes environments (both medical and nonmedical). The ideal anaesthesiologist would be lower on Neuroticism, higher on Extraversion and higher on Conscientiousness.

Chronic stress indicated by hair cortisol concentration in anaesthesiologists and its relationship to work experience and emotional intelligence: A cross-sectional biomarker and survey study

BACKGROUND

Anaesthesia is a stressful medical specialty. The reaction to stress is constituted by behavioural, psychological and physiological components. Chronic physiological stress can have negative consequences for health.

OBJECTIVES

First, we hypothesised that chronic physiological stress is higher for both beginning and late-career consultant anaesthesiologists. Second, we hypothesised that individuals high in emotional intelligence endure lower physiological stress.

DESIGN

Cross-sectional biomarker and survey study.

SETTING

Participants were recruited during the May 2019 annual meeting of the Dutch Anaesthesia Society.

PARTICIPANTS

Of the 1348 colleagues who attended the meeting, 184 (70 male/114 female) participated in the study. Of the study participants, 123 (67%) were consultant anaesthesiologists (52 male/71 female) and 61 (33%) were resident anaesthesiologists (18 male/43 female). Exclusion criteria were endocrine disorders and not having enough hair. Also, experience of a recent major life event led to exclusion from analysis of our hypotheses.

MAIN OUTCOME MEASURES

Chronic physiological stress was measured by hair cortisol concentration. Emotional intelligence was assessed using a validated Dutch version of the Trait Emotional Intelligence Questionnaire. As secondary measures, psychological sources of stress were assessed using validated Dutch versions of the home-work interference (SWING) and the effort-reward imbalance questionnaires.

RESULTS

In support of Hypothesis 1, hair cortisol concentration was highest among early and late-career consultant anaesthesiologists (quadratic effect: b = 45.5, SE = 16.1, t = 2.8, P = 0.006, R2 = 0.14). This nonlinear pattern was not mirrored by self-reported sources of psychological stress. Our results did not support Hypothesis 2; we found no evidence for a relationship between emotional intelligence and physiological stress.

CONCLUSION

In the early and later phases of an anaesthesiologist's career, physiological chronic stress is higher than in the middle of the career. However, this physiological response could not be explained from known sources of psychological stress. We discuss these findings against the background of key differences between physiological and psychological stress.

Deep neuromuscular block reduces the incidence of intra-operative complications during laparoscopic donor nephrectomy: a pooled analysis of randomized controlled trials

Study objective

To assess whether different intensities of intra-abdominal pressure and deep neuromuscular blockade influence the risk of intra-operative surgical complications during laparoscopic donor nephrectomy.

Design

A pooled analysis of ten previously performed prospective randomized controlled trials.

Setting

Laparoscopic donor nephrectomy performed in four academic hospitals in the Netherlands: Radboudumc, Leiden UMC, Erasmus MC Rotterdam, and Amsterdam UMC.

Patients

Five hundred fifty-six patients undergoing a transperitoneal, fully laparoscopic donor nephrectomy enrolled in ten prospective, randomized controlled trials conducted in the Netherlands from 2001 to 2017.

Interventions

Moderate (tetanic count of four > 1) versus deep (post-tetanic count 1–5) neuromuscular blockade and standard (≥10 mmHg) versus low (<10 mmHg) intra-abdominal pressure.

Measurements

The primary endpoint is the number of intra-operative surgical complications defined as any deviation from the ideal intra-operative course occurring between skin incision and closure with five severity grades, according to ClassIntra. Multiple logistic regression analyses were used to identify predictors of intra- and postoperative complications.

Main results

In 53/556 (9.5%) patients, an intra-operative complication with ClassIntra grade ≥ 2 occurred. Multiple logistic regression analyses showed standard intra-abdominal pressure (OR 0.318, 95% CI 0.118–0.862; p = 0.024) as a predictor of less intra-operative complications and moderate neuromuscular blockade (OR 3.518, 95% CI 1.244–9.948; p = 0.018) as a predictor of more intra-operative complications. Postoperative complications occurred in 31/556 (6.8%), without significant predictors in multiple logistic regression analyses.

Conclusions

Our data indicate that the use of deep neuromuscular blockade could increase safety during laparoscopic donor nephrectomy. Future randomized clinical trials should be performed to confirm this and to pursue whether it also applies to other types of laparoscopic surgery.

Trial registration

Clinicaltrials.gov LEOPARD-2 (NCT02146417), LEOPARD-3 trial (NCT02602964), and RELAX-1 study (NCT02838134), Klop et al. (NTR 3096), Dols et al. 2014 (NTR1433).

Positive end-expiratory pressure affects geometry and function of the human diaphragm

Positive end-expiratory pressure (PEEP) is routinely applied in mechanically ventilated patients to improve gas exchange and respiratory mechanics by increasing end-expiratory lung volume (EELV). In a recent experimental study in rats, we demonstrated that prolonged application of PEEP causes diaphragm remodeling, especially longitudinal muscle fiber atrophy. This is of potential clinical importance, as the acute withdrawal of PEEP during ventilator weaning decreases EELV and thereby stretches the adapted, longitudinally atrophied diaphragm fibers to excessive sarcomere lengths, having a detrimental effect on force generation. Whether this series of events occurs in the human diaphragm is unknown. In the current study, we investigated if short-term application of PEEP affects diaphragm geometry and function, which are prerequisites for the development of longitudinal atrophy with prolonged PEEP application. Nineteen healthy volunteers were noninvasively ventilated with PEEP levels of 2, 5, 10, and 15 cmH₂O. Magnetic resonance imaging was performed to investigate PEEP-induced changes in diaphragm geometry. Subjects were instrumented with nasogastric catheters to measure diaphragm neuromechanical efficiency (i.e., diaphragm pressure normalized to its electrical activity) during tidal breathing with different PEEP levels. We found that increasing PEEP from 2 to 15 cmH₂O resulted in a caudal diaphragm displacement (19 [14-26] mm, P < 0.001), muscle shortening in the zones of apposition (20.6% anterior and 32.7% posterior, P < 0.001), increase in diaphragm thickness (36.4% [0.9%-44.1%], P < 0.001) and reduction in neuromechanical efficiency (48% [37.6%-56.6%], P < 0.001). These findings demonstrate that conditions required to develop longitudinal atrophy in the human diaphragm are present with the application of PEEP.NEW & NOTEWORTHY We demonstrate that PEEP causes changes in diaphragm geometry, especially muscle shortening, and decreases in vivo diaphragm contractile function. Thus, prerequisites for the development of diaphragm longitudinal muscle atrophy are present with the acute application of PEEP. Once confirmed in ventilated critically ill patients, this could provide a new mechanism for ventilator-induced diaphragm dysfunction and ventilator weaning failure in the intensive care unit (ICU).

The neuromuscular and multisystem features of RYR1-related malignant hyperthermia and rhabdomyolysis: A study protocol

INTRODUCTION

Malignant hyperthermia (MH) and exertional rhabdomyolysis (ERM) have long been considered episodic phenotypes occurring in response to external triggers in otherwise healthy individuals with variants in RYR1. However, recent studies have demonstrated a clinical and histopathological continuum between patients with RYR1-related congenital myopathies and those with ERM or MH susceptibility. Furthermore, animal studies have shown non-neuromuscular features such as a mild bleeding disorder and an immunological gain-of-function associated with MH/ERM related RYR1 variants raising important questions for further research. Awareness of the neuromuscular disease spectrum and potential multisystem involvement in RYR1-related MH and ERM is essential to optimize the diagnostic work-up, improve counselling and and future treatment strategies for patients affected by these conditions. This study will examine in detail the nature and severity of continuous disease manifestations and their effect on daily life in patients with RYR1-related MH and ERM.

METHODS

The study protocol consists of four parts; an online questionnaire study, a clinical observational study, muscle imaging, and specific immunological studies. Patients with RYR1-related MH susceptibility and ERM will be included. The imaging, immunological and clinical studies will have a cross-sectional design, while the questionnaire study will be performed three times during a year to assess disease impact, daily living activities, fatigue and pain. The imaging study consists of muscle ultrasound and whole-body magnetic resonance imaging studies. For the immunological studies, peripheral mononuclear blood cells will be isolated for in vitro stimulation with toll-like receptor ligands, to examine the role of the immune system in the pathophysiology of RYR1-related MH and ERM.

DISCUSSION

This study will increase knowledge of the full spectrum of neuromuscular and multisystem features of RYR1-related MH and ERM and will establish a well-characterized baseline cohort for future studies on RYR1-related disorders. The results of this study are expected to improve recognition of RYR1-related symptoms, counselling and a more personalized approach to patients affected by these conditions. Furthermore, results will create new insights in the role of the immune system in the pathophysiology of MH and ERM.

TRIAL REGISTRATION

This study was pre-registered at ClinicalTrials.gov (ID: NCT04610619).

The effect of low- versus normal-pressure pneumoperitoneum during laparoscopic colorectal surgery on the early quality of recovery with perioperative care according to the enhanced recovery principles (RECOVER): study protocol for a randomized controlled study

BACKGROUND

There is increasing evidence for the use of lower insufflation pressures during laparoscopic surgery. Deep neuromuscular blockade allows for a safe reduction in intra-abdominal pressure without compromising the quality of the surgical field. While there is considerable evidence to support superior surgical conditions during deep neuromuscular blockade, there is only a limited amount of studies investigating patient outcomes. Moreover, results are not always consistent between studies and vary between different types of laparoscopic surgery. This study will investigate the effect of low-pressure pneumoperitoneum facilitated by deep NMB on quality of recovery after laparoscopic colorectal surgery.

METHODS

The RECOVER study is a multicenter double-blinded randomized controlled trial consisting of 204 patients who will be randomized in a 1:1 fashion to group A, low-pressure pneumoperitoneum (8 mmHg) facilitated by deep neuromuscular blockade (post tetanic count of 1-2), or group B, normal-pressure pneumoperitoneum (12 mmHg) with moderate neuromuscular blockade (train-of-four response of 1-2). The primary outcome is quality of recovery on postoperative day 1, quantified by the Quality of Recovery-40 questionnaire.

DISCUSSION

Few studies have investigated the effect of lower insufflation pressures facilitated by deep neuromuscular blockade on patient outcomes after laparoscopic colorectal procedures. This study will identify whether low pressure pneumoperitoneum and deep neuromuscular blockade will enhance recovery after colorectal laparoscopic surgery and, moreover, if this could be a valuable addition to the Enhanced Recovery After Surgery guidelines.

TRIAL REGISTRATION

EudraCT 2018-001485-42. Registered on April 9, 2018. Clinicaltrials.govNCT03608436. Registered on July 30, 2018.

Monitoring patient-ventilator breath contribution in the critically ill during neurally adjusted ventilatory assist: reliability and improved algorithms for bedside use

The patient-ventilator breath contribution (PVBC) index estimates the relative contribution of the patient to total tidal volume (Vt_insp) during mechanical ventilation in neurally adjusted ventilator assist mode and has been used to titrate ventilator support. The reliability of this index in ventilated patients is unknown and was investigated in this study. PVBC was calculated by comparing tidal volume (Vt_insp) and diaphragm electrical activity (EAdi) during assisted breaths (Vt_insp/EAdi)_assist and during unassisted breaths (Vt_insp/EAdi)_no-assist. Vt_insp was normalized to peak EAdi (EAdi_peak) using 1) one assisted breath, 2) five consecutive assisted breaths, or 3) five assisted breaths with matching EAdi preceding the unassisted breath (^N1PVBC², ^X5PVBC², and PX5VBCEAdi-matching2 , respectively). In addition, PVBC was calculated by comparing only Vt_insp for breaths with matching EAdi (PVBCβ²). Test-retest reliability of the different PVBC calculation methods was evaluated with the intraclass correlation coefficient (ICC) using five repeated PVBC maneuvers performed with a 1-min interval. In total, 125 PVBC maneuvers were analyzed in 25 patients. ICC [95% confidence interval] values were 0.46 [0.23-0.66], 0.51 [0.33-0.70], and 0.42 [0.14-0.69] for ^N1PVBC², ^X5PVBC², PX5VBCEAdi-matching2 , respectively. Complex waveform analyses showed that insufficient EAdi filtering by the ventilator software affects reliability of PVBC calculation. With our new EAdi-matching techniques reliability improved (PVBCβ² ICC: 0.78 [0.60-0.90]). We conclude that current techniques to calculate PVBC exhibit low reliability and that our newly developed criteria and estimation of PVBC-using Vt_insp of assisted breaths and unassisted breaths with matching EAdi-improves reliability. This may help implementation of PVBC in clinical practice. NEW & NOTEWORTHY The patient-ventilator breath contribution (PVBC) index estimates the relative contribution of the patient to tidal volume generated by the patient and the mechanical ventilator during mechanical ventilation in neurally adjusted ventilator assist mode. It could be used to titrate ventilator support and thus to limit development of diaphragm dysfunction in intensive care unit patients. Currently available methods for bedside assessment of PVBC are unreliable. Our newly developed criteria and estimation of PVBC largely improve reliability and help to quantify patient contribution to total inspiratory effort.

Spinal anesthesia-induced hypotension is caused by a decrease in stroke volume in elderly patients

Background

Hypotension is common during spinal anesthesia (SA) and is caused by a decrease in systemic vascular resistance (SVR) and/or cardiac output (CO). The effect of the dose of bupivacaine administered intrathecally on the changes in CO in elderly patients is largely unknown. This study investigated the hemodynamic effect of SA in elderly patients by studying the effect of two different dosages of intrathecal bupivacaine.

Methods

This prospective cohort study included 64 patients aged >65 years scheduled for procedures under SA; the patients received either 15 mg bupivacaine (the medium dose [MD] group) or 10 mg bupivacaine and 5 μg sufentanil (the low dose [LD] group). Blood pressure and CO were monitored throughout the procedure using Nexfin™, a noninvasive continuous monitoring device using a finger cuff.

Results

Thirty-three patients received MD and 31 received LD and there was no mean difference in baseline hemodynamics between the groups. On an average, the CO decreased 11.6% in the MD group and 10.0 % in the LD group. There was no significant change in SVR. Incidence of a clinically relevant decrease in stroke volume (SV) (>15% from baseline) was 67% in the MD and 45% in the LD groups (P<0.05).

Conclusion

CO and blood pressure decreased significantly after the onset of SA in elderly patients. This is mainly caused by a decrease in SV and not by a decrease in SVR. There was no difference in CO and blood pressure change between dosages of 10 or 15 mg bupivacaine.

Influence of a Tourniquet on Opioid Consumption After Local Infiltration Analgesia for Total Knee Arthroplasty

Objective

Local infiltration analgesia (LIA) with ropivacaine is increasingly used to provide postoperative analgesia after total knee arthroplasty (TKA). TKA may be performed with or without the use of a tourniquet. The absence of local blood flow when infiltrating local anaesthesia below an inflated tourniquet may affect the rate of systemic absorption, and this may have an effect on the duration and intensity of analgesia as compared with LIA without the use of a tourniquet. The aim of the present study was to investigate the influence of tourniquet use during surgery on the time to first request (TTFR) of opioids and opioid consumption.

Methods

Two historical time-based cohorts (one with and one without tourniquet during surgery) of 300 patients underwent primary TKA under spinal anaesthesia and received LIA to provide postoperative analgesia. The cohorts were compared for TTFR of opioids and opioid consumption.

Results

TTFR did not significantly differ between the tourniquet and non-tourniquet groups with a median (25^th-75^th percentile) of 240 (102-651) and 282 (100-720) min, respectively. The median (25^th-75^th percentile) oxycodone use was higher in the tourniquet group with 50 (20-90) versus 40 (10-77.5) mg (p=0.01).

Conclusion

There was no difference in the time to first opioid consumption, suggesting that the presence of an inflated tourniquet during local anaesthetic injection does not alter systemic absorption sufficiently to affect the duration of analgesia. However, the use of a tourniquet was associated with a higher opioid consumption, which is most likely caused by pain resulting from the tourniquet itself.

The influence of hypoxia on platelet function and plasmatic coagulation during systemic inflammation in humans in vivo

Systemic inflammation and hypoxia frequently occur simultaneously in critically ill patients, and are both associated with platelet activation and coagulopathy. However, human in vivo data on the effects of hypoxia on platelet function and plasmatic coagulation under systemic inflammatory conditions are lacking. In the present study, 20 healthy male volunteers were randomized to either 3.5 h of hypoxia (peripheral saturation 80-85%) or normoxia (room air), and systemic inflammation was elicited by intravenous administration of 2 ng/kg endotoxin. Various parameters of platelet function and plasmatic coagulation were determined serially. Endotoxemia resulted in increased circulating platelet-monocyte complexes and enhanced platelet reactivity, effects which were attenuated by hypoxia. Furthermore, endotoxin administration resulted in decreased plasma levels of platelet factor-4 levels and increased concentrations of von Willebrand factor. These endotoxemia-induced effects were not influenced by hypoxia. Neither endotoxemia nor hypoxia affected thrombin generation. In conclusion, our data reveal that hypoxia attenuates the endotoxemia-induced increases in platelet-monocyte formation and platelet reactivity, while leaving parameters of plasmatic coagulation unaffected.

Short-Term Hypoxia Dampens Inflammation in vivo via Enhanced Adenosine Release and Adenosine 2B Receptor Stimulation

Hypoxia and inflammation are closely intertwined phenomena. Critically ill patients often suffer from systemic inflammatory conditions and concurrently experience short-lived hypoxia. We evaluated the effects of short-term hypoxia on systemic inflammation, and show that it potently attenuates pro-inflammatory cytokine responses during murine endotoxemia. These effects are independent of hypoxia-inducible factors (HIFs), but involve augmented adenosine levels, in turn resulting in an adenosine 2B receptor-mediated post-transcriptional increase of interleukin (IL)-10 production. We translated our findings to humans using the experimental endotoxemia model, where short-term hypoxia resulted in enhanced plasma concentrations of adenosine, augmentation of endotoxin-induced circulating IL-10 levels, and concurrent attenuation of the pro-inflammatory cytokine response. Again, HIFs were shown not to be involved. Taken together, we demonstrate that short-term hypoxia dampens the systemic pro-inflammatory cytokine response through enhanced purinergic signaling in mice and men. These effects may contribute to outcome and provide leads for immunomodulatory treatment strategies for critically ill patients.

Anti-Müllerian hormone does not predict time to pregnancy: results of a prospective cohort study

In order to study whether ovarian reserve tests (ORTs) can predict time to ongoing pregnancy, we conducted a prospective cohort study in a cohort of healthy pregnancy planners. A total of 102 pregnancy planners were followed for 1 year, or until ongoing pregnancy occurred, after cessation of contraceptives). A baseline measurement of anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH) and antral follicle count (AFC) was conducted. At the end of follow-up, a semen analysis was performed and chlamydia antibody titres were assessed. A univariate prediction model demonstrated age and the AFC to be significantly capable of predicting time to pregnancy (hazard ratio 0.92, 95% CI 0.87-0.98, p = 0.01; 1.04, 95% CI 1.01-1.07, p = 0.02 respectively). In the multivariate model, however, correcting for female age, we found no predictive effect of AMH, basal FSH or the AFC for time to ongoing pregnancy (hazard ratios 1.43, 95% CI 0.84-2.46, p = 0.36; 0.96, 95% CI 0.86-1.06, p = 0.43; 1.03, 95% CI 1.00-1.07, p = 0.08, respectively). This was confirmed by the low C-statistic. We therefore concluded that baseline AMH, AFC or FSH levels do not predict time to ongoing pregnancy in a cohort of healthy pregnancy planners. These results limit the usability of these ORTs in the assessment of current fertility.

Deep neuromuscular blockade improves surgical conditions during low-pressure pneumoperitoneum laparoscopic donor nephrectomy

Background

Evidence indicates that low-pressure pneumoperitoneum (PNP) reduces postoperative pain and analgesic consumption. A lower insufflation pressure may hamper visibility and working space. The aim of the study is to investigate whether deep neuromuscular blockade (NMB) improves surgical conditions during low-pressure PNP.

Methods

This study was a blinded randomized controlled multicenter trial. 34 kidney donors scheduled for laparoscopic donor nephrectomy randomly received low-pressure PNP (6 mmHg) with either deep (PTC 1–5) or moderate NMB (TOF 0–1). In case of insufficient surgical conditions, the insufflation pressure was increased stepwise. Surgical conditions were rated by the Leiden-Surgical Rating Scale (L-SRS) ranging from 1 (extremely poor) to 5 (optimal).

Results

Mean surgical conditions were significantly better for patients allocated to a deep NMB (SRS 4.5 versus 4.0; p < 0.01). The final insufflation pressure was 7.7 mmHg in patients with deep NMB as compared to 9.1 mmHg with moderate NMB (p = 0.19). The cumulative opiate consumption during the first 48 h was significantly lower in patients receiving deep NMB, while postoperative pain scores were similar. In four patients allocated to a moderate NMB, a significant intraoperative complication occurred, and in two of these patients a conversion to an open procedure was required.

Conclusions

Our data show that deep NMB facilitates the use of low-pressure PNP during laparoscopic donor nephrectomy by improving the quality of the surgical field. The relatively high incidence of intraoperative complications indicates that the use of low pressure with moderate NMB may compromise safety during LDN. Clinicaltrials.gov identifier: NCT 02602964.

Effectiveness of deep versus moderate muscle relaxation during laparoscopic donor nephrectomy in enhancing postoperative recovery: study protocol for a randomized controlled study

BACKGROUND

Postoperative recovery after live donor nephrectomy is largely determined by the consequences of postoperative pain and analgesia consumptions. The use of deep neuromuscular blockade has been shown to reduce postoperative pain scores after laparoscopic surgery. In this study, we will investigate whether deep neuromuscular blockade also improves the early quality of recovery after live donor nephrectomy.

METHODS

The RELAX-study is a phase IV, multicenter, double-blinded, randomized controlled trial, in which 96 patients, scheduled for living donor nephrectomy, will be randomized into two groups: one with deep and one with moderate neuromuscular blockade. Deep neuromuscular blockade is defined as a post-tetanic count of 1-2. Our primary outcome measurement will be the Quality of Recovery-40 questionnaire (overall score) at 24 h after extubation.

DISCUSSION

This study is, to our knowledge, the first randomized study to assess the effectiveness of deep neuromuscular blockade during laparoscopic donor nephrectomy in enhancing postoperative recovery. The study findings may also be applicable for other laparoscopic procedures.

TRIAL REGISTRATION

clinicaltrials.gov, NCT02838134 . Registered on 29 June 2016.

[Are nail polish, artificial nails and piercings allowed outside the surgical area?Recommendations for the perioperative policy]

- An increasing number of patients wear nail polish, artificial nails or have piercings.- There is uncertainty about the perioperative management of these items, especially when located outside the surgical area.- In the majority of hospitals, patients are urged to remove these items preoperatively, under the assumption that they might cause problems.- Frequently, however, these items cannot be removed straightforwardly.- Nail polish and artificial nails only very rarely cause perioperative problems and therefore do not need to be removed pre-operatively.- The same applies to most piercings, except when located in or near the respiratory tract, if they have sharp endings or if they might cause problems as a result of the perioperative positioning of the patient.- Providing adequate information to the patient, knowledge about removal of these items and documentation of agreed arrangements are all important.- A national guideline concerning perioperative policy is urgently required.

Immunologic Consequences of Hypoxia during Critical Illness

Hypoxia and immunity are highly intertwined at clinical, cellular, and molecular levels. The prevention of tissue hypoxia and modulation of systemic inflammation are cornerstones of daily practice in the intensive care unit. Potentially, immunologic effects of hypoxia may contribute to outcome and represent possible therapeutic targets. Hypoxia and activation of downstream signaling pathways result in enhanced innate immune responses, aimed to augment pathogen clearance. On the other hand, hypoxia also exerts antiinflammatory and tissue-protective effects in lymphocytes and other tissues. Although human data on the net immunologic effects of hypoxia and pharmacologic modulation of downstream pathways are limited, preclinical data support the concept of tailoring the immune response through modulation of the oxygen status or pharmacologic modulation of hypoxia-signaling pathways in critically ill patients.

Correlation of bupivacaine 0.5% dose and conversion from spinal anesthesia to general anesthesia in cesarean sections

BACKGROUND

Failed spinal anesthesia for cesarean sections may require conversion to general anesthesia. The aim of this study was to determine whether the administered spinal bupivacaine dose for performing a cesarean section under spinal anesthesia was related to the conversion rate to general anesthesia.

METHODS

Retrospective analysis was performed on 1252 electronic data and file of patients who underwent a cesarean section under spinal anesthesia between 2004 and 2011.

RESULTS

In 15 patients, spinal anesthesia was converted into general anesthesia due to block failure. Patients in whom a bupivacaine dose of 8 mg or smaller was administered had significantly higher conversion rate (3/61 (4.9%) patients and 12/1191 (1.0%) patients, respectively; p < 0.05.). The relative risk of conversion with a 8 mg dose or lower is 4.88 (95% CI 1.41 - 16.85).

CONCLUSION

This retrospective study shows that a low dose administration a bupivacaine 0.5% for spinal anesthesia in cesarean section patients elicits significantly more frequent conversion to general anesthesia.

The in vitro mechanisms and in vivo efficacy of intravenous lidocaine on the neuroinflammatory response in acute and chronic pain

INTRODUCTION

The neuroinflammatory response plays a key role in several pain syndromes. Intravenous (iv) lidocaine is beneficial in acute and chronic pain. This review delineates the current literature concerning in vitro mechanisms and in vivo efficacy of iv lidocaine on the neuroinflammatory response in acute and chronic pain.

DATABASES AND DATA TREATMENT

We searched PUBMED and the Cochrane Library for in vitro and in vivo studies from July 1975 to August 2014. In vitro articles providing an explanation for the mechanisms of action of lidocaine on the neuroinflammatory response in pain were included. Animal or clinical studies were included concerning iv lidocaine for acute or chronic pain or during inflammation.

RESULTS

Eighty-eight articles regarding iv lidocaine were included: 36 in vitro studies evaluating the effect on ion channels and receptors; 31 animal studies concerning acute and chronic pain and inflammatory models; 21 clinical studies concerning acute and chronic pain. Low-dose lidocaine inhibits in vitro voltage-gated sodium channels, the glycinergic system, some potassium channels and Gαq-coupled protein receptors. Higher lidocaine concentrations block potassium and calcium channels, and NMDA receptors. Animal studies demonstrate lidocaine to have analgesic effects in acute and neuropathic pain syndromes and anti-inflammatory effects early in the inflammatory response. Clinical studies demonstrate lidocaine to have advantage in abdominal surgery and in some neuropathic pain syndromes.

CONCLUSIONS

Intravenous lidocaine has analgesic, anti-inflammatory and antihyperalgesic properties mediated by an inhibitory effect on ion channels and receptors. It attenuates the neuroinflammatory response in perioperative pain and chronic neuropathic pain.

Short-term hyperoxia does not exert immunologic effects during experimental murine and human endotoxemia

Oxygen therapy to maintain tissue oxygenation is one of the cornerstones of critical care. Therefore, hyperoxia is often encountered in critically ill patients. Epidemiologic studies have demonstrated that hyperoxia may affect outcome, although mechanisms are unclear. Immunologic effects might be involved, as hyperoxia was shown to attenuate inflammation and organ damage in preclinical models. However, it remains unclear whether these observations can be ascribed to direct immunosuppressive effects of hyperoxia or to preserved tissue oxygenation. In contrast to these putative anti-inflammatory effects, hyperoxia may elicit an inflammatory response and organ damage in itself, known as oxygen toxicity. Here, we demonstrate that, in the absence of systemic inflammation, short-term hyperoxia (100% O2 for 2.5 hours in mice and 3.5 hours in humans) does not result in increased levels of inflammatory cytokines in both mice and healthy volunteers. Furthermore, we show that, compared with room air, hyperoxia does not affect the systemic inflammatory response elicited by administration of bacterial endotoxin in mice and man. Finally, neutrophil phagocytosis and ROS generation are unaffected by short-term hyperoxia. Our results indicate that hyperoxia does not exert direct anti-inflammatory effects and temper expectations of using it as an immunomodulatory treatment strategy.

What is the evidence for the use of low-pressure pneumoperitoneum? A systematic review

Background

Laparoscopic surgery has several advantages when compared to open surgery, including faster postoperative recovery and lower pain scores. However, for laparoscopy, a pneumoperitoneum is required to create workspace between the abdominal wall and intraabdominal organs. Increased intraabdominal pressure may also have negative implications on cardiovascular, pulmonary, and intraabdominal organ functionings. To overcome these negative consequences, several trials have been performed comparing low- versus standard-pressure pneumoperitoneum.

Methods

A systematic review of all randomized controlled clinical trials and observational studies comparing low- versus standard-pressure pneumoperitoneum.

Results and conclusions

Quality assessment showed that the overall quality of evidence was moderate to low. Postoperative pain scores were reduced by the use of low-pressure pneumoperitoneum. With appropriate perioperative measures, the use of low-pressure pneumoperitoneum does not seem to have clinical advantages as compared to standard pressure on cardiac and pulmonary function. Although there are indications that low-pressure pneumoperitoneum is associated with less liver and kidney injury when compared to standard-pressure pneumoperitoneum, this does not seem to have clinical implications for healthy individuals. The influence of low-pressure pneumoperitoneum on adhesion formation, anastomosis healing, tumor metastasis, intraocular and intracerebral pressure, and thromboembolic complications remains uncertain, as no human clinical trials have been performed. The influence of pressure on surgical conditions and safety has not been established to date. In conclusion, the most important benefit of low-pressure pneumoperitoneum is lower postoperative pain scores, supported by a moderate quality of evidence. However, the quality of surgical conditions and safety of the use of low-pressure pneumoperitoneum need to be established, as are the values and preferences of physicians and patients regarding the potential benefits and risks. Therefore, the recommendation to use low-pressure pneumoperitoneum during laparoscopy is weak, and more studies are required.

Detection of a spontaneous pulse in photoplethysmograms during automated cardiopulmonary resuscitation in a porcine model

INTRODUCTION

Reliable, non-invasive detection of return of spontaneous circulation (ROSC) with minimal interruptions to chest compressions would be valuable for high-quality cardiopulmonary resuscitation (CPR). We investigated the potential of photoplethysmography (PPG) to detect the presence of a spontaneous pulse during automated CPR in an animal study.

METHODS

Twelve anesthetized pigs were instrumented to monitor circulatory and respiratory parameters. Here we present the simultaneously recorded PPG and arterial blood pressure (ABP) signals. Ventricular fibrillation was induced, followed by 20 min of automated CPR and subsequent defibrillation. After defibrillation, pediatric-guidelines-style life support was given in cycles of 2 min. PPG and ABP waveforms were recorded during all stages of the protocol. Raw PPG waveforms were acquired with a custom-built photoplethysmograph controlling a commercial reflectance pulse oximetry probe attached to the nose. ABP was measured in the aorta.

RESULTS

In nine animals ROSC was achieved. Throughout the protocol, PPG and ABP frequency content showed strong resemblance. We demonstrate that (1) the PPG waveform allows for the detection of a spontaneous pulse during ventilation pauses, and that (2) frequency analysis of the PPG waveform allows for the detection of a spontaneous pulse and the determination of the pulse rate, even during ongoing chest compressions, if the pulse and compression rates are sufficiently distinct.

CONCLUSIONS

These results demonstrate the potential of PPG as a non-invasive means to detect pulse presence or absence, as well as pulse rate during CPR.

Experimental neuropathy increases limbic forebrain CRF

Neuropathic pain is often accompanied by stress, anxiety and depression. Although there is evidence for involvement of corticotropin-releasing factor (CRF), the detailed neuronal basis of these pain-related mood alterations is unknown. This study shows that peripheral mononeuropathy was accompanied by changes in limbic forebrain CRF, but did not lead to changes in the functioning of the hypothalamo-pituitary-adrenal axis and the midbrain Edinger-Westphal centrally projecting (EWcp) neuron population, which play main roles in the organism's response to acute pain. Twenty-four days after chronic constriction injury (CCI) of the rat sciatic nerve, the oval bed nucleus of the stria terminalis (BSTov) contained substantially more Crf mRNA as did the central amygdala (CeA), which, in addition, possessed more CRF. In contrast, Crf mRNA and CRF contents of the hypothalamic paraventricular nucleus (PVN) were unaffected by CCI. Similarly, EWcp neurons, producing the CRF family member urocortin 1 (Ucn1) and constitutively activated by various stressors including acute pain, did not show an effect of CCI on Ucn1 mRNA or Ucn1. Also, the immediate early gene products cFos and deltaFosB in the EWcp were unaffected by CCI. These results indicate that neuropathic pain does not act via the HPA-axis or the EWcp, but includes a main role of Crf in the limbic system, which is in clear contrast to stressors like acute and chronic pain, which primarily act on the PVN and the EWcp.

Effects of vagus nerve stimulation and vagotomy on systemic and pulmonary inflammation in a two-hit model in rats

Pulmonary inflammation contributes to ventilator-induced lung injury. Sepsis-induced pulmonary inflammation (first hit) may be potentiated by mechanical ventilation (MV, second hit). Electrical stimulation of the vagus nerve has been shown to attenuate inflammation in various animal models through the cholinergic anti-inflammatory pathway. We determined the effects of vagotomy (VGX) and vagus nerve stimulation (VNS) on systemic and pulmonary inflammation in a two-hit model. Male Sprague-Dawley rats were i.v. administered lipopolysaccharide (LPS) and subsequently underwent VGX, VNS or a sham operation. 1 hour following LPS, MV with low (8 mL/kg) or moderate (15 mL/kg) tidal volumes was initiated, or animals were left breathing spontaneously (SP). After 4 hours of MV or SP, rats were sacrificed. Cytokine and blood gas analysis was performed. MV with 15, but not 8 mL/kg, potentiated the LPS-induced pulmonary pro-inflammatory cytokine response (TNF-α, IL-6, KC: p<0.05 compared to LPS-SP), but did not affect systemic inflammation or impair oxygenation. VGX enhanced the LPS-induced pulmonary, but not systemic pro-inflammatory cytokine response in spontaneously breathing, but not in MV animals (TNF-α, IL-6, KC: p<0.05 compared to SHAM), and resulted in decreased pO(2) (p<0.05 compared to sham-operated animals). VNS did not affect any of the studied parameters in both SP and MV animals. In conclusion, MV with moderate tidal volumes potentiates the pulmonary inflammatory response elicited by systemic LPS administration. No beneficial effects of vagus nerve stimulation performed following LPS administration were found. These results questions the clinical applicability of stimulation of the cholinergic anti-inflammatory pathway in systemically inflamed patients admitted to the ICU where MV is initiated.

Titin and diaphragm dysfunction in mechanically ventilated rats

Purpose

Diaphragm weakness induced by mechanical ventilation may contribute to difficult weaning from the ventilator. For optimal force generation the muscle proteins myosin and titin are indispensable. The present study investigated if myosin and titin loss or dysfunction are involved in mechanical ventilation-induced diaphragm weakness.

Methods

Male Wistar rats were either assigned to a control group (n = 10) or submitted to 18 h of mechanical ventilation (MV, n = 10). At the end of the experiment, diaphragm and soleus muscle were excised for functional and biochemical analysis.

Results

Maximal specific active force generation of muscle fibers isolated from the diaphragm of MV rats was lower than controls (128 ± 9 vs. 165 ± 13 mN/mm², p = 0.02) and was accompanied by a proportional reduction of myosin heavy chain concentration in these fibers. Passive force generation upon stretch was significantly reduced in diaphragm fibers from MV rats by ca. 35%. Yet, titin content was not significantly different between control and MV diaphragm. In vitro pre-incubation with phosphatase-1 decreased passive force generation upon stretch in diaphragm fibers from control, but not from MV rats. Mechanical ventilation did not affect active or passive force generation in the soleus muscle.

Conclusions

Mechanical ventilation leads to impaired diaphragm fiber active force-generating capacity and passive force generation upon stretch. Loss of myosin contributes to reduced active force generation, whereas reduced passive force generation is likely to result from a decreased phosphorylation status of titin. These impairments were not discernable in the soleus muscle of 18 h mechanically ventilated rats.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-012-2504-5) contains supplementary material, which is available to authorized users.

Anti-mullerian hormone predicts menopause: a long-term follow-up study in normoovulatory women

CONTEXT

It has been hypothesized that a fixed interval exists between age at natural sterility and age at menopause. Both events show considerable individual variability, with a range of 20 yr. Correct prediction of age at menopause could open avenues of individualized prevention of age-related infertility and other menopause-related conditions, like cardiovascular disease and breast carcinoma.

OBJECTIVE

The aim of this study was to explore the ability of ovarian reserve tests to predict age at menopause.

DESIGN AND SETTING

We conducted a long-term follow-up study at an academic hospital.

PARTICIPANTS

A total of 257 normoovulatory women (age, 21-46 yr) were derived from three cohorts with highly comparable selection criteria.

INTERVENTIONS

Anti-Müllerian hormone (AMH), antral follicle count, and FSH were assessed at time 1 (T1). At time 2 (T2), approximately 11 yr later, cycle status (strictly regular, menopausal transition, or postmenopause) and age at menopause were inventoried.

MAIN OUTCOME MEASURES

Accuracy of the ovarian reserve tests in predicting time to menopause was assessed by Cox regression, and a nomogram was constructed for the relationship between age-specific AMH concentrations at T1 and age at menopause.

RESULTS

A total of 48 (19%) women had reached postmenopause at T2. Age, AMH, and antral follicle count at T1 were significantly related with time to menopause (P < 0.001) and showed a good percentage of correct predictions (C-statistic, 0.87, 0.86, and 0.84, respectively). After adjusting for age, only AMH added to this prediction (C-statistic, 0.90). From the constructed nomogram, it appeared that the normal distribution of age at menopause will shift considerably, depending on the individual age-specific AMH level.

CONCLUSIONS

AMH is highly predictive for timing of menopause. Using age and AMH, the age range in which menopause will subsequently occur can be individually calculated.

α7 nicotinic acetylcholine receptor agonist GTS-21 attenuates ventilator-induced tumour necrosis factor-α production and lung injury

BACKGROUND

Mechanical ventilation (MV) induces an inflammatory response that can lead to lung injury. The vagus nerve can limit the inflammatory response through the cholinergic anti-inflammatory pathway. We evaluated the effects of stimulation of the cholinergic anti-inflammatory pathway with the selective partial α7 nicotinic acetylcholine receptor (α7nAChR) agonist GTS-21 on inflammation and lung injury induced by MV using clinically relevant ventilator settings. Furthermore, we investigated whether altering endogenous cholinergic signalling, by administration of the non-specific nAChR antagonist mecamylamine and the peripherally acting acetylcholinesterase inhibitor neostigmine, modulates the MV-induced inflammatory response.

METHODS

C57BL6 mice were injected i.p. with either the selective α7nAChR agonist GTS-21 (8 mg kg(-1)), the acetylcholinesterase inhibitor neostigmine (80 μg kg(-1)), the nAChR antagonist mecamylamine (1 mg kg(-1)), or a placebo; followed by 4 h of MV (8 ml kg(-1), 1.5 cm H(2)O PEEP).

RESULTS

MV resulted in release of cytokines in plasma and lungs compared with unventilated mice. Lung and plasma levels of tumour necrosis factor (TNF)-α, but not of interleukin-10, were lower in GTS-21-treated animals compared with placebo (P<0.05). In addition, GTS-21 lowered the alveolar-arterial gradient, indicating improved lung function (P=0.04). Neither neostigmine nor mecamylamine had an effect on MV-induced inflammation or lung function.

CONCLUSIONS

MV with clinically relevant ventilator settings results in pulmonary and systemic inflammation. Stimulation of the cholinergic anti-inflammatory pathway with GTS-21 attenuates MV-induced release of TNF-α, which was associated with reduced lung injury. Modulation of endogenous cholinergic signalling did not affect the MV-induced inflammatory response. Selective stimulation of the cholinergic anti-inflammatory pathway may represent new treatment options for MV-induced lung injury.

The relation between skin temperature increase and sensory block height in spinal anaesthesia using infrared thermography

BACKGROUND AND OBJECTIVES

To evaluate the feasibility of determining the extent of sympathetic blockade by skin temperature measurement with infrared thermography and relate the cranial extent of the temperature increase to that of the sensory block after spinal anaesthesia.

METHODS

Before and 5, 10 and 20 min after the administration of spinal anaesthesia, skin temperatures were measured with infrared thermography at the dermatomes T2-L3, in 12 male patients scheduled for lower limb surgery. The most cephalad dermatome at which sensory blockade occurred was related to the dermatome at which the largest temperature jump (corrected for baseline temperature) occurred.

RESULTS

The baseline temperatures showed considerable variation across the dermatomes, being lower below T12 than at the thoracic dermatomes. The mean difference between the level of the cephalad skin temperature elevation front (mean 1.03 °C, SD 0.8 °C) and cranial sensory block height was 0.10 dermatomes (SD 1.16), correlation coefficient (0.88, P<0.001).

CONCLUSION

The varying baseline temperatures across the trunk, the limited sympathetic block-induced increase in skin temperature at the trunk and the difficult control of influences from the surroundings partly obscured the extent of the skin temperature increase and its correlation to sensory block height. These factors have to be controlled to improve the use of infrared cameras as an easy bedside tool for predicting the cranial extent of (sympathetic blockade during) spinal anaesthesia.

Ultrasound-guided proximal and distal sciatic nerve blocks in children

STUDY OBJECTIVE

To present the use of ultrasonography for the performance of proximal subgluteal and distal sciatic nerve blocks in children.

DESIGN

Prospective descriptive study.

SETTING

University hospital.

PATIENTS

45 ASA physical status I, II, and III patients, aged between 8 months and 16 years, scheduled for lower limb surgery.

INTERVENTIONS

During general anesthesia, proximal, subgluteal, and distal sciatic nerve blocks using ultrasonography were performed. If severe postoperative pain was expected, a catheter technique was used.

MEASUREMENTS

The injected amount of local anesthetic was noted. Based on the spread of local anesthetic, prediction for successful block was made. Complications, adverse effects, postoperative pain scores, and parent satisfaction scores were noted.

MAIN RESULTS

21 proximal sciatic nerve blocks (12 single-injection and 9 continuous blocks) and 35 distal sciatic nerve blocks (17 single-injection, 6 bilateral single-injection, 4 continuous, and one bilateral continuous block) were performed. A mean initial dose of 0.25 mL.kg(-1) of ropivacaine 0.375% was injected. A successful block was obtained in all children. Excellent postoperative pain relief was obtained. All parents were satisfied with the postoperative pain relief. No complications occurred.

CONCLUSION

Ultrasonography is useful in the identification of the sciatic nerve and it facilitates needle and catheter placement for proximal and distal nerve blocks in children.

[Helicopter emergency medical service missions at night: 2 years of experience in the Dutch Regional Emergency Healthcare Network East]

OBJECTIVE

To study whether there are differences between day and night in the dispatch of helicopter emergency medical services (HEMS) and in their response and travelling times, medical treatment and transport of patients.

DESIGN

Retrospective, descriptive study.

METHOD

All data on helicopter emergency medical service (HEMS) missions available 24/7 from Nijmegen, the Netherlands, during 2007 and 2008 were collected. All missions in this period were divided into daytime and night-time missions. Next, the reason for dispatch, the duration of distinct times during the mission, the method of transport of the HEMS team, medical treatments and patient transport were compared.

RESULTS

In 2007 and 2008 the HEMS team was dispatched 2891 times. 1107 patients were treated during daytime and 479 during the night. The mean distance to the incident scene was longer for night missions. During night-time the HEMS team was dispatched more often for road traffic accidents and violence-related accidents but less often for falls, drowning, horse riding accidents and people becoming trapped (non-traffic-related). There were no differences in medical treatment given by the HEMS physician between day and night, but fewer patients were transported by helicopter at night. Travelling times and on-scene times were only slightly different.

CONCLUSION

The number of dispatches of the HEMS team at night was higher than expected, but night missions were cancelled more often due to weather conditions than missions by day. Prehospital times and operations of the Netherlands HEMS differed slightly between day and night.

Soft tissue landmark for ultrasound identification of the sciatic nerve in the infragluteal region: the tendon of the long head of the biceps femoris muscle

BACKGROUND AND OBJECTIVES

The sciatic nerve block represents one of the more difficult ultrasound-guided nerve blocks. Easy and reliable internal ultrasound landmarks would be helpful for localization of the sciatic nerve. Earlier, during ultrasound-guided posterior approaches to the infragluteal sciatic nerve, the authors recognized a hyperechoic structure at the medial border of the long head of biceps femoris muscle (BFL). The present study was performed to determine whether this is a potential internal landmark to identify the infragluteal sciatic nerve.

METHODS

The depth and the thickness of this hyperechoic structure, its relationship with the sciatic nerve and the ultrasound visibility of both were recorded in the proximal upper leg of 21 adult volunteers using a linear ultrasound probe in the range of 7-13 MHz. The findings were verified by an anatomical study in two cadavers.

RESULTS

The hyperechoic structure at the medial border of the BFL extended in a dorsoventral direction between 1.4+/-0.6 cm (mean+/-SD) and 2.8+/-0.8 cm deep from the surface, with a width of 2.2+/-0.9 mm. Between 2.6+/-0.9 and 10.0+/-1.5 cm distal to the subgluteal fold, the sciatic nerve was consistently identified directly at the ventral end of the hyperechoic structure in all volunteers. The anatomical study revealed that this hyperechoic structure corresponds to tendinous fibres inside and at the medial border of the BFL.

CONCLUSION

The hyperechoic BFL tendon might be a reliable soft tissue landmark for ultrasound localization of the infragluteal sciatic nerve.

Isoflurane attenuates pulmonary interleukin-1beta and systemic tumor necrosis factor-alpha following mechanical ventilation in healthy mice

BACKGROUND

Mechanical ventilation (MV) induces an inflammatory response in healthy lungs. The resulting pro-inflammatory state is a risk factor for ventilator-induced lung injury and peripheral organ dysfunction. Isoflurane is known to have protective immunological effects on different organ systems. We tested the hypothesis that the MV-induced inflammatory response in healthy lungs is reduced by isoflurane.

METHODS

Healthy C57BL6 mice (n=34) were mechanically ventilated (tidal volume, 8 ml/kg; positive end-expiratory pressure, 4 cmH(2)O; and fraction of inspired oxygen, 0.4) for 4 h under general anesthesia using a mix of ketamine, medetomidine and atropine (KMA). Animals were divided into four groups: (1) Unventilated control group; (2) MV group using KMA anesthesia; (3) MV group using KMA with 0.25 MAC isoflurane; (4) MV group using KMA with 0.75 MAC isoflurane. Cytokine levels were measured in lung homogenate and plasma. Leukocytes were counted in lung tissue.

RESULTS

Lung homogenates: MV increased pro-inflammatory cytokines. In mice receiving KMA+ isoflurane 0.75 MAC, no significant increase in interleukin (IL)-1beta was found compared with non-ventilated control mice. PLASMA: MV induced a systemic pro-inflammatory response. In mice anesthetized with KMA+ isoflurane (both 0.25 and 0.75 MAC), no significant increase in tumor necrosis factor (TNF)-alpha was found compared with non-ventilated control mice.

CONCLUSIONS

The present study is the first to show that isoflurane attenuates the pulmonary IL-1beta and systemic TNF-alpha response following MV in healthy mice.