Higher Oxygen Saturation Research Articles

Detecting natural selection in high-altitude human populations

High-altitude natives have distinctive biological characteristics that appear to offset the stress of hypoxia. Evolutionary theory reasons that they reflect genetic adaptations resulting from natural selection on traits with heritable variation. Furthermore, high-altitude natives of the Andean and Tibetan Plateaus differ from one another, perhaps resulting from different evolutionary histories. Three approaches have developed a case for the possibility of population genetic differences: comparing means of classical physiological traits measured in samples of natives and migrants between altitudes, estimating genetic variance using statistical genetics techniques, and comparing features of species with different evolutionary histories. Tibetans have an inferred autosomal dominant major gene for high oxygen saturation that is associated with higher offspring survival, a strong indicator of ongoing natural selection. New approaches use candidate gene and genomic analyses. Conclusive evidence about population genetic differences and associations with phenotypes remains to be discovered.

Two routes to functional adaptation: Tibetan and Andean high-altitude natives

Populations native to the Tibetan and Andean Plateaus are descended from colonizers who arrived perhaps 25,000 and 11,000 years ago, respectively. Both have been exposed to the opportunity for natural selection for traits that offset the unavoidable environmental stress of severe lifelong high-altitude hypoxia. This paper presents evidence that Tibetan and Andean high-altitude natives have adapted differently, as indicated by large quantitative differences in numerous physiological traits comprising the oxygen delivery process. These findings suggest the hypothesis that evolutionary processes have tinkered differently on the two founding populations and their descendents, with the result that the two followed different routes to the same functional outcome of successful oxygen delivery, long-term persistence and high function. Assessed on the basis of basal and maximal oxygen consumption, both populations avail themselves of essentially the full range of oxygen-using metabolism as populations at sea level, in contrast with the curtailed range available to visitors at high altitudes. Efforts to identify the genetic bases of these traits have included quantitative genetics, genetic admixture, and candidate gene approaches. These reveal generally more genetic variance in the Tibetan population and more potential for natural selection. There is evidence that natural selection is ongoing in the Tibetan population, where women estimated to have genotypes for high oxygen saturation of hemoglobin (and less physiological stress) have higher offspring survival. Identifying the genetic bases of these traits is crucial to discovering the steps along the Tibetan and Andean routes to functional adaptation.

Amyloid-beta peptide affects the oxygen dependence of erythrocyte metabolism: A role for caspase 3

Human erythrocyte metabolism is modulated by the cell oxygenation state. Among other mechanisms, competition of deoxyhemoglobin and some glycolytic enzymes for the cytoplasmic domain of band 3 is probably involved in modulation. This metabolic modulation is connected to variations in intracellular NADPH and ATP levels as a function of the oxygenation state of the cell, and, consequently, it should have physiologic relevance. The present study investigates the effect of amyloid-beta peptide exposure on this metabolic modulation and its relationship with the activity of erythrocyte caspase 3. Metabolic differences between erythrocytes incubated at high and low oxygen saturation disappear following to 24h exposure to amyloid-beta peptide. Western blotting analysis shows that caspase 3 is concurrently activated. Pre-incubation of amyloid-beta peptide-treated erythrocytes with a specific inhibitor of caspase 3, partially restores the oxygen-dependent modulation. This finding suggests that human erythrocytes following to exposure to amyloid-beta peptide show a complete loss of the oxygen-dependent metabolic modulation, which is partially restored by caspase 3 inhibitor-treatment.

Hypereutrophication in Ngau Mei Hoi Bay, Hong Kong

Abstract Investigations into eutrophication of Ngau Mei Hoi Bay, Hong Kong, were carried out in July and December 1996. The results show that Ngau Mei Hoi Bay can be classified as hypereutrophic. During summer phytoplankton blooms (average chlorophyll a = 33.96 μg L−1), high oxygen saturation (up to 145.3%), high pH (7.8–8.4), and nutrient depletion (mean NO3+NO2 = 0.89 μg L−1) at the surface in association with hypoxic (dissolved oxygen concentration was down to 0.9 mg L−1), low pH (down to 4.9), and high nutrient (mean NO3+NO2 = 96.28 μg L−1) conditions at the bottom layer were observed. This typical phenomenon of eutrophication resulted from nutrient enrichment by anthropogenic activities, water column stratification formed by spreading of the Pearl River plume at the surface, and outer shelf water intrusion at the bottom. The perniciousness of the hypereutrophication and future monitoring needs for environmental management are also discussed.

More on NRP

The 2005 Consensus on Science and Treatment Recommendations of the International Liaison Committee on Resuscitation (ILCOR) serves as the scientific basis for neonatal resuscitation. This consensus reflects the world’s published medical literature and the various perspectives of the representatives to ILCOR from North and South America, Europe, Africa, Australia, and New Zealand. Guidelines reflect not only the science, but also the regional differences in equipment and health priorities. Accordingly, guidelines for the United States may differ in some respects from those of Great Britain or South Africa. The United States guidelines serve as the foundation for the Neonatal Resuscitation Program (NRP) educational program. What are the implications of the new consensus, guidelines, and educational program at the most local level – that of the hospitals and the professionals providing perinatal services? How should the changes be implemented in everyday practice? The 2005 guidelines incorporate several major changes in approach that mean not only behavioral changes, but also new equipment. New educational tools and areas of emphasis in the NRP offer opportunities and challenges to both instructors and providers of neonatal resuscitation. Clearly, the most sweeping change in the 2005 guidelines is the possibility of providing positive-pressure ventilation with oxygen concentrations less than 100% during initial resuscitation. This alters the conduct of resuscitation from the immediate rapid assessment performed in the first several seconds after birth. No longer is the question “Is the baby pink?” asked simultaneously with “Is the amniotic fluid clear?”, “Is the baby breathing or crying?”, “Is there good muscle tone?”, and “Is the baby term?”. Instead, the first 10 to 15 minutes …

Growth and correlates of nutritional status among infants with hypoplastic left heart syndrome (HLHS) after stage 1 Norwood procedure

Background Protein-energy malnutrition is common among infants with congenital heart disease. We hypothesized that infants with hypoplastic left heart syndrome (HLHS) are at risk for malnutrition. Objective To determine the prevalence of and risk factors for malnutrition in infants undergoing palliative surgery for HLHS. Methods Retrospective chart review of 50 infants with HLHS who underwent both stage 1 Norwood and bidirectional Glenn (BDG) procedures over 4.5 y. Results After a median hospital stay of 21 d, median discharge weight was 3.4 kg, unchanged from admission. Adjusting for weight on admission, children with longer length of hospital stay, longer intensive care unit stay, shorter duration of parental nutrition therapy, and higher diuretic dosage at discharge had a lower weight-for-age Z score at discharge ( R 2 = 0.85). On admission for BDG, median weight-for-age Z score was −2.0. After adjusting for weight on discharge from the initial hospitalization, children with fewer calories/ounce of their enteral nutrition at discharge, worse right ventricular function, more frequent readmissions, and higher oxygen saturation at discharge had a lower weight-for-age Z score at BDG ( R 2 = 0.49). Conclusions Malnutrition is common in infants with HLHS after stage 1 palliation. Variables associated with more complex postoperative course and imbalance between systemic and pulmonary blood flow were all associated with poorer nutritional status. When adjusting for these factors, the use of parenteral nutrition and high calorie enteral feeds were associated with improved nutritional status. Aggressive parenteral and enteral nutritional therapy might help reduce the prevalence of growth faltering in infants who have HLHS.

Venous oxygen saturation during normovolaemic haemodilution in the pig

Hypovolaemia may be considered to represent a volume-restricted cardiac output (CO), but CO varies inversely with the haemoglobin concentration (Hb) and a maximal mixed venous oxygen saturation (SvO2) may be a better target for volume administration than a maximal CO. In 10 anaesthetized pigs, volume loading with 6% hydroxyethyl starch was performed to obtain a maximal SvO2 followed by normovolaemic haemodilution with 6% hydroxyethyl starch. Volume loading increased SvO2 from 55.0+/-5.2% to 64.8+/-9.0% (mean+/-SD) associated with an increase in CO (2.3+/-0.4 to 3.5+/-0.9 l/min) and central venous oxygen saturation (ScvO2; 68.2+/-9.3% to 79.4+/-7.2%; P<0.05). Heart rate (HR), mean arterial (MAP), central venous (CVP), pulmonary arterial mean (PAMP), and occlusion pressures (PAOP) increased as well (P<0.05). In contrast, during progressive haemodilution, SvO2 and ScvO2 remained statistically unchanged until the haemoglobin concentration had decreased from 5.5+/-0.4 to 2.9+/-0.2 mM, while CO and HR increased at a haemoglobin value of 4.4+/-0.4 and 4.0+/-0.4 mM and CVP and PAOP decreased at a haemoglobin of 4.0+/-0.4 and 2.9+/-0.2 mM, respectively (P<0.05) leaving MAP unaffected. This study found that volume loading increased cardiac output and mixed and central venous oxygen saturations in parallel, but during normovolaemic haemodilution an increase in cardiac output left mixed and central venous oxygen saturations statistically unchanged until haemoglobin concentration was reduced by approximately 50%. Accordingly, volume therapy should be directed to maintain a high venous oxygen saturation rather than a change in cardiac output.

Die Zuverlässigkeit der fetalen Pulsoxymetrie bei der Detektion einer fetalen Azidose

Fetal pulse oximetry is a continuous method to exclude the lack of oxygen in cases of non-reassuring fetal heart rate. This study aims at the evaluation of the predictive value of this method concerning the development of fetal acidosis. 136 fetuses with non-reassuring heart rate were monitored by fetal pulse oximetry. In all cases fetal blood pH and base excess were determined repeatedly by fetal blood analysis (FBA). The pH value and base excess in the umbilical artery and scalp blood as well as the changes of pH and base excess were correlated to the duration of low, medium and high fetal oxygen saturation (FSpO (2)). Sensitivity, specificity, positive and negative predictive values were calculated for the assumption that "FSpO (2) < or = 30 % for at least 10 or 15 minutes" predicts a pH or base excess in the umbilical artery and in FBA of < 7.1/7.15/7.2 or < or = -4/8/12 mmol/L and a decline of pH (base excess) by more than 0.05 (0.1) pH units (4 mmol/L). A highly significant negative correlation was found between umbilical artery and FBA pH and base excess as well as the change of both and the duration of low oxygen saturation. Additionally the change of FBA pH depends on the duration of medium FSpO (2). A pH below 7.15 in FBA as well as base excess < or = -12 mmol/L were safely detected by a cut-off of "FSpO (2) < or = 30 % for at least 10 minutes" and pH < 7.1 and base excess < or = -12 mmol/l in FBA in 100 % and 75 %, respectively. A decline of pH by more than 0.1 pH units and of base excess by more than 4 mmol/L were excluded by a negative predictive value of 98 %. In conclusion, medium and progressive acidosis can be reliably excluded by fetal pulse oximetry.

Qualidade da água em pesque-pague da região metropolitana de São Paulo (Brasil): avaliação através de fatores abióticos (período seco e chuvoso)

The water quality of 30 sports fishing in São Paulo (Brazil) metropolitan area was evaluated under abiotic variables during dry and rainy periods of September 2000 and February 2002. Alkalinity varied between 10.5 and 95.0 CaCO3/L; the conductivity varied between 10.2 and 390.0 μS/cm; the pH between 5.80 and 8.10. Dissolved oxygen varied between 5.20 and 12.40 mg/L; turbidity between 11 and 270 NTU; water temperature 18 and 27°C. The STS varied between 12 and 140 mg/L and the water transparency between 0.10 and 0.60. The results were in accordance with National Environmental Council (Conama) Resolution (1986) for class 2. However, high electrical conductivity and oxygen saturation showed high level of organic matter which leads to deterioration of water quality. There were no significant differences (P > 0.05) between the variables and the dry and rainy periods, which suggests a higher influence of the management on the analyzed systems than on the climatic variations

Timing of Chest Tube Removal After Coronary Artery Bypass Surgery

Assessing the impact of chest tube removal timing following a coronary artery bypass grafting surgery on the clinical outcome. Eighty-three consecutive patients were randomly assigned to either have the chest tube removed 24 hours (Group A) or 48 hours (Group B) postoperatively. Chest tubes were removed on the condition that drainage was less than 100 cc for the last 8 hours. Pre- and postoperative data were analyzed. The following preoperative and intraoperative risk factors were more prevalent among Group A patients: previous MI (60.5% vs 40.7%, p = 0.11), previous CVA (9.1% vs 0%, p = 0.11), hypertension (72.7% vs 55.6%, p = 0.14), pump time (111.6 min vs 96.8 min, p = 0.07), and cross-clamp time (73.8 min vs 64.4 min, p = 0.07). Postoperatively, there was a lower demand for analgesics in Group A (2.1 times for 12 hours at 36 hours vs 3.6 p = 0.09), lower white blood cell count (10,947 at 48 hours vs 11,576, p = 0.39) a higher oxygen saturation (91.9% at 48 hours vs 88.9%, p = 0.07), higher expiratory volumes (594 mL at 36 hours vs 514 mL p = 0.08) and earlier mobilization (23% walking at 48 hours vs 4%, p = 0.01). Pleural effusion and atelectasis were less frequent in Group A in both chest X-rays (66% vs 73%, p = 0.6 and 64% vs 75%, p = 0.47, respectively) and CT scans (19% vs 41%, p = 0.1 and 84% vs 96%, p = 0.42, respectively). There was no difference between the two groups in the prevalence of serous wound discharge and the length of hospital stay and there were no reported cases of pneumonia throughout the study. In cases where no excessive drainage accumulates, early removal of the chest tubes was found to be a policy that improves the postoperative outcome and decreases the need for supportive treatment such as analgetics, physiotherapy, nurse care, and oxygen. This policy did not involve significant residual effusions.

Oxygénothérapie du nouveau-né : matériels de surveillance non invasive

In newborn and premature infants whose lung immaturity entails a limited capacity for O2 detoxification, the use of supplemental oxygen should be continuously and non-invasively monitored. Pulse oximetry and transcutaneous O2 monitoring are the systems most used in the NICU. Major limitations of pulse oximetry are motion artifact, sensitivity to excessive light, cutaneous hypoperfusion, hypothermia, venous congestion, arterio-venous shunting, strong skin pigmentation, anemia and high percentage of abnormal hemoglobin. Alarm habituation is a further major risk. New oxymeters show less motion, artifact and higher accuracy during low oxygen saturation. The accuracy during high oxygen saturation is very dependent on the specific oxymeter model used. Transcutaneous O2 monitoring is usually combined with transcutaneous PCO2 monitoring, hence enabling evaluation of oxygenation as well as ventilation. A major risk of this method is related to the heated electrode sensor, which can induce skin burns. A combined ear sensor for pulse oximetry and PCO2 monitoring seems promising.

Feasibility of kangaroo mother care in Mumbai

The purpose of this study was to determine the feasibility and acceptability of kangaroo care in a tertiary care hospital in India. A randomized controlled trial was performed over one year period in which 89 neonates were randomized into two groups kangaroo mother care (KMC) and conventional method of care (CMC). Forty-four babies were randomized into KMC group and 45 to CMC. There was significant reduction in KMC vs CMC group of hypothermia (10/44 vs 21/45, p-value < 0.01), higher oxygen saturations (95.7 vs 94.8%, p-value < 0.01) and decrease in respiratory rates (36.2 vs 40.7, p-value < 0.01). There were no statistically significant differences in the incidence of hyperthermia, sepsis, apnea, onset of breastfeeding and hospital stay in two groups. 79% of mothers felt comfortable during the KMC and 73% felt they would be able to give KMC at home. KMC is feasible, as mothers are already admitted in hospitals and are involved in the care of newborn. KMC is a simple and feasible intervention; acceptable to most mothers admitted in hospitals. There may be benefits in terms of reducing the incidence of hypothermia with no adverse effects of KMC demonstrated in the study. The present study has important implications in the care of LBW infants in the developing countries, where expensive facilities for conventional care may not be available at all place.

Emergence and Recovery Characteristics of Desflurane Versus Sevoflurane in Morbidly Obese Adult Surgical Patients: A Prospective, Randomized Study

We compared postoperative recovery after desflurane (n = 25) versus sevoflurane (n = 25) anesthesia in morbidly obese adults (body mass index >/=35) who underwent gastrointestinal bypass surgery via an open laparotomy. After premedication with midazolam and metoclopramide 1 h before surgery, epidural catheter placement, induction of anesthesia with fentanyl and propofol, and tracheal intubation facilitated with succinylcholine, anesthesia was maintained with age-adjusted 1 minimum alveolar concentration (MAC) desflurane or sevoflurane. Fentanyl IV, morphine or local anesthetics epidurally, and vasoactive drugs as needed were used to maintain arterial blood pressure at +/-20% of baseline value and to keep bispectral index of the electroencephalogram values between 40 to 60 U. Although patients were anesthetized with desflurane for a longer time (261 +/- 50 min versus 234 +/- 37 min, mean +/- sd; P < 0.05, desflurane versus sevoflurane, respectively) and for more MAC-hours (4.2 +/- 0.9 h versus 3.7 +/- 0.8 h; P < 0.05), significantly earlier recovery of response to command and tracheal extubation occurred in patients given desflurane than in patients given sevoflurane. The modified Aldrete score was greater in desflurane-anesthetized patients on admission to the postanesthesia care unit (PACU) (P = 0.01) but not at discharge (P = 0.47). On admission to PACU, patients given desflurane had higher oxygen saturations (97.0% +/- 2.4%) than patients given sevoflurane (94.8% +/- 4.4%, P = 0.035). Overall, the incidence of postoperative nausea and vomiting and the use of antiemetics did not differ between the two anesthetic groups. We conclude that morbidly obese adult patients who underwent major abdominal surgery in a prospective, randomized study awoke significantly faster after desflurane than after sevoflurane anesthesia and the patients anesthetized with desflurane had higher oxygen saturation on entry to the PACU.

Historical Perspectives

When pharmacologic closure of patent ductus arteriosus (PDA) in the preterm infant using indomethacin was introduced in 1976, there was a paucity of knowledge about the factors controlling the caliber of the ductus arteriosus both before and after birth. Additionally, mortality and morbidity of prematurity (associated with what was then usually referred to as hyaline membrane disease) was remarkably high in the early 1970s. As early as the 1950s, some neonatologists recognized PDA as a complication of what later became designated as “respiratory distress syndrome” (RDS), although it was not until the advent of intermittent mandatory ventilation (IMV) and continuous positive airway pressure (CPAP) that the concept gained prominence. Patency of the ductus appeared to be a major complication, especially in the smallest of preterm babies (at that time, < 1,350 g]) and usually carried a terminal prognosis. The advent of IMV and CPAP kept these small babies alive for a sufficient period of time for the patent ductus to become recognized progressively as a distinct clinical entity and an important early complication of preterm birth. Observant neonatologists noted that babies who had RDS often improved up to a point, beyond which they worsened. The usual story was that the baby experienced ventilatory failure, was treated with mechanical ventilation, and began to improve, with lower inspired oxygen requirements. After a few days, when discussions ensued about taking the baby off the ventilator, the infant’s improvement would cease. The radiographic picture changed from a clearing of the initial ground glass appearance coupled with a relatively small heart to an enlarging heart and the pulmonary edema of congestive heart failure due to a left-to-right shunt across the PDA. Beginning in the mid-1960s, aggressive surgeons advocated operative closure of the PDA in these small preterm infants, but multiple centers consistently reported unacceptably high …

Preterm infants' behavioural indicators of oxygen decline during bottle feeding.

During the time when preterm infants' oral feeding skills are developing they often experience physiological instability and need assistance from caregivers to maintain adequate oxygenation. Assisting infants to maintain optimal oxygenation during oral feeding requires an understanding of how they express and aim to self-regulate their oxygen status. The purpose of this study was to identify potential behavioural indicators of declining oxygenation during preterm infant early bottle-feeding. The design was explorative. Data were collected from a secondary analysis of 20 videotapes of preterm infant bottle feedings which included concurrent oxygen saturation data. In this analysis infant behaviours and quality of breathing were coded and compared across three periods: high oxygen saturation, immediately preceding an oxygen desaturation event, and during an oxygen desaturation event. Infants gave limited behavioural indicators of declining oxygenation. Immediately prior to a desaturation event, they had an increase in eye flutter and were typically sucking and apnoeic. During a desaturation event, they typically relaxed their arms/hands and stopped sucking. Reliance on preterm infant behavioural cues will be insufficient for detection of oxygen desaturation during oral feeding. Attention to changes in breath sounds and to the pattern of sucking are potentially important intervention strategies for the prevention of and appropriate response to oxygen decline during feeding. Sucking pauses may be a time when preterm infants aim to regulate their breathing pattern and thereby increase oxygenation. Interventions that focus on detection and minimization of apnoea during feeding, and which aim to protect infant sucking pauses, may reduce the number and severity of desaturation events preterm infants experience during bottle feeding.

The ratio of flow in the superior and inferior caval veins after construction of a bidirectional cavopulmonary anastomosis in children.

In patients who have undergone a superior cavopulmonary anastomosis, the superior caval venous flow provides the only, or the most important, pulmonary blood supply, while the inferior caval venous blood is not oxygenated, being mixed with the pulmonary venous blood before entering the systemic circulation. In healthy children, the contribution of superior caval venous flow to total cardiac output has been shown to decrease during growth. Patients who have undergone a superior cavopulmonary anastomosis, however, often have a higher oxygen saturation than predicted by the age-matched ratio of superior to inferior caval venous flows. This study was designed, therefore, to assess the ratio of flows in the superior and inferior caval veins subsequent to a superior cavopulmonary anastomosis. We carried out 18 magnetic resonance imaging studies with velocity-mapping and heart catheterisations so as to assess the contribution of superior caval venous flow to total cardiac output. Patients were divided into 3 groups according to their age. There were five aged from 8 to 24 months, eight aged from 24 to 48 months, and five older than 48 months. No significant difference could be found in the ratios of superior-to-inferior caval venous flow, nor of superior caval venous-to-systemic flow, between the 3 groups. The ratio of venous flows was 0.89 +/- 0.34 in those aged from 8 to 24 months, 1.09 +/- 0.42 in those from 24 to 48 months, and 1.25 +/- 0.27 in the older patients (F analysis of variance 1.06, p 0.37). The ratio of superior caval venous-to-systemic flow was 0.46 +/- 0.08 in the youngest patients, 0.50 +/- 0.09 in those aged from 24 to 48 months, and 0.55 +/- 0.05 in the older patients (F analysis of variance 0.76, p 0.49). These findings suggest that the hemodynamics of a cavopulmonary anastomosis may affect the normal decrease of superior caval venous flow with age. This could be related to a redistribution of flow, with a proportionally higher flow to the head and upper body after construction of a superior cavopulmonary anastomosis. Since increasing cyanosis and progressive exercise intolerance are the main indications for creation of a total cavopulmonary connection, these findings should be taken into account when determining the timing for completion of the Fontan circulation.

The Association of High Jugular Bulb Venous Oxygen Saturation with Cognitive Decline After Hypothermic Cardiopulmonary Bypass

The Association of High Jugular Bulb Venous Oxygen Saturation with Cognitive Decline After Hypothermic Cardiopulmonary Bypass

Respiratory adaptations in a deep-sea orbiniid polychaete from Gulf of Mexico brine pool NR-1: metabolic rates and hemoglobin structure/function relationships.

Methanoaricia dendrobranchiata Blake (Polychaeta; Orbiniidae) occurs in large numbers in association with communities of the mussel Bathymodiolus childressi at hydrocarbon seeps on the Louisiana Slope of the Gulf of Mexico. Its microhabitat can be strongly hypoxic (oxygen is often undetectable) and sulfidic (sulfide concentrations can reach millimolar levels), which may seriously challenge aerobic metabolism. We describe a suite of adaptations to its low-oxygen environment. The worms are capable of regulating their rate of oxygen consumption down to partial pressures of approximately 870 Pa oxygen. This capability correlates with a large gill surface area, a small diffusion distance from sea water to blood, a very high hemoglobin oxygen-affinity (P50=27.8 Pa at 10 degrees C and pH 7.6) and a Bohr effect that is pronounced at high oxygen saturations. When fully saturated, the hemoglobin binds sufficient oxygen for only 31 min of aerobic metabolism. However, these polychaetes can withstand extended periods of anoxia both in the absence and presence of 1 mmol l(-1) sulfide (TL50=approx. 5.5 and 4 days, respectively).

Bone: formation by autoinduction. 1965.

Bone: formation by autoinduction. 1965.

Hypercapnia Due to Unrecognized Recurarization with a High Oxygen Saturation on the Pulse Oximeter

Carbon dioxide narcosis can produce apnea and coma, even though blood oxygen remains high enough to sustain life. We reported an unusual case of hypercapnia due to unrecognized recurarization with a high oxygen saturation on the pulse oximeter. A 74 year-old woman was scheduled for a spinal fusion due to a fracture of the lumbar vertebrae. During more than an hour after surgery, the oxygen saturation on the pulse oximeter was 99 or 100%. Neostigmine was repeatedly required due to only one twitch of train-of-four (TOF) stimulation at that time. Despite a return of four twitchs of TOF stimulation, the patient's level of consciousness deteriorated as a result of hypercapnia (: 92.3 mmHg). Reventilation was required until this unusual carbon dioxide store had dissipated. We discuss the investigation, diagnosis and subsequent management of such an old patient and emphasize that the TOF stimulation was a reliable indicator of adequate recovery of neuromuscular function.