Improving management of ARDS: uniting acute management and long-term recovery.

Acute Respiratory Distress Syndrome (ARDS) is an important global health issue with high in-hospital mortality. Importantly, the impact of ARDS extends beyond the acute phase, with increased mortality and disability for months to years after hospitalization. These findings underscore the importance of extended follow-up to assess and address the Post-Intensive Care Syndrome (PICS), characterized by persistent impairments in physical, cognitive, and/or mental health status that impair quality of life over the long-term. Persistent muscle weakness is a common physical problem for ARDS survivors, affecting mobility and activities of daily living. Critical illness and related interventions, including prolonged bed rest and overuse of sedatives and neuromuscular blocking agents during mechanical ventilation, are important risk factors for ICU-acquired weakness. Deep sedation also increases the risk of delirium in the ICU, and long-term cognitive impairment. Corticosteroids also may be used during management of ARDS, particularly in the setting of COVID-19. Corticosteroids can be associated with myopathy and muscle weakness, as well as prolonged delirium that increases the risk of long-term cognitive impairment. The optimal duration and dosage of corticosteroids remain uncertain, and there's limited long-term data on their effects on muscle weakness and cognition in ARDS survivors. In addition to physical and cognitive issues, mental health challenges, such as depression, anxiety, and post-traumatic stress disorder, are common in ARDS survivors. Strategies to address these complications emphasize the need for consistent implementation of the evidence-based ABCDEF bundle, which includes daily management of analgesia in concert with early cessation of sedatives, avoidance of benzodiazepines, daily delirium monitoring and management, early mobilization, and incorporation of family at the bedside. In conclusion, ARDS is a complex global health challenge with consequences extending beyond the acute phase. Understanding the links between critical care management and long-term consequences is vital for developing effective therapeutic strategies and improving the quality of life for ARDS survivors.

A systematic review and meta-analysis of the clinimetric properties of the core outcome measurement instruments for clinical effectiveness trials of nutritional and metabolic interventions in critical illness (CONCISE).

BACKGROUND: CONCISE is an internationally agreed minimum set of outcomes for use in nutritional and metabolic clinical research in critically ill adults. Clinicians and researchers need to be aware of the clinimetric properties of these instruments and understand any limitations to ensure valid and reliable research. This systematic review and meta-analysis were undertaken to evaluate the clinimetric properties of the measurement instruments identified in CONCISE. METHODS: Four electronic databases were searched from inception to December 2022 (MEDLINE via Ovid, EMBASE via Ovid, CINAHL via Healthcare Databases Advanced Search, CENTRAL via Cochrane). Studies were included if they examined at least one clinimetric property of a CONCISE measurement instrument or recognised variation in adults ≥ 18 years with critical illness or recovering from critical illness in any language. The COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist for systematic reviews of Patient-Reported Outcome Measures was used. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses were used in line with COSMIN guidance. The COSMIN checklist was used to evaluate the risk of bias and the quality of clinimetric properties. Overall certainty of the evidence was rated using a modified Grading of Recommendations, Assessment, Development and Evaluation approach. Narrative synthesis was performed and where possible, meta-analysis was conducted. RESULTS: A total of 4316 studies were screened. Forty-seven were included in the review, reporting data for 12308 participants. The Short Form-36 Questionnaire (Physical Component Score and Physical Functioning), sit-to-stand test, 6-m walk test and Barthel Index had the strongest clinimetric properties and certainty of evidence. The Short Physical Performance Battery, Katz Index and handgrip strength had less favourable results. There was limited data for Lawson Instrumental Activities of Daily Living and the Global Leadership Initiative on Malnutrition criteria. The risk of bias ranged from inadequate to very good. The certainty of the evidence ranged from very low to high. CONCLUSIONS: Variable evidence exists to support the clinimetric properties of the CONCISE measurement instruments. We suggest using this review alongside CONCISE to guide outcome selection for future trials of nutrition and metabolic interventions in critical illness. TRIAL REGISTRATION: PROSPERO (CRD42023438187). Registered 21/06/2023.

Core outcome measures for clinical effectiveness trials of nutritional and metabolic interventions in critical illness: an international modified Delphi consensus study evaluation (CONCISE).

BACKGROUND: Clinical research on nutritional and metabolic interventions in critically ill patients is heterogenous regarding time points, outcomes and measurement instruments used, impeding intervention development and data syntheses, and ultimately worsening clinical outcomes. We aimed to identify and develop a set of core outcome domains and associated measurement instruments to include in all research in critically ill patients. METHODS: An updated systematic review informed a two-stage modified Delphi consensus process (domains followed by instruments). Measurement instruments for domains considered 'essential' were taken through the second stage of the Delphi and a subsequent consensus meeting. RESULTS: In total, 213 participants (41 patients/caregivers, 50 clinical researchers and 122 healthcare professionals) from 24 countries contributed. Consensus was reached on time points (30 and 90 days post-randomisation). Three domains were considered 'essential' at 30 days (survival, physical function and Infection) and five at 90 days (survival, physical function, activities of daily living, nutritional status and muscle/nerve function). Core 'essential' measurement instruments reached consensus for survival and activities of daily living, and 'recommended' measurement instruments for physical function, nutritional status and muscle/nerve function. No consensus was reached for a measurement instrument for Infection. Four further domains met criteria for 'recommended,' but not 'essential,' to measure at 30 days post-randomisation (organ dysfunction, muscle/nerve function, nutritional status and wound healing) and three at 90 days (frailty, body composition and organ dysfunction). CONCLUSION: The CONCISE core outcome set is an internationally agreed minimum set of outcomes for use at 30 and 90 days post-randomisation, in nutritional and metabolic clinical research in critically ill adults.

Management of COVID-19 ICU-survivors in primary care: - a narrative review.

Many survivors of critical illness suffer from long-lasting physical, cognitive, and mental health sequelae. The number of affected patients is expected to markedly increase due to the COVID-19 pandemic. Many ICU survivors receive long-term care from a primary care physician. Hence, awareness and appropriate management of these sequelae is crucial. An interdisciplinary authorship team participated in a narrative literature review to identify key issues in managing COVID-19 ICU-survivors in primary care. The aim of this perspective paper is to synthesize important literature to understand and manage sequelae of critical illness due to COVID-19 in the primary care setting.

Surviving critical illness: what is next? An expert consensus statement on physical rehabilitation after hospital discharge.

BACKGROUND: The study objective was to obtain consensus on physical therapy (PT) in the rehabilitation of critical illness survivors after hospital discharge. Research questions were: what are PT goals, what are recommended measurement tools, and what constitutes an optimal PT intervention for survivors of critical illness? METHODS: A Delphi consensus study was conducted. Panelists were included based on relevant fields of expertise, years of clinical experience, and publication record. A literature review determined five themes, forming the basis for Delphi round one, which was aimed at generating ideas. Statements were drafted and ranked on a 5-point Likert scale in two additional rounds with the objective to reach consensus. Results were expressed as median and semi-interquartile range, with the consensus threshold set at ≤0.5. RESULTS: Ten internationally established researchers and clinicians participated in this Delphi panel, with a response rate of 80 %, 100 %, and 100 % across three rounds. Consensus was reached on 88.5 % of the statements, resulting in a framework for PT after hospital discharge. Essential handover information should include information on 15 parameters. A core set of outcomes should test exercise capacity, skeletal muscle strength, function in activities of daily living, mobility, quality of life, and pain. PT interventions should include functional exercises, circuit and endurance training, strengthening exercises for limb and respiratory muscles, education on recovery, and a nutritional component. Screening tools to identify impairments in other health domains and referral to specialists are proposed. CONCLUSIONS: A consensus-based framework for optimal PT after hospital discharge is proposed. Future research should focus on feasibility testing of this framework, developing risk stratification tools and validating core outcome measures for ICU survivors.

Post-traumatic stress disorder symptoms after acute lung injury: a 2-year prospective longitudinal study.

BACKGROUND: Survivors of critical illnesses often have clinically significant post-traumatic stress disorder (PTSD) symptoms. This study describes the 2-year prevalence and duration of PTSD symptoms after acute lung injury (ALI), and examines patient baseline and critical illness/intensive care-related risk factors. METHOD: This prospective, longitudinal cohort study recruited patients from 13 intensive care units (ICUs) in four hospitals, with follow-up 3, 6, 12 and 24 months after ALI onset. The outcome of interest was an Impact of Events Scale - Revised (IES-R) mean score ≥1.6 ('PTSD symptoms'). RESULTS: During the 2-year follow-up, 66/186 patients (35%) had PTSD symptoms, with the greatest prevalence by the 3-month follow-up. Fifty-six patients with post-ALI PTSD symptoms survived to the 24-month follow-up, and 35 (62%) of these had PTSD symptoms at the 24-month follow-up; 50% had taken psychiatric medications and 40% had seen a psychiatrist since hospital discharge. Risk/protective factors for PTSD symptoms were pre-ALI depression [hazard odds ratio (OR) 1.96, 95% confidence interval (CI) 1.06-3.64], ICU length of stay (for a doubling of days, OR 1.39, 95% CI 1.06-1.83), proportion of ICU days with sepsis (per decile, OR 1.08, 95% CI 1.00-1.16), high ICU opiate doses (mean morphine equivalent ≥100 mg/day, OR 2.13, 95% CI 1.02-4.42) and proportion of ICU days on opiates (per decile, OR 0.83, 95% CI 0.74-0.94) or corticosteroids (per decile, OR 0.91, 95% CI 0.84-0.99). CONCLUSIONS: PTSD symptoms are common, long-lasting and associated with psychiatric treatment during the first 2 years after ALI. Risk factors include pre-ALI depression, durations of stay and sepsis in the ICU, and administration of high-dose opiates in the ICU. Protective factors include durations of opiate and corticosteroid administration in the ICU.

Evaluation of two delirium screening tools for detecting post-operative delirium in the elderly.

BACKGROUND: Postoperative delirium in the elderly is common and associated with poor outcomes, but often goes unrecognized. Delirium screening tools, validated in postoperative settings are lacking. This study compares two screening tools [Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) and Nursing Delirium Symptom Checklist (NuDESC)] with a DSM-IV-based diagnosis of delirium, conducted by neuropsychiatric examination in postoperative settings. METHODS: Consecutive English-speaking patients, ≥70 yr, undergoing surgery with general anaesthesia and capable of providing informed consent, were recruited. Diagnostic test characteristics were compared for each screening tool vs neuropsychiatric examination, both in the Post-Anaesthesia Care Unit (PACU), and daily during inpatient hospitalization, adjusting for repeated measures. RESULTS: Neuropsychiatric examination identified delirium in 45% of 91 patients evaluated in the PACU and in 32% of 166 subsequent delirium assessments on the ward in the 58 admitted patients. The sensitivity [95% confidence interval (CI)] of delirium detection of the CAM-ICU in the PACU, and in all repeated assessments was 28% (16-45%) and 28% (17-42%), respectively; for the NuDESC (scoring threshold ≥2), 32% (19-48%) and 29% (19-42%), respectively, and the NuDESC (threshold ≥1), 80% (65-91%) and 72% (60-82%), respectively. Specificity was >90% for both the CAM-ICU and the NuDESC (threshold ≥2); specificity for the NuDESC (threshold ≥1), in the PACU was 69% (54-80%) and 80% (73-85%) for all assessments. CONCLUSIONS: While highly specific, neither CAM-ICU nor NuDESC (threshold ≥2) are adequately sensitive to identify delirium post-operatively; NuDESC (threshold ≥1) increases sensitivity, but reduces specificity.

The south-east Scotland dermatology workload study: 30 years' analysis.

BACKGROUND: Dermatological activity data have been collected for the same region of south-east Scotland (population 1·24 million), approximately every 5 years, since 1981. This has allowed assessment of trends in demand from primary and secondary care, and activity within secondary care dermatology services, assisting planning of dermatological services. OBJECTIVES: To quantify dermatology outpatient workload across the same population to allow comparison with previous studies for trends in practice. METHODS: During November 2010, a standardized proforma was completed for all National Health Service and private practice dermatology outpatient consultations. Demographic data, source and reason for referral, diagnoses, investigations, treatments and disposal were recorded, and comparisons made with five previous studies. RESULTS: A total of 5470 consultations were recorded: 2882 new and 2588 review patients (new to review ratio 1 : 0·9, male to female 1 : 1·3, mean age 49 years, range 1 month to 101 years). Ninety-one per cent of referrals came from primary care and 9% from secondary care. Fifty-eight per cent of referrals were for diagnosis and 32% for hospital management. Diagnostic concordance between referrer and dermatologist ranged from 94% for acne to 14% for melanoma. Benign tumours accounted for 30% of referrals, malignant tumours 13%, dermatitis 13·3%, psoriasis 6·2% and acne/rosacea 5%. The referral rate rose to 23·2/1000 population per annum, with the increase coming mainly from primary care. CONCLUSIONS: Demand for dermatology continues to increase: new referrals have risen by 134% in 30 years, with a 36% increase in the last 5 years, despite corresponding population increases of 5·3% and 3%, respectively.

Biomembrane templates for nanoscale conduits and networks.

Long nanotubes of fluid-lipid bilayers can be used to create templates for photochemical polymerization into solid-phase conduits and networks. Each nanotube is pulled from a micropipette-held feeder vesicle by mechanical retraction of the vesicle after molecular bonding to a rigid substrate. The caliber of the tube is controlled precisely in a range from 20 to 200 nanometers merely by setting the suction pressure in the micropipette. Branched conduits can be formed by coalescing separate nanotubes drawn serially from the feeder vesicle surface. Single nanotubes and nanotube junctions can be linked together between bonding sites on a surface to create a functionalized network. After assembly, the templates can be stabilized by photoinitiated radical cross-linking of macromonomers contained in the aqueous solution confined by the lipid bilayer boundary.

A new temperature-sensitive liposome for use with mild hyperthermia: characterization and testing in a human tumor xenograft model.

The single biggest challenge now facing drug delivery (for liposomes and indeed other carriers) is to initiate and produce release of the encapsulated drug only at the diseased site and at controllable rates. Our efforts have focused on developing a new thermal-sensitive drug delivery system, specifically for the local control of solid tumors. We describe here a new lipid formulation containing doxorubicin that has been optimized for both mild hyperthermic temperatures (39 degrees C to 40 degrees C) that are readily achievable in the clinic and rapid release times of drug (tens of seconds). This new liposome, in combination with mild hyperthermia, was found to be significantly more effective than free drug or current liposome formulations at reducing tumor growth in a human squamous cell carcinoma xenograft line (FaDu), producing 11 of 11 complete regressions lasting up to 60 days posttreatment.

Increased microvascular permeability contributes to preferential accumulation of Stealth liposomes in tumor tissue.

Stealth liposomes have recently emerged as a promising antitumor drug delivery system, yet no studies have been reported to examine their dynamic behavior at the microcirculatory level. In this investigation, we have used in vivo fluorescence videomicroscopy to study the decay in plasma concentration and the interstitial accumulation of Stealth and conventional liposomes in tumor and granulating tissue microcirculatory preparations. Fluorescently labeled Stealth or conventional liposomes were injected i.v. into rats bearing dorsal skinflap window chambers, some of which contained a vascularized mammary adenocarcinoma. After injection, fluorescent light intensities arising from liposomes within blood vessels and the interstitium were measured over time. These measurements were used to derive plasma pharmacokinetics and vascular permeability coefficients for each liposome species in both tumor and granulating normal tissues. Within the first 90 min after injection, Stealth liposome accumulation in the tumor interstitium was 3-4-fold that for conventional liposomes. The percentage of administered liposomes remaining in the circulation at the end of 90 min was 60.2% for Stealth and 20.4% for conventional liposomes. Tumor vascular permeability was 3.42 +/- 0.78 x 10(-7)cm/s for Stealth and 1.75 x 0.38 x 10(-7)cm/s for conventional liposomes. In normal granulating tissues permeability for the 2 constructs was equivalent at 0.8-0.9 x 10(-7)cm/s. In conclusion, preferential accumulation of Stealth liposomes in tumors was attributable to a combination of slower plasma clearance and higher vascular permeability relative to conventional liposomes. Our method of combining in vivo microscopy with a tumor microcirculatory model provides a unique approach to study quantitatively the delivery of liposomes to tumor tissues, since it can be used to study the process in real time at the microcirculatory level.

Efficacy of liposomes and hyperthermia in a human tumor xenograft model: importance of triggered drug release.

The tumor drug concentrations, drug distributions, and therapeutic efficacies achieved by three fundamentally different liposomes, nonthermosensitive liposome (NTSL), traditional thermosensitive liposome (TTSL), and low temperature sensitive liposome (LTSL); free doxorubicin (DOX); and saline in combination with hyperthermia (HT) were directly compared in a human tumor xenograft model. NTSL is a nonthermosensitive liposome in the physiological temperature range, TTSL is a traditional thermosensitive liposome that triggers in the range of approximately 42-45 degrees C and releases drug over approximately 30 min, and LTSL is a new low temperature sensitive liposome that triggers in the range of approximately 39-40 degrees C and releases drug in a matter of seconds. Because of the different attributes of the liposomes, it was possible to delineate the relative importance of liposome drug encapsulation, HT cytotoxicity, HT-drug interaction, HT-induced liposomal delivery, and HT-triggered liposomal drug release in achieving antitumor activity. Athymic nude mice bearing the FaDu human tumor xenograft were given a single i.v. dose of 5 mg/kg of DOX (free drug or liposome encapsulated), and the tumors were then heated to either 34 degrees C or 42 degrees C for 1 h at 34 degrees C. All treatment groups were similar, achieving low concentrations of DOX (0-4.5 ng/mg). At 42 degrees C, the LTSL (25.6 ng/mg) achieved the highest DOX concentration (P < 0.04), but all three liposomal formulations (7.3-25.6 ng/mg) were higher than saline or DOX (0-0.7 ng/mg; P < 0.02). LTSL + HT was also the only group that resulted in significant amounts of DNA-bound DOX (silver nitrate-extractable fraction; P < 0.02). Tumor tissue sections were visualized for DOX fluorescence to investigate the local distribution of the drug in the tumor and confirm the relative drug concentrations based on fluorescence intensity. There was relatively little fluorescence seen with treatment groups at 34 degrees C. At 42 degrees C, the LTSL showed the most DOX fluorescence (P < 0.01), and the fluorescence, although not homogeneous, was pervasive throughout the tumor sections. Therapeutic efficacy of treatments was determined from tumor growth time. At 34 degrees C, the only treatment group significantly better than the saline group (9.8 days) was the NTSL group, with a growth time of 20.9 days (P < 0.02). At 42 degrees C, all three liposomal formulations were more efficacious than DOX. LTSL + HT had the longest growth time (51.4 days) and the most number of local controls at 60 days (six of nine tumors). With HT, the DOX concentrations and fluorescence were tightly correlated with tumor growth delay, indicating that adequate (increased) drug delivery can be predictive of therapeutic effect. Overall, the LTSL + HT group showed the largest DOX concentration, the highest and most pervasive DOX fluorescence, and the most antitumor effect. Thus, HT-triggered liposomal drug release may account for the largest differential therapeutic effect and demonstrates the importance of rapid drug release from the drug carriers at the tumor site.

The effect of augmenting early nutritional energy delivery on quality of life and employment status one year after ICU admission.

Augmenting energy delivery during the acute phase of critical illness may reduce mortality and improve functional outcomes. The objective of this sub-study was to evaluate the effect of early augmented enteral nutrition (EN) during critical illness, on outcomes one year later. We performed prospective longitudinal evaluation of study participants, initially enrolled in The Augmented versus Routine approach to Giving Energy Trial (TARGET), a feasibility study that randomised critically ill patients to 1.5 kcal/ml (augmented) or 1.0 kcal/ml (routine) EN administered at the same rate for up to ten days, who were alive at one year. One year after randomisation Short Form-36 version 2 (SF-36v2) and EuroQol-5D-5L quality of life surveys, and employment status were assessed via telephone survey. At one year there were 71 survivors (1.5 kcal/ml 38 versus 1.0 kcal/ml 33; P=0.55). Thirty-nine (55%) patients consented to this follow-up study and completed the surveys (n = 23 and 16, respectively). The SF-36v2 physical and mental component summary scores were below normal population means but were similar in 1.5 kcal/ml and 1.0 kcal/ml groups (P=0.90 and P=0.71). EuroQol-5D-5L data were also comparable between groups (P=0.70). However, at one-year follow-up, more patients who received 1.5 kcal/ml were employed (7 versus 2; P=0.022). The delivery of 1.5 kcal/ml for a maximum of ten days did not affect self-rated quality of life one year later.

Tension-stabilized pores in giant vesicles: determination of pore size and pore line tension.

We present the first observations of giant, long-existing, stabilized pores in vesicle membranes. Using a new experimental technique for studying the electro-permeabilization of lipid membranes, giant liposomes (from 25 to 56 microns in diameter) were subjected to single, square, electric pulses (duration 150 microseconds and electric field strength from 63 to 126 kV/m). The liposomes were held by a micropipet and small membrane tensions were created by controlling the pipet suction pressure. The liposomes were loaded with media having different refractive index from the outside solution, and, under these conditions, the formation of pores in the pressurized liposome could be visualized by the jet of inside solution that flowed out from the membrane pore. By adjusting the membrane tension, pores were kept open, and pore lifetimes could be varied from tenths of a second to several seconds. The pore size was determined from the volumetric flow in the pore region and the measured pressure differences across the bilayer. It was clear from the experiments that only one pore remained opened after the pulse. The estimated pore radii were on the order of one micrometer. The pores were in a quasi-stationary state and when they closed they did so spontaneously in a quick process (in milliseconds). The isotropic membrane tension was determined for the same measurements and from determinations of both pore size and dynamic membrane tension the pore line tension was found. The line tension of the pore region was determined for two lipid compositions, stearoyl-oleoylphosphatidylcholine and stearoyl-oleoylphosphatidylcholine with 50 mol% cholesterol, and the obtained values for single bilayers were (0.92 +/- 0.07) x 10(-11) N and (3.05 +/- 0.12) x 10(-11) N, respectively.

Repulsive interactions and mechanical stability of polymer-grafted lipid membranes.

Liposome membranes containing lipids with covalently attached poly(ethylene glycol) (PEG-lipid) are currently being developed as drug delivery systems. These, so called, 'Stealth' liposomes have a relatively long half life (approximately 1 day) in blood circulation and show an altered biodistribution in vivo. The extended lifetime appears to result from a steric stabilization of the liposome by the grafted polymer. In order to characterize the surface structures that promote steric stability in such polymer-grafted lipid bilayer systems, we have used X-ray diffraction to measure the structural organization and interbilayer repulsion for lipid/cholesterol (2:1) bilayers incorporating 4 mol% of a PEG-lipid in which the molecular weight of the PEG moiety was 1900 g/mol. At this concentration, applied pressure versus interbilayer distance relations showed that the grafted polymer moiety extended approximately 50 A from the lipid surface and gave rise to a strong, slowly decaying repulsive pressure between membranes that opposed their close approach. Also, the pressure vs. distance relations were only modestly altered by changing the ionic strength of the medium (1 mM NaCl and 100 mM NaCl). Therefore, even though the PEG-lipid headgroup bears a negative charge, the long range pressure cannot be due primarily to an electrostatic double layer pressure. Measurements of lipid bilayer elasticity using micropipet manipulation showed that PEG-lipid did not change the cohesive properties of lipid/cholesterol liposomes which was consistent with the X-ray structural data showing that the PEG-lipid did not change the normal structure of the bilayer interior. From these data we conclude that the repulsive barrier properties of lipid-grafted PEG polymer chains originate mainly from a steric pressure and that this simple polymer steric stabilization is the basis for the extended in vivo circulation times observed for polymer-grafted liposomes.

The effects of bilayer thickness and tension on gramicidin single-channel lifetime.

Measurements have been made of gramicidin single-channel lifetimes in monoacylglycerol bilayers chosen so that their thickness ranged from above to below the length of the gramicidin channel. Contact angles, electrical capacities and bulk-phase interfacial tensions have also been determined for these systems. The mean channel lifetime decreased with the hydrocarbon thickness of the membrane until the latter reached 2.2 nm, after which the lifetime was relatively constant. A theoretical model has been proposed which relates the mean channel lifetime (or dissociation constant) to both the thickness and the tension of the bilayers. The analysis of the present results and of those of previous studies has led to the idea that aggregates of water molecules may play an important rôle in the dissociation of the gramicidin channel.

A quantitative explanation of the effects of some alcohols on gramicidin single-channel lifetime.

The effects of n-decanol, n-hexadecanol, n-octyl(oxyethylene)3 alcohol and cholesterol on gramicidin single-channel lifetime in planar lipid bilayers have been determined. The bilayers used were formed from a solution of monoolein in squalene. Measurements have also been made of the above compounds' effects on membrane thickness (as measured by electrical capacity and optical reflectance technique) and surface tension (as derived from bulk interfacial tension and bilayer-lens contact angle measurements). The reduction in single-channel lifetime caused by the n-alkanols may be accounted for quantitatively in terms of the effects of these compounds on bilayer thickness and surface tension. The n-octyl(oxyethylene)3 alcohol caused an increase in single-channel lifetime which is also consistent with the thickness/tension theory. The reduction in channel lifetime caused by cholesterol, however, was much larger than would be predicted from its effects on bilayer thickness and surface tension.

Hyperthermia increases accumulation of technetium-99m-labeled liposomes in feline sarcomas.

The effect of hyperthermia on the accumulation of technetium-99m-labeled liposomes was studied in feline sarcomas. Each cat received two separate injections of liposomes. The first was used to quantify the amount of technetium-99m-labeled liposomes within the tumor under normothermic conditions. The second injection was made at the beginning of a 60-min hyperthermia procedure. Planar scintigraphy was used to measure the activity of technetium-99m-labeled liposomes within the tumor at predetermined times up to 18 h after injection. Regions of interest were drawn for the tumor, lungs, liver, kidney, and aorta. Counts in the regions of interest were decay corrected. Counts/pixel in the tumor under normothermic and hyperthermic conditions were normalized to aorta counts/pixel. A total of 16 cats were eligible for the study. In two of the 16 cats, incomplete count data precluded analysis. In the remaining 14 cats, hyperthermia resulted in a significant increase in liposome accumulation in the tumor (P = 0.001). Tumor volume ranged from 1.2 to 236.2 cm3, and thermal dose ranged from 2.0 to 243.3 CEM43CT90 (equivalent time that the 10th percentile temperature was equal to 43 degrees C). There was not a relationship between either tumor volume or hyperthermia dose on the magnitude of increased liposome accumulation, suggesting that this method has application across a range of tumor volumes and degrees of heatibility.