Concurrent beneficial (vitamin D production) and hazardous (cutaneous DNA damage) impact of repeated low-level summer sunlight exposures

Background

The concurrent impact of repeated low‐level summer sunlight exposures on vitamin D production and cutaneous DNA damage, potentially leading to mutagenesis and skin cancer, is unknown.

Objectives

This is an experimental study (i) to determine the dual impact of repeated low‐level sunlight exposures on vitamin D status and DNA damage/repair (via both skin and urinary biomarkers) in light‐skinned adults; and (ii) to compare outcomes following the same exposures in brown‐skinned adults.

Methods

Ten white (phototype II) and six South Asian volunteers (phototype V), aged 23–59 years, received 6 weeks’ simulated summer sunlight exposures (95% ultraviolet A/5% ultraviolet B, 1·3 standard erythemal doses three times weekly) wearing summer clothing exposing ~35% body surface area. Assessments made were circulating 25‐hydroxyvitamin D [25(OH)D], immunohistochemistry for cyclobutane pyrimidine dimer (CPD)‐positive nuclei and urinary biomarkers of direct and oxidative (8‐oxo‐deoxyguanosine) DNA damage.

Results

Serum 25(OH)D rose from mean 36·5 ± 13·0 to 54·3 ± 10·5 nmol L⁻¹ (14·6 ± 5·2 to 21·7 ± 4·2 ng mL⁻¹) in phototype II vs. 17·2 ± 6·3 to 25·5 ± 9·5 nmol L⁻¹ (6·9 ± 2·5 to 10·2 ± 3·8 ng mL⁻¹) in phototype V (P < 0·05). Phototype II skin showed CPD‐positive nuclei immediately postcourse, mean 44% (range 27–84) cleared after 24 h, contrasting with minimal DNA damage and full clearance in phototype V (P < 0·001). The findings did not differ from those following single ultraviolet radiation (UVR) exposure. Urinary CPDs remained below the detection threshold in both groups; 8‐oxo‐deoxyguanosine was higher in phototype II than V (P = 0·002), but was unaffected by UVR.

Conclusions

Low‐dose summer sunlight exposures confer vitamin D sufficiency in light‐skinned people concurrently with low‐level, nonaccumulating DNA damage. The same exposures produce minimal DNA damage but less vitamin D in brown‐skinned people. This informs tailoring of sun‐exposure policies.

What's already known about this topic?

Repeated low‐level exposures to simulated U.K. sunlight can produce vitamin D sufficiency in light‐skinned people, but the concurrent impact on cutaneous DNA damage is unknown.

What does this study add?

Low‐level simulated sunlight exposures in people of skin phototype II conferred vitamin D sufficiency concurrently with DNA damage, which showed partial clearance at 24 h and no evidence of accumulated damage after 6 weeks of exposures.

The same exposures produced minimal DNA damage but less vitamin D in brown‐skinned people (phototype V).

The findings are informative for sun‐exposure guidance.

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Early skin and challenge testing after rocuronium anaphylaxis

We present a case of early skin and challenge testing in a patient following severe anaphylaxis to rocuronium. The patient presented for semi-elective laparoscopic cholecystectomy and developed anaphylaxis with severe cardiovascular collapse after induction of anaesthesia. Surgery was cancelled but was considered necessary before the recommended four to six weeks for formal allergy testing. Limited skin and challenge testing was performed to rocuronium and cisatracurium while the patient was in the intensive care unit to identify a safe neuromuscular blocking drug for subsequent early surgery. The subsequent surgery, 48 hours after the initial reaction, was uneventful. The case highlights the difficulties when anaesthetising patients with recent anaphylaxis who have not yet had formal allergy testing and presents a potential management strategy involving early skin testing.

Sunlight exposure behaviour and vitamin D status in photosensitive patients: longitudinal comparative study with healthy individuals at U.K. latitude

BACKGROUND

Low vitamin D status is prevalent in wintertime in populations at northerly latitudes. Photosensitive patients are advised to practise sun avoidance, but their sunlight exposure levels, photoprotective measures and resulting vitamin D status are unknown.

OBJECTIVES

To examine seasonal vitamin D status in photosensitive patients relative to healthy individuals and to assess quantitatively behavioural and demographic contributors.

METHODS

This was a longitudinal prospective cohort study (53·5°N) examining year-round 25-hydroxyvitamin D [25(OH)D] levels, sun-exposure behaviour and oral vitamin D intake in photosensitive patients diagnosed at a photoinvestigation unit (n = 53), compared with concurrently assessed healthy adults (n = 109).

RESULTS

Photosensitive patients achieved seasonal 25(OH)D variation, but insufficient (< 20 ng mL(-1); 50 nmol L(-1)) and even deficient (< 10 ng mL(-1); 25 nmol L(-1)) levels occurred at the summer peak in 47% and 9% of patients, respectively, rising to 73% and 32% at the winter trough. Adjusting for demographic factors, the mean values were lower than for healthy volunteers by 18% [95% confidence interval (CI) 4-29] in summer (P = 0·02) and 25% (95% CI 7-39) in winter (P = 0·01). Behavioural factors explained 25(OH)D differences between cohorts. Patients demonstrated lower weekend ultraviolet B doses (P < 0·001), smaller skin surface area exposure (P = 0·004) and greater sunscreen use (P < 0·001), while average oral vitamin D intake was low in both groups (photosensitive: 2·94 μg per day). Supplementation and summer surface area exposure predicted summer peak and winter trough 25(OH)D levels. A 1 μg per day increment in supplementary vitamin D raised summer and winter 25(OH)D by 5% (95% CI 3-7) and 9% (95% CI 5-12), respectively (both P < 0·001).

CONCLUSIONS

Photosensitive patients are, through their photoprotective measures, at high risk of year-round low vitamin D status. Guidance on oral measures should target this patient group and their physicians.

Sunlight exposure and photoprotection behaviour of white Caucasian adolescents in the UK

BACKGROUND

Sun exposure has positive and negative effects on health, yet little is known about the sun exposure behaviour of UK adolescents, including those more prone or less prone to sunburn.

OBJECTIVE

To examine sun exposure behaviour of UK white Caucasian adolescents including time spent outdoors, holiday behaviour, use of sunscreen and clothing, with assessment for differences between sun-reactive skin type groups.

METHODS

White Caucasian adolescents (12-15 years) attending schools in Greater Manchester completed a two-page questionnaire to assess sun exposure and photoprotective behaviour.

RESULTS

A total of 133 adolescents (median age 13.4 years; 39% skin type I/II, 61% skin type III/IV) completed the questionnaire. In summer, adolescents spent significantly longer outdoors at weekends (median 4 h/day, range 0.25-10) than on weekdays (2, 0.25-6; P < 0.0001). When at home in the UK during summer, 44% reported never wearing sunscreen compared to just 1% when on a sunny holiday. Sunscreen use was also greater (frequency/coverage) when on a sunny holiday than at home in the UK summer (P < 0.0001). Adolescents of skin types I/II (easy burning) spent significantly less time outdoors than skin types III/IV (easy tanning) on summer weekends (P < 0.001), summer weekdays (P < 0.05) and on a sunny holiday (P = 0.001). Furthermore, skin types I/II reported greater sunscreen use during summer in the UK and on sunny holiday (both P < 0.01), and wore clothing covering a greater skin area on a sunny holiday (P < 0.01) than skin types III/IV. There was no difference in sun exposure behaviour/protection between males and females.

CONCLUSION

The greater sun-protective measures reported by adolescents of sun-reactive skin type group I/II than III/IV suggest those who burn more easily are aware of the greater need to protect their skin. However, use of sunscreen during the UK summer is low and may need more effective promotion in adolescents.

Lifestyle factors including less cutaneous sun exposure contribute to starkly lower vitamin D levels in U.K. South Asians compared with the white population

BACKGROUND

Long-standing concerns over the vitamin D status of South Asian adults in the U.K. require studies using statistically valid sample sizes to measure annual variation and contributory lifestyle factors.

OBJECTIVES

To measure annual variation in the vitamin D status of U.K. South Asians, to determine the associated lifestyle influences, and to compare these with a similar study of white adults.

METHODS

A single-centre, prospective cohort study measuring circulating 25-hydroxyvitamin D [25(OH)D], sunlight exposure levels and lifestyle factors for 1 year in 125 ambulant South Asian adults with sun-reactive skin type V, aged 20-60 years, in Greater Manchester, U.K. (53·5°N).

RESULTS

The 25(OH)D levels of South Asians were alarmingly low. In summer, their median 25(OH)D level was 9·0 ng mL(-1) , [interquartile range (IQR) 6·7-13·1], falling to 5·8 ng mL(-1) (IQR 4·0-8·1) in winter. This compared with values in the white population of 26·2 ng mL(-1) (IQR 19·9-31·5) in summer and 18·9 ng mL(-1) IQR (11·6-23·7) in winter. Median daily dietary vitamin D was lower in South Asians (1·32 μg vs. 3·26 μg for white subjects) and was compounded by low supplement use. Despite similar times spent outdoors, ultraviolet (UV) dosimeters recorded lower personal UV exposure among South Asians, indicating sun avoidance when outside, while sun exposure diaries recorded lower amounts of skin surface exposure.

CONCLUSIONS

The majority of South Asians never reached sufficiency in vitamin D status. Lifestyle differences, with lower oral intake, sun exposure and rates of cutaneous production due to darker skin, indicate that standard advice on obtaining sufficient vitamin D needs modification for the South Asian community in the U.K.

The role of sunlight exposure in determining the vitamin D status of the U.K. white adult population

BACKGROUND

Vitamin D is necessary for bone health and is potentially protective against a range of malignancies. Opinions are divided on whether the proposed optimal circulating 25-hydroxyvitamin D [25(OH)D] level (≥ 32 ng mL⁻¹) is an appropriate and feasible target at population level.

OBJECTIVES

We examined whether personal sunlight exposure levels can provide vitamin D sufficient (≥ 20 ng mL⁻¹) and optimal status in the U.K. public.

METHODS

This prospective cohort study measured circulating 25(OH)D monthly for 12 months in 125 white adults aged 20-60 years in Greater Manchester. Dietary vitamin D and personal ultraviolet radiation (UVR) exposure were assessed over 1-2 weeks in each season. The primary analysis determined the post-summer peak 25(OH)D required to maintain sufficiency in wintertime.

RESULTS

Dietary vitamin D remained low in all seasons (median 3·27 μg daily, range 2·76-4·15) while personal UVR exposure levels were high in spring and summer, low in autumn and negligible in winter. Mean 25(OH)D levels were highest in September [28·4 ng mL⁻¹; 28% optimal, zero deficient (<5 ng mL⁻¹)], and lowest in February (18·3 ng mL⁻¹; 7% optimal, 5% deficient). A February 25(OH)D level of 20 ng mL⁻¹ was achieved following a mean (95% confidence interval) late summer level of 30·4 (25·6-35·2) and 34·9 (27·9-41·9) ng mL⁻¹ in women and men, respectively, with 62% of variance explained by gender and September levels.

CONCLUSIONS

Late summer 25(OH)D levels approximating the optimal range are required to retain sufficiency throughout the U.K. winter. Currently the majority of the population fails to reach this post-summer level and becomes vitamin D insufficient during the winter.

The impact of photosensitivity disorders on aspects of lifestyle

BACKGROUND

Photosensitivity disorders involve an abnormal skin reaction to sunlight exposure and affect a substantial percentage of the population. No previous studies have directly compared lifestyle attributes between photosensitive and healthy individuals.

OBJECTIVES

To assess the impact of photosensitivity on time spent outdoors in the U.K., holiday behaviour, use of sunscreens and vitamin D supplements, and employment status.

METHODS

Questionnaires were completed by ambulant photosensitive and healthy adults aged 18-60 years residing in Greater Manchester.

RESULTS

Forty-five adults with moderate-severe photosensitivity and 124 healthy adults completed the questionnaire. This revealed that photosensitive subjects spent significantly less time outdoors in the U.K. on both summer weekdays (P < 0·01) and summer weekends (P < 0·0001) than healthy subjects, took fewer holidays per year (P < 0·05), and spent less time outdoors on a sunny holiday (P < 0·0001). They wore clothing that covered a wider skin area (P < 0·0001), and use of sunscreen was greater (both frequency of application and area covered) in the photosensitive group outside of holiday time (P < 0·0001), but not when on a sunny holiday, as healthy people increased their sunscreen use at this time. Despite the reduced sun exposure, photosensitive subjects were no more likely to take vitamin D supplements than healthy subjects were; they also exhibited a significantly higher rate of unemployment (P < 0·05).

CONCLUSIONS

Photosensitivity disorders negatively influence lifestyle including employment status; more attention is required to the socioeconomic impact of these conditions.

Management of acute heart failure

Acute heart failure may be defined as the failure of the circulation to supply the demands of metabolising tissues due to acute cardiac dysfunction. First aid measures aimed at reducing symptomatology should be chosen with respect to their ability to improve cardiac function. The use of diuretics in acute heart failure does not sit well with the principle of improving cardiac function whereas the use of vasodilators does. As with any circulatory disturbance treatment must be guided by appropriate monitoring and the demands of metabolizing tissues must be reduced. Inotropes should be reserved for severe cases where other treatments have failed. This is to avoid the increased myocardial oxygen demand as a result of inotrope use.

The National Confidential Enquiry into Perioperative Deaths 2000: then and now

The most recent report from the National Confidential Enquiry into Perioperative Deaths (NCEPOD) was published on 21 November 2000 (Department of Health, 2000a). The data presented in the report relate to a randomized 10% sample of perioperative deaths occurring in the UK (excluding Scotland) occurring between 1 April 1998 and 31 March 1999. Comparisons are drawn in the report with the randomized 20% sample examined in 1990 (Department of Health, 1990).

Recognizing hypovolaemia

Clinical shock is a common problem of the critically ill patient. Assessment of the circulating volume is important to assure adequate oxygen supply to the tissues, and hypovolaemia must be treated promptly to avoid organ dysfunction. The author reviews the diagnostic approach, focusing on clinical and "surrogate" markers of volume status. Clinical signs are often late indicators and the monitoring of hemodynamic variables through cardiac catheterism can be misleading. The fluid challenge approach provides a useful diagnostic test of hypovolaemia, and a method for titrating the dose of fluid tailored to the individual's requirement.

Laboratory facilities and recommendations for the characterization of biological ultraviolet dosimeters

A laboratory facility for characterizing biological dosimeters for the measurement of UV radiation has been built and tested. The facility is based on a solar simulator, stabilized by photofeedback, and monitored by a spectroradiometer, with a versatile filter arrangement. This enables the following characteristics of the dosimeters to be ascertained: spectral response, linearity, and reciprocity; angular acceptance and response; calibration in simulated sunlight. The system has been tested on a variety of dosimeters and has the potential to be used with other radiometers, subject currently to the size of their active surface.

Report from the meeting: Gastrointestinal Tonometry: State of the Art. 22nd-23rd May 1998, London, UK

Gastrointestinal (GI) tonometry, the only clinically available method for the accurate diagnosis of compromised GI blood flow, has been shown to be a sensitive predictor of increased morbidity, mortality and prolonged hospitalization. The recent introduction of the Tonocap, as a means of performing automated air tonometry, has simplified the application of GI tonometry in the clinical setting. Despite this the utility of GI tonometry remains controversial. The GI Tonometry: State of the Art meeting brought together a group of clinicians with a proven track record of research, clinical interest and expertise in this field. The aim of the meeting was to come to a consensus regarding certain issues such as the past and future roles of GI tonometry and standards for its correct usage and interpretation. Finally suggestions as to further research and clinical evaluation were made within a broader discussion regarding the complexities of applying the principles of evidence-based medicine to the introduction of a new piece of medical technology.

The appropriate role of colloids in managing fluid imbalance: a critical review of recent meta-analytic findings

Three meta-analyses have recently been reported on the relationship between choice of resuscitation fluid and risk of mortality in critically ill patients. The relative risk of death (1.16-1.19) in two of the meta-analyses was slightly higher in colloid than crystalloid recipients; however, this observation was not statistically significant. In the third meta-analysis, 6% (95% confidence interval [CI], 3-9%) pooled excess mortality was documented in patients receiving albumin for hypovolaemia, burns or hypoalbuminaemia. The mortality difference in hypovolaemia patients (4%; 95% CI, 0-8%) was not statistically significant. A variety of serious limitations apply to the three meta-analyses, suggesting that their findings be interpreted cautiously. More than one-half of the randomized controlled trials (RCTs) included in the meta-analyses were reported prior to 1990 and hence do not reflect current practice. Each meta-analysis included only a subset of relevant RCTs, and therefore the scope of inferences to be drawn from the meta-analytic results is limited. The meta-analyses combined RCTs that were notably heterogeneous with respect to patient characteristics, type of illness, administered fluids and physiologic endpoints. Differences in illness severity, concomitant therapies and fluid management approaches were not taken into account. Very few of the RCTs were blinded. The meta-analyses do not support the conclusion that choice of resuscitation fluid is a major determinant of mortality in critically ill patients, nor do they support changes to current fluid management practice. Changes such as exclusive reliance on crystalloids would necessitate a reassessment of the goals and methods of fluid therapy. Since the effect on mortality may be minimal or non-existent, choice of resuscitation fluid should rest on whether the particular fluid permits the intensive care unit to provide better patient care.

Spectral UV irradiance on vertical surfaces: a case study

The UV spectral irradiance on horizontal and vertically oriented surfaces was measured throughout a cloudless day (18 July 1995) at Izana station, Tenerife, using a Bentham DTM300 spectroradiometer scanning from 290 to 500 nm in steps of 5 nm. Results show that irradiance measured on a horizontal surface is not proportional to irradiance on a vertical surface. The relation between the two depends upon orientation of the vertical surface, zenith angle and wavelength. At short UVB wavelengths surfaces directed toward the solar azimuth received their maximum irradiances much closer to solar noon than the maxima for longer wavelengths. Some vertical surfaces also received significantly more irradiance than the horizontal surface at long wavelengths during all but the central hours of the day, while at short wavelengths all vertical irradiances were less than the horizontal except for the measurements at the extreme ends of the day. Erythemally effective radiation followed the diurnal pattern of irradiations for short UVB wavelengths.

Relationship between preoperative endotoxin immune status, gut perfusion, and outcome from cardiac valve replacement surgery

STUDY OBJECTIVE

Endotoxin is a powerful trigger of systemic inflammation. Since cardiac surgery exposes patients to endotoxemia, this study was set up to define the relationship between preoperative endogenous endotoxin immune status, gut perfusion, and outcome following cardiac valve replacement surgery.

DESIGN

Observational study.

SETTING

University hospital.

PATIENTS

Fifty-nine consecutive patients undergoing cardiac valve replacement.

MEASUREMENTS AND MAIN RESULTS

Blood was assayed for IgG and IgM endotoxin core antibody (EndoCAb) levels preoperatively, immediately postoperatively, and at 4 h and 24 h postoperatively. Intraoperative gut mucosal perfusion was assessed using gastric tonometry. Complications were assessed for groups above and below the median EndoCAb value of a healthy population (100 median units micro/mL). Of the 59 patients, 12 developed at least one of a set of predefined complications. Of these 12, all had preoperative levels of IgM EndoCAb below 100 MU/mL (p<0.025). Eleven had IgG EndoCAb levels below 100 MU/mL (0.05<p<0.1). There was no relationship between the fall in gastric intramucosal pH and exposure to endotoxin as implied by the fall in unbound IgM EndoCAb levels, although the specificity of tonometry for predicting complications could be improved by considering the patient's preoperative EndoCAb status.

CONCLUSIONS

Preoperative EndoCAb levels were related to poor outcome following cardiac surgery and may be used to improve the specificity of GI tonometry in predicting postoperative complications.

Comparison of commonly used clinical indicators of hypovolaemia with gastrointestinal tonometry

OBJECTIVE

The gastrointestinal tonometer, which allows measurement of gastrointestinal mucosal CO2 and subsequent derivation of gut intramucosal pH (pHi), has been demonstrated to be a sensitive predictor of outcome following major surgery. Current theory suggests that the origin of the low pH may be hypovolaemia. This study was designed to compare the temporal sequence of changes in tonometric readings with invasive blood pressure, stroke volume, heart rate, lactate and arterial blood gas measurements during progressive haemorrhage.

DESIGN

Observational healthy volunteer study.

SETTING

Intensive care unit at University College London Hospitals.

SUBJECTS

Six healthy, medically qualified volunteers.

INTERVENTIONS

After obtaining baseline measurements, the subjects were progressively bled 25% (range = 21-31%) of their blood volume over a period of 1 h in two approximately equal aliquots. Equilibration was allowed for 30 min following the bleed, after which further measurements were made and the blood was then retransfused over 30 min.

MEASUREMENTS AND MAIN RESULTS

There was no consistent change in any of the haemodynamic variables other than gastric intramucosal CO2:arterial CO2 gap (PiCO2-PaCO2) after removal of the first aliquot of blood, although five of the six subjects also demonstrated a fall in pHi. After removal of the second aliquot of blood, PiCO2-PaCO2 gap and pHi continued to indicate a worsening gastric intramucosal acidosis; stroke volume, as measured by suprasternal Doppler, demonstrated a marked fall, while all other variables measured had not altered consistently or to such a degree as to elicit a clinical response or cause suspicion of a hypovolaemic state. On retransfusion, all variables returned towards baseline.

CONCLUSIONS

This study demonstrates the value of tonometry as an early monitor of hypovolaemia and highlights the shortcomings of other more commonly measured clinical variables.

Passive immunisation with IgG endotoxin core antibody hyperimmune fresh frozen plasma

Postoperative complications have been associated with low pre-operative endotoxin core antibody (EndoCAb) status. Seventy-three patients scheduled to undergo elective cardiac surgery were screened for IgG EndoCAb levels 1 week prior to admission. Of these 73 patients, 39 had levels below the median of a healthy population (100 MU = median units/ml). Only 6 received an infusion of IgG EndoCAb hyperimmune fresh frozen plasma (FFP) due to surgical rescheduling or unavailability of compatible hyperimmune FFP. The 6 patients demonstrated significant elevation (p < 0.0001) of their IgG EndoCAb levels from a mean level of 43 MU/ml (range: 26-75) to a posttransfusion mean of 267 MU/ml (range: 227-300), which persisted until at least immediately prior to the operative period. We conclude that passive immunisation with EndoCAb hyperimmune FFP is possible prior to elective surgery and that the kinetic profile of such an administration will allow the FFP to be given the night prior to surgery and still maintain significantly elevated levels for surgery planned the following morning.

Haemostatic changes in the pulmonary blood during cardiopulmonary bypass

Pulmonary injury may result from the use of cardiopulmonary bypass (CPB). We investigated changes in the haemostatic system in the pulmonary vein during CPB compared with blood that circulated through the bypass circuit. Paired samples were taken from the pulmonary vein and central venous pressure (CVP) line during the peri-operative period from ten patients. Plasma levels of factor VII (P < 0.001), prekallikrein (P < 0.05), antithrombin III (P < 0.001) and heparin cofactor II (P < 0.005) were decreased in the pulmonary vein after 20 min of bypass compared with pre-operative levels. In the pulmonary vein there was a significant increase in neutrophil expressed CD11b (P < 0.001), neutrophil elastase: alpha 1-antitrypsin complexes (P < 0.001), endothelin-1(P < 0.001) and thrombin-antithrombin complexes (P < 0.001) by the end of bypass compared with pre-operative levels. There was no significant change in monocyte expressed CD11b, factor XII or C1-esterase inhibitor in the pulmonary vein for the study period. None of these variables were significantly different in the pulmonary vein compared with CVP line. In the pulmonary vein plasma levels of activated factor VII decreased following heparin administration (P < 0.001) in the majority of patients which was coincidental to an increase (P < 0.001) in tissue factor pathway inhibitor (TFPI). This increase in TFPI was significantly higher in the pulmonary vein compared with CVP line (P < 0.05) There was a decrease in neutrophil count by 20 min on CPB in both the pulmonary vein and CVP line (P < 0.001) and this did not return to pre-operative levels in the pulmonary vein. Soluble thrombomodulin levels decreased by 20 min on CPB in the CVP line (P < 0.05) but tended to increase in the pulmonary vein, although this was not statistically significant. In conclusion we found evidence of thrombin generation and possible endothelial damage together with increased neutrophil activation and adhesion molecule expression in the pulmonary vein during CPB which may play an important role in the development of post-CPB pulmonary injury.

Perioperative plasma volume expansion reduces the incidence of gut mucosal hypoperfusion during cardiac surgery

OBJECTIVE

To test the hypothesis that perioperative plasma volume expansion would preserve gut mucosal perfusion during elective cardiac surgery.

DESIGN

Prospective randomized open study.

SETTING

Teaching hospital.

PATIENTS

Sixty American Society of Anesthesiology grade III patients with a preoperative left ventricular ejection fraction of 50% or greater undergoing elective cardiac surgery.

INTERVENTIONS

Patients were allocated randomly to a control or protocol group. The control group was treated according to standard practices. After induction of general anesthesia, the protocol group received, in addition, 200-mL boluses of a 6% hydroxyethyl starch solution to obtain a maximum stroke volume. This procedure was repeated every 15 minutes until the end of surgery, except when the patient underwent cardiopulmonary bypass.

MEASUREMENTS AND RESULTS

Cardiac stroke volume was estimated by an esophageal Doppler system, and gastric mucosal perfusion was measured by tonometric assessment of gastric intramucosal pH in all patients. Patients were followed up postoperatively until discharge from the hospital or death. The incidence of gut mucosal hypoperfusion (gastric intramucosal pH < 7.32) at the end of surgery was reduced in the protocol group (7% vs 56%) (P < .001), as were the number of patients in whom major complications developed (0 vs 6) (P = .01), mean number of days spent in the hospital (6.4 [range, 5 to 9] vs 10.1 [range, 5 to 48]) (P = .011), and mean number of days spent in the intensive care unit (1 [range, 1 to 1] vs 1.7 [range 1 to 11] days) (P = .023).

CONCLUSIONS

Perioperative plasma volume expansion with colloid during cardiac surgery, guided by esophageal Doppler measurement of cardiac stroke volume, reduced the incidence of gut mucosal hypoperfusion. This group of patients also had an improved outcome when compared with controls.

Maintaining blood flow in the extracorporeal circuit: haemostasis and anticoagulation

OBJECTIVES

To review the methods and developments in maintaining extracorporeal circuits in critically ill patients.

DESIGN

The review includes details of the pathophysiological processes of haemostasis and coagulation in critically ill patients, methods of maintaining blood flow in the extracorporeal circuit and methods of monitoring anticoagulation agents used.

SETTING

Information is relevant to the management of critically ill patients requiring extracorporeal renal and respiratory support and cardiopulmonary bypass.

CONCLUSIONS

Heparin is the mainstay of anticoagulation for the extracorporeal circuit although the complex abnormalities of the coagulation system in critically ill patients are associated with a considerable risk of bleeding. Alternative therapeutic agents and physical strategies (prostacyclin, low molecular weight heparin, sodium citrate, regional anticoagulation, heparin bonding and attention to circuit design) may reduce the risk of bleeding but expense and difficulty in monitoring are disadvantages.

Phaeochromocytoma presenting as acute hyperamylasaemia and multiple organ failure

Phaeochromocytoma may present in many different ways. We report an unusual presentation of phaeochromocytoma in a man with hyperamylasaemia and multiple organ failure thought to be due to acute relapsing pancreatitis. Abdominal ultrasound and computerised tomography (CT) examinations revealed a mass at the tail of the pancreas. Fine needle biopsy of the mass precipitated headache, intense vasoconstriction and labile blood pressure. He proceeded to laparotomy, at which an 8 x 9 cm mass was found to be replacing the left adrenal gland. Histological examination revealed a phaeochromocytoma. This case illustrates that hyperamylasaemia and multiple organ failure may be unusual presentations of phaeochromocytoma and may be unusual presentations of phaeochromocytoma and phaeochromocytoma should be considered in the differential diagnosis of a peripancreatic mass found by ultrasound or CT.

An evaluation of the microbial retention performance of three ventilator-circuit filters

OBJECTIVES

to determine and compare the microbial retention efficiency of 3 types of heat and moisture exchange (HME) filters.

DESIGN

randomised prospective study.

SETTING

Intensive Care Unit at the Middlesex Hospital and the microbiology laboratory of the Department of Academic Microbiology, University College London Medical School.

MEASUREMENTS AND RESULTS

An aerosol challenge to each filter using a suspension containing. S. marcescens and the bacteriophage MS2. In total 45 filters of 3 types were tested, 15 previously unused and 30 that had been used in ventilator circuits of 30 patients. The 3 types of filter generally had microbial retention efficiencies of > 99.99% for both S. marcescens and the bacteriophage MS2.

CONCLUSION

The 3 types of HME filter were effective microbial filters and comparable in their microbial retention.

Low intramucosal pH is associated with failure to acidify the gastric lumen in response to pentagastrin

OBJECTIVE

To determine if low gastric intramucosal pH is associated with impaired secretion of gastric acid after pentagastrin stimulation.

DESIGN

Prospective study.

SETTING

Intensive care unit of a university teaching hospital.

PATIENTS

20 patients requiring mechanical ventilation.

INTERVENTIONS

All patients with a gastric luminal pH > 4 were given pentagastrin 6 micrograms/kg s.c. to stimulate gastric acid secretion and the response assessed by further measurements of gastric luminal pH.

MEASUREMENTS AND RESULTS

Gastric intramucosal pH (pHi) and luminal pH (pHL) were measured. Patients were divided into two groups on the basis of a low or normal pHi (A value of 7.35 was taken as the lower limit of normal). Patients (n = 6) with normal pHi (7.40 +/- 0.05 [mean +/- SD]) and a luminal pH > 4 (5.65 +/- 1.25) all had a decrease in pHL in response to pentagastrin (decrease in pHL 4.02 +/- 1.52). Of the patients (n = 7) with low pHi (7.2 +/- 0.13) and a pHL > 4 (6.51 +/- 0.48) only one responded to pentagastrin (decrease in pHL for this group 0.93 +/- 1.86). Patients with a pHL < 4 (2.4 +/- 0.71) were not given pentagastrin (n = 7).

CONCLUSION

Some critically ill patients with low gastric intramucosal pH appear to have an impaired ability to acidify the gastric lumen in response to pentagastrin.

Epidermis and serum protect retinol but not retinyl esters from sunlight-induced photodegradation

Sunlight-induced photodegradation of retinyl esters and retinol in human skin, blood and cultured keratinocytes was investigated. Using high-performance liquid chromatography with an extraction method that avoided saponification, the analysis of human foreskin (Caucasian) showed that levels of retinyl esters and retinol were approximately 3.5 and 5.0 times higher, respectively, in the epidermis than in the dermis. Upon irradiation by sunlight, a significant reduction in epidermal retinyl esters was observed in both summer and winter. However, epidermal retinol, dermal retinol and dermal retinyl esters did not show statistically significant reductions. When serum from volunteers who had taken a large dose of retinyl palmitate to elevate serum retinyl esters was exposed to sunlight, the retinyl esters in the serum rapidly disappeared after 10 min of exposure--similar to the photodegradation seen for retinyl palmitate in an organic solvent. While retinol in an organic solvent rapidly photodegraded similar to serum retinyl palmitate, serum retinol slowly declined upon sunlight irradiation. When cultured keratinocytes that took-up 3H-retinol and thereafter contained 3H-retinyl esters and 3H-retinol were exposed to sunlight, 80% of the 3H-retinyl esters disappeared upon sunlight irradiation whereas only about 20% of the 3H-retinol did so. These results suggest that the epidermis, serum and keratinocytes selectively protect retinol from sunlight-induced photodegradation. It is most likely that serum retinol-binding protein and cellular retinol-binding protein protect retinol, a vital epithelial growth factor, from photodegradation.

Intra-operative gut mucosal hypoperfusion is associated with increased post-operative complications and cost

OBJECTIVES

To determine CO and gastric mucosal perfusion in patients during elective major surgery; to seek a relationship with subsequent outcome.

DESIGN

Prospective descriptive study.

SETTING

University hospital.

PATIENTS

51 patients undergoing elective major surgery of an anticipated duration of greater than 2 h who were at risk of developing gut mucosal hypoperfusion and postoperative organ failure.

MEASUREMENTS AND RESULTS

CO was determined by oesophageal Doppler measurement of aortic blood flow. Gastric mucosal perfusion was determined by tonometric assessment of gastric mucosal pH (pHi). Blood pressure and urine flow were measured. At the end of surgery no patients were oliguric or hypotensive. Post-operatively morbidity, mortality, duration and cost of stay in the ITU and hospital were assessed. There were 32 patients with evidence of gastric mucosal ischaemia at the end of surgery (pHi < 7.32) despite maintenance of CO. This group of patients spent a mean of 4.7 (range 0-33) days in the ITU, 14 developed major complications (7 with multiple organ failure [MOF] and 6 died. In 19 patients gut mucosal perfusion was maintained during surgery (pHi > or = 7.32); these patients demonstrated an increase in CO of 48.4% (95% confidence interval 21.3 -75.6) and spent a mean of 1.0 (range 0-4) days in the ITU. Only one developed a major complication and none died. The total cost of post-operative care for the 51 patients was estimated at pounds 356650. Mean cost per patient in the low pHi group was significantly greater at pounds 8845 (range pounds 600--pounds 42,700) compared to pounds 3874 (range pounds 2,600--pounds 9,600) in the normal pHi group. The total.cost of post-operative care for the 7 patients who developed MOF was pounds 171,450 i.e. 48% of the total cost.

CONCLUSION

A low gastric pHi measured during the intraoperative period in a group of patients undergoing major (mainly cardiovascular) surgery is associated with increased post-operative complications and cost.

The effect of hydroxyethyl starch and other plasma volume substitutes on endothelial cell activation; an in vitro study

OBJECTIVE

To study the effect of medium molecular weight hydroxyethyl starches on endothelial cell and neutrophil activation in vitro.

SETTING

Laboratory analysis.

METHODS

The effects of albumin and hydroxyethyl starch on the neutrophil adhesion molecule (CD11bCD18), with and without lipopolysaccharide stimulation, were studied in whole blood. E-selectin expression on human umbilical vein endothelial cells was stimulated with lipopolysaccharide alone and in the presence of either albumin or hydroxyethyl starch. The effect of albumin and hydroxyethyl starches on rapid endothelial cell activation was studied using von Willebrand factor release as a marker.

MEASUREMENTS AND RESULTS

Hydroxyethyl starches but not albumin inhibited stimulated vWF release in a dose dependent manner. No effect was seen on endothelial E-selectin or neutrophil CD11bCD18 expression.

CONCLUSIONS

these results suggest a possible beneficial role of hydroxyethyl starches in the inhibition of endothelial activation thus preventing neutrophil adhesion during sepsis syndrome.

The rational administration of colloids

The safe administration of i.v. fluids is one of the most significant advances in the care of critically ill patients this century. However, despite advances in the monitoring of cardiovascular variables, the questions of what? when? and how much? remain areas of enormous controversy. Ironically as the choice of i.v. fluids becomes greater and the monitoring more sophisticated the controversy grows. This article will concentrate on the diagnosis of hypovolaemia, the consequences of hypovolaemia and the rational use of i.v. fluids, particularly colloids, to treat it.

The role of endotoxin immunity, neutrophil degranulation and contact activation in the pathogenesis of post-operative organ dysfunction

Gut mucosal hypoperfusion is associated with a poor outcome following major surgery but the pathogenetic mechanisms remain poorly understood. We have examined the relationship between gut mucosal hypoperfusion, endotoxin core antibodies (EndoCAb), neutrophil elastase alpha-1 antitrypsin complexes (NE) and components of the contact system during elective major surgery. Of the 26 patients studied 16 developed gut mucosal hypoperfusion (pHi < 7.32) by the end of surgery; of these four developed multiple organ failure (MOF) and three subsequently died. In this group there was a significant rise in NE (P < 0.005) and significant reductions in components of the contact system (factor XII, antithrombin III, prekallikrein and C1-inhibitor; P < 0.001) from immediately before surgery to 24 h later. Ten patients maintained gut mucosal perfusion (pHi > or = 7.32); none of these developed life threatening complications. In this group there was no significant increase in NE and, although there were significant reductions in some components of the contact system (P < 0.01), levels of C1-INH were not reduced. All patients demonstrated a significant reduction in both IgG and IgM EndoCAbs (P < or = 0.005) indicating exposure to endotoxin. However, the group that maintained gut mucosal perfusion had significantly higher IgG EndoCAb levels at baseline and 24 h (P < or = 0.005). These data suggest that all patients were exposed to endotoxin and that high levels of anti-endotoxin antibodies may contribute to the prevention of endotoxin-induced contact activation, neutrophil degranulation and gut mucosal hypoperfusion occurring during major surgery and thus reduce the likelihood of the development of post-operative MOF.

Postoperative multiple organ dysfunction syndrome associated with gut mucosal hypoperfusion, increased neutrophil degranulation and C1-esterase inhibitor depletion

We have examined the relationship between gut mucosal perfusion, as determined by gastric intramucosal pH (pHi), changes in plasma neutrophil elastase concentrations and components of the contact system during elective major surgery and related these findings to patient outcome. Of the 26 patients studied, 16 developed gut mucosal hypoperfusion (pHi < 7.32) by the end of surgery; four of these developed multiple organ dysfunction syndrome; three of these died. In this group there was a significant increase in neutrophil elastase (P < 0.005) and significant reductions in plasma components of the contact system from immediately before surgery to 24 h later. Ten patients maintained gut mucosal perfusion (pHi > or = 7.32); none of these developed life threatening complications. In this group there was no significant increase in neutrophil elastase and, although there were significant reductions in some plasma components of the contact system, concentrations of C1-esterase inhibitor (the main inhibitor of the contact system) were not significantly reduced. We conclude that gut mucosal hypoperfusion, neutrophil degranulation and activation of the contact system to the extent that C1-esterase inhibitor becomes depleted are associated with a poor outcome after major surgery.