Global peatland initiation driven by regionally asynchronous warming.

Widespread establishment of peatlands since the Last Glacial Maximum represents the activation of a globally important carbon sink, but the drivers of peat initiation are unclear. The role of climate in peat initiation is particularly poorly understood. We used a general circulation model to simulate local changes in climate during the initiation of 1,097 peatlands around the world. We find that peat initiation in deglaciated landscapes in both hemispheres was driven primarily by warming growing seasons, likely through enhanced plant productivity, rather than by any increase in effective precipitation. In Western Siberia, which remained ice-free throughout the last glacial period, the initiation of the world's largest peatland complex was globally unique in that it was triggered by an increase in effective precipitation that inhibited soil respiration and allowed wetland plant communities to establish. Peat initiation in the tropics was only weakly related to climate change, and appears to have been driven primarily by nonclimatic mechanisms such as waterlogging due to tectonic subsidence. Our findings shed light on the genesis and Holocene climate space of one of the world's most carbon-dense ecosystem types, with implications for understanding trajectories of ecological change under changing future climates.

Ecosystem state shifts during long-term development of an Amazonian peatland.

The most carbon (C)-dense ecosystems of Amazonia are areas characterized by the presence of peatlands. However, Amazonian peatland ecosystems are poorly understood and are threatened by human activities. Here, we present an investigation into long-term ecohydrological controls on C accumulation in an Amazonian peat dome. This site is the oldest peatland yet discovered in Amazonia (peat initiation ca. 8.9 ka BP), and developed in three stages: (i) peat initiated in an abandoned river channel with open water and aquatic plants; (ii) inundated forest swamp; and (iii) raised peat dome (since ca. 3.9 ka BP). Local burning occurred at least three times in the past 4,500 years. Two phases of particularly rapid C accumulation (ca. 6.6-6.1 and ca. 4.9-3.9 ka BP), potentially resulting from increased net primary productivity, were seemingly driven by drier conditions associated with widespread drought events. The association of drought phases with major ecosystem state shifts (open water wetland-forest swamp-peat dome) suggests a potential climatic control on the developmental trajectory of this tropical peatland. A third drought phase centred on ca. 1.8-1.1 ka BP led to markedly reduced C accumulation and potentially a hiatus during the peat dome stage. Our results suggest that future droughts may lead to phases of rapid C accumulation in some inundated tropical peat swamps, although this can lead ultimately to a shift to ombrotrophy and a subsequent return to slower C accumulation. Conversely, in ombrotrophic peat domes, droughts may lead to reduced C accumulation or even net loss of peat. Increased surface wetness at our site in recent decades may reflect a shift towards a wetter climate in western Amazonia. Amazonian peatlands represent important carbon stores and habitats, and are important archives of past climatic and ecological information. They should form key foci for conservation efforts.

A calibration of cellulose isotopes in modern prostrate Nothofagus and its application to fossil material from Antarctica.

Carbon and oxygen isotopes (δ13C and δ18O) in tree rings are widely used to reconstruct palaeoclimate variables such as temperature during the Holocene (12 thousand years ago - present), and are used increasingly in deeper time. However, their use is largely restricted to arboreal trees, which excludes potentially important data from prostrate trees and shrubs, which grow in high latitude and altitude end-member environments. Here, we calibrate the use of δ13C and δ18O as climatic archives in two modern species of southern beech (Nothofagus) from Tierra del Fuego, Chile, at the southern limit of their current range. We show that prostrate trees are potentially suitable archives for recording climatological means over longer periods (on the order of decades), which opens up these important environments for tree ring isotope analysis. We then apply our new understanding to a remarkable late Neogene (17-2.5 Ma) fossil Nothofagus assemblage from the Transantarctic Mountains, Antarctica, representative of a prostrate tundra shrub growing during a period of significant ice sheet retreat. The δ13C of the fossil cellulose was found to be ~4‰ enriched relative to that of the modern tress. This is likely to be due to a combination of a more positive δ13C of contemporaneous atmospheric CO2 and enhanced water use efficiency at the fossil site. Using the cellulose-δ18O in the fossil wood, we are able to reconstruct precipitation oxygen isotopes over the Antarctic interior for the first time for this time period. The results show that δ18Oprecip over Antarctica was -16.0 ± 4.2‰, around 12‰ enriched relative to today, suggesting changes in the hydrological cycle linked to warmer temperatures and a smaller ice sheet.

Coherent deglacial changes in western Atlantic Ocean circulation.

Abrupt climate changes in the past have been attributed to variations in Atlantic Meridional Overturning Circulation (AMOC) strength. However, the exact timing and magnitude of past AMOC shifts remain elusive, which continues to limit our understanding of the driving mechanisms of such climate variability. Here we show a consistent signal of the 231Pa/230Th proxy that reveals a spatially coherent picture of western Atlantic circulation changes over the last deglaciation, during abrupt millennial-scale climate transitions. At the onset of deglaciation, we observe an early slowdown of circulation in the western Atlantic from around 19 to 16.5 thousand years ago (ka), consistent with the timing of accelerated Eurasian ice melting. The subsequent weakened AMOC state persists for over a millennium (~16.5-15 ka), during which time there is substantial ice rafting from the Laurentide ice sheet. This timing indicates a role for melting ice in driving a two-step AMOC slowdown, with a positive feedback sustaining continued iceberg calving and climate change during Heinrich Stadial 1.

Treatment of hypertensive crisis in children with nifedipine.

We report 31 episodes of hypertensive crises in children, managed with sublingual nifedipine at the following dosages: 10 mg in children with body weight (BW) higher than 20 kg, 5 mg in children with BW between 10 and 20 kg, and 2.5 mg in children with BW below 10 kg. The mean initial blood pressures were 161.41 mm Hg for the systolic pressure (mSBP) and 111.25 mm Hg for the diastolic pressure (mDBP). After nifedipine, both the mSBP and the mDBP decreased, with onset of effect five minutes after dosage and maximum decrease at 60 min (mSBP 134.93 mm Hg, mDBP 79.23 mm Hg, for decreases of 16.4 and 28.7%, respectively), and this effect persisted for 180 min. Blood pressure increased again from min 240 to min 360, yet without reaching the initial levels. One case did not respond to the first dose of nifedipine and required a second one. The effect of nifedipine was more pronounced on the DBP than on the SBP, and greater reductions of both pressures were achieved in the cases with higher initial readings. No side of medication were observed in our patients.

Continuous arteriovenous haemofiltration in children.

Continuous arteriovenous haemofiltration (CAVH) was used in 7 critically ill children: a premature neonate with hypervolaemia secondary to hydrops foetalis and six children aged 9 days to 7 years with acute oliguric renal failure. Biospal 0.5 m2, Renaflo 0.25 m2, Gambro 0.15 m2 and Amicon 0.015 m2 filters were used according to the weights and ages of the patients. Adequate removal of water and solutes was obtained in 6 patients. One of the patients with the smallest filter needed a change to a filter with a larger surface area to improve water and solute removal. Haemofiltration was maintained for between 17 hours and 31 days and was well tolerated. CAVH was discontinued because of recovery of renal function in three patients, improvement of the hypervolaemic state in one, death in three, and transfer to continuous ambulatory peritoneal dialysis because of chronic renal failure in one patient. CAVH is a useful technique for the treatment of acute renal failure and hypervolaemia in critically ill children.

Analysis of costs in a pediatric ICU.

OBJECTIVE: To analyze the actual cost of pediatric intensive care and its different components, particularly the differences between various patient groups, with special reference to the variable cost and the elements included in it. DESIGN: Prospective, observational study. SETTING: Multidisciplinary 12-bed pediatric intensive care unit (PICU) in a tertiary university hospital. PATIENTS: 495 admissions to the unit over 17 consecutive months; 64.2% were medical patients and 35.8% were surgical patients; the mean (SE) stay in the PICU was 6.6 +/- 0.4 days. MEASUREMENTS AND RESULTS: The fixed cost per day per patient was calculated, including the costs of physicians, nurses, auxiliary and other personnel who worked during the study period, and the costs of structural depreciation, maintenance, consumption, and disposable material. The variable cost was individually calculated from the costs of routine procedures and also included expenditure on pharmaceuticals, blood products, biochemical, hematological, and bacteriologic tests, radiology, image diagnosis procedures, and other procedures. The Physiologic Stability Index (PSI) was obtained in the first 24 h after admission. The mean fixed cost per patient per day was u.s. $608, which represents 72% of the total patient cost during this study; 86% of this amount was for personnel (58% for nurses and auxiliary staff). Variable costs came to 28% of the total amount, and were $218 +/- 100 (M +/- SEM) per patient per day. In addition to the costs of their longer stay in the PICU, the daily variable costs of nonsurvivors were higher than those of survivors ($542 +/- 52 vs $179 +/- 7; p < 0.001). We classified the patients into four groups according to their PSI score in the first 24 h; variable daily costs increased (p < 0.05) in all comparisons with the PSI level: group I: < 4 points ($155 +/- 0.5), group II: 5-9 points ($210 +/- 13), group III: 10-14 points ($324 +/- 54), group IV: > 15 points ($480 +/- 42). However, this pattern was not found for all resources: the cost of treatment techniques and biochemical and hematological tests increased, but the consumption of antibiotics, parenteral nutrition, blood products, and bacteriologic tests reached their maximum level in groups I-III and radiology was not significantly influenced by PSI level. CONCLUSIONS: The cost of personnel was the biggest factor in intensive care costs: 62.4% of the total costs. Nonsurvivors generated 3 times the mean variable daily expenditure on survivors and had longer stays in the PICU. The increase in PSI score on the first day was associated with a global increase in variable costs. The cost of treatment techniques significantly increased as the illness became more severe but consumption of antibiotics and parenteral nutrition and use of bacteriologic tests and radiology did not.

Usefulness of gastric intramucosal pH for monitoring hemodynamic complications in critically ill children.

OBJECTIVE: To assess the efficacy of gastric intramucosal pH for the evaluation of tissue perfusion and prediction of hemodynamic complications in critically ill children. DESIGN: Open prospective study without controls. SETTING: Pediatric intensive care unit (ICU) of a tertiary care university pediatric hospital. PATIENTS: Thirty critically ill children (16 boys and 14 girls), age range: 3 months-12 years. MEASUREMENTS AND RESULTS: A tonometry catheter was placed in the stomach of all patients on admission to the pediatric ICU. Simultaneous tonometry and arterial gas measurements were made on admittance and every 6-12 h throughout the study; a total of 202 measurements were made. The catheter was removed after extubation and/or when the patient was hemodynamically stable. Intramucosal pH was calculated using the Henderson-Hasselbalch equation based on the pCO2 of the tonometer and arterial bicarbonate. Intramucosal pH values between 7.30 and 7.45 were considered to be normal. The patient's condition was analyzed using the Pediatric Risk Mortality Score (PRISM). The relations between intramucosal pH and the presence of major hemodynamic complications (cardiopulmonary arrest, shock), minor hemodynamic complications (hypotension, hypovolemia or arrhythmia), death, PRISM score and the duration of the stay in the pediatric ICU were analyzed. Intramucosal pH on admission was 7.48 +/- 0.15 on average (range 7.04-7.68). Five patients (16%) had an intramucosal pH lower than 7.30 on admission; these patients did not have a higher incidence of hemodynamic complications. The 16 patients (53%) who had an intramucosal pH of less than 7.30 at some time during the course of their disease had more hemodynamic complications than the patients who did not have pH lower than 7.30 (p < 0.0001). Every case of cardiopulmonary arrest and shock was related to intramucosal pH of less than 7.30. Patients with major complications (cardiopulmonary arrest and shock) had lower intramucosal pHs than those with minor hemodynamic complications (p = 0.03); similarly, they had low intramucosal pH readings more often than those with minor complications (p = 0.0032). Intramucosal pH values less than 7.30 had a sensitivity of 90% and a specificity of 98% as a predictor of hemodynamic complications. There was no relation between intramucosal pH lower than 7.30 and either PRISM or the duration of the stay in the pediatric ICU. Patients with intramucosal pH less than 7.20 had a higher PRISM than the patients who did not have pH lower than 7.20 (p < 0.05). A patient who died during the study due to cardiopulmonary arrest had prior intramucosal pH measurements of 7.23 and 7.10, and three patients died of late complications after the end of the study. Hemodynamic complications were not detected with arterial pH. Gap pH (arterial pH-intramucosal pH) and standard pH measurements yielded the same results as gastric intramucosal pH. CONCLUSION: Intramucosal pH could provide a useful early indication of hemodynamic complications in critically ill children.

[Alpha coma: clinical, electroencephalographic and aetiological correlation in childhood]. / Coma alfa: correlación clínica, electroencefalográfica y etiología en la edad pediátrica.

INTRODUCTION: Alpha coma is defined as the appearance, in an unconscious patient, of EEG activity in the alpha frequency band (8-13Hz). OBJECTIVE: To determine, in our setting, the incidence, aetiology, clinical significance and course of alpha coma in paediatric patients and review the literature. PATIENTS AND METHODS: We did a retrospective study of the patients admitted to a paediatric intensive care unit who had alpha activity recorded whilst in coma. RESULTS: Only two patients, aged 5 and 12 years, were found. Both had complex congenital cardiopathy and cardio-respiratory arrest one and twelve days postoperatively, respectively. Several EEGs were done whilst they were in coma. Barbiturate coma was not used. Both had clinical mid-brain involvement during alpha recording. The pattern was bilateral, arreactive and preceded by a theta pattern, appeared two days after the arrest, was maintained for two and three days in the two cases and was followed by delta pattern. The second case finally showed a 'burst-suppression'. The CAT was normal. The patients died 4 and 11 days after the appearance of alpha coma. CONCLUSIONS: Alpha coma is rare in childhood. Both the aetiology and the bad prognosis are similar to that of adults. Alpha coma is a transient EEG pattern occurring during the evolution of coma. We consider it to be due probably to mid-brain involvement.

[Acute renal failure after major surgery: effectiveness of continuous arterio-venous hemofiltration (CAVH)]. / Insuficiencia renal postcirugía mayor: utilidad de la hemofiltración arteriovenosa continua.

Thirteen patients with acute renal failure after mayor surgery were treated with CAVH, 6 children after liver transplantation (OLT) and 7 after extracorporeal cardiac surgery (ECS). The ages ranged from 4 months to 19 years, with filters from 0.16 m2 to 0.5 m2, according to the weights. CAVH was initiated 19 hours (mean) after OLT and 10.5 hours (mean) after ECS. Mean creatinine clearance was 6.3 ml/min/1.73 m2 (ECS) and 10.1 ml/min/1.73 m2 (OLT). Serum creatinine remained under acceptable values (mean 2.1 mg.%) in both groups. Mean fluid removal was 5.7 L/day (242 ml/kg/day), which allowed plasma administration despite oligoanuria in the OLT group. Fluid removal decreased central venous pressure (p < 0.001) and increased mean arterial pressure (p < 0.01) in the ECS group, and inotropic support could be diminished. CAVH was well tolerated and it was maintained for 79 hours (ECS) and 105 hours (OLT).

[Usefulness of intracoronary therapy with progenitor cells in patients with dilated cardiomyopathy: Bridge or alternative to heart transplantation?]. / Utilidad de la terapia intracoronaria con células progenitoras en pacientes con miocardiopatía dilatada: ¿puente o alternativa al trasplante cardiaco?

INTRODUCTION AND OBJECTIVES: Some paediatric publications have recently raised the value of intracoronary therapy with autologous bone marrow-derived progenitor cells (APCs) in children with dilated cardiomyopathy (DCM) and heart failure. We describe the usefulness of this treatment in two infants with severe DCM and heart failure, who had been transferred to our hospital for cardiac transplant evaluation. PATIENTS AND METHODS: The first patient was a 3 months old male weighing 4 kg. The second was a 4 months old male weighing 5 kg. At the time of admission, both were in poor clinical condition (NYHA IV), with severe dilation and systolic dysfunction (ejection fraction [EF]<30%) of the left ventricle and marked elevation of NT-proBNP, requiring treatment with mechanical ventilation and inotropic iv infusion. After mobilization with G-CSF for 4 days, APCs were obtained from peripheral blood by leukocytapheresis, administering them by a slow intracoronary bolus injection using a stop-flow technique (6.15x106 CD34-positive cells/Kg in the first patient, and 10.55x106 CD34-positive cells/Kg in the second). RESULTS: Since the first week after the procedure, clinical status of patients improved and echocardiography showed a decrease in left ventricular dilation. A month later, there was a significant improvement in EF (> 40%) and NT-proBNP levels, subsequently maintained throughout the follow-up. However, four months later in the first patient, the left ventricle dilated again and its function slightly worsened, but without any significant impact in his clinical status. CONCLUSIONS: Intracoronary therapy with APCs can be an alternative in children, especially infants, with DCM and heart failure. It can reduce the waiting list mortality, improve clinical status and provide more time on the waiting list to receive a suitable organ, or even to make transplantation unnecessary.

[Vein and arterial renal thrombosis in a newborn (author's transl)]. / Trombosis arterial y venosa en un recién nacido

A case of arterial and venous thrombosis in a newborn is presented. The etiopathogenic aspects are discussed, and the possible relationship between arterial and venous thrombosis in comparison with clinical renal vein thrombosis are evaluated. Appropriated treatment for these patients is presented.

[Hyperglycemia in hypertonic dehydration (author's transl)]. / Hiperglicemia en la deshidratación hipertónica.

Fourteen patients who developed hyperglycemia with hypertonic dehydration are reviewed, and compared to a control group of twenty-four dehydrated infants without hyperglycemia. The threshold of hyperglycemia was considered at 125 mg. %. The relationship between hyperglycemia and degree of formula concentration, incidence of shock and water and solute metabolism chemistry are analysed. The different theories about hyperglycemia in the course of hypertonic dehydration are discussed. Because of the negativity of other factors, authors suggest that the most important factor in hyperglycemia may be the ionic alteration of the cell.

[Complications on two cases of peritoneal dialysis (authors transl)]. / Dos casos de complicaciones de la diálisis peritoneal en niños.

Two newborns with abdominal perforation during peritoneal dialysis are presented. The first probably before dialysis and the second iatrogenic. Both needed surgical intervention. Incidence in children in comparation with adults is discussed. Severe clinic complications of both patients that needed complete parenteral nutrition, mechanic ventilation and treatment of Candida sepsis are comented. Both survived without sequels in spite of severe complications.

[Epidemiologic comments on hypertonic dehydration in Madrid (author's transl)]. / Comentarios epidemiológicos a la deshidratación hipertónica en Madrid

The epidemiologic factors are studied in 584 cases of Hypertonic Dehydration (H.D.) admitted to the Children's Clinic "La Paz" over a period of 5 years. The overall monthly mean (MMT) resulted in 9.75 children a month with a standard deviation of +/- 2.1. The overall monthly evolution is analysed according to the sex, the seasonal incidence, as well as the more relevant etiologic factors: Concentrated diet, diarrhoea, vomiting, respiratory pathology and fever. The epidemiologic peculiarities are discussed according to age.

[Uncommon malformative association (author's transl)]. / Asociación malformativa infrecuente: malformación cerebral, hipoplasia renal bilateral y aplasia cutis

An uncommon malformative association is presented ((hydrocephalus, bilateral renal hypoplasia, aplasia cutis) associated with neonatal gastrointestinal perforation. The bibliography related with these problems is reviewed, discussing the possible relationship between them. The etiological hypothesis is infective, and pathogenic interpretation is pointed out in this context.