Innovative Design and Development of Personalized Ankle-Foot Orthoses for Survivors of Stroke With Equinovarus Foot: Protocol for a Feasibility and Comparative Trial

BACKGROUND

Ankle-foot orthoses (AFOs) are vital in gait rehabilitation for patients with stroke. However, many conventional AFO designs may not offer the required precision for optimized patient outcomes. With the advent of 3D scanning and printing technology, there is potential for more individualized AFO solutions, aiming to enhance the rehabilitative process.

OBJECTIVE

This nonrandomized trial seeks to introduce and validate a novel system for AFO design tailored to patients with stroke. By leveraging the capabilities of 3D scanning and bespoke software solutions, the aim is to produce orthoses that might surpass conventional designs in terms of biomechanical effectiveness and patient satisfaction.

METHODS

A distinctive 3D scanner, complemented by specialized software, will be developed to accurately capture the biomechanical data of leg movements during gait in patients with stroke. The acquired data will subsequently guide the creation of patient-specific AFO designs. These personalized orthoses will be provided to participants, and their efficacy will be compared with traditional AFO models. The qualitative dimensions of this experience will be evaluated using the Quebec User Evaluation of Satisfaction With Assistive Technology (QUEST) assessment tool. Feedback from health care professionals and the participants will be considered throughout the trial to ensure a rounded understanding of the system's implications.

RESULTS

Spatial-temporal parameters will be statistically compared using paired t tests to determine significant differences between walking with the personalized orthosis, the existing orthosis, and barefoot conditions. Significant differences will be identified based on P values, with P<.05 indicating statistical significance. The Statistical Parametric Mapping method will be applied to graphically compare kinematic and kinetic data across the entire gait cycle. QUEST responses will undergo statistical analysis to evaluate patient satisfaction, with scores ranging from 1 (not satisfied) to 5 (very satisfied). Satisfaction scores will be presented as mean and SD values. Significant variations in satisfaction levels between the personalized and existing orthosis will be assessed using a Wilcoxon signed rank test. The anticipation is that the AFOs crafted through this innovative system will either match or outperform existing orthoses in use, with higher patient satisfaction rates.

CONCLUSIONS

Embracing the synergy of technology and biomechanics may hold the key to revolutionizing orthotic design, with the potential to set new standards in patient-centered orthotic solutions. However, as with all innovations, a balanced approach, considering both the technological possibilities and individual patient needs, will be paramount to achieving optimal outcomes.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/52365.

Differences between FEV6, FVC and VC at the diagnosis of obstructive ventilatory defect

INTRODUCTION

The diagnosis of airway obstruction can be made through FEV1/FVC ratio <0.7 or FEV1/VC ratio < lower limit of normality (LLN). Several authors advocate that FEV1/FEV6 ratio is an alternative to diagnosing obstructive ventilatory defect, while others have determined that the best cut-off for this ratio (best combined sensitivity and specificity) is 0.73.

OBJECTIVE

To evaluate the non-inferiority of FEV1/FEV6 ratio < 0.73 when compared to FEV1/FVC ratio < 0.7 and FEV1/VC < LLN in diagnosing airway obstruction.

METHODS

A retrospective analysis of the medical records from patients who underwent spirometry or plethysmography in a university central hospital from June 1st to December 31st, 2018 was carried out. Only medical records which included FEV1/FVC < 0.7 or FEV1/VC < LLN were selected, and these results were compared to FEV1/FEV6 ratio.

RESULTS

A total of 526 patients with obstructive ventilatory defect were identified by one of the two ratios described. Of these, 95.1%, 87.4% and 88.6% were obstructive by FEV1/FVC, FEV1/VC, and FEV1/FEV6 ratio, respectively. The positive predictive value (PPV) of FEV1/FEV6 in relation to FEV1/FVC ratio was 99.6% (p < 0.001) with a diagnostic efficacy of 92.8%, whereas the PPV of FEV1/FEV6 in relation to FEV1/VC was 91.0% (p < 0.001) and diagnostic efficacy was 85.2%. Most false negatives, comparing FEV6 with the other two tests, were found in patients with FEV1 > 70% (mild obstruction) and in individuals aged >50 years.

CONCLUSIONS

FEV1/FEV6 < 0.73 may be a good alternative ratio, as it is non-inferior to FEV1/VC and FEV1/FVC in diagnosing obstructive ventilatory defect.

Lessons learned from investigating patients' and physiotherapists' perspectives on the design of a telerehabilitation platform

PURPOSE

Home self-rehabilitation exercises for musculoskeletal conditions are a valuable complement to rehabilitation plans. Telerehabilitation systems using artificial intelligence can provide reliable solutions and empower patients by providing them with guidance and motivating them to engage in rehabilitation plans and activities. This study aims to understand the patient's and physiotherapist's perspective on the requirements of effective face-to-face physiotherapy sessions to inspire the design of a telerehabilitation platform to be used in home settings.

METHODS

The authors used an ethnography-informed approach through observation and semi-structured interviews with patients (n = 13) and physiotherapists (n = 10) in two outpatient rehabilitation clinics. The AEIOU framework was used to structure and analyse the observation. Thematic analysis was used to code and analyse the data collected from the observations and the interviews.

RESULTS

Patients' and physiotherapists' perspectives emphasise the need for exercise instruction clarity, evolution monitoring, and feedback. In the absence of the physiotherapist, in home settings, patients feel insecure and fear execution difficulties and limited exercise instructions, while physiotherapists struggle with controlling patients' home exercise performance. Telerehabilitation is seen as an opportunity to move further into home self-rehabilitation programs.

CONCLUSIONS

Besides home exercise monitoring and guidance, telerehabilitation platforms must allow personalization and effective communication between patients and physiotherapists.

Chronic stroke survivors' perspective on the use of serious games to motivate upper limb rehabilitation - a qualitative study

Upper limb paresis occurs quite commonly after stroke and may result in the affected limb's disuse or learned non-use. As a result, its cortical representation may be suppressed, further inhibiting its spontaneous utilization, resulting in motor function deterioration, increase in spasticity, joint stiffness and pain.The aim of this work was to involve stroke survivors in a qualitative study within a user centred design process to better understand the perspectives of stroke survivors on virtual reality - based serious games (SG) for upper limb rehabilitation during the chronic phase and use those insights to design a VR-based serious games which promotes activation of the affected cortical area.A qualitative research method was performed using a multi professional focus group discussion, including a representative group of stroke survivors.With the insights of this work, the authors initiated the design of a VR-based SG prototype for upper limb rehabilitation with two modes, one version to be played with any arm to pick a virtual hammer and hit targeted objects, and other version, a mirror version based on mirror therapy.

Immersive virtual reality for upper limb rehabilitation: comparing hand and controller interaction

Virtual reality shows great potential as an alternative to traditional therapies for motor rehabilitation given its ability to immerse the user in engaging scenarios that abstract them from medical facilities and tedious rehabilitation exercises. This paper presents a virtual reality application that includes three serious games and that was developed for motor rehabilitation. It uses a standalone headset and the user's hands without the need for any controller for interaction. Interacting with an immersive virtual reality environment using only natural hand gestures involves an interaction that is similar to that of real life, which would be especially desirable for patients with motor problems. A study involving 28 participants (4 with motor problems) was carried out to compare two types of interaction (hands vs. controllers). All of the participants completed the exercises. No significant differences were found in the number of attempts necessary to complete the games using the two types of interaction. The group that used controllers required less time to complete the exercise. The performance outcomes were independent of the gender and age of the participants. The subjective assessment of the participants with motor problems was not significantly different from the rest of the participants. With regard to the interaction type, the participants mostly preferred the interaction using their hands (78.5%). All four participants with motor problems preferred the hand interaction. These results suggest that the interaction with the user's hands together with standalone headsets could improve motivation, be well accepted by motor rehabilitation patients, and help to complete exercise therapy at home.

Serious Games for Stroke Telerehabilitation of Upper Limb - A Review for Future Research

Maintaining appropriate home rehabilitation programs after stroke, with proper adherence and remote monitoring is a challenging task. Virtual reality (VR) - based serious games could be a strategy used in telerehabilitation (TR) to engage patients in an enjoyable and therapeutic approach. The aim of this review was to analyze the background and quality of clinical research on this matter to guide future research. The review was based on research material obtained from PubMed and Cochrane up to April 2020 using the PRISMA approach. The use of VR serious games has shown evidence of efficacy on upper limb TR after stroke, but the evidence strength is still low due to a limited number of randomized controlled trials (RCT), a small number of participants involved, and heterogeneous samples. Although this is a promising strategy to complement conventional rehabilitation, further investigation is needed to strengthen the evidence of effectiveness and support the dissemination of the developed solutions.

Telehealth Opportunities in the COVID-19 Pandemic Early Days: What Happened, Did Not Happen, Should Have Happened, and Must Happen in the Near Future?

The objective of this communication is to offer a better understanding of the value of telemedicine in health care, particularly its role in creating opportunities for continuity of care to patients in a complex and novel setting as were the circumstances of the early COVID-19 pandemic times. Crisis time is also a time for opportunities. With regard to telehealth, all players (providers, staff, and patients) should be informed about its benefits and should also become familiar with the use of the various telehealth options and this will only be achieved through large information campaigns necessary enriched by local teaching and training programs in both public and private institutions. The final aim is to launch the debate and foster ideas useful throughout the pandemic. This article covers the experiences of physicians as well as health professionals in the Iberian Peninsula (Spain and Portugal), to provide a clearer idea of what has happened and how we can improve it with the possibilities provided by telemedicine, while at the same time to put in evidence that public health systems need to be rethought to provide solutions to situations such as that we are experiencing.

An Exploratory Study on the use of Virtual Reality in Balance Rehabilitation

Studies have shown the potential of Virtual Reality and motion tracking devices in physical rehabilitation. This paper addresses the topic of using non-immersive Virtual Reality therapeutic games with motion tracking in physical rehabilitation and describes an exploratory study performed in collaboration with a national public Rehabilitation Center about their use to motivate patients to perform exercises relevant for balance rehabilitation. The work involved developing and adapting mini-games to track patients posture; tests with patients recovering from Spinal Cord Injury suggest that this type of games can be helpful in the recovery process namely in patients' motivation for performing the therapeutic gestures.

Do we have today a reliable method to detect the moment of loss of consciousness during induction of general anaesthesia?

This review aims to give an overview of the current state of monitoring depth of anaesthesia and detecting the moment of loss of consciousness, from the first clinical signs involved in anaesthesia to the latest technologies used in this area. Such techniques are extremely important for the development of automatic systems for anaesthesia control, including preventing intraoperative awareness episodes and overdoses. A search in the databases Pubmed and IEEE Xplore was performed using terms such anaesthetic monitoring, depth of anaesthesia, loss of consciousness, as well as anaesthesia indexes, namely BIS. Despite the several methods capable of monitoring the hypnotic state of anaesthesia, there is still no methodology to accurate detect the moment of loss of consciousness during induction of general anaesthesia.

Using Virtual Reality to Increase Motivation in Poststroke Rehabilitation

Virtual reality (VR) applications meet fundamental principles of rehabilitation: intensity, task oriented training, biofeedback, environments rich in stimuli, and motivation, all pivotal factors for the success of rehabilitation programs. This paper describes the development process of a set of VR minigames developed to increase the motivation of stroke patients while performing repetitive upper limb movements.

STROKE34 Study Protocol: A Randomized Controlled Phase IIa Trial of Intra-Arterial CD34+ Cells in Acute Ischemic Stroke

Rationale/aim

Despite the increasing efficacy of recanalization therapies for acute ischemic stroke, a large number of patients are left with long-term functional impairment, devoid of efficacious treatments. CD34+ cells comprise a subset of bone marrow-derived mononuclear cells with the capacity to promote angiogenesis in ischemic lesions and have shown promising results in observational and in vitro studies. In this study, we aim to assess the efficacy of an autotransplant of CD34+ cells in acute ischemic stroke.

Sample size estimates

30 patients will be randomized for a power of 90% and alpha of 0.05 to detect a difference in 3 months infarct volume.

Methods and design

We will screen 18–80 years old patients with acute ischemic stroke due to occlusion of a middle cerebral artery (MCA) for randomization. Persistent arterial occlusions, contra-indications to magnetic resonance imaging (MRI), premorbid dependency, or other severe diseases will be excluded. Treatment will involve bone marrow aspiration, selection of CD34+ cells, and their administration intra-arterially in the symptomatic MCA by angiography. Patients will be randomized for treatment at 7 (±2) days, 20 (±5 days) or sham procedure, 10 in each group.

Study outcomes

The primary outcome will be infarct volume in MRI performed at 3 months. Secondary outcomes will include adverse events and multidimensional functional and neurological measures.

Discussion/conclusion

STROKE34 is a PROBE design phase IIa clinical trial to assess the efficacy of intra-arterial administration of CD34+ cells 7 and 20 days after acute ischemic stroke.

Trial registration (EU Clinical Trials Register)

2017-002456-88.

DSM-IH-R Psychotic Disorders: procedural validity of the Mini International Neuropsychiatric Interview (MINI). Concordance and causes for discordance with the CIDI

OBJECTIVES

the Mini International Neuropsychiatric Interview (MINI) is a short diagnostic structured interview (DSI) designed to generate positive diagnosis for the main Diagnostic and Statistical Manual (DSM)-III-R/IV Axis I disorders and to explore the symptoms of Criterion A for Schizophrenia (Sc) to rule out the presence of Psychotic Disorders. The procedural validity of the MINI was investigated in psychiatric patients using the Composite International Diagnostic Interview (CIDI) as a gold standard in Europe and the Structured Clinical Interview for DSM-III-R (SCID-P)in the US. This paper presents the concordance and the reasons for discordance between the MINI and the CIDI for DSM-III-R Psychotic and Mood Disorders. No study had systematically analysed the sources of disagreement between DSI based on the same operational criteria in psychotic patients.

METHODS

256 consecutively recruited psychiatric patients and 50 non-psychiatric subjects passed the MINI and the CIDI.

RESULTS

concordance was good for the presence of Major Depressive Episode (MDE), Manic Episode, Psychotic Disorders, syndromes or symptoms (0.65 to 0.82). Inconsistencies in evaluation of the disorder recency accounted for 25 to 40% of discordance for current diagnoses. Fifty-three percent of discordance for lifetime Manic Episode resulted from inconsistencies in the severity of the index episode. Fifty percent of discordance for the diagnosis of Psychotic Disorders was due to algorithmic differences between the two DSI.

CONCLUSION

the MINI yields reliable DSM-III-R diagnoses within a short time frame (22 minutes). Depending on the quantitative and the qualitative analyses of discrepancies between the MINI and the CIDI for Psychotic Disorders and Mood Episodes, we proposed and tested modifications leading to improvements in both interviews. The procedural validity of the modified MINI according to the modified CIDI was found to be very good.

Time resolved measurements by the pulse height analysis soft x-ray diagnostic on TCV

A single chord, single processing chain, hybrid (analog/digital) pulse height analysis diagnostic has been developed for the TCV tokamak, aiming to provide the evolution of the plasma electron temperature with a software selectable minimum temporal resolution of 100 ms. The high count rate (approximately 65 kHz) together with an energy resolution of 190 eV (at 5.9 keV) were achieved by encoding the data stream with an on-site developed interface amplifier and time generator. The diagnostic was also used to investigate the non-Maxwellian behavior of the electron energy distribution function with strong electron cyclotron resonance heating and to monitor the presence of intrinsic and injected impurities in the 700 eV-20 keV energy range. The conversion of this diagnostic into a real-time control tool is under development.

Radial basis function neural networks versus fuzzy models to predict return of consciousness after general anesthesia

This work presents two modelling techniques to predict return of consciousness (ROC) after general anaesthesia, considering the effect concentration of the anaesthetic drug at awakening. First, several clinical variables were statistically analysed to determine their correlation with the awakening concentration. The anaesthetic and the analgesic mean dose during surgery, and the age of the patient, proved to have significantly high correlation coefficients. Variables like the mean bispectral index value during surgery, duration of surgery did not present a statistical relation with ROC. Radial basis function (RBF) neural networks were trained relating different sets of clinical values with the anaesthetic drug effect concentration at awakening. Secondly, fuzzy models were built using an adaptive network-based fuzzy inference system (ANFIS) also relating different sets of variables. Clinical data was used to train and test the models. The fuzzy models and RBF neural networks proved to have good prediction properties and balanced results.

The effect of a remifentanil bolus on the bispectral index of the EEG (BIS) in anaesthetized patients independently from intubation and surgical stimuli

BACKGROUND AND OBJECTIVE

Remifentanil boluses are used in different clinical situations and the effects on bispectral index monitoring are unclear. We analysed the effect of a remifentanil bolus on the bispectral index of the electroencephalogram (bispectral index) under total intravenous anaesthesia with propofol and remifentanil.

METHODS

ASA I-III patients were included in this study. All patients received a 2 microg k g-1 remifentanil bolus in a period free from stimuli. Bispectral index and haemodynamic data were collected from an A-2000XP bispectral index monitor (every second) and an AS/3 Datex monitor (every 5 s). Bispectral index data were analysed using the area under the curve. Mean arterial pressure and heart rate were averaged at each 30-s period and analysed using analysis of variance.

RESULTS

A total of 240 bispectral index values were obtained per patient. The area under the curve between 90 and 120 s after the bolus was significantly lower than the basal area under the curve (average of all areas before the bolus, P < 0.05). Mean arterial pressure and heart rate were significantly reduced from 96.4 +/- 19.9 mmHg at the time of the bolus to 74.2 +/- 16.6 mmHg 120 s after, and from 70 +/- 16.4 bpm at the time of the bolus to 61 +/- 13.6 bpm after (P < 0.001), respectively.

CONCLUSIONS

There was a significant reduction in the areas under the curve between 90-120 s following the bolus. Heart rate and blood pressure also showed significant reductions. Thus, remifentanil bolus given under total intravenous anaesthesia with propofol and remifentanil decreases bispectral index, an effect independent of intubation and surgical stimuli.

Practical aspects of the use of target controlled infusion with remifentanil in neurosurgical patients: predicted cerebral concentrations at intubation, incision and extubation

Remifentanil has important side effects and it is not easy to know what remifentanil concentrations should be used during different endpoints of anaesthesia. We analyzed the remifentanil predicted effect-site concentrations (RemiCe) at different events during neurosurgical procedures and assessed if the concentrations used were clinically adequate. BIS and haemodynamic parameters were collected every 5 seconds. Predicted cerebral concentration of propofol (PropCe) and RemiCe were analyzed immediately prior to respective stimulus, and 30, 60 and 90 seconds after. RemiCe were 2.2 +/- 0.3, 6 +/- 2.6 and 2.2 +/- 0.9 ng ml(-1) at intubation, incision and extubation, respectively. PropCe observed in the same periods were 5 +/- 1, 2.6 +/- 0.9 and 1 +/- 0.3 microg ml(-1), also respectively. The remifentanil concentrations used in our patients were lower than reported concentrations, while being clinically adequate to minimize the haemodynamic response to stimulation.

[Hydroxyethyl starch 130/0.4 can be useful to prevent a hemodynamic response to a single dose of remifentanil]

Intravenous propofol and remifentanil are often used in anesthesia. The combined use of these drugs tends to cause hemodynamic depression. We describe the absence of hemodynamic effects in response to infusion of propofol and remifentanil when hydroxyethyl starch (HES) 130/0.4 was also administered. During induction, because blood volume needed to be replaced, two patients aged 62 and 65 years received intravenous HES 130/0.4. They then received a single dose of 2 microg x kg(-1) of remifentanil during total intravenous anesthesia (TIVA) with propofol and remifentanil before placement of a Mayfield head holder. No changes in mean blood pressure or heart rate were observed in either patient after the remifentanil bolus when they have received HES 130/0.4 during TIVA with propofol and remifentanil HES 130/0.4 may play an active role in preventing a hemodynamic response to remifentanil bolus. This hypothesis should be tested in a randomized controlled trial.

Effect of small changes in temperature on CA1 pyramidal cells from rat hippocampal slices during hypoxia: implications about the mechanism of hypothermic protection against neuronal damage

Small reductions in temperature have been shown to improve neurologic recovery after ischemia. We have examined the effect of temperature on biochemical and physiological changes during hypoxia using rat hippocampal slices as a model system. The postsynaptic population spike recorded from the CA1 pyramidal cell region of slices subjected to 7 min of hypoxia with hypothermia (34 degrees C) recovered to 73% of its prehypoxic level; slices subjected to the same period of hypoxia at 37 degrees C did not recover. After 7 min of hypoxia ATP fell to 48% of its prehypoxic concentration at 34 degrees C and 30% at 37 degrees C. Potassium fell to 86% during 7 min of hypoxia with hypothermia, this compares to a fall to 58% at 37 degrees C. The increase in sodium after 7 min of hypoxia was also attenuated by hypothermia (133% vs. 163% of its prehypoxic concentration). When the hypoxic period was shortened to 3 min (37 degrees C) the population spike recovered to 94%. If the temperature was increased to 40 degrees C there was only 7% recovery of the population spike after 3 min of hypoxia. With hyperthermia (40 degrees C), ATP fell to 33% after 3 min of hypoxia, this compares to 81% at normothermia. Potassium fell to 76% after 3 min of hypoxia with hyperthermia, this compares to 91% at 37 degrees C. Sodium concentrations increased with hyperthermia before hypoxia, at 3 min of hypoxia there was no significant difference between the hyperthermic and normothermic tissue; there was a large increase in sodium with hyperthermia after 5 min of hypoxia (209% vs. 146%). We conclude that the improved recovery after hypothermic hypoxia is at least in part due to the attenuated changes in ATP, potassium and sodium during hypoxia and that the worsened recovery with hyperthermia is due to an exacerbation of the change in ATP, potassium and sodium concentrations during hypoxia.

Nitrous oxide in neuroanaesthesia: an appraisal

A handful of recent publications have brought relevant contributions to the ongoing debate over the use of nitrous oxide in neuroanaesthesia. The present article reviews these publications. The question of whether nitrous oxide can be safely used in patients with reduced cerebral compliance and the relationship between hypocapnic vasoconstriction and nitrous oxide are discussed. The implications of the use of nitrous oxide during evoked potentials recording (motor evoked potentials and somatosensory evoked potentials) are discussed. The possible harmful effect of nitrous oxide in cerebral ischaemia is debated.

The Mini-International Neuropsychiatric Interview (M.I.N.I.): the development and validation of a structured diagnostic psychiatric interview for DSM-IV and ICD-10

The Mini-International Neuropsychiatric Interview (M.I.N.I.) is a short structured diagnostic interview, developed jointly by psychiatrists and clinicians in the United States and Europe, for DSM-IV and ICD-10 psychiatric disorders. With an administration time of approximately 15 minutes, it was designed to meet the need for a short but accurate structured psychiatric interview for multicenter clinical trials and epidemiology studies and to be used as a first step in outcome tracking in nonresearch clinical settings. The authors describe the development of the M.I.N.I. and its family of interviews: the M.I.N.I.-Screen, the M.I.N.I.-Plus, and the M.I.N.I.-Kid. They report on validation of the M.I.N.I. in relation to the Structured Clinical Interview for DSM-III-R, Patient Version, the Composite International Diagnostic Interview, and expert professional opinion, and they comment on potential applications for this interview.

Nitrous oxide impairs electrophysiologic recovery after severe hypoxia in rat hippocampal slices

BACKGROUND

Research has suggested that nitrous oxide may be harmful to ischemic neurons; however, the evidence for this is equivocal. The authors used rat hippocampal slices to examine the effects of nitrous oxide on neuronal hypoxic damage.

METHODS

The evoked population spike (PS) was recorded from hippocampal CA1 pyramidal cells before, during, and after hypoxia. Control groups received nitrogen concentrations equal to nitrous oxide throughout the experiments. Biochemical measurements were made from dissected CA1 regions under experimental conditions that matched the electrophysiology studies.

RESULTS

Recovery of the PS after hypoxia was 18 +/- 7% in slices treated with 50% nitrous oxide before and during 3.5 min of hypoxia; this compares with 41 +/- 9% (P < 0.05) in nitrogen-treated slices. Slices treated with nitrous oxide (95%) only during hypoxia (6 min) also demonstrated significantly less recovery of the PS than did slices treated with nitrogen. There was no significant difference in recovery if nitrous oxide was discontinued after the hypoxic period. Adenosine triphosphate concentrations after 3.5 min of hypoxia in slices treated with nitrous oxide decreased to the same extent as in nitrogen-treated slices (47% vs. 50%). Calcium influx increased during 10 min of hypoxia in untreated slices, but nitrous oxide did not significantly increase calcium influx during hypoxia. The sodium concentrations increased and potassium concentrations decreased during hypoxia; nitrous oxide did not significantly alter these changes.

CONCLUSIONS

Nitrous oxide impaired electrophysiologic recovery of hippocampal slices after severe hypoxia. Nitrous oxide did not cause significant changes in the biochemical parameters examined.

The effect of isoflurane on biochemical changes during and electrophysiological recovery after anoxia in rat hippocampal slices

It is unclear whether isoflurane protects against neuronal damage. This study examines the extent and mechanism by which isoflurane might affect anoxic neuronal damage. The size of the evoked postsynaptic population spike recorded from the CA 1 pyramidal cell layer of the rat hippocampal slice 60 min after anoxia was compared with its preanoxic, preisoflurane level. Intracellular adenosine triphosphate (ATP), sodium, and potassium levels were measured in the dentate and CA 1 regions at the end of the anoxic period in similarly treated slices. Isoflurane increased the latency and reduced the amplitude of the evoked response before anoxia. Isoflurane (2%) did not significantly improve recovery of the evoked response after 5 min of anoxia (untreated slices = 6 +/- 2% (mean +/- SEM), isoflurane = 17 +/- 7%); 1.5% isoflurane also did not significantly improve recovery after 4 min of anoxia (untreated = 30 +/- 8% vs. 1.5% isoflurane = 47 +/- 12%). Isoflurane did not significantly attenuate the decrease in ATP levels in either the dentate or CA 1 regions of the hippocampal slice during 4 or 7 min of anoxia; however, there was a significant improvement in ATP levels after 10 min of anoxia in both regions of isoflurane-treated preparations (1.0 +/- 0.1 vs. 1.4 +/- 0.1, CA 1; 1.3 +/- 0.1 vs. 2.0 +/- 0.2 nM/mg dry weight, dentate). Sodium concentrations increased and potassium concentrations decreased during anoxia. Isoflurane did not significantly attenuate the changes in these ions during anoxia. In conclusion, isoflurane does not significantly improve recovery of CA 1 pyramidal cells during anoxia nor does it attenuate the anoxic changes in ATP, sodium, and potassium after 4 or 7 min of anoxia. With a more prolonged period of anoxia (10 min) isoflurane reduces the decrease in ATP levels.

Propofol reduces neuronal transmission damage and attenuates the changes in calcium, potassium, and sodium during hyperthermic anoxia in the rat hippocampal slice

BACKGROUND

Propofol reduces cerebral blood flow, cerebral metabolic rate for oxygen, and intracranial pressure and is being increasingly used in neuroanesthesia. In vivo studies have yielded conflicting results on its ability to protect against ischemic brain damage. In the current study, an in vitro model was used to examine the mechanism of propofol's action on anoxic neuronal transmission damage.

METHODS

A presynaptic pathway was stimulated in the rat hippocampal slice to elicit a postsynaptic population spike in the CA1 region. The effects of propofol (20 micrograms/ml), its solvent intralipid or no drug, on the population spike before, during, and 60 min after anoxia at 37 degrees C or 39 degrees C were examined. Intracellular adenosine triphosphate (ATP), Na, and K were measured in dissected CA1 regions at 37 degrees C and 39 degrees C after 5 min of anoxia; 45Ca influx was measured after 10 min of anoxia.

RESULTS

Propofol did not improve recovery after 5, 6, or 7 min of anoxia at 37 degrees C. Recovery of the population spike after 6 min of anoxia at 37 degrees C was 62 +/- 11% with propofol, 35 +/- 15% with intralipid, and 44 +/- 10% in untreated tissue (NS). After 5 min of anoxia at 39 degrees C, there was significantly better recovery of the population spike with propofol (76 +/- 12%) than with intralipid (11 +/- 6%) or no drug (13; +/- 5%). Propofol, but not intralipid, reduced the population spike amplitude before anoxia. At 37 degrees C, anoxia caused significant changes in ATP (62% of normoxic concentration), Ca (115%), Na (138%), and K (68%). Both propofol and intralipid significantly attenuated the changes in ATP (78% and 82% of normoxic concentration) and Ca (104% and 103%). Na changes were attenuated by propofol (95%) but not intralipid; K concentration was not affected by either drug. At 39 degrees C, for most parameters, anoxia caused more marked changes: ATP was 23% of normoxic concentration, Ca 116%, Na 185%, and K 48%. Both propofol and intralipid attenuated the decrease in ATP (56% of normoxic); propofol, but not intralipid, significantly attenuated the changes in Ca (100%), Na (141%), and K (63%).

CONCLUSIONS

Propofol improved electrophysiologic recovery from anoxia during hyperthermia but not normothermia. At 37 degrees C propofol attenuated the changes in ATP, Na, and Ca, however, this did not result in improved recovery. At 39 degrees C the changes in ATP, Na, and K caused by anoxia were greater than at 37 degrees C; this could explain why electrophysiologic damage was worsened. Improved recovery with propofol at 39 degrees C may be explained by its attenuation of the changes in Ca, Na, and K at this temperature. The decrease in ATP was attenuated by both propofol and intralipid and therefore cannot explain the improved recovery.

The importance of sodium for anoxic transmission damage in rat hippocampal slices: mechanisms of protection by lidocaine

1. The effect of sodium influx on anoxic damage was investigated in rat hippocampal slices. Previous experiments demonstrated that a concentration of tetrodotoxin which blocks neuronal transmission protects against anoxic damage. In this study we examined low concentrations of lidocaine (lignocaine; which do not block neuronal transmission), for their effect on recovery of the evoked population spike recorded from the CA1 pyramidal cell layer. 2. Recovery of the population spike, measured 60 min after a 5 min anoxic period, was 4 +/- 2% of its preanoxic, predrug level. Lidocaine concentrations of 10, 50, and 100 microM significantly improved recovery to 56 +/- 12, 80 +/- 7 and 70 +/- 14%, respectively. 3. Lidocaine (10 microM) did not alter the size of the evoked response before anoxia and had no significant effect on potassium levels or calcium influx during anoxia. It did, however, reduce cellular sodium levels (146 +/- 7 vs. 202 +/- 12 nmol mg-1) and preserve ATP levels (2.17 +/- 0.07 vs. 1.78 +/- 0.07 nmol mg-1) during anoxia. All values were measured at the end of 5 min of anoxia except those for Ca2+ influx which were measured during 10 min of anoxia. 4. High concentrations of lidocaine (100 microM) did not improve recovery significantly over that observed with 10 microM. They also had no significantly greater effects on sodium levels than 10 microM lidocaine (137 +/- 12 vs. 146 +/- 7 nmol mg-1); however, 100 microM lidocaine significantly improved potassium (202 +/- 18 vs. 145 +/- 6 nmol mg-1) and ATP (2.57 +/- 0.06 vs. 2.17 +/- 0.07 nmol mg-1) levels, while reducing calcium influx (7.76 +/- 0.12 vs. 9.24 +/- 0.39 nmol mg-1 (10 min)-1) when compared with 10 microM lidocaine. 5. We conclude that sodium influx and ATP depletion are of major importance in anoxic damage since 10 microM lidocaine reduced these changes during anoxia and improved recovery of the population spike. In addition, our results indicate that the properties of the sodium channel are altered during anoxia, since sodium influx is blocked by a concentration of lidocaine that does not affect the population spike in the preanoxic period.

Anoxia reduces depolarization induced calcium uptake in the rat hippocampal slice

Veratridine-induced depolarization caused a large increase in Ca uptake in the rat hippocampal slice (30.2 vs. 9.0 nM/mg dry weight). This uptake was reduced to 18.4 nM/mg when veratridine was combined with anoxia. When compared with veratridine exposure alone, the combination of anoxia and veratridine increased intracellular Na (460 vs. 380 microM/g), decreased intracellular K (30 vs. 40 microM/g) and decreased ATP levels (0.1 vs. 0.8 nM/mg). The changes in Na, K, and ATP should enhance net Ca uptake, yet Ca uptake was reduced. This suggests an effect of anoxia to block Ca channels. In summary anoxia attenuates depolarization-induced Ca uptake. This may represent a mechanism by which neurons are partially protected against anoxic damage which could be more severe if depolarization-induced Ca uptake was not limited.