End-tidal CO2 monitoring

Two cases of malignant hyperthermia are described where the earliest sign was a rise in the end-tidal CO2 concentration. This led to nearly immediate detection and adequate treatment with sodium dantrolene. These cases demonstrate the efficacy of monitoring end-expired CO2 concentrations in patients at risk from malignant hyperthermia, as well as a means for following the adequacy of treatment.     

Effects of Suxamethonium on CO2-Production

Eighteen patients undergoing alloplastic surgery of the hip were divided into three groups, each consisting of six patients. All operations were performed under endotracheal intubation using halothane N2O-O2 anaesthesia. After a steady state as to CO2-production had been obtained, suxamethonium 1 mg kg-1 was given intravenously to the patients in Group I. A maximum rise in CO2-production of 14.8% (range: 12.9-16.8) was observed after 5 min. In Group II, patients were pretreated with pancuronium 0.01 mg kg-1: no increase in CO2-production was observed. The third group received a continuous infusion of suxamethonium. In this group there was an increase in CO2-production of 17.6% (range: 6.7-22.0) 5 min after start of infusion. The CO2-production then fell to the preinfusion level over the next 10 min.     

Perioperative gastric tonometric PCO2 and intramucosal pH in patients undergoing liver transplantation

BACKGROUND: Extensive research has focused on the role of insufficient gastro-intestinal perfusion and inflammatory activation in the development of organ dysfunction during critical illness. In patients undergoing liver transplantation, portal and caval vein clamping leads to gastro-intestinal and lower extremity venous congestion during the anhepatic phase, and studies suggest that gastro-intestinal perfusion may be compromised. This study was performed to investigate gastro-intestinal perfusion in patients undergoing liver transplantation. METHODS: In 16 patients undergoing liver transplantation, perioperative gastric tonometry with determination of tonometric PCO2, tonometric-arterial PCO2 gradient and intramucosal pH were performed. Blood gases were obtained simultaneously from the arterial and portal vein blood. RESULTS: Tonometric PCO2 was 4.6 (4.2/5.3) kPa preoperatively and increased to 5.6 (4.5/6.0) kPa during the anhepatic phase (P<0.01), while the tonometric-arterial PCO2 gradient increased from -0.3 (-0.5/0.0) kPa preoperatively to 0.7 (0.3/1.2) kPa during the anhepatic phase (P<0.01). Intramucosal pH decreased to 7.27 (7.21/7.32) u during the anhepatic phase (P<0.01, compared to preoperatively). The portal vein PCO2 was not significantly different from arterial PCO2 or tonometric PCO2 at any measurement point. CONCLUSION: This study demonstrates that clinical liver transplantation is associated with gastro-intestinal perfusion in the range of aerobic metabolism. The results do not support the presence of gastro-intestinal perfusion in the range of anaerobic metabolism.     

The Fenem CO2 detector device An apparatus to prevent unnoticed oesophageal intubation

A new oesophageal intubation detector device, the Fenem CO2 detector, was used in 100 patients intubated during anaesthesia for elective surgery. This new device was 100% accurate in the differentiation between tracheal and oesophageal placement of a tube.     

Transcutaneous Pco2 in adults

Using a transcutaneous Pco₂ (PtcCO₂) electrode, arterial Pco₂ (Paco₂) was compared with PtcCO₂in eight adults (seven patients, one normal subject) over a wide range of values of PaCO₂(2.4 to 7.87 kPa). At an electrode temperature of 43°C, PtcCO₂=1.25 Paco₂kPa (95% confidence limits: 0.60 kPa). Change in PtcCO₂accurately reflected change in Paco₂.     

二尖瓣狭窄分离术后晚期复发病人瓣膜置换术278例分析

目的　探讨风湿性二尖瓣狭窄闭式扩张分离术后晚期复发瓣膜的病理改变 ,及其再次手术方式的选择。方法　 1978年 12月至 2 0 0 1年 12月共收治风湿性二尖瓣狭窄闭式扩张分离术后晚期复发性瓣膜病 2 78例。二尖瓣复发性病变均以狭窄为主合并不同程度的关闭不全。其中合并三尖瓣功能性关闭不全 12 7例 (4 5 7% ) ,合并复发性主动脉瓣病变 33例 (11 9% ) ;二尖瓣与主动脉瓣双瓣膜病变合并三尖瓣病变 6 1例 (2 1 9% )。二尖瓣复发性病变的病理特点主要表现为 (1)交界硬化融合型 4 6例 (16 5 % ) ;(2 )后瓣钙化卷缩型 18例 (6 5 % ) ;(3)交界钙化融合型 177例 (6 3 7% ) ;(4 )瓣膜与瓣下结构钙化型 37例(13 3% )。所有病人均行二尖瓣置换术 ,其中二尖瓣与主动脉瓣双瓣置换术 33例 ;三尖瓣功能性关闭不全作改良DeVega成形术 137例、Kay二瓣化环缩术加用成形环固定 5 1例。 结果　早期死亡 19例(6 8% ) ,主要死因为心力衰竭与多脏器功能衰竭。长期生存 2 5 9例 ,随访率 95 7% ,随访 6个月～ 2 2年 ,累计随访时间 116 2 2年。晚期死亡 15例 ,累计生存率 5、10、15年分别为 85 5 %、71 2 %、6 5 1%。抗凝过量出血的发生率为 1 11%病人·年。结论　风湿性二尖瓣狭窄闭式扩张术后晚期瓣膜复发性病变 ,再次     

Airway Deadspace, End-Tidal CO2, and Christian Bohr

In order to calculate alveolar deadspace, an important measure of ventilation/perfusion mismatching, it is necessary to measure airway or anatomical deadspace (VDaw) and physiological deadspace. VDaw is usually measured graphically or by similar means, but sometimes it is estimated from a formula, based on Christian Bohr's work, in which end-tidal PCO2 is used as a measure of alveolar PCO2. In 58 patients undergoing anaesthesia and positive pressure ventilation, there were large errors in this estimate of VDaw compared to a graphical method. At tidal volumes of 400-500 ml, the median error was 34 ml; at larger tidal volumes, the median error increased to 74 ml (P less than 0.001). The size of the error was correlated to the slope of phase III, the part of the CO2 tracing representing alveolar CO2, at both ventilator settings (P less than 0.01). It is concluded that estimates of VDaw based on end-tidal PCO2 are unreliable, and their use will lead to a large part of the alveolar deadspace being wrongly accredited to VDaw.     

CO2 production and breathing pattern during invasive and non-invasive respiratory monitoring

A computerized non-invasive strain gauge system for respiratory monitoring is described and compared with pneumotachography. With the use of simultaneous capnography, changes in breathing pattern, end-tidal PCO2 and CO2 production were evaluated during non-invasive (NIM) and invasive breathing monitoring (IM) in 14 healthy subjects. An overall absolute difference between measured and calculated tidal volumes of 4.6 +/- 3.47% (r = 0.97) was found. When switching from NIM to IM, tidal volume increased by 19% and breathing frequency decreased by 11% with a 10% increase in minute ventilation. These changes were mainly accomplished by an increased respiratory drive with the timing component unaltered. During IM both end-tidal PCO2 and CO2 production increased significantly as compared with those during NIM.     

Effects of esmolol on haemodynamic response to CO2 pneumoperitoneum for laparoscopic surgery

Background : Carbon dioxide (CO₂) pneumoperitoneum for laparoscopic surgery increases arterial pressures, systemic vascular resistance and heart rate and decreases urine output.
Methods : In this double-blind randomized study esmolol, an ultrashort-acting β1-adrenoceptor antagonist was compared with physiological saline (control) in 28 patients undergoing laparoscopic surgery in standardized 1 MAC isoflurane anaesthesia. Alfentanil infusion was used to prevent the increase of mean arterial pressure more than 25% from baseline.
Results : Esmolol effectively prevented the pressor response to induction and maintenance of CO₂ pneumoperitoneum. Significantly ( P <0.001) less alfentanil was needed in the esmolol group than in the control group. Urine output was higher ( P <0.05) and plasma renin activity ( P <0.01) and urine N-acetyl-β-D-glucosaminidase levels lower in the esmolol group when compared with the control group.
Conclusions : Esmolol blunts the pressor response to induction and maintenance of pneumoperitoneum and may protect against renal ischaemia during pneumoperitoneum.     

CO2 production after suxamethonium and diazepam

The CO2-production and degree of relaxation after increasing doses of suxamethonium were measured in seven patients undergoing alloplastic surgery of the hip. The study indicates that the CO2-production rises following the injection of increasing doses of suxamethonium. Another group of patients received diazepam 0.1 mg kg-1 before the injection of suxamethonium 1 mg kg-1. CO2-production was significantly reduced compared to CO2 production when suxamethonium was not preceded by diazepam. It is suggested that diazepam in doses larger than 0.1 mg kg-1 might be effective in preventing fasciculations and postoperative muscle pains before the injection of suxamethonium in a dose of 0.5 mg kg-1.     

Breath-by-breath measurement of oxygen consumption and Fio2-Feo2with increased oxygen demand

Continuous on-line breath-by-breath measurement of pulmonary gas exchange was used to monitor the increase in oxygen uptake (VO2) and carbon dioxide excretion (VCO2) induced by the oxidative phosphorylation uncoupling agent 2, 4-dinitrophenol (DNP) in 10 dogs. With incremental doses of DNP totaling 5 mg/kg, the continuously monitored VO2 increased within 2-3 min after the first injection of the drug. VCO2 showed a similar response 4-6 min after the first injection. Temperature increase due to the pharmacological oxidative phosphorylation uncoupling required 20-30 min for a discernible change at this dose. This study also demonstrated a modified and compromised response to the drug in dogs where oxygen delivery was limited by mechanical ventilation.     

地氟烷在二尖瓣置换手术中对缺血再灌注心肌的保护作用

在心脏外科手术中心肌缺血再灌注(ischemia-reperfusion,I-R)损伤的防治是急需解决的问题。缺血预处理(ischemic preconditioning,IPC)具有心肌保护作用[1,2]。研究显示挥发性麻醉药也具有类似IPC的麻醉药预处理(anesthetic-induced preconditioning,APC)作用[3,4],能减轻I-R后     

Intrathoracic and pulmonary blood volume during CO2-pneumoperitoneum in humans

Background : Induction of CO₂-pneumoperitoneum may have significant effects on systemic and pulmonary haemodynamics. We hypothesized, that intrathoracic (ITBV) and pulmonary blood volume (PBV) are affected during intra-abdominal CO₂-insufflation, which may be pronounced by positional changes of the patient.
Methods : Sixteen anaesthetized patients were studied before, during and after CO₂-pneumoperitoneum for laparoscopic cholecystectomy. A dye indicator technique was used to assess ITBV and PBV. In addition, gas exchange and haemodynamics were recorded.
Results : In the supine position, induction of CO₂-pneumoperitoneum had no effects on ITBV, PBV and cardiac output. Mean systemic arterial pressure increased from 10.9±1.5 kPa (82±11 mmHg) to 12.7±1.5 kPa (95±11 mmHg, P<0.01). In the reverse Trendelenburg position ITBV decreased from 19.8±5.1 ml . kg^-1 to 16.7±3.7 ml . kg¹ ( P <0.05) during CO₂-insufflation, but increased to control values after 20 min. PBV decreased from 4.2±1.2 ml . kg^-1 to 3.4±1.1 ml . kg^-1 (P<0.05) and remained decreased during CO₂-pneumoperitoneum. Calculated venous admixture was unchanged throughout the study. Deflation of CO₂-pneumoperitoneum increased ITBV (22.4±5.2 ml . kg^-1, P<0.05) and cardiac output above control values.
Conclusions : In anaesthetized-paralyzed patients in the reverse Trendelenburg position intra-abdominal CO₂-insufflation is associated with significant alterations of ITBV and PBV. The release of CO₂-pneumoperitoneum is associated with a re-distribution of blood into the thorax.     

o2 and co2 following tourniquet deflation

We examined changes in O2 uptake, CO2 output, blood pressure and heart rate following tourniquet deflation in 23 patients undergoing orthopaedic surgery of the lower extremities. A pneumatic tourniquet was applied for periods ranging from 21 to 106 min (mean 51 min). Prerelease values of VO2 (O2 uptake at each min) and VCO2 (CO2 output at each min) were 201 (37) and 174 (38) (mean (SD)) ml.min-1, respectively. Significantly, VO2 and VCO2 increased by 55% and 80%, respectively, at 2 min after tourniquet release and returned to prerelease values within 8 min. The blood pressure fell significantly and the heart rate rose significantly. The increases in CO2 output and O2 uptake were dependent on the length of tourniquet inflation time; Y = 4.7 x (tourniquet time) + 54, r = 0.88, (p less than 0.001) for CO2, and Y = 1.3 x (tourniquet time) + 99, r = 0.52, (p less than 0.05) for O2. The slope of the increase in CO2 output as a function in inflation time was 3.6 times greater than that of O2 uptake. In conclusion, CO2 output and O2 uptake increased transiently after tourniquet deflation and the extent of the increase in CO2 output is more than threefold as compared with that in O2 uptake.     

Intra-arterial and extra-arterial pH, PCO2 and PO2 monitors

In vitro blood gas analysers inherently limit the frequency of serial blood gas measurements because of blood loss and cost. In vivo blood gas monitors eliminate an inherent cost and blood loss associated with measurement. Optode microsensing is a technology that can be readily adapted to in vivo measurement of pH, PCO₂ and PO₂. Optode-based intra-arterial devices that display continuous values have been developed that are practical for routine use but consistent performance remains a problem; an extra-arterial device that provides intermittent values has been shown to be consistent but is not yet available for routine use. The transfer of blood gas measurements from laboratory analysers to the combination of point-of-care analysers and monitors should have as profound an impact on acute respiratory care as did the introduction of laboratory-based blood gas analysers over 30 years ago. However, we must be sure these devices are reliable, consistent and cost beneficial in order to avoid widespread adoption of yet another technology that provides more data, more cost, and questionable patient benefit.     

Ventilation, dynamic compliance and ventilatory response to CO2

Age dependent variations in minute ventilation (VE), tidal volume (Vr), respiratory rate and dynamic compliance (Cdyn) as well as ventilatory response to inhalation of carbon dioxide (CO2) were investigated in 20 spontaneously breathing intubated infants and children during halothane anaesthesia. Ages ranged from 6 days to 5 years. Seven patients were younger than 6 months of age. Ventilation volumes were measured by pneumotachography and end tidal carbon dioxide concentration by an in-line capnograph. Fluid-filled oesophageal catheters were used for pressure recordings. Measurements were made before surgery (with and without 2.22 and 3.71% of CO2 in inspired gas) and during surgery. Regression analysis of the relationship between VE and body weight revealed no direct proportionality. On a weight basis, VE was significantly higher in younger than in older patients. Tidal volume was directly proportional to body weight. The mean (SEM) value of tidal volume was 4.3 (0.2) ml/kg. Dynamic compliance showed a direct proportionality with weight. The mean (SEM) value of Cdyn was 10 (1.1) ml/kPa/kg. There was no ventilatory response in any patient to inhalation of 2.22% CO2. In the older group of children (greater than 6 months of age) VE increased by 34% during inhalation of 3.71% CO2 (p less than 0.025). In the younger patients (less than 6 months of age) no ventilatory response to inhalation of 3.71% of CO2 was found, indicating a more pronounced depression of ventilation in these infants.     

Reliability of CO2 measurements from the airway by a pharyngeal catheter in unintubated, spontaneously breathing subjects

Although several short communications have appeared describing attempts to record the concentrations of carbon dioxide (CO₂) from the unintubated airway by a catheter placed in the nose, so far only few reports have documented the reliability of the method. To evaluate the reliability of CO₂ measurements by a catheter in the open, unintubated airway during spontaneous respiration, a 12 CH PVC catheter was forwarded through the nostril to the hypopharynx and connected to a capnograph in nine healthy volunteers. Another capnograph was connected to a tightly fitting face mask and simultaneous CO₂ recordings were attained from the two parts of the airway during normoventilation, hyperventilation and rebreathing. A corresponding blood sample was drawn from the radial artery for blood gas analysis. The configurations of the capnograms recorded from the pharyngeal catheter were similar to those recorded from the face mask. The results were analysed by a multifactor analysis of variance. The carbon dioxide tension ( p CO₂) was significantly influenced by degree of ventilation ( P <0.0001), subject ( P <0.0001), measurement site ( P =0.030) and interaction subject-ventilation ( P =0.015). In spite of the significant influence of the measurement site, the difference between end tidal carbon dioxide tension ( P CO₂(ET)) and carbon dioxide tension in arterial blood ( P CO₂(a)) was small. The mean differences between paired measurements ( p CO₂(ET)- p CO₂(a)) were -0.10 kPa±0.41 kPa (mean±SD) for the catheter and -0.20 kPa ±0.43 kPa for the face mask. The study demonstrates that reliable recordings of CO₂ concentrations during spontaneous respiration can be obtained by a thin catheter positioned in the hypopharynx.