Evaluation of a Protocol for the Management of Maintenance and Reversal of Rocuronium Block Using Neostigmine or Sugammadex.

BACKGROUND: Postoperative residual neuromuscular blockade (PRNB) is defined as an adductor pollicis train-of-four ratio (TOFR) <0.9. It is a common postoperative complication when nondepolarizing muscle relaxants are either not reversed or reversed with neostigmine. PRNB has been reported in 25% to 58% of patients who receive intermediate-acting nondepolarizing muscle relaxants, and it is associated with increased morbidity and decreased patient satisfaction. We conducted a prospective descriptive cohort study during the implementation of a practice guideline that included the selective use of sugammadex or neostigmine. The primary study aim of this pragmatic study was to estimate the incidence of PRNB at arrival to the postanesthesia care unit (PACU) when the practice guideline is followed. METHODS: We enrolled patients undergoing orthopedic or abdominal surgery requiring neuromuscular blockade. Rocuronium administration was guided by surgical requirements and based on ideal body weight, with dose reductions for women and/or age >55 years. Only qualitative monitoring was available to the anesthesia providers, and selection of sugammadex or neostigmine was guided by tactile assessments of the response to train-of-four (TOF) stimulation by a peripheral nerve stimulator. Neostigmine was administered if no fade was detected in the TOF response at the thumb. Deeper blocks were reversed with sugammadex. The prespecified primary and secondary end points were the incidence of PRNB at arrival to the PACU, defined as a normalized TOFR (nTOFR) < 0.9, and severe PRNB, defined as nTOFR <0.7 on arrival to the PACU. Anesthesia providers were blinded to all quantitative measurements made by research staff. RESULTS: Analysis included 163 patients, and 145 underwent orthopedic and 18 abdominal surgeries. Of the 163 patients, 92 (56%) were reversed with neostigmine and 71 (44%) with sugammadex. The overall incidence of PRNB at PACU arrival was 5 of 163 or 3% (95% confidence interval [CI], 1-7). The incidence of severe PRNB in PACU was 1% (95% CI, 0-4). Three of the 5 subjects with PRNB had TOFR <0.4 at time of reversal but were given neostigmine since anesthesia providers detected no fade by qualitative assessment. CONCLUSIONS: The use of a protocol that specifies rocuronium dosing and selective use of sugammadex versus neostigmine based on qualitative assessment of TOF count and fade allowed us to achieve an incidence of PRNB of 3% (95% CI, 1-7) at PACU arrival. Quantitative monitoring may be needed to further reduce this incidence.

Disposable Autonomous Device for Swab-to-Result Diagnosis of Influenza.

A prototype of a self-contained, automated, disposable device for chemically amplified protein-based detection of influenza virus from nasal swab specimens was developed and evaluated in a clinical setting. The device required only simple specimen manipulation without any dedicated instrumentation or specialized training by the operator for interpretation. The device was based on a sandwich immunoassay for influenza virus nucleoprotein; it used an enzyme-labeled antibody and a chromogenic substrate to provide an amplified visible signal, in a two-dimensional paper network format. All reagents were stored within the device. Device performance was assessed at Seattle Children's Hospital; clinical staff collected nasal swab samples from 25 patients and then operated test devices on site to detect influenza A and B in those specimens. The total test time from device initiation to result was approximately 35 min. Device performance for influenza A detection was ∼70% accurate using in-house qRT-PCR influenza A as a gold-standard comparison. The ratio of valid to total completed device runs yielded a success rate of 92%, and the negative predictive value for both the influenza A and B assay was 81%. The ability to diagnose respiratory infections rapidly and close to the patient was well received by hospital staff, inspiring further optimization of device function.

Investigation of Reagent Delivery Formats in a Multivalent Malaria Sandwich Immunoassay and Implications for Assay Performance.

Conventional lateral flow tests (LFTs), the current standard bioassay format used in low-resource point-of-care (POC) settings, have limitations that have held back their application in the testing of low concentration analytes requiring high sensitivity and low limits of detection. LFTs use a premix format for a rapid one-step delivery of premixed sample and labeled antibody to the detection region. We have compared the signal characteristics of two types of reagent delivery formats in a model system of a sandwich immunoassay for malarial protein detection. The premix format produced a uniform binding profile within the detection region. In contrast, decoupling the delivery of sample and labeled antibody to the detection region in a sequential format produced a nonuniform binding profile in which the majority of the signal was localized to the upstream edge of the detection region. The assay response was characterized in both the sequential and premix formats. The sequential format had a 4- to 10-fold lower limit of detection than the premix format, depending on assay conjugate concentration. A mathematical model of the assay quantitatively reproduced the experimental binding profiles for a set of rate constants that were consistent with surface plasmon resonance measurements and absorbance measurements of the experimental multivalent malaria system.

Dissolvable bridges for manipulating fluid volumes in paper networks.

A capability that is key to increasing the performance of paper microfluidic devices is control of fluid transport in the devices. We present dissolvable bridges as a novel method of manipulating fluid volumes within paper-based devices. We demonstrate and characterize the operation of the bridges, including tunability of the volumes passed from 10 µL to 80 µL, using parameters such as geometry and composition. We further demonstrate the utility of dissolvable bridges in the important context of automated delivery of different volumes of a fluid from a common source to multiple locations in a device for simple device loading and activation.

Tunable-delay shunts for paper microfluidic devices.

We demonstrate a novel method for controlling fluid flow in paper-based devices. The method delays fluid progress through a porous channel by diverting fluid into an absorbent pad-based shunt placed into contact with the channel. Parameters to control the delay include the length and the thickness of the shunt. Using this method, reproducible delays ranging from 3 to 20 min were achieved. A simple electrical circuit model was presented and used to predict the delays in a system. Results from the model showed good agreement with experimental observations. Finally, the shunts were used for the sequential delivery of fluids to a detection zone in a point-of-care compatible folding card device using biochemical reagents for the amplified detection of the malaria protein PfHRP2.

Two-dimensional paper network format that enables simple multistep assays for use in low-resource settings in the context of malaria antigen detection.

The lateral flow test has become the standard bioassay format in low-resource settings because it is rapid, easy to use, and low in cost, uses reagents stored in dry form, and is equipment-free. However, lateral flow tests are often limited to a single chemical delivery step and not capable of the multistep processing characteristic of high performance laboratory-based assays. To address this limitation, we are developing a paper network platform that extends the conventional lateral flow test to two dimensions; this allows incorporation of multistep chemical processing, while still retaining the advantages of conventional lateral flow tests. Here, we demonstrate this format for an easy-to-use, signal-amplified sandwich format immunoassay for the malaria protein PfHRP2. The card contains reagents stored in dry form such that the user need only add sample and water. The multiple flows in the device are activated in a single user step of folding the card closed; the configuration of the paper network automatically delivers the appropriate volumes of (i) sample plus antibody conjugated to a gold particle label, (ii) a rinse buffer, and (iii) a signal amplification reagent to the capture region. These results highlight the potential of the paper network platform to enhance access to high-quality diagnostic capabilities in low-resource settings in the developed and developing worlds.

Enhanced sensitivity of lateral flow tests using a two-dimensional paper network format.

Point-of-care diagnostic assays that are rapid, easy-to-use, and low-cost are needed for use in low-resource settings; the lateral flow test has become the standard bioassay format in such settings because it meets those criteria. However, for a number of analytes, conventional lateral flow tests lack the sensitivity needed to have clinical utility. To address this limitation, we are developing a paper network platform that extends the conventional lateral flow test to two dimensions. The two-dimensional structures allow incorporation of multistep processes for improved sensitivity, while still retaining the positive aspects of conventional lateral flow tests. Here we create an easy-to-use, signal-amplified immunoassay based on a modified commercial strip test for human chorionic gonadotropin, the hormone used to detect pregnancy, and demonstrate an improved limit of detection compared to a conventional lateral flow assay. These results highlight the potential of the paper network platform to enhance access to high-quality diagnostic capabilities in low-resource settings in the developed and developing worlds.

Dissolvable fluidic time delays for programming multi-step assays in instrument-free paper diagnostics.

Lateral flow tests (LFTs) are an ingenious format for rapid and easy-to-use diagnostics, but they are fundamentally limited to assay chemistries that can be reduced to a single chemical step. In contrast, most laboratory diagnostic assays rely on multiple timed steps carried out by a human or a machine. Here, we use dissolvable sugar applied to paper to create programmable flow delays and present a paper network topology that uses these time delays to program automated multi-step fluidic protocols. Solutions of sucrose at different concentrations (10-70% of saturation) were added to paper strips and dried to create fluidic time delays spanning minutes to nearly an hour. A simple folding card format employing sugar delays was shown to automate a four-step fluidic process initiated by a single user activation step (folding the card); this device was used to perform a signal-amplified sandwich immunoassay for a diagnostic biomarker for malaria. The cards are capable of automating multi-step assay protocols normally used in laboratories, but in a rapid, low-cost, and easy-to-use format.