Measurement of extravascular lung water to diagnose severe reperfusion lung injury following pulmonary endarterectomy: a prospective cohort clinical validation study.

The measurement of extravascular lung water is a relatively new technology which has not yet been well validated as a clinically useful tool. We studied its utility in patients undergoing pulmonary endarterectomy as they frequently suffer reperfusion lung injury and associated oedematous lungs. Such patients are therefore ideal for evaluating this new monitor. We performed a prospective observational cohort study during which extravascular lung water index measurements were taken before and immediately after surgery and postoperatively in intensive care. Data were analysed for 57 patients; 21 patients (37%) experienced severe reperfusion lung injury. The first extravascular lung water index measurement after cardiopulmonary bypass failed to predict severe reperfusion lung injury, area under the receiver operating characteristic curve 0.59 (95%CI 0.44-0.74). On intensive care, extravascular lung water index correlated most strongly at 36 h, area under the receiver operating characteristic curve 0.90 (95%CI 0.80-1.00). Peri-operative extravascular lung water index is not a useful measure to predict severe reperfusion lung injury after pulmonary endarterectomy, however, it does allow monitoring and measurement during the postoperative period. This study implies that extravascular lung water index can be used to directly assess pulmonary fluid overload and that monitoring patients by measuring extravascular lung water index during their intensive care stay is useful and correlates with their clinical course. This may allow directed, pre-empted therapy to attenuate the effects and improve patient outcomes and should prompt further studies.

A review of enhanced recovery for thoracic anaesthesia and surgery.

During the past decade, there has been a dramatic increase in the number of thoracic surgical procedures carried out in the UK. The current financial climate dictates that more efficient use of resources is necessary to meet escalating demands on healthcare. One potential means to achieve this is through the introduction of enhanced recovery protocols, designed to produce productivity savings by driving reduction in length of stay. These have been promoted by government bodies in a number of surgical specialties, including colorectal, gynaecological and orthopaedic surgery. This review focuses on aspects of peri-operative care that might be incorporated into such a programme for thoracic anaesthesia, for which an enhanced recovery programme has not yet been introduced in the UK, and a review of the literature specific to this area of practice has not been published before. We performed a comprehensive search for published work relating to the peri-operative management and optimisation of patients undergoing thoracic surgery, and divided these into appropriate areas of practice. We have reviewed the specific interventions that may be included in an enhanced recovery programme, including: pre-optimisation; minimising fasting time; thrombo-embolic prophylaxis; choice of anaesthetic and analgesic technique and surgical approach; postoperative rehabilitation; and chest drain management. Using the currently available evidence, the design and implementation of an enhanced recovery programme based on this review in selected patients as a package of care may reduce morbidity and length of hospital stay, thus maximising utilisation of available resources.

A novel MHC class I-like gene is mutated in patients with hereditary haemochromatosis.

Hereditary haemochromatosis (HH), which affects some 1 in 400 and has an estimated carrier frequency of 1 in 10 individuals of Northern European descent, results in multi-organ dysfunction caused by increased iron deposition, and is treatable if detected early. Using linkage-disequilibrium and full haplotype analysis, we have identified a 250-kilobase region more than 3 megabases telomeric of the major histocompatibility complex (MHC) that is identical-by-descent in 85% of patient chromosomes. Within this region, we have identified a gene related to the MHC class I family, termed HLA-H, containing two missense alterations. One of these is predicted to inactivate this class of proteins and was found homozygous in 83% of 178 patients. A role of this gene in haemochromatosis is supported by the frequency and nature of the major mutation and prior studies implicating MHC class I-like proteins in iron metabolism.

Oligomerized transferrin receptors are selectively retained by a lumenal sorting signal in a long-lived endocytic recycling compartment.

Cross-linking of surface receptors results in altered receptor trafficking in the endocytic system. To better understand the cellular and molecular mechanisms by which receptor cross-linking affects the intracellular trafficking of both ligand and receptor, we studied the intracellular trafficking of the transferrin receptor (TfR) bound to multivalent-transferrin (Tf10) which was prepared by chemical cross-linking of transferrin (Tf). Tf10 was internalized about two times slower than Tf and was retained four times longer than Tf, without being degraded in CHO cells. The intracellular localization of Tf10 was investigated using fluorescence and electron microscopy. Tf10 was not delivered to the lysosomal pathway followed by low density lipoprotein but remained accessible to Tf in the pericentriolar endocytic recycling compartment for at least 60 min. The retained Tf10 was TfR-associated as demonstrated by a reduction in surface TfR number when cells were incubated with Tf10. The presence of Tf10 within the recycling compartment did not affect trafficking of subsequently endocytosed Tf. Retention of Tf10 within the recycling compartment did not require the cytoplasmic domain of the TfR since Tf10 exited cells with the same rate when bound to the wild-type TfR or a mutated receptor with only four amino acids in the cytoplasmic tail. Thus, cross-linking of surface receptors by a multivalent ligand acts as a lumenal retention signal within the recycling compartment. The data presented here show that the recycling compartment labeled by Tf10 is a long-lived organelle along the early endosome recycling pathway that remains fusion accessible to subsequently endocytosed Tf.

Beta-very low density lipoprotein is sequestered in surface-connected tubules in mouse peritoneal macrophages.

beta-very low density lipoprotein (VLDL) is a large lipoprotein with multiple apoprotein E (apoE) molecules that bind to the LDL receptors on mouse macrophages. Even though they bind to the same receptor, the endocytic processing of beta-VLDL differs from low density lipoprotein (LDL). LDL is rapidly delivered to perinuclear lysosomes and degraded, but much of the beta-VLDL is retained in peripheral compartments for several minutes. We have investigated the properties of these peripheral compartments. Measurement of the pH was made using FITC-phosphatidylethanolamine incorporated into the beta-VLDL, and we found that the peripheral compartments were near neutral in pH. These peripheral, beta-VLDL containing compartments were poorly accessible to antibodies, but a low molecular weight fluorescence quencher (trypan blue) entered the compartments within a few seconds. Intermediate voltage EM of cells labeled with colloidal-gold-beta-VLDL revealed that the peripheral compartments are tubular, surface-connected invaginations. Kinetic studies with fluorescent beta-VLDL showed that the compartments become fully sealed with a half-time of 6 min, and the beta-VLDL is then delivered rapidly to perinuclear lysosomes. By monitoring fluorescence energy transfer between lipid analogs incorporated into the beta-VLDL, some processing of the lipoprotein in the peripheral tubular compartments is demonstrated. The novel mode of uptake of beta-VLDL may account for the high cholesterol ester accumulation induced by this lipoprotein.

The effects of human cytomegalovirus infection on cytoskeleton-associated polysomes.

Human cytomegalovirus (HCMV) infection induces disruption of the host cell's cytoskeleton (CSK). This disruption is accompanied by three transient phases of actin depolymerization that occur at 20 min, 5 to 10 h and 48 to 72 h post infection (pi). During the 20 min peak of actin depolymerization, the level of cellular polysomes associated with the CSK was reduced, due to release of ribosomes from CSK-associated polysomes. Cellular mRNAs previously existing in these polysomes, however, remained associated with the CSK. Also during this period, nuclear to cytoplasmic transport of host cellular mRNA as well as the association of newly synthesized mRNA with the CSK was temporarily delayed. By 60 min pi, ribosomes, preexisting host cellular mRNA, and newly synthesized mRNAs (host and viral) had reestablished a distribution in the infected cell comparable to that of uninfected cells. Sedimentation profiles of soluble and CSK fractions at various times throughout the viral infection indicated that, although the amount of polysomes associated with the CSK at 20 min pi was reduced, essentially all HCMV and all host cell polysomes present were associated with the CSK. The majority of HCMV DNA hybridizable poly(A)+ RNAs were associated with the CSK throughout the viral infection. These early events appear to correlate with a transient interruption of host cellular mRNA translation early in infection and may represent a process whereby HCMV gene expression becomes competitive with that of the host cell.

Cytoskeletal disruption during human cytomegalovirus infection of human lung fibroblasts.

Human cytomegalovirus (HCMV) infection causes a rapid, progressive disruption of the host cell cytoskeleton that correlates with actin depolymerization. Whole-mount (3D) electron microscopy was used to analyze the cytoskeleton of uninfected and HCMV-infected human lung fibroblast cells. Within 2 min of HCMV infection, localized areas of cytoskeletal disruption were observed. Disruption extended throughout the cytoplasm during the ensuing 45 to 90 min of infection and resulted in generalized cytoskeletal disorganization. Actin depolymerization occurred, as indicated by an increase in DNase I inhibition and alteration in the fluorescence pattern with rhodamine-conjugated phalloidin. Thus, actin appears to be the primary cytoskeletal target involved during HCMV infection. Fractionation of the virus seed inoculum showed that development of DNase I inhibitory activity in infected cells was associated only with the virus-containing fractions. Cytochalasin B treatment at early times of HCMV infection stimulated progeny virus production. This study demonstrates that rapid cytoskeletal disruption occurs during early periods of HCMV infection and indicates that actin depolymerization facilitates viral infectivity.

Oral and intravenous propranolol during exercise.

The intrinsic sinoatrial (SA) rate at rest and during exercise was measured in 5 normal male subjects after prolonged oral and acute intravenous administration of propranolol and atropine. At rest, the intrinsic SA rate was similar after both oral and intravenous propranolol. At the higher levels of power output on a cycle ergometer, cardiac rate was slower after oral than after intravenous propranolol. When the intravenous study was repeated with the use of an additional dose of propranolol, cardiac rate was lower at comparable levels of power output, but not as low as that after oral propanolol. Differences in responses were interpreted as reflecting varying degrees of beta blockade, the most complete being that after prolonged oral propranolol administration of 320 mg daily. The intravenous dose of propranolol usually used to obtain the "pharmacologically isolated heart" at rest is too small to induce full beta blockade in exercise.

Acute cocaine-induced seizures: differential sensitivity of six inbred mouse strains.

Mature male and female mice from six inbred stains were tested for susceptibility to behavioral seizures induced by a single injection of cocaine. Cocaine was injected ip over a range of doses (50-100 mg/kg) and behavior was monitored for 20 minutes. Seizure end points included latency to forelimb or hindlimb clonus, latency to clonic running seizure and latency to jumping bouncing seizure. A range of strain specific sensitivities was documented with A/J and SJL mice being most sensitive and C57BL/6J most resistant. DBA/2J, BALB/cByJ and NZW/LacJ strains exhibited intermediate sensitivity. EEG recordings were made in SJL, A/J and C57BL/6J mice revealing a close correspondence between electrical activity and behavior. Additionally, levels of cocaine determined in hippocampus and cortex were not different between sensitive and resistant strains. Additional studies of these murine strains may be useful for investigating genetic influences on cocaine-induced seizures.

Usefulness of weightlifting training in improving strength and maximal power output in coronary artery disease.

The effects of 10 weeks (20 sessions) of combined weightlifting and aerobic training (n = 10) were compared with the effects of aerobic training alone (n = 8) on indexes of strength and aerobic exercise capacity in 18 men with coronary artery disease (CAD). Initial test performance was similar between groups. After aerobic training, the maximal load that could be lifted once only (1-repetition maximum) in single-arm curl, single-leg press and single-knee extension exercises increased by 13% (11.8 to 13.3 kg; p less than 0.01), 4% (97.0 to 101.0 kg; difference not significant) and 5% (28.2 to 29.7 kg; difference not significant), respectively; corresponding gains with combined weightlifting and aerobic training were 43% (12.2 to 17.4 kg; p less than 0.01), 21% (99.0 to 120.0 kg; p less than 0.01) and 24% (29.0 to 36.0 kg; p less than 0.01). After aerobic training, the initial 1-repetition maximum could be lifted an average of 4 times, compared with 14 times after combined training. Maximal progressive incremental cycle ergometer power output increased by 2% in the aerobic control group (1,088 to 1,113 kpm/min; difference not significant) and by 15% (1,030 to 1,180 kpm/min; p less than 0.05) in the experimental group. Cycling time at 80% of initial maximal power before attaining a Borg (0 to 10) rating of perceived exertion of 7 (very severe) increased by 11% (604 to 672 seconds; difference not significant) and by 109% (541 to 1,128 seconds; p less than 0.05) in the control and weight-trained patients, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictors of dropout from cardiac exercise rehabilitation. Ontario Exercise-Heart Collaborative Study.

The Ontario Exercise-Heart Collaborative Study was a multicenter randomized clinical trial of high intensity exercise for the prevention of recurrent myocardial infarction in 733 men. Of the 678 subjects who could have participated for at least 3 years, 315 (46.5%) dropped out. Stepwise multiple linear logistic regression analysis was carried out to examine the relation between subject characteristics and the probability of dropping out during the study. Analysis was performed on the entry group as a whole by considering those subjects who had reinfarction while complying with the program and also by excluding all subjects with reinfarctions. The consistent and statistically significant predictors of dropout in both analyses were smoking and a blue collar occupation. Angina was significantly associated with dropout only when reinfarctions were excluded. It may be important to consider these factors when investigating the potential for compliance-improving strategies in reducing dropout from exercise rehabilitation programs.

Symptom intensity and subjective limitation to exercise in patients with cardiorespiratory disorders.

The aim of the study was to compare (1) the intensity of leg effort and dyspnea during exercise and (2) subjective limitations to performance in normal subjects, patients receiving medication for cardiac disorders, patients with pulmonary impairment, patients with pulmonary impairment who were also receiving cardiac medications, patients experiencing chest pain during exercise, and patients who had a reduced exercise capacity but did not have pulmonary impairment and were not receiving cardiac medication. Five hundred seventy-eight subjects rated the intensity of leg effort, discomfort with breathing (dyspnea), and chest pain every minute (Borg scale) during an incremental exercise task (100 kpm/min each minute) to maximum work capacity on a cycle ergometer and following exercise indicated their subjective limitation by completing a simple questionnaire. Leg effort and dyspnea increased systematically with power output in a positively accelerating manner in all groups; both symptoms were significantly more intense in the impaired groups compared with the normal group at submaximal power outputs. In all groups, there was a significant relationship between symptom intensity at submaximal power outputs and the maximal power output achieved. Leg discomfort in combination with breathing discomfort was the predominant subjective limitation in all groups; chest pain in combination with leg and breathing discomfort was the major subjective limitation in individuals with angina. Activation of the sensory systems during exercise is accompanied by a perception of discomfort associated with the peripheral exercising muscles and discomfort with breathing; both discomfort associated with the exercising muscles and discomfort associated with breathing contribute to exercise limitation to a large degree in normal subjects and patients with cardiorespiratory diseases.

Measurements of cardiac output in seriously ill patients using a CO2 rebreathing method.

A CO2 rebreathing method for the measurement of cardiac output was evaluated by comparison with the direct Fick O2 method in 26 studies performed in 18 patients who were critically ill. The method requires measurement of CO2 output by collection of expired gas, of arterial PCO2, and of mixed venous PCO2 by rebreathing. Twenty-five comparisons were within +/- 20% of the direct Fick measurements, at cardiac outputs varying between 1.4 and 6.4 L/min. Knowledge of the cardiac output increased the quality of the interpretation of arterial blood PO2 measurements in the assessment of pulmonary gas exchange disturbances.

Measurement of cardiac output by CO2 rebreathing in unsteady state exercise.

The ability to determine cardiac output (Q) noninvasively during a nonsteady state (NSS) incremental exercise test was assessed. Seven healthy subjects performed two maximal incremental cycle ergometer exercise tests (100 kpm/min increments every minute), and also steady state exercise (SS) at 25, 50, and 75 percent of their maximum power output. The Q was determined by the indirect CO2 Fick method; mixed venous PCO2 was calculated using the exponential CO2 rebreathing method. No significant differences were observed for the cardiac output/oxygen uptake relationship (Q/VO2) obtained between the two incremental exercise tests. During NSS, the Q/VO2 was linear (r = .89; intercept = 5.69 L/min; slope = 5.39). During the SS, Q/VO2 was linear (r = .90; intercept = 5.47 L/min; slope = 4.87). No significant difference was observed between the SS and NSS Q/VO2 relationships (p greater than 0.05), and the NSS relationship was similar to Q/VO2 values previously reported in the literature. Accurate and reproducible measurements of Q can be obtained noninvasively in healthy subjects using the exponential CO2 rebreathing method during incremental progressive exercise tests, with similar values at comparable VO2 to those obtained in the steady state.

Cardiac output determination during progressive exercise in cystic fibrosis.

Cardiac output (Q) determination using the equilibrium CO2-rebreathe indirect Fick technique (Equil) to estimate mixed venous PCO2 (Pv-CO2) has been validated during steady state (SS) exercise in subjects with lung disease. A modification of the exponential method using a low concentration of CO2 with an exponential rise in PEt-CO2 (Ex) during rebreathing to estimate Pv-CO2 has been validated during nonsteady state exercise. The purpose of the present study was to validate the Ex method in subjects with lung disease. Q was measured by Ex at every second work load during Prog. Q was measured after 5 min of SS exercise by both Ex and Equil. Arterial PCO2 was estimated from PEtCO2. There was no significant difference in the Q-VO2 relationship during Prog exercise between the combined control and mild (FEV1 > 70%) CF subjects or the moderate and severe CF subjects. Q can be determined in the nonsteady state using the exponential CO2-rebreathe indirect Fick technique in subjects with CF, allowing for noninvasive examination of cardiopulmonary interaction during exercise at a wide range of work loads.

The LDL receptor and LRP are receptors for beta VLDL on pigeon monocyte-derived macrophages.

Receptors for the lipoprotein, beta very low density lipoprotein (beta VLDL), have been identified through the binding of beta VLDL-gold conjugates on two ligand-induced regions of pigeon monocyte-derived macrophages. These regions were microvilli/retraction fibers and membrane ruffles. The present study investigated the location and identity of beta VLDL receptors using an antiserum directed against the epidermal growth factor (EGF) precursor region of the human low density lipoprotein (LDL) receptor. The anti-receptor serum recognized two membrane proteins from pigeon monocyte-derived macrophages, a 116 kDa (LDL receptor) protein and a 600 kDa (low density lipoprotein receptor-related protein; LRP) protein. Ligand blot analysis demonstrated that pigeon beta VLDL bound to both the LDL receptor and LRP. Immuno-gold electron microscopy using the anti-receptor serum resulted in immunoglobulin localization on the same two ligand-induced regions, microvilli/retraction fibers and membrane ruffles, to which the ligand had bound. Furthermore, simultaneous immunogold localization of the lipoprotein receptor antigens and beta VLDL-gold (ligand) binding substantiated co-localization of the receptor antigens and beta VLDL on the ligand-induced regions. Cross-competition studies with the anti-receptor serum and beta VLDL-gold conjugate documented that increasing concentration of the anti-receptor serum resulted in 70% inhibition of beta VLDL-gold conjugate binding. These data suggest that pigeon monocyte-derived macrophages utilize both the LDL receptor and LRP as receptors for pigeon beta VLDL.

High-intensity endurance training in 20- to 30- and 60- to 70-yr-old healthy men.

Factors contributing to maximal incremental and short-term exercise capacity were measured before and after 12 wk of high-intensity endurance training in 12 old (60-70 yr) and 10 young (20-30 yr) sedentary healthy males. Peak O2 uptake in incremental cycle ergometer exercise increased from 1.60 +/- 0.073 to 2.21 +/- 0.073 (SE) l/min (38% increase) in the old subjects and from 2.54 +/- 0.141 to 3.26 +/- 0.181 l/min (29%) in the young subjects. Peak cardiac output, estimated by extrapolation from a series of submaximal measurements by the CO2 rebreathing method, increased by 30% (from 12.7 to 16.5 l/min) in the old subjects, associated with a 6% increase (from 126 to 135 ml/l) in arteriovenous O2 difference; in the young subjects there were equal 14% increases in both variables (18.0 to 20.5 l/min and 140 to 159 ml/l, respectively). Submaximal mean arterial pressure and cardiac output were lower posttraining in the old subjects; total vascular conductance and cardiac stroke volume increased. Although peak power at the start of a short-term maximal isokinetic test did not change, total work accomplished in 30 s at a pedaling frequency of 110 revolutions/min increased in both groups, from 11.2 to 12.6 kJ and from 15.7 to 16.9 kJ in the old and young, respectively; fatigue during the 30-s test was less, and postexercise plasma lactate concentrations were lower. In older subjects, increases in aerobic power after high-intensity endurance training are at least as large as in younger subjects and are associated with increases in vascular conductance, maximal cardiac output, and stroke volume.

Calculation of whole blood CO2 content.

Currently used methods for calculating whole blood CO2 content from calculated plasma content, measured blood pH, hemoglobin concentration ([Hb]), and O2 saturation yield materially different results. In this study the constants of the fundamental equations relating blood CO2 content to plasma content have been reevaluated. An iterative computer technique was used to empirically derive appropriate constants from data obtained from nine healthy male subjects at rest and at several exercise work loads. A calculation was derived that fitted the data well [difference 0.02 +/- 1.19 ml/100 (SD) ml, r = 0.98] blood CCO2 = plasma CCO2 (Formula: see text) where plasma CCO2 = 2.226.s.plasma PCO2.(1 + 10pH-pK'), CCO2 is CO2 content, SO2 is O2 saturation, s is the plasma CO2 solubility coefficient, and pK' is the apparent pK [s and pK' are from the equations of Kelman (Respir. Physiol. 3: 111-115, 1967)].

Comparison of cardiac output during exercise by single-breath and CO2-rebreathing methods.

Cardiac output (Q) was estimated in supine rest and in upright cycling at several work rates up to 200 W in five male and one female subjects. At least four repetitions of both the CO2-rebreathing plateau method (Collier, J. Appl. Physiol. 9:25-29, 1956) and the Kim et al. (J. Appl. Physiol. 21: 1338-1344, 1966) single-breath method were performed at each work rate, in a steady state of O2 consumption and heart rate. At supine rest and low work rates, estimates of Q were similar by the two methods. However, at higher work rates, the single-breath method significantly (P less than 0.05) underestimated the value obtained by CO2 rebreathing. The reason for the difference in estimates of Q by the two methods was traced to the determination of arterial partial pressure of CO2 (PaCO2) and mixed venous partial pressure of CO2 (PvCO2). The estimate of PaCO2 from the single-breath method was approximately 88.5% of the estimate from end-tidal PCO2 used with the rebreathing method (P less than 0.001). The oxygenated PvCO2 calculated from the single-breath Q averaged approximately 92.5% of the PvCO2 from CO2 rebreathing (P less than 0.0001). The difference in estimates of Q was not eliminated by using a logarithmic form of the CO2 dissociation curve with the single-breath method.

Endogenous triacylglycerol utilization by rat skeletal muscle during tetanic stimulation.

An isolated perfused rat hindquarter preparation was used to examine the utilization of endogenous triacylglycerol (TG) during 20 min of electrical stimulation. The sciatic nerve was stimulated with maximal tetanic trains at 0.5 Hz. The isometric tension generated by the gastrocnemius-plantaris-soleus muscle group was recorded, and muscle samples were taken pre- and poststimulation. Twenty minutes of stimulation significantly reduced endogenous TG from 6.78 +/- 0.84 to 4.64 +/- 0.64 mumol X g dry wt-1 (32%) in the red gastrocnemius muscle and from 7.70 +/- 0.61 to 6.66 +/- 0.80 mumol X g dry wt-1 (13.5%) in the plantaris muscle. Although TG content decreased by 16% in the soleus (28.2 +/- 5.0 to 23.8 +/- 4.4 mumol X g-1), the change was not significant. Stimulation had no effect on white gastrocnemius TG concentration (6.84 +/- 1.22 to 6.25 +/- 1.41 mumol X g-1). Thus oxidation of TG occurred primarily in muscles with a large proportion of fast-twitch oxidative-glycolytic fibers. Calculations from measurements of muscle energy stores and fuel uptake indicated that up to 62% of the aerobic energy was provided by endogenous TG. Carbohydrate oxidation contributed up to 28% and the remaining 10% may be accounted for by the oxidation of exogenous free fatty acids originating in the perfusate or from hindquarter adipose tissue. The magnitude of the fall in TG concentration in a given muscle was inversely related to the fall in glycogen concentration.