Patent foramen ovale is not associated with hypoxemia in severe chronic obstructive pulmonary disease and does not impair exercise performance

RATIONALE

Patent foramen ovale (PFO) may be disadvantageous in chronic obstructive pulmonary disease (COPD). It is unknown whether right-to-left shunting through PFO increases during exercise impairing exercise performance.

OBJECTIVES

To determine whether (1) PFO prevalence is greater in hypoxemic versus less hypoxemic patients with COPD, (2) PFO is associated with clinically relevant impairment, and (3) right-to-left shunting increases during exercise and impairs exercise performance.

METHODS

Patients with COPD and age-matched control subjects underwent contrast transthoracic echocardiography and transcranial Doppler to identify PFO. Patients with COPD with no shunt and patients with large PFO underwent cardiopulmonary exercise tests with contrast transcranial Doppler, esophageal, and gastric balloon catheters.

MEASUREMENTS AND MAIN RESULTS

PFO prevalence was similar in 50 patients with COPD and 50 healthy control subjects (46% vs. 30%; P = 0.15). Large shunts were more common in patients with COPD (26% vs. 6%; P = 0.01). In an expanded COPD cohort, PFO prevalence was similar in 31 hypoxemic (Pao2 ≤ 7.3 kPa) and 63 less hypoxemic (Pao2 > 8.0 kPa) patients with COPD (39% vs. 52%; P = 0.27). Patients with intrapulmonary shunting had lower Pao2 than both patients with PFO and those with no right-to-left shunt (7.7 vs. 8.6 vs. 9.3 kPa, respectively; P = 0.002). Shunting significantly increased during exercise in patients with COPD with PFO. Endurance time at 60% Vo2max was 574 (178) seconds for patients with PFO and 534 (279) seconds for those without (P = ns).

CONCLUSIONS

Hypoxemic patients with COPD do not have a higher prevalence of PFO. Patients with COPD with PFO do not perform less well either on a 6-minute walk or submaximal exercise testing despite increased right-to-left shunting during exercise.

Randomized trial of 'intelligent' autotitrating ventilation versus standard pressure support non-invasive ventilation: impact on adherence and physiological outcomes

BACKGROUND AND OBJECTIVE

Effective non-invasive ventilation (NIV) therapy is dependent on optimal ventilator settings to maximize clinical benefit and patient tolerance. Intelligent volume-assured pressure support (iVAPS) is a hybrid mode of servoventilation, providing constant automatic adjustment of pressure support (PS) to achieve a target ventilation determined by the patient's requirements. In a randomized crossover trial, we tested the hypothesis that iVAPS, with automated selection of ventilator settings, was non-inferior to standard PS ventilation, with settings determined by an experienced health-care professional, for controlling nocturnal hypoventilation in patients naive to NIV.

METHODS

Eighteen patients referred to a ventilator clinic with chronic obstructive or restrictive lung disease and newly diagnosed nocturnal hypoventilation (10 male, median (interquartile range): age 54(41-61) years, mean daytime PaO2 9.25(8.59-10.31) kPa, -PaCO2 6.38(5.93-6.65) kPa were randomized to iVAPS and standard PS. Polysomnography with transcutaneous CO2 monitoring was performed at baseline and 1 month after each treatment period. Nightly hours of therapy were recorded by the ventilator.

RESULTS

iVAPS delivered a lower median PS compared with standard PS (8.3(5.6-10.4) vs 10.0(9.0-11.4) cmH2 O; P = 0.001) for the same ventilatory outcome (mean overnight: SpO2 96(95-98) vs 96(93-97)%; P = 0.13 and PtcCO2 6.5(5.8-6.8) vs 6.2(5.8-6.9); P = 0.54). There was no difference in outcome between ventilator modes for spirometry, respiratory muscle strength, sleep quality, arousals or O2 desaturation index. Adherence was greater with iVAPS (5:40(4:42-6:49) vs 4:20(2:27-6:17) hh:mm/night; P = 0.004).

CONCLUSIONS

iVAPS servoventilation with automation of ventilation settings is as effective as PS ventilation initiated by a skilled health-care professional in controlling nocturnal hypoventilation and produced better overnight adherence in patients naive to NIV.

Lung function indices for predicting mortality in COPD

Chronic obstructive pulmonary disease (COPD) is characterised by high morbidity and mortality. It remains unknown which aspect of lung function carries the most prognostic information and if simple spirometry is sufficient.

Survival was assessed in COPD outpatients whose data had been added prospectively to a clinical audit database from the point of first full lung function testing including spirometry, lung volumes, gas transfer and arterial blood gases. Variables univariately associated with survival were entered into a multivariate Cox proportional hazard model.

604 patients were included (mean±sd age 61.9±9.7 years; forced expiratory volume in 1 s 37±18.1% predicted; 62.9% males); 229 (37.9%) died during a median follow-up of 83 months. Median survival was 91.9 (95% CI 80.8–103) months with survival rates at 3 and 5 years 0.83 and 0.66, respectively. Carbon monoxide transfer factor % pred quartiles (best quartile (>51%): HR 0.33, 95% CI 0.172–0.639; and second quartile (51–37.3%): HR 0.52, 95% CI 0.322–0.825; versus lowest quartile (<27.9%)), age (HR 1.04, 95% CI 1.02–1.06) and arterial oxygen partial pressure (HR 0.85, 95% CI 0.77–0.94) were the only parameters independently associated with mortality.

Measurement of gas transfer provides additional prognostic information compared to spirometry in patients under hospital follow-up and could be considered routinely.

Transfer factor not GOLD stage is the most powerful predictor of survival in patients with COPDhttp://ow.ly/mGmjG

Breathlessness and skeletal muscle weakness in patients undergoing lung health screening in primary care

Earlier diagnosis of COPD is a major public health challenge as symptoms may be attributed to the normal consequences of aging. The optimum strategy for identifying patients with COPD remains to be determined. People aged 35 and over (n = 1896) on a GP practice register were randomised to either invitation or an opportunistic lung health check which included spirometry, quadriceps strength and MRC dyspnoea score. Then, 101 participants subsequently completed the General Practice Physical Activity Questionnaire. A total of 335 attended over a 15-week period; 156 were in the invitation group and 179 from the opportunist group. In 25 persons, spirometry was unsatisfactory or contraindicated. Spirometry was normal in 204(65.8%) and restrictive in 36(11.6%). 70(22.6%) had airflow obstruction, corresponding to Global Initiative for Chronic Lung Disease (GOLD) stages I-IV in 18(5.8%), 35(11.3%), 14(4.5%) and 3(1.0%), respectively. The opportunist group were significantly more likely to have airflow obstruction 30.1% vs 14.3% (p = 0.001). Breathlessness was reported commonly (40.5%) and quadriceps strength correlated significantly with MRC dyspnoea score independent of age, sex, pack-years smoked, fat-free mass and FEV(1) percent predicted. This relationship was also present in the subgroup of healthy participants (n = 143). 51.5% of participants screened were classified as "inactive" and this group were weaker and more breathless than those who were more active. Airflow obstruction was more common in those screened opportunistically. Breathlessness and inactivity are common in patients taking part in spirometry screening. Breathlessness is significantly associated with leg strength independent of spirometry and should be amenable to interventions to increase physical activity.

Singing classes for chronic obstructive pulmonary disease: a randomized controlled trial

BACKGROUND

There is some evidence that singing lessons may be of benefit to patients with chronic obstructive pulmonary disease (COPD). It is not clear how much of this benefit is specific to singing and how much relates to the classes being a group activity that addresses social isolation.

METHODS

Patients were randomised to either singing classes or a film club for eight weeks. Response was assessed quantitatively through health status questionnaires, measures of breathing control, exercise capacity and physical activity and qualitatively, through structured interviews with a clinical psychologist.

RESULTS

The singing group (n=13 mean(SD) FEV1 44.4(14.4)% predicted) and film group (n=11 FEV1 63.5(25.5)%predicted) did not differ significantly at baseline. There was a significant difference between the response of the physical component score of the SF-36, favouring the singing group +12.9(19.0) vs -0.25(11.9) (p=0.02), but no difference in response of the mental component score of the SF-36, breathing control measures, exercise capacity or daily physical activity. In the qualitative element, positive effects on physical well-being were reported in the singing group but not the film group.

CONCLUSION

Singing classes have an impact on health status distinct from that achieved simply by taking part in a group activity.

TRIALS REGISTRATION

Registration Current Controlled Trials - ISRCTN17544114.

Respiratory muscle fatigue following exercise in patients with interstitial lung disease

BACKGROUND

It is not known whether respiratory muscle fatigue occurs as a consequence of exercise in patients with interstitial lung disease (ILD) and, if so, to what extent it is related to changes in dynamic lung volumes.

OBJECTIVES

To assess the development of respiratory muscle fatigue in patients with ILD and relate it to the respiratory pattern during exercise.

METHODS

Sixteen ILD patients (11 women) performed incremental, symptom-limited cycle ergometry with inspiratory capacity manoeuvres used to measure changes in end-expiratory lung volume (EELV). Twitch transdia-phragmatic pressure (TwPdi) and twitch gastric pressure (TwT10Pga), in response to magnetic stimulation, were used to assess the development of fatigue.

RESULTS

TwPdi did not differ significantly before and after exercise (21.8 ± 8 vs. 20.2 ± 8 cm H2O; p = 0.10), while TwT10Pga fell from 28.6 ± 18 to 25.2 ± 14 cm H2O (p = 0.02). EELV fell from 2.18 ± 0.65 to 1.91 ± 0.59 liters following exercise (p = 0.04). The fall in TwT10Pga correlated with peak oxygen uptake at peak of exercise (r = -0.52, p = 0.041), increase in heart rate (r = 0.53, p = 0.032) and with the decrease of EELV during exercise (r = 0.57, p = 0.021). Abdominal muscle fatiguers (n = 9, 56%), defined as having a ≥10% fall in TwT10Pga, had a fall in EELV of 22 ± 22% compared to 0.7 ± 8% in non-fatiguers (p = 0.016).

CONCLUSION

Abdominal muscle fatigue develops during exercise in some ILD patients in association with increased expiratory muscle activity manifested by reduced EELV.

Health status assessment in routine clinical practice: the chronic obstructive pulmonary disease assessment test score in outpatients

BACKGROUND

The chronic obstructive pulmonary disease (COPD) assessment test (CAT) is a simple, self-completion questionnaire developed to measure health status in patients with COPD, which is potentially suitable for routine clinical use.

OBJECTIVES

The purpose of this study was to establish the determinants of the CAT score in routine clinical practice.

METHODS

Patients attending the clinic completed the CAT score before being seen. Clinical data, including, where available, plethysmographic lung volumes, transfer factor and arterial blood gas analysis, were recorded on a pro forma in the clinic.

RESULTS

In 224 patients (36% female), mean forced expiratory volume in 1 s (FEV₁) was 40.1% (17.9) of predicted (%pred); CAT score was associated with exacerbation frequency [0-1/year 20.1 (7.6); 2-4/year 23.5 (7.8); >4/year 28.5 (7.3), p < 0.0001; 41/40/19% in each category] and with Medical Research Council (MRC) dyspnoea score (r² = 0.26, p < 0.0001) rising approximately 4 points with each grade. FEV(1) %pred had only a weak influence. Using stepwise regression, CAT score = 2.48 + 4.12 [MRC (1-5) dyspnoea score] + 0.08 (FEV(1) %pred) + 1.06 (exacerbation rate/year)] (r² = 0.36, p < 0.0001). The CAT score was higher in patients (n = 54) with daily sputum production [25.9 (7.5) vs. 22.2 (8.2); p = 0.004]. Detailed lung function (plethysmography and gas transfer) was available in 151 patients but had little influence on the CAT score.

CONCLUSION

The CAT score is associated with clinically important variables in patients with COPD and enables health status measurement to be performed in routine clinical practice.

Effect of acute exacerbations on skeletal muscle strength and physical activity in cystic fibrosis

BACKGROUND

Skeletal muscle weakness is an important complication of chronic respiratory disease. The effect of acute exacerbations on strength in patients with cystic fibrosis is not known.

METHODS

Quadriceps (QMVC) and respiratory muscle strength were measured in patients at the time of acute admission, at discharge and one month later. Patients wore an activity monitor during admission and at one month. Convalescent values were compared to the stable clinic population.

RESULTS

Data were available for 13 acute admissions and 25 stable CF outpatients. Strength and other parameters including daily step count did not differ significantly between the stable and one month post-admission groups. At admission, QMVC was 16.7 (8.3)% lower than at convalescence, whereas inspiratory muscle strength did not change significantly. Reduction in QMVC did not correlate with activity levels or with markers of systemic inflammation.

CONCLUSION

Further research is needed to identify the mechanisms responsible for the reduction in QMVC.

ACUTE CALCIFIC TENDINITIS OF THE FINGER — A CASE REPORT

Acute calcific tendinitis of the hand is rare and often misdiagnosed as infection, fracture or periarthritis. It frequently occurs in peri-menopausal women and is caused by deposits of hydroxyapatite crystals. We describe acute calcific tendinitis of the flexor digitorum superficialis insertion in an elderly man taking oral anticoagulants. The differential diagnoses and recommended treatment are discussed.

An inverting circumferential suture for flexor tenorraphy

Zone two flexor tendon repair remains challenging with significant outcome variation using recognised techniques. Tendon adhesion formation results in poor outcomes and rehabilitation regimes aim to limit this. Some repairs augment strength, but increasing bulk mitigates against movement. This novel epitendinous technique causes tendon inversion with potential gliding benefits and improved outcomes. 60 porcine tendons were randomised to a 2-stranded modified Kessler or a 4-stranded Adelaide repair, then sudivided into three different circumferential technique groups: locked running, Silfverskiold, or a new inverting repair. Tendon load to failure (LTF), 2 mm gap formation, bulking effect and method of failure were analysed during digital tensiometry. Four-stranded repairs demonstrated better LTF than 2-stranded techniques. The inverting epitendinous and Silfverskiold repairs showed higher LTF characteristics than the locked running suture, and better tissue holding capacity. The inverting repair has similar properties to commonly used suturing methods and the conformation creates a smooth inverted repair.

Singing teaching as a therapy for chronic respiratory disease--a randomised controlled trial and qualitative evaluation

Background

Despite optimal pharmacological therapy and pulmonary rehabilitation, patients with COPD continue to be breathless. There is a need to develop additional strategies to alleviate symptoms. Learning to sing requires control of breathing and posture and might have benefits that translate into daily life.

Methods

To test this hypothesis we performed a randomised controlled trial, comparing a six week course of twice weekly singing classes to usual care, in 28 COPD patients. The experience of singing was assessed in a qualitative fashion, through interviews with a psychologist. In addition, we surveyed patients with chronic respiratory conditions who participated in a series of open singing workshops.

Results

In the RCT, the physical component score of the SF36 improved in the singers (n = 15) compared to the controls (n = 13); +7.5(14.6) vs. -3.8(8.4) p = 0.02. Singers also had a significant fall in HAD anxiety score; -1.1(2.7) vs. +0.8(1.7) p = 0.03. Singing did not improve single breath counting, breath hold time or shuttle walk distance. In the qualitative element, 8 patients from the singing group were interviewed. Positive effects on physical sensation, general well-being, community/social support and achievement/efficacy emerged as common themes. 150 participants in open workshops completed a questionnaire. 96% rated the workshops as "very enjoyable" and 98% thought the workshop had taught them something about breathing in a different way. 81% of attendees felt a "marked physical difference" after the workshop.

Conclusion

Singing classes can improve quality of life measures and anxiety and are viewed as a very positive experience by patients with respiratory disease; no adverse consequences of participation were observed.

Trial Registration

Current Controlled Trials - ISRCTN17544114.

An assessment of skin preparation in upper limb surgery

Postoperative wound infections remain a major source of upper limb morbidity. The effectiveness of peri-operative human upper limb preparation was determined using a clear fluid antiseptic and an iodine-based solution over 60 and 90 seconds. Less area was missed using iodine over both times and increasing clear solution preparation time from 60 to 90 seconds improved coverage. Surgical experience had little outcome relevance and a 90-second preparation time with either solution was insufficient, with fingers being the sites most commonly missed.

Topographic organization of projections from the amygdala to the visual cortex in the macaque monkey

The topography of amygdaloid projections to the visual cortices in the macaque monkey was examined by injecting the fluorescent tracers Fast Blue and Diamidino Yellow at different locations in the occipital and temporal lobes and mapping the distribution of retrogradely labeled cells in the amygdala. Injections involving regions from rostral area TE to caudal area V1 all resulted in labeled cells within the basal nucleus of the amygdala. Relatively few double-labeled cells were observed even when the two injections were separated by less than 3 mm. The projections were rostrocaudally organized such that projections to caudal visual areas originated from dorsal and caudal portions of the magnocellular division of the basal nucleus while projections to more rostrally situated visual areas originated in more rostral and ventral portions of the basal nucleus. When injections involved rostral and medial portions of area TE, retrogradely labeled cells were observed in the accessory basal and lateral nuclei in addition to the basal nucleus. These data confirm that the amygdala gives rise to feedback projections to all levels of the "ventral stream" visual pathway. The projections do not appear to be diffusely distributed since few double-labeled cells were observed. The largest cells of the basal nucleus, those located in the magnocellular division, project the farthest in the visual system and innervate all occipital and temporal levels. The smaller cells, in the intermediate and parvicellular regions, project to more rostral and medial portions of the visual cortex. These results suggest that the amygdala may have substantial modulatory control over sensory processing at all stages of the ventral-stream visual cortical hierarchy.

Severe injury triggers antigen-specific T-helper cell dysfunction

Although it is established that post-injury immune dysfunction involves alterations in T-cell function, the effects of injury on T-cell function in vivo are poorly understood. This study uses a mouse injury model and an antigen immunization approach to investigate the influence of injury on antigen-specific T-helper cell function. We report here that injury triggered a significant reduction in antigen-specific T-helper-1 (Th1)-dependent IgG2a antibody formation, while IgM, IgG1, and IgE production was unchanged. In addition, injury caused a reduction in cytokine production (IL-2, IFNgamma and IL-10) by antigen-stimulated T-cells. We also demonstrate that interleukin 12 (IL-12), a cytokine that promotes Th1 cell differentiation, restored IgG2a antibody formation and corrected the injury-induced reduction in antigen-stimulated cytokine production. Taken together, these findings indicate that severe injury induces a dramatic reduction in Th1 cell function in vivo and suggest that therapies designed to restore Th1 cell function may be beneficial to the injured host.

Enhancing diagnostic ultrasound programs utilizing wide-area image management technology

Diagnostic ultrasound in remote sites is limited by attendant delay in interpretation and reporting. Technology advances were incorporated in an ultrasound program based in Churchill, Manitoba, and designed to meet the needs of the Central Canadian Arctic. Still-frame ultrasound images are digitized via a sonographer's picture archiving and communications system (PACS) workstation, and as they are collected they are transmitted over a dial-up Internet protocol network in Dicom 3.0 format to a tertiary care center. Received images are routed to a physician's PACS workstation, where they can be reviewed prior to the patient leaving the remote clinic. The impact of existing technology on a northern ultrasound program is discussed. The implications of technology enhancement are reviewed, with specific reference to remote low bandwidth sites.

The effect of hysterectomy on ano-rectal physiology

Hysterectomy is associated with severe constipation in a subgroup of patients, and an adverse effect on colonic motility has been described in the literature. The onset of irritable bowel syndrome and urinary bladder dysfunction has also been reported after hysterectomy. In this prospective study, we investigated the effect of simple hysterectomy on ano-rectal physiology and bowel function. Thirty consecutive patients were assessed before and 16 weeks after operation. An abdominal hysterectomy was performed in 16 patients, and a vaginal procedure was performed in 14. The parameters measured included the mean resting, and maximal forced voluntary contraction anal pressures, the recto-anal inhibitory reflex, and rectal sensation to distension. In 8 patients, the terminal motor latency of the pudendal nerve was assessed bilaterally. Pre-operatively, 8 patients were constipated. This improved following hysterectomy in 4, worsened in 2, and was unchanged in 2. Symptomatology did not correlate with changes in manometry. Although, the mean resting pressure was reduced after hysterectomy (57 mmHg-53 mmHg, P = 0.0541), the maximal forced voluntary contraction pressure was significantly decreased (115 mmHg-105 mmHg, P = 0.029). This effect was more pronounced in those with five or more previous vaginal deliveries (P = 0.0244, n = 9). There was no significant change in the number of patients with an intact ano-rectal inhibitory reflex after hysterectomy. There was no change in rectal sensation to distension, and the right and left pudendal nerve terminal motor latencies were unaltered at follow-up. Our results demonstrate that hysterectomy causes a decrease in the maximal forced voluntary contraction and pressure, and this appears to be due to a large decrease in a small group of patients with previous multiple vaginal deliveries.

Burn injury primes naive CD4+ T cells for an augmented T-helper 1 response

BACKGROUND

The mechanisms responsible for altered T-cell responses and cytokine production after injury are not well understood. We used T-cell receptor (TCR) transgenic mice to study burn injury effects on naive versus antigen-activated CD4+ T cells in vivo.

METHODS

One week after sham or burn injury, lymph node cells were prepared from TCR transgenic mice and stimulated with TCR transgene-specific antigens. T-cell proliferation was measured and culture supernatants were tested for interleukin-2 (IL-2), interferon-gamma (IFN-gamma), IL-4, and IL-10 by enzyme-linked immunosorbent assay (ELISA). Burn injury effects on antigen-activated T cells were studied by immunizing TCR transgenic or wild-type mice at the time of injury.

RESULTS

The antigen-stimulated proliferation of native CD4+ T cells was unaffected by burn injury and no increase in T-helper 2 (Th2)-type cytokine production was observed. Instead, burn injury augmented INF-gamma production by naive CD4+ transgenic T cells, and IL-2 production was marginally reduced. Thus, burn injury primed native T cells for an enhanced Th1-type response. In contrast, antigen-specific proliferation, IL-2, and IFN-gamma production by T cells harvested from immunized wild-type mice were suppressed. Unexpectedly, high mortality was observed when burn-injured TCR transgenic mice were immunized.

CONCLUSION

Our results show that burn injury has differential effects on naive and antigen-activated CD4+ T cells and can prime naive CD4+ T cells.

Coexistent Hirschsprung's disease and esophageal achalasia in male siblings

Achalasia of the esophagus developed in two male siblings soon after birth, and they were successfully treated by surgery. Persistent signs resulted in the later diagnosis of Hirschsprung's disease. One required subtotal colectomy and ileoanal anastomosis, and the other is managing well on conservative treatment. Genetic analysis of the genes encoding the RET protooncogene, endothelin-3, and the endothelin-3 receptor did not show any defect. Familial achalasia of the esophagus in combination with Hirschsprung's disease has never been reported.

Major injury induces increased production of interleukin-10 by cells of the immune system with a negative impact on resistance to infection

OBJECTIVE

The purpose of this study was to compare the production of interleukin-10 (IL-10) by peripheral blood mononuclear cells (PBMC) from injured patients and control subjects to determine the responsible cell types and to relate IL-10 production to the occurrence of sepsis. A mouse model of burn injury was used to confirm the human findings and to assess the importance of IL-10 in the lowered resistance to infection after injury.

SUMMARY BACKGROUND DATA

Severe injury is associated with depressed immune responses. Although IL-10 is known to inhibit several aspects of immune reactivity, the role of IL-10 in postinjury immune suppression remains controversial.

METHODS

Peripheral blood mononuclear cells from 14 burn and 12 trauma patients and 16 healthy individuals were studied at serial intervals for IL-10 production stimulated by a T-cell mitogen, phytohemagglutinin, and by bacterial lipopolysaccharide. To determine the source of IL-10, CD4+ and CD8+ lymphocyte subsets were obtained by selective depletion of PBMC with antibody-coated magnetic beads and were stimulated by anti-CD3 antibody to induce IL-10 secretion. In addition, IL-10 production by patients' PBMC in the first 10 days after injury was assessed for correlation with subsequent septic events. Anti-CD3-stimulated IL-10 production also was determined for CD4- and CD8-enriched lymphocyte subsets obtained by antibody and complement depletion of splenocytes harvested from groups of burn and sham burn mice at day 10 after injury, the time of maximal susceptibility to a septic challenge, cecal ligation and puncture (CLP). Finally, to test the importance of IL-10 in immune suppression in vivo, groups of burn and sham burn mice were treated with anti-IL-10 monoclonal antibody or control immunoglobulin G (IgG) on days 1 and 3 postinjury and were observed for survival after CLP on day 10.

RESULTS

Patients' PBMC produced significantly more IL-10 than did controls' PBMC 7 to 14 days after injury. Patients' CD4+ (T-helper) but not CD8+ (T-cytotoxic) lymphocytes also showed increased IL-10 production versus those of control subjects early after injury. Increased PBMC IL-10 production in the first 10 days postinjury correlated significantly (p < 0.05) with subsequent septic events. Burn mouse CD4-enriched but not CD8-enriched splenocytes produced more IL-10 than did sham burn splenocyte subsets on day 10 after injury. Burn mice treated with anti-IL-10 antibody but not with control IgG had significantly increased survival after CLP.

CONCLUSION

Serious injury in humans and in a mouse burn model is followed by increased stimulated production of IL-10 by cells of the immune system. The CD4+ T-helper cells appear to be a major source of IL-10 after injury. In injured patients, increased IL-10 production is correlated with subsequent septic events, and in the burn mouse, IL-10 appears to induce decreased resistance to infection.

Anti-interleukin-10 antibody restores burn-induced defects in T-cell function

BACKGROUND

Studies have shown that susceptibility to sepsis after severe injury correlated with reduced production of T-helper 1 (Th1) cytokines (interleukin-2 [IL-2] and interferon-gamma [IFN-gamma]) and a persistence of T-helper 2 (Th2) cytokines (IL-4 and IL-10). The mechanisms responsible for this effect are not clear. We used a T-dependent antigen to study both the effect of burn injury on antigen-specific Th functions in vivo and the effect of anti-IL-10 antibody on these functions.

METHODS

Male A/J mice were anesthetized and given a 25% scald burn or a sham burn. On day 0 all mice were immunized with 100 micrograms trinitrobenzene sulfonic acid (TNP) haptenated ovalbumin (TNP-OVA) in complete Freund's adjuvant. Mice (10 per group) were given 250 micrograms monoclonal rat antimurine IL-10 antibody (anti-IL-10 MAB) or control rat immunoglobin G (IgG) on day 0 and 100 micrograms anti-IL-10 MAB or IgG on day 2. On day 10 the mice were killed to obtain serum and spleen cells. TNP-specific serum antibody isotype titers were determined by enzyme-linked immunosorbent assay (ELISA). Splenocyte proliferation and cytokine-production in response to TNP-OVA or to anti-CD3 MAB were determined by tritiated thymidine incorporation and by ELISA, respectively.

RESULTS

Burn injury resulted in depressed levels of the TNP-specific IgG2a antibody isotype (Th1 dependent), whereas TNP-specific IgG1 and IgE (Th2 dependent) levels were not decreased in burn versus sham burn mice. Anti-IL-10 MAB but not IgG restored the IgG2a response. Burn injury also resulted in reduced TNP-OVA-specific proliferation of splenocytes, whereas anti-CD3 proliferation was equivalent in burn and sham mice. TNP-OVA-specific IL-2 and IFN-gamma production were significantly reduced by burn injury. Anti-IL-10 MAB restored TNP-OVA-specific proliferation and antigen-specific IL-2 and interferon-gamma production by splenocytes from burn mice.

CONCLUSIONS

Burn injury induces the loss of antigen-specific Th1 cell function, and IL-10 acts as a trigger to down-regulate Th1 activity after injury.

Is circulating endotoxin the trigger for the systemic inflammatory response syndrome seen after injury?

OBJECTIVE

Patients with severe traumatic or burn injury and a mouse model of burn injury were studied early after injury to determine the relation of plasma endotoxin (lipopolysaccharide [LPS]) to the production of proinflammatory cytokines and subsequent resistance to infection.

SUMMARY BACKGROUND DATA

Elevated levels of plasma LPS have been reported in patients after serious injury. It has been suggested that circulating LPS may be a trigger for increased proinflammatory cytokine production and may play a role in the septic syndromes seen in a substantial portion of such patients. Yet, despite multiple reports of leakage of LPS from the gut and bacterial translocation after injury in animal models, there is little direct evidence linking circulating LPS with production of inflammatory mediators.

METHODS

The authors studied serial samples of peripheral blood from 10 patients with 25% to 50% surface area burns and 8 trauma patients (injury Severity Score, 25-57). Patients were compared with 18 healthy volunteers. The study was focused on the first 10 days after injury before the onset of sepsis or the systemic inflammatory response syndrome. Plasma samples were assayed for LPS, and adherent cells from the blood were studied for basal and LPS-stimulated production of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and interleukin-6 (IL-6). The correlation of increased plasma LPS with TNF-alpha production was studied as was the association of increased plasma LPS and increased TNF-alpha production with subsequent septic complications. We also studied a mouse model of 25% burn injury. Burn mice were compared with sham burn control subjects. Plasma samples were assayed at serial intervals for LPS, and adherent cells from the spleens were studied for basal- and LPS-stimulated production of TNF-alpha, IL-1 beta, and IL-6. Expression of the messenger RNAs for IL-1 beta and TNF-alpha also was measured. The relation of increased TNF-alpha production with mortality from a septic challenge, cecal ligation and puncture (CLP), was determined. Finally, the effect of administration of LPS to normal mice on subsequent mortality after CLP and on TNF-alpha production was studied.

RESULTS

Elevated plasma LPS (> 1 pg/mL) was seen in 11 of the 18 patients within 10 days of injury and in no normal control subjects. In this period, patients as compared with control subjects showed increased stimulated production of TNF-alpha, IL-1 beta, and IL-6. Increased TNF-alpha production was not correlated with elevated plasma LPS in the same patients. Neither increased plasma LPS nor increased TNF-alpha production early after injury was correlated with subsequent development of systemic inflammatory response syndrome or sepsis in the patients. Burn mice, as compared with sham burn control subjects, showed elevated plasma LPS levels chiefly in the first 3 days after injury. Increased stimulated production of proinflammatory cytokines by adherent splenocytes from the burn mice also was seen at multiple intervals after injury and did not correlate with mortality from CLP. Increased production of TNF-alpha and IL-1 beta was associated with increased expression of messenger RNAs for these cytokines. Finally, two doses of 1 ng LPS administered 24 hours apart to normal mice had no effect on mortality from CLP performed 7 days later nor on the production of TNF-alpha at the time of CLP.

CONCLUSIONS

These findings call into question the idea that circulating LPS is the trigger for increased proinflammatory cytokine production, systemic inflammatory response syndrome, and septic complications in injured patients.