In a porcine model of implantable pacemakers for pediatric unilateral diaphragm paralysis, the phrenic nerve is the best target

BACKGROUND

A frequent complication of Fontan operations is unilateral diaphragmatic paresis, which leads to hemodynamic deterioration of the Fontan circulation. A potential new therapeutic option is the unilateral diaphragmatic pacemaker. In this study, we investigated the most effective stimulation location for a potential fully implantable system in a porcine model.

METHODS

Five pigs (20.8 ± 0.95 kg) underwent implantation of a customized cuff electrode placed around the right phrenic nerve. A bipolar myocardial pacing electrode was sutured adjacent to the motor point and peripherally at the costophrenic angle (peripheral diaphragmatic muscle). The electrodes were stimulated 30 times per minute with a pulse duration of 200 µs and a stimulation time of 300 ms. Current intensity was the only variable changed during the experiment.

RESULTS

Effective stimulation occurred at 0.26 ± 0.024 mA at the phrenic nerve and 7 ± 1.22 mA at the motor point, a significant difference in amperage (p = 0.005). Even with a maximum stimulation of 10 mA at the peripheral diaphragm muscle, however, no effective stimulation was observed.

CONCLUSION

The phrenic nerve seems to be the best location for direct stimulation by a unilateral thoracic diaphragm pacemaker in terms of the required amperage level in a porcine model.

Laparoscopic Electromyography and Electrostimulation of the Gastrointestinal Tract Before Placement of Theranostic Devices

NEED

Electrical stimulation (ES) is a promising therapy for multisegmental gastrointestinal (GI) motility disorders such as gastroparesis with slow-transit constipation or chronic intestinal pseudo-obstruction. Wireless communicating GI devices for smart sensing and ES-based motility modulation will soon be available. Before placement, a potential benefit for each GI segment must be intraoperatively assessed.

TECHNICAL SOLUTION

A minimally invasive multisegmental electromyography (EMG) analysis with ES of the GI tract is required.

PROOF OF CONCEPT

Two porcine experiments were performed with a laparoscopic setup. Multiple hook-needle electrodes were subserosally applied in the stomach, duodenum, jejunum, ileum, and colon. EMG signals were acquired for computer-assisted motility analysis. Gastric ES, duodenal ES, jejunal ES, ileal ES, and colonic ES were applied.

NEXT STEPS

Further technological and rapid regulatory solutions are desired to initialize a clinical trial of the next generation devices in the near future.

CONCLUSION

We demonstrate a laparoscopic strategy with EMG analysis and ES of multiple GI segments. Thus, GI function may be evaluated before theranostic devices are placed. Extended GI resection or organ transplantation may be delayed or even avoided in affected patients.

A porcine model of postoperative hemi-diaphragmatic paresis to evaluate a unilateral diaphragmatic pacemaker

Unilateral phrenic nerve damage is a dreaded complication in congenital heart surgery. It has deleterious effects in neonates and children with uni-ventricular circulation. Diaphragmatic palsy, caused by phrenic nerve damage, impairs respiratory function, especially in new-borns, because their respiration depends on diaphragmatic contractions. Furthermore, Fontan patients with passive pulmonary perfusion are seriously affected by phrenic nerve injury, because diaphragmatic contraction augments pulmonary blood flow. Diaphragmatic plication is currently employed to ameliorate the negative effects of diaphragmatic palsy on pulmonary perfusion and respiratory mechanics. This procedure attenuates pulmonary compression by the abdominal contents. However, there is no contraction of the plicated diaphragm and consequently no contribution to the pulmonary blood flow. Hence, we developed a porcine model of unilateral diaphragmatic palsy in order to evaluate a diaphragmatic pacemaker. Our illustrated step-by-step description of the model generation enables others to replicate and use our model for future studies. Thereby, it might contribute to investigation and advancement of potential improvements for these patients.

Proof of concept of an accelerometer as a trigger for unilateral diaphragmatic pacing: a porcine model

BACKGROUND

Unilateral diaphragmatic paralysis in patients with univentricular heart is a known complication after pediatric cardiac surgery. Because diaphragmatic excursion has a significant influence on perfusion of the pulmonary arteries and hemodynamics in these patients, unilateral loss of function leads to multiple complications. The current treatment of choice, diaphragmatic plication, does not lead to a full return of function. A unilateral diaphragmatic pacemaker has shown potential as a new treatment option. In this study, we investigated an accelerometer as a trigger for a unilateral diaphragm pacemaker (closed-loop system).

METHODS

Seven pigs (mean weight 20.7 ± 2.25 kg) each were implanted with a customized accelerometer on the right diaphragmatic dome. Accelerometer recordings (mV) of the diaphragmatic excursion of the right diaphragm were compared with findings using established methods (fluoroscopy [mm]; ultrasound, M-mode [cm]). For detection of the amplitude of diaphragmatic excursions, the diaphragm was stimulated with increasing amperage by a cuff electrode implanted around the right phrenic nerve.

RESULTS

Results with the different techniques for measuring diaphragmatic excursions showed correlations between accelerometer and fluoroscopy values (correlation coefficient 0.800, P < 0.001), accelerometer and ultrasound values (0.883, P < 0.001), and fluoroscopy and ultrasound values (0.816, P < 0.001).

CONCLUSION

The accelerometer is a valid method for detecting diaphragmatic excursion and can be used as a trigger for a unilateral diaphragmatic pacemaker.

Real-time classification of hand movements as a basis for intuitive control of grasp neuroprostheses

This paper reports on the evaluation of recurrent and convolutional neural networks as real-time grasp phase classifiers for future control of neuroprostheses for people with high spinal cord injury. A field-programmable gate array has been chosen as an implementation platform due to its form factor and ability to perform parallel computations, which are specific for the selected neural networks. Three different phases of two grasp patterns and the additional open hand pattern were predicted by means of surface Electromyography (EMG) signals (i.e. Seven classes in total). Across seven healthy subjects, CNN (Convolutional Neural Networks) and RNN (Recurrent Neural Networks) had a mean accuracy of 85.23% with a standard deviation of 4.77% and 112 µs per prediction and 83.30% with a standard deviation of 4.36% and 40 µs per prediction, respectively.

Technical, Medical and Ethical Challenges in Networks of Smart Active Implants

Networks of distributed interactive micro-implants could enhance the treatment of otoneurological conditions such as tinnitus or restore impaired complex physiological/ motor functions such as gastrointestinal motility or grasping. For this, an electrical stimulation of neural and muscular tissue is a key prerequisite. Challenges in the development of such interactive micro-implants are the complex human-machine interface, the wireless power supply, and the long-term stability of implants as well as secure and safe signal transmission. This paper addresses all these topics as well as the ethical, legal and social implications of smart implant networks in general. First achievements of the German innovation cluster INTAKT will be presented.

Five-fold Gastrointestinal Electrical Stimulation With Electromyography-based Activity Analysis: Towards Multilocular Theranostic Intestinal Implants

Background/Aims

Motility disorders are common and may affect the entire gastrointestinal (GI) tract but current treatment is limited. Multilocular sensing of GI electrical activity and variable electrical stimulation (ES) is a promising option. The aim of our study is to investigate the effects of adjustable ES on poststimulatory spike activities in 5 GI segments.

Methods

Six acute porcine experiments were performed with direct ES by 4 ES parameter sets (30 seconds, 25 mA, 500 microseconds or 1000 microseconds, 30 Hz or 130 Hz) applied through subserosal electrodes in the stomach, duodenum, ileum, jejunum, and colon. Multi-channel electromyography of baseline and post-stimulatory GI electrical activity were recorded for 3 minutes with hook needle and hook-wire electrodes. Spike activities were algorithmically calculated, visualized in a heat map, and tested for significance by Poisson analysis.

Results

Post-stimulatory spike activities were markedly increased in the stomach (7 of 24 test results), duodenum (8 of 24), jejunum (23 of 24), ileum (18 of 24), and colon (5 of 24). ES parameter analysis revealed that 80.0% of the GI parts (all but duodenum) required a pulse width of 1000 microseconds, and 60.0% (all but jejunum and colon) required 130 Hz frequency for maximum spike activity. Five reaction patterns were distinguished, with 30.0% earlier responses (type I), 42.5% later or mixed type responses (type II, III, and X), and 27.5% non-significant responses (type 0).

Conclusions

Multilocular ES with variable ES parameters is feasible and may significantly modulate GI electrical activity. Automated electromyography analysis revealed complex reaction patterns in the 5 examined GI segments.

Motility analysis by means of video tracked markers

The motility of the gastrointestinal tract is crucial for digestive activity and dysfunction can lead to severe disease pattern. A method for analysing the motility is needed when treatment approaches shall be evaluated. Therefore markers attached to different locations on the stomach and the bowel of pigs are video tracked in this research study. The markers are designed to provide a high contrast and have an adhesive side for fixation. Above the operation field a video camera has been placed to film the markers during the procedure. To analyse the video data a special algorithm has been implemented. The algorithm requires a registration process at the beginning of each recording which allows the parallel tracking of multiple markers. After the registration the algorithm tracks the position of the marker frame by frame. Each frame is converted into a greyscale picture by adding specified colour values of each pixel. This allows emphasizing certain colours. The centre of the marker is determined by computing the horizontal and vertical centre of the marker starting at the corresponding marker position of the previous frame. After completion the data is stored as coordinates and a video with the marker position displayed for further processing. For advanced analysis the data can be synchronized with electromyography signals, for example. The marked videos show a promising tracking of the markers. However, if the algorithm loses track of a marker during a recording, it is unlikely to relocate it due to the successive processing of the frames. Nevertheless this method provides a simple and easy to use solution for movement detection of the gastrointestinal tract.

Electrical stimulation with motility analysis of five parts of the gastrointestinal tract

Gastrointestinal (GI) motility disorders are frequent and clinically significant conditions with impairment of patient’s quality of life. Examples range from upper GI symptoms such as dysphagia and gastroparesis to lower GI manifestations, namely chronic-intestinal pseudo obstruction, diarrhea and constipation. Furthermore, postoperative motility disorders are common. Currently, available pharmacological or dietetic treatment options are limited. Since GI motility is based on myoelectric activity, electrical stimulation (ES) is a promising alternative. Numerous studies have demonstrated suitable pacing strategies and parameters in different GI segments. However, results of multilocular ES are rare. We report the first experimental study to evaluate ES of five GI parts in a porcine model. Multi-channel electromyography (EMG) recordings of gastrointestinal baseline and poststimulatory electrical activity were realized together with video-based marker tracking (VBMT). ES provoked visible GI contractions and appeared to modulate frequencies of slow waves and spikes. Further investigations are needed for analysis of locoregional and cross-organ effects of ES on the GI tract.

Multifunctional surface probe for less invasive stimulation of sacral somatic and autonomic outflow under EMG feedback control

Invasive electric stimulation of sacral somatic and autonomic outflow is used for treatment of urinary and anorectal functional disturbances and selective monitoring of the autonomic nerve-sparing technique in pelvic surgery, the so called pelvic intraoperative neuromonitoring. The aim of this experimental study was to investigate a less invasive approach for simultaneous stimulation of sacral somatic and autonomic outflow and concomitant recording of feedback.

A newly developed multifunctional surface probe for simultaneous transrectal stimulation and electromyography (EMG) of external (EAS) and internal anal sphincter (IAS) was investigated in a consecutive series of six male pigs. The probe (cathode) was designed for intra-anal/-rectal application. An additional surface anode was placed on the animals´ back at the level of the sacrum. Each animal underwent autonomic nerve-sparing low anterior rectal resection. The transrectal stimulations followed a standardized protocol. Further direct stimulation of the surgically exposed pelvic autonomic nerves was carried out with a hand-guided bipolar microfork probe.

In all six experiments, the transrectal stimulation resulted in significantly increased EMG signals of the somatically innervated EAS (21.0 μV (interquartile range (IQR): 17.8; 64.4) before stimulation vs. 375.8 μV (IQR: 103.4; 895.9) during stimulation, p = 0.004) and autonomically innervated IAS (35.1 μV (IQR: 27.9; 41.7) before stimulation vs. 1115.7 μV (IQR: 420.1; 2920.3) during stimulation, p = 0.008). Subgroup analysis of the observed IAS EMG signals under transrectal stimulation and hand guided direct stimulation revealed no significant differences between both methods (70.5 μV (IQR: 31.5; 322.7) vs. 320.3 μV (IQR: 204.0; 358.0), p = 0.109).

The newly developed multifunctional surface probe enabled successful transrectal stimulation of sacral somatic and autonomic outflow under EMG feedback control. The clinical value of this less invasive approach for the treatment of functional disturbances needs further investigations.

Different encapsulation strategies for implanted electronics

Recent advancements in implant technology include increasing application of electronic systems in the human body. Hermetic encapsulation of electronic components is necessary, specific implant functions and body environments must be considered. Additional functions such as wireless communication systems require specialized technical solutions for the encapsulation.

In this paper 3 different implant strategies based on the material groups silicone, ceramics and titanium alloys are evaluated. With the background of a specific application the requirements for the encapsulation are defined and include the implementation of electrical feedthroughs, wireless communication and wireless energy transfer as well as biomedical specifications such as hermetic sealing, mechanical stability and biocompatibility. The encapsulations are manufactured and qualified experimentally.

Implantable electronics of a closed-loop system for controlling prosthetic hands

This paper presents the design of implantable electronics as a part of a system for prosthetic hand control. Purpose of the implant is the sensing of electrical signals originating from biological tissue and the actuation of the same, therefore closing the loop and allowing for an improved control of the prosthetic hand. The implant contains two integrated circuits for eight channel EMG monitoring and four channel stimulation, respectively. An on-board microcontroller allows for local pre-processing. All intracorporeal to extracorporeal communications are running through and are directed by the main processing platform. The external components of the control system include, in addition to the main processing and control platform, the inductive power transfer circuits and the pressure sensors for the sensory feedback. Different assembly and encapsulation options are taken into account for the implantable electronics and are unified in a single PCB design.

Signal and energy transmission for implanted systems

Aspects and approaches for the design of systems for simultaneous signal and energy transmission for medical implants are presented. The main focus is on the consideration of the mutual influence on both transmission lines. To minimize the influence of capacitive as well as inductive paths, that affect the transmission, reducing the number of components is discussed. In order to increase the degree of miniaturization and reliability, the realization of certain functionalities is based on the so-called parasitics of electrical components. An implementation example is presented.

Extracorporeal Stimulation of Sacral Nerve Roots for Observation of Pelvic Autonomic Nerve Integrity: Description of a Novel Methodological Setup

INTRODUCTION

Neurophysiologic monitoring can improve autonomic nerve sparing during critical phases of rectal cancer surgery.

OBJECTIVES

To develop a system for extracorporeal stimulation of sacral nerve roots.

METHODS

Dedicated software controlled a ten-electrode stimulation array by switching between different electrode configurations and current levels. A built-in impedance and current level measurement assessed the effectiveness of current injection. Intra-anal surface electromyography (sEMG) informed on targeting the sacral nerve roots. All tests were performed on five pig specimens.

RESULTS

During switching between electrode configurations, the system delivered 100% of the set current (25 mA, 30 Hz, 200 μs cathodic pulses) in 93% of 250 stimulation trains across all specimens. The impedance measured between single stimulation array contacts and corresponding anodes across all electrode configurations and specimens equaled 3.7 ± 2.5 kΩ. The intra-anal sEMG recorded a signal amplitude increase as previously observed in the literature. When the stimulation amplitude was tested in the range from 1 to 21 mA using the interconnected contacts of the stimulation array and the intra-anal anode, the impedance remained below 250 Ω and the system delivered 100% of the set current in all cases. Intra-anal sEMG showed an amplitude increase for current levels exceeding 6 mA.

CONCLUSION

The system delivered stable electric current, which was proved by built-in impedance and current level measurements. Intra-anal sEMG confirmed the ability to target the branches of the autonomous nervous system originating from the sacral nerve roots.

SIGNIFICANCE

Stimulation outside of the operative field during rectal cancer surgery is feasible and may improve the practicality of pelvic intraoperative neuromonitoring.

PDMS electrodes for recording and stimulation

The usability of flexible electrodes in moving environment is limited due to different mechanical characteristics of their metallic and polymeric components. To achieve structure compatible electrodes, all used materials need to have similar Young’s moduli as the surrounding tissue. This paper describes the characterization of macroscopic as well as miniaturized electrodes entirely made out of modified silicone (PDMS). Electrochemical, mechanical, biological, optical, and applicative methods were used. It could be shown, that PDMS electrodes are capable to be used for recording electrocardiograms with similar form and amplitude as with standard electrodes.

SEP-induced activity and its thermographic cortical representation in a murine model

This article is a methodical report on the generation of reproducible changes in brain activity in a murine model. Somatosensory evoked potentials (SEP) are used to generate synchronized cortical activity. After electrical stimulation of mice forelimbs, the potentials were recorded with a flexible thin-film polyimide electrode structure directly from the cortex. Every registration included a simultaneous recording from both hemispheres that repeated four times to reproduce and compare the results. The SEPs in the murine model were shown to generate a very stable signal. The latency of the second positive wave (P2 wave) ranged between 16 and 19 ms, and the N1-P2 amplitude ranged between 39 and 48 µV. In addition, the temperature distribution of the cortex was acquired using infrared thermography. Surface cortical temperature changed during electrical stimulation without a clear hemispheric correlation. These initial results could be a step toward a better understanding of the different synchronized cortical activities and basic methods of evaluation of various mathematical algorithms to detect them.

Design and realization of a wireless sensor gateway for health monitoring

This paper describes the design and realization of a wireless sensor gateway (WSG) within a wireless sensor network (WSN) for health monitoring. The WSN allows recording and wireless transmission of biosignals, namely the electrocardiogram, pulse wave and body weight, which are important parameters for cardiovascular monitoring. These can be displayed, analysed, and saved on the WSG through a user interface based on a touch screen. The proposed WSG has the distinctive feature of using two different radio transceivers, exploiting the advantages of each device. Currently, most personal computers and handhelds have standardized Bluetooth interfaces (IEEE 802.15.1) but not ZigBee interfaces (IEEE 802.15.4). Hence, the proposed gateway is designed to receive data from wireless sensors through its ZigBee interface and to forward them to a personal computer via its Bluetooth interface. This feature, combined with simple touch screen menu navigation will reach increased patient compliance and consequently increased benefit for patient in terms of healthcare and safety.

Acquisition of myoelectric signals to control a hand prosthesis with implantable epimysial electrodes

The acquisition of myoelectric signals from the Musculus deltoideus of a rhesus monkey is described. Such signals are aimed to be used as control signal for an active myoelectric hand prosthesis. For recording, implantable flexible, polyimide-based multi-site microelectrodes were placed epimysially on the muscle. EMG signals were recorded during voluntary goal-directed movements of the arm, and analyzed with respect to signal amplitude and frequency.

Electrode structures for acquisition and neural stimulation controlling the cardiovascular system

In this study we present an innovative electrode system, for many different applications in the field of cardiovascular diseases. It is a combination of intelligent communicating dry-surface electrodes, which are able to interact with different sensors especially with an invasive, ultra flexible electrode-system. Dry and smart surface electrodes, which can be integrated in textiles and therefore such electrode are almost "invisible" for patients, are used for ECG acquisition and can be integrated in a communication network. In combination with a pulse oximeter or impedance spectroscopy the pulse transit time (PTT) can be calculated. Additionally, with invasive electrodes the nervous vagus can be stimulated and therefore cardiovascular functions can be controlled. The association of an implanted stimulator with an interacting and smart monitoring system results into a cardiovascular controlling. In this work we will focus on the feasibility, suitability, fabrication and characterization of invasive and dry-surface electrode systems as a basic element and foundation for cardiovascular regulation in a closed loop.

Flexible dry surface-electrodes for ECG long-term monitoring

In this paper a new generation of dry electrodes for ECG-recording purposes is presented. These electrodes are flexible, biocompatible, biostable and perform a dry signal acquisition without the use of any electrolyte gel or adhesive. Thereby no skin preparation is needed. The material properties allow integration into textiles to form intelligent clothes for long-term monitoring duties. The electrodes can be washed together with the carrier textiles and provide a very good wearing comfort resulting in wide acceptance by the patients. The Department Medical Engineering and Neuroprosthetics of the Fraunhofer Institute for Biomedical Engineering developed these electrodes mainly to process the Electrocardiogram, however, in first tests they proved their capability even for other biosignal requirements like surface-EMG. In either case the signal quality of the dry electrodes is comparable to commercial Ag/AgCl gel-electrodes.

Impact of spinal cord injury on self-perceived pre- and postmorbid cognitive, emotional and physical functioning

STUDY DESIGN

Cross-sectional study with repeated measurements.

OBJECTIVES

To examine the patient's perspective of the impact of spinal cord injury (SCI) on physical, cognitive, emotional function, and quality of life (QOL).

SETTING

Australia.

METHODS

A sample of 63 patients with SCI, 32 of whom had recent injuries, and 31 with established injuries were administered the Ruff Neurobehavioral Inventory to examine patients' subjective evaluation of pre- and post-injury functioning. Current happiness levels were also evaluated using the Subjective Happiness Scale. A follow up assessment was performed 6 months later to examine changes over time.

RESULTS

A significant difference was found between perception of pre- and postmorbid function on composite Cognitive (t=5.99, df=62, P<0.001), Physical (t=11.56, df=62, P<0.001), and QOL (t=7.16, df=62, P<0.001) scales and on several of the Emotional subscales including anxiety, paranoia and suspicion, and substance abuse (P<0.001). A series of hierarchical regression analyses indicate that post-SCI pain was a significant predictor of: cognitive (R(2)=0.20, P<0.001); emotional (R(2)=0.13, P<0.004); and of QOL (R(2)=0.22, P<0.001) functioning. With the exception of a decrease in happiness (P<0.01), there were no significant changes in any measures over the 6 month time period.

CONCLUSIONS

There are significant changes in patients' perceptions of physical and cognitive functioning, and of QOL before and after SCI and some aspects of emotional functioning. Pain has a significant adverse effect on functioning. Happiness decreased slightly in the 6 months between surveys.

Long-term characterization of electrode materials for surface electrodes in biopotential recording

The long-term electrical behavior of 16 different electrode materials was investigated by using continuous impedance spectroscopy over a period of 10 days. The materials included bare and electrolytically treated metals, metals coated with intrinsically conductive polymers, and polymers with conductive particles. Electrolytic treatment of metal electrodes yielded a significant impedance reduction. The lowest impedance values could be reached with the polymer-coated metal electrodes. The impedance behavior is an important aspect when choosing an electrode material, and has to be considered in signal processing. The choice of a material depends on the application of the electrode. Moreover, for long-term applications, the electrochemical stability of a material has to be considered.

Visuospatial learning: Ruff Light Trail Learning Test

The assessment of memory typically includes tests for both audioverbal and visuospatial processing, while measurements of learning have primarily utilized the audioverbal mode. However, there exists no compelling reason why learning should not also be assessed in the visuospatial mode. The Ruff Light Trail Learning Test (RULIT) represents such an option. Normative values utilizing 307 volunteers indicated neither significant gender nor educational differences. However, an age effect for those subjects 55 and older was demonstrated, and our data suggest that the major reason for the inferior learning in this older subgroup was their reduced memory capacities rather than their slowed visuospatial processing. Multiple components including learning curves, error analysis, and delayed recall are presented. Test-retest data also indicate an adequate reliability. The validity was compared to concurrently administered neuropsychological tests, and, finally, the potential for neuropsychological application of this new test is discussed.

Efficacy study of THINKable in the attention and memory retraining of traumatically head-injured patients

The efficacy of computer-assisted attention and memory retraining was evaluated with 15 severely head-injured patients. Training with selected exercises tailored to the individual's needs were provided from the THINKable program for up to 20 hours in both the attention and memory remediation modules. The experimental design evaluated outcome by juxtaposing multiple baseline procedures with a pre- and post-group comparison. Significant results were documented on the computerized tasks, psychometric measures and on patient and observer ratings of everyday behaviours of attention and memory.

Hemodynamic effects of a lorazepam-fentanyl anesthetic induction for coronary artery bypass surgery

Previous anesthetic induction techniques using the combination of a benzodiazepine (midazolam or diazepam) and fentanyl have been reported to produce marked hypotension. In this study, anesthesia was induced with a combination of lorazepam and fentanyl in patients undergoing coronary artery bypass graft surgery. In 10 patients, anesthesia was induced using an exponentially declining continuous infusion of lorazepam equivalent to a total infused dose of 0.1 mg/kg over 15 minutes, which was supplemented at 10 minutes by fentanyl, 75 micrograms/kg, given as an infusion over 5 minutes. In 8 additional patients, anesthesia was induced with an exponentially declining infusion of fentanyl to a total dose of 75 micrograms/kg over 15 minutes, which was supplemented at 10 minutes by lorazepam, 0.1 mg/kg, given as an infusion over 5 minutes. Hemodynamics were recorded during a 20-minute observation period. One patient in each group required treatment for bradycardia during the initial drug infusion (before the second drug was added). Four additional patients in the group receiving lorazepam followed by fentanyl required treatment for bradycardia or hypotension within 10 minutes of the beginning of the fentanyl infusion. When an infusion of lorazepam was added to the fentanyl infusion, hemodynamics remained stable; however, the reverse order produced a high level of bradycardia and hypotension.

Comparison of different methods for detecting human immune deficiency virus in human immunodeficiency virus-seropositive hemophiliacs

Since the detection of antibodies against the human immune deficiency virus (HIV) does not definitely prove HIV infection in hemophiliacs, virus detection was attempted by virus isolation from the peripheral blood monocytes (PBL), by demonstration of p24 antigen and decline of p24 antibody, and by detection of viral DNA by the polymerase chain reaction (PCR). Virus isolation was optimized by immediate coculture of PBL and by replacement of the reverse transcriptase test by the p24 antigen test, whereas the elimination of CD8+ lymphocytes proved to be unnecessary. Virus detection was dependent on the clinical stage of the illness. Virus isolation in 70 of 211 patients (33%) was more sensitive than detection of p24 antigen or decline of p24 antibody. PCR was performed in 25 patients and indicated infection in all of 15 isolation-positive cases and in 6 of 10 patients from whom virus was not isolated. Changes from negative to positive virus culture and from a weakly fusiogenic to a highly fusiogenic isolate were often accompanied by a progression of the disease. The results suggest that reactivation of HIV occurs when immune deficiency has become manifest. Apparently virus isolation detects only the virus already reactivated in vivo, whereas the PCR may also detect latent virus.