Long-term outcomes with haloperidol versus placebo in acutely admitted adult ICU patients with delirium

PURPOSE

We assessed long-term outcomes in acutely admitted adult patients with delirium treated in intensive care unit (ICU) with haloperidol versus placebo.

METHODS

We conducted pre-planned analyses of 1-year outcomes in the Agents Intervening against Delirium in the ICU (AID-ICU) trial, including mortality and health-related quality of life (HRQoL) assessed by Euroqol (EQ) 5-dimension 5-level questionnaire (EQ-5D-5L) index values and EQ visual analogue scale (EQ VAS) (deceased patients were assigned the numeric value zero). Outcomes were analysed using logistic and linear regressions with bootstrapping and G-computation, all with adjustment for the stratification variables (site and delirium motor subtype) and multiple imputations for missing HRQoL values.

RESULTS

At 1-year follow-up, we obtained vital status for 96.2% and HRQoL data for 83.3% of the 1000 randomised patients. One-year mortality was 224/501 (44.7%) in the haloperidol group versus 251/486 (51.6%) in the placebo group, with an adjusted absolute risk difference of - 6.4%-points (95% confidence interval [CI] - 12.8%-points to - 0.2%-points; P = 0.045). These results were largely consistent across the secondary analyses. For HRQoL, the adjusted mean differences were 0.04 (95% CI - 0.03 to 0.11; P = 0.091) for EQ-5D-5L-5L index values, and 3.3 (95% CI - 9.3 to 17.5; P = 0.142) for EQ VAS.

CONCLUSIONS

In acutely admitted adult ICU patients with delirium, haloperidol treatment reduced mortality at 1-year follow-up, but did not statistically significantly improve HRQoL.

Thrombocytopenia and platelet transfusions in ICU patients: an international inception cohort study (PLOT-ICU)

PURPOSE

Thrombocytopenia (platelet count < 150 × 109/L) is common in intensive care unit (ICU) patients and is likely associated with worse outcomes. In this study we present international contemporary data on thrombocytopenia in ICU patients.

METHODS

We conducted a prospective cohort study in adult ICU patients in 52 ICUs across 10 countries. We assessed frequencies of thrombocytopenia, use of platelet transfusions and clinical outcomes including mortality. We evaluated pre-selected potential risk factors for the development of thrombocytopenia during ICU stay and associations between thrombocytopenia at ICU admission and 90-day mortality using pre-specified logistic regression analyses.

RESULTS

We analysed 1166 ICU patients; the median age was 63 years and 39.5% were female. Overall, 43.2% (95% confidence interval (CI) 40.4-46.1) had thrombocytopenia; 23.4% (20-26) had thrombocytopenia at ICU admission, and 19.8% (17.6-22.2) developed thrombocytopenia during their ICU stay. Absence of acquired immune deficiency syndrome (AIDS), non-cancer-related immune deficiency, liver failure, male sex, septic shock, and bleeding at ICU admission were associated with the development of thrombocytopenia during ICU stay. Among patients with thrombocytopenia, 22.6% received platelet transfusion(s), and 64.3% of in-ICU transfusions were prophylactic. Patients with thrombocytopenia had higher occurrences of bleeding and death, fewer days alive without the use of life-support, and fewer days alive and out of hospital. Thrombocytopenia at ICU admission was associated with 90-day mortality (adjusted odds ratio 1.7; 95% CI 1.19-2.42).

CONCLUSION

Thrombocytopenia occurred in 43% of critically ill patients and was associated with worse outcomes including increased mortality. Platelet transfusions were given to 23% of patients with thrombocytopenia and most were prophylactic.

Loop diuretics in adult intensive care patients with fluid overload: a systematic review of randomised clinical trials with meta-analysis and trial sequential analysis

BACKGROUND

Fluid overload is a risk factor for organ dysfunction and death in intensive care unit (ICU) patients, but no guidelines exist for its management. We systematically reviewed benefits and harms of a single loop diuretic, the predominant treatment used for fluid overload in these patients.

METHODS

We conducted a systematic review with meta-analysis and Trial Sequential Analysis (TSA) of a single loop diuretic vs. other interventions reported in randomised clinical trials, adhering to our published protocol, the Cochrane Handbook, and PRISMA statement. We assessed the risks of bias with the ROB2-tool and certainty of evidence with GRADE. This study was registered in the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42020184799).

RESULTS

We included 10 trials (804 participants), all at overall high risk of bias. For loop diuretics vs. placebo/no intervention, we found no difference in all-cause mortality (relative risk (RR) 0.72, 95% confidence interval (CI) 0.49-1.06; 4 trials; 359 participants; I2 = 0%; TSA-adjusted CI 0.15-3.48; very low certainty of evidence). Fewer serious adverse events were registered in the group treated with loop diuretics (RR 0.81, 95% CI 0.66-0.99; 6 trials; 476 participants; I2 = 0%; very low certainty of evidence), though contested by TSA (TSA-adjusted CI 0.55-1.20).

CONCLUSIONS

The evidence is very uncertain about the effect of loop diuretics on mortality and serious adverse events in adult ICU patients with fluid overload. Loop diuretics may reduce the occurrence of these outcomes, but large randomised placebo-controlled trials at low risk of bias are needed.

Endotracheal lactate reflects lower respiratory tract infections and inflammation in intubated patients

The aim of this study was to assess L-lactate and D-lactate in endotracheal aspirate from intubated patients hospitalized at the intensive care unit and explore their use as diagnostic biomarkers for inflammation and lower respiratory tract infections (LRTI). Tracheal aspirates from 91 intubated patients were obtained at time of intubation and sent for microbiological analyses, neutrophil count, and colorimetric lactate measurements. We compared the concentration of lactate from patients with microbiological verified LRTI or clinical/radiological suspicion of LRTI with a control group. In addition, associations between inflammation and the lactate isomers were examined by correlating L-lactate and D-lactate with sputum neutrophils and clinical assessments. The concentration of L-lactate was increased in aspirates with verified or suspected LRTI (p < 0.001) relative to the control group at Day 0. Connections between L-lactate and inflammation were indicated by the correlation between neutrophils and L-lactate (p < 0.001). We found no increase in sputum D-lactate from patients with verified or suspected LRTI relative to the control group and D-lactate was not correlated with neutrophils. L-lactate was found to be a potential indicator for inflammation and LRTI at the time of intubation. An association was found between neutrophil count and L-lactate. Interestingly, the increase of L-lactate in the control group after intubation may suggest that intubation challenges the host response by inflicting tissue damage or by introducing infectious microbes.

Low-dose hydrocortisone in patients with COVID-19 and severe hypoxia: The COVID STEROID randomised, placebo-controlled trial

Background

In the early phase of the pandemic, some guidelines recommended the use of corticosteroids for critically ill patients with COVID‐19, whereas others recommended against the use despite lack of firm evidence of either benefit or harm. In the COVID STEROID trial, we aimed to assess the effects of low‐dose hydrocortisone on patient‐centred outcomes in adults with COVID‐19 and severe hypoxia.

Methods

In this multicentre, parallel‐group, placebo‐controlled, blinded, centrally randomised, stratified clinical trial, we randomly assigned adults with confirmed COVID‐19 and severe hypoxia (use of mechanical ventilation or supplementary oxygen with a flow of at least 10 L/min) to either hydrocortisone (200 mg/d) vs a matching placebo for 7 days or until hospital discharge. The primary outcome was the number of days alive without life support at day 28 after randomisation.

Results

The trial was terminated early when 30 out of 1000 participants had been enrolled because of external evidence indicating benefit from corticosteroids in severe COVID‐19. At day 28, the median number of days alive without life support in the hydrocortisone vs placebo group were 7 vs 10 (adjusted mean difference: −1.1 days, 95% CI −9.5 to 7.3, P = .79); mortality was 6/16 vs 2/14; and the number of serious adverse reactions 1/16 vs 0/14.

Conclusions

In this trial of adults with COVID‐19 and severe hypoxia, we were unable to provide precise estimates of the benefits and harms of hydrocortisone as compared with placebo as only 3% of the planned sample size were enrolled.

Trial registration: ClinicalTrials.gov: NCT04348305. European Union Drug Regulation Authorities Clinical Trials (EudraCT) Database: 2020‐001395‐15.

The influence of active and passive air humidification on exhaled breath condensate volume

Exhaled breath condensate (EBC) is safely collected in mechanically ventilated (MV) patients, but there are no guidelines regarding humidification of inhaled air during EBC collection. We investigated the influence of active and passive air humidification on EBC volumes obtained from MV patients. We collected 29 EBC samples from 21 critically ill MV patients with one condition of active humidification and four different conditions of non-humidification; 19 samples from 19 surgical MV patients with passive humidification and two samples from artificial lungs MV with active humidification. The main outcome was the obtained EBC volume per 100 L exhaled air. When collected with different conditions of non-humidification, mean [95% CI] EBC volumes did not differ significantly (1.35 [1.23; 1.46] versus 1.16 [1.05; 1.28] versus 1.27 [1.13; 1.41] versus 1.17 [1.00; 1.33] mL/100 L, p=0.114). EBC volumes were higher with active humidification than with non-humidification (2.05 [1.91; 2.19] versus 1.25 [1.17; 1.32] mL/100 L, p<0.001). The volume difference between these corresponded to the EBC volume obtained from artificial lungs (0.81 [0.62; 0.99] versus 0.89 mL/100 L, p=0.287). EBC volumes were lower for surgical MV patients with passive humidification compared to critically ill MV patients with non-humidification (0.55 [0.47; 0.63] versus 1.25 [1.17; 1.32] mL/100 L, p<0.001). While active humidification increases EBC volumes, passive humidification decreases EBC volumes and possibly influences EBC composition by other mechanisms. We propose that EBC should be collected from MV patients without air humidification to improve reproducibility and comparability across studies, and that humidification conditions should always be reported.

Intracranial entrapment of a haemodialysis catheter guidewire

A 49-year-old man with chronic obstructive pulmonary disease was hospitalised due to pneumonia and pulmonary embolisms. After subsequently developing septic shock and acute renal failure, he required dialysis. A haemodialysis catheter was planned inserted into the right subclavian vein, the guidewire was introduced using the Seldinger technique. When the guidewire's 20 cm marker entered the introducer needle, it suddenly encountered resistance. Repeated attempts to remove the guidewire failed. Vital signs and haemodynamic parameters remained unchanged throughout the procedure. CT angiography revealed cranial displacement of the wire into the right internal jugular vein, with the tip of the wire just cranial to the jugular foramen in the right sigmoid sinus. Interventional radiological removal attempts were unsuccessful. Thoracic and neurosurgical interventions were considered impossible and the guidewire was left in place. Due to the pulmonary embolism and the foreign object in the patient, life-long anticoagulation was considered, with close monitoring of compliance with the patient's comorbidity and medication.

Characteristics and early outcomes of patients hospitalised for COVID-19 in North Zealand, Denmark

INTRODUCTION

Coronavirus disease 2019 (COVID-19) is an ongoing pandemic associated with significant morbidity and mortality worldwide. Limited data are available describing the clinical presentation and outcomes of hospitalised COVID-19 patients in Europe.

METHODS

This was a single-centre retrospective chart review of all patients with COVID-19 admitted to the North Zealand Hospital in Denmark between 1 March and 4 May 2020. Main outcomes include major therapeutic interventions during hospitalisation, such as invasive mechanical ventilation, as well as death.

RESULTS

A total of 115 patients were included, including four infants. The median age of adults was 68 years and 40% were female. At admission, 55 (50%) patients had a fever, 29 (26%) had a respiratory rate exceeding 24 breaths/minute, and 78 (70%) received supplemental oxygen. The prevalence of co-infection was 13%. Twenty patients (18%) (median age: 64 years; 15% female) were treated in the intensive care unit. Twelve (10.4%) received invasive mechanical ventilation and three (2.6%) renal replacement therapy. Nine patients (8%) developed pulmonary embolism. Sixteen patients (14%) died. Among patients requiring mechanical ventilation (n = 12), seven (6.1%) were discharged alive, four (3.4%) died and one (0.9%) was still hospitalised.

CONCLUSION

In this cohort of hospitalised COVID-19 patients, mortality was lower than in other Danish and European case series.

FUNDING

none.

TRIAL REGISTRATION

not relevant.

Conservative vs liberal fluid therapy in septic shock (CLASSIC) trial-Protocol and statistical analysis plan

INTRODUCTION

Intravenous (IV) fluid is a key intervention in the management of septic shock. The benefits and harms of lower versus higher fluid volumes are unknown and thus clinical equipoise exists. We describe the protocol and detailed statistical analysis plan for the conservative versus liberal approach to fluid therapy of septic shock in the Intensive Care (CLASSIC) trial. The aim of the CLASSIC trial is to assess benefits and harms of IV fluid restriction versus standard care in adult intensive care unit (ICU) patients with septic shock.

METHODS

CLASSIC trial is an investigator-initiated, international, randomised, stratified, and analyst-blinded trial. We will allocate 1554 adult patients with septic shock, who are planned to be or are admitted to an ICU, to IV fluid restriction versus standard care. The primary outcome is mortality at day 90. Secondary outcomes are serious adverse events (SAEs), serious adverse reactions (SARs), days alive at day 90 without life support, days alive and out of the hospital at day 90 and mortality, health-related quality of life (HRQoL), and cognitive function at 1 year. We will conduct the statistical analyses according to a pre-defined statistical analysis plan, including three interim analyses. For the primary analysis, we will use logistic regression adjusted for the stratification variables comparing the two interventions in the intention-to-treat (ITT) population.

DISCUSSION

The CLASSIC trial results will provide important evidence to guide clinicians' choice regarding the IV fluid therapy in adults with septic shock.

Co-administration of iloprost and eptifibatide in septic shock (CO-ILEPSS)-a randomised, controlled, double-blind investigator-initiated trial investigating safety and efficacy

Background

Part of the pathophysiology in septic shock is a progressive activation of the endothelium and platelets leading to widespread microvascular injury with capillary leakage, microthrombi and consumption coagulopathy. Modulating the inflammatory response of endothelium and thrombocytes might attenuate this vicious cycle and improve outcome.

Method

The CO-ILEPSS trial was a randomised, placebo-controlled, double-blind, pilot trial. Patients admitted to the intensive care unit with septic shock were randomised and allocated in a 2:1 ratio to active treatment with dual therapy of iloprost 1 ng/kg/min and eptifibatide 0.5 μg/kg/min for 48 h or placebo. The primary outcomes were changes in biomarkers reflecting endothelial activation and disruption, platelet consumption and fibrinolysis. We compared groups with mixed models, post hoc Wilcoxon signed-rank test and Mann-Whitney U test.

Results

We included 24 patients of which 18 (12 active, 6 placebo) completed the full 7-day trial period and were included in the per-protocol analyses of the primary outcomes. Direct comparison between groups showed no differences in the primary outcomes. Analyses of within-group delta values revealed that biomarkers of endothelial activation and disruption changed differently between groups with increasing levels of thrombomodulin (p = 0.03) and nucleosomes (p = 0.02) in the placebo group and decreasing levels of sE-Selectin (p = 0.007) and sVEGFR1 (p = 0.005) in the active treatment group. Platelet count decreased the first 48 h in the placebo group (p = 0.049) and increased from baseline to day 7 in the active treatment group (p = 0.023). Levels of fibrin monomers declined in the active treatment group within the first 48 h (p = 0.048) and onwards (p = 0.03). Furthermore, there was a significant reduction in SOFA score from 48 h (p = 0.024) and onwards in the active treatment group.

Intention-to-treat analyses of all included patients showed no differences in serious adverse events including bleeding, use of blood products or mortality.

Conclusion

Our results could indicate benefit from the experimental treatment with reduced endothelial injury, reduced platelet consumption and ensuing reduction in fibrinolytic biomarkers along with improved SOFA score. The results of the CO-ILEPSS trial are exploratory and hypothesis generating and warrant further investigation in a large-scale trial.

Trial registration

Clinicaltrials.com, NCT02204852 (July 30, 2014); EudraCT no. 2014-002440-41

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2573-8) contains supplementary material, which is available to authorized users.

Mortality in critical illness: The impact of asymmetric dimethylarginine on survival-A systematic review and meta-analysis

INTRODUCTION

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of the nitric oxide system, may be associated with an adverse outcome in critically ill patients. The aim of the present review was to clarify if plasma ADMA and the arginine-to-ADMA ratio (arginine/ADMA) are associated with mortality in critically ill patients.

METHODS

We searched PubMed, EMBASE and Web of Science/BIOSIS Previews on 31 July 2017 for studies published after 2000 including critically ill paediatric or adult patients and evaluating any association between all-cause mortality and admission ADMA and/or arginine/ADMA ratio. We pooled data from studies providing sufficient data in random effects meta-analyses.

RESULTS

We identified 15 studies including a total of 1300 patients. These studies have a medium to high risk of bias and substantial clinical heterogeneity. After contacting authors for homogenous data, six studies including 705 patients could be included in a formal meta-analysis. This analysis revealed a strong association between high plasma ADMA upon admission and mortality (pooled odds ratio 3.13; 95% confidence interval (CI) 1.78-5.51). A significant association between ADMA/arginine ratio and mortality was found in two studies only (54 patients) out of a total of six studies (564 patients).

CONCLUSIONS

A high plasma ADMA level upon admission is strongly associated with mortality in critically ill patients. However, there is no association between the arginine/ADMA ratio and mortality in this group of patients. The pathophysiological role of ADMA in circulatory collapse and its potential as a target for intervention remains to be explored.

Hypophosphatemia and duration of respiratory failure and mortality in critically ill patients

BACKGROUND

Hypophosphatemia has been associated with prolonged duration of respiratory failure and increased mortality in critically ill patients, but there is very limited evidence supporting the negative effects of low phosphate. We examined the association between hypophosphatemia at ICU admission and time to successful weaning and 28-day mortality.

METHODS

This was a cohort study that included all mechanically ventilated adult patients admitted to the ICU in 2013 at Nordsjaellands Hospital. Hypophosphatemia was defined as a serum level below 0.80 mmol/L. Multivariate Cox-regression was used to evaluate the effect of hypophosphatemia on mechanical ventilation and 28-day mortality. Multiple imputation was used to adjust for missing values.

RESULTS

A total of patients were admitted during the study period, of whom 190 were eligible. 122 (64.2%) had serum phosphate levels measured during the first 24 hours of admission, of whom 25 (20.5%) were found to be hypophosphatemic. About 74% of patients were successfully weaned from the ventilator within 28 days. Hypophosphatemia was not associated with this outcome (HR: 0.56; 95% CI: 0.30-1.04; P = .067). All-cause 28-day mortality was 32.6%. Hypophosphatemia was also not associated with 28-day mortality (HR: 1.64; 95% CI: 0.65-4.17; P = .447). Similar results were present in supplementary analysis where missing data were included by means of multiple imputation.

CONCLUSION

Hypophosphatemia at ICU admission was not associated with prolonged respiratory failure nor mortality. Further studies are warranted, where phosphate is measured systematically on all patients to elucidate the effect of low phosphate on relevant outcomes.

[Nitric oxide and sepsis]

The main purpose of this study is to review the function of nitric oxide during sepsis and septic shock. Futhermore, the study reviews the various physiological functions of nitric oxide in the human body, and how these functions can and have been used clinically. Nitric oxide plays an important role during septic shock in contributing to development of hypotension, multiorgan failure and lack of response to pressor therapy. Elevated concentrations of nitric oxide in both circulation and expiratory air have been found in hu-mans and animals during sepsis and septic shock. Further-more, studies show that nictric oxide plays an important role in the immune system. The physiological effect of nitric oxide has been used in various treatments.

[Treatment of hyperthermia]

Hyperthermia is an uncontrolled elevation of body temperature exceeding the body's ability to dissipate heat. Hyperthermia can result in dangerously high core temperatures and can rapidly become fatal. Common causes include heat stroke, malignant hyperthermia, serotonin syndrome, neuroleptic syndrome, a few endocrine emergencies as well as numerous intoxications. Rapid diagnosis and prompt cooling are pivotal, since the condition triggers a cascade of metabolic events which may progress to irreversible injury or death. Ice-water immersion and evaporative cooling are the methods of choice.

Serum and plasma neutrophil gelatinase associated lipocalin (NGAL) levels are not equivalent in patients admitted to intensive care

BACKGROUND

Neutrophil gelatinase associated lipocalin (NGAL) is proposed as a biomarker of acute kidney injury (AKI). NGAL has been studied in a range of body fluids including serum and EDTA plasma. The aim of the present study was to establish relationship between serum NGAL concentrations and EDTA plasma NGAL concentrations in patients admitted to intensive care units (ICUs) and whether these determinations are directly comparable in this setting.

METHODS

NGAL was measured in 40 paired samples of serum and EDTA plasma from 25 patients admitted to intensive care with a commercial particle-enhanced turbidimetric immunoassay (The NGAL Test™, BioPorto Diagnostics A/S, Gentofte, Denmark) on a Roche Hitachi 917 (Roche-Hitachi, Inc., Tokyo, Japan) analyzer.

RESULTS

Serum NGAL concentrations ranged from 26.8 to 1,808 ng/ml (median 281 ng/ml, interquartile range (IQR) 453 ng/ml). EDTA plasma NGAL concentrations ranged from 25.7 to 1,752 ng/ml (median 225 ng/ml, IQR 352 ng/ml). The difference in NGAL concentrations in paired serum and EDTA plasma samples (serum- plasma) ranged from -13.8 to 321 ng/ml (median 79 ng/ml, IQR 116 ng/ml; difference from zero, P < 0.0001, Wilcoxon's signed rank test). Although serum and EDTA plasma values were correlated (Spearman's r = 0.95, P < 0.0001), Deming regression analysis showed a slope of 1.1 that was not significantly different from unity (95% confidence interval (CI) 1.0-1.1) and a highly significant intercept of 67.9 ng/ml with a wide confidence interval (95% CI 29.8-106).

CONCLUSION

NGAL concentration values measured in serum and EDTA plasma cannot be directly compared and should not be used as equivalents in studies of patients admitted to intensive care.

Kidney failure related to broad-spectrum antibiotics in critically ill patients: secondary end point results from a 1200 patient randomised trial

OBJECTIVES

To explore whether a strategy of more intensive antibiotic therapy leads to emergence or prolongation of renal failure in intensive care patients.

DESIGN

Secondary analysis from a randomised antibiotic strategy trial (the Procalcitonin And Survival Study). The randomised arms were conserved from the primary trial for the main analysis.

SETTING

Nine mixed surgical/medical intensive care units across Denmark.

PARTICIPANTS

1200 adult intensive care patients, 18+ years, expected to stay +24 h.

EXCLUSION CRITERIA

bilirubin >40 mg/dl, triglycerides >1000 mg/dl, increased risk from blood sampling, pregnant/breast feeding and psychiatric patients.

INTERVENTIONS

Patients were randomised to guideline-based therapy ('standard-exposure' arm) or to guideline-based therapy supplemented with antibiotic escalation whenever procalcitonin increased on daily measurements ('high-exposure' arm).

MAIN OUTCOME MEASURES

Primary end point: estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2). Secondary end points: (1) delta eGFR after starting/stopping a drug and (2) RIFLE criterion Risk 'R', Injury 'I' and Failure 'F'. Analysis was by intention to treat.

RESULTS

28-day mortality was 31.8% and comparable (Jensen et al, Crit Care Med 2011). A total of 3672/7634 (48.1%) study days during follow-up in the high-exposure versus 3016/6949 (43.4%) in the 'standard-exposure arm were spent with eGFR <60 ml/min/1.73 m(2), p<0.001. In a multiple effects model, 3 piperacillin/tazobactam was identified as causing the lowest rate of renal recovery of all antibiotics used: 1.0 ml/min/1.73 m(2)/24 h while exposed to this drug (95% CI 0.7 to 1.3 ml/min/1.73 m(2)/24 h) vs meropenem: 2.9 ml/min/1.73 m(2)/24 h (2.5 to 3.3 ml/min/1.73 m(2)/24 h)); after discontinuing piperacillin/tazobactam, the renal recovery rate increased: 2.7 ml/min/1.73 m(2)/24 h (2.3 to 3.1 ml/min/1.73 m(2) /24 h)). eGFR <60 ml/min/1.73 m(2) in the two groups at entry and at last day of follow-up was 57% versus 55% and 41% versus 39%, respectively.

CONCLUSIONS

Piperacillin/tazobactam was identified as a cause of delayed renal recovery in critically ill patients. This nephrotoxicity was not observed when using other beta-lactam antibiotics.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00271752.

Fluid volume and osmoregulation in humans after a week of head-down bed rest

Body fluid homeostasis was investigated during chronic bed rest (BR) and compared with that of acute supine conditions. The hypothesis was tested that 6 degrees head-down BR leads to hypovolemia, which activates antinatriuretic mechanisms so that the renal responses to standardized saline loading are attenuated. Isotonic (20 ml/kg body wt) and hypertonic (2.5%, 7.2 ml/kg body wt) infusions were performed in eight subjects over 20 min following 7 and 10 days, respectively, of BR during constant sodium intake (200 meq/day). BR decreased body weight (83.0 +/- 4.8 to 81.8 +/- 4.4 kg) and increased plasma osmolality (285.9 +/- 0.6 to 288.5 +/- 0.9 mosmol/kgH(2)O, P < 0.05). Plasma ANG II doubled (4.2 +/- 1.2 to 8.8 +/- 1.8 pg/ml), whereas other endocrine variables decreased: plasma atrial natriuretic peptide (42 +/- 3 to 24 +/- 3 pg/ml), urinary urodilatin excretion rate (4.5 +/- 0.3 to 3.2 +/- 0.1 pg/min), and plasma vasopressin (1.7 +/- 0.3 to 0.8 +/- 0.2 pg/ml, P < 0.05). During BR, the natriuretic response to the isotonic saline infusion was augmented (39 +/- 8 vs. 18 +/- 6 meq sodium/350 min), whereas the response to hypertonic saline was unaltered (32 +/- 8 vs. 29 +/- 5 meq/350 min, P < 0.05). In conclusion, BR elicits antinatriuretic endocrine signals, but it does not attenuate the renal natriuretic response to saline stimuli in men; on the contrary, the response to isotonic saline is augmented.

Antihypertensive effect of 0.1-Hz blood pressure oscillations to the kidney

BACKGROUND

Physiological blood pressure (BP) fluctuations with frequencies >0.1 Hz can override renal blood flow autoregulation. The influence of such immediate changes in renal perfusion pressure (RPP) on daily BP regulation, eg, via shear stress-stimulated liberation of renal endothelial NO, however, is unknown. Thus, we studied the effects of such RPP oscillations on renal function and on systemic BP during the onset of renal hypertension.

METHODS AND RESULTS

Seven beagles (randomly assigned to each of the following protocols) were chronically instrumented for the measurement of systemic BP, RPP, and renal excretory function. An inflatable cuff was used to reduce and to oscillate RPP over 24 hours in the freely moving dog. Reducing RPP to 87+/-2 mm Hg diminished excretion of sodium and water and doubled plasma renin activity (PRA, n=7, P<0. 01) but had no significant effect on urinary nitrate excretion (n=6), a marker of NO generation. Superimposing 0.1-Hz oscillations (+/-10 mm Hg) onto the reduced RPP blunted hypertension, returned fluid excretion almost to control levels, and doubled renal sodium elimination. Nitrate excretion peaked at 8 hours, only to return to control values shortly thereafter. PRA, conversely, was significantly reduced during the last third of the experimental protocols.

CONCLUSIONS

BP fluctuations transiently stimulate NO liberation and induce a reduction in PRA, which enhances 24-hour sodium and water excretion and markedly attenuates the acute development of renovascular hypertension.

Gastrointestinal osmoreceptors and renal sodium excretion in humans

The hypothesis that natriuresis can be induced by stimulation of gastrointestinal osmoreceptors was tested in eight supine subjects on constant sodium intake (150 mmol NaCl/day). A sodium load equivalent to the amount contained in 10% of measured extracellular volume was administered by a nasogastric tube as isotonic or hypertonic saline (850 mM). In additional experiments, salt loading was replaced by oral water loading (3.5% of total body water). Plasma sodium concentration increased after hypertonic saline (+3.1 +/- 0.7 mM), decreased after water loading (-3.8 +/- 0.8 mM), and remained unchanged after isotonic saline. Oncotic pressure decreased by 9.4 +/- 1.2, 3.7 +/- 1.2, and 10.7 +/- 1.3%, respectively. Isotonic saline induced an increase in renal sodium excretion (104 +/- 15 to 406 +/- 39 micromol/min) that was larger than seen with hypertonic saline (85 +/- 15 to 325 +/- 39 micromol/min) and water loading (88 +/- 11 to 304 +/- 28 micromol/min). Plasma ANG II decreased to 22 +/- 6, 35 +/- 6, and 47 +/- 5% of baseline after isotonic saline, hypertonic saline, and water loading, respectively. Plasma atrial natriuretic peptide (ANP) concentrations and urinary excretion rates of endothelin-1 were unchanged. In conclusion, stimulation of osmoreceptors by intragastric infusion of hypertonic saline is not an important natriuretic stimulus in sodium-replete subjects. The natriuresis after intragastric salt loading was independent of ANP but can be explained by inhibition of the renin-angiotensin system.

Blood pressure and plasma catecholamines in acute and prolonged hypoxia: effects of local hypothermia

This study measured the pressor and plasma catecholamine response to local hypothermia during adaptation to hypobaric hypoxia. Eight healthy men were studied at rest and after 10 and 45 min of local cooling of one hand and forearm as well as after 30 min of rewarming at sea level and again 24 h and 5 days after rapid, passive transport to high altitude (4,559 m). Acute mountain sickness scores ranged from 5 to 16 (maximal attainable score: 20) on the first day but were reduced to 0-8 by the fifth day. Systolic blood pressure, heart rate, and plasma epinephrine increased on day 1 at altitude compared with sea level but declined again on day 5, whereas diastolic and mean blood pressures continued to rise in parallel with plasma norepinephrine. With local cooling, an increased vasoactive response was seen on the fifth day at altitude. Very high pressures were obtained, and the pressure elevation was prolonged. Heart rate increased twice as much on day 5 compared with the other two occasions. Thoracic fluid index increased with cooling on day 5, suggesting an increase in pulmonary vascular resistance. In conclusion, prolonged hypoxia seems to elicit an augmented pressor response to local cooling in the systemic and most likely also the pulmonary circulation.

Isotonic and hypertonic sodium loading in supine humans

The hypothesis that hypertonic saline infusion induces a greater natriuresis than infusion of the same amount of sodium as isotonic saline was tested in 8 supine subjects on fixed sodium intake of 150 mmol NaCl day(-1). Sodium loads equivalent to the amount of sodium contained in 10% of measured extracellular volume were administered intravenously over 90 min either as isotonic saline or as hypertonic saline (850 mmol L(-1)). A third series without saline infusion served as time control. Experiments lasted 8 h. Water balance and sodium loads were maintained by replacing the excreted amounts every hour. Plasma sodium concentrations only increased following hypertonic saline infusion (by 2.7 +/- 0.3 mmol L(-1)). Oncotic pressure decreased significantly more with isotonic saline (4.1 +/- 0.3 mmHg) than with hypertonic saline (3.2 +/- 0.2 mmHg), indicating that isotonic saline induced a stronger volumetric stimulus. Renal sodium excretion increased more than a factor of four with isotonic and hypertonic saline but also increased during time control (factor of three). Cumulated sodium excretions following isotonic (131 +/- 13 mmol) and hypertonic saline (123 +/- 10 mmol) were statistically identical exceeding that of time control (81 +/- 9 mmol). Plasma angiotensin II decreased in all series but plasma ANP concentrations and urinary excretion rates of endothelin-1 remained unchanged. In conclusion, hypertonic saline did not produce excess natriuresis. However, as the two loading procedures induced similar natriureses during different volumetric stimuli, part of the natriuresis elicited by hypertonic saline could be mediated by stimulation of osmoreceptors involved in renal sodium excretion. The supine position does not provide stable time control conditions with regard to renal excretory function.

Cardiovascular, endocrine, and renal effects of urodilatin in normal humans

Effects of urodilatin (5, 10, 20, and 40 ng. kg-1. min-1) infused over 2 h on separate study days were studied in eight normal subjects with use of a randomized, double-blind protocol. All doses decreased renal plasma flow (hippurate clearance, 13-37%) and increased fractional Li+ clearance (7-22%) and urinary Na+ excretion (by 30, 76, 136, and 99% at 5, 10, 20, and 40 ng. kg-1. min-1, respectively). Glomerular filtration rate did not increase significantly with any dose. The two lowest doses decreased cardiac output (7 and 16%) and stroke volume (10 and 20%) without changing mean arterial blood pressure and heart rate. The two highest doses elicited larger decreases in stroke volume (17 and 21%) but also decreased blood pressure (6 and 14%) and increased heart rate (15 and 38%), such that cardiac output remained unchanged. Hematocrit and plasma protein concentration increased with the three highest doses. The renin-angiotensin-aldosterone system was inhibited by the three lowest doses but activated by the hypotensive dose of 40 ng. kg-1. min-1. Plasma vasopressin increased by factors of up to 5 during infusion of the three highest doses. Atrial natriuretic peptide immunoreactivity (including urodilatin) and plasma cGMP increased dose dependently. The urinary excretion rate of albumin was elevated up to 15-fold (37 +/- 17 micrograms/min). Use of a newly developed assay revealed that baseline urinary urodilatin excretion rate was low (<10 pg/min) and that fractional excretion of urodilatin remained below 0.1%. The results indicate that even moderately natriuretic doses of urodilatin exert protracted effects on systemic hemodynamic, endocrine, and renal functions, including decreases in cardiac output and renal blood flow, without changes in arterial pressure or glomerular filtration rate, and that filtered urodilatin is almost completely removed by the renal tubules.

Ten days of head down tilt: effects of isotonic and hypertonic saline loads in normal man

The initial response to bed rest involves an increase in central blood volume leading to a an enhanced renal excretion of fluid and electrolytes. Within 24 hours of head-down bed rest a new steady state condition occurs with a sustained reduction of plasma volume, extracellular fluid volume, total body water, and body weight. It was the purpose of the present study to elucidate the volume homeostatic mechanisms during head-down bed rest by investigating the endocrine and renal responses to a load of sodium chloride given as either an isotonic or a hypertonic solution.

Renal effects of urodilatin and atrial natriuretic peptide in volume expanded conscious dogs

The renal effects of urodilatin and atrial natriuretic peptide (ANP) were examined in conscious dogs during acute volume expansion maintained through independent infusions of water and NaCl. Peptide was infused in a step-up fashion, in 40-min periods at rates of 2.5, 12.5 and 50.0 ng kg-1 min-1 (ANP, urodilatin) or 0.5, 2.5 and 10.0 ng kg-1 min-1 (second series of urodilatin). ANP immunoreactivity (ANPir) in plasma was measured with an antibody showing 100% cross-reactivity with urodilatin. At 50 ng kg-1 min-1, ANP increased plasma ANPir some 10-fold (64 +/- 6 pg ml-1 to 728 +/- 82 pg ml-1) while urodilatin elicited a 25-fold increase in ANPir (78 +/- 13 pg ml-1 to 1645 +/- 204 pg ml-1). ANP doubled sodium excretion (61 +/- 12 to 124 +/- 30 mumol min-1, P < 0.05) while urodilatin increased sodium excretion to 269 +/- 45 mumol min-1. Both peptides approximately doubled urine flow. Urodilatin at 10 ng kg-1 min-1 increased sodium excretion from 57 +/- 17 mumol min-1 to 106 +/- 25 mumol min-1, i.e. similar to the response ANP elicited at 50 ng kg-1 min-1. In the time control series a significant fall in sodium excretion was observed, despite the continuous replacement of sodium and water. The results demonstrate that in identical, relatively high doses, the changes in sodium excretion, diuresis, heart rate (HR) and arterial pressures elicited by urodilatin are more pronounced than those of ANP.(ABSTRACT TRUNCATED AT 250 WORDS)