Blood Gas Monitoring Research Articles

Continuous pH and pCO2 Monitoring Using the Paratrend Inserted Through a Pulmonary Artery or Central Venous Catheter

The Paratrend continuous blood gas monitoring system was placed through a pulmonary artery or central venous catheter as a means of continuously monitoring pH, pCO2, and mixed venous oxygen saturation in three neonates at risk for cardiorespiratory dysfunction, two following surgery for congenital heart disease and one with septic shock. After calibration with an arterial/mixed venous blood gas value, the Paratrend monitor provided a clinically useful continuous measurement of pH and pCO2. The difference between the Paratrend and the arterial values for pH and pCO2 were 0.02 ± 0.009 and 2.4 ± 0.8 mmHg, respectively. There was a significant discrepancy between the oxygen saturation reading from the Paratrend and the actual measured mixed venous value (9 ± 5%). The possible applications of the Paratrend placed through a pulmonary artery or central venous catheter are discussed.

Anesthesia in extreme obesity

Approximately 1-2% of all anesthetized patients are morbidly obese (body mass index > 35 kg/m2). The perioperative mortality is significantly elevated (up to 20%) compared with lean patients. Morbidly obese patients are at high risk for cardiopulmonary dysfunction. Difficult airway management is reported in 13-20% of obese patients. Hypoxia is often observed due to faster desaturation during induction of anesthesia. After surgery, patients are endangered by a high incidence of obstructive sleep apnea syndrome (50%), pulmonary atelectasis (5%) and acute pulmonary embolism (5-12%). Individualized perioperative management is required based on preoperative history and physical examination. Modern anesthetic drugs (desfluran, sevoflurane or propofol, and remifentanil, respectively) allow rapid recovery and early postoperative mobilization. Adequate monitoring, e.g. by an intraarterial blood pressure monitoring and repetitive blood gas analyses, improves patient safety prior the onset of complications. Postoperative admission on an intensive care unit of morbidly obese patients is based upon concomitant diseases and surgical requirements. The main reason for admission is an inadequate pulmonary gas exchange. This interdisciplinary approach will reduce the risk of anesthesia and avoid complications in morbidly obese patients.

A cardiopulmonary bypass score system to assess quality of perfusion performance

During cardiopulmonary bypass, the perfusionist maintains physiological parameters laid down in protocols; this is his or her performance capability. In order to assess his or her performance we need to be able to analyse these physiological parameters objectively. We defined six parameters, pH, BE, PaCO2, PaO2, ACT and oesophageal temperature and gave them ideal values of 7.40+/-0.05, 0.0+/-2.5 mmol/l, 39.0+/-3.0 mmHg, 150+/-50 mmHg, 540+/-60 s and 37.2+/-0.2 degrees C, respectively. We established ranges and a score system: +/- one standard deviation of the mean for a score of zero; between +/- one and two standard deviations for a score of one; and greater than +/- two standard deviations for a score of two. We captured and analysed the most outlying value, with respect to known normal values, for each parameter recorded on the pump sheet. This was performed for 100 consecutive patients. Mean +/- standard deviation (medians) values for pH, BE, PaCO2, PaO2, ACT and oesophageal temperature were 7.41+/-0.07 (7.41), -1.85+/-2.37 mmol/l (-1.85 mmol/l), 34.6+/-5.42 mmHg (34.0 mmHg), 320+/-96.2 mmHg (317 mmHg), 558+/-164 s (503 s) and 37.3+/-0.5 degrees C (37.4 degrees C), respectively. We then analysed what percentage of our 100 patients fell within each score range for each of the six parameters. This is an efficient means in analysing whether the perfusionist abides by the protocols, what quality is supplied to the patient, does he or she react when he or she is faced with parameters that are out of range and finally advocating in-line blood gas monitoring. This is another step towards our goal of total quality management.

An update on perfusion safety: does the type of perfusion practice affect the rate of incidents related to cardiopulmonary bypass?

Cardiopulmonary bypass (CPB) techniques vary among adult and pediatric patients undergoing cardiac surgery. This may result in a differential conduct of CPB between various aged patients. The present study reports on perfusion incidents occurring in hospitals using extracorporeal circulation. An 80 question survey was mailed to chief perfusionists at all 1030 US cardiac surgical centers. Respondents were asked to report on device use and incidents occurring during a 2-year period from July 1996 to June 1998. Five hundred and twenty-four completed surveys were returned with the age of surgical patients operated on at each hospital defined as either an adult (n=407), pediatric (n=17), or combined-adult and pediatric (n=100). Centrifugal pumps were used as the primary systemic pumps in 54% of adult, 12% of pediatric, and 36% of combined centers. In-line blood gas monitoring was used in 76% of all pediatric hospitals, but in only 30% of adult facilities. Incident rates occurred once per every 120.9, 83.9, and 220.2 cases in adult, pediatric, and combined centers, respectively. Mortality rates related to CPB occurred 2.7 times higher in adult and pediatric centers as compared to combined hospitals. Arterial dissection was the number one cause of death in both pediatric and combined hospitals, while coagulation disturbances resulted in the highest mortality for adult procedures. Results of this study show that the lowest incident rates occur at hospitals performing combined adult and pediatric CPB.

Continuous pH and pCO2 Monitoring Using the Paratrend Inserted Through a Pulmonary Artery or Central Venous Catheter

The Paratrend continuous blood gas monitoring system was placed through a pulmonary artery or central venous catheter as a means of continuously monitoring pH, pCO2, and mixed venous oxygen saturation in three neonates at risk for cardiorespiratory dysfunction, two following surgery for congenital heart disease and one with septic shock. After calibration with an arterial/mixed venous blood gas value, the Paratrend monitor provided a clinically useful continuous measurement of pH and pCO2. The difference between the Paratrend and the arterial values for pH and pCO2 were 0.02 ± 0.009 and 2.4 ± 0.8 mmHg, respectively. There was a significant discrepancy between the oxygen saturation reading from the Paratrend and the actual measured mixed venous value (9 ± 5%). The possible applications of the Paratrend placed through a pulmonary artery or central venous catheter are discussed.

Spectral analysis of fetal heart rate variability as a predictor of intrapartum fetal distress

Objective: To evaluate the usefulness of power spectral analysis on fetal heart rate variability as a new diagnostic method of fetal distress. Study design: Among 76 pregnant women who underwent computerized electronic fetal monitoring and cord blood gas analysis, we divided them into three groups: normal fetus group (36); presumed distress group (26); and acidemic distress group (14). In order to perform linear analysis on the raw data of the fetal heart rate, after resampling, we performed Fourier transformation and investigated power distributions among very low frequency (VLF), low frequency (LF), high frequency (HF) bands, and autonomic balance (LF/HF). Results: The results of the spectral analysis showed that in normal fetus group, the difference in the distribution of power spectrums of VLF, LF and HF was significantly higher than in presumed distress group and acidemic distress group. In fetal distress, the LF and VLF value (≤0.0023, ≥0.0437) were good predictors (sensitivity 97.5%, 75.0% and specificity 86.1%, 94.4%). The LF value (≤0.0013) was a good predictor in fetal acidemia (sensitivity 97.5% and specificity 86.1%). C onclusions: A computerized spectral analysis of fetal heart rate variation is a good predictor of fetal distress, which is made automatically and objectively.

A brief review of Dr F Gotoh's contribution to neuroscience: research in the field of cerebral blood flow and stroke.

Professor Emeritus Fumio Gotoh began and continues his remarkable career in medicine at Keio University. Since his graduation from medical school there in 1951, Dr. Gotoh has devoted himself to neurology, especially in the enigmatic field of stroke science. He is most renown for his groundbreaking research and leadership in the study of cerebral blood flow and metabolism. Beginning with his doctoral thesis paper in 1959 entitled "Effects of blood pressure on cerebral circulation," our article briefly delineates how Prof. Gotoh has paved the path for current and future discoveries in modern medicine. Although wholly difficult to sum up Dr. Gotoh's extensive career in such a short article, we have attempted to chronologically list and furthermore to describe his numerous works. Herein we describe his expansion to the international arena with his contributions at Wayne State University as well as his novel cerebral blood gas monitoring techniques now used in modified fashion throughout the world. From his CO2-based investigations in animals to his study of the autonomic nervous system's role in human cerebrovascular control, we remark on Dr. Gotoh's accomplishments without the use of functional imaging. Yet despite the basic science theme of his research, he has always kept them clinically correlated to entities such as Cheyne-Stokes phenomenon and Shy-Drager syndrome. Prof. Gotoh has been asked to head some of the most influential stroke societies and was the second president of the International Stroke Society. In conjunction with leading authorities, he developed a quantifiable, evidence-based stroke scale which was introduced in the International Journal of Stroke in 2001. Today despite his retirement, Dr. Gotoh continues his work in cerebral blood flow and metabolism.

Exercise Intolerance Following Heart Transplantation: The Role of Pulmonary Diffusing Capacity Impairment

Although impairment of the diffusing capacity of the lung for carbon monoxide (DLCO) in heart transplant recipients is well-documented, there are limited data on its impact on exercise capacity in these patients. The aim of this study was to determine the effect of DLCO reduction on exercise capacity in heart transplant recipients. Descriptive cohort study. A regional cardiopulmonary transplant center. Twenty-six heart transplant recipients who were studied before and after transplantation compared with 26 healthy volunteers. Spirometry and static lung volumes were measured using body plethysmography, DLCO was measured using the single-breath technique, and progressive cardiopulmonary exercise was performed using a bicycle ergometer, continuous transcutaneous blood gas monitoring, and on-line analysis of minute ventilation, oxygen uptake (VO(2)), and carbon dioxide production. Before transplantation, the mean percent predicted for hemoglobin-corrected DLCO was reduced in patients (73.2%) compared to healthy control subjects (98.8%; p < 0.001) and declined significantly after transplantation (60.1%; p < 0.05). Although the mean maximal symptom-limited VO(2) (VO(2)max) increased after transplantation (increase, 41.3 to 48.6% of predicted; p < 0.05), it remained substantially lower than normal (92.9%; p < 0.001). There was a significant correlation between DLCO and VO(2)max after transplantation (r = 0.61; p = 0.001), but not before transplantation (r = 0.09; p = 0.66). DLCO was also inversely correlated with other respiratory responses to exercise, including the following: the ventilatory response to exercise (r = -0.44; p < 0.05); dead space to tidal volume ratio (r = -43; p < 0.05); and the alveolar-arterial oxygen gradient (r = -0. 45; p < 0.05), but there was no correlation between any of these variables and DLCO before transplantation. DLCO reduction after heart transplantation appears to represent persistent gas exchange impairment and contributes to exercise limitation in heart transplant recipients.

The Effects of Continuous Blood Gas Monitoring During Cardiopulmonary Bypass: A Prospective, Randomized Study—Part I

The use of continuous in-line blood gas management (CILBGM) is steeped in controversy concerning its potential utility and impact on patient outcomes. The purpose of this study was to determine whether the use of CILBGM results in improved quality of patient care. Fifty-nine patients were enrolled in a Institutional Review Board-approved, prospective, randomized study. An in-line blood gas monitor (CDI 500) was placed into the arterial and venous lines for all patients. Blood gas monitoring in the control group was managed by intermittent sampling (every 20–30 min), while the treatment group was managed with continuous monitoring. There were no differences between groups in preoperative, surgical, anesthetic, or perfusion variables. The accuracy of the in-line monitor was comparable to laboratory analysis for arterial blood gas parameters (N = 160; pH bias = 0.00; PaCO2 bias = −1.1 mmHg; and PaO2 bias = 0.7 mmHg). There was less deviation from target values (pH = 7.40, PaCO2 = 40 mmHg, PaO2 = 150–200 mmHg) when in-line monitoring was used versus intermittent sampling (N = 784; pH deviation = 0.05 ± 0.03 vs. 0.03 ± 0.01, p &lt; 0.0001; PaCO2 deviation 44.0 ± 2.9 mmHg vs. 2.0 ± 0.9 mmHg, p &lt; 0.0001; and PaO2 deviation = 22.7 ± 16.9 mmHg vs. 11.7 ± 8.3 mmHg, p &lt; 0.0001). In conclusion, the results of part I of this study demonstrate that the use of CILBGM results in more accurate blood gas management during CPB.

The Effects of Continuous Blood Gas Monitoring During Cardiopulmonary Bypass: A Prospective, Randomized Study—Part II

The impact of blood gas management during cardiopulmonary bypass (CPB) on patient care has not been examined and remains controversial. The purpose of this study was to determine whether precise blood gas management during CPB influences patient outcome. Fifty-nine patients were enrolled in an Institutional Review Board-approved, prospective, randomized study. An in-line blood gas monitor (CDI 500) was placed into the arterial and venous lines for all patients. Blood gas monitoring in the control group was managed by intermittent sampling (every 20–30 min), while the treatment group was managed with continuous monitoring. Blood gas control and measured parameters were as follows: pH 7.40 ± 0.05, PaCO2 40 ± 5 mmHg, PaO2 200 ± 50 mmHg. The treatment group had the CDI 500 guide clinical decisions. Compared to the control group, the treatment group consisted of significantly more diabetic (7% vs. 47%, p ≤ 0.001), renal failure (3% vs. 13%, p ≤ 0.01), and chronic obstructive pulmonary disease patients (7% vs. 20%, p ≤ 0.01). Internal thoracic artery utilization was higher in treatment patients than control patients (67% vs. 95%, p ≤ 0.02). No other differences existed in demographic, pharmacological, surgical, or anesthetic parameters. In the perioperative period, the control group required antiarrythmic support more frequently than the treatment group (10% vs. 0%, p ≤ 0.05). Compared to the control group, the treatment group required antiarrythmic (18% vs. 10%, p ≤ 0.05) and cardiac glycoside therapy (11% vs. 0%, p ≤ 0.05) less frequently in the postoperative period. Although treatment patients required less intraoperative pacing and cardioversion and spent less time on mechanical ventilation, in the intensive care unit (ICU), and in the hospital than control patients, statistical significance was not achieved. In conclusion, the use of continuous, in-line blood gas monitoring resulted in improvement in a number of postoperative outcome variables, although ICU and hospital stay was not effected.

Clinical performance of an in-line point-of-care monitor in neonates.

To evaluate the bias, precision, and blood loss characteristics of an ex vivo in-line point-of-care testing blood gas and electrolyte monitor designed for use in critically ill newborn infants. Study participants included consecutive neonates with an umbilical artery catheter (UAC) in use for clinical laboratory testing. The in-line monitor (VIA LVM Blood Gas and Chemistry Monitoring System, VIA Medical, San Diego, CA) was directly connected to the participant's UAC and the monitor's determinations of pH, PCO(2), PO(2), sodium, potassium, and hematocrit (Hct) were compared with those simultaneously drawn and measured with a standard bench top laboratory instrument (Radiometer 625 ABL; Radiometer America, Inc, Westlake, OH). The bias (the mean difference from the reference method) and precision (1 standard deviation of the mean difference) performance criteria of the in-line monitor were derived using standard laboratory procedures. Sixteen neonates monitored for a total of 37 days had a total of 229 paired blood samples available for comparison by the 2 methods. Bias and precision performance characteristics of the in-line monitor were similar to reports of other point-of-care devices (ie, pH: -.003 +/-.024; PCO(2):.35 +/- 2.84 mm Hg; PO(2):.39 +/- 7.30 mm Hg; sodium:.52 +/- 2.34 mmol/L; potassium:.17 +/-.18 mmol/L; and Hct:.61 +/- 2.80%). The range of values observed for each parameter included much of the range anticipated among critically ill neonates (ie, pH: 7.15-7.65; PCO(2): 25-75 mm Hg; PO(2): 25-275 mm Hg; sodium: 127-150 mmol/L; potassium: 2.6-5.5 mmol/L; and Hct: 32%-60%). Mean blood loss (+/- standard deviation) per sample with the in-line monitor was approximately one-tenth that of the reference method: 24 +/- 7 microL versus 250 microL, respectively. There was no evidence of hemolysis and no patient related safety issues were identified with use of the in-line monitor. Repeated laboratory testing of critically ill neonates using an ex vivo in-line monitor designed for use in neonates provides reliable laboratory results. The blood loss and hemolysis data obtained suggests that this monitoring device offers potential for reducing neonatal blood loss-and possibly transfusion needs-during the first weeks of life. Before this promising technology can be routinely recommended for care of critically ill neonates, greater practical experience in a variety of clinical settings is needed.

Noninvasive blood gas monitoring.

In the clinical setting, noninvasive blood gas monitoring has become the standard of care over arterial punctures. Technology has provided ways to measure both arterial oxygen (PaO2) and arterial Carbon Dioxide (PaCO2). With the availability of noninvasive blood gas monitoring, patient care and comfort is improving, and cost savings are being implemented. Overall noninvasive monitoring can aid in the diagnosis of some pulmonary diseases and monitor patient progress.

Continuous intra-arterial blood gas monitoring during thoracic surgery.

This study was undertaken to assess the clinical usefulness of a continuous intra-arterial blood gas (CIABG) monitoring system, Paratrend 7, during thoracic surgery. A sensor of the CIABG monitoring system was inserted into the radial artery in 50 patients. During one-lung/differential lung ventilation, arterial blood samples for estimation of blood gases (ABG) were taken every 45-90 min or when clinically needed. The PCO(2), PO(2), and pH values displayed by the CIABG monitor were recorded prior to arterial blood sampling and were compared with the results of ABG analysis. The mean (bias) and the standard deviation (precision) of the differences were calculated from the data for each parameter. Ninety-four blood samples were obtained. The correlation between CIABG and ABG measurements was strong for each parameter: r = 0.83 (PCO(2)), 0.89 (PO(2)), 0.74 (pH). The bias +/- precision between the two methods was 0.4 +/- 3.0 mmHg for PCO(2), -6 +/- 47 mmHg for PO(2), -1.2 +/- 27.4% for PO(2) and -0.01 +/- 0.04 for pH. For PO(2) values <150 mmHg, the bias +/- precision was 1 +/- 28 mmHg. The agreement between CIABG and ABG measurements was better for PCO(2) and pH than for PO(2). The PO(2) value displayed on the CIABG monitor may not always be reliable during thoracic surgical procedures.

The increase in CO2 production induced by NaHCO3 depends on blood albumin and hemoglobin concentrations.

To evaluate the origin of H+ ions participating in the generation of CO2 coming from sodium bicarbonate infusion during metabolic acidosis. We hypothesized that these H+ ions come from a back-titration of the main non-bicarbonate buffers present in the blood, i. e. the hemoglobin and the albumin, and thus postulated that the rate of CO2 release from a bicarbonate load is dependent on the concentration of these buffers. Prospective clinical and experimental study. Surgical intensive care unit of a university hospital. (1) Sixteen stable sedated and artificially ventilated critically ill patients with a mild base deficit. (2) Acidotic human blood (bicarbonate 5 mM, pH 7.0) of hematocrit 5, 10, 20 and 40% regenerated from a mixture of frozen fresh plasma and packed red blood cells. infusion of 1.5 mmol/kg sodium bicarbonate over 5 min. Regenerated blood: 25 mM sodium bicarbonate load. continuous measurement of CO2 production (VCO2) on the expired gas using a metabolic monitor and arterial blood gas analysis before (T0), at the end (T5) and at 10, 30 and 60 min after the beginning of the bicarbonate infusion. The increase in VCO2 was 18 +/- 7% leading to a rise in PaCO2 from 39.6 +/- 2.3 at T0 to 46.2 +/- 2.7 mmHg at T5. The increases in VCO2 and in PaCO2 were significantly correlated to the albumin (r = 0.73, p < 0.005 and r = 0.70, p < 0.005, respectively) and to the hemoglobin (r = 0.51, p < 0.05 and r = 0.65, p < 0.01, respectively) concentrations. Regenerated blood: gas analysis 1 min after the bicarbonate load. The increase in PCO2 was closely related to the hematocrit (Ht) of the blood as it was 15.9 +/- 7.5 mmHg for Ht 5%, 29.0 +/- 9.6 for Ht 10%, 44.2 +/- 5.9 for Ht 20% and 71.0 +/- 3.5 for Ht 40% (n = 5 for each, p < 0.001). The importance of the release of CO2 from a bicarbonate load is dependent on the concentration of the blood non-bicarbonate buffers. It is therefore likely that the adverse effects of bicarbonate therapy linked to the CO2 generation are more important in patients with high blood albumin and hemoglobin concentrations.

Continuous pH and P CO2 monitoring during respiratory failure in children with the Paratrend 7 inserted into the peripheral venous system

The Paratrend monitor provides continuous arterial blood gas monitoring after insertion through a >/=20-gauge arterial cannula. To determine the correlation of arterial blood gas values and the Paratrend monitor placed through a peripheral intravenous catheter. Prospective, open-label evaluation. University-based pediatric intensive care unit. Infants and children with respiratory failure and arterial access. The cohort included 23 infants and children. A total of 100 sample sets (Paratrend/ABG Pco(2) and pH values) were collected. The absolute difference between the arterial and Paratrend Pco(2) was 2. 9 +/- 1.8 mm Hg (range 0 to 9 mm Hg). Linear regression analysis of Paratrend Pco(2) versus arterial Pco(2) resulted in r = 0.97 and r(2) = 0.9479 (P <.001). Bland-Altman analysis of Pco(2) values demonstrated a bias +/- precision of -2.1 +/- 2.7 mm Hg. The absolute difference between arterial and Paratrend pH was 0.04 +/- 0. 02 units (range 0 to 0.15 units). Linear regression analysis of Paratrend pH versus arterial pH resulted in r = 0.83 and r(2) = 0. 7016 (P <.0001). Bland-Altman analysis of pH values revealed a bias +/- precision of 0.03 +/- 0.03 units. Inserted through a peripheral intravenous cannula, the Paratrend monitor can be used to provide an accurate estimation of arterial blood gas values in children with respiratory failure.

In vitro validation of the Tonocap® and a modified Paratrend 7® sensor

Introduction The assessment of splanchnic perfusion by measuring gastric luminalPCO2 is a clinically useful technique. The Tonocap® (Datex-Ohmeda) has been validated for such use but only provides a reading every 10 min. The Paratrend 7® Sensor (Diametrics Medical Ltd) is a device used for continuous blood gas monitoring capable of responding to changes inPCO2 within 15 s. Recently, sublingual measurement ofPCO2 has been described as a new method of assessing splanchnic perfusion.1 We modified the Paratrend 7® sensor by encasing it in a plastic sleeve in order to protect it as would be necessary for sublingual use. It was then compared with the Tonocap® by placing them both in a water bath. Methods A vigorously stirred water bath of saline at a constant temperature of 37°C was bubbled with standard calibration gas mixtures of 5% and 10% CO2 with predicted CO2 tensions being calculated from atmospheric pressure and corrected for water saturation of the bath. A Trip® catheter (Tonometrics) connected to a Tonocap® was placed in the water bath alongside two Paratrend 7® sensors, one covered by a plastic sheath, the other unsheathed. The sheath consisted of the plastic tubing from a Butterfly®-19 (Venisystems-) which had a 2 cm eye cut at the end to allow more contact with the sensor but provided protection. The Tonocap® was left to equilibrate in the water bath for 30 min. A total of 52 paired readings were taken at 10-min intervals. Results Table 35 shows the bias and precision of each measurement technique as a percentage of predicted values. Conclusions: The results for the Tonocap® and Paratrend 7® (unsheathed) are similar to previously reported studies.2 The sheathed Paratrend 7® was also shown to give a very accurate reading ofPCO2 with a very small negative bias and excellent precision.

Continuous Monitoring of Arterial Blood Gases and pH during Intraoperative Rapid Blood Administration Using a Paratrend Sensor

Background and Objectives: The aim of this study was to determine the effects of rapid transfusion of packed red cells on the arterial blood gases and acid–base status of the recipient. Materials and Methods: We studied 16 patients (mean age 66.3±9.9 years) who received rapid transfusion of 632.8±287.2 g of packed red cells in CPDA–1, stored before use for a period of 15.2±4.4 days. During transfusion, monitoring of pH, PCO₂ and PO₂ was continuous using an intra–arterial multiparameter sensor (Paratrend 7, Biomedical Sensors, UK). Results: The rate of the transfusion was 73.1±9.6 g/min and the duration of observation was 35.8±12.8 min. Arterial pH decreased from 7.446±0.023 to 7.385±0.034 (p<0.001) and PCO₂ increased from 32.31±1.35 to 36.41±1.86 mmHg (p<0.001). ΔpH and ΔPCO₂ showed significant correlation to the weight and the age of the transfused blood (p<0.001 for both dependent variables). The rate of pH change was positively but insignificantly correlated to the rate of the transfusion. Base excess was significantly decreased and end–tidal CO₂ (PetCO₂) was increased from 25.8±2.0 to 28.1±2.3 mmHg (p<0.05), significantly correlating to the amount and age of the administered component (p<0.05). PetCO₂ was not elevated when PCO₂ changes were minimal. Alterations in PO₂ were not specific and our clinical impression was that they were related to unmeasured parameters. Conclusion: Our findings suggest that the fall in pH and the elevation in PCO₂ which occur during rapid transfusion of packed red cells may go undetected or be misinterpreted if the acid–base status of the recipient is not monitored continously. These alterations are mainly of metabolic character and depend on the amount and age of the transfused component. Our data suggest that arterial sampling is essential during massive transfusions.

Continuous Monitoring of Arterial Blood Gases and pH during Intraoperative Rapid Blood Administration Using a Paratrend Sensor

Abstract Background and Objectives: The aim of this study was to determine the effects of rapid transfusion of packed red cells on the arterial blood gases and acid‐base status of the recipient. Materials and Methods: We studied 16 patients (mean age 66.3±9.9 years) who received rapid transfusion of 632.8±287.2 g of packed red cells in CPDA‐1, stored before use for a period of 15.2±4.4 days. During transfusion, monitoring of pH, PCO2 and PO2 was continuous using an intra‐arterial multiparameter sensor (Paratrend 7, Biomedical Sensors, UK). Results: The rate of the transfusion was 73.1×9.6 g/min and the duration of observation was 35.8±12.8 min. Arterial pH decreased from 7.446±0.023 to 7.385±0.034 (p&lt;0.001) and PCO2 increased from 32.31±1.35 to 36.41±1.86 mmHg (p&lt;0.001). ΔpH and ΔPCO2 showed significant correlation to the weight and the age of the transfused blood (p&lt;0.001 for both dependent variables). The rate of pH change was positively but insignificantly correlated to the rate of the transfusion. Base excess was significantly decreased and end‐tidal CO2 (PetCO2) was increased from 25.8±2.0 to 28.1±2.3 mmHg (p&lt;0.05), significantly correlating to the amount and age of the administered component (p&lt;0.05). PetCO2 was not elevated when PCO2 changes were minimal. Alterations in PO2 were not specific and our clinical impression was that they were related to unmeasured parameters.Conclusion: Our findings suggest that the fall in pH and the elevation in PCO2 which occur during rapid transfusion of packed red cells may go undetected or be misinterpreted if the acid‐base status of the recipient is not monitored continously. These alterations are mainly of metabolic character and depend on the amount and age of the transfused component. Our data suggest that arterial sampling is essential during massive transfusions.

Multiparameter brain tissue monitoring--correlation between parameters and identification of CPP thresholds.

Continuous monitoring of brain interstitial gas concentrations allows direct regional evaluation of the pathophysiology of cerebral tissues. We have incorporated the Paratrend 7 (P7) multiparameter sensor into our established multimodal monitoring of head injured patients, to investigate the relationship between brain and arterial pO2, pCO2, and pH, as well as defining thresholds for cerebral perfusion pressure (CPP). A P7 sensor was inserted into the brain tissue of 40 adult head injured patients via a modified Camino bolt or triple lumen bolt. A second sensor was placed in the femoral artery for continuous monitoring of blood gases. Data signals from 19 monitored parameters were collected onto computer at the bedside for up to 14 days. No complications were seen. For individual patients the changes in brain tissue parameters showed large variations over 24 hours and the relationship between parameters varied considerably both between patients and during the period of monitoring any one individual. Changes related to periods of arterial desaturation, cerebral hypoperfusion and therapeutic manoeuvres could be seen. Good correlation was seen between brain pCO2 and arterial pCO2 (r = 0.58). Poor correlation was seen between CPP and brain pO2, and between brain pO2 and ICP. However, by grouping values for intracranial pressure (ICP) and CPP, thresholds for brain tissue pO2 were identified in 16 patients where CPP fell below 60 mmHg. No patients where CPP was always > 60 mmHg showed a significant threshold for a drop in brain pO2 (n = 16). In conclusion, the P7 shows potential as a monitor of regional brain oxygenation and for detection of potentially damaging secondary insults. The results must be interpreted whilst considering catheter position, autoregulation and systemic arterial changes for each individual.

Intra-aortic administration of epinephrine above aortic occlusion does not alter outcome of experimental cardiopulmonary resuscitation

Intra-aortic balloon occlusion during experimental cardiopulmonary resuscitation (CPR) improves coronary perfusion pressure and resuscitability and provides unique access to the central circulation. It has been hypothesized that administration of epinephrine into the aortic arch in combination with aortic occlusion would further improve haemodynamics during CPR, resuscitability and 24 h survival. In 16 anaesthetised dogs intravascular catheters were placed for hemodynamic and blood gas monitoring. An aortic balloon catheter was placed by femoral artery insertion with its tip just distal to the left subclavian artery. Ventricular fibrillation for 7.5 min without CPR, 2.5 min of Basic Life Support with chest compressions and ventilation with 100% oxygen were followed by 30 min of Advanced Cardiac Life Support (ACLS) with systemic canine drug dosages. The intra-aortic balloon was inflated when ACLS started and gradually deflated shortly after restoration of spontaneous circulation (ROSC). Epinephrine, in 100 μg/kg boluses every 5 min until the heart was restarted or 30 min had elapsed was administered through the intra-aortic catheter in the experimental group ( n=8) and via a central venous catheter in the control group ( n=8). Coronary perfusion pressure increased during the ACLS period in both groups ( P<0.05) with no difference between the groups and there was no difference in the frequency of ROSC (experimental group 5/8, control group 4/8). Furthermore with respect to 24 h survival, there was no difference between the experimental group (2/8) and the control group (3/8). Severe macroscopic haemorrhagic necrosis of the myocardium in the dogs with ROSC was found in 4/5 in the experimental group compared to 1/4 in the control group. In conclusion, intra-aortic administration of 100 μg/kg epinephrine doses combined with aortic occlusion during experimental CPR did not alter outcome.