mmHg PCO2 Research Articles

Effects of Carbon Dioxide and Temperature on the Oxygen-Hemoglobin Dissociation Curve of Human Blood: Implications for Avalanche Victims.

Completely avalanche-buried patients are frequently exposed to a combination of hypoxia and hypercapnia with a risk of normothermic cardiac arrest. Patients with a long burial time and an air pocket are exposed to a combination of hypoxia, hypercapnia, and hypothermia which may lead to the development of the “triple H syndrome”. This specific combination has several pathophysiological implications, particularly on the cardiovascular system and oxygen transport (oxygen supply and oxygen consumption). To examine the effects on hemoglobin oxygen affinity, we investigated venous blood samples from 15 female and 15 male healthy subjects. In a factorial design of four different carbon dioxide partial pressure (PCO2) levels (20, 40, 60, and 80 mmHg) and five different temperature levels (13.7°C, 23°C, 30°C, 37°C, and 42°C), 30 unbuffered whole blood samples were analyzed in a newly developed in vitro method for high-throughput oxygen dissociation curve (ODC) measurements. P50s, Hill coefficients, CO2-Bohr coefficients, and temperature coefficients were analyzed using a linear mixed model (LMM). Mean P50 at baseline (37°C, 40 mmHg PCO2) was 27.1 ± 2.6 mmHg. Both CO2-Bohr (p < 0.001) and temperature coefficients (p < 0.001) had a significant effect on P50. The absolute CO2 effect was still pronounced at normothermic and febrile temperatures, whereas at low temperatures, the relative CO2 effect (expressed by CO2-Bohr coefficient; p < 0.001, interaction) was increased. The larger impact of PCO2 on oxygen affinity at low temperature may be caused by the competition of 2,3-BPG with PCO2 and the exothermic binding characteristic of 2,3-BPG. In a model of an avalanche burial, based on published data of CO2 levels and cooling rates, we calculated the resulting P50 for this specific condition based on the here-reported PCO2 and temperature effect on ODC. Depending on the degree of hypercapnia and hypothermia, a potentially beneficial increase in hemoglobin oxygen affinity in the hypoxic condition might ensue.

Pnömosistis Jirovecii Enfeksiyonu Tanısı Alan Nefrotik Sendrom Olgusu

Pneumocystis jirovecii pneumonia (commonly called Pneumocystis pneumonia or PCP) is an opportunistic infection that occurs in immunocompromised individuals. 26 year-old male patient admitted to nephrology department for hypervolemic hyponatremia and consulted to our clinic because desaturation developed. He has been diagnosed with collapsing glomerulonephritis (GN) and he was using cyclosporine and prednisolone. Postero-anterior chest X-ray showed that; left cardiodiaphragmatic sinus was blunt. In the arterial blood gas, Ph:7,42 PO2:53 mmHg PCO2:35,4 mmHg, HCO3:23,6 mEql/L. The the alveolar arterial gradient was elevated (52,75). Antibiotic and because of hypervolemia diuretic therapy was recommended to the patient. After ten days the patient's hypoxia deepened.Repeated chest X-ray showed bilateral perihilar heterogeneous opacity. Flexible bronchoscopy was performed. Pneumocystis jirovecii was detected in lavage culture. The patient treated with Trimethoprim- Sulfamethoxazole (TMP-SMZ) (3 x 7.5 mg / kg) dose. Hypoxemia improved on the 7th day of treatment and the patient was discharged. TMP-SMZ treatment was completed in 21 days. Pneumocystis developing secondary to cyclosporin toxicity Jirovecii pneumonia is a rare case.

Abstract T P181: Static And Dynamic Cerebral Autoregulation Dissociate In Asymptomatic Carotid Artery Disease

Background: High grade internal carotid artery (ICA) disease can alter cerebral autoregulation and thus increase risk for ischemia. We aimed to differentiate two types of autoregulation - dynamic cerebral autoregulation (DCA), thought to be a homeostatic process, and vasomotor reactivity (VMR), which determines cerebrovascular reserve - in patients with asymptomatic ICA stenosis. Methods: Twenty-two patients (age 50-93, 16M) with unilateral 80-100% ICA occlusion but no stroke underwent quantitative CBF measurements using continuous arterial spin labeling (CASL) MRI. DCA was performed by continuous insonation of both middle cerebral arteries with transcranial Doppler for 10 minutes at depth 56mm using a standard head frame. Phase shift (PS) between spontaneous oscillations in blood pressure (measured with finger photoplethysmography (Finapres)) and MCA mean flow velocities (MFV) at frequencies .06-.12 Hz was calculated for each hemisphere using transfer function analysis. Lower degree of PS indicated worse autoregulation (abnormal &lt;24deg1). VMR was determined as a response to 2 minutes of 5% CO2 inhalation (abnormal &lt;2% rise in MCA MFV per mmHg PCO2 by Doppler-integrated inline capnometer (Spencer Technologies)). T-test Chi-square, and multivariable linear regression were used to look for associations between VMR, DCA, and hemispheral CBF (SPSS v.22). Results: MCA MFV (p&lt;.001), VMR (p=.002), and CBF (p&lt;.003), were lower in the ICA occlusion hemisphere. DCA difference approached significance (p=0.064). Controlling for age and anterior circle of Willis collateral cross-filling, DCA (p=0.024), but not VMR (p=0.079) on the occluded side was associated with greater hemispheral CBF asymmetry (F=6.87, p=0.024). VMR and DCA were not correlated (Fisher exact =.61). Conclusions: DCA but not VMR correlated with a low flow state produced by high grade ICA disease in asymptomatic patients. Our results suggest that in ICA stenosis dynamic/homeostatic mechanisms may be affected without substantially altering the static/protective mechanism of cerebrovascular reserve. Ongoing studies will investigate the effect of these two autoregulatory mechanisms on vascular cognitive impairment. 1 Ortega-Gutierrez S, et al. J Neuroimaging. 2014 24:379-86

Venoarterial PCO2 difference: a marker of postoperative cardiac output in children with congenital heart disease.

To determine the relationship between venoarterial carbon dioxide gradient (DeltapCO2) and central venous oxygen saturation (ScvO2) in children after cardiac surgery. A cohort study. The Paediatric cardiac intensive care unit of the Aga Khan University Hospital, Karachi, from June 2006 to May 2007. All children admitted in the paediatric cardiac intensive care after complete repair of congenital heart defect using cardiopulmonary bypass were included in the study. Simultaneous arterial and central venous blood gas samples were obtained from a catheter placed in the artery (either radial or femoral) and superior vena cava respectively. Linear regression analysis was performed between ScvO2 and DeltapCO2. Fifty seven children aged from 5 days to 14 years were included and 272-paired simultaneous arterial and central venous samples were analyzed. Mean venous pCO2 was 47.82+/-9.03 mmHg and mean arterial pCO2 was 40.50+/-9.06 mmHg. One hundred seventy four samples had ScvO2 > 70% with mean DeltapCO2 of 5.44+/-2.55 mmHg and 98 samples had ScvO2 < 70% with mean DeltapCO2 of 9.07+/-3.90 mmHg. With ScvO2 < 70%, 77 samples had DeltapCO2 of > 6 mmHg while only 21 samples had DeltapCO2 of < 6 mmHg (p < 0.001). On the contrary with ScvO2 > 70%, 71 samples had DeltapCO2 of > 6 mmHg and 103 samples had DeltapCO2 of < 6 mmHg. Coefficient of correlation (R2) between 0.340 was ScvO2 and DeltapCO2. Elevated DeltapCO2 is practical and can be utilized as a useful adjunct to low ScvO2 in the assessment of low cardiac output syndrome in children after cardiac surgery.

Transcranial Doppler sonography with evaluation of CO2 reactivity in craniocerebral trauma

17 patients with severe head injury were examined by transcranial Doppler sonography. Resting values and CO2 reactivity were determined. The resting measurements had no prognostic value. There was no significant side difference in patients with unilateral intracranial lesions. CO2 reactivity was 2.8 +/- 2.3%/mmHg pCO2 in patients with good outcome, whereas in patients with bad outcome CO2 reactivity was 0.6 +/- 5.1%/mmHg pCO2. However, in the acute situation after the trauma there was no difference between the two. In patients with a unilateral lesion we found a significantly lower CO2 reactivity on the side of the lesion of 1.8 +/- 0.4%/mmHg pCO2, on the non-affected side CO2 reactivity was 4.5 +/- 2.1%/mmHg pCO2. The conclusion is that the CO2 reactivity yields information on the actual haemodynamic situation in brain-injured patients. Repeated measurements are necessary to improve the prognostic value of CO2 reactivity, because this parameter may improve during treatment.

Small volume of hypertonic saline as the initial fluid replacement in experimental hypodynamic sepsis

IntroductionWe conducted the present study to examine the effects of hypertonic saline solution (7.5%) on cardiovascular function and splanchnic perfusion in experimental sepsis.MethodsAnesthetized and mechanically ventilated mongrel dogs received an intravenous infusion of live Escherichia coli over 30 minutes. After 30 minutes, they were randomized to receive lactated Ringer's solution 32 ml/kg (LR; n = 7) over 30 minutes or 7.5% hypertonic saline solution 4 ml/kg (HS; n = 8) over 5 minutes. They were observed without additional interventions for 120 minutes. Cardiac output (CO), mean arterial pressure (MAP), portal and renal blood flow (PBF and RBF, respectively), gastric partial pressure of CO2 (pCO2; gas tonometry), blood gases and lactate levels were assessed.ResultsE. coli infusion promoted significant reductions in CO, MAP, PBF and RBF (approximately 45%, 12%, 45% and 25%, respectively) accompanied by an increase in lactate levels and systemic and mesenteric oxygen extraction (sO2ER and mO2ER). Widening of venous-arterial (approximately 15 mmHg), portal-arterial (approximately 18 mmHg) and gastric mucosal-arterial (approximately 55 mmHg) pCO2 gradients were also observed. LR and HS infusion transiently improved systemic and regional blood flow. However, HS infusion was associated with a significant and sustained reduction of systemic (18 ± 2.6 versus 38 ± 5.9%) and mesenteric oxygen extraction (18.5 ± 1.9 versus 36.5 ± 5.4%), without worsening other perfusional markers.ConclusionA large volume of LR or a small volume of HS promoted similar transient hemodynamic benefits in this sepsis model. However, a single bolus of HS did promote sustained reduction of systemic and mesenteric oxygen extraction, suggesting that hypertonic saline solution could be used as a salutary intervention during fluid resuscitation in septic patients.

Effects of oxygen and carbon dioxide on human retinal circulation: an investigation using blue field simulation and scanning laser ophthalmoscopy

To investigate the quantitative response of retinal circulation in normal human eyes to oxygen and carbon dioxide provocation and to gain more information about retinal mean transit time (MTT). Healthy subjects were studied while breathing: room air (O(2) baseline); pure O(2); room air (CO(2) baseline), and CO(2) in room air. The CO(2) level was brought to 30% above individual baseline level. During each gas exposure, blue field simulation was used to estimate the velocity of macular leucocytes and fluorescein angiography was used to determine MTT, arteriovenous passage time (AVP) and vessel diameters. Breathing pure O(2) caused a reduction in macular leucocyte velocity of about 13%, a non-significant change in MTT and AVP from baseline, and a 10% reduction in the diameter of temporal retinal arteries and veins. Breathing CO(2) caused an increase in macular leucocyte velocity of 21%, a non-significant change in MTT and AVP, and no change in retinal vascular diameters. Both O(2) and CO(2) had the expected effects on retinal blood flow, as judged by leucocyte velocity in the macular capillaries, but little effect on retinal MTT, indicating concomitant changes in flow and retinal vascular volume. Measuring the diameter of retinal vessels before and during pure O(2) breathing is a simple and effective way of determining the reactivity of retinal vessels.

Changes in the Acid-Base Equilibrium of Pleural Fluid During the First 2 Hours After Thoracentesis

The aim of this study was to assess changes in the acid-base equilibrium of pleural fluid during the first 2 hours after thoracentesis and to determine whether, as with arterial blood, it is important to keep the fluid on ice. A prospective, descriptive, comparative study was performed in 53 consecutive patients with pleural effusion. Thoracentesis was performed and pleural fluid was collected in 5 heparinized syringes to determine the pH, PO2, and PCO2 at baseline and at 30, 60, 90, and 120 minutes. In the first 26 patients, pleural fluid was collected in a further 4 syringes that were kept on ice prior to performing the same measurements at 30, 60, 90, and 120 minutes. The patients had a mean (SD) age of 70 (14) years, 66% were smokers, 72% were men, 63% had right-sided pleural effusion, 85% had unilateral effusion, and 15% had massive effusion. In 10 patients the effusion was a transudate, in 35 it was lymphocytic, and in 8 it was neutrophilic. The etiology was benign in 34 cases and neoplastic in 19 cases. The baseline pH was 7.35 (0.1) and baseline values of PO2 and PCO2 were 57.8 (20) mm Hg and 53.7 (15) mm Hg, respectively. No significant changes were observed in the first 2 hours for either pH or PCO2, whereas PO2 did undergo a significant change over this period. The difference between the baseline value and the value obtained at 120 minutes was 0.005 (0.02) for pH, 12.5 (19) mm Hg for PO2, and 0.8 (3) mm Hg for PCO2, with correlation coefficients of 0.97, 0.49, and 0.98, respectively. Comparison of values by simple regression analysis did not reveal a significant difference in the changes in pH, PO2, or PCO2 associated with keeping samples on ice. Multivariate analysis revealed that neoplastic effusion and a higher red blood cell count in pleural fluid had a significant influence on pH changes. The pH and PCO2 of pleural fluid did not change significantly during the first 2 hours following thoracentesis, whereas PO2 did undergo a significant change. Keeping samples on ice during this period is unnecessary. Only a higher red blood cell count in pleural fluid and neoplastic effusion had a limited effect on changes in the pH of samples from our patients during the first 2 hours following thoracentesis.

Short-lasting systemic and regional benefits of early crystalloid infusion after intravenous inoculation of dogs with live Escherichia coli

We investigated the systemic and regional hemodynamic effects of early crystalloid infusion in an experimental model of septic shock induced by intravenous inoculation with live Escherichia coli. Anesthetized dogs received an intravenous infusion of 1.2 x 10(10) cfu/kg live E. coli in 30 min. After 30 min of observation, they were randomized to controls (no fluids; N = 7), or fluid resuscitation with lactated Ringer's solution, 16 ml/kg (N = 7) or 32 ml/kg (N = 7) over 30 min and followed for 120 min. Cardiac index, portal blood flow, mean arterial pressure, systemic and regional oxygen-derived variables, blood lactate, and gastric PCO2 were assessed. Rapid and progressive cardiovascular deterioration with reduction in cardiac output, mean arterial pressure and portal blood flow (approximately 50, approximately 25 and approximately 70%, respectively) was induced by the live bacteria challenge. Systemic and regional territories showed significant increases in oxygen extraction and in lactate levels. Significant increases in venous-arterial (approximately 9.6 mmHg), portal-arterial (approximately 12.1 mmHg) and gastric mucosal-arterial (approximately 18.4 mmHg) PCO2 gradients were also observed. Early fluid replacement, especially with 32 ml/kg volumes of crystalloids, promoted only partial and transient benefits such as increases of approximately 76% in cardiac index, of approximately 50% in portal vein blood flow and decreases in venous-arterial, portal-arterial, gastric mucosal-arterial PCO2 gradients (7.2 +/- 1.0, 7.2 +/- 1.3 and 9.7 +/- 2.5 mmHg, respectively). The fluid infusion promoted only modest and transient benefits, unable to restore the systemic and regional perfusional and metabolic changes in this hypodynamic septic shock model.

A fatal case of severe serotonin syndrome accompanied by moclobemide and paroxetine overdose

Aim: To present a fatal case of serotonin syndrome accompanied by moclobemide and paroxetine overdose. Case presentation: A 34-year-old married woman was presented following intentional ingestion of 3.5 g moclobemide and 2.6 g paroxetine. She was drowsy, agitated, and having rigor. In 1 h she developed myoclonus and diffuse muscle rigidity prominent in lower extremities. All laboratory tests were unremarkable except hyperglycemia (160 mg/dl), sinus tachycardia (103/min), and metabolic acidosis (7.051 pH, 52 mmHg pO2, 74.7 mmHg pCO2, 15% HCO3, 77% SaO2). Despite oxygen supplementation, her respiratory acidosis got worse and the SaO2 concentration decreased to 72%. Endotracheal intubation and paralysis were decided to control muscle hyperactivity followed by hyperthermia (max. 42.3oC) unresponsive to benzodiazepine. Even aggressive supportive treatment (mechanical ventilation, buffer replacement, cyproheptadine, and dantrolene) were applied, the patient could not recover and suffered cardiopulmonary arrest 20 h after presentation. Conclusion: Physicians working in the emergency departments and intensive care units, managing patients presenting with acute ingestion of selective serotonin reuptake inhibitors combined with monoamine oxidase inhibitors, should be aware of recognizing and treating serotonin stndrome. This is because many of these patients may require intensive care monitoring as well as tracheal intubation and ventilatory support.

Propofol and Thiopental Do Not Interfere with Regional Cerebral Blood Flow Response at Sedative Concentrations

Anesthetics may affect the regional cerebral blood flow (rCBF) response associated with increased brain activity in humans. rCBF was measured as auditory stimulus rate was increased during propofol and thiopental administration. After informed consent, 10 right-handed male volunteer participants (aged 33.5 +/- 10.4 yr, weighing 74.5 +/- 8.4 kg) received thiopental (n = 4) or propofol (n = 6) intravenously at stepwise target concentrations of propofol 1.2 and 2.5-3, or thiopental 4 and 7-9 microg/ml, representing sedative and hypnotic drug concentrations. The latter made volunteers unresponsive to voice or mild stimulation. Quantitative positron emission tomographic brain images were obtained at 0, 20, and 40 auditory words per minute at each drug concentration. Using SPM99 analysis, 10-mm spherical regions of interest were identified by peak covariation of word rate with rCBF across all conditions and drug concentrations. Individual mean rCBF responses in these and primary auditory cortex (Heschl's gyri) were obtained. Significant increases in rCBF with auditory word rate occurred in temporal lobes bilaterally at baseline (significance, T = 4.95). There was no change in this response during sedation (T = 5.60). During unresponsiveness seven of 10 participants had a diminished response in the left temporal lobe (T = 3.18). Global CBF, corrected for changes in PCO2 (3% .mmHg PCO2), was reduced 15% by sedation and 27% during unresponsiveness. The presence of propofol or thiopental does not affect the rCBF response to increasing stimulus rate during consciousness. Thus, changes in rCBF activation patterns with sedative concentrations of these drugs represent effects on brain activity itself. The neuroanatomical targets of drug effect on memory and attention may be revealed by changes in rCBF patterns associated with these cognitive activities.

Decreases in mesenteric blood flow associated with increases in sublingual PCO2 during hemorrhagic shock.

We investigated relationships between visceral blood flow, intestinal wall carbon dioxide tension (PCO2), and sublingual PCO2 during hemorrhagic shock. In five pigs, cardiac output declined 81% and superior mesenteric blood flow 77% during hemorrhage. Duodenal PCO2 increased from an average of 50 to 121 mmHg and sublingual PCO2 concurrently increased from an average of 46 to 101 mmHg. Within 60 min after reinfusion of shed blood, duodenal and sublingual PCO2 returned to baseline values. Decreases in mesenteric blood flow were correlated with increases in sublingual (r = 0.91; P < 0.001) and duodenal (r = 0.89; P < 0.001) tissue PCO2. In five randomized "sham hemorrhage" control animals, neither decreases in cardiac output or mesenteric blood flow nor increases in duodenal or sublingual PCO2 were observed. Decreases in mesenteric blood flow during hemorrhage were therefore associated with early and comparable increases in tissue PCO2 in both visceral and sublingual sites.

Impaired cerebral vasoreactivity correlates with recent symptomaticity in severe carotid artery disease

P62 OBJECTIVE: Impaired cerebral vasomotor reactivity has been proposed as a measure of exhausted vascular reserve in patients with carotid artery stenosis or occlusion. We tested this hypothesis by measuring vasoreactivity in patients with asymptomatic or recently symptomatic severe carotid artery disease. METHODS: Fourteen patients with severe carotid artery disease (5 with occlusion, 9 with stenosis 80–99%, 8 symptomatic, 6 asymptomatic within 2 years) and 7 healthy controls had continuous bilateral monitoring of mean flow velocity (MFV) in the MCAs by transcranial Doppler (TCD). End-tidal CO2 was measured continuously with an in-line capnometer connected via snorkel mouthpiece, nasal airway occluded by noseclip. After baseline measurements, subjects held their breath for 30 seconds. A breath holding index (BHI) was calculated (% change in MFV/seconds held). After return to baseline MFV, subjects breathed a 5% CO2 gas mixture for 2 minutes. CO2 reactivity was calculated as percent rise in MFV per mmHg PCO2 once the MFV curve plateaued. ANOVA was used to calculate differences between symptomatic, asymptomatic and control groups for CO2 reactivity and BHI. RESULTS: There was a highly significant difference in vasoreactivity by CO2 inhalation in the symptomatic group (2.02±.80 %/mmHg) versus the asymptomatic group (4.45±1.9 %/mmHg) and controls (3.69±.95 %/mmHg) (F 2,18 =7.85, p=.004). A linear relationship was seen between MFV and PCO2, taking multiple MFV measurements at various PCO2 levels throughout the study period (average r 2 =.60 for patients, .77 for controls). BHI did not distinguish between the groups (p=.37). CONCLUSIONS: Measuring cerebral vasoreactivity by CO2 inhalation with continuous TCD monitoring provides an important physiological index of the clinical status of patients with carotid artery disease which may help guide treatment algorithms. The linear relationship between MCA MFV and end-tidal CO2 enables confirmation of the baseline and maximum measurements used to calculate CO2 reactivity, and provides the opportunity to investigate further the link between physiology and clinical state.

Laboratories on the Move: Blood Gas Analysis

We evaluated the performance of a portable instrument for measuring pH, PCO2, and PO2 during land and air transport of critical care patients. We determined accuracy and precision by analyzing control materials with known values and by running duplicate analyses of patient specimens. The control data showed that the instrument performed as well in a moving ambulance and in an airborne jet-powered aircraft as it did while in a stationary position on the ground. Duplicate results of patient specimens showed good correlation. The maximum differences between mean control values were 0.002 for pH, 0.2 mm Hg for PCO2, and 3.9 mm Hg for PO2. For PCO2 and PO2, the precision was slightly lower in the moving vehicles than on the ground, but appeared adequate for medical decisions. Our results indicate that this analyzer produces acceptable blood gas results in moving vehicles.

Impaired cerebral vasoreactivity correlates with recent symptomaticity in severe carotid artery disease

P62 OBJECTIVE: Impaired cerebral vasomotor reactivity has been proposed as a measure of exhausted vascular reserve in patients with carotid artery stenosis or occlusion. We tested this hypothesis by measuring vasoreactivity in patients with asymptomatic or recently symptomatic severe carotid artery disease. METHODS: Fourteen patients with severe carotid artery disease (5 with occlusion, 9 with stenosis 80–99%, 8 symptomatic, 6 asymptomatic within 2 years) and 7 healthy controls had continuous bilateral monitoring of mean flow velocity (MFV) in the MCAs by transcranial Doppler (TCD). End-tidal CO2 was measured continuously with an in-line capnometer connected via snorkel mouthpiece, nasal airway occluded by noseclip. After baseline measurements, subjects held their breath for 30 seconds. A breath holding index (BHI) was calculated (% change in MFV/seconds held). After return to baseline MFV, subjects breathed a 5% CO2 gas mixture for 2 minutes. CO2 reactivity was calculated as percent rise in MFV per mmHg PCO2 once the MFV curve plateaued. ANOVA was used to calculate differences between symptomatic, asymptomatic and control groups for CO2 reactivity and BHI. RESULTS: There was a highly significant difference in vasoreactivity by CO2 inhalation in the symptomatic group (2.02±.80 %/mmHg) versus the asymptomatic group (4.45±1.9 %/mmHg) and controls (3.69±.95 %/mmHg) (F 2,18 =7.85, p=.004). A linear relationship was seen between MFV and PCO2, taking multiple MFV measurements at various PCO2 levels throughout the study period (average r 2 =.60 for patients, .77 for controls). BHI did not distinguish between the groups (p=.37). CONCLUSIONS: Measuring cerebral vasoreactivity by CO2 inhalation with continuous TCD monitoring provides an important physiological index of the clinical status of patients with carotid artery disease which may help guide treatment algorithms. The linear relationship between MCA MFV and end-tidal CO2 enables confirmation of the baseline and maximum measurements used to calculate CO2 reactivity, and provides the opportunity to investigate further the link between physiology and clinical state.

Accuracy of a Portable Blood Gas Analyzer Incorporating Optodes for Canine Blood

The accuracy of a portable blood gas analyzer (OPTI 1) was evaluated using canine blood and aqueous control solutions. Sixty‐four arterial blood samples were collected from 11 anesthetized dogs and were analyzed for pH, partial pressure of carbon dioxide (Pco2), partial pressure of oxygen (Po2), and bicarbonate concentration ([HCO3‐]) values by the OPTI 1 and a conventional blood gas analyzer (GASTAT 3). The conventional analyzer was considered as a standard against which the OPTI 1 was evaluated. Comparison of OPTI 1 results with those of GASTAT 3 by linear regression analysis revealed a high degree of correlation with the GASTAT 3 (r= .90‐.91). The mean ± SD of the differences between OPTI 1 and GASTAT 3 values was ‐0.008 ± 0.017 for pH, ‐0.88 ± 3.33 mm Hg for Pco2, 3.71 ± 6.98 mm Hg for Po2, and ‐0.34 ± 1.45 mEq/L for [HCO3‐]. No statistically significant difference was found between the OPTI 1 and the GASTAT 3. Agreement between these 2 methods is within clinically acceptable ranges for pH, Pco2, Po2, and [HCO3‐]. The coefficients of variation for measured pH, Pco2, and Po2 values of 3 aqueous control solutions (acidic, normal, and alkalotic) analyzed by the OPTI 1 ranged from 0.047 to 0.072% for pH, 0.78 to 1.81% for Pco2, and 0.73 to 2.77% for Po2. The OPTI 1 is concluded to provide canine blood gas analysis with an accuracy that is comparable with that of conventional benchtop blood gas analyzers.

Accuracy of a portable blood gas analyzer incorporating optodes for canine blood.

The accuracy of a portable blood gas analyzer (OPTI 1) was evaluated using canine blood and aqueous control solutions. Sixty-four arterial blood samples were collected from 11 anesthetized dogs and were analyzed for pH, partial pressure of carbon dioxide (PCO2) partial pressure of oxygen (PO2), and bicarbonate concentration ([HCO3-]) values by the OPTI 1 and a conventional blood gas analyzer (GASTAT 3). The conventional analyzer was considered as a standard against which the OPTI 1 was evaluated. Comparison of OPTI 1 results with those of GASTAT 3 by linear regression analysis revealed a high degree of correlation with the GASTAT 3 (r = .90-.91). The mean +/- SD of the differences between OPTI 1 and GASTAT 3 values was -0.008 +/- 0.017 for pH, -0.88 +/- 3.33 mm Hg for PCO2, 3.71 +/- 6.98 mm Hg for PO2, and -0.34 +/- 1.45 mEq/L for [HCO3-]. No statistically significant difference was found between the OPTI 1 and the GASTAT 3. Agreement between these 2 methods is within clinically acceptable ranges for pH, PCO2, PO2, and [HCO3-]. The coefficients of variation for measured pH, PCO2, and PO2 values of 3 aqueous control solutions (acidic, normal, and alkalotic) analyzed by the OPTI 1 ranged from 0.047 to 0.072% for pH, 0.78 to 1.81% for PCO2, and 0.73 to 2.77% for PO2. The OPTI 1 is concluded to provide canine blood gas analysis with an accuracy that is comparable with that of conventional benchtop blood gas analyzers.

Evaluation in volunteers of the VIA V-ABG automated bedside blood gas, chemistry, and hematocrit monitor.

To evaluate the VIA V-ABG (VIA Medical Corp.) point-of-care blood gas and chemistry monitor in healthy human volunteers, with particular emphasis on the measurement of blood gases. Experimental conditions were varied by intermittently subjecting volunteers to either isocapnic hypercapnia (end-tidal (ET), PETCO2 = 50+/-2 mmHg, ETPO2 = 130+/-5 mmHg) or isocapnic hypoxia (PETCO2 = 42+/-2, PETO2 + 45+/-2 mmHg) in addition to room air breathing. Measurements by the VIA V-ABG device were compared with paired samples and measurements performed by two ABL Radiometers (505 and 500). Analysis of results includes bias and precision plots and comparison of results with minimal performance criteria as established by CLIA. Nineteen volunteers yielded 222 matched samples. The range of values were 7.32-7.61 for pH, 20.9-51.6 mmHg for PCO2, 27.9-184.5 mmHg for PO2, 134-141 mmol/l for Na, 3.1-4.1 mmol/l for K, and 30.0-50.4% for hematocrit. Bias and precision (+/-2 sd) for pH was 0.01 and 0.04, for PCO2 was 0.4 and 4.8, for PO2 was 1.0 and 17.0, for Na was -0.3 and 5.2, for K was 0.1 and 0.2, and for Hct was 2.0 and 5.4. Over the range of blood gas values assessed, blood gas measurements by the VIA V-ABG device were clinically acceptable and met minimal performance criteria utilizing current Medicare CLIA proficiency standards. Performance criteria were also met by the VIA V-ABG device for Na, K, and Hct measurements but the range of values was too narrow to allow characterization of clinical acceptability. The VIA V-ABG device appears to perform well compared with the results which have been published for other point-of-care devices. Comparison between different studies investigating point-of-care devices is difficult due to several factors (range of values measured, comparison device, population studied, etc.). Some of these instruments, including the VIA V-ABG device, may serve quite well as point-of-care devices to perform certain tests at the bedside. Whether or not any of these devices can substitute for traditional laboratory blood gas and chemistry measurements remains an issue that is not adequately studied.

Glycosylation of CHO-derived recombinant tPA produced under elevated pCO2.

Carbon dioxide is a metabolic byproduct of mammalian cell metabolism that can accumulate in poorly ventilated cultures. A buildup of CO2 at constant pH will be accompanied by an increase in medium osmolality. We have examined the glycosylation of tissue plasminogen activator (tPA) produced under serum-free conditions by recombinant Chinese hamster ovary (CHO) cells (MT2-1-8 cell line) in response to elevated pCO2 at constant or elevated osmolality. The proportion of sialic acids comprising N-glycolylneuraminic acid decreased from 2.3-4.0% under 36 mmHg pCO2 to 1.5-2.2% under 250 mmHg pCO2. No changes were observed in the total sialic acid content, the content of other monosaccharides, the relative amounts of type I and type II tPAs, the distribution of surface charges, or the proportion of high-mannose oligosaccharides-even though these conditions have previously been shown to inhibit the specific growth rate of MT2-1-8 cells by 30-40% and the specific tPA production rate by as much as 40%. These results suggest robust glycosylation of tPA by CHO cells.

Clinical evaluation of a new continuous intraarterial blood gas monitoring system in the intensive care setting

The present study was designed to evaluate a new continuous intraarterial blood gas monitoring system under routine clinical intensive care conditions. Nine mechanically ventilated adult patients were enrolled in this study. A multiparameter intravascular sensor was inserted into the radial or dorsalis pedis artery through a 20-gauge cannula in each patient. The accuracy of the sensor for pH, Pco2, and Po2 values was evaluated by comparing the data simultaneously obtained from the monitoring system and from conventional blood gas analysis. Measurements were performed for 3 days for each sensor. A total of 62 blood samples were obtained for comparison. The ranges of measured variables were: pH 7.185-7.602, Pco2, 28.8-68.5 mmHg, and Po2 45.2-542.4 mmHg. The overall bias ±precision values were 0.002±0.018 for pH units, 0.53±2.04mmHg for Pco2, and -1.62±20.00 mmHg for Po2. In clinically important ranges of Po2, less than 200 mmHg in particular, the bias and precision values were -2.25±6.48 mmHg in the range of less than 100mmHg, and 0.98±14.38 mmHg in the range of 100-200 mmHg. Variations of sensor accuracy as a function of elapsed time were within the clinically acceptable range throughout the study period. These findings suggest that this new device is sufficiently useful for routine clinical settings.