Effect of high vs. low arterial blood oxygen content on cerebral energy metabolite levels during hypoxia with normothermia and hypothermia in the rat

The effects of different levels of arterial blood oxygen content (CaO2) on brain tissue adenosine triphosphate (ATP), phosphocreatine (PCr), lactate, and reduced nicotinamide adenine dinucleotide (NADH) were studied during cerebral hypoxia in normothermic and hypothermic male Wistar rats with unilateral carotid ligation. Animals were exposed to hypoxia (PaO2 19--26 torr) for 25 min, and brain tissue metabolite values measured microfluorometrically were compared with those of normothermic normoxic controls. CaO2 was 4.0 +/- 0.2 ml/dl (mean +/- SEM) at PaO2 26 torr in normothermic animals. CaO2 was increased to 8.2 +/- 0.3 ml/dl at PaO2 26 torr by means of bicarbonate infusion producing a leftward shift of the oxyhemoglobin-dissociation curve in one normothermic hypoxic group. In all normothermic hypoxic groups ATP and PCr decreased and lactate and NADH increased significantly compared with control values. There was no significant difference in brain tissue metabolite values among these groups despite an increase in CaO2 by twofold in one group. Hypothermia (32 C) resulted in CaO2 8.4 +/- 0.2 ml/dl at PaO2 26 torr. This was decreased to 4.0 +/- 0.2 ml/dl by decreasing PaO2 to 19 torr in another group at the same temperature. ATP and PCr were well preserved in both groups despite the difference in CaO2s. Although the lactate and NADH levels were increased in the hypothermic group with CaO2 4.0 +/- 0.2 ml/dl, they were significantly lower than those values in normothermic hypoxic groups. These results indicate that the increase in CaO2 produced by hypothermia is not a major determinant in hypothermic protection during cerebral hypoxia.     

Retransfusion acidosis after brief haemorrhagic hypotension in the dog.

Dogs under chloralose anasthesia were bled at a rate of 50 ml/min to a total of 25 ml/kg body weight and 2 minutes later a quick reinfusion of adequate volumes of blood, dextran, or Locke's solution was done. Within 2 minutes after reinfusion, the pH of arterial blood fell by 0.074--0.127; concurrently, PaCO2 rose by 9.2-12.9 mm Hg. A close correlation was demonstrated between these changes. After retransfusion, PaO2 and the arterial lactic acid level did not change significantly. Thus retransfusion acidosis in the dog appears after a brief hypotensive period, too, but cannot be attributed to a "washout" of lactate from the tissues.     

Effects of sample storage time, temperature and syringe type on blood gas tensions in samples with high oxygen partial pressures.

BACKGROUND--Although plastic arterial sampling syringes are now commonly used, the effects of sample storage time and temperature on blood gas tensions are poorly described for samples with a high oxygen partial pressure (PaO2) taken with these high density polypropylene syringes. METHODS--Two ml samples of tonometered whole blood (PaO2 86.7 kPa, PaCO2 4.27 kPa) were placed in glass syringes and in three brands of plastic blood gas syringes. The syringes were placed either at room temperature or in iced water and blood gas analysis was performed at baseline and after 5, 10, 20, 40, 60, 90, and 120 minutes. RESULTS--In the first 10 minutes measured PaO2 in plastic syringes at room temperature fell by an average of 1.21 kPa/min; placing the sample on ice reduced the rate of PaO2 decline to 0.19 kPa/min. The rate of fall of PaO2 in glass at room temperature was 0.49 kPa/min. The changes in PaCO2 were less dramatic and at room temperature averaged increases of 0.47 kPa for plastic syringes and 0.71 kPa for glass syringes over the entire two hour period. These changes in gas tension for plastic syringes would lead to an overestimation of pulmonary shunt measured by the 100% oxygen technique of 0.6% for each minute left at room temperature before analysis. CONCLUSIONS--Glass syringes are superior to plastic syringes in preserving samples with a high PaO2, and prompt and adequate cooling of such samples is essential for accurate blood gas analysis.     

胸科手术中单肺通气期间不同通气方式的比较

目的 观察胸科手术病人麻醉中单肺通气（ＯＬＶ）期间不同通气方式的效果。方法 １０例择期胸科手术成年病人,ＡＳＡⅠ～Ⅱ级,在ＯＬＶ期间首先采用全潮气量（１０ｍｌ／ｋｇ）不加ＰＥＥＰ,随后采用半潮气量（５ｍｌ／ｋｇ）同时施加７ｃｍＨ２Ｏ ＰＥＥＰ两种通气方式,保持每分通气量不变。在开胸后ＯＬＶ前,ＯＬＶ时采用敏种通气方式后３０ｍｉｎ,以及恢复双肺通气（ＴＬＶ）后３０ｍｉｎ分别进行血气分析,同时监测气道     

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 < 0.0001; PaCO2 deviation = 4.0 +/- 2.9 mmHg vs. 2.0 +/- 0.9 mmHg, p < 0.0001; and PaO2 deviation = 22.7 +/- 16.9 mmHg vs. 11.7 +/- 8.3 mmHg, p < 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.     

Arterial hypoxaemia following premedication in patients with coronary artery disease

The effect of premedication with morphine and scopolamine, morphine alone, and scopolamine alone on arterial oxygen tension has been studied in patients with coronary artery disease undergoing bypass operations. Control arterial blood samples were obtained with the patients in the supine position breathing room air the day before operation. A second arterial blood sample was taken in the induction room with the patient breathing room air in the supine position. In the first group (scopolamine only) and second group (morphine only) cH+ (pH), PaCO2 and PaO2 did not change. In the third group (morphine and scopolamine), however, PaO2 decreased, while PaCO2 and cH+ increased (pH decreased). The changes in cH+ and PaCO2 were statistically significant, but of no clinical importance. The present study suggests that, when morphine and scopolamine premedication is used for patients with coronary artery disease, simultaneous administration of oxygen is important in helping to eliminate a possible cause of preoperative myocardial ischaemia.     

Hypercapnia increases cerebral tissue oxygen tension in anesthetized rats

PURPOSE: To test the hypotheses that deliberate elevation of PaCO(2) increases cerebral tissue oxygen tension (PBrO(2)) by augmenting PaO(2) and regional cerebral blood flow (rCBF). METHODS: Anesthetized rats were exposed to increasing levels of inspired oxygen (O(2)) or carbon dioxide (CO(2); 5%, 10% and 15%, n = 6). Mean arterial blood pressure (MAP), PBrO(2) and rCBF were measured continuously. Blood gas analysis and hemoglobin concentrations were determined for each change in inspired gas concentration. Data are presented as mean +/- standard deviation with P < 0.05 taken to be significant. RESULTS: The PBrO(2) increased in proportion to arterial oxygenation (PaO(2)) when the percentage of inspired O(2) was increased. Proportional increases in PaCO(2) (48.7 +/- 4.9, 72.3 +/- 6.0 and 95.3 +/- 15.4 mmHg), PaO(2) (172.2 +/- 33.1, 191.7 +/- 42.5 and 216.0 +/- 41.8 mmHg), and PBrO(2) (29.1 +/- 9.2, 49.4 +/- 19.5 and 60.5 +/- 23.0 mmHg) were observed when inspired CO(2) concentrations were increased from 0% to 5%, 10% and 15%, respectively, while arterial pH decreased (P < 0.05 for each). Exposure to CO(2) increased rCBF from 1.04 +/- 0.67 to a peak value of 1.49 +/- 0.45 (P < 0.05). Following removal of exogenous CO(2), arterial blood gas values returned to baseline while rCBF and PBrO(2) remained elevated for over 30 min. The hypercapnia induced increase in PBrO(2) was threefold higher than that resulting from a comparable increase in PaO(2) achieved by increasing the inspired O(2) concentration (34.9 +/- 14.5 vs 11.4 +/- 5.0 mmHg, P < 0.05). CONCLUSION: These data support the hypothesis that the combined effect of increased CBF, PaO(2) and reduced pH collectively contribute to augmenting cerebral PBrO(2) during hypercapnia.     

Transcutaneous carbon dioxide and oxygen measurement in patients undergoing microlaryngosurgery with high frequency jet ventilation

BACKGROUND: High frequency jet ventilation (HFJV) via thin tracheal tube is a convenient method of ventilation in microlaryngosurgery, but the problem of the assessment of oxygen and carbon dioxide status during HFJV is yet to be studied. METHODS: Fifteen patients undergoing microlaryngosurgery under total intravenous anesthesia with HFJV were studied. The combined transcutaneous carbon dioxide (PtcCO2) and oxygen (PtcO2) levels were compared with arterial blood gas values (PaCO2, PaO2). RESULTS: The PtcCO2 values demonstrated a high degree of correlation with PaCO2 before intubation (r = 0.97), during HFJV (r = 0.96), and after anesthesia (r = 0.93). The PaO2 values demonstrated a generally good correlation with PaO2 before intubation (r = 0.78) and during HFJV (r = 0.83), but not after anesthesia (r = 0.54). CONCLUSION: Capnography values are invalid during HFJV, and an arterial catheter is not always indicated and feasible in microlaryngoscopy. The transcutaneous devices provide an effective method for non-invasive monitoring of PaCO2 in situations where continuous and precise control of CO2 levels is desired such as in perioperative period of microlaryngosurgery with HFJV.     

The hemodynamic and metabolic effects of tourniquet application during knee surgery

We evaluated the effects of tourniquet application on the cardiovascular system and metabolism in 10 young men undergoing knee surgery with general anesthesia. The duration of inflation was from 75 to 108 min. Heart rate, mean arterial pressure, cardiac index (CI) by pulse contour method, and systemic vascular resistance were measured before, during, and after tourniquet inflation. pH, PaO(2), PaCO(2), and lactate blood concentrations were also measured. VO(2) and VCO(2) were assessed every minute from tracheal intubation up to 15 min after tourniquet deflation and VO(2) in excess of the basal value over the 15 min after deflation (VO(2)exc) was calculated. Mean arterial pressure increased 26% (P: < 0.05) during inflation and returned to basal values after deflation. CI did not change immediately after inflation; although, thereafter, it increased 18% (P: < 0.05). Five minutes after deflation, CI further increased to a value 40% higher than the basal value. Therefore, systemic vascular resistance increased 20% suddenly after inflation (P: < 0.05) and decreased 18% after deflation (P: < 0.05). VO(2) and VCO(2) remained stable during inflation and increased (P: < 0.05) after deflation. VO(2)exc depended on duration of tourniquet inflation time (Tisch) (P: < 0.05). After deflation, PaCO(2) and lactate increased (P: < 0.05) while Tisch increased. We conclude that tourniquet application induces modifications of the cardiovascular system and metabolism, which depend on tourniquet phase and on Tisch. Whether these modifications could be relevant in patients with poor physical conditions is not known. Implications: The clinical effects of tourniquet application were evaluated in 10 young men undergoing knee surgery. Our data indicate that tourniquet application causes hemodynamic and metabolic changes which may become clinically relevant after a long period of tourniquet inflation, particularly in patients with concomitant cardiovascular diseases.     

坐位全身麻醉对肺血液动力及肺内分流的影响

目的 观测神经外科手术中坐位全身麻醉对肺血液动力及肺内分流（Ｑｓ／Ｑｔ）的影响。方法 ２８例后颅窝及后颈髓手术病人，采用静脉复合诱导、吸入七氟醚或安氟醚及伍用芬太尼维持麻醉，以Ｓｗａｎ－Ｇａｎｚ导管和动脉、混合静脉缺血气检测方法监测血液动力学和肺内分流状况，参数包括ＣＩ、ＲＡＰ、ＭＰＡＰ、ＰＣＷＰ、ＰＶＲＩ、ｐＨａ、ＰａＣＯ２、ＰａＯ２、ＰａＯ２／ＦｉＯ２及Ｑｓ／Ｑｔ。分别在麻醉前、坐位前、坐位后     

The cardiorespiratory effects of laparoscopic procedures in infants

We assessed the cardiorespiratory effects of laparoscopic procedures in 27 infants aged between 36 and 365 days. Infants were monitored and anaesthetised in a standardised manner. Heart rate, mean arterial pressure, end-tidal carbon dioxide and oxygen saturation were recorded, and blood gases were measured at 5 min after intubation, 15 and 30 min after carbon dioxide pneumoperitoneum, 5 min after desufflation and after extubation. The pH, PaO2, base excess, SaO2 and SpO2 decreased, and PCO2 increased by insufflation of carbon dioxide intraperitoneally, and improved following deflation. Changes in pH and PaO2 during the study were statistically significant (p < 0.0001). The increase in PaCO2 30 min after pneumoperitoneum was statistically significant when compared with initial values. Transient arrhythmias were observed in 10 infants 1 min after pneumoperitoneum. There were no statistically significant alterations in heart rate and systolic blood pressure.     

Respiratory characteristics of a microporous membrane oxygenator.

A microporous membrane oxygenator has been used in 258 clinical perfusions for cardiac surgery. In 132 perfusions the oxygenator was ventilated with 100% O2, and in 126 perfusions 98% O2-2%CO2 was used. Patients' BSA was 0.4-2.3 M2. Bypass duration was up to 563 min. In the group ventilated with 100% O2, average PaCO2 was 30 mmHg, with arterial pH of 7.48. 98% O2-2% ventilation resulted in an average PaCO2 of 36 mmHg, with arterial pH of 7.41. CO2 transfer is influenced by gas flow rate, and data from selected cases demonstrate that increasing gas flow results in decreasing PaCO2, while decreasing gas flow increases PaCO2. The thickness of the blood film is decreased by increasing the "shim" pressure, so that increasing the "shim" presure results in higher PaO2. Oxygen saturation averaged 99% for the entire series. Addition of CO2 to the oxygen and appropriate changes in gas flow and "shim" pressure permit changes to be made in the ventilation of the device during perfusion to achieve desired levels of PaO2 and PaCO2 under widely disparate conditions of temperature and flow.     

Equilibration period for PaO2 following alteration of FIO2 in mechanically ventilated patients

To determine arterial oxygen tension (PaO2) in mechanically ventilated patients, we repeatedly measured arterial blood gas (ABG) to examine changes in PaO2 until equilibration following alteration of fractional concentrations of oxygen in inspired gas (FIO2). Forty anesthetized patients with normal arterial oxygenation were randomly assigned to one of four groups. Group 1 (n = 10): Arterial blood samples were drawn every one minute during a 15-min period of equilibration after change of FIO2 from 1.0 to 0.21. Then FIO2 was returned to 1.0 and the similar sampling was repeated. Group 2 (n = 10): The protocol was same as in Group 1 except for FIO2 targeted for 0.8 and 0.4. Group 3 (n = 10): Blood sampling was every two minutes during a 14-min period and repeated while FIO2 was altered as in Group 1. Group 4 (n = 10): The protocol was same as in Group 3 except for the target FIO2 similar to Group 2. PaO2 was stabilized in 4 min at earliest and in 6 min at latest after change of FIO2 in every settings of this study. In mechanically ventilated patients with normal arterial oxygenation, PaO2 could be stabilized after a 6-min period of equilibration following alteration of FIO2.     

Piritramide and alfentanil display similar respiratory depressant potency

BACKGROUND: The question whether some opioids exert less respiratory depression than others has not been answered conclusively. We applied pharmacokinetic/pharmacodynamic (PKPD) modeling to obtain an estimate of the C50 for the depression of CO2 elimination as a measure of the respiratory depressant potency of alfentanil and piritramide, two opioids with vastly different pharmacokinetics and apparent respiratory depressant action. METHODS: Twenty-three patients received either alfentanil (2.3 microg x kg(-1) x min-1, 14 patients, as published previously) or piritramide (17.9 microg x kg(-1) x min(-1), nine patients) until significant respiratory depression occurred. Opioid pharmacokinetics and the arterial PCO2 (PaCO2) were determined from frequent arterial blood samples. An indirect response model accounting for the respiratory stimulation due to increasing PaCO2 was used to describe the PaCO2 data. RESULTS: The following pharmacodynamic parameters were estimated with NONMEM [population means and interindividual variability (CV)]: k(elCO2) (elimination rate constant of CO2) 0.144 (-) min(-1), F (gain of the CO2 response) 4.0 (fixed according to literature values) (28%), C50 (both drugs) 61.3 microg l-1 (41%), k(eo alfentanil) 0.654 (-) min(-1) and k(eo piritramide) 0.023 (-) min(-1). Assigning separate C50 values for alfentanil and piritramide did not improve the fit compared with a model with the same C50. CONCLUSION: Since the C50 values did not differ, both drugs are equally potent respiratory depressants. The apparently lower respiratory depressant effect of piritramide when compared with alfentanil is caused by slower equilibration between the plasma and the effect site. Generalizing our results and based on simulations we conclude that slowly equilibrating opioids like piritramide are intrinsically safer with regard to respiratory depression than rapidly equilibrating opioids like alfentanil.     

Postoperative hypoxaemia: oesophagectomy with gastric replacement

Pre- and postoperative arterial blood samples were analysed for oxygen partial pressure (PaO2) and carbon dioxide partial pressure (PaCO2) in a consecutive series of 21 patients subjected to two- or three-stage oesophagectomy for carcinoma of the oesophagus. The forced vital capacity (FVC) was measured at the same time. On the second postoperative day the PaO2 showed a fall to 65 per cent of the preoperative value followed by a gradual recovery to 78 per cent on the tenth postoperative day. After 13 weeks the PaO2 had recovered to 95 per cent of the preoperative value. The PaCO2 decreased in the early postoperative period but had returned to the preoperative level by the tenth day. The FVC showed a trend similar to the PaO2 with a reduction to 33 per cent of the preoperative value on the second postoperative day, 52 per cent on the tenth day and 85 per cent after 13 weeks.     

Arterial oxygen partial pressure and cardiovascular surgery in elderly patients

Arterial blood gas assessment is still routinely performed in candidates for a cardiovascular surgery. Whether sampling arterial blood is useful in an elderly patient with a near normal lung function and who meets all other criteria for operability, is unknown. Therefore, it was our purpose to provide reference values for arterial blood gases in these patients and to examine how the level of arterial oxygen partial pressure (PaO(2)) might influence postoperative outcome. We retrospectively studied arterial blood gases in 201 patients, aged 70-92 years with normal or near normal ventilatory function awaiting a planned cardiovascular surgery. PaO(2) averaged 81.6+/-7.6 mmHg and PaCO(2) averaged 37.7+/-3.2 mmHg. Both were independent of age. Factors associated with mortality according to bivariate analysis were: gender (female), type of surgery (valve replacement), and a low PaO(2) with strictly no ventilatory abnormality. In conclusion, PaO(2) values in elderly patients with cardiac disease and normal ventilatory function are greater than those obtained by extrapolation from healthy younger subjects. PaO(2) measurement should be recommended prior to cardiovascular surgery in elderly patients since a low PaO(2) with strictly normal ventilatory function is significantly associated with an increased risk for postoperative mortality.     

Evaluation of arterial blood sampling using the B 109 syringe (radiometer)

Arterial blood gas measurements were performed after sampling with two different syringes (B 109 Radiometer and "ONCE" ASIK) and storage of the samples at 0-4 degrees C for 15 min. The blood samples were analysed in an ABL3 blood gas analyser. We found no statistically significant difference between the mean PaO2, PaCO2 and pH values with either technique of sampling. The B 109 syringe does not offer any advantages over the common plastic 2.5 ml. syringe ("ONCE").     

Transcutaneous oxygen and carbon dioxide monitoring. Use in adult surgical patients in an intensive care unit

We evaluated a combined transcutaneous oxygen and carbon dioxide (tcPO2 and tcPO2) monitor in 33 adult surgical patients in an intensive care unit. Surgical procedures included cardiothoracic, general, vascular, and orthopedic operations. Ninety-three paired, transcutaneous values were compared with simultaneously determined arterial blood gas measurements. The correlation coefficient for PaO2 was .75 (P less than .01) whereas for PaCO2 it was .55 (P less than .01). Although statistically significant, individual transcutaneous values differed by as much as 50 mm Hg from levels determined from arterial samples. Such differences make it inappropriate to use this monitor to predict actual PaO2 or PaCO2. By contrast, continuous monitoring allowed observation of acute changes associated with respiratory-care procedures and cardiovascular decompensation. Such acute changes changes were appreciated on the tcPO2 tracing but not the tcPO2 tracing. We conclude that the tcPO2 monitor is a valuable trend indicator of cardiopulmonary dysfunction, but that the tcPCO2 monitor is not.     

纤维支气管镜与机械通气联合救治肝移植术后重症肺部感染

目的 探讨纤维支气管镜(纤支镜)与机械通气联合救治肝移植术后肺部重症感染的疗效.方法 回顾分析福州总院肝胆病中心2000年1月至2007年1月肝移植术后并发重症肺部感染的46例病人采用联合机械通气,行纤支镜检查、取痰堵养、吸痰、支气管肺段灌洗等治疗,观察治疗前后动脉血气分析结果的变化及标本病原学检测和药敏实验.结果 治疗后动脉血气分析中pH,PaO2.PaCO2,SaO2指标明显好转(P＜0.05),吸出分泌物培养阳性检出率为76.1%(35/46).治疗有效率为91.3%.结论 纤支镜与机械通气联合应用救治肝移植术后重症肺部感染,有助于确定致病菌,清除气道分泌物、局部灌洗增强抗感染效果.     

Continuous measurement of intraarterial pHa, PaCO2, and PaO2 in the operating room

Miniaturized sensors based upon the principles of optical fluorescence can measure the pH, PCO2, and PO2 of liquid or gas media. A prototype of a three-component fiberoptic sensor has been developed for intraarterial application by CDI, 3M Health Care, Irvine, California. We report the first study of this continuous intraarterial monitor in patients undergoing surgical procedures under general anesthesia. Fourteen patients participated in the study. The fiberoptic sensor was calibrated before insertion and then passed through an existing 18-gauge radial artery cannula. Blood samples were drawn at frequent intervals through the same cannula for in vitro blood gas analysis. For each of the 87 arterial blood gas samples obtained, the in vitro values of pHa, PaCO2, and PaO2 were compared with simultaneous readings from the fiberoptic sensor. For pHa, the mean error (error = fiberoptic value minus in vitro value) or "bias" of the fiberoptic data was -0.032 and the standard deviation of error or "precision" was 0.042. For PaCO2, the bias was -3.8 mm Hg and the precision was 4.7 mm Hg. For PaO2, the bias was -9.0 mm Hg and the precision was 23.3 mm Hg. For PaO2 values less than 175 mm Hg, the bias was -8.5 mm Hg and the precision was 8.3 mm Hg. Expressed in terms of percentage errors, the bias +/- precision values were -11.5% +/- 13.3% for PaCO2, and -6.2% +/- 10.0% for PaO2. The duration of the surgical procedures ranged from 1.6 to 8 h with an average of 4.2 h.(ABSTRACT TRUNCATED AT 250 WORDS)