Degree Of Hypoxemia Research Articles

Chronic in vivo hypoxia in various organs: Hypoxia-inducible factor-1α and apoptosis

We studied the in vivo persistence of hypoxia-inducible factor-1α (HIF-1α), main transducer of hypoxia, the differential response in organs exposed to the same degree of hypoxemia and the relationship with apoptosis. We measured HIF-1α (immunohistochemistry peroxidase and Western blot) and apoptosis (TUNEL) in heart, liver, kidney, gastrocnemius, and brain of rats exposed to chronic normobaric hypoxia (10% O 2) or normoxia (21% O 2) for 2 weeks. Despite same arterial O 2 pressure and increased hemoglobin concentration (219 ± 5 vs. 124 ± 4 g/L), the organs responded differently. While marked in brain, muscle, and kidney cortex, HIF-1α was undetectable in heart and liver. In kidney medulla, HIF-1α was high in both normoxia and hypoxia. By contrast, apoptosis was marked in heart, slight in kidney medulla, and undetectable in other organs. We conclude that the HIF-1α response to chronic hypoxia can be a sustained phenomenon, but not in all organs, and that apoptosis responds differently from HIF-1α.

Long-Term Neurodevelopmental Outcome and Exercise Capacity After Corrective Surgery for Tetralogy of Fallot or Ventricular Septal Defect in Infancy

The purpose of this prospective study was to assess whether neurodevelopmental status and exercise capacity of children 5 to 10 years after corrective surgery for tetralogy of Fallot or ventricular septal defect in infancy was different compared with normal children and influenced by the preoperative condition of hypoxemia or cardiac insufficiency. Forty unselected children, 20 with tetralogy of Fallot and hypoxemia and 20 with ventricular septal defect and cardiac insufficiency, operated on with combined deep hypothermic circulatory arrest and low flow cardiopulmonary bypass at a mean age of 0.7 +/- 0.3 years (mean +/- SD), underwent, at mean age 7.4 +/- 1.6 years, standardized evaluation of neurologic status, gross motor function, intelligence, academic achievement, language, and exercise capacity. Results were compared between the groups and related to preoperative, perioperative, and postoperative status and management. Rate of mild neurologic dysfunction was increased compared with normal children, but not different between the groups. Exercise capacity and socioeconomic status were not different compared with normal children and between the groups. Compared with the normal population, motor function, formal intelligence, academic achievement, and expressive and receptive language were significantly reduced (p < 0.01 to p < 0.001) in the whole group and in the subgroups, except for normal intelligence in ventricular septal defect patients. Motor dysfunction was significantly higher in the Fallot group compared with the ventricular septal defect group (p < 0.01) and correlated with neurologic dysfunction, lower intelligence, and reduced expressive language (p < 0.05 each). Reduced New York Heart Association functional class was correlated with lower exercise capacity and longer duration of cardiopulmonary bypass (p < 0.05 each). Reduced socioeconomic status significantly influenced dysfunction in formal intelligence (p < 0.01) and academic achievement (p < 0.05). Preoperative risk factors such as prenatal hypoxia, perinatal asphyxia, and preterm birth, factors of perioperative management such as cardiac arrest, lowest nasopharyngeal temperature, and age at surgery, and postoperative risk factors as postoperative cardiocirculatory insufficiency and duration of mechanical ventilation were not different between the groups and had no influence on outcome. Degree of hypoxemia in Fallot patients and degree of cardiac insufficiency in ventricular septal defect patients did not influence the outcome within the subgroups. Children with preoperative hypoxemia in infancy are at higher risk for motor dysfunction than children with cardiac insufficiency. Corrective surgery in infancy for tetralogy of Fallot or ventricular septal defect with combined circulatory arrest and low flow bypass is associated with reduced neurodevelopmental outcome, but not with reduced exercise capacity in childhood. In our experience, the general risk of long-term neurodevelopmental impairment is related to unfavorable effects of the global perioperative management. Socioeconomic status influences cognitive capabilities.

Cognitive and Functional Deterioration in Patients with Severe COPD

The objective of this study was to examine the association among the duration of COPD, degree of hypoxemia, and neurological abnormalities including cognitive functioning. Fifty-four patients with severe COPD and 24 age- and sex-matched controls, were included in the study. All patients and controls were administered pulmonary function tests, standardized Mini-mental State Examination (MMSE), Blessed Dementia Scale (BDS), Physical Self-maintenance Scale (PSMS), Modified Activities of Daily Living scale (MADL), Instrumental Activities of Daily Living scale (IADL), Cornell Scale for Depression in Dementia (CSDD), Global Deterioration Scale (GDS) and Clinical Dementia Rating (CDR). In addition, detailed physical and neurological examinations were performed. Sixty-four percent of patients with COPD showed abnormalities in MMSE, predominantly in recent memory, construction, attention, language, and orientation domains. Functional abnormalities were correlated with cognitive abnormalities. Although COPD patients did not show significant depression compared to controls, 77.7%. of the patients showed subjective and objective cognitive disturbance and 72.2% of the patients were classified as questionable or mild dementia. In conclusion, patients with COPD show significant cognitive and functional impairments that cannot be explained just by coincidence or by depression.

Das hepatopulmonale Syndrom - Wo stehen wir im Jahr 2006?

The hepato-pulmonary syndrome (HPS) is characterized by a combination of liver disease and pulmonary gas exchange abnormalities with arterial hypoxemia, intrapulmonary vasodilatation and arteriovenous shunting in the absence of intrinsic cardiopulmonary disease. The course of the disease is typically progressive. The mortality rate correlates with the pulmonary shunt volume and the degree of hypoxemia at room air. While the patho-physiology of HPS is still not fully understood, a multifactorial etiology is favored. Apart from functional intrapulmonary arteriovenous shunts which appear to represent a major factor in the development of HPS, both ventilation-perfusion mismatch and limited oxygen diffusion contribute to the HPS. Regarding its clinical appearance, pulmonary and hepatic symptoms have to be distinguished. Contrast echocardiography is the primary diagnostic tool. Symptomatically, hypoxemia can be treated with oxygen. So far, the only successful treatment approach which has been tested in larger patient groups, is liver transplantation. Given this background, the aim of this review is to critically discuss current concepts of this serious complication of liver diseases.

Model for end-stage liver disease (MELD) exception for hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) occurs when intrapulmonary vascular dilatation leads to abnormal arterial gas exchange in the setting of liver disease and/or portal hypertension. Over the past 15 years, HPS has emerged as a relatively common complication of cirrhosis, occurring in 15 to 20% of cases, and is an indication for liver transplantation (LT) in patients with significant hypoxemia. However, many clinical features of HPS that may influence exception to the Model for EndStage Liver Disease (MELD) scoring system, including standardized diagnostic criteria, preand post-LT mortality rates, and rate of progression of hypoxemia, are not fully characterized. The diagnosis of HPS is based on the presence of hypoxemia on room air due to intrapulmonary vascular dilatation in the setting of liver disease and/or portal hypertension. The prevalence of HPS (range, 12 to 32%) varies depending on whether abnormalities in arterial gas exchange are defined by an abnormal alveolar-arterial oxygen gradient or arterial hypoxemia (PaO2). 2-7 For the purpose of considering HPS for MELD exception, arterial hypoxemia (PaO2 60 mm Hg) detected in the sitting position (to avoid effects of positional changes on PaO2) is a reasonable standard. In a large prospective study of 200 LT candidates, pulse oximetry was found to be a useful screening technique for hypoxemia in patients with cirrhosis. The use of a screening oximetry threshold of 96% as a trigger for obtaining an arterial blood gas would have detected all patients with a PaO2 60 mm Hg and resulted in screening of 14% of the cohort. A proposed screening algorithm is provided in Figure 1. The most sensitive and appropriate screening test to detect intrapulmonary vascular dilatation is microbubble transthoracic contrast echocardiography. Although this is a qualitative test, it can also be used to screen for pulmonary hypertension and frequently distinguishes between intracardiac and intrapulmonary shunting. Radionuclide scanning with Tc99m-macroaggregated albumin (MAA), although quantitative, should not be used as a screening test because the MAA scanning technique is not standardized across centers, it is less sensitive than transthoracic contrast echocardiography, and it cannot distinguish between intracardiac and intrapulmonary shunting. In addition, up to 20 to 30% of patients with HPS have comorbidities that may contribute to hypoxemia (i.e., ascites, hydrothorax, pneumonia, chronic obstructive pulmonary disease). Therefore, it is appropriate to review cardiopulmonary data (i.e., chest x-ray, pulmonary function tests, computed tomographic scan of the chest) in all patients being considered for MELD exception. The major diagnostic use of the MAA scan, if performed and interpreted by means of standardized methodology, is in defining the contribution of HPS to hypoxemia in patients with comorbidities and PaO2 60 mm Hg. 8 If the MAA scan is positive for increased shunting, HPS is likely an important component of hypoxemia. The natural history and outcomes before and after LT in patients with HPS are incompletely characterized. Two recent single-center studies suggest that mortality in well-characterized patients with cirrhosis not undergoing LT is significantly increased in those with HPS compared with those without HPS, and that the degree of hypoxemia and severity of liver disease adversely influence outcome. However, the numbers of patients are small, and in one study, a subset of patients with HPS did not undergo LT because of comorbidities

Failure of non-invasive ventilation in patients with acute lung injury: observational cohort study

IntroductionThe role of non-invasive positive pressure ventilation (NIPPV) in the treatment of acute lung injury (ALI) is controversial. We sought to assess the outcome of ALI that was initially treated with NIPPV and to identify specific risk factors for NIPPV failure.MethodsIn this observational cohort study at the two intensive care units of a tertiary center, we identified consecutive patients with ALI who were initially treated with NIPPV. Data on demographics, APACHE III scores, degree of hypoxemia, ALI risk factors and NIPPV respiratory parameters were recorded. Univariate and multivariate regression analyses were performed to identify risk factors for NIPPV failure.ResultsOf 79 consecutive patients who met the inclusion criteria, 23 were excluded because of a do not resuscitate order and two did not give research authorization. Of the remaining 54 patients, 38 (70.3%) failed NIPPV, among them all 19 patients with shock. In a stepwise logistic regression restricted to patients without shock, metabolic acidosis (odds ratio 1.27, 95% confidence interval (CI) 1.03 to 0.07 per unit of base deficit) and severe hypoxemia (odds ratio 1.03, 95%CI 1.01 to 1.05 per unit decrease in ratio of arterial partial pressure of O2 and inspired O2 concentration – PaO2/FiO2) predicted NIPPV failure. In patients who failed NIPPV, the observed mortality was higher than APACHE predicted mortality (68% versus 39%, p < 0.01).ConclusionNIPPV should be tried very cautiously or not at all in patients with ALI who have shock, metabolic acidosis or profound hypoxemia.

Eisenmenger syndrome: medical prevention and management strategies

The original definition of Eisenmenger syndrome refers to an unrestrictive post-tricuspid valve congenital systemic-to-pulmonary shunt. When the pulmonary arterial systolic pressure becomes equal to the systemic arterial systolic pressure, the direction of the shunt becomes pulmonary-to-systemic. The latter leads to progressive cyanosis, and exercise intolerance is initially proportional to the degree of hypoxaemia. Later, congestive heart failure may occur. The management principle is to avoid any factors that destabilise this delicately balanced physiology. Until recently, this could only be achieved by symptomatic therapy; however, when patients are severely incapacitated, transplantation is needed. At present, new drugs, which are more selective pulmonary vasodilators, are available to interfere with the ongoing disease process to improve functional capacity and delay the decision for transplantation.

Prediction of hypoxemia after lung resection surgery

Pulmonary resection under general anesthesia induces various degrees of hypoxemia that adversely impacts on postoperative recovery. Consecutive of 53 patients undergoing anatomical pulmonary resection were enrolled in this study to accurately define predictors of postoperative hypoxemia. Preoperative variables studied included spirometric variables, blood gases, and extent of low attenuation area (below -910 Hounsfield units) on a three-dimensional computed tomography lung model. Arterial oxygen saturation was calculated from arterial partial pressure of oxygen measured 1 day before and 1 day after surgery with patients at rest breathing room air. Postoperatively, the patients were managed according to a standardized regimen. According to stepwise multiple regression analysis, preoperative oxygen saturation and the extent of low attenuation area were selected as the best predictors of postoperative oxygen saturation. Regression equation was generated with these two variables. The predicted postoperative oxygen saturation was significantly dependent on the length of management (P<0.01). Using a radiographic parameter, we established a novel means of predicting postoperative hypoxemia that impacted on postoperative recovery. Because this radiographic parameter was superior to conventional spirometric variables for prediction of postoperative hypoxemia, further confirmation of its usefulness in predicting risk after pulmonary resection is warranted.

Whole Lung Lavage and Extracorporeal Membrane Oxygenation in a Patient with Pulmonary Alveolar Proteinosis and Lung Cancer

Pulmonary alveolar proteinosis is characterized by accumulation of surfactant phospholipids and proteins within alveoli of the lungs. Sequential whole lung lavage is an accepted modality for treatment of pulmonary alveolar proteinosis. Generally, the degree of hypoxemia is tolerable while only one lung is being ventilated and the other is being lavaged. However, one patient became severely hypoxemic when one lung ventilation was performed through the left lung because of R-to-L shunt due to the lung cancer in the left lower lobe. Therefore, whole lung lavage on the right lung was successfully performed, while utilizing venovenous extracorporeal membrane oxygenation.

Perioperative risk factors evaluation of cleft palate repair in Pierre Robin sequence at early age

To evaluate the perioperative risk factors of the cleft palate repair in Pierre Robin sequence patients at early age and to investigate how to control the risk factors. Six consecutive patients with Pierre Robin sequence underwent primary repair of cleft palate in Department of Oral Maxillofacial Surgery, Peking University School of Stomatology from June 2001 to February 2004. The patients underwent von Longenbeck operation by the same perioperative observation of serum oxygen saturation were obtained for these patients. patients included 4 males and 2 females with age of 9 months to 5 surgeon. Pre- and post-operative polysomnographic studies and years. All the patients suffered various degree of hypoxaemia during the period of intubation. There was only one patient who had hypoxaemia within the first 2 hours during postanaesthetic recovery period. No obvious difference was found in apnea and hypopnea index (AHI) among the patients before and after operation. Severe hypoxaemia may happen in perioperative period when the patients with PRS underwent cleft palate repair. Most patients with PRS could undergo cleft palate repair safely performed by experienced surgeon at early age under comprehensive consideration and careful control of the risk factors.

Determinants of BMI in patients with COPD.

COPD is characterized by significant chronic inflammation that is evident not only in the pulmonary compartment but also in the circulation. Peripheral blood features of COPD include markers of oxidative stress and altered circulating levels of inflammatory mediators and acute-phase proteins. The presence of a systemic inflammatory response may influence quality of life by giving rise to weight loss, muscle wasting and tissue depletion. The aim of the present study was to evaluate the determinants of body mass and the value of serum tumour necrosis factor alpha (TNF-alpha) as a marker of weight loss in COPD patients, and to correlate this with the burden of oxidative stress as measured by serum malonyldialdehyde (MDA) levels. Fifty-two male COPD patients (mean age 62.55 +/- 6.81 years) were studied. After anthropometric measurements and standard spirometry, serum TNF-alpha concentration was measured by enzyme-linked immunosorbent assay using an hTNF-alpha kit, and MDA was studied spectrophotometrically using the Yoshioka-Kawada method. The mean BMI was 24.82 +/- 3.46. BMI was lower than normal (< 19) in six patients. Mean serum TNF-alpha concentration was 14.99 +/- 8.98 pg/mL and MDA was 0.93 +/- 0.13 nmol/L. There was no significant correlation between serum MDA and TNF concentrations (P = 0.140). Serum TNF-alpha and MDA concentrations were not correlated with severity of airflow obstruction or degree of hypoxaemia (P > 0.05 for all). BMI was negatively correlated with burden of smoking (pack-years) (r = -0.392, P= 0.004); but not with pulmonary function, degree of hypoxaemia, serum TNF-alpha or MDA levels. BMI was significantly lower in current smokers than ex-smokers (P = 0.041); however, serum MDA and TNF levels were similar in both groups. The results of this study indicate that body mass is related to smoking status (both pack-years and continuance of smoking) in COPD; however, serum TNF-alpha concentration does not seem to be a good marker of weight loss in these patients.

Prognostic factors for severe acute respiratory syndrome: a clinical analysis of 165 cases.

This study analyzes single factors that affect the prognosis of severe acute respiratory syndrome (SARS) and establishes a prognosis model by multivariate analysis. We retrospectively analyzed the clinical features of SARS in 165 clinically confirmed severe cases. Both age and existence of other diseases before SARS were significantly correlated with prognosis (r = 0.506 and r = 0.457, respectively; P < .001). During the acute phase of SARS, lactate dehydrogenase level, degree of hypoxemia, respiratory rate, α-hydroxybutyric dehydrogenase level, creatine kinase isoenzyme—MB, platelet count, and number of involved lobes noted on chest radiographs, and so on, correlated markedly with the prognosis (r = 0.257–0.788; P < .05). The multivariate prognosis regression model was associated with degree of hypoxemia and platelet count. The model was defined by the formula Py=1 = es/(1 + es), where S is [2.490 × degree of hypoxemia]-[0.050 × number of platelets], and it had a high sensitivity (91.67%), specificity (98.33%), and accuracy (96.42%). The model could be used to effectively judge the state of illness and the prognosis.

Cardiopulmonary complications during gastroscopy in patients with chronic respiratory failure undergoing long-term home oxygen therapy.

Gastric ulcer and hemorrhage are major complications in patients with chronic respiratory failure, but upper GI endoscopy tends to be avoided because of possible cardiopulmonary events. This study was designed to evaluate hypoxemia and subsequent cardiac complications during gastroscopic procedures in patients with chronic respiratory failure undergoing long-term home oxygen therapy (LHOT). Gastroscopy was carried out in 10 patients undergoing LHOT and 10 age-matched control subjects without pulmonary diseases. Oxygen saturation and cardiac arrhythmias before and during gastroscopy were monitored. Patients were given 10 mg intramuscular scopolamine butylbromide and local anesthesia using 100-300 mg lidocaine gel 15 minutes before the procedure. Each patient continued to receive oxygen via a nasal cannula in the same dosage as their daily use. Decrease in oxygen saturation during endoscopic procedure was significantly greater in patients undergoing LHOT (from 95.9+/-0.9 to 93.4+/-1.7%) compared with control subjects (from 96.7+/-0.4 to 96.2+/-0.4%). There was a significant correlation between the degree of hypoxemia and the oxygen dosage required for their daily treatment in the patients (r = 0.727, P<0.02). These results indicate that the degree of respiratory failure influences the degree of decrease in oxygen saturation during gastroscopy. It is suggested that use of the nasal route for oxygen supply may be one of the major causes of the hypoxemia.

Cor Pulmonale in Cystic Fibrosis

Cystic fibrosis is a common autosomal recessive disorder that is associated with a defective chloride transport channel in epithelial cells. The discovery of the cystic fibrosis gene in 1989 has led to a better understanding of the pathophysiology of the disease and the development of more effective therapeutic interventions. Chronic recurrent lung infections, pancreatic exocrine insufficiency, and elevated sweat chloride levels are hallmarks of the disease. Survival of patients with cystic fibrosis is steadily improving and most patients survive into adulthood. As lung disease progresses, secondary pulmonary hypertension and cor pulmonale are likely to develop. Pulmonary hypertension is correlated with the degree of hypoxemia and may be associated with increased mortality. The goal of therapy of cor pulmonale in cystic fibrosis is to correct hypoxemia and lower the elevated pulmonary artery pressures. This is best achieved by supplemental oxygen and aggressive treatment of the pulmonary disease with antibiotics and airway clearance techniques. It is also important to assess oxygenation during sleep and exercise. Bilateral lung transplantation is a treatment option for patients with end-stage lung disease, even in the presence of cor pulmonale.

The correlation between obstructive sleep apnea and low gonadotropin secretion in men

OSA patients and controls were of similar age, although body mass index (BMI) was slightly greater in patients (30.6 versus 26.3 kg/m, P 1⁄4 0:1). Four OSA patients had low 07:00 h total testosterone concentrations. All participants had the expected rise in testosterone overnight, but mean and area under the curve (AUC) total testosterone concentrations were significantly lower in the OSA patients. Similarly, mean and AUC LH were reduced in OSA patients versus controls. After adjusting for BMI, the mean LH and total testosterone differences between groups were of marginal statistical significance, although AUC remained different between the groups. RDI was significantly negatively correlated with LH-AUC and total testosterone-AUC, whereas degree of hypoxemia did not correlate.

The Use of Transesophageal Echocardiography to Facilitate Removal of a Thoracic Nail

The Use of Transesophageal Echocardiography to Facilitate Removal of a Thoracic Nail

What Are Obstructive Sleep Apnea Patients Being Treated for Prior to This Diagnosis?

Patients with obstructive sleep apnea syndrome (OSAS) use health-care resources at higher rates than control subjects for years prior to diagnosis. Although obesity and certain cardiovascular disorders are more common in OSAS patients, the precise cause of increased health-care utilization is unclear. To examine the causes of increased utilization, and what patients with OSAS were being treated for prior to this diagnosis. We compared the records of 773 patients with OSAS to those of age-, gender-, geographic-, and physician-matched control subjects from the general population. We found that sleep apnea patients used 23 to 50% more resources (defined by physician fees, physician visits, and hospital nights) in the 5 years prior to diagnosis than did control subjects. We examined the diagnoses made and found that apnea patients are at higher risk for hypertension (odds ratio [OR], 2.5; 95% confidence interval [CI], 2.0 to 3.3), congestive heart failure (OR, 3.9; 95% CI, 1.7 to 8.9), cardiac arrhythmias (OR, 2.2; 95% CI, 1.2 to 4.0), cardiovascular disease (OR, 2.6; 95% CI, 2.0 to 3.3), chronic obstructive airways disease (OR, 1.6; 95% CI, 1.2 to 2.0), and depression (OR, 1.4; 95% CI, 1.0 to 1.9). To control for the confounding effects of obesity and to determine the independent effects of body mass index (BMI), gender, age, degree of hypoxemia, apnea-hypopnea index, and sleepiness in the 773 patients, we performed a logistic regression analysis with the dependent variable being diagnosis, and a linear regression analysis with the dependent variable being measures of health-care utilization. Age and BMI were significant independent predictors of most cardiovascular diagnoses and arthropathy. Male gender predicted ischemic heart disease (OR, 2.98; 95% CI, 1.36 to 6.54), and female gender was predictive of chronic obstructive airways disease (OR, 2.63; 95% CI, 1.85 to 3.72) and depression (OR, 2.24; 95% CI, 1.45 to 3.44). The best model predicting health-care utilization measures was comprised of age, gender, and BMI, and explained 9%, 14%, and 8% of the variability in physician fees, number of physician claims, and number of physician visits, respectively. Of all comorbid diagnoses, significantly increased utilization was found for cardiovascular disease and especially hypertension in the OSAS patients.

Sedation, Risk, and Safety: Do We Really Have Data at Last?

The July 2001 issue of Pediatrics contained a commentary by Freeman entitled “The Risk of Sedation for Electroencephalograms: Data at Last.”1 This commentary, written to accompany a paper by Olson et al,2 made several statements based on erroneous statistical inference. We are grateful to the editors of Pediatrics for granting us this forum in which to respond to that commentary. The great importance of safety for children who need sedation is clearly reflected in past publications of this journal, most notably the American Academy of Pediatrics (AAP) “Guidelines for Monitoring and Management of Pediatric Patients During and After Sedation for Diagnostic and Therapeutic Procedures.”3 We, as did Dr Freeman, commend Olson and colleagues for demonstrating that sedation for electroencephalograms (EEGs) in children is usually not necessary when effective behavioral techniques are employed. Nevertheless, there are occasions when behavioral techniques are inadequate, as demonstrated by the 513 patients (18% of the total in this series) who received sedation with chloral hydrate and other drugs. Three of these patients developed oxygen desaturation to between 82% and 88%. This corresponds to a Pao2 of about 45 to 55, a significant degree of hypoxemia. Although transient hypoxemia is unlikely to lead to long-term consequences, unrecognized or inadequately treated hypoxemia, especially when related to airway obstruction, may progress to more severe complications. It is to the investigators' credit that their compliance with the AAP guidelines for monitoring during sedation resulted in prompt recognition and treatment of the airway problems without sequelae. This ability to rescue from complications is strongly emphasized in the 2001 standards of the Joint Commission on Accreditation of …

High Altitude Medicine: Impacts for Anesthesia?

Until recently altitudes above 4000 m were mostly visited by trained and experienced mountaineers, today these altitudes are open to anybody thanks to increased wealth, leisure time and mobility as well as to commercial trekking and mountaineering agencies. Therefore, practitioners are increasingly confronted with questions concerning high altitude tolerance. Often such questions are asked by individuals that have no prior mountaineering experience, have never been to high altitudes and may even be under treatment for chronic diseases. Therefore, knowledge about the physiology of acclimatization to high altitude, about high altitude illnesses as well as high altitude tolerance of patients with cardio-pulmonary disease is particularly important for those doctors who are asked for advice by people who intend to go to high altitude as well as for those doctors who accompany trekkings or expeditions. This mini-symposium demonstrates that we have quite a good knowledge, based on scientific data, about the physiology of acclimatization to hypoxia, while our understanding of the pathophysiology of high altitude illnesses is still rather speculative, although considerable progress has been achieved recently regarding the pathogenesis of high altitude pulmonary edema. Unfortunately, there are almost no controlled studies that investigate possibilities of assessment of tolerance to high altitude in healthy individuals or patients. Is research in high altitude medicine of any relevance for anesthesiology or intensive care medicine? At first glance there appears to be a big contrast : In anesthesia and intensive care medicine one tries with all means of the art to avoid blood gases, to which mountaineers or trekkers expose themselves voluntarily. A mountaineer who ascends rapidly to the Margherita Hut (4559 m) will have an arterial PO2 of about 40 mmHg and an arterial oxygen saturation between 70 and 80 % on the day of arrival. Except for a reduced performance, this level of hypoxemia does not have negative effects regarding well-being and health in those 50 % of the mountaineers who can tolerate such a rapid exposure without developing acute mountain sickness or high altitude pulmonary edema [1]. Equally impressive is the potential of adaptation of healthy humans to hypoxia. A pilot candidate of the Air Force who has to participate in an educational „demonstration on the effects of lack of oxygen” during which he is exposed rapidly to a simulated altitude of 8800 m will pass out within 10-15 minutes, if the doctor running the experiment does not give him the oxygen mask in time [2]. On the contrary, a mountaineer who ascends slowly over 6-8 weeks to the same altitude on Mount Everest is able to perform about 100 Watt at this altitude and will tolerate the following arterial blood gases : PO2 = 28 mmHg, PCO2 = 10 mmHg and SaO2 = 50 %, pH = 7,52 (at rest 7,56) [3]. Even during such maximal exercise in extreme hypoxia, one does not find arrhythmias or sign or ischemia in the ECG [4], while subtle cerebral dysfunctions occur (in most cases transiently) in some individuals [5]. The discrepancy between high altitude medicine and anesthesia will disappear when looking at it from a different point of view. The blood gas values reported from high altitude show which degree of hypoxemia can be tolerated without apparent damage by healthy individuals during acute and chronic exposure to hypoxia. Perhaps, one should keep in mind these blood gas values of healthy individuals at altitudes of 4500 m when balancing over the narrow ridge between oxygen toxicity and hypoxemia in anesthesiology and intensive care medicine.

Acid-base status and blood gas arterial values in free-ranging sika deer hinds immobilized with medetomidine and ketamine.

Ten free-ranging female sika deer (Cervus nippon) were captured to obtain the reference values for acid-base status and blood gas when immobilized with the combination of medetomidine and ketamine. The mean +/- SE of PaCO2, PaO2, and HCO3- were 58.1 +/- 6.1 mmHg, 58.8 +/- 6.4 mmHg, and 36.0 +/- 4.4 mmol/l, respectively. Although acidosis and alkalosis occurred in three and two animals, respectively, no serious conditions were observed. The blood values, however, suggest that some degree of hypoxemia and respiratory acidosis with metabolic alkalosis are developed. The trapped deer showed a significantly higher than normal rectal temperature reflective of exertion.