700,000 years of tropical Andean glaciation.

Our understanding of the climatic teleconnections that drove ice-age cycles has been limited by a paucity of well-dated tropical records of glaciation that span several glacial-interglacial intervals. Glacial deposits offer discrete snapshots of glacier extent but cannot provide the continuous records required for detailed interhemispheric comparisons. By contrast, lakes located within glaciated catchments can provide continuous archives of upstream glacial activity, but few such records extend beyond the last glacial cycle. Here a piston core from Lake Junín in the uppermost Amazon basin provides the first, to our knowledge, continuous, independently dated archive of tropical glaciation spanning 700,000 years. We find that tropical glaciers tracked changes in global ice volume and followed a clear approximately 100,000-year periodicity. An enhancement in the extent of tropical Andean glaciers relative to global ice volume occurred between 200,000 and 400,000 years ago, during sustained intervals of regionally elevated hydrologic balance that modified the regular approximately 23,000-year pacing of monsoon-driven precipitation. Millennial-scale variations in the extent of tropical Andean glaciers during the last glacial cycle were driven by variations in regional monsoon strength that were linked to temperature perturbations in Greenland ice cores1; these interhemispheric connections may have existed during previous glacial cycles.

Effects of low-dose alfentanil administration on central respiratory drive and respiratory pattern in spontaneously breathing ASA 1 patients.

The aim of this study was to assess the short-term effects of the administration of low doses of alfentanil on respiratory drive and respiratory pattern. We studied 17 ASA I patients scheduled for minor surgery or endoscopic procedures. During spontaneous ventilation, Respiratory Rate, Tidal Volume, Total Respiratory Cycle, Inspiratory and Expiratory Time, Mean Inspiratory Flow, P0.1, S(a)O(2) and EtCO(2) were all measured. The inspired oxygen concentration was 21% and measurements were made at baseline, 5 min (T1), 10 min (T2) and 15 min (T3) following an intravenous bolus injection 10 microg.kg(-1) alfentanil. The administration of alfentanil produced a significant (p < 0.05) reduction in S(a)O(2), minute volume and P0.1. In ASA I spontaneously breathing patients, the pre-operative administration of low doses of alfentanil can initially reduce the respiratory centre activity leading to a reduction in minute volume and S(a)O(2). We therefore recommend careful monitoring of cardio-respiratory function in ASA I patients, following the administration of alfentanil.

Effect of low dose fentanyl-droperidol administration on respiratory drive, respiratory pattern and gas exchange in ASA 1 spontaneously breathing patients.

The aim of this study was to investigate the short term effects of low doses of fentanyl and droperidol on central respiratory drive, gas exchanges, respiratory pattern and inspiratory impedance of the respiratory system in a group of ASA 1 patients. Fourteen ASA 1 patients scheduled for minor surgery or endoscopic procedures were enrolled in the study, thirty minutes before the intervention. During spontaneous breathing of air we evaluated, by recording airflow, airway opening pressure and volume, the following variables: Respiratory Rate (RR), Tidal Volume (TV), Total respiratory cycle, Inspiratory and Expiratory Time (Ti, Te), mean inspiratory flow, P0.1, pH, PaO2 and PaCO2. After obtaining basal measurements, droperidol and fentanyl were injected and the above mentioned variables evaluated at 5 min (T1), 10 min (T2), 15 min (T3) intervals. Arterial blood was age, sampled at T3 for blood gas evaluation. The administration of droperidol (0.1 mg/kg) and fentanyl (0.002 mg/kg) significantly reduced P0.1 and Tidal Volume comparing basal with T1 and, T2 values. The other variables did not significantly modify. Two patients showed transient respiratory rhythm abnormalities in the first 180 sec following the administration of droperidol+fentanyl. Our results suggest that, in ASA 1 patients, droperidol+fentanyl preoperative administration, has no significant effects on respiratory pattern, respiratory impedance and gas exchanges: however also at low doses, the association of droperidol+fentanyl can reduce the respiratory center activity, expressed as P0.1, with a consequent reduction in Tidal Volume.

[Regional intravenous anesthesia (RIA): a simple method not used frequently]. / Anestesia regionale endovenosa (ARE): una metodica semplice ma poco utilizzata.

We studied 20 outpatients undergoing surgery of the extremities with regional intravenous anesthesia (RIA). In our study RIA vas performed with the help of a double tourniquet in order to prevent adverse reactions; the drug of choice was lidocaine, because we considered it more suitable for this kind of procedure. The technique was of simple execution and well tolerated by the patient. This technique maker it possible to perform surgery of forearm and foot with a small amount of anesthetic even in outpatients.

[Problems related to resuscitation in studies with contrast media]. / Problematiche di interesse rianimatorio nelle indagini contrastografiche.

This study has the purpose of describing indications and legal implications related to the intravascular use of contrast media (ICM) in order to provide useful guidelines to the intensivist, often involved in the treatment of adverse reactions. The structure of modern contrast media (CM), is a benzenic ring carrying steadily three iodine ions. Adverse reactions due to the use of ICM, are local or systemic ranging from skin rashes or flushes (urticaria et al.), to cardiovascular, respiratory and neurologic symptoms. The prevention of these reactions is mandatory in patients reporting a history of allergy or atopia disease. From a legal point of view, the contraindication to procedures involving i.v. use of CM are not clearly pointed out therefore several concerns have been expressed. The intensivist is not required to physically attend the procedure, in agreement with the circular #64 edited in 1979; on the other hand his prompt intervention should be granted if necessary. Furthermore every therapeutic supply suitable for any resuscitational intervention should be available in the area where the test is performed. In conclusion we would like to stress the financial and ethic implications related to the choice of ICM (ionic versus non-ionic). The use of non-ionic CM offers several advantages: among them the better tolerance for the patient and the lower incidence of adverse reactions. However non-ionic CM have a cost ten-fold higher and both groups of drugs have same incidence of fatal reactions, therefore the use of non-ionic ICM is recommended for high risk patients.

[Effects of the nutritional status on the respiratory system]. / Influenza dello stato nutrizionale sull'apparato respiratorio.

Mechanically ventilated patients are at high risk for malnutrition, and it is now accepted that nutrition can influence the respiratory function. In particular, malnutrition can adversely affect lung function and the adverse effects of such malnutrition include: decreased ventilatory drive, decreased respiratory muscle function, alterations of lung parenchyma and depressed lung defense mechanisms. Therefore, nutrition support should be considered if a patients has a severe chronic pulmonary disease or an acute respiratory disease. Recent studies showed that malnourished patients have a reduced respiratory muscle strength and that nutritional intervention can return muscle ventilatory function to normal levels. Furthermore, it seems very likely that the ventilatory drive can be influenced by dietary intake of amino acids and glucose. The structure of the pulmonary parenchyma can be affected by starvation and the pulmonary defense mechanisms are depressed in malnourished patients. The incidence of post-operative pneumonia or atelectasis is higher in protein-depleted patients. in comparison with well-nourished patients. In conclusion, the importance of nutrition support in the management of patients with respiratory failure, particularly those mechanically ventilated, is stressed in the paper.

[Physiopathologic problems of obesity related to anesthesia]. / Problemi fisiopatologici dell'obesità in relazione all'anestesia.

Obesity, its complications and its treatment have a great importance for the anesthesiologist. The pathophysiological consequences of obesity involve great part of the organs so that the perioperative management of these subjects may affect surgical outcome. For this reason care should be taken to the peroperative evaluation of the obese patient regarding his pulmonary, metabolic and cardiac function. The anesthesiologist also needs to be aware of intraoperative problems caused by obesity. Recovery in ICU for a short time could be required for the prevention and treatment of post-operative complications.

Dehiscence of intestinal anastomoses and anaesthesia.

This study, carried out in 62 patients undergoing surgery under general anaesthesia, has evaluated the nestigmine effects on tone and motility of the muscular rectal wall, by recording compliance and manometric values. An increase of intrarectal pressure values in patients antagonized with neostigmine has been evidenced. This finding is related to contracture and increased motility of muscular rectal wall, induced by anticholinesterase agent. In patients eligible for intestinal anastomoses, rapidly eliminated myoneural blocker such as atracurium besylate or vecuronium, should be preferred. These agents allow a spontaneous reversal of the myoneural block, without pharmacologic antagonism.