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C Keller

Publications and source records attributed to C Keller.

At least 73 records · Page 4Linked to original sources
PubMed2002

Augmented spontaneous breathing and pulmonary gas exchange during pneumoperitoneum.

BACKGROUND AND OBJECTIVE: Ventilation of the lungs with positive end-expiratory pressure during pneumoperitoneum has been shown to improve the arterial partial pressure of oxygen. The implications of spontaneous breathing on pulmonary gas exchange remain unknown in this setting. We therefore sought to examine the influence of pressure-support ventilation with spontaneous breathing on gas exchange during simulated laparoscopy. METHODS: Ten pigs were subjected to pneumoperitoneum at a pressure of 15 cmH2O. Animals received, in a random order, pressure-support and pressure-controlled ventilation for 60 min per mode. Inert gas and haemodynamic measurements were performed before changing to a subsequent mode. RESULTS: Pressure-support ventilation was more efficient than pressure-controlled ventilation regarding perfusion of normal V(A)/Q lung areas (78 +/- 4% vs. 72 +/- 5%) (P < 0.05), alveolar-arterial partial pressure of oxygen difference (9.73 +/- 1.3 vs. 11.2 +/- 1.2 kPa) and arterial partial pressure of oxygen (14.93 +/- 1.6 vs. 13.7 +/- 2.0 kPa) (P < 0.05). CONCLUSIONS: Pressure-support ventilation resulted in significantly better gas exchange than pressure-controlled ventilation in this model of simulated laparoscopy.

Animals↗
PubMed2002

Monitoring pollution by proton-transfer-reaction mass spectrometry during paediatric anaesthesia with positive pressure ventilation via the laryngeal mask airway or uncuffed tracheal tube.

Twenty children aged 2-66 months were randomly allocated for airway management with either the laryngeal mask airway or uncuffed tracheal tube using intermittent positive pressure ventilation with a tidal volume of 8 ml.kg-1 and a respiratory rate adjusted to maintain end-expiratory carbon dioxide concentration at 5.3 kPa. Induction was with fentanyl/propofol and maintenance was with sevoflurane 2.5% in oxygen/air. The airway device was removed when the patients were awake and the patients were transferred to the postanaesthesia care unit 10 min later. Air was sampled from a point 1.5 m above the floor at a location remote from the ventilation outlet and analysed using a proton-transfer-reaction mass spectrometer capable of continuous trace gas analysis at the parts per billion volume (ppbv) level. The concentration of sevoflurane was recorded every minute during three consecutive phases: for 5 min before the introduction of sevoflurane (background); after introduction of sevoflurane until removal of the airway device (intra-operative); and every minute after removal until the concentration returned to background levels. Median (interquartile range [range]) intra-operative sevoflurane concentrations were 200-400 times higher than background values for the laryngeal mask airway 1 (1-2 [0-3]) ppbv vs. 404 (278-523 [83-983]) ppbv, respectively, and the tracheal tube 2 (1-3 [0-5]) ppbv vs. 396 (204-589 [107-1735]) ppbv (both p < 0.0001), and returned to background values within 5 min of removal. There were no differences in sevoflurane concentration between devices intra-operatively or after removal. The performance of the proton-transfer-reaction mass spectrometer was identical at the start and end of the 30-day study. We conclude that peri-operative sevoflurane concentration in a modern operating theatre is similar for the laryngeal mask airway and the uncuffed tracheal tube in paediatric patients receiving intermittent positive pressure ventilation. Intra-operative sevoflurane concentrations are five times lower than occupational safety limit requirements, and 1000 times lower 5 min after removal of the airway device with the patient awake. The proton-transfer-reaction mass spectrometer has potential for monitoring air quality in the operating theatre.

Air Pollutants, Occupational↗
PubMed2002

Neopterin as a marker of immunostimulation: an investigation in anaesthetic workplaces.

Personnel working in operating theatres and recovery rooms are exposed to a variety of noxious substances. The results of studies of the effects of occupational exposure on immune parameters are conflicting. Neopterin is an acknowledged marker of immunostimulation. Urinary neopterin levels of 58 anaesthetists and anaesthetic nurses were measured over a 3-week period. Neopterin analyses were performed using high performance liquid chromatography. Neopterin levels were within the normal range for all subjects. Younger subjects (aged < or = 35 years) had significantly higher urinary neopterin concentrations than older subjects (aged > 35 years). The present study is the first to investigate the influence of anaesthetic exposure on neopterin levels. No evidence of immunostimulation was found.

Adult↗
PubMed2002

Reliability of epigastric auscultation to detect gastric insufflation.

BACKGROUND: We studied the reliability of epigastric auscultation to detect gastric insufflation in 30 anaesthetized, paralysed intubated patients. METHODS: A 16FG gastric tube was positioned with the tip in the mid-oesophagus with the proximal end attached to an injection port with a one-way valve. Four observers participated in the study. Observers were paired and each pair studied 15 patients. Each patient underwent four test sequences in random order, two by each observer. Each test sequence comprised one observer injecting different volumes of air (0.25 ml, 0.5 ml, 1 ml, 2 ml, 3 ml, 4 ml, 5 ml, 10 ml, 15 ml and 0 ml as a control) in random order whilst the second blinded observer listened with a stethoscope over the epigastrium. Each randomized volume was injected rapidly at 5 s intervals for 1 min. The number of injections required to detect air entering the stomach was recorded. The stomach was deflated between each test sequence. RESULTS: To detect air entering the stomach with 95% confidence, 11 injections were required for 0.25 ml; 7 for 0.5 ml; 3 for 1 ml; 2 for 2 ml and 3 ml, and I for > or =4 ml. The mean (range) inter- and intraobserver reliability was 0.73 (0.71-0.75) and 0.76 (0.76-0.89), respectively. The incidence of false positives was 21% (25/120) and the incidence of false negatives was 10% (103/1080), making the specificity and sensitivity 79% and 91%, respectively. CONCLUSIONS: We conclude that epigastric auscultation can detect gastric insufflation of 0.25 ml air after 11 breaths and > or = 4 ml air after one breath with 95% confidence. Inter- and intraobserver reliability is moderate to excellent. Epigastric auscultation should be repeated to reduce the risk of false positives.

Adolescent↗
PubMed2002

Mechanical closure of the vocal cords with the laryngeal mask airway ProSeal.

We report a case of mechanical closure of the vocal cords with the laryngeal mask airway ProSeal (PLMA) in an anaesthetized, paralysed 59-yr-old, 88 kg female undergoing lower-limb vascular surgery. Near-complete airway obstruction developed after a size-5 PLMA was inserted and the cuff inflated with 20 ml of air. Fibreoptic inspection revealed that the PLMA was correctly positioned, but the vocal cords were closed. Withdrawal of air from the cuff and/or moving the head and neck into the sniffing position resolved this problem.

Airway Obstruction↗
PubMed2002

The feasibility of transesophageal echocardiograph-guided right and left ventricular oximetry in hemodynamically stable patients undergoing coronary artery bypass grafting.

UNLABELLED: There are no techniques available for continuous noninvasive measurement of the oxygen saturation of blood flowing through the heart. We assessed the feasibility and accuracy of transesophageal echocardiograph (TEE)-guided left ventricular (SpO2 LV) and right ventricular (SpO2 RV) oximetry. Twenty hemodynamically stable, well-oxygenated anesthetized patients (ASA physical status III, aged 51-75 yr) undergoing coronary artery bypass grafting were studied. A TEE probe was modified by attaching a single-use pediatric reflectance pulse oximeter just proximal to the ultrasound transducer. The TEE probe was directed toward the LV by using the transgastric mid-short axis view or toward the RV by using the transgastric RV inflow view, in random order. Readings were taken every 30 s for 10 min during a hemodynamically stable period of anesthesia. Simultaneous blood samples were taken from the radial artery and pulmonary artery to determine arterial oxygen saturation (SaO2) and mixed venous oxygen saturation (SvO2), respectively. During SpO2 LV readings, simultaneous finger pulse oximetry (SpO2 finger) was also recorded. SpO2 LV was feasible in 20 of 20 patients, and SpO2 RV was feasible in 19 of 20 patients. The mean +/- SD (range) oxygen saturation for each method was the following: SpO2 LV, 98.7% +/- 0.6% (97%-100%); SaO2, 98.7% +/- 0.6% (96.6%-99.4%); SpO2 finger, 98.1% +/- 1.2% (97%-100%); SpO2 RV, 73.9% +/- 4.7% (64%-85%); and SvO2, 74.5% +/- 4.4% (66.8%-82.6%). SpO2 LV agreed closely with SaO2 (mean difference, 0.072%). SpO2 RV agreed closely with SvO2 (mean difference, 0.65%). SpO2 LV agreed more closely with SaO2 than finger oximetry (mean difference, -0.072 vs -0.692). TEE-guided SpO2 LV and SpO2 RV are feasible in hemodynamically stable anesthetized patients and provide similar readings to arterial and mixed venous blood samples. The technique merits further investigation. IMPLICATIONS: Transesophageal echocardiograph-guided left and right ventricular oximetry is feasible in hemodynamically stable anesthetized patients and provides similar readings to arterial and mixed venous blood samples.

Aged↗
PubMed2002

Gum-elastic bougie-guided insertion of the ProSeal laryngeal mask airway: a new technique.

We determined the success rates, cardiovascular responses and airway morbidity for gum-elastic bougie-guided insertion of the ProSeal laryngeal mask airway. One hundred anaesthetized, non-paralyzed adults (ASA 1-2 aged 18 to 80 years) were studied. The ProSeal LMA drainage tube was primed with a well-lubricated 16 French gauge gum-elastic bougie with the curved end proximal and the straight end protruding 30 cm beyond the drainage tube tip. The straight end of the gum-elastic bougie was inserted into the oesophagus under laryngoscopic guidance, the laryngoscope removed and the ProSeal LMA inserted using the standard insertion technique and the gum-elastic bougie as a guide. The following variables were recorded: ease of insertion, oropharyngeal leak pressure, ventilatory capability, ease of gastric tube insertion, blood staining on the bougie or LMA at removal, and postoperative airway morbidity. Haemodynamic data were recorded immediately pre-insertion and every minute for five minutes after insertion. Gum-elastic bougie and ProSeal LMA insertion was successful at the first attempt in all patients within 50 seconds. There were no significant increases in heart rate or blood pressure. Oropharyngeal leak pressure was 33 (17-40) cmH2O and ventilation was possible without leak in all patients at 9.5 ml x kg(-1) tidal volume. There were no drainage tube or gastric air leaks. Gastric tube insertion was successful at the first attempt in all patients. Blood staining at removal was not detected on the gum-elastic bougie, but was detected in 3% of ProSeal LMAs. The incidence of sore throat, dysphagia and dysarthria was 21%, 9% and 1% respectively. We conclude that gum-elastic bougie-guided insertion of the ProSeal LMA has a high success rate and is associated with minimal haemodynamic change and a low incidence of trauma.

Adolescent↗
PubMed2001

Transcriptional activation of the IL-6 gene in human contracting skeletal muscle: influence of muscle glycogen content.

In humans, the plasma interleukin 6 (IL-6) concentration increases dramatically during low-intensity exercise. Measurements across the working limb indicate that skeletal muscle is the source of IL-6 production. To determine whether energy availability influences the regulation of IL-6 expression during prolonged exercise, six male subjects completed two trials consisting of 180 min of two-legged dynamic knee extensor with either normal or low (~60% of control) pre-exercise muscle glycogen levels. Increases in plasma IL-6 during exercise were significantly higher (P<0.05) in the low-glycogen (16-fold) trial verses the control (10-fold) trial. Transcriptional activation of the IL-6 gene in skeletal muscle was also higher in the low-glycogen trial; it increased by about 40-fold after 90 min of exercise and about 60-fold after 180 min of exercise. Muscle IL-6 mRNA followed a similar but delayed pattern, increasing by more than 100-fold in the low-glycogen trial and by about 30-fold in the control trial. These data demonstrate that exercise activates transcription of the IL-6 gene in working skeletal muscle, a response that is dramatically enhanced when glycogen levels are low. These findings also support the hypothesis that IL-6 may be produced by contracting myofibers when glycogen levels become critically low as a means of signaling the liver to increase glucose production.

Exercise↗
PubMed2001

Matrix-dependent mechanism of neutrophil-mediated release and activation of matrix metalloproteinase 9 in myocardial ischemia/reperfusion.

BACKGROUND: A key component of reperfusion of myocardial infarction is an immediate inflammatory response, which enhances tissue repair. Matrix turnover is crucial to tissue repair, and matrix metalloproteinases (MMPs) are key enzymes involved in matrix degradation. The hypothesis tested is that one inflammation-based effector of tissue repair is the secretion and activation of MMP-9 by infiltrating neutrophils. METHODS AND RESULTS: Cardiac lymph and tissue were assayed for atent and active MMP-2 and MMP-9 by zymography and immunochemistry. Dual-labeling immunofluorescence determined the cellular source of MMP-9 protein. Isolated canine neutrophils were incubated with preischemic and postischemic cardiac lymph in the presence and absence of collagen-fibronectin pads, and the supernatants were assayed for latent and active MMP-9. MMP-9 increased during the first hours of reperfusion in both lymph supernatants and myocardial extracts, and this increase was of neutrophil origin. MMP-9 in the cardiac lymph remained latent but was activatable. In contrast, MMP-9 in the myocardium was in both latent and active forms. In situ zymography demonstrated that activated MMP-9 surrounded the infiltrated neutrophils. When postischemic cardiac lymph was incubated with neutrophils in vitro, MMP-9 secretion and activation occurred only in the presence of a collagen-fibronectin substrate; preischemic cardiac lymph did not induce significant secretion or activation. CONCLUSIONS: Infiltrating neutrophils are an early source of MMP-9 after reperfusion, and a portion of MMP-9 in the myocardium is active. Infiltrating neutrophils may localize MMP-9 activation by secreting MMP-9 and as a source of activating proteases.

Animals↗
PubMed2001

An ins(X;11)(q24;q23) fuses the MLL and the Septin 6/KIAA0128 gene in an infant with AML-M2.

The MLL (HRX, ALL-1 HTRX) gene at chromosome band 11q23 frequently is rearranged in acute lymphoblastic and myeloblastic leukemia. To date, more than 40 different 11q23 abnormalities have been described on the cytogenetic level, and at least 25 of the respective fusion partner genes are cloned. The vast majority of the respective reciprocal translocations generate a chimeric 5'-MLL/partner-3' gene on the derivative 11q23. In this work, we report a unique ins(X;11)(q24;q23) in an infant with acute myeloid leukemia (AML-M2) that fuses the human KIAA0128 gene at Xq24 with MLL. In contrast to the typical reciprocal MLL translocations, however, we provide evidence that the 5'-MLL/KIAA0128-3' fusion resides on Xq24 rather than on 11q23. The KIAA0128 gene encodes the human Septin 6 protein, which contains an ATP-GTP binding motif and three nuclear targeting sequences in its carboxy terminus. The maintenance of the reading frame of the 5'-MLL/KIAA0128-3' mRNA fusion allows for the formation of a novel chimeric protein. Septin 6 is the third member of the Septins that is fused to the MLL protein; the other two are hCDCrel at 22q11 and MSF at 17q25.

Chromosomes, Human, Pair 11↗
PubMed2001

Effects of two frequencies of walking on cardiovascular risk factor reduction in Mexican American women.

The beneficial effects of moderate-intensity exercise on cardiorespiratory fitness and body composition are well documented, with the greatest health benefits reported in sedentary individuals who engage in moderate levels of exercise. The published literature contains no quantification of the threshold of lower limits of beneficial exercise or estimates of benefits derived from lower exercise levels. The specific aim of this study was to compare the effects of two walking frequencies, holding intensity and duration constant, on blood lipids, body composition, and exercise maintenance regimens of Mexican American women. A quasi-experimental design, with two treatment groups and one comparison group, was used to explore the dose-response effects of low-intensity exercise on cardiovascular outcomes. Significant interactions were found between walking and total serum cholesterol and skin-fold sums. This study demonstrated the clinical efficacy of a low-intensity exercise regimen on cardiovascular risk factors and exercise adherence.

Adolescent↗
PubMed2001

Chromatin assembly during S phase: contributions from histone deposition, DNA replication and the cell division cycle.

During S phase of the eukaryotic cell division cycle, newly replicated DNA is rapidly assembled into chromatin. Newly synthesised histones form complexes with chromatin assembly factors, mediating their deposition onto nascent DNA and their assembly into nucleosomes. Chromatin assembly factor 1, CAF-1, is a specialised assembly factor that targets these histones to replicating DNA by association with the replication fork associated protein, proliferating cell nuclear antigen, PCNA. Nucleosomes are further organised into ordered arrays along the DNA by the activity of ATP-dependent chromatin assembly and spacing factors such as ATP-utilising chromatin assembly and remodelling factor ACE An additional level of controlling chromatin assembly pathways has become apparent by the observation of functional requirements for cyclin-dependent protein kinases, casein kinase II and protein phosphatases. In this review, we will discuss replication-associated histone deposition and nucleosome assembly pathways, and we will focus in particular on how nucleosome assembly is linked to DNA replication and how it may be regulated by the cell cycle control machinery.

Animals↗
PubMed2001

[Spontaneous versus controlled respiration with the laryngeal mask. A review].

Over the last 10 years, the Laryngeal Mask Airway (LMA) has gained widespread acceptance as a general purpose airway for routine anaesthesia. Published data from large studies and reports have confirmed the safety and efficacy of the device for spontaneous and controlled ventilation during routine use. The initial experience with the LMA should ideally be confined to short cases requiring the patient to remain spontaneously ventilating. With experience, it will be found that less anesthetic agent is required during anesthesia with the LMA and patient recovery should be improved as a result. Spontaneous breathing is the chosen mode of ventilation in approximately 60% of LMA uses in the UK. During spontaneous breathing a minimal inspiratory pressure support will help with higher endtidal carbon dioxide levels. The anaesthetist should be experienced with using the LMA in spontaneously ventilating patients before using it with positive pressure ventilation. Several large scale studies have failed to show any link between positive pressure ventilation and pulmonary aspiration or gastric insufflation. The main disadvantage of the LMA is that it does not protect against aspiration. From a practical point of view, most fasted patients with normal lung compliance may be mechanically ventilated through the LMA to airway pressures of approximately 20 cmH2O. The low pressure seal implies that tidal volumes should be approximately 6-8 ml*kg-1 and the inspiratory flow rates should be reduced to achieve adequate and safe ventilation.

Anesthesia, Inhalation↗
PubMed2001

Vaginal pessary-induced mechanical bowel obstruction.

We present a case of a mechanical bowel obstruction secondary to an impacted vaginal pessary. As the elderly segment of the population continues to grow, pessary use is increasing in absolute numbers, and clinicians must consider these medical devices when evaluating abdominal, gynecological, and urological complaints in elderly women.

Aged↗
PubMed2001

Reversing sevoflurane-associated Q-Tc prolongation by changing to propofol.

Congenital or acquired forms of the long Q-T syndrome may result in ventricular tachycardia known as torsade de pointes. Many drugs including volatile anaesthetics modify the Q-T interval. Sevoflurane is known to prolong of the rate-corrected Q-T interval (Q-Tc). The objective of this study was to determine whether the sevoflurane-associated Q-Tc prolongation is rapidly reversible when propofol is substituted for sevoflurane. Thirty-two female patients were allocated to two groups. All patients received sevoflurane induction and anaesthesia for 15 min. In one group, sevoflurane was then discontinued and anaesthesia maintained on propofol for another 15 min. The second group received sevoflurane anaesthesia for 30 min. Measurements were taken before, and 15, 20, 25 and 30 min after induction. Q-Tc prolongation was significantly reduced 5, 10 and 15 min after propofol had been substituted for sevoflurane. We conclude that the sevoflurane-associated Q-Tc prolongation is fully reversible within 15 min when propofol is substituted for sevoflurane.

Adult↗