COVID-19 vaccine coverage, determinants and inequity amongst refugees and migrants in Pakistan: a cross-sectional study

OBJECTIVE

Migrants and refugees are at a disadvantage in accessing basic necessities. The objective of this study is to assess the inequity in access, needs and determinants of COVID-19 vaccination among refugees and migrant populations in Pakistan.

DESIGN

We conducted a mixed-method study comprising a cross-sectional survey and a qualitative study. In this paper, we will only report the findings from the cross-sectional survey.

SETTING

This survey was conducted in different cities of Pakistan including Quetta, Karachi and Hyderabad.

PARTICIPANTS

A total of 570 participants were surveyed including refugees and migrants, both in regular and irregular situations.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome of the study was to estimate the proportion of refugees and migrants, both in regular and irregular situations vaccinated against COVID-19 and assess the inequity. The χ2 test and Fisher's exact test were used to determine the significant differences in proportions between refugees and migrants and between regions.

RESULTS

The survey showed that only 26.9% of the refugee and migrant population were tested for COVID-19, 4.56% contracted coronavirus, and 3.85% were hospitalised due to COVID-19. About 66% of the refugees and migrants were fully vaccinated including those who received the single-dose vaccine or received all two doses, and 17.6% were partially vaccinated. Despite vaccination campaigns by the government, 14.4% of the refugee and migrant population remained unvaccinated mostly because of vaccines not being offered, distant vaccination sites, limited access, unavailability of COVID-19 vaccine or due to a difficult registration process. Vaccination rates varied across provinces, genders and migrant populations due to misconceptions, and several social, cultural and geographical barriers.

CONCLUSION

This study highlights the COVID-19 vaccine coverage, access and inequity faced by refugees and migrants during the pandemic. It suggests early prioritisation of policies inclusive of all refugees and migrants and the provision of identification documents to ease access to basic necessities.

Malaria in pregnancy: Meta-analyses of prevalence and associated complications

This review aims to assess the prevalence of malaria in pregnancy during antenatal visits and delivery, species-specific burden together with regional variation in the burden of disease. It also aims to estimate the proportions of adverse pregnancy outcomes in malaria-positive women. Based on the PRISMA guidelines, a thorough and systematic search was conducted in July 2023 across two electronic databases (including PubMed and CENTRAL). Forest plots were constructed for each outcome of interest highlighting the effect measure, confidence interval, sample size, and its associated weightage. All the statistical meta-analysis were conducted using R-Studio version 2022.07. Sensitivity analyses, publication bias assessment, and meta-regression analyses were also performed to ensure robustness of the review. According to the pooled estimates of 253 studies, the overall prevalence of malaria was 18.95% (95% CI: 16.95-21.11), during antenatal visits was 20.09% (95% CI: 17.43-23.06), and at delivery was 17.32% (95% CI: 14.47-20.61). The highest proportion of malarial infection was observed in Africa approximating 21.50% (95% CI: 18.52-24.81) during ANC and 20.41% (95% CI: 17.04-24.24) at the time of delivery. Our analysis also revealed that the odds of having anaemia were 2.40 times (95% CI: 1.87-3.06), having low birthweight were 1.99 times (95% CI: 1.60-2.48), having preterm birth were 1.65 times (95% CI: 1.29-2.10), and having stillbirths were 1.40 times (95% CI: 1.15-1.71) in pregnant women with malaria.

The Last Mile-Community Engagement and Conditional Incentives to Accelerate Polio Eradication in Pakistan: Study Protocol for a Quasi-Experimental Trial

Poliomyelitis is a condition of great concern and is endemic in only two countries of the world: Pakistan and Afghanistan. Community mobilization plays a vital role in raising awareness and can help reduce polio vaccine refusals. The objective of this study will be to decrease polio vaccine refusals and zero-dose vaccines by motivating behavior change through the provision of conditional-collective-community-based incentives (C3Is) based on a reduction in polio vaccine refusals. The project will adopt a pretest/post-test quasi-experimental design with two intervention high-risk union councils (HRUCs) and two control union councils (UCs) of peri-urban (Karachi) and rural (Bannu) settings in Pakistan. A participatory community engagement and demand creation strategy with trust-building community mobilization with C3Is, to reduce vaccine refusals and improve polio immunization coverage in two HRUCs, will be used. These UCs will be divided into clusters based on the polio program framework and community groups will be formed in each cluster. These community groups will carry out awareness activities and will be given serial targets to reduce vaccine refusals and those who qualify will be provided C3Is. The project intends to create a replicable model that the government can integrate within health systems for long-term sustainability until the goal of eradication of poliovirus is achieved. The evaluation will be carried out by an independent data collection and analysis team at baseline and endline (after 12 months of intervention). The trial is registered with linicalTrials.gov with number NCT05721274.

COVID 19 in Children: Gastrointestinal, Hepatobiliary and Pancreatic Manifestation

The most devastating pandemic of this era coronavirus disease-2019 (COVID-19) is caused by a novel virus named severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Although it is primarily a respiratory pathogen, it can also result in several extra-pulmonary manifestations includes gastrointestinal symptoms, hepatocellular injury. Angiotensin-converting enzyme-2 (ACE-2) receptor and transmembrane serine protease 2 (TMPRSS2), the entry receptor for the causative coronavirus SARS-CoV-2 is co-express in the gastrointestinal tract, hepatocyte, and cholangiocytes similar to the respiratory mucosa. The presence of these receptors facilitates the entry into the tissue and causes direct viral tissue damage, which is a proposed mechanism of injury. Diarrhoea, nausea, vomiting, abdominal discomfort are common gastrointestinal manifestations, whereas derangement of liver function tests is the most hepatic manifestation in COVID-19. In this article, we reviewed on SARS-CoV-2 disease COVID-19 regarding gastrointestinal, hepatic, and pancreatic manifestation, the mechanisms by which the virus may inflict damage, and their management perspective.

The role of β-blockers in the management of hypertension: an Asian perspective

Following publication of the National Institute of Clinical Excellence (NICE) Guidelines in 2006, the use of β-blockers as first-line therapy in hypertension has been somewhat controversial. However, a recent reappraisal of the European Society of Hypertension guidelines highlights that these agents exhibit similar BP lowering efficacy to other classes of agents, prompting a re-examination of the utility of these agents in various patient populations. The authors felt that it is important to address this controversy and provide an Asian perspective on the place of β-blockers in current clinical practice and the benefits of β-blockade in selected patient populations. In addition to their use as a potential first-line therapy in uncomplicated hypertension, β-blockers have a particular role in patients with hypertension and comorbidities such as heart failure or coronary artery disease, including those who had a myocardial infarction. One advantage which β-blockers offer is the additional protective effects in patients with prior cardiovascular events. Some of the disadvantages attributed to β-blockers appear more related to the older drugs in this class and further appraisal of the efficacy and safety profile of newer β-blockers will lend support to the current guideline recommendations in Asian countries and encourage increased appropriate use of β-blockade in current clinical practice within Asia.

Adsorption of chromium (VI) from aqueous solution by sugar beet bagasse-based activated charcoal

Chromium (VI) is known to be potentially carcinogenic and mutagenic in humans. A low-cost industrial solid bioadsorbent, bagasse-based activated charcoal (BAC), has been investigated for removal of chromium from aqueous solution. All the experiments were carried out in batch process with laboratory-prepared samples to study the effects of adsorbent dose, contact time, pH and initial concentration of Cr(VI). The removal of chromium ion was found to be highly dependent on the pH of the solution, adsorbent dose and contact time. Also the equilibrium adsorption was analyzed by the Freundlich and Langmuir isotherm models. It was found that the Freundlich isotherm model best described the sorption of chromium by sugar beet bagasse-based activated charcoal (r2 > 0.9927). Experimental data of kinetic studies were fitted to pseudo-first-order, pseudo-second-order and modified pseudo-first-order models. The results showed pseudo-second order kinetics was best fitted to the collected data (r2 > 0.9893). Optimum conditions for adsorption were determined at pH 2 and a contact time of 180 minutes (92.7% removal). These retention capacities suggest that BAC can provide a simple, effective, and cheap method for removing Cr(VI) ions from effluents and water resources.

Prevalence, awareness, treatment and control of hypertension in Malaysia: a national study of 16,440 subjects

STUDY DESIGN

A cross-sectional study was conducted in all states of Malaysia to determine the prevalence, awareness, treatment and control of hypertension. A stratified two-stage cluster sampling design with proportional allocation was used.

METHODS

Trained nurses obtained two blood pressure measurements from each subject. Hypertension was defined as mean systolic blood pressure >140 mmHg, diastolic blood pressure >90 mmHg, or a self-reported diagnosis of hypertension and taking antihypertensive medication. All data were analysed using Stata 9.2 software and took the complex survey design into account. A two-sided P-value of <0.05 was considered to be statistically significant.

RESULTS

The overall prevalence of hypertension for subjects aged 15 years was 27.8% (95% confidence interval (CI) 26.9-28.8). The prevalence of hypertension was significantly higher in males (29.6%, 95% CI 28.3-31.0) compared with females (26.0%, 95% CI 25.0-27.1). Multivariate logistic regression showed that the odds of having hypertension increased with increasing age, in males, in subjects with a family history of hypertension, with increasing body mass index, in non-smokers and with decreasing levels of education. Only 34.6% of the subjects with hypertension were aware of their hypertensive status, and 32.4 were taking antihypertensive medication. Amongst the latter group, only 26.8% had their blood pressure under control. The prevalence of hypertension amongst those aged 30 years has increased from 32.9% in 1996 to 40.5% in 2004.

CONCLUSION

In Malaysia, the prevalence of hypertension is high, but levels of awareness, treatment and control are low. There is an urgent need for a comprehensive integrated population-based intervention programme to ameliorate the growing problem of hypertension in Malaysians.

World Health Organization Quality of Life Assessment: brief version in Bahasa Malaysia

WHOQOL-100, a 100 items quality of life assessment by WHO is too lengthy to be applicable in researches where the quality of life is one of the many variables of interest. The abbreviated version with 26 items is more acceptable by subjects, especially those with illness. The generic and the abbreviated Malay version were given to subjects who were healthy and with illness. Results showed that the domain scores produced by WHOQOL-BREF correlate highly with that of WHOQOL-100. WHOQOL-BREF domain scores demonstrated good discriminant validity, construct validity, internal consistency and test-retest reliability. The study indicates that WHOQOL-BREF in its brevity offers a valid and reliable assessment of quality of life.

The effects of angiotensin II on pulse wave velocity in healthy humans

OBJECTIVES

To examine the dose response relationship between Ang II and pulse wave velocity (an index of arterial stiffness) in healthy human volunteers.

DESIGN AND METHODS

We studied 9 healthy male volunteers (mean age 24.7 +/- 0.66 years) in a double-blind, randomized, cross-over, placebo-controlled design. We measured carotid-femoral PWV using a novel device complior. Subjects received placebo, 0.5, 1 and 5 ng/kg/min Ang II as infusions over 30 minutes under standardized conditions. Heart rate, blood pressure and PWV were recorded at baseline and then every 10 minutes during the infusion and twice after the end of the infusion.

RESULTS

Systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) in mmHg increased significantly with the 5 ng/kg/min dose compared to placebo (p = 0.004, p -0.007, p = 0.003, respectively). There was no significant difference in SBP, DBP and MAP between 1 and 0.5 ng/kg/min compared to placebo. There was a significant increase in PWV with 5 ng/kg/min dose only compared to placebo (p = 0.02). However, less than 30% of the total Ang II-induced rise in PWV was explained by the Ang II-induced rise in blood pressure (R2 = 0.257).

CONCLUSIONS

Ang II increases PWV in healthy human only when given in doses that significantly increase blood pressure. Not all the increase in Ang II-induced rise in PWV can be explained due to Ang II-induced rise in BP.

Heterogeneity of the CYP2D6 gene among Malays in Malaysia

BACKGROUND

Although Malays shared an origin with Chinese, their evolution saw substantial divergences. Phenotyping studies suggested that they differed in CYP2D6 polymorphism, with higher PM prevalence but lesser right-shift for debrisoquine MRs.

OBJECTIVE

To study the genotype distribution of CYP2D6 among the Malays in Malaysia.

METHOD

We obtained DNA from 107 Malays and used PCR to determine common CYP2D6 alleles.

RESULT

CYP2D6*1 occurred at a frequency of 36.0%, duplicated gene, 0.93%, CYP2D6*4, 2.8%, CYP2D6*5, 5.1%, CYP2D6*9, 3.3%, CYP2D6*10, 49.5% and CYP2D6*17, 0.5%. The findings of CYP2D6*17 and CYP2D6*9 were novel for Asia. The frequency for CYP2D6*10 was lower than in other Asian races. The most frequent genotypes were CYP2D6*1/*10 at 39.3%. Two subjects had genotypes that predicted PM phenotype, 35% showed genotypes that predicted intermediate metabolizers and one subject had a genotype that predicted ultra-rapid metabolism.

CONCLUSION

The genetic polymorphism of CYP2D6 in Malays is different from Chinese and Far Eastern races. They may be intermediate between East Asians and Caucasians in CYP2D6 activity. Further study in relation to the evolution of races and disease prevalence may help to identify the contributions of the polymorphism in alleged susceptibility to diseases apart from delineating its contributions to ethnic differences in the pharmacology of CYP2D6 drugs.

Hypertension and stroke in Asia: prevalence, control and strategies in developing countries for prevention

Reliable statistics related to the prevalence, incidence and mortality of hypertension and stroke are not available from Asia. The data may be in national or institutional reports or journals published in the local language only. The mortality rate for stroke has been on the decline since the mid 1960s in the developed countries of Asia, such as Australia, New Zealand, and Japan, with some improvement in Singapore, Taiwan and Hong Kong, some areas of China and Malaysia about 15 years later. In India, China, Philippines, Thailand, Sri Lanka, Iran, Pakistan, Nepal, there has been a rapid increase in stroke mortality and prevalence of hypertension. The prevalence of hypertension according to new criteria (>140/90 mm Hg) varies between 15-35% in urban adult populations of Asia. In rural populations, the prevalence is two to three times lower than in urban subjects. Hypertension and stroke occur at a relatively younger age in Asians and the risk of hypertension increases at lower levels of body mass index of 23-25 kg/m2. Overweight, sedentary behaviour, alcohol, higher social class, salt intake, diabetes mellitus and smoking are risk factors for hypertension in most of the countries of Asia. In Australia, New Zealand and Japan, lower social class is a risk factor for hypertension and stroke. Population-based long-term follow-up studies are urgently needed to demonstrate the association of risk factors with hypertension in Asia. However prevention programmes should be started based on cross-sectional surveys and case studies without waiting for the cohort studies.

Ethnic differences in response to non-selective beta-blockade among racial groups in Malaysia

OBJECTIVE

To determine whether racial differences in response to blockade of beta receptors occur among racial groups in Malaysia that are the Malays, Indians and Chinese. SUBJECTS, MATERIALS AND METHOD: 35 healthy male volunteers representing the 3 main racial groups in Malaysia (12 Malays, 12 Chinese and 11 Indians) were studied in a randomized, placebo-controlled, crossover and single-blind design. Propranolol 80 mg 12-hourly was given orally for 48 hours. Six hours after the last dose subjects attended an exercise session where resting and exercise heart rate, blood pressure, plasma potassium and glucose levels, resting FEV1 and plasma propranolol concentrations were recorded.

RESULTS

No significant difference in plasma propranolol (mean +/- SEM) levels was seen between races six hours after the last dose (Malays, 59.7 +/- 8.8 ng/ml, Indians, 67.6 +/- 19.3 ng/ml, Chinese, 58.4 +/- 7.9 ng/ml). Chinese were least sensitive to the bradycardic and hypotensive effects of propranolol at rest and exercise. Indians and Malays had significant reduction of supine systolic blood pressure with propranolol but not Chinese. Comparison of percentage reductions of systolic blood pressure at supine, sitting and exercise by repeated measure analysis showed the Malays to have significantly higher change compared to the Chinese (p = 0.022). Similarly, comparison of percentage reductions of heart rate at supine, sitting and exercise by repeated measure analysis showed the Malays to have significantly higher change compared to the Chinese (p = 0.040). Average change in potassium concentrations at peak exercise and recovery showed the Indians to have significantly higher increase in potassium levels with propranolol compared to the Malays (p = 0.038). However, no significant interethnic difference was seen in the reduction of glucose levels at rest, peak exercise or recovery. Also, no significant interethnic difference was seen in reduction of FEV1 values.

CONCLUSION

We, therefore, conclude that ethnic differences in response to blockade of beta-receptors exist among racial groups in Malaysia. These differences were seen at similar plasma drug levels between races suggesting ethnic differences in drug sensitivity, rather than differences in drug disposition.

First-dose response to angiotensin-converting enzyme inhibition in congestive cardiac failure: a Malaysian experience

Despite their proven value in reducing morbidity and mortality in different grades of heart failure, angiotensin converting enzyme (ACE) inhibitors continue to be underused. One reason for this is clinicians' apprehension of first-dose hypotension. We conducted a double-blind, randomised, placebo-controlled parallel group study to investigate the effect of various ACE inhibitors on first-dose hypotension. Eighty unselected patients were randomised into five treatment groups: placebo, captopril 6.25 mg, enalapril 2.5 mg, perindopril 2 mg and lisinopril 2.5 mg. Blood pressure was measured at baseline, half hourly for two hours and hourly for three hours after drug treatment. The maximum drops in mean arterial pressure (in mmHg +/- SD) were placebo 5.89 +/- 2.65, perindopril 5.29 +/- 2.49, enalapril 13.28 +/- 3.31, lisinopril 15.04 +/- 5.74 and captopril 16.76 +/- 5.74 (all p < 0.05 vs placebo except for perindopril). Perindopril, unlike the other ACE inhibitors studied, did not produce first-dose hypotension following its initiation in patients with congestive heart failure.

Field evaluation of cyfluthrin and malathion 96 TG ULV spraying at high-rise flats on dengue vectors in Malaysia

Cyfluthrin (Solfac ULO15) and malathion 96 TG were evaluated against sentinel sugar-fed adults and 4th-instar larvae of Aedes aegypti at high-rise flats in Malaysia by ULV spraying. The impact of both insecticides on field populations of Aedes spp. (Ae. aegypti and Ae. albopictus) larvae were monitored weekly using containers. Both cyfluthrin and malathion 96 TG showed adulticidal effects but cyfluthrin showed more significant larvicidal effect than malathion 96 TG (P < 0.05).

Fatal Campylobacter jejuni infection in a patient splenectomised for thalassaemia

A 35 year old man with a fatal Campylobacter jejuni infection is described. He had HbE/beta zero thalassaemia and had undergone splenectomy nine months previously for hypersplenism; he also had chronic hepatitis C infection. He presented with high grade fever but no gastrointestinal symptoms and rapidly progressed to septicaemic shock and hepatic encephalopathy despite treatment with penicillin, gentamicin, and, later, chloramphenicol and ceftazidime. Only one case of Campylobacter jejuni septicaemia occurring post-splenectomy has been reported previously, also in an iron overloaded thalassaemia patient. Unusual Gram negative bacilli must be covered by the chosen antibiotic regimen when splenectomised thalassaemic patients present with high grade fever.

Blood pressure regulation by the kallikrein-kinin system

1. The kallikrein-kinin system has a significant role in regulating arterial blood pressure. 2. Reduced formation of the kinin compontents may cause hypertensive diseases. This is because of the fact that this system is responsible for vasodilatation, reduction in total peripheral resistance, natriuresis, diuresis, increasing renal blood flow and releasing various vasodilator agents. 3. Reduced kinin-kallikrein generation in hypertensive subjects may also be associated with genetic and environmental defects. 4. The kallikrein-kinin system when administered to hypertensive patients can lower their raised blood pressure to normotensive levels. 5. The mode of action of angiotensin-converting enzyme inhibitors principally may be dependent on the kinin system protection.

Effects of lisinopril on congestive heart failure in normotensive patients with diastolic dysfunction but intact systolic function

This study examined the effects of lisinopril on diastolic function in 12 normotensive patients (mean age 72 years) with symptomatic congestive heart failure, intact left ventricular systolic function and abnormal diastolic function secondary to ischaemic heart disease in a placebo-controlled double blind crossover study, with each treatment dosed orally for 5 continuous weeks. Compared to placebo, lisinopril significantly decreased blood pressure, increased plasma renin activity without altering heart rate or plasma norepinephrine. There was no statistically significant improvement with lisinopril in radionuclide derived peak filling rate and time to peak filling rate, in Doppler echocardiographic measurements of the ratio of peak flow velocity in early diastole to the peak flow velocity of atrial contraction (E:A ratio) and in visual analogue scales of symptoms. Thus, although angiotension converting enzyme inhibitors may have an established role in the treatment of heart failure secondary to left ventricular systolic dysfunction, its use in patients with isolated diastolic dysfunction remains unclear.

The effect of enalapril on tyramine induced changes in renal function in man

Increasing animal evidence support an important facilitatory interaction between angiotensin II and norepinephrine within the kidney. This angiotensin II/norepinephrine interaction was investigated in man by examining the effect of enalapril pretreatment (5 mg for 5 days) on the renal response to a low non-pressor dose of intravenous tyramine 4 micrograms/kg/min for 120 min in 8 healthy subjects undergoing water diuresis. Tyramine is an indirect sympathomimetic agent which causes neuronal release of norepinephrine. Enalapril and tyramine, alone and in combination, had no effect on glomerular filtration, effective renal plasma flow or sodium excretion. Tyramine caused a significant increase in urinary flow rate (p < 0.05) but this was not influenced by enalapril pretreatment. The lack of effect of enalapril on the renal response to tyramine contrasts with a previous study which examined the effect of enalapril on the renal response to circulating norepinephrine. This may suggest that enalapril affect renal function only when there is renal vasoconstriction (as with norepinephrine) and not when renal blood flow is unchanged (as with tyramine).

How good are doctors as drug prescribers?

The training of doctors in therapeutics has created interesting discussions internationally. A survey of senior hospital pharmacists currently practising throughout West Malaysia was embarked on during a recent postgraduate seminar. About sixty per cent said prescribing errors were common amongst doctors. Sixteen per cent of the prescribing errors were potentially serious. Most of the time errors were due to carelessness, lack of knowledge on drug action or a combination of both. Nearly 35% of prescribing errors were not acknowledged by doctors. Most doctors did not give reasons for not acknowledging pharmacists' intervention. About half (46.5%) of the respondents thought that doctors were not adequately trained in the use of drugs.

The differential effects of circulating norepinephrine and neuronally released norepinephrine on sodium excretion in humans

The renal effects of incremental infusions of norepinephrine (placebo, 0.025 mu/kg/min), 0.075 micrograms/kg/min, phenylephrine (placebo, 0.5 micrograms/kg/min, 2.5 micrograms/kg/min), and tyramine (placebo, 2 micrograms/kg/min, 15 micrograms/kg/min) were examined in three respective groups (n = 9, 8, and 8) of normotensive male subjects undergoing water diuresis. Tyramine is an indirect sympathetic agent that causes neuronal release of endogenous norepinephrine. Increases in mean arterial pressure during each high-dose infusion were comparable in all three groups. Both norepinephrine and phenylephrine caused a decrease in urinary sodium excretion and effective renal plasma flow, with no changes in glomerular filtration rate. Proximal tubular sodium reabsorption, as assessed by both lithium clearance and solute-free water clearance methods, was increased by pressor doses of norepinephrine and phenylephrine. In contrast, a similar pressor dose of tyramine was associated with a pressure natriuresis, an increase in effective renal plasma flow, and a decrease in proximal tubular sodium reabsorption. Our data indicate that, in normotensive humans, circulating catecholamines (norepinephrine and phenylephrine) have opposite effects on renal sodium handling from neuronally released norepinephrine (tyramine).

Effect of noradrenaline on renal sodium and water handling in euhydrated and overhydrated man

1. The renal effects of incremental doses of intravenously infused noradrenaline were evaluated in normal subjects during two different water loads, 5 ml/kg (n = 6) and 20 ml/kg (n = 9), producing conditions of euhydration and overhydration, respectively. 2. Noradrenaline infusion rates ranged from 0.015 to 0.075 microgram min-1 kg-1. In the euhydrated subjects, noradrenaline caused a dose-dependent fall in urinary sodium excretion and an increase in urinary flow rate. During overhydration similar doses of noradrenaline caused a fall in urinary sodium excretion but a decrease in urinary flow rate. 3. Although there was no detectable change in glomerular filtration rate, a dose-dependent fall in effective renal plasma flow was observed in both hydration states during noradrenaline infusion. 4. Noradrenaline infusion was associated with a dose-dependent increase in proximal tubular sodium reabsorption as assessed by the lithium clearance method. Fractional reabsorption of sodium by the distal nephron was, however, unchanged by noradrenaline in both hydration states. 5. Plasma vasopressin concentration was unchanged by noradrenaline in euhydrated subjects. The renin-angiotensin-aldosterone axis was stimulated by noradrenaline in both euhydrated and overhydrated subjects. 6. Thus we conclude that plasma circulating noradrenaline has a dose-dependent antinatriuretic effect in man. The antinatriuretic effect of noradrenaline is mediated mainly at the proximal tubule in man. We have also shown that during overhydration, noradrenaline decreased urinary flow rate. In contrast, in euhydrated subjects, noradrenaline increased urinary flow rate with no accompanying changes in plasma vasopressin concentration, which suggests a direct effect of noradrenaline on the renal tubular permeability to water.

Renal effects of low dose prazosin in patients with congestive heart failure

Activation of the sympathetic nervous system may contribute to the renal vasoconstriction and sodium retention seen in congestive heart failure. Previous studies in congestive heart failure patients employing large doses of prazosin that lowered systemic blood pressure have been generally disappointing. The renal haemodynamic and segmental tubular effects of low non-depressor doses of prazosin (0.25 mg and 0.50 mg) were examined in eight female patients with mild to moderate congestive heart failure. Segmental tubular function was assessed by the lithium clearance method. Compared to placebo, prazosin caused a significant increase in urinary sodium excretion (from 56 +/- 7 to 92 +/- 7 mumol.min-1, P < 0.01), paralleled by significant increases in fractional excretion of sodium and lithium. Glomerular filtration rate and effective renal plasma flow were not altered by prazosin. Prazosin pre-treatment did not alter any of the renal responses to frusemide treatment (mean dose 85 +/- 14 mg). This study demonstrates that low non-depressor doses of prazosin have a clear natriuretic effect in congestive heart failure patients, which is predominantly established by interference with tubular reabsorption.

Circulating angiotensin II and renal sodium handling in man: a dose-response study

1. Animal studies have shown that angiotensin II has a biphasic effect on urinary sodium excretion. To examine whether this is also true in man, we studied seven salt-replete male subjects in a single-blind placebo-controlled manner. 2. While undergoing maximum diuresis, subjects were infused with 0, 1, 2, 5 or 10 ng of angiotensin II min-1 kg-1 over 80 min. Subjects were studied while seated, and stood every 20 min for urine collection. 3. Angiotensin II produced a dose-dependent antidiuretic effect. The urine flow rate, in ml/min expressed as the change from baseline with increasing dose of angiotensin, was: +3.4 +/- 1.77, -1.26 +/- 0.49 (P < 0.05), -2.75 +/- 1.23 (P < 0.05), -4.21 +/- 0.82 (P < 0.05) and -6.51 +/- 1.07 (P < 0.01). 4. In contrast, the effect of angiotensin II on sodium excretion showed a flat dose-response curve beyond 5 ng min-1 kg-1. The urinary sodium excretion, in mumol/min expressed as the change from baseline with increasing dose of angiotensin, was: 9.5 +/- 21.2, -18.9 +/- 29.6, -37.0 +/- 11.6 (P < 0.05), -67.7 +/- 19.6 (P < 0.01) and -63.8 +/- 14.3 (P < 0.01). 5. The fractional distal reabsorption of sodium, determined by using the lithium clearance technique, showed a rise with all doses of angiotensin II used and reached statistical significance with the top two doses. 6. Unlike antidiuresis, antinatriuresis after graded doses of angiotensin II in human subjects showed a flat dose-response curve beyond 5 ng min-1 kg-1. Pressor doses of angiotensin II also have a significant effect on the distal tubule in promoting sodium reabsorption.

Enalapril blunts the antinatriuretic effect of circulating noradrenaline in man

OBJECTIVE

The present study examines the effect of angiotensin converting enzyme inhibition on the renal haemodynamic and sodium excretory responses to noradrenaline in man.

DESIGN

We studied the effects of intravenous noradrenaline (0.075 micrograms/kg per min) and enalapril pretreatment (5 mg/day for 5 days), alone and in combination, on urinary sodium excretion, effective renal plasma flow, glomerular filtration rate and segmental tubular function in nine normal subjects.

METHODS

The subjects were studied during maximal water diuresis. The clearance of inulin and of para-aminohippurate were used to estimate the glomerular filtration rate and effective renal plasma flow, respectively. Segmental tubule handling of sodium was assessed by the lithium clearance method.

RESULTS

Noradrenaline alone decreased urinary sodium excretion (P < 0.01) and the effective renal plasma flow (P < 0.01) without altering the glomerular filtration rate. Enalapril pretreatment significantly attenuated this fall in sodium excretion (P < 0.05) and effective renal plasma flow (P < 0.05), and had a similar attenuating effect on the noradrenaline-induced decrease in the fractional excretion of lithium. The pressor response to noradrenaline infusion was not, however, influenced by the enalapril pretreatment.

CONCLUSIONS

Enalapril blunts the renal vasoconstrictive effect and the antinatriuretic effect of noradrenaline in man. Our results indicate that there is an important interaction between the sympathetic nervous system and the renin-angiotensin system in the kidneys in man.

Sex differences in hypokalaemic and electrocardiographic effects of inhaled terbutaline

BACKGROUND

Gender differences in the chronotropic effects of infused isoprenaline have previously been described. The aim of the present study was to investigate possible gender differences in hypokalaemic, chronotropic, and electrocardiographic effects of inhaled terbutaline.

METHODS

Twenty healthy volunteers (10 female) were recruited (mean age 24 years for women (F) and 22 years for men (M). Subjects were given either inhaled terbutaline 5 mg or placebo in single blind, randomised crossover fashion and the following measurements were made for four hours after inhalation: (a) serum potassium concentration; (b) heart rate; (c) electrocardiographic sequelae (T wave amplitude, Q-Tc interval). The effects of terbutaline on serum potassium was chosen as the primary end point for detecting a 0.3 mmol/l difference between sexes, with a beta error of 0.2 and alpha set at 0.05.

RESULTS

The hypokalaemic effects of terbutaline were significantly greater in women, the potassium results (means and 95% CI) being as follows: lowest potassium concentration--F 3.12 (2.96-3.28) mmol/l v M 3.65 (3.49-3.81) mmol/l; percentage change from baseline at one hour--F 15.4% (11.5-19.3%) v M 8.5% (4.6-12.3%); average potassium concentration during the four hours--F 3.39 (3.33-3.46) mmol/l v M 3.78 (3.72-3.85) mmol/l. There was no significant regression between body weight and the potassium response to terbutaline. There were also significant sex differences for T wave, Q-Tc, and heart rate response. The percentage fall in T wave amplitude 30 minutes after terbutaline was: F 44.6% (32.1-57.0%) v M 22.4% (9.9-34.8%).

CONCLUSIONS

Women are more sensitive to the hypokalaemic, chronotropic, and electrocardiographic sequelae of inhaled terbutaline.

Prazosin blunts the antinatriuretic effect of circulating angiotensin II in man

OBJECTIVE

The present study examines the role of alpha 1-adrenoceptors in determining the renal haemodynamic and sodium excretory responses to a physiological dose of angiotensin II in man.

DESIGN

The effects of a low-dose infusion of angiotensin II (1 ng/kg per min) and a non-depressor dose of prazosin (0.25 mg), alone and in combination, on urinary sodium excretion (UNaV), effective renal plasma flow (ERPF), glomerular filtration rate (GFR) and segmental tubular function were studied in eight normal male subjects.

METHODS

Subjects were studied undergoing maximal water diuresis. Clearances of inulin and para-aminohippurate were employed to estimate GFR and ERPF, respectively. Segmental tubular handling was assessed by both lithium clearance (CLi) and solute-free water methods.

RESULTS

Angiotensin II decreased UNaV without altering ERPF and GFR. Angiotensin II caused a significant fall in fractional CLi, which may indicate a proximal tubular effect of angiotensin II. Angiotensin II alone also increased fractional reabsorption of sodium delivered to the distal nephron, as evaluated by both the CLi method and by estimation of solute-free water clearance. When angiotensin II was given in combination with prazosin, which on its own had no apparent effects on any renal parameters, the antinatriuretic and tubular effects of angiotensin II were significantly blunted.

CONCLUSIONS

These findings suggest that low doses of circulating angiotensin II are able to modulate UNaV by increasing sodium reabsorption in the proximal and, to some extent, the distal nephron segment in man. The study also showed that a non-depressor dose of prazosin blunted the renal effects of angiotensin II, thereby providing tentative evidence of a renal interaction between alpha-adrenoceptors and angiotensin II in man.

Effect of angiotensin-converting enzyme inhibition on plasma brain natriuretic peptide levels in patients with heart failure

1. The aim of this study was to examine the effect of captopril, an angiotensin-converting enzyme inhibitor, on plasma levels of human brain natriuretic peptide-like immunoreactivity (hBNP-li) in patients with congestive heart failure. 2. Six male patients (aged 52-74 years) with mild to moderate congestive heart failure were studied on two occasions in the semi-recumbent position. After a 30 min rest, patients were randomized to receive oral tablets of either captopril (6.25 mg followed by 25 mg 2 h later) or placebo in a single-blind manner. Plasma hBNP-li, atrial natriuretic peptide-like immunoreactivity (ANP-li) and angiotensin II-like immunoreactivity (ANG II-li) levels and blood pressure were measured. 3. Baseline plasma hBNP-li and ANP-li levels in these patients with mild to moderate congestive heart failure were 13.5 +/- 3.2 pmol/l and 50.9 +/- 11.8 pmol/l, respectively. In 11 healthy male subjects aged 20-23 years, the peripheral plasma hBNP-li and ANP-li levels were 1.3 +/- 0.2 pmol/l and 5.6 +/- 1.7 pmol/l, respectively. In all patients, captopril decreased the plasma ANG II-li level (from 24.3 +/- 8.1 to 6.6 +/- 3.2 pmol/l, P < 0.05) and mean arterial blood pressure (from 92 +/- 3 to 80 +/- 3 mmHg, P < 0.05). Compared with placebo, captopril treatment was associated with significant reductions in plasma hBNP-li (from 14.3 +/- 3.0 to 12.8 +/- 2.1 pmol/l, P < 0.05) and in plasma ANP-li (from 53.9 +/- 1.11 to 36.8 +/- 7.6 pmol/l, P < 0.05) levels.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of enalapril and spironolactone on terbutaline-induced hypokalemia

OBJECTIVE

To investigate whether enalapril (E) 10 mg and spironolactone (S) 100 mg attenuate the hypokalemic effect of inhaled terbutaline (T).

DESIGN

Randomized single-blind crossover. Subjects received the following treatment combinations: (a) placebo (P), (b) T alone, (c) T + E, or (d) T + S.

SETTING

University Department of Clinical Pharmacology.

PARTICIPANTS

Twenty healthy volunteers (ten male, ten female) of mean age 22.8 +/- 3.1 years.

MAIN OUTCOME MEASURES

Serum potassium, magnesium, ECG changes (R-R interval, T wave, and QTc interval) for 4 h after terbutaline inhalation.

MAIN RESULTS

Baseline serum potassium levels were higher following prior treatment with E and S; P, 3.78 mmol/L (3.67 to 3.88); T + E, 3.93 mmol-1 (3.82 to 4.03); and T + S, 4.03 mmol/L (3.93 to 4.14) (p less than 0.05). Mean potassium concentrations over 4 h were also higher following prior treatment with E and S; T, 3.58 mmol/L (3.54 to 3.63); T + E, 3.68 mmol/L (3.64 to 3.72) (p less than 0.05); and T + S, 3.73 mmol/L (3.68 to 3.78) (p less than 0.01).

CONCLUSIONS

Enalapril and spironolactone protect against the fall in serum potassium over 4 h by elevating baseline potassium concentration. These potassium-sparing drugs, however, should not be used to prevent the hypokalemic and electrocardiographic sequelae of inhaled beta 2-agonists.

Atrial natriuretic factor inhibits metoclopramide stimulated aldosterone release in man

1. Atrial natriuretic factor (ANF) has an inhibitory effect on angiotensin II and ACTH stimulated aldosterone secretion in man. The selectivity of this aldosterone suppressing effect of ANF is unclear in man. The present study investigated the effect of ANF on the increase in plasma aldosterone due to metoclopramide in man. 2. Eight normal male volunteers were studied on three occasions. Metoclopramide (10 mg slow i.v.) was given on all study days and each volunteer was randomised to receive 45 min infusion of either 5% D-glucose (placebo) or ANF (99-126) 3 or 15 pmol kg-1 min-1. 3. Metoclopramide increased plasma aldosterone to approximately 170% of baseline levels (P less than 0.01). Concomitant infusion of ANF 3 pmol kg-1 min-1 and 15 pmol kg-1 min-1 significantly attenuated this rise in plasma aldosterone to approximately 130% (P less than 0.05) and 110% (P less than 0.01) of baseline values respectively. 4. It is suggested, in the light of previous findings, that the inhibitory effect of ANF represents a non-selective action of ANF on aldosterone release.

Lithium does not alter the renal response to a pressor dose of tyramine in man

Renal clearance of lithium has been used as a marker of proximal tubular function in man. Recently, lithium pre-treatment has been shown to interfere with the natriuretic actions of some natriuretic agents in man. We have therefore investigated the effects of oral lithium carbonate (500 mg) on the natriuretic response to a pressor dose of tyramine (15 micrograms kg-1 min-1) in six normal volunteers. Lithium had no effect on baseline sodium excretion, nor did it affect the tyramine-induced increase in blood pressure and subsequent natriuresis. These results show that oral lithium carbonate (500 mg) does not appear to interfere with the pressure natriuretic response to tyramine in man.

Presynaptic alpha receptors in relation to the cardiovascular effect of yohimbine in the anesthetized cat

Yohimbine in doses of 0.1 and 0.5 mg/kg induced a prolonged graded elevation in mean arterial blood pressure (MABP) and pulse pressure (PP) in chloralose-anesthetized cats. However, an increased dose of yohimbine of 1.0 mg/kg resulted in a fall in blood pressure which lasted 30 min. All 3 dose levels produced an increase in heart rate (HR) but the response was maximal at 0.5 mg/kg. Therefore, further cardiovascular effects were investigated at this dose level. Propranolol pretreatment abolished yohimbine-induced tachycardia, but had little effect on the pressor response. Guanethidine pretreatment antagonized the tachycardia and converted the pressor response to yohimbine into a depressor one. Both tachycardia and rise in MABP obtained in response to yohimbine were abolished by hexamethonium pretreatment. In C-1 cord sectioned cats, only a transient tachycardia and rise in blood pressure were obtained. Yohimbine also augmented positive chronotropic response to the right cardioaccelerator nerve stimulation. Furthermore, yohimbine completely antagonized the inhibitory effect of clonidine on the positive chronotropic response induced by cardioaccelerator nerve stimulation. Therefore, a major fraction of the observed cardiovascular effects of yohimbine seems to be mediated indirectly via the released catecholamines secondary to the blockade by the drug, of presynaptic alpha adrenoceptors at sympathetic nerve terminals.

REVERSIBLE COMPRESSION OF DEHYDRATED PEAS

Freeze-dried peas were compressed 4-fold and subsequently rehydrated to virtually their precompression characteristics. Histological studies showed that conventional processes of freezing and freeze-drying result in considerable disruption of cell walls. Contrary to what was anticipated, compression forces of 1000-2000 psi resulted in only a slight increase in breakage of cell walls. However, no correlation was established between cell disruption or texture and increasing compression force. A study of the effects of plasticizing moisture and compression force enabled optimization of processing conditions resulting in compressed peas which can be reconstituted to virtually their precompression characteristics.