Perioperative Fluid Management in Surgical Patients: A Review.

Intravenous (IV) fluids are one of the most widely prescribed medications. Despite their frequent usage, IV fluids are often not used appropriately. High-quality evidence to guide the surgeon in the perioperative period is sparse. A plethora of choices for IV fluids exists with limited evidence to help guide the surgeon in specific patient populations and situations. To address this, the authors have set out to provide a critical review of commonly used IV fluids to treat surgical patients. Gaps in the existing literature for the surgical population will also be discussed as potential target areas for future research.

A unified constitutive model for pressure sensitive shear flow transitions in moderate dense granular materials.

Granular shear flows exhibit complex transitional regimes that are dramatically affected by the pressure level and shear stress state. New advances in granular shear tests at low pressure have enlightened the understanding of the two granular shear flow transitions: between quasi-static and moderate shear flows, and between steady-state and transient shear flows. However, a unified constitutive model to describe these two transitions is yet to develop. In this work, a simplified and unified model is proposed based on innovative triaxial shear flow tests, using two dimensionless physical variables. Model results validated against experimental data suggest that the shear flow transition between a quasi-static to a moderate Isotach type flow state is highly pressure-dependent. At extremely low pressure, the granular viscosity becomes the primary mechanism, suppressing the quasi-static mechanism even under "quasi-static" shear rates. In transient to steady state granular flow transitions, a mobilized shear stress ratio or mobilized friction coefficient between zero and the critical state ratio for consolidated granular packings is taken into consideration. This is coupled with the mechanism of granular viscosity. These findings have not been discussed before and are of great relevance to granular mechanics as well as space and earthquake engineering.

Disposable versus reusable medical gowns: A performance comparison.

BACKGROUND: Medical gowns are essential personal protective equipment (PPE) that prevents the spread of microorganisms and bodily fluids. During surge capacity situations, such as the COVID-19 pandemic, reusable PPE is often recommended due to shortages. METHODS: This research evaluated the performance of disposable versus reusable medical gowns by assessing their ability to provide adequate protection across their expected service lifespan. Level I, II, and III gowns were tested for water resistance and hydrostatic pressure, along with other durability assessments (breaking, tear, and seam strength, pilling resistance, dimensional stability, and air permeability, colorfastness, and fabric hand) per standard test methods. Data were collected at new for the disposable gowns and after 1, 25, 50, and 75 industrial launderings for the reusable gowns. Results were compared to the Association of the Advancement Instrumentation® (AAMI) PB70 performance specifications. RESULTS: Level I and II disposable gowns did not meet AAMI performance specifications for impact penetration water resistance. All 3 levels of disposable gowns also failed to meet the American Society for Testing and Materials performance requirements for breaking strength in the crosswise direction. CONCLUSIONS: The adoption of reusable gowns may result in increased protection and significant cost savings due to their superior durability and sustainability when compared to disposable gowns.

Racial Disparities in Coronavirus Disease 2019 (COVID-19) Mortality Are Driven by Unequal Infection Risks.

BACKGROUND: As of 1 November 2020, there have been >230 000 deaths and 9 million confirmed and probable cases attributable to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the United States. However, this overwhelming toll has not been distributed equally, with geographic, race/ethnic, age, and socioeconomic disparities in exposure and mortality defining features of the US coronavirus disease 2019 (COVID-19) epidemic. METHODS: We used individual-level COVID-19 incidence and mortality data from the state of Michigan to estimate age-specific incidence and mortality rates by race/ethnic group. Data were analyzed using hierarchical Bayesian regression models, and model results were validated using posterior predictive checks. RESULTS: In crude and age-standardized analyses we found rates of incidence and mortality more than twice as high than for Whites for all groups except Native Americans. Blacks experienced the greatest burden of confirmed and probable COVID-19 (age-standardized incidence, 1626/100 000 population) and mortality (age-standardized mortality rate, 244/100 000). These rates reflect large disparities, as Blacks experienced age-standardized incidence and mortality rates 5.5 (95% posterior credible interval [CrI], 5.4-5.6) and 6.7 (95% CrI, 6.4-7.1) times higher than Whites, respectively. We found that the bulk of the disparity in mortality between Blacks and Whites is driven by dramatically higher rates of COVID-19 infection across all age groups, particularly among older adults, rather than age-specific variation in case-fatality rates. CONCLUSIONS: This work suggests that well-documented racial disparities in COVID-19 mortality in hard-hit settings, such as Michigan, are driven primarily by variation in household, community, and workplace exposure rather than case-fatality rates.

Metallic Biomaterials: Current Challenges and Opportunities.

Metallic biomaterials are engineered systems designed to provide internal support to biological tissues and they are being used largely in joint replacements, dental implants, orthopaedic fixations and stents. Higher biomaterial usage is associated with an increased incidence of implant-related complications due to poor implant integration, inflammation, mechanical instability, necrosis and infections, and associated prolonged patient care, pain and loss of function. In this review, we will briefly explore major representatives of metallic biomaterials along with the key existing and emerging strategies for surface and bulk modification used to improve biointegration, mechanical strength and flexibility of biometals, and discuss their compatibility with the concept of 3D printing.

An integrated movement capture and control platform applied towards autonomous movements of surgical robots.

Robotic surgery has gradually gained acceptance due to its numerous advantages such as tremor filtration, increased dexterity and motion scaling. There remains, however, a significant scope for improvement, especially in the areas of surgeon-robot interface and autonomous procedures. Previous studies have attempted to identify factors affecting a surgeon's performance in a master-slave robotic system by tracking hand movements. These studies relied on conventional optical or magnetic tracking systems, making their use impracticable in the operating room. This study concentrated on building an intrinsic movement capture platform using microcontroller based hardware wired to a surgical robot. Software was developed to enable tracking and analysis of hand movements while surgical tasks were performed. Movement capture was applied towards automated movements of the robotic instruments. By emulating control signals, recorded surgical movements were replayed by the robot's end-effectors. Though this work uses a surgical robot as the platform, the ideas and concepts put forward are applicable to telerobotic systems in general.

NASA TLX: software for assessing subjective mental workload.

The NASA Task Load Index (TLX) is a popular technique for measuring subjective mental workload. It relies on a multidimensional construct to derive an overall workload score based on a weighted average of ratings on six subscales: mental demand, physical demand, temporal demand, performance, effort, and frustration level. A program for implementing a computerized version of the NASA TLX is described. The software version assists in simplifying collection, postprocessing, and storage of raw data. The program collects raw data from the subject and calculates the weighted (or unweighted) workload score, which is output to a text file. The program can also be tailored to a specific experiment using a simple input text file, if desired. The program was designed in Visual Studio 2005 and is capable of running on a Pocket PC with Windows CE or on a PC with Windows 2000 or higher. The NASA TLX program is available for free download.

Performance of basic manipulation and intracorporeal suturing tasks in a robotic surgical system: single- versus dual-monitor views.

BACKGROUND: Technical advances in the application of laparoscopic and robotic surgical systems have improved platform usability. The authors hypothesized that using two monitors instead of one would lead to faster performance with fewer errors. METHODS: All tasks were performed using a surgical robot in a training box. One of the monitors was a standard camera with two preset zoom levels (zoomed in and zoomed out, single-monitor condition). The second monitor provided a static panoramic view of the whole surgical field. The standard camera was static at the zoomed-in level for the dual-monitor condition of the study. The study had two groups of participants: 4 surgeons proficient in both robotic and advanced laparoscopic skills and 10 lay persons (nonsurgeons) who were given adequate time to train and familiarize themselves with the equipment. Running a 50-cm rope was the basic task. Advanced tasks included running a suture through predetermined points and intracorporeal knot tying with 3-0 silk. Trial completion times and errors, categorized into three groups (orientation, precision, and task), were recorded. RESULTS: The trial completion times for all the tasks, basic and advanced, in the two groups were not significantly different. Fewer orientation errors occurred in the nonsurgeon group during knot tying (p=0.03) and in both groups during suturing (p=0.0002) in the dual-monitor arm of the study. Differences in precision and task error were not significant. CONCLUSIONS: Using two camera views helps both surgeons and lay persons perform complex tasks with fewer errors. These results may be due to better awareness of the surgical field with regard to the location of the instruments, leading to better field orientation. This display setup has potential for use in complex minimally invasive surgeries such as esophagectomy and gastric bypass. This technique also would be applicable to open microsurgery.

Evaluation of pancreatic cancer with Raman spectroscopy in a mouse model.

OBJECTIVES: Detection of neoplastic changes using optical spectroscopy has been an active area of research in recent times. Raman spectroscopy is a vibrational spectroscopic technique that can be used to diagnose various tumors with high sensitivity and specificity. We evaluated the ability of Raman spectroscopy to differentiate normal pancreatic tissue from malignant tumors in a mouse model. METHODS: We collected 920 spectra, 475 from 31 normal pancreatic tissue and 445 from 29 tumor nodules using a 785-nm near-infrared laser excitation. Discriminant function analysis was used for classification of normal and tumor samples. RESULTS: Using principal component analysis, we were able to highlight subtle chemical differences in normal and malignant tissue. Using histopathology as the gold standard, Raman analysis gave sensitivities between 91% and 96% and specificities between 88% and 96%. CONCLUSIONS: Raman spectroscopy along with discriminant function analysis is a useful method to detect cancerous changes in the pancreas. Pancreatic tumors were characterized by increased collagen content and decreased DNA, RNA, and lipids components compared with normal pancreatic tissue.

Diagnosis of neuroblastoma and ganglioneuroma using Raman spectroscopy.

BACKGROUND: Raman spectroscopy has proven to be useful in studying premalignant and malignant lesions in adults. This is the first report to evaluate Raman spectroscopy in the diagnosis and classification of neuroblastoma in children. METHODS: A biopsy or resection of fresh tissue samples from normal adrenal glands, neuroblastomas, ganglioneuromas, nerve sheath tumors, and pheochromocytoma at our hospital were equally divided between routine histology and spectroscopic studies. At least 12 spectra were collected from different regions of each sample using a Renishaw Raman microscope. Raw spectra were processed to remove noise, fluorescence, and shot noise, and then analyzed using principle component analysis and discriminant function analysis. RESULTS: We collected 698 spectra from 16 neuroblastomas, 5 ganglioneuromas, 3 normal adrenal glands, 6 nerve sheath tumors, and 1 pheochromocytoma. Raman spectroscopy differentiated between normal adrenal gland, and neuroblastoma and ganglioneuroma with 100% sensitivity and 100% specificity. It correlated well with the Shimada histologic classification system with 100% sensitivity and 100% specificity. It was also able to differentiate neuroblastoma from nerve sheath tumors and pheochromocytoma with high sensitivity and specificity. CONCLUSION: This technique can differentiate neuroblastoma from ganglioneuroma and other tumors. It has a potential as a noninvasive real-time diagnostic tool in classifying pediatric tumors.

Raman spectroscopy can differentiate malignant tumors from normal breast tissue and detect early neoplastic changes in a mouse model.

Raman spectroscopy shows potential in differentiating tumors from normal tissue. We used Raman spectroscopy with near-infrared light excitation to study normal breast tissue and tumors from 11 mice injected with a cancer cell line. Spectra were collected from 17 tumors, 18 samples of adjacent breast tissue and lymph nodes, and 17 tissue samples from the contralateral breast and its adjacent lymph nodes. Discriminant function analysis was used for classification with principal component analysis scores as input data. Tissues were examined by light microscopy following formalin fixation and hematoxylin and eosin staining. Discriminant function analysis and histology agreed on the diagnosis of all contralateral normal, tumor, and mastitis samples, except one tumor which was found to be more similar to normal tissue. Normal tissue adjacent to each tumor was examined as a separate data group called tumor bed. Scattered morphologically suspicious atypical cells not definite for tumor were present in the tumor bed samples. Classification of tumor bed tissue showed that some tumor bed tissues are diagnostically different from normal, tumor, and mastitis tissue. This may reflect malignant molecular alterations prior to morphologic changes, as expected in preneoplastic processes. Raman spectroscopy not only distinguishes tumor from normal breast tissue, but also detects early neoplastic changes prior to definite morphologic alteration.

Comparison of a supplemental wide field of view versus a single field of view with zoom on performance in minimally invasive surgery.

BACKGROUND: The limited space and high magnification involved in minimally invasive surgery (MIS) can cause surgeons to lose sight of an instrument while performing tasks such as suturing and knot-tying. A current strategy employed to locate the instrument is zooming out and in with the endoscope, which can be a time-intensive and iterative task. This study investigates the use of a supplemental wide field of view (FOV) via a second endoscope for locating an instrument outside the FOV in a MIS setting. METHODS: Ten surgically naïve subjects performed a simple aimed movement task with either hand (dominant or nondominant) under two display conditions: (1) conventional single monitor with zoom, and (2) supplemental wide FOV monitor with no zoom. The task emulated the need to locate an instrument outside the surgeon's FOV and return it to a home position. RESULTS: The supplemental wide FOV produced significantly faster times [F(3,716) = 173.2, p < 0.001)] compared to a single monitor. The task was accomplished most quickly with the dual monitor with the dominant hand, followed by dual monitor with nondominant hand followed by a single monitor with either hand. There were also significantly fewer errors (t = 3.734, df = 9, p = 0.005) with the supplemental wide FOV. None of the subjects were slower with the dual monitor, and all but one had fewer errors. The variance for both task times and errors were also significantly smaller (p < 0.001 and p = 0.008, respectively) with the supplemental wide FOV indicating that subjects performed with increased reliability. CONCLUSION: The supplemental wide FOV gave the subjects the ability to see their instrument at all times providing a more efficient display than zooming out and in. This enabled faster times and fewer errors while allowing the user to perform the task with more consistency.

Ca2+ from one or two channels controls fusion of a single vesicle at the frog neuromuscular junction.

Neurotransmitter release is triggered by the cooperative action of approximately five Ca2+ ions entering the presynaptic terminal through Ca2+ channels. Depending on the organization of the active zone (AZ), influx through one or many channels may be needed to cause fusion of a vesicle. Using a combination of experiments and modeling, we examined the number of channels that contribute Ca2+ for fusion of a single vesicle in a frog neuromuscular AZ. We compared Ca2+ influx to neurotransmitter release by measuring presynaptic action potential-evoked (AP-evoked) Ca2+ transients simultaneously with postsynaptic potentials. Ca2+ influx was manipulated by changing extracellular [Ca2+] (Ca(ext)) to alter the flux per channel or by reducing the number of open Ca2+ channels with omega-conotoxin GVIA (omega-CTX). When Ca(ext) was reduced, the exponent of the power relationship relating release to Ca2+ influx was 4.16 +/- 0.62 (SD; n = 4), consistent with a biochemical cooperativity of approximately 5. In contrast, reducing influx with omega-CTX yielded a power relationship of 1.7 +/- 0.44 (n = 5) for Ca(ext) of 1.8 mM and 2.12 +/- 0.44 for Ca(ext) of 0.45 mM (n = 5). Using geometrically realistic Monte Carlo simulations, we tracked Ca2+ ions as they entered through each channel and diffused in the terminal. Experimental and modeling data were consistent with two to six channel openings per AZ per AP; the Ca2+ that causes fusion of a single vesicle originates from one or two channels. Channel cooperativity depends mainly on the physical relationship between channels and vesicles and is insensitive to changes in the non-geometrical parameters of our model.

Supplemental wide field-of-view monitor improves performance in surgical telerobotic movement time.

BACKGROUND: This study investigates the effect of a supplemental wide field-of-view (FOV) monitor on performance at high magnifications where the benefits of robotic surgery have greater importance. METHODS: Ten surgically naïve participants performed a simple aimed movement task under two different monitor conditions. The task is intended to emulate the need to locate an instrument outside the surgeon's FOV and return it to a 'home' position without the need to zoom. One monitor condition used a narrow FOV (25x) coupled with a supplemental wide FOV (3x). The second monitor condition used only a narrow FOV. RESULTS: Using a supplemental wide FOV in addition to a narrow FOV improved task performance by at least 33%, with greater consistency and reliability. CONCLUSION: The supplemental wide FOV monitor provided additional information to the participant, allowing more efficient performance at high magnifications without the need for zooming.

Computer-assisted, robot-enhanced open microsurgery in an animal model.

BACKGROUND: Computer-assisted, robot-enhanced surgery improves laparoscopic and thoracoscopic surgery through tremor filtration, motion scaling, articulation, and improved ergonomics. Surgeons perform many open cases under magnification that magnifies the tremor present in all surgeons' hands, so the tremor filtration and motion scaling of robotic surgery may improve microsurgery. Our goal was to compare microvascular anastomoses performed with a robot-enhanced technique with a standard technique. METHODS: We performed end-to-end anastomoses in 1-mm rat femoral arteries with interrupted 10-0 suture. We compared the anastomotic time, patency, and leak rates between traditional microsurgery techniques (by hand) and a robot-enhanced technique using the Zeus robotic surgery system (Computer Motion, Goleta, California). The surgeon used an operative microscope for visualization in both techniques. RESULTS: We performed 30 anastomoses by hand and 31 with Zeus. We observed a remarkable degree of tremor filtration in the robot-enhanced cases. Anastomotic times for both techniques demonstrated a learning curve. Anastomoses done by hand (mean time, 17.2 minutes) were significantly faster than those done with Zeus (mean time, 27.6 minutes) (P = 0.0006). All anastomoses from both groups were patent, and none leaked after 3 minutes. CONCLUSION: The Zeus system is effective at performing complex, open, microsurgery tasks in vivo. There was no measurable benefit from the remarkable tremor filtration and motion scaling offered by robot-enhanced surgery.

Raman spectroscopy for neoplastic tissue differentiation: a pilot study.

BACKGROUND: Several changes occur during the transformation of normal tissue to neoplastic tissue. Such changes in molecular composition can be detected by Raman spectroscopy. Raman spectroscopy is a nondestructive method of measuring these changes, which suggests the possibility of real-time diagnosis during medical procedures. METHODS: This study seeks to evaluate the ability of Raman spectra to distinguish tissues. The Raman signatures of normal kidney, lung, and liver tissue samples from pigs and rats were characterized in vitro. Further, a human neuroblastoma and a hepatoblastoma, obtained at resection were also studied. RESULTS: The Raman spectra of the animal samples of kidney, liver, and lung are distinctly different in the intensity distribution of the Raman peaks. Further, the spectra of a given organ from pigs and rats, although similar, were different enough to distinguish between the 2 animals. In the patient tissues, the Raman spectra of normal liver, viable tumor, and fibrotic hepatoblastoma were very different. Fibrotic tissue showed a greater concentration of carotenoids, whereas viable tissue was rich in proteins and nucleic acids. The normal tissue showed both components. Similar differences were also seen in the neuroblastoma tissue. CONCLUSIONS: The results of this study show the potential use of Raman spectroscopy in clinical diagnosis.