Clinician perception of a novel cardiovascular lifestyle prescription form in the primary and secondary care setting in Wales, UK

ISSUES ADDRESSED

To establish the views of clinicians on the feasibility and effectiveness of using a novel lifestyle prescription form (LRx) which requires co-signing by clinician and patient and is uniquely based on the design of the standard drug prescription form, in the primary and secondary health care settings.

METHODS

Thirty-six participants were issued with a "prescription" pad, of 20 LRx scripts, for 1 month and requested to issue an LRx prescription to patients they deemed suitable during their consultation, recording their reason for use of the LRx. Each clinician was then asked to complete a comprehensive feedback questionnaire.

RESULTS

Feedback of the LRx was overwhelmingly positive. The script was viewed as a more effective way to convey and support cardiovascular lifestyle advice, than usual care. Forty per cent (196 of 480) of the LRx scripts that were provided to primary and secondary care clinicians during the study period were issued. In most consultations, the LRx script was issued to reaffirm dietary advice. Nurses and health care assistants were more likely than doctors to use the LRx in response to a request for lifestyle advice from a patient.

CONCLUSIONS

The LRx may be a useful addition to the clinician's communication toolkit to stimulate lifestyle behaviour changes in their patients. The main barrier to use in the study was lack of consultation time. SO WHAT?: Issuing the LRx is a method of solidifying lifestyle advice that clinicians could utilise, providing them with another tool in their behaviour change arsenal, particularly with familiarity with the tool.

Prolonged deterioration of endothelial dysfunction in response to postprandial lipaemia is attenuated by vitamin C in Type 2 diabetes

BACKGROUND

Endothelial dysfunction (ED) has been described in Type 2 diabetes (T2DM). We have described previously a diminution of flow-mediated arterial dilatation and, by implication, further ED in T2DM in response to postprandial lipaemia (PPL) at 4 h. This is possibly mediated by oxidative stress/alteration of the nitric oxide (NO) pathway. T2DM subjects tend to exhibit both exaggerated and prolonged PPL. We therefore studied the relationship of PPL to the duration of ED in T2DM subjects and oxidative stress with or without the antioxidant, vitamin C.

METHODS

Twenty subjects with T2DM with moderate glycaemic control (mean HbA1c 8.4%) were studied. After an overnight fast, all subjects consumed a standard fat meal. Endothelial function (EF), lipid profiles, and venous free radicals were measured in the fasting, peak lipaemic phase (4 h) and postprandially to 8 h. The study was repeated in a double-blinded manner with placebo, vitamin C (1 g) therapy for 2 days prior to re-testing and with the fat meal. Oxidative stress was assessed by lipid-derived free radicals in plasma, ex vivo by electron paramagnetic resonance spectroscopy (EPR) and by markers of lipid peroxidation (TBARS). Endothelial function was assessed by flow-mediated vasodilatation (FMD) of the brachial artery.

RESULTS

There was a significant decrease in endothelial function in response to PPL from baseline (B) 1.3 +/- 1.3% to 4 h 0.22 +/- 1.1% (P < 0.05) and 8 h 0.7 +/- 0.9% (P < 0.05) (mean +/- sem). The endothelial dysfunction seen was attenuated at each time point with vitamin C. Baseline EF with vitamin C changed from (fasting) 3.8 +/- 0.9-2.8 +/- 0.8 (at 4 h) and 2.9 +/- 1.3 (at 8 h) in response to PPL. Vitamin C attenuated postprandial (PP) oxidative stress significantly only at the 4-h time point [301.1 +/- 118 (B) to 224.7 +/- 72 P < 0.05] and not at 8 h 301.1 +/- 118 (B) to 260 +/- 183 (P = NS). There were no changes with placebo treatment in any variable. PPL was associated with a PP rise in TG levels (in mmol/l) from (B) 1.8 +/- 1 to 2.7 +/- 1 at 4 h and 1.95 +/- 1.2 at 8 h (P = 0.0002 and 0.33, respectively).

CONCLUSION

PPL is associated with prolonged endothelial dysfunction for at least 8 h after a fatty meal. Vitamin C treatment improves endothelial dysfunction at all time points and attenuates PPL-induced oxidative stress. This highlights the importance of low-fat meals in T2DM and suggests a role for vitamin C therapy to improve endothelial function during meal ingestion.

Platelet nitrate responsiveness in fasting and postprandial type 2 diabetes

Vascular responsiveness to exogenous nitrates in type 2 diabetes (T2DM) is attenuated in brachial and coronary vessels. We determined platelet responsiveness to nitric oxide (NO) in T2DM and control subjects. We examined whether the postprandial (PP) state affected platelet sensitivity to NO donors in T2DM patients and the extent of correlation between this and measures of oxidative stress, compared to changes in endothelial function. Twelve T2DM subjects were studied fasting and four hours after a test meal and compared with 15 healthy controls. We assessed the inhibitory effects of NO donors on adenosine 5'-diphosphate (ADP)-induced platelet aggregation. Oxidative stress was assessed by lipid-derived free radicals, ex vivo by electron paramagnetic resonance spectroscopy and markers of lipid peroxidation. Endothelial function was assessed by flow-mediated vasodilatation (FMD) of the brachial artery. Results are expressed as (mean +/- SEM). Fasting platelet aggregation was increased in diabetics versus controls (14.86 +/- 1.1 Ohms vs. 10.76 +/- 1.1 Ohms, p < 0.05). Sodium nitroprusside (SNP) and glyceryl trinitrate (GTN) inhibited ADP-induced aggregation by 73.1 +/- 5.9% and 50.3 +/- 7.7% in healthy controls compared to 15.4 +/- 7% and 19.5 +/- 8.2% in T2DM (p < 0.05). Fasting and postprandial inhibition of platelet aggregation with NO donors in T2DM was similar. T2DM patients had higher levels of oxidative stress in the fasting state and postprandially. There were no PP correlations with platelet NO resistance. In conclusion, there is platelet hyporesponsiveness to NO donors (SNP/GTN) in T2DM compared to controls, with increased ADP-induced platelet aggregation. Platelet abnormalities were associated with increased oxidative stress.

Racial differences in responses to drug treatment: implications for pharmacotherapy of heart failure

Chronic heart failure (CHF) is a common disease with high associated morbidity and mortality, and the outcome appears to be worse in black compared with white patients. There is currently no clear consensus for basing the pharmacological treatment of CHF on racial differences. Most studies that have investigated the potential effects of racial differences on pharmacological responses in heart failure have been based on African Americans and white participants. Using these data, this review will discuss the current understanding of the effects of racial differences in response to pharmacotherapy in heart failure, possible mechanisms for these observed differences, and how this may impact on patient management. Diuretics have favorable symptomatic benefits in both black and white patients with heart failure with evidence of fluid retention. ACE inhibitors seem to be less effective in the treatment of black patients with heart failure compared with white patients. This may be due to low pre-existing activity of the renin-angiotensin system in blacks. The role of angiotensin receptor blockers (ARBs) in the management of all patients with heart failure is incompletely defined and there are no clear trial data to show any difference in effect between black and white patients with heart failure. There is good evidence for the use of spironolactone in all patients with heart failure, but no evidence for a different effect in black patients. Similarly, there is no conclusive data to suggest a difference in effect of digoxin in different racial groups. The evidence available would suggest that certain beta-adrenoceptor antagonists (certainly carvedilol but not bucindolol) are effective in both black and white patients with CHF. The combination of hydralazine and nitrates would appear to be particularly effective in black patients with CHF though the African American Heart Failure Trial (A-HeFT) trial should provide clearer evidence for the potentially greater beneficial effects of these two drugs in the black population. It is important to accept that racial categorization acts as only a surrogate marker for genetic or other factors responsible for individual responses to drug therapy and that any identified differences will not apply to all members of each stratified group. Nonetheless, in managing a complex, common and often fatal condition such as heart failure, recognizing potential individual differences in drug responses should enable the responsible clinician to provide a tailored and evidence-based approach to patient treatment.

Determinants of platelet responsiveness to nitric oxide in patients with chronic heart failure

Congestive heart failure (CHF) is associated with oxidative stress. Platelet responsiveness to nitric oxide (NO) donors, are impaired in patients with angina pectoris, possibly by increasing oxidative stress. We investigated the occurrence of platelet resistance to NO in patients, with ischaemic or non-ischaemic cardiomyopathy compared with normal subjects. Anti-aggregatory effects of sodium nitroprusside (SNP), oxidative stress and whole blood superoxide anion content were determined, with correlates of responsiveness to SNP. Inhibition of platelet aggregation by SNP was 65.4+/-3.55% in controls and 59.3+/-4.1% in CHF (P=ns) despite increased oxidative stress and post-aggregation O2- in CHF patients. However, subsets of CHF patients have NO-resistant platelets: this is associated with increasing age and/or increased oxidative stress (both p<0.05).

Role of nitric oxide and oxidative stress in baroreceptor dysfunction in patients with chronic heart failure

Abnormalities of autonomic control of the cardiovascular system are seen in chronic heart failure (CHF) and confer a poor prognosis. Nitric oxide appears to be important in the regulation of baroreflex control in health and in disease states. The antioxidant vitamin C increases nitric oxide bioavailability in CHF. We evaluated the effects of vitamin C on baroreceptor sensitivity (BRS) by sequence analysis in 100 CHF patients and 44 control subjects. Groups of 55 CHF patients and 22 controls were randomly allocated to receive a single intravenous injection of vitamin C (2 g) or placebo. In addition, 45 CHF patients were randomly allocated to receive a 4-week course of oral vitamin C (4 g/day) or placebo. An age-related reference range for BRS was developed in 22 healthy controls matched for age and gender to the CHF group. BRS was significantly impaired in the CHF group compared with age-matched older controls and young controls (6.9 +/- 3.1, 12.5 +/- 4.9 and 21.7 +/- 9.1 mmHg/ms respectively; P < 0.001 between groups). Intravenous vitamin C acutely improved BRS in CHF patients by 24% (by 1.8 +/- 4.1 mmHg/ms; P < 0.05), but not in controls. There was no improvement in BRS in CHF patients given chronic oral vitamin C. Thus acute intravenous, but not chronic oral, vitamin C improved BRS in CHF patients. There was no effect of intravenous vitamin C in healthy subjects, suggesting that the mechanism was either by free radical scavenging or due to central effects.

Addition of candesartan to angiotensin converting enzyme inhibitor therapy in patients with chronic heart failure does not reduce levels of oxidative stress

BACKGROUND

Angiotensin II exerts a number of harmful effects in patients with chronic heart failure (CHF) and, through an increase in oxidative stress, is thought to be critical in the development of endothelial dysfunction. Angiotensin II may be elevated in CHF despite treatment with angiotensin converting enzyme (ACE) inhibitors, producing a rationale for adjunctive angiotensin receptor blockade. We investigated whether the addition of angiotensin antagonism to ACE inhibition would reduce oxidative stress and improve endothelial function and exercise tolerance in patients with chronic heart failure.

METHODS AND RESULTS

Twenty-eight heart failure patients, who were on stable ACE inhibitor therapy, were randomised to receive adjunctive therapy with candesartan or placebo. Plasma lipid-derived free radicals, TBARS and neutrophil O2-generation, markers of oxidative stress, were measured in venous blood. Arterial endothelial function was assessed as the response of the brachial artery to flow-related shear stress. Exercise capacity was determined by cardiopulmonary exercise testing. Compared with placebo, candesartan had no effect on changes in lipid derived free radicals (-0.1+/-1.2 vs. -0.1+/-1.0 units, respectively, P=NS), TBARS (-2.2+/-1.1 vs. -2.6+/-2.2 micromol/l, respectively, P=NS) or neutrophil O2-generating capacity (-7.3+/-5.1 vs. -8.4+/-7.9 mV/5x10(5) neutrophils, respectively, P=NS). There was no effect on changes in brachial artery flow-mediated dilatation (0.5+/-1.0 vs. 0.8+/-1.3%, respectively, P=NS) nor peak VO2 (1.6+/-0.7 ml/kg per min vs. 1.8+/-0.6 ml/kg per min; P=NS).

CONCLUSION

The addition of the candesartan to ACE inhibitor therapy had no effect on oxidative stress and did not improve endothelial function or exercise capacity in patients with CHF.

Acute effects of vitamin C on platelet responsiveness to nitric oxide donors and endothelial function in patients with chronic heart failure

Chronic heart failure (CHF) is characterized by a prothrombotic state, which may relate to increased platelet aggregability, endothelial dysfunction, and increased oxidative stress. We investigated the effect of vitamin C in CHF on ex vivo platelet aggregation and platelet responsiveness to the anti-aggregatory effects of the nitric oxide (NO) donors glyceryl trinitrate (GTN) and sodium nitroprusside (SNP). We also examined parameters of oxidative stress and endothelial function in patients. In this double-blind, randomized, crossover study vitamin C (2 g) or placebo was given intravenously to 10 patients with CHF. We measured adenosine 5-diphosphate (ADP)-induced platelet aggregation, flow-mediated dilatation (FMD) in the brachial artery using ultrasonic wall-tracking, and plasma levels of lipid-derived free radicals using electron paramagnetic resonance spectroscopy. Vitamin C did not affect ex vivo platelet aggregability but enhanced the inhibition of platelet aggregation by SNP (62.7+/-10.2 to 82.7+/-4.8%, p = 0.03) and tended to increase responses to GTN (40.5+/-9.0 to 53.4+/-7.3, p = 0.06). The effect of vitamin C on platelet responsiveness to the antiaggregatory effects of SNP was inversely related to basal response to SNP (r = -0.9, p < 0.01); a similar trend was observed with GTN (r = -0.6, p = 0.1). Vitamin C also increased FMD (1.9+/-0.6 to 5.8+/-1.5%, p = 0.02) and reduced plasma lipid-derived free radicals by 49+/-19% (p < 0.05). In patients with CHF acute intravenous administration of vitamin C enhances platelet responsiveness to the anti-aggregatory effects of NO donors and improves endothelial function, suggesting a potential role for vitamin C as a therapeutic agent in CHF.

Preservation of venous endothelial function in the forearm venous capacitance bed of patients with chronic heart failure despite arterial endothelial dysfunction

OBJECTIVES

The goal of this study was to assess whether endothelial dysfunction occurs in the forearm venous capacitance bed of patients with chronic heart failure (CHF) and to determine the role of nitric oxide (NO) in modulating venous tone.

BACKGROUND

Control of venous tone is crucially important in CHF. More than 70% of blood volume lies in the venous capacitance beds. Therefore, small changes in venous tone may markedly affect cardiac filling pressures and cardiac output.

METHODS

Venous tone was measured using radionuclide forearm venous plethysmography in 24 patients with CHF and 16 age-matched controls. The effect of basal NO activity on venous tone was assessed by infusing N-monomethyl-L-arginine 12 mg/min and stimulated NO using carbachol 15 microg/min. Brachial artery flow-mediated dilation was assessed by ultrasonic wall-tracking.

RESULTS

Blockade of basal NO release caused a significant and similar venoconstriction in patients (9.6 +/- 1.8%, p < 0.01) and controls (6.6 +/- 1.7%, p < 0.01). Carbachol-induced venodilation was significant and similar in patients (36.8 +/- 3.9%, p < 0.001) and controls (40.7 +/- 3.9%, p < 0.001). Brachial artery flow-mediated dilation was impaired in patients compared with controls (2.0 +/- 0.6% vs. 7.5 +/- 2.5%, p < 0.01).

CONCLUSIONS

Our data indicate that, despite marked impairment of the function of the arterial endothelium, there is preservation of both basal and stimulated NO release in the forearm venous capacitance bed. This may provide important insights into mechanisms of endothelial dysfunction in CHF and the potential for novel therapy.

The relationships between post-prandial lipaemia, endothelial function and oxidative stress in healthy individuals and patients with type 2 diabetes

Post-prandial lipaemia (PPL) is a factor in atherogenesis and results in reversible endothelial dysfunction in healthy individuals. Oxidative stress and triglyceride (TG)-rich lipoproteins have been implicated. Type 2 diabetes (NIDDM) results in exaggerated PPL. We attempted to delineate the mechanisms of PPL induced, endothelial dysfunction (EF) and oxidative stress in 12 NIDDM and 12 matched healthy subjects. Subjects underwent a fat tolerance test, with endothelial function assessed by flow-mediated vasodilatation and oxidative stress measured by venous lipid-derived free radicals ex vivo and lipid peroxidation products over the postprandial phase. Fasting TG, post-prandial hypertriglyceridaemia and the TG enrichment of all lipoproteins was significantly greater in NIDDM. Post-prandial endothelial function inversely correlated with fasting HDL-C (r=-0.84, P=0.001) in both the control and NIDDM groups. The deterioration in EF in the NIDDM group also correlated with TG enrichment of VLDL and LDL. PPL in both groups also resulted in increased oxidative stress. The increment in free radicals correlated with TG enrichment of VLDL in both groups and was, therefore, greater in NIDDM. Thus, PPL -- with the production of TG-enrichment of VLDL -- results in endothelial dysfunction by an oxidative stress mechanism in both groups. The magnitude is greater in NIDDM. Fasting HDL-C appears to contribute to the protection of the endothelium against this phenomenon. Hence, exaggerated PPL associated with reduced HDL-C may be important in the pathogenesis of vascular disease, particularly in NIDDM.

Neutrophil superoxide anion--generating capacity, endothelial function and oxidative stress in chronic heart failure: effects of short- and long-term vitamin C therapy

OBJECTIVES

First, we sought to study the effects of short- and long-term vitamin C therapy on oxidative stress and endothelial dysfunction in chronic heart failure (CHF), and second, we sought to investigate the role of neutrophils as a cause of oxidative stress in CHF.

BACKGROUND

Oxidative stress may contribute to endothelial dysfunction in CHF. Vitamin C ameliorates endothelial dysfunction in CHF, presumably by reducing oxidative stress, but this is unproven.

METHODS

We studied 55 patients with CHF (ischemic and nonischemic etiologies) and 15 control subjects. Flow-mediated dilation (FMD) in the brachial artery was measured by ultrasound wall-tracking, neutrophil superoxide anion (O2-) generation by lucigenin-enhanced chemiluminescence and oxidative stress by measurement of free radicals (FRs) in venous blood using electron paramagnetic resonance (EPR) spectroscopy and plasma thiobarbituric acid reactive substances (TBARS). Measurements were performed at baseline in all subjects. The effects of short-term (intravenous) and long-term (oral) vitamin C therapy versus placebo were tested in patients with nonischemic CHF.

RESULTS

At baseline, FRs were higher in patients with CHF than in control subjects (p < 0.01), TBARS were greater (p < 0.005), neutrophil O2- -generating capacity was enhanced (p < 0.005) and FMD was lower (p < 0.0001). Compared with placebo, short-term vitamin C therapy reduced FR levels (p < 0.05), tended to reduce TBARS and increased FMD (p < 0.05), but did not affect neutrophil O2- -generating capacity. Long-term vitamin C therapy reduced FR levels (p < 0.05), reduced TBARS (p < 0.05) and improved FMD (p < 0.05), but also reduced neutrophil O2- -generating capacity (p < 0.05). Endothelial dysfunction was not related to oxidative stress, and improvements in FMD with vitamin C therapy did not relate to reductions in oxidative stress.

CONCLUSIONS

Oxidative stress is increased in ischemic and nonischemic CHF, and neutrophils may be an important cause. Vitamin C reduces oxidative stress, increases FMD and, when given long term, decreases neutrophil O2- generation, but the lack of a correlation between changes in endothelial function and oxidative stress with vitamin C implies possible additional non-antioxidant benefits of vitamin C.

Ciprofibrate therapy improves endothelial function and reduces postprandial lipemia and oxidative stress in type 2 diabetes mellitus

BACKGROUND

Exaggerated postprandial lipemia (PPL) is a factor in atherogenesis, involving endothelial dysfunction and enhanced oxidative stress. We examined the effect of ciprofibrate therapy on these parameters in type 2 diabetes mellitus.

METHODS AND RESULTS

Twenty patients entered a 3-month, double-blind, placebo-controlled study. Each subject was studied fasting and after a fatty meal, at baseline, and after 3 months of treatment. Glucose and lipid profiles were measured over an 8-hour postprandial period. Endothelial function (flow-mediated endothelium-dependent vasodilatation [FMD]) and oxidative stress (electron paramagnetic resonance spectroscopy) were measured after fasting and 4 hours postprandially. At baseline, both groups exhibited similar PPL and deterioration in endothelial function. After ciprofibrate, fasting and postprandial FMD values were significantly higher (from 3.8+/-1. 8% and 1.8+/-1.3% to 4.8+/-1.1% and 3.4+/-1.1%; P<0.05). This was mirrored by a fall in fasting and postprandial triglycerides (3. 1+/-2.1 and 6.6+/-4.1 mmol/L to 1.5+/-0.8 and 2.8+/-1.3 mmol/L, P<0. 05). Fasting and postprandial HDL cholesterol was also elevated (0. 9+/-0.1 and 0.8+/-0.1 mmol/L and 1.2+/-0.2 and 1.2+/-0.1 mmol/L, P<0. 05). There were no changes in total or LDL cholesterol. Fasting and postprandial triglyceride enrichment of all lipoproteins was attenuated, with cholesterol depletion of VLDL and enrichment of HDL. There were similar postprandial increases in oxidative stress in both groups at baseline, which was significantly attenuated by ciprofibrate (0.3+/-0.6 versus 1.5+/-1.1 U, P<0.05).

CONCLUSIONS

This study demonstrates that fibrate therapy improves fasting and postprandial endothelial function in type 2 diabetes. Attenuation of PPL and the associated oxidative stress, with increased HDL cholesterol levels, may be important.

The effect of GH replacement therapy on endothelial function and oxidative stress in adult growth hormone deficiency

OBJECTIVES

Controversy persists with regard to the atherogenic risk associated with adult growth hormone deficiency (GHD). Endothelial dysfunction and enhanced oxidative stress are early features of atherogenesis. Therefore, we have studied the effect of three months of low dose GH replacement therapy (0.03IU/kg/day) on these parameters in GHD adults.

SUBJECTS AND METHODS

Eight hypopituitary GHD adults (4 male, 4 female), who were receiving conventional hormone replacement therapy, were studied before and after 3 months of GH replacement (0.03IU/kg/day). All observations obtained were compared with similar measurements made in 8 matched control subjects. All study subjects were non-smokers, normotensive and gave no personal or family history of premature vascular disease. Endothelial function was assessed using a specialised vessel wall tracking system to measure endothelium-dependent, flow-mediated, brachial artery dilatation (FMD). Measurements were repeated following glyceryl-trinitrate (GTN) (endothelium-independent dilatation). Oxidative stress was assessed by directly measuring lipid-derived free radicals in venous blood by electron paramagnetic resonance spectroscopy. Fasting lipids, insulin, plasma glucose and IGF-I were also measured at baseline and following GH replacement.

RESULTS

FMD, expressed as a percentage change from resting base-line diameter, was significantly impaired in the pre-treatment GHD patients compared with controls (3.1+/-2.1% vs 6.1+/-0.9%, P<0. 001; means+/-s.d.) indicating endothelial dysfunction. Significant increase in FMD was noted following GH therapy (3.1+/-2.1% vs 6. 5+/-1.9%, P<0.001). Free radicals (arbitrary units) were elevated in the pre-treatment GHD patients compared with controls (0.36+/-0.09 vs 0.11+/-0.12, P<0.05) and fell significantly following GH therapy (0.23+/-0.03 vs 0.36+/-0.09, P<0.05), although they remained elevated compared with controls. Fasting insulin was significantly higher (25.9+/-18.8 vs 13.9+/-6.7mu/l, P<0.05) and IGF-I concentrations lower (10.8+/-4.7 vs 20.2+/-6.3nmol/l, P<0.05) in the pre-treatment GHD subjects. After treatment there were no changes in insulin concentration, although IGF-I levels were normalised (10. 8+/-2.3 vs 23.6+/-11.4nmol/l, P<0.05).

CONCLUSIONS

Endothelial dysfunction and enhanced oxidative stress are features of adult GHD. This study suggests plausible mechanisms underlying any proatherogenic tendency in adult GHD and demonstrates improvement of these factors following GH replacement.

Endothelium-derived nitric oxide contributes to the regulation of venous tone in humans

BACKGROUND

Although nitric oxide (NO) is known to play an important part in the regulation of arterial tone, little is known about its role in veins. The aim of this study was to investigate the role of basal and stimulated NO activity in the regulation of tone of the human venous capacitance bed.

METHODS AND RESULTS

We measured venous tone using radionuclide forearm venous plethysmography in 24 healthy subjects with no cardiovascular risk factors. In 13 subjects, basal NO activity was assessed by measuring the effects on venous tone of an intra-arterial infusion of the NO synthase inhibitor N-monomethyl-L-arginine (L-NMMA). In the remaining 11 subjects, stimulated NO activity was evaluated by measuring the effects of an intra-arterial infusion of incremental doses of carbachol, followed in a subgroup by coinfusion with L-NMMA. Infusion of carbachol caused dose-dependent venodilation, with a maximal reduction in forearm venous tone of 40.1+/-12.5% (P<0.0001). Carbachol-induced venodilation was inhibited by L-NMMA (48.9+/-6.2% reversal of maximal venodilation, P<0.01). Infusion of L-NMMA alone caused venoconstriction (9.1+/-6.4% increase in venous tone, P=0.002).

CONCLUSIONS

Human forearm capacitance veins exhibit both stimulated and basal NO activity, which indicates that NO contributes not only to the regulation of venous tone but also to resting venous tone in healthy human subjects.

Prospective randomized trial of single clamp technique versus intermittent ischaemic arrest: myocardial and neurological outcome

OBJECTIVE

To explore the hypothesis that intermittent ischaemic arrest (IIA) provides better myocardial preservation but generates a larger number of cerebral microemboli (ME) and consequently a higher incidence of post-operative cerebral dysfunction compared with the single clamp technique (SCT).

METHODS

Ninety-one patients with stable angina undergoing elective CABG with no clinical evidence of aortic or cerebro-vascular or neurological disease were prospectively randomized to: IIA (n = 43) or SCT with intermittent anterograde cold blood cardioplegia (n = 48). Myocardial preservation was assessed by measuring serum CK-MB, Troponin-T (TnT) and Troponin-I (TnI) and from pre- and post-operative ECGs and left ventricular (LV) function by echocardiography. Intra-operative cerebral ME were counted by transcranial Doppler of the right middle cerebral artery. All patients completed the Luria Nebraska Neuropsychological Battery (LNNB) tests for motor, visual, reading, memory and intellectual processes the day before surgery and at 1 week and 6 months post-operatively. Serum levels of the neuro-specific protein S-100 were measured.

RESULTS

The two groups were comparable for age, sex, extent of coronary disease, previous myocardial infarction, diabetes, hypertension and number of arterial and venous grafts. The median number of ME detected per patient was 34 (range 4-208) and was similar in both groups. Protein S-100 levels remained normal and similar in both groups at all times except in one patient with SCT who had an operative stroke. LNNB scores were similarly depressed at 1 week and recovered in all cases at 6 months. There was no correlation between the number of ME and LNNB scores. Median peak TnI levels were 0.64 microg/l with IIA vs. 0.87 microg/l with SCT (P = NS) and TnT 0.8 microg/l vs. 1.08 microg/l (P < 0.03). SCT was however associated with longer mean ischaemic (67.6 +/- 16.1 vs. 34.5 +/- 16.5 min, P < 0.001) and mean bypass time (88.5 +/- 18.2 vs. 74.6 +/- 26.3 min, P < 0.004) than IIA. Four patients with SCT and none with IIA had ECG changes suggestive of MI (P = 0.04).

CONCLUSION

During elective CABG in patients with no clinical evidence of aortic or cerebro-vascular disease the incidence of peri-operative ME and post-operative neuropsychological disturbances are comparable with both techniques of myocardial preservation. Biochemical analysis suggests that IIA provides more effective myocardial preservation.

An unusual cause of recurrent pneumonia

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Postanginal septicaemia (Lemmiere's disease) complicated by haemophagocytosis

We report a case of postanginal septicaemia complicated by bronchopneumonia and haemophagocytosis in a 19-year old male, presenting with severe thrombocytopenia. We believe that this is the first reported case of thrombocytopenia due to haemophagocytosis in this unusual condition.

Hibernating myocardium caused by isolated, radiation induced left main stem coronary artery stenosis

A 45 year old man presented with a five week history of worsening exertional dyspnoea and orthopnoea. He had also noted mild, bilateral ankle swelling. The patient had been diagnosed with stage III Hodgkin's lymphoma in 1968 at the age of 21. During the same year he underwent total nodal irradiation followed by chemotherapy in 1971. He had remained entirely asymptomatic over the course of the next 24 years with no evidence of relapse. Cardiac catheterisation undertaken soon after admission revealed a tight left main stem stenosis with a left dominant system. Left ventriculogram showed severe, global hypokinesia, and raised left ventricular end diastolic pressure (22 mm Hg). Urgent coronary artery bypass graft surgery was carried out. He made an uncomplicated recovery and his condition improved sufficiently to allow discharge eight days following the procedure. His heart failure slowly resolved and repeat transthoracic echocardiogram performed six months after surgery showed an unequivocal improvement in left ventricular function. Left ventricular ejection fraction continued to improve and increased from 23% at two months to 42% at two years. He currently remains entirely asymptomatic off all medication.

Seroprevalence to Leptospira interrogans serovar hardjo in merino stud rams in South Australia

A serological survey of 2160 Merino stud rams on 36 farms detected positive reactions greater than or equal to 1/100 in 42% of animals using the microscopic agglutination test (MAT) to Leptospira interrogans serovar hardjo. Twenty flocks had seroprevalence values greater than 30% with 15 flocks having values > or = 60%. The enzyme-linked immunosorbent assays showed that 47% and 3% of rams on the 36 farms were positive for IgG and IgM antibodies, respectively. Forty-five percent of hardjo reactions were in rams that had not been exposed to cattle. Significant correlations were found between IgM reactors and creek/dam water pumped into troughs, and between MAT/IgG reactors and total flock size. No statistical relationships were detected between positive reactors and two different annual average rainfall gradients, the time of the year in which samples were obtained, or agricultural regions of South Australia. Infections with an organism of the Sejroe serogroup is widespread in Merino stud rams.

Multiple intensive care unit outbreak of Acinetobacter calcoaceticus subspecies anitratus respiratory infection and colonization associated with contaminated, reusable ventilator circuits and resuscitation bags

PURPOSE

Acinetobacter calcoaceticus subspecies anitratus (A. anitratus) can cause nosocomially and community acquired pneumonia. Source identification of the organism is often difficult. An outbreak of respiratory infection and colonization with A. anitratus affecting 93 ventilated patients in all six of a hospital's intensive care units (ICUs) over 10 months is described.

PATIENTS AND METHODS

In April 1984, the infection control staff started to review positive culture results from all patients in all ICUs. At this point, information on significant isolates was recorded by patient, site, date, genus and species, and antimicrobial susceptibility. During the month of August 1984, an increased number of A. anitratus isolates from sputum began to be detected. Information was expanded to include the date of hospital admission, ICU admission, intubation, and extubation; the dates and types of all surgical procedures; the results and dates of all prior sputum cultures; and the use of nebulized bronchodilator medications. Monthly numbers of cases were compared for four months prior to the outbreak, during the outbreak, and for seven months after the outbreak. Plasmid DNA from isolates was prepared, electrophoresed, and visualized. Isolates were designated according to the molecular weights of visualized plasmids.

RESULTS

Barrier precautions and improved staff handwashing did not diminish the frequency of new cases. When pasteurized, reusable ventilator circuits and resuscitation bags were cultured for the possibility of low-level contamination, 18 percent were positive for A. anitratus. Terminal ethylene oxide sterilization of these devices was associated with prompt control of the outbreak. Plasmid DNA analysis of isolates from patients involved in the outbreak, contaminated devices, and the hands of personnel responsible for device disinfection revealed two predominant plasmid profiles. After outbreak control, isolates with these profiles were found much less frequently in patient specimens.

CONCLUSION

Contaminated, reusable ventilator support equipment may be a leading cause for the extent of A. anitratus in the sputum of intubated patients. This problem is potentially correctable by the use of terminal etyhlene oxide sterilization of reusable ventilator circuits and resuscitation bags.

Comparison of direct electron microscopy and enzyme immunoassay for the detection of rotaviruses in calves, lambs, piglets and foals

Direct electron microscopy (EM) and enzyme-immunoassay (rotazyme) results for the detection of rotaviruses in 346 enteric specimens from calves, lambs, piglets and foals were compared. The rotazyme test was at least 3 times more sensitive than direct EM in diagnosing infection. Rotavirus antigen was demonstrated by rotazyme in 22% of 280 scour samples and in 27% of 66 samples from non-scouring animals. There was an association between diarrhoea and higher amounts of rotavirus antigen. This prevalence of rotaviruses detected in animals with diarrhoea highlights the significant involvement of other pathogens identified in the study including Eimeria, Cryptosporidia, Escherichia coli, Campylobacter, and other viruses.

Spacelab-2 Plasma Depletion Experiments for Ionospheric and Radio Astronomical Studies

The Spacelab-2 Plasma Depletion Experiments were a series of studies to examine shuttle-induced perturbations in the ionosphere and their application to ground-based radio astronomy. The space shuttle Challenger fired its orbital maneuvering subsystem engines on 30 July and 5 August 1985, releasing large amounts of exhaust molecules (water, hydrogen, and carbon dioxide) that caused the electrons and ions in Earth's upper atmosphere to chemically recombine, thereby creating so-called "ionospheric holes." Two burns conducted over New England produced ionospheric peak depletions ranging from 25 to 50 percent, affected the ionosphere over a 200-kilometer altitude range, and covered 1 degrees to 2 degrees of latitude. Optical emissions associated with the hole spanned an area of several hundred thousand square kilometers. A third burn was conducted over a low-frequency radio observatory in Hobart, Australia, to create an "artificial window" for ground-based observations at frequencies normally below the natural ionospheric cutoff (penetration) frequency. The Hobart experiment succeeded in making high-resolution observations at 1.7 megahertz through the induced ionospheric hole.