Improving escalation of deteriorating patients through cognitive task analysis: Understanding differences between work-as-prescribed and work-as-done

BACKGROUND

Appropriate care escalation requires the detection and communication of in-hospital patient deterioration. Although deterioration in the ward environment is common, there continue to be patient deaths where problems escalating care have occurred. Learning from the everyday work of health care professionals (work-as-done) and identifying performance variability may provide a greater understanding of the escalation challenges and how they overcome these. The aims of this study were to i) develop a representative model detailing escalation of care ii) identify performance variability that may negatively or positively affect this process and iii) examine linkages between steps in the escalation process.

METHODS

Thirty Applied Cognitive Task Analysis interviews were conducted with clinical experts (>4 years' experience) including Ward Nurses (n = 7), Outreach or Sepsis Nurses (n = 8), Nurse Manager or Consultant (n = 6), Physiotherapists (n = 4), Advanced Practitioners (n = 4), and Doctor (n = 1) from two National Health Service hospitals and analysed using Framework Analysis. Task-related elements of care escalation were identified and represented in a Functional Resonance Analysis Model.

FINDINGS

The NEWS2's clinical escalation response constitutes eight unique tasks and illustrates work-as-prescribed, but our interview data uncovered an additional 24 tasks (n = 32) pertaining to clinical judgement, decisions or processes reflecting work-as-done. Over a quarter of these tasks (9/32, 28 %) were identified by experts as cognitively challenging with a high likelihood of performance variability. Three out of the nine variable tasks were closely coupled and interdependent within the Functional Resonance Analysis Model ('synthesising data points', 'making critical decision to escalate' and 'identifying interim actions') so representing points of potential escalation failure. Data assimilation from different clinical information systems with poor usability was identified as a key cognitive challenge.

CONCLUSION

Our data support the emphasis on the need to retain clinical judgement and suggest that future escalation protocols and audit guidance require in-built flexibility, supporting staff to incorporate their expertise of the patient condition and the clinical environment. Improved information systems to synthesise the required data surrounding an unwell patient to reduce staff cognitive load, facilitate decision-making, support the referral process and identify actions are required. Fundamentally, reducing the cognitive load when assimilating core escalation data allows staff to provide better and more creative care. Study registration (ISRCTN 38850) and ethical approval (REC Ref 20/HRA/3828; CAG-20CAG0106).

Exploring the Professional Identity of Hospital Pharmacists in British Columbia

Background

Pharmacists lack a cohesive professional identity, with only limited previous research on the formation of a professional identity for pharmacy. In particular, there is sparse information on the professional identity of pharmacists who practise in hospital settings.

Objectives

To determine hospital pharmacists' professional identity and the characteristics of an ideal pharmacist and ideal practice setting.

Methods

This qualitative study used key informant interviews with semistructured questions. A maximum variation sampling strategy was used to recruit a cross-section of pharmacists from different geographic areas of British Columbia who were practising in a variety of roles. The interviews were transcribed and then analyzed thematically.

Results

Nineteen pharmacists participated in the study. Seven themes pertaining to hospital pharmacists' professional identity were generated, specifically medication expert, therapy optimizer, collaborator, educator, researcher, patient advocate, and unknown professional. Similarities were found with personas previously identified in a population of primarily community pharmacists. The ideal pharmacist was described as being a medication expert, a collaborator, and a leader. The ideal practice setting was characterized as being adequately funded and allowing pharmacists to practise to their full scope.

Conclusions

Hospital pharmacists' professional identity is based on being a medication expert who is seen as an essential member of a collaborative team.

'You can't walk through water without getting wet' UK nurses' distress and psychological health needs during the Covid-19 pandemic: A longitudinal interview study

BACKGROUND

Pre-COVID-19 research highlighted the nursing profession worldwide as being at high risk from symptoms of burnout, post-traumatic stress disorder (PTSD) and suicide. The World Health Organization declared a pandemic on 11th March 2020 due to the sustained risk of further global spread of COVID-19. The high healthcare burden associated with COVID-19 has increased nurses' trauma and workload, thereby exacerbating pressure on an already strained workforce and causing additional psychological distress for staff.

OBJECTIVES

The Impact of COVID-19 on Nurses (ICON) interview study examined the impacts of the pandemic on frontline nursing staff's psychosocial and emotional wellbeing.

DESIGN

Longitudinal qualitative interview study.

SETTINGS

Nurses who had completed time 1 and 2 of the ICON survey were sampled to include a range of UK work settings including acute, primary and community care and care homes. Interviewees were purposively sampled for maximum variation to cover a broad range of personal and professional factors, and experiences during the COVID-19 pandemic, including redeployment.

METHODS

Nurses participated in qualitative in-depth narrative interviews after the first wave of COVID-19 in July 2020 (n = 27) and again at the beginning of the second wave in December 2020 (n = 25) via video and audio platform software. Rigorous qualitative narrative analysis was undertaken both cross-sectionally (within wave) and longitudinally (cross wave) to explore issues of consistency and change.

RESULTS

The terms moral distress, compassion fatigue, burnout and PTSD describe the emotional states reported by the majority of interviewees leading many to consider leaving the profession. Causes of this identified included care delivery challenges; insufficient staff and training; PPE challenges and frustrations. Four themes were identified: (1) 'Deathscapes' and impoverished care (2) Systemic challenges and self-preservation (3) Emotional exhaustion and (4) (Un)helpful support.

CONCLUSIONS

Nurses have been deeply affected by what they have experienced and report being forever altered with the impacts of COVID-19 persisting and deeply felt. There is an urgent need to tackle stigma to create a psychologically safe working environment and for a national COVID-19 nursing workforce recovery strategy to help restore nurse's well-being and demonstrate a valuing of the nursing workforce and therefore support retention.

601 The Effect of the COVID-19 Pandemic on Hip Fracture Mortality in The South West of England

Aim

High perioperative mortality rates in surgical patients suffering concomitant COVID-19 infection have contributed to a fall in elective and urgent surgery. However, data and debate have centred around post hoc infected cases, without the context of the rest of the surgical cohort, and without comparable historical control groups. We aimed to address this by studying patients with a neck of femur fracture. This common condition has a stable incidence with good prospective data collected routinely for the National Hip Fracture Database (NHFD).

Method

We analysed NHFD data for all hospitals within our region over a 3-month period, covering the height of the first outbreak and compared this with the same months in 2019.

Results

The incidence of hip fracture was stable (463 in 2019, 448 in 2020). 30-day mortality was 6.26% in 2019 and 7.14% in 2020 (p = 0.595). In the second cohort, 14 patients tested positive for COVID-19 perioperatively. Of these, 3 died (21%) compared to 29 who tested negative (p < 0.001). Mean time to operation reduced by 1.90 hours, with a significant drop in patients waiting over 36 hours (190 to 85, p < 0.001). There were no significant differences between gender, ASA grade or pre-operative AMTS.

Conclusions

We have confirmed high perioperative mortality for those with COVID-19 infection but have not shown a statistically significant difference in overall mortality from hip fracture during the initial phase of the pandemic. We argue from this data set that the hypothetical risk of surgery during this pandemic may have been overestimated.

Electric impedance spectroscopy feature extraction for tissue classification with electrode embedded surgical needles through a modified forward stepwise method

There has been a growing interest in developing electric impedance sensing surgical tools for tissue identification during surgery. A key facet of this development is identifying distinct features that can be used to identify tissues from one another. This paper explores several feature extraction techniques and classification methods applied to electric impedance data. Furthermore, a modified forward stepwise method is proposed. The method introduces a scoring metric to help select features to add to the model, that is based off of the coefficient of variation and overlapping index from the feature's probability density functions for each of the classes. The proposed and existing methods were applied to spectral data measured at 23 frequencies, from 132 samples across 6 different tissues including ex-vivo bovine kidney, liver and muscle, poultry liver, as well as freshly excised canine testicle and ovary samples. These methods were able to successfully find impedance spectra features for the investigated biological tissues. The best predictive accuracy was with Boruta feature extraction and a Random Forest classifier but without significantly reducing the number of features in the classifier model. The proposed method was able to reduce the number of features in the model to an average of 5.8 features for all tested classifiers. These methods may have use in finding features to discriminate other tissue types, possibly to aid in targeting lesions in minimally invasive cancer treatment surgeries.

52 I’m on the Floor and Can’t Get up and it’s Really Annoying: A Qualitative Investigation of Patient and Staff Perceptions of Options for Getting up From the Floor Following A Fall

Background

Falls are the most common reason for ambulance call-outs resulting in non-conveyance. Even in the absence of injury, only half of those who have fallen can get themselves up off the floor. Many remain there for over an hour, increasing complications risks.

It is feasible to teach people techniques to help get themselves off the floor, yet these techniques are rarely taught. To date, there are no published data on attitudes towards teaching and learning these techniques. Our study aimed to investigate patient, carer and staff attitudes towards seeking help and using techniques to get-up following a fall.

Methods

A qualitative focus group and semi-structured interviews were conducted with 28 participants, including community-dwelling older people who had experienced a non-injurious fall, carers, physiotherapists, occupational therapists, paramedics and community first responders.

Data were transcribed and analysed systematically using the Framework approach. A stakeholder group of falls experts and patients advised during analysis.

Results

The data highlighted three areas contributing to an individual’s capability to get-up following a fall: the environment (physical and social); physical ability; and degree of self-efficacy (attitude and beliefs about their own ability). These factors influenced each person’s capability to manage their fall response.

Staff described how they balance their responsibilities, prioritising the individual’s immediate needs; this leaves limited time to address capability in the aforementioned three areas. Paramedics, routinely responding to falls, only receive training on getting-up techniques from within their peer-group. Therapists are aware of the skillset to breakdown the getting-up process, but, with limited time, select who to teach these techniques to.

Conclusion

Neither therapists nor ambulance service staff routinely teach all those at risk of falling strategies on how to get-up. Interventions to positively impact on capability to get-up following a fall should include strategies that address the environment, physical ability and self-efficacy.

Preventing excessive gestational weight gain: a systematic review of interventions

Women who gain excessive weight during pregnancy have an increased risk of post-partum obesity, and retention of gestational weight gain (GWG) post birth is a strong predictor of maternal overweight/obesity a decade or more after the birth. The aim of the current review was to identify, and evaluate the effect of key variables designed to modify risk factors for excessive weight gain in pregnant women that have been targeted in interventions over the last decade. The 10 interventions focused primarily on behavioural changes in relation to physical activity and/or to eating. While six studies reported significantly less weight gain in the intervention women, only three showed that women in the intervention were significantly more likely to gain within recommended guidelines. GWG was reduced in only normal-weight, low-income, obese, or overweight women, or not at all. Only one study reported a reduction in GWG in women with body mass indexes spanning the normal, overweight and obese categories. The findings were inconsistent in relation to what factors need to be targeted in intervention programmes to reduce GWG. Consideration of psychological factors relevant to pregnancy, in addition to behavioural changes in relation to eating and physical activity, is suggested for future intervention studies.

Endoscopic ultrasound with fine needle aspiration and biopsy in lung cancer and isolated mediastinal lymphadenopathy

Endoscopic ultrasound with fine-needle aspiration and biopsy (EUS-FNAB) is well established in diagnosing and staging lung cancer in patients with mediastinal adenopathy. EUS-FNAB is highly sensitive, less invasive and has lower complication rates when compared to surgical staging of mediastinal nodes. In this study we describe our experience of EUS-FNAB in lung cancer and other causes of mediastinal lymphadenopathy. EUS-FNAB was performed for assessment of PET positive mediastinal lymph nodes between January 2007 and March 2009 in AMNCH. The endpoints of our study were sensitivity and specificity of EUS-FNAB, morbidity and length of hospital stay. Thirty four patients underwent EUS-FNAB during the study period for both diagnosis and staging. Thirty patients had positive lymph node invasion and 4 had no evidence of malignant invasion. In these 4 patients negative cytology was confirmed on mediastinoscopy giving EUS-FNAB a sensitivity and specificity of 100%. EUS-FNAB upstaged the disease in 12 patients. EUS-FNAB is a reliable tool for mediastinal staging in lung cancer, significantly reducing the need for surgical staging procedures in patients with suspected mediastinal involvement.

A case study of DNAPL remediation in northeastern Brazil

Aquifer restoration in the United States is recognized as a technically challenging objective when dense non-aqueous phase liquids (DNAPLs) are present (1). In fact, only a few aquifers impacted by DNAPLs have been restored. Factors that have typically contributed to the lack of successful aquifer restoration include the chemical properties of the DNAPL, the physical properties of the aquifer, the absence of cost-effective technologies, and an incomplete or inaccurate development of a conceptual hydrogeological model for the site. In Latin America, environmental studies historically have been related to biological quality of surface water and groundwater. Recently, the U.S. and Canada have experienced an increased influx of foreign students and professionals interested in studying specialized courses in environmental engineering, or participating in conferences. This exposure to current topics has strengthened the awareness of these professionals regarding groundwater contamination from gasoline-derived compounds and chlorinated solvents. As a result of this increased awareness, Latin American hydrogeologists and environmental regulators have been able to recognize the potential problems that could result from DNAPL spills that may impact groundwater and have learned to approach them using locally available technology and resources. A case study of such an example is presented below.

Remediation of NAPL-contaminated aquifers: is the cure worth the cost?

Millions of dollars are spent in the United States each year to design, construct, and operate systems intended to remediate groundwater impacted by dense non-aqueous phase liquids (DNAPLs), such as trichloroethlene (TCE) and tetrachloroethene (PCE), or light non-aqueous phase liquids (LNAPLs), such as gasoline, diesel, and jet fuel. However, several recent studies suggest that many of these groundwater remediation systems may operate for decades without restoring groundwater to background conditions. This paper examines the potential economic impacts of continuing the current regulatory approach to remediation of NAPL-contaminated aquifers versus considering regionally contaminated aquifers as large storage basins instead of pristine resources. Treating water at the point of extraction when needed, provides an equivalent benefit and may be more practical and cost effective than attempting to restore aquifers to background conditions at the point of contamination.

Pseudoaneurysm of the lingual artery secondary to tonsillectomy treated with selective embolization

False aneurysm may occur from trauma to the floor of the mouth, including iatrogenic trauma from surgical procedures. This report will present a case of a pseudoaneurysm of the lingual artery following tonsillectomy. Development of lingual artery pseudoaneurysms can occur within a few hours following tonsillectomy. Angiography provides the diagnosis, and endovascular intervention is an efficient alternative to surgery for treatment of such aneurysm with low morbidity. Endovascular embolization with platinum coils is an effective means of controlling bleeding and avoiding surgical intervention.

Castles or boarding-houses: a new concept of security

Current concepts of security, even if valid in the past, are inappropriate now. We need a new concept of security based on co-operation and interdependence, not military (and especially nuclear) confrontation. The International Court of Justice Advisory Opinion on the legality of nuclear weapons, international concern on the dangers of the arms trade, the landmines campaign, and statements by retired military leaders, are all signs of hope. But others, including non-governmental organizations, must also learn to co-operate. The Year of the Culture of Peace is an opportunity to make co-operation more effective and, particularly in schools, to make the United Nations better known and better appreciated.

Understanding attitudes towards tissue donation

Nurses discussing organ or tissue donation with patients and their relatives need to be well informed. Tissue donation is not being optimised. The attitude of health professionals towards organ and tissue donation can influence the relatives' decision.

Conflicting attitudes to corneal and organ donation: a study of nurses' attitudes to organ donation

The demand for transplantable organs and tissues is steadily increasing and action is necessary to improve the organ and tissue donation rates. Previous research has suggested that nurses have a substantial influence on the rates of donation in the clinical area. Nurses (N = 150) were asked to complete a number of measures to assess positive and negative attitudes towards cadaveric organ donation, with 112 (74.6%) responding. The findings identified conflicting attitudes particularly in relation to corneal donation; 25% of the respondents would not donate their corneas. Reasons given included fear of disfigurement, religious factors such as the need to see into the next life, and dislike of the thought of donation of eyes but without knowing why. The majority of the respondents were in favour of donation generally and many carried or had signed donor cards. Nurses are usually the professionals who have the most contact with the patient in the clinical and are therefore able to identify potential donors. It seems likely that nurses with conflicting attitudes to donation are less likely to undertake the emotional costs involved when relatives of potential donors are approached re donation, than those who have more positive attitudes.

Effect of phenytoin on acute lung injuries in unanesthetized sheep

OBJECTIVE

To determine if the intravenous administration of phenytoin attenuates or prevents acute experimental lung injury.

DESIGN

Placebo-controlled, longitudinal animal investigative study.

SETTING

University research laboratory.

SUBJECTS

Sixteen yearling female lambs weighing 30 +/- 3 kg.

INTERVENTION

After administration of anesthesia, the animals were endotracheally intubated and mechanically ventilated. Using sterile techniques, four thoracotomies were performed. Through the left fourth intercostal space, cannulas for pressure measurements were inserted directly into the main pulmonary artery and left atrium. An ultrasound flow cuff for determination of cardiac output was placed around the main pulmonary artery. Through the left tenth intercostal space, the diaphragmatic and mediastinal parietal pleura were widely cauterized. Through the right tenth intercostal space, the caudal mediastinal lymph node was identified and divided at the caudal margin of the right pulmonary ligament, and a 1- to 2-cm portion of the node distal to the ligament was resected. The diaphragmatic and mediastinal parietal pleura were widely cauterized. Through the right sixth intercostal space, the efferent duct (or ducts) was identified, ligated at the site of entry into the thoracic duct, and cannulated. The lymph cannula was brought to the outside of the thorax through a separate stab wound.

MEASUREMENTS AND MAIN RESULTS

Unanesthetized sheep were studied 7 to 10 days after surgery. Hemodynamic, lung fluid balance, and arterial blood variables were measured in uninjured sheep and in sheep injured by intravenous infusions of Escherichia coli endotoxin (1 microgram/kg iv over 30 mins), air bubbles (0.056 to 0.074 mL/kg/min over 4 hrs), or oleic acid (0.06 mL/kg over 1 hr). The sheep were studied when untreated and after pretreatment with phenytoin. We found that the expected increase in protein-rich lung lymph flow with injuries, resulting from increased microvascular permeability in the lungs, was attenuated by phenytoin when the lungs were injured by endotoxin or air bubbles. In contrast, phenytoin had no effect on oleic acid-induced lung injury or on uninjured lungs.

CONCLUSIONS

Phenytoin attenuates acute lung injuries in sheep that are thought to be caused by stimulation of host inflammatory responses (e.g., endotoxin and air bubbles), but has no effect on direct injuries to the lungs (e.g., oleic acid). A plausible mechanism for this finding is phenytoin inhibition of polymorphonuclear leukocyte function.

Proteolytic activity in sheep lung lymph as marker of lung capillary injury

Intravenous infusions of Escherichia coli endotoxin into sheep caused the appearance in lung lymph of high levels of an enzyme with trypsinlike activity. The time course of appearance of the enzyme and the extent of its increase corresponded to the known events of endotoxin-induced capillary injury. Accordingly, activity was low in the first phase of endotoxin-induced increased lung lymph flow caused by increased pressure filtration but was high in the second phase of increased lung lymph flow caused by increased permeability filtration. Recovery was associated with a decrease of activity to preinfusion levels. Capillary damage and increased permeability filtration induced by air emboli or oleic acid led to a similar increase in lung lymph proteolytic activity. By contrast lung lymph proteolytic activity remained virtually unchanged during increased pressure filtration induced by inflation of a balloon in the left atrium. Activity also remained unchanged in thoracic duct lymph, indicating that the increased activity in lung lymph is not an expression of a generalized response to endotoxin. The enzyme, a serine protease with a molecular weight of about 70,000 to 75,000 and a pH optimum between 7.3 and 7.6, was not related to lymph clotting and was not capable of correcting the clotting defects of plasmas deficient in enzymes of the clotting cascade. These results together with specificity studies indicate that the enzyme represents a new, hitherto unidentified, protease. Measurements of its activity in lung lymph represent a sensitive marker of lung capillary injury.

Factors related to physical therapy students' decisions to work with elderly patients

The purpose of this study was to determine the factors related to physical therapy students' decisions to work with elderly patients subsequent to graduation. Questionnaires, distributed to students in graduating classes of seven entry-level master's degree programs and seven baccalaureate degree programs, were returned by 326 participants. The questionnaires included 20 questions within four categories--biographical (3), experiential (7), perceived socioeconomic (3), and attitudinal (7) factors--plus 1 question to determine whether students intended to work with elderly patients. Chi-square tests (p less than .05) determined significant relationships between the participants' intentions to work with elderly people and their answers to 10 of the questions (1 biographical, 3 experiential, and 6 attitudinal). The answers to 1 of these experiential questions and 4 of these attitudinal questions were significant at the .001 level. No perceived socioeconomic questions were significant. Our results may help in planning strategies to encourage physical therapy students to work with elderly people.

Thermographic evaluation of the painful shoulder in the hemiplegic patient

In this study, we investigated the applicability of thermography as a technique for evaluating the painful postcerebrovascular accident (CVA) shoulder in hemiplegic patients. A thermographic series was taken of the upper extremities and upper trunk of 27 female subjects. The four groups we evaluated were nonhemiplegic subjects (n = 9), post-CVA subjects with recovered function (n = 6), hemiplegic subjects with upper extremity motor impairment (n = 6), and hemiplegic subjects with both motor impairment and ipsilateral shoulder pain (n = 6). The data revealed a normal thermographic series in 8 of the 9 nonhemiplegic subjects, but only in 1 of the 18 post-CVA subjects. The majority of the abnormal thermographic series of post-CVA subjects showed a 1 degree to 5 degree C coolness on the involved side. No consistent thermographic patterns emerged that could be related to the severity or location of pain. Further studies are needed to evaluate the efficacy of thermography as a means of determining the relationship between ipsilateral post-CVA coolness and hemiplegic shoulder pain.

Blood flow changes at the wrist in manual workers after preventive interventions

Radial and ulnar artery circulatory changes at the wrist were studied at the work site in manual workers performing repetitive tasks to compare the effects of two preventive interventions, exercise and rest. The Doppler method was used for assessment of blood flow velocity, and systolic blood pressure measurements were made on 16 right hand-dominant female workers in a suture manufacturing industry. Radial and ulnar blood flow velocity decreased while systolic blood pressure at these arteries remained stable after 1 1/2 hours of manual work. After 5-minute interventions of either exercise or rest, blood flow velocity increased, radial blood pressure remained stable, and ulnar blood pressure decreased. A 5-minute exercise program produced greater increases in radial blood flow velocity than did a 5-minute rest program. Brief exercise programs have been shown to improve circulation at the wrist after circulation was compromised by the performance of manual work. Such programs may offer one practical method of preventing soft tissue injuries related to the sustained compromise of blood flow at the wrist.

Improvement of quantitation of biological X-ray microanalysis

Absolute measurements of elemental concentrations within thin biological samples are often made by reference to a series of standards which resemble the samples in chemical and physical properties and the linear relationship between (p-b)/c and concentration. This principle requires that the chemical and physical properties of the matrix remain constant throughout a series of standards with different elemental contents and throughout different regions of the samples. Some of the changes undergone by specimens during X-ray microanalysis, e.g. loss of elements or organic mass loss, are also influenced by the composition of the matrix. A simple empirical modification to the linear (p-b)/c versus concentration relationship is presented to account for some of these effects and therefore improve quantitation of analyses.

Blood flow in the rectal gland of Squalus acanthias

The percent of cardiac output distributed to the rectal gland of 33 free-swimming fish was quantitated by the isotopically labeled microsphere technique. In 21 fish less than 1% was found in the rectal gland; 12 fish had 2-7%, suggesting a pattern of intermittent blood flow. Methylmethacrylate corrosion casts were made for scanning electron microscopy study of the microvasculature. Blood entering the rectal gland artery is distributed via three pathways. The most extensive is along the rectal gland artery into 11 or 12 circumferential vessels, which branch along the capsule and give rise to the radially arranged sinusoids that perfuse the secretory tubules and then join to form the central rectal gland vein. A second is an arterial bypass that runs the length of the rectal gland and joins the circulation of the postvalvular intestine. The third is via arteriovenous anastomoses in the capsule between tightly packed small arteries and veins. The low to moderate blood flow in most rectal glands and the very high flow in others is consistent with the observation that in vivo the rectal gland secretes only intermittently. Blood pathways allowing bypass of the rectal gland parenchyma suggest a role of blood flow in the regulation of the secretory process.

Quantitative ion localization within Suaeda maritima leaf mesophyll cells

Grown under saline conditions, Suaeda maritima accumulates Na(+) and Cl(-) into its leaves, where individual mesophyll cells behave differently in their compartmentation of these ions. Measurements of ion concentrations within selected subcellular compartments show that freeze-substitution with dry sectioning is a valuable preparative technique for analytical electron microscopy of highly vacuolate plant material. Using this approach, absolute estimates were made of Na(+), K(+) and Cl(-) concentrations in the cytoplasm, cell walls, chloroplasts and vacuoles of leaf mesophyll cells.

The microvasculature of the elasmobranch gill

Corrosion replicas were made of the gill vasculature of the spiny dogfish shark (S. acanthias) and little skate (R. erinacea) by methylmethacrylate perfusion via the ventral or dorsal aorta at 2.0-5.3 kPa. After tissue maceration the replicas were examined by light and scanning electron microscopy. In both species 3 vascular pathways were found: (1) the major pathway subserving the respiratory function of the gill, consisting of the afferent filamental artery which feeds into a medial afferent sinus (MA) from which arise the prelamellar arterioles (AL) leading to the lamellae, the postlamellar arterioles and efferent filamental artery (EA); (2) a nutrient circulation arising from the EA, supplying oxygenated blood to the filamental tissue, and anastomosing with the interlamellar vessels (IL); (3) a collateral circulation consisting of ILs which drain through channels interdigitating with the ALs and which then form a collateral reticulum, beneath the water channel epithelium, with vessels from the adjacent filaments. In the dogfish, small prelamellar arteriovenous anastomoses (PA) connect the MAs to the ILs with the same frequency as the ALs. PAs have not been found in the skate, but the efferent nutrient circulation is much more extensively developed. Many similarities exist between the elasmobranchs and teleosts in regard to the microvascular organization of the gill.

Isoflurane anesthesia and pressure antagonism in mice

The anesthetic partial pressure causing a loss of righting reflex in mice (ED50) was determined for isoflurane at ambient total pressures ranging from 1 to 100 atmospheres absolute (ATA). The higher pressures, produced by adding helium, decreased isoflurane's apparent anesthetic effect: 48 percent more was needed at 100 ATA. This is consistent with previous work with N2O, where a 46 percent increase was found. The ED50 for isoflurane at 1 ATA is 0.0057 ATA, only 29 percent of that predicted by the Meyer-Overton relationship for mice.