Arterial to End-tidal Carbon Dioxide Pressure Difference during Laparoscopic Surgery in Pregnancy

Background: There is controversy about whether capnography is adequate to monitor pulmonary ventilation to reduce the risk of significant respiratory acidosis in pregnant patients undergoing laparoscopic surgery. In this prospective study, changes in arterial to end-tidal carbon dioxide pressure difference (PaCO2--PetCO2), induced by carbon dioxide pneumoperitoneum, were determined in pregnant patients undergoing laparoscopic cholecystectomy.

Methods: Eight pregnant women underwent general anesthesia at 17-30 weeks of gestation. Carbon dioxide pnueumoperitoneum was initiated after obtaining arterial blood for gas analysis. Pulmonary ventilation was adjusted to maintain PetCO2 around 32 mmHg during the procedure. Arterial blood gas analysis was performed during insufflation, after the termination of insufflation, after extubation, and in the postoperative period.

Results: The mean +/- SD for PaCO2--PetCO2 was 2.4 +/- 1.5 before carbon dioxide pneumoperitoneum, 2.6 +/- 1.2 during, and 1.9 +/- 1.4 mmHg after termination of pneumoperitoneum. PaCO2 and p H during pneumoperitoneum were 35 +/- 1.7 mmHg and 7.41 +/- 0.02, respectively. There were no significant differences in either mean PaCO2--PetCO2 or PaCO2 and p H during various phases of laparoscopy.     

Arterial to end-tidal carbon dioxide pressure difference during laparoscopic surgery in pregnancy

BACKGROUND: There is controversy about whether capnography is adequate to monitor pulmonary ventilation to reduce the risk of significant respiratory acidosis in pregnant patients undergoing laparoscopic surgery. In this prospective study, changes in arterial to end-tidal carbon dioxide pressure difference (PaCO2--PetCO2), induced by carbon dioxide pneumoperitoneum, were determined in pregnant patients undergoing laparoscopic cholecystectomy. METHODS: Eight pregnant women underwent general anesthesia at 17-30 weeks of gestation. Carbon dioxide pnueumoperitoneum was initiated after obtaining arterial blood for gas analysis. Pulmonary ventilation was adjusted to maintain PetCO2 around 32 mmHg during the procedure. Arterial blood gas analysis was performed during insufflation, after the termination of insufflation, after extubation, and in the postoperative period. RESULTS: The mean +/- SD for PaCO2--PetCO2 was 2.4 +/- 1.5 before carbon dioxide pneumoperitoneum, 2.6 +/- 1.2 during, and 1.9 +/- 1.4 mmHg after termination of pneumoperitoneum. PaCO2 and pH during pneumoperitoneum were 35 +/- 1.7 mmHg and 7.41 +/- 0.02, respectively. There were no significant differences in either mean PaCO2--PetCO2 or PaCO2 and pH during various phases of laparoscopy. CONCLUSIONS: Capnography is adequate to guide ventilation during laparoscopic surgery in pregnant patients. Respiratory acidosis did not occur when PetCO2 was maintained at 32 mmHg during carbon dioxide pneumoperitoneum.     

腹腔镜下前列腺癌根治术中呼气末CO2分压的变化及意义

目的观察腹腔镜前列腺癌根治术中动脉血CO2分压（PaCO2）与呼气末CO2分压（PetCO2）差值Pa-ETCO2变化及其临床意义。方法腹腔镜前列腺癌根治术患者28例，于气管插管全身麻醉下完成手术，术中PETCO2维持在30～35mmHg左右，分别在麻醉后（T0），气腹第30min（T1），60min（T2），120min（T3），180min（T4）取桡动脉血行血气分析测PaCO2，据监测的PETCO2及血气分析获得的PaCO2，计算每个时间点的Pa-ETCO2。结果气腹后各时间点PaCO2，MBP，PPEAK，Pa-ETCO2明显增高（P〈0．05），人工气腹60min后，Pa-ETCO2发生显著变化（P〈0．01），部分患者出现CO2蓄积。气腹后PH值明显下降（P〈0．01）。结论腹腔镜前列腺癌根治术中人工气腹60min后PETCO2不能真实反映PaCO2，当PETCO2维持在30-35mmHg时应监测PaCO2避免发生高碳酸血症。     

Arterial to end-tidal carbon dioxide tension difference in anaesthetized adults mechanically ventilated via a laryngeal mask or a cuffed oropharyngeal airway.

To evaluate arterial (PaCO2), end-tidal (PETCO2) and carbon dioxide tension difference during mechanical ventilation with extratracheal airways, 60 patients ASA physical status I-II, receiving general anaesthesia for minor extra-abdominal procedures were randomly allocated to receive either a cuffed oropharyngeal airway (group COPA, n = 30) or a laryngeal mask (group LMA, n = 30). The lungs were mechanically ventilated by IPPV using a 60% nitrous oxide and 1-1.5% isoflurane in oxygen mixture (VT = 8 mL kg-1; RR = 12 b min-1; l/E = 1/2). After PETCO2 had been stable for at least 10 min after airway placement, haemodynamic variables and PETCO2 were recorded and an arterial blood sample was obtained for measurement of PaCO2. No differences in anthropometric parameters, smoking habit, haemodynamic variables and incidence of untoward events were observed between the two groups. Airway manipulation, to maintain adequate ventilation, was required in only nine patients in the cuffed oropharyngeal airway group (30%) (P < 0.0005); however, in no case was it necessary to remove the designated extratracheal airway due to unsuccessful mechanical ventilation. The mean difference between arterial and end-tidal carbon dioxide partial pressure was 0.4 +/- 0.3 KPa in the laryngeal mask group (95% confidence intervals: 0.3-0.5 KPa) and 0.3 +/- 0.26 KPa in the cuffed oropharyngeal airway group (95% confidence intervals: 0.24-0.4 KPa) (P = NS). We conclude that in healthy adults who are mechanically ventilated via the cuffed oropharyngeal airway, the end-tidal carbon dioxide determination is as accurate an indicator of PaCO2 as that measured via the laryngeal mask, allowing capnometry to be reliably used to evaluate the adequacy of ventilation.     

Arterial to end-tidal carbon dioxide tensio difference during laparoscopy Magnitude and effect of anaesthetic technique

The relationship between arterial carbon dioxide tension and end-tidal carbon dioxide tension was studied in 25 patients during laparoscopy. Thirteen patients received general anaesthesia and 12 epidural anaesthesia. The overall mean difference between arterial and end-tidal carbon dioxide tensions was 0.44 kPa (95% confidence intervals 0.28-0.60 kPa) which was significantly less than that reported in studies during other procedures. The reasons for this difference are probably associated with the physiological changes induced by CO2 pneumoperitoneum and steep Trendelenburg positioning. The choice of anaesthetic technique did not affect the arterial to end-tidal carbon dioxide tension difference significantly (p greater than 0.9).     

Intraabdominal Carbon Dioxide Insufflation in the Pregnant Ewe: Uterine Blood Flow, Intraamniotic Pressure, and Cardiopulmonary Effects

Background: Laparoscopic surgical procedures are being performed in pregnant women with increasing frequency. Maternal-fetal physiologic changes occurring during intraabdominal carbon dioxide insufflation are poorly understood, and maternal-fetal safety is of concern during carbon dioxide pneumoperitoneum. A previous pilot study using end-tidal carbon dioxide-guided ventilation resulted in maternal and fetal acidosis and tachycardia during carbon dioxide pneumoperitoneum. Using serial arterial PCO2 to guide ventilation, this study was designed to evaluate maternal-fetal cardiopulmonary status, uterine blood flow, and the intraamniotic pressure effects of intraabdominal carbon dioxide insufflation in singleton pregnant ewes between 120 and 135 days of gestation.

Methods: In a prospective randomized cross-over study, nine ewes were to receive either abdominal insufflation with carbon dioxide to an intraabdominal pressure of 15 mmHg (n = 9; insufflation group) or receive no insufflation (n = 9; control group). Anesthesia was induced with thiopental and maintained with end-tidal halothane (1 to 1.5 minimum alveolar concentration/100% oxygen). Mechanical ventilation was guided by serial maternal arterial blood gas analysis to maintain PaCO2 between 35 and 40 mmHg. Data from insufflated animals were collected during insufflation (60 min) and after desufflation (30 min). Control group data were collected and matched to similar time intervals for 90 min. Ewes were allowed to recover, and after a rest period (48 h) they were entered in the cross-over study.

Results: During insufflation there was a significant increase (P <0.05) in maternal PaCO2 to end-tidal carbon dioxide gradient and minute ventilation, with concomitant decreases in maternal end-tidal carbon dioxide and PaO2. Intraamniotic pressure increased significantly during insufflation. No significant changes were observed in maternal hemodynamic variables, fetal variables, or in uterine blood flow during the study. There were no fetal deaths or preterm labor in any of the animals during the experiment.     

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.     

Flow requirements for the Bain breathing circuit during anaesthesia for caesarean section

We studied the relationship between arterial carbon dioxide tension (PaCO2) and fresh gas flow (FGF) during use of the Bain breathing circuit for Caesarean section anaesthesia. Thirty-one patients undergoing Caesarean section were anaesthetised using the Bain circuit with intermittent positive pressure ventilation. The PaCO2 were measured at FGF of 70 ml X kg-1 X min-1, 80 ml X kg-1 X min-1, and 100 ml X kg-1 X min-1. The FGF requirement to maintain a given PaCO2 during Caesarean section anaesthesia is the same as the requirements for nonpregnant subjects, despite the increase in carbon dioxide production associated with pregnancy. This is probably because the total FGF determined by body weight and given during Caesarean section anaesthesia is 15-20 per cent higher than nonpregnant levels, due to the weight gain associated with pregnancy. A FGF of 100 ml X kg-1 of pregnant weight/min maintains PaCO2 of 4.44 kPa predelivery, which is in the desirable range of PaCO2 during Caesarean section.     

A comparison of carbon dioxide monitoring and oxygenation between facemask and divided nasal cannula

The divided nasal cannula is a device recently released in Australia that couples oxygen delivery and end-tidal carbon dioxide (PETCO2) monitoring. This study compares the accuracy of PETCO2 measurements by the divided nasal cannula and those measured by a modified facemask (as currently used in this institution), with arterial partial pressure of carbon dioxide (PaCO2). In this crossover study, 30 patients who had arterial lines as part of their routine monitoring were given oxygen via nasal cannula and facemask preoperatively. The PETCO2 was measured with each device and a simultaneous PaCO2 and PaO2 measured after equilibration. The results demonstrate a significant difference between the PETCO2 as measured by each technique. The divided nasal cannula more accurately reflects PaCO2 (mean arterial to end expired gradient of 5 mmHg) and provides a more representative trace when compared to a traditional facemask system. Both methods provided adequate oxygenation.     

Accuracy of end-tidal carbon dioxide monitoring using the NBP-75 microstream capnometer. A study in intubated ventilated and spontaneously breathing nonintubated patients

Arterial carbon dioxide partial pressure measurements using the NBP-75 microstream capnometer were compared with direct PaCO2 values in patients who were (a) not intubated and spontaneously breathing, and (b) patients receiving intermittent positive pressure ventilation of the lungs and endotracheal anaesthesia. Twenty ASA physical status I-III patients, undergoing general anaesthesia for orthopaedic or vascular surgery were included in a prospective crossover study. After a 20-min equilibration period following the induction of general anaesthesia, arterial blood was drawn from an indwelling radial catheter, while the end-tidal carbon dioxide partial pressure was measured at the angle between the tracheal tube and the ventilation circuit using a microstream capnometer (NBP-75, Nellcor Puritan Bennett, Plesanton, CA, USA) with an aspiration flow rate of 30 mL min(-1). Patients were extubated at the end of surgery and transferred to the postanaesthesia care unit, where end-tidal carbon dioxide was sampled through a nasal cannula (Nasal FilterLine, Nellcor, Plesanton, CA, USA) and measured using the same microstream capnometer. In each patient six measurements were performed, three during mechanical ventilation and three during spontaneous breathing. A good correlation between arterial and end-tidal carbon dioxide partial pressure was observed both during mechanical ventilation (r = 0.59; P = 0.0005) and spontaneous breathing (r = 0.41; P = 0.001); while no differences in the arterial to end-tidal carbon dioxide tension difference were observed when patients were intubated and mechanically ventilated (7. 3 +/- 4 mmHg; CI95: 6.3-8.4) compared to values measured during spontaneous breathing in the postanesthesia care unit, after patients had been awakened and extubated (6.5 +/- 4.8 mmHg; CI95: 5. 2-7.8) (P = 0.311). The mean difference between the arterial to end-tidal carbon dioxide tension gradient measured in intubated and non-intubated spontaneously breathing patients was 1 +/- 6 mmHg (CI95: -11-+13). We conclude that measuring the end-tidal carbon dioxide partial pressure through a nasal cannula using the NBP-75 microstream capnometer provides an estimation of arterial carbon dioxide partial pressure similar to that provided when the same patients are intubated and mechanically ventilated.     

不同潮气量及呼吸频率对腹腔镜手术患者呼吸、循环功能的影响

目的:比较不同潮气量及呼吸频率时腹腔镜手术患者呼吸、循环功能的影响.方法:随机将30例ASA Ⅰ～Ⅱ级的患者均分为3组,呼吸频率分别为12次/min(A组)、16次/min(B组)、20次/min(C组),3组均采用容量控制(VCV)模式,分钟通气量为120ml/kg.气管插管静脉麻醉.记录各组气腹前(To)、气腹后2...     

End-tidal to arterial oxygen tension difference as an oxygenation index

BACKGROUND: "Ideal" alveolar oxygen tension (PAO2) is a calculated entity and the alveolar-arterial oxygen tension difference (PA-aO2) is used to evaluate gas exchange function of the lungs. Accurate calculations of PAO2 necessitate measurements of the respiratory exchange ratio (RER), which is less frequently done, and most often approximations are made. The measured end-tidal oxygen tension (PETO2) is a reflection of the alveolar oxygen tension. The aim was to study the relationship between PAO2 and PETO2, and to see whether the end-tidal to arterial oxygen tension difference (PET-aO2) could give the same information about lung function as PA-aO2. METHODS: Twenty patients admitted for cardio-pulmonary exercise tests were studied. They bicycled for 4 min at each work load until maximum work load was reached. Arterial blood gases were analysed before, after 4 min at each work load, at maximum work load and after 2 min of recovery. A metabolic computer measured mixed expired gas concentrations. End-tidal gas concentrations were measured with a side stream gas analyser. RESULTS: We measured major increases in oxygen uptake, carbon dioxide elimination and RER. PAO2 and PETO2 increased at maximum exercise and during recovery. PAO2 and PETO2 were closely correlated during the study, through great changes in oxygen uptake and RER (r=0.88). When correction was made for wet gas the median difference was 0.12 kPa. CONCLUSIONS: At ambient air (FIO2=0.21), PET-aO2 as a respiratory index may give equivalent information to PA-aO2, without the need for measurements of mixed expired gas tensions or the hazard of an assumed RER.     

Is end-tidal CO2 an accurate measure of arterial CO2 during laparoscopic procedures in children and neonates with cyanotic congenital heart disease?

BACKGROUND/PURPOSE: Children with cyanotic congenital heart disease (CCHD) may require laparoscopic procedures. There are no data on the ability of capnography to predict arterial carbon dioxide concentrations (PaCO2) in patients with CCHD during pneumoperitoneum. METHODS: Seven patients (age 1 to 35 months) with CCHD undergoing laparoscopic Nissen fundoplication are presented. Standard general endotracheal anesthesia was administered. The operations were performed either by or in consultation with the cardiac anesthesia team. During each case, concomitant PaCO2 and end-tidal carbon dioxide (ETCO2) measurements were made via an arterial line and capnograph before and after insufflation of the abdomen. The PaCO2-ETCO2 gradients before and during pneumoperitoneum were then compared using a paired Student's t test. RESULTS: There was a statistically significant increase in the PaCO2-ETCO2 gradient (5.7 v 13.4) after insufflation compared with baseline (P <.015). CONCLUSIONS: These preliminary results show that ETCO2 is not a reliable monitor of PaCO2 in patients with CCHD undergoing laparoscopic procedures. The authors feel that close monitoring, including arterial blood gas measurements, and an experienced anesthesia team are necessary to perform laparoscopic procedures in patients with CCHD.     

Pigs are not a reliable experimental model in the study of the haemodynamic and respiratory effects of CO2 pneumoperitoneum

BACKGROUND: Haemodynamic and respiratory effects of a CO2 pneumoperitoneum (intra-abdominal pressure = 12 mmHg) associated to a head-up position(15 degrees ) were studied in 20 pigs using a Swan-Ganz catheter and the Single Breath Test for CO2. The pneumoperitoneum induced a moderate rise in mean arterial pressure (+17%) (P<0.001) without any variation in heart rate, cardiac output and systemic vascular resistances. RESULTS: The following respiratory effects were observed: an increase in PaCO2 (+20%) (P<0.001), PE'CO2 (+31%) (P<0.001), expired volume of CO2 (+28%) (P<0.001), arterial to end-tidal CO2 gradient (+80%) (P<0.001) and alveolar dead space (+40%) (P<0.001) occured. Alveolar ventilation remained stable. Finally and contrary to healthy human patient, intraperitoneal CO2 insufflation in pig induced slight haemodynamic changes and major respiratory modifications. CONCLUSION: Thus, our data do not support the conclusion that the pig is a reliable experimental model for studying the pathophysiology of CO2 pneumoperitoneum-induced changes in haemodynamic and respiratory parameters, in human patients.     

CO2气腹对中老年直肠癌行腹腔镜手术患者呼吸和循环系统的影响

摘要为保证中老年直肠癌腹腔镜手术的安全,观测CO2气腹对呼吸和循环系统的影响,选择50例中老年择期行直肠癌腹腔镜手术患者,术中采用气管插管静脉复合结合连续硬膜外麻醉。行腹腔镜手术时,监测心率（HR）、平均动脉血压（MAP）、心电图（ECG）、呼吸频率（RR）、潮气量（VT）、气道压力（PAw）、血氧饱和度（SPO2）、呼气末二氧化碳分压（PetCO2）、动脉血氧分压（PaO2）、动脉二氧化碳分压（PaCO2）。结果显示,患者行CO2气腹前各项指标均在正常范围,CO2气腹后5min、15min的HR增快,MAP、PAw、PETCO2、PaCO2均升高。结果表明,CO2气腹对中老年直肠癌腹腔镜手术者呼吸、循环系统影响很大,因此,术中必须严密监测,备好抢救药品,对中老年合并心肺疾病者更应注意。     

Hypercarbia during carbon dioxide pneumoperitoneum.

Patients with cardiopulmonary insufficiency undergoing laparoscopic surgery with carbon dioxide (CO2) pneumoperitoneum may retain CO2 resulting in clinically significant respiratory acidosis. A canine model of pulmonary emphysema induced by papain inhalation was utilized to evaluate the respiratory effects of both CO2 and helium pneumoperitoneum. Prior to papain inhalation and 5 and 8 weeks after initial treatment under general anesthesia, mechanical ventilation was adjusted to maintain the end-tidal CO2 (ETCO2) at 40 mm Hg during baseline and pneumoperitoneum physiologic monitoring periods. Utilizing an analysis of variance, hemodynamic and respiratory physiologic parameters were compared. In this canine model, all dogs demonstrated consistent hypercarbia during CO2 pneumoperitoneum prior to papain treatments, but CO2 retention was significantly increased in the emphysematous state. The occurrence of hypercarbia during CO2 pneumoperitoneum may be underestimated by ETCO2 monitoring as was revealed by an increased PaCO2 (arterial carbon dioxide pressure)-ETCO2 gradient with an increasing time interval between papain exposure and period of physiologic monitoring. Irrespective of the pulmonary condition of the dog, helium pneumoperitoneum did not produce any hypercarbic or acidic changes when compared with the concomitant baseline period of dogs prior to the induction of pneumoperitoneum, thus suggesting that helium pneumoperitoneum may be a reasonable alternative in patients at risk for CO2 retention.     

Intermittent CPAP: A New Mode of Ventilation during General Anesthesia

Background: Airway pressure-release ventilation provides ventilation comparable to controlled mechanical ventilation (CMV), but with lower peak airway pressures and less deadspace ventilation. To obtain these advantages for patients administered general anesthesia, the authors (1) designed a mode similar to airway pressure-release ventilation, intermittent continuous positive airway pressure (CPAPI), and compared its efficiency with that of CMV; and (2) assessed the accuracy of end-tidal carbon dioxide tension (PET (CO)2) as a monitor of the partial pressure of carbon dioxide in arterial blood (PaCO2) during CPAPI compared with during CMV.

Methods: Twenty anesthetized, tracheally intubated patients received baseline CMV that produced a PETCO2 of approximately 35 mmHg and a pulse oximetry value > 90%. Patients were assigned to undergo alternating trials of CMV and CPAPI. During CPAPI, CPAP was applied to the airway, removed for 1 s, and reapplied at a rate equal to the ventilator rate during CMV. The difference between the carbon dioxide tension in arterial blood and end-tidal gas [P(a - ET)CO2] and the calculation of PaCO2/minute ventilation quantified the efficiency of ventilation. Data were summarized as mean +/- SD and compared using the Student's test.

Results: Peak airway pressure (13 +/- 2 vs. 23 +/- 5 cm H2 O; P < 0.001) and minute ventilation (3.5 +/- vs. 4.6 +/- 1.2 l/min; P < 0.0001) were lower during CPAPI than during CMV. The value for PaCO2/minute ventilation (11.1 +/- 2.9 vs. 7.9 +/- 2.6 mmHg [middle dot] 1-1 [middle dot] min-1; P < 0.0001) was greater during CPAPI. P(a - ET)CO2 was always greater during CMV (6.3 +/- 1.6 vs. 1.7 +/- 0.9 mmHg; P < 0.0001) and was never > 3.5 mmHg during CPAPI.     

Pressure support ventilation during inhalational induction with sevoflurane and remifentanil in adults

BACKGROUND AND OBJECTIVE: The purpose of this prospective randomized study was to assess the value of pressure support ventilation during inhalational induction with sevoflurane in adult patients. METHODS: Thirty-five adult patients, ASA I-II and scheduled for ear nose throat surgery were studied. Vital capacity induction with 8% sevoflurane in 8 L min-1 oxygen was performed. Pressure support ventilation was used in Group 1 with pressure set at 15 cmH2O. In Group 2, patients breathed spontaneously. After 2 min, sevoflurane was set to 3% and remifentanil 1 microg kg(-1) was injected over 2 min followed by an infusion of 0.1 microg kg(-1) min(-1). Two minutes after the end of the bolus, intubation was performed. Bispectral index, oxygen saturation, respiratory rate, end-tidal carbon dioxide, expired tidal volume and expired sevoflurane concentration were recorded every minute. RESULTS: Eighteen patients were included in Group 1 and 17 in Group 2. Saturation, respiratory rate and end-tidal carbon dioxide were similar in the two groups. Expired tidal volume was significantly higher and bispectral index values significantly lower in Group 1. Intubating conditions were better in Group 1. CONCLUSIONS: Pressure support ventilation provides both better ventilation and deeper level of anaesthesia during inhalation induction with sevoflurane.     

Haemodynamic changes during low-pressure carbon dioxide pneumoperitoneum in young children

BACKGROUND: Both mechanical and pharmacological effects may contribute to the haemodynamic consequences of carbon dioxide (CO2) pneumoperitoneum. The aim of the present study was to evaluate the haemodynamic effects of low-pressure pneumoperitoneum [intra-abdominal pressure (IAP) 5 mmHg] in young children (< 3 years). METHODS: Thirteen children, aged 6-36 months, ASA physical status I-III, who were scheduled for laparoscopic fundoplication for gastro-oesophageal reflux were investigated in the head-up position (10 degrees ). Noninvasive thoracic electrical bioimpedance cardiac index (CI), stroke volume index (SVI), heart rate (HR), mean arterial pressure (MAP) and peak inspiratory pressure (PIP) were recorded, together with PetCO2 and PaCO2 at five time points: before insufflation, 20, 35 and 70 min after start of CO2 insufflation and 12 min after desufflation. During insufflation, minute ventilation was not adjusted and the IAP was maintained at 5 mmHg. RESULTS: During insufflation, PetCO2 increased from 29 +/- 4 to 37 +/- 5 mmHg (P < 0.001) and PaCO2 increased from 31 +/- 4 to 39 +/- 5 mmHg (P < 0.01). CI increased from 2.39 +/- 0.86 to 2.92 +/- 0.94 l x min-1 x m2 (P < 0.01), HR increased from 108 +/- 10 to 126 +/- 22 b x min-1 (P < 0.01), MAP increased from 52 +/- 10 to 63 +/- 9 (P < 0.05) and PIP increased from 16 +/- 3 to 18 +/- 3 cm H2O (P < 0.001). There were no changes in SVI and arterial oxygen saturation. CONCLUSIONS: We conclude that low-pressure CO2 pneumoperitoneum (with IAPs not exceeding 5 mmHg) for laparoscopic fundoplication in infants and children does not decrease their cardiac index.     

Arterial to end-tidal carbon dioxide tension difference during anaesthesia in early pregnancy

Sixteen patients requiring general anaesthesia for termination of pregnancy by dilatation and evacuation of the uterus were studied. Arterial and end-tidal carbon dioxide tensions were determined during anaesthesia. The mean arterial to end-tidal carbon dioxide tension difference was 0.07 kPa (-0.02-0.16, 5-95 per cent confidence limits). These results were similar to those observed during Caesarean section and those during anaesthesia for post-delivery tubal ligations. The physiological changes such as increased cardiac output, haemodilution, and increased blood volume which manifest by 12 weeks of gestation probably result in a reduced (a-E')PCO2 value.