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

Evaluation of Arterial to End-tidal Carbon Dioxide Pressure Differences during Laparoscopic Renal Surgery in the Lateral Decubitus Position

Background:

End-tidal carbon dioxide (PEtCO₂) is a noninvasive reliable technique to measure arterial partial pressure of carbon dioxide (PaCO2) in the body under general anesthesia. However, gradient between PaCO₂ and PEtCO₂ (P[a-Et] CO₂) is influenced by many factors.

Aims:

In the present study, we evaluated the changes in P (a-Et) CO₂ for laparoscopic donor nephrectomy in lateral decubitus position (LDP).

Settings and Design:

This was an observational, double-blinded, tertiary care center-based study.

Methods:

Thirty-one American Society of Anesthesiologists Class I and Class II patients of either sex undergoing laparoscopic donor nephrectomy in LDP under general anesthesia were included. An arterial cannula was inserted, PaCO₂ was measured at eight predesignated time intervals, and PEtCO₂ was also noted at the corresponding time period.

Statistical Analysis:

Data were analyzed using a two-way analysis of variance for repeated measurements using one dependent variable and one within-subject factor (time). Quantitative data were presented as mean ± standard deviation or median and interquartile range, as appropriate.

Results:

The mean P (a-Et) CO₂ gradient was 5.67 ± 1.36 mmHg 10 min after induction of anesthesia in the supine position (T1a). Ten minutes after LDP, P (a-Et) CO₂ gradient was 7.38 ± 1.45 mmHg (T1b) and was higher than T1a. The P (a-Et) CO₂ values 10 min after release of pneumoperitoneum and 10 min after making the patient supine were significantly higher than the T1a value. The highest value of P (a-Et) CO₂ gradient was at 30 min after creation of pneumoperitoneum (T30), i.e., 9.99 ± 1.70 mmHg. Pearson's correlation coefficient showed that the degree of correlation varied considerably during surgery due to interindividual variability (R² T1a vs. T60 was 0.61 vs. 0.17).

Conclusions:

PEtCO₂ does not reliably predict PaCO₂ in healthy patients scheduled for laparoscopic renal surgery in LDP.

Anaesthetic considerations for laparoscopic surgery in neonates and infants: a practical review

Minimally invasive surgery is being applied to an increasing number of neonates and infants undergoing abdominal surgeries. Knowledge of specific implications, patient's health status and pathophysiological changes induced by the surgery allow the anaesthesiologist to provide safe anaesthesia to these high-risk patients. This chapter describes the specific pathophysiological effects, peri-operative management, major complications and contraindications related to endoscopic procedures.

Monitoring gaseous exchange: implications for nursing care

The purpose of this study is to examine whether a relationship exists between arterial and end-tidal carbon dioxide tension (PaCO2 and PETCO2 respectively) in patients admitted to intensive care units (ICUs), and what the implications it has for nursing care. PaCO2 and PETCO2 are indicators of ventilatory adequacy which is an important aspect of respiratory function. These measures of carbon dioxide tension are obtained via invasive and non-invasive monitoring tools. Measurement of PETCO2 has only recently been introduced into ICUs and its usefulness in these environments is open to debate. A population of 30 intubated patients had 214 simultaneous measurements of PaCO2 and PETCO2 taken over a period of 10 months. The findings indicate that, despite strong significant correlations, PETCO2 cannot be used safely as a substitute for PaCO2 as the arterial/end-tidal carbon dioxide gradient is not constant, nor does capnography provide a consistently reliable indicator of PaCO2.

Regional anesthesia for laparoscopy

A variety of laparoscopic procedures can be performed on patients under regional anesthesia. Diagnostic laparoscopy in elective and emergency patients, pain mapping, laparoscopy for infertility, and tubal sterilization are some examples. The key benefits of regional anesthesia include less emesis, less postoperative pain, shorter postoperative stay, improved patient satisfaction, and overall safety. Regional techniques, such as rectus sheath blocks, inguinal blocks, and caudal blocks, are useful adjuncts to general anesthesia and facilitate postoperative analgesia. Other techniques, such as spinal and epidural anesthesia, and combination of the two, are suitable as a sole anesthetic technique for laparoscopy. The physiologic changes during laparoscopy in the awake patient appear to be tolerated well under regional anesthesia. It is reasonable to assume that with advances in instrumentation and surgical techniques, the role of laparoscopy will increase in the future. The benefits conferred by regional anesthesia make it an attractive option to general anesthesia for many patients and procedures. Successful implementation of regional anesthesia is an important determinant of how anesthesiologists, surgeons, and surgical facilities cope with new challenges. In the future, it could be possible to provide "walk-in/walk-out" regional anesthesia with a real possibility of fast tracking patients through the recovery process after ambulatory surgery. For maximal patient safety, however, facilities offering regional anesthesia must have appropriately trained anesthesia personnel and the equipment necessary for monitoring and providing full resuscitation in the event of complications or a need to convert to general anesthesia.

Anesthesia for radical prostatectomy, cystectomy, nephrectomy, pheochromocytoma, and laparoscopic procedures

This article presents some of the more salient aspects of the anesthetic management of the common major renal surgical procedures and discusses the physiology and anesthetic implications of minimally invasive laparoscopic urologic surgery.

Experimental study of effect of embolism of different laparoscopy insufflation gases

BACKGROUND AND PURPOSE

Whilst carbon dioxide is the gas generally used for insufflation during laparoscopy, several studies have reported adverse effects specifically associated with its use. These effects may be attributable to chemical, metabolic, or immunologic effects specific to CO2. Because helium is chemically, physiologically, and pharmacologically inert, it has been suggested as a possible substitute insufflation gas. However, there has been concern about the potential implications of venous gas embolism during helium insufflation. The aim of this study was to examine the physiological effect of the intravenous injection of He and CO2 in an experimental model.

MATERIALS AND METHODS

Eleven domestic white pigs were randomly allocated to receive multiple intravenous injections of increasing volumes of either CO2 or He gas. Cardiorespiratory function was measured, and the intravenous volumes of gas that resulted in cardiac arrest were determined.

RESULT

Cardiorespiratory functional measures returned to normal quicker after CO2 than after He injection. Helium injection quickly overwhelmed the animal's ability to compensate and resulted in death at a lower volume than did CO2 injection.

CONCLUSIONS

Gas embolism during He insufflation is more likely to be lethal than is CO2 embolism. This scenario is most likely following Veress needle insertion into a large vein. Therefore, if He is to be used for insufflation during clinical laparoscopy, the possibility of venous injection should be minimized by avoiding Veress needle use. Further investigation of the safety of He insufflation is warranted before a role during clinical laparoscopy can be recommended.

Capnography monitoring during neurosurgery: reliability in relation to various intraoperative positions

In neurosurgery, estimation of PaCO2 from PETCO2 has been questioned. The aim of this study was to reevaluate the accuracy of PETCO2 in estimating PaCO2 during neurosurgical procedures lasting >3 h and to measure the effect of surgical positioning on arterial to end-tidal CO2 gradient (P[a-ET]CO2) over time. One hundred four neurosurgical patients classified into four groups (supine [SP], lateral [LT], prone [PR], sitting [ST]) were included in a prospective study. PaCO2, PETCO2, and P(a-ET)CO2 were measured after induction of anesthesia (T0), after positioning (T1), each following hour (T2, T3, T4), and at the end of the procedure after return to the SP position (T5). Data are expressed as the mean +/- SD, and statistical analysis used linear regression, the Bland-Altman method, and analysis of variance. The mean durations of positioning and surgery were 4.1+/-1 h and 3.7+/-1.3 h, respectively. We performed 624 simultaneous measurements of PaCO2 (33+/-5 mm Hg) and PETCO2 (27+/-4 mm Hg), leading to a mean P(a-ET)CO2 of 6+/-4 mm Hg. P(a-ET)CO2 of the LT group (7+/-3 mm Hg) was larger (compared with the SP, PR, and ST groups) because of a lower PETCO2 (26+/-4 mm Hg). Negative P(a-ET)CO2 (PETCO2 > PaCO2) occurred 22 times, only in the SP (n = 9) and ST groups (n = 13). Changes in opposite directions of PETCO2 and PaCO2 between two successive measurements were found in 26% of the cases. Correlation coefficients in the four groups (PaCO2 versus PETCO2) were not in good agreement (0.46 to 0.62; P < 0.001). The mean bias was between 5 and 7 mm Hg. The superior (13-15 mm Hg) and inferior (-5 to 0 mm Hg) limits of agreement were too large to expect PETCO2 to replace PaCO2. In conclusion, during neurosurgical procedures of >3 h, capnography should be performed with regular analysis of arterial blood gases for optimal ventilator adjustment.

IMPLICATIONS

This study, which aimed to reevaluate the ability of PETCO2 to estimate PaCO2 during neurosurgical procedures according to surgical position, indicates that PETCO2 cannot replace PaCO2 for the following reasons: scattering of individual values; occurrence of negative arterial to end-tidal CO2 gradient (P[a-ET]CO2; PaCO2 and PETCO2 variations in opposite directions; large changes in P(a-ET)CO2 between two samples; and instability of P(a-ET)CO2 over time.

Comparative carbon dioxide output through injured and noninjured peritoneum during laparoscopic procedures

Tension pneumoperitoneum may force gas into a small injured vessel if the opening is kept patent by surrounding tissues. However, the amount of carbon dioxide (CO2) that penetrates through injured or noninjured peritoneum has not been systematically determined. In 25 patients undergoing elective laparoscopic ultrasonography and cholecystectomy, CO2 output (VCO2) and O2 uptake (VO2) were measured at baseline and during anesthesia, pneumoperitoneum, laparoscopic surgical procedure (Surgery), and after hemostasis of the surgical field (Postsurgery). Before anesthesia, VCO2/BSA and VO2/BSA were 97.7 +/- 11.3 and 116.0 +/- 10.0 ml x min(-1) x m(-2), respectively. During anesthesia, they fell to 72.3 +/- 6.0 and 89.8 +/- 7.6 ml x min(-1) x m(-2), respectively (p < 0.05). VCO2/BSA increased to 96.0 +/- 11.1 at pneumoperitoneum (p < 0.05) and increased further to 126.1 +/- 11.0 ml x min(-1) x m(-2) at Surgery. It fell to 111.7 +/- 10.9 ml x min(-1) x m(-2) Postsurgery. VO2/BSA remained unchanged during pneumoperitoneum. Minute volume increased from 2.24 +/- 0.20 in anesthesia to 2.89 +/- 0.25, 4.01 +/- 0.32, and 3.46 +/- 0.28 L x min(-1) x m(-2) during pneumoperitoneum, Surgery, and Postsurgery, respectively, to maintain PaCO2. We conclude that the amount of CO2 absorbed following pneumoperitoneum prior to surgery is lower than that during Surgery or Postsurgery. The amount of CO2 absorbed through the surgical field was 2.3 times higher than that through the nonsurgical field while that from the peritoneum after hemostasis of surgical field was 1.6 times higher.

Effects of carbon dioxide insufflation for laparoscopic cholecystectomy on the respiratory system

The changes occurring in total respiratory system, lung and chest wall mechanics, lung volume and gas-exchange during abdominal insufflation with carbon dioxide for laparoscopic cholecystectomy were studied. Using the technique of rapid airway occlusion during constant flow inflation together with an oesophageal balloon, we computed compliance and maximum resistance of the respiratory system, subsequently apportioning it into its lung and chest wall components. Maximum resistance of the respiratory system was further divided into airway resistance and the viscoelastic properties of the lung and the chest wall. In 10 patients (group 1), we measured respiratory system, lung and chest wall mechanics (compliance and resistance), functional residual capacity, end-tidal carbon dioxide tension and oxygen saturation. In addition, arterial blood gas analysis and end-tidal carbon dioxide tension were measured in a second group of 10 patients (group 2). Measurements, in both groups, were obtained in the reverse Trendelenburg position, at 15 min after the induction of anaesthesia, 5 min and 45 min after abdominal insufflation and at 15 min after abdominal deflation. Tidal volume, respiratory rate, inspiratory flow and the fraction of inspired oxygen were similar in both groups and maintained constant during the procedure. We found that abdominal carbon dioxide insufflation caused: a reduction in compliance of the respiratory system (both lung and chest wall components) and of functional residual capacity; a marked increase in the maximum resistance of the respiratory system (mainly due to increases in the viscoelastic properties of the lung and chest wall); no change in oxygenation, but an increase in the end-tidal carbon dioxide tension (which was correlated closely with the arterial carbon dioxide tension). These changes were not affected by the duration of anaesthesia.

General anesthesia using the laryngeal mask airway during brief, laparoscopic inspection of the peritoneum in children

The authors prospectively examined the cardiorespiratory changes seen with general anesthesia using the laryngeal mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children. Anesthesia consisted of halothane in 50% oxygen/air and a caudal epidural block. The patient was allowed to ventilate spontaneously without assistance. Baseline measurements of heart rate, systolic blood pressure (SBP), end-tidal CO2 (ETCO2), tidal volume, respiratory rate, and oxygen saturation were recorded every 1 min for 5 min prior to the start of laparoscopy and every minute during the laparoscopic procedure. A total of 15 patients were enrolled in the study ranging in age from 15 to 90 months (35.5 +/- 23.8 months) and in weight from 10 to 26.4 kg (14.9 +/- 4.9 kg). The length of the laparoscopy varied from 3 to 9 min (6.1 +/- 2.1 min). Although clinically insignificant, there was an increase in the heart rate from a baseline value of 141 +/- 9 to 148 +/- 9 beats/min (p = 0.0016) and in the SBP from a baseline value of 97 +/- 6 mm Hg to 101 +/- 7 mm Hg (p = 0.0087). The baseline tidal volume prior to the start of laparoscopy was 5.2 +/- 1.1 mL/kg and increased to 6.4 +/- 1.4 mL/kg during laparoscopy (p < 0.0001) while the respiratory rate increased from 32 +/- 4 to 40 +/- 6 breaths/min (p < 0.0001). ETCO2 increased from a baseline value of 47 +/- 6 to 53 +/- 6 torr (p = 0.0059). The maximum value of the ETCO2 was 55 torr or greater in 6 patients, exceeded 60 torr in 3 patients, with a maximum value of 63 torr. The increased ETCO2 returned to baseline within 2 to 7 min (4.7 +/- 1.5 min) following completion of the laparoscopy. There was no significant change in oxygen saturation. Our initial experience suggests that general anesthesia may be provided using the laryngeal mask during brief laparoscopic inspection of the peritoneum.

Ventilatory effects of laparoscopic cholecystectomy

BACKGROUND

During laparoscopic cholecystectomy the arterial-end-tidal CO2 gradient (Fa-ETCO2) has been variously shown to be unchanged, increased, decreased or even negative. The goal of this study was to evaluate Fa-ETCO2, and to determine the proper contribution of VECO2 and VA in regard to the increase of FETCO2.

METHODS

Ventilatory patterns were studied in 15 ASA 1-2 patients (mean age +/- SD: 48.5 +/- 15.0) undergoing laparoscopic cholecystectomy, with intraperitoneal CO2 insufflation limited to 12 mmHg, 15 degrees head-up position, during general anaesthesia and controlled ventilation. The following were studied before, during and after the pneumoperitoneum: FaCO2, FETCO2, nasopharyngeal temperature; dead space ventilation, and expired volumes using the Single Breath Test for CO2. VA was calculated as the alveolar fraction of expired VT multipled by the respiratory frequency.

RESULTS

During pneumoperitoneum it is shown that: 1) Fa-ETCO2 either decreases and becomes even negative (n = 8) (P < 0.01), or stays unchanged (n = 7), but never elevates; 2) VECO2 increases (peak value: +22.6%) (P < 0.01); 3) VA is unchanged, and 4) dead space ventilation, determined in 7 patients, remains unchanged.

CONCLUSION

We conclude that only exogenous CO2 loading, and not VA, can explain such increase in FETCO2 and FaCO2, in cases of limited CO2 insufflating pressure in ASA 1-2 patients.

Comparative stress hormone changes during helium versus carbon dioxide laparoscopic cholecystectomy

Laparoscopic surgery has been termed minimally invasive surgery by advocates of this technology. It has been demonstrated previously that using carbon dioxide for insufflation produces a respiratory acidosis due to transperitoneal absorption of gas. Insufflation with helium does not create this acidosis. We questioned whether laparoscopic surgery would elicit a stress response and whether the absence of acidosis with helium might prevent or reduce the levels of stress hormones. Sixteen female patients undergoing laparoscopic cholecystectomy were randomly assigned to helium (n = 8) or CO2 (n = 8) insufflation. Serum cortisol, epinephrine, and norepinephrine were measured preoperatively, after induction of anesthesia but before insufflation, at 45 min of surgery, and after desufflation. There were increases in epinephrine, norepinephrine, plasma cortisol, and urine cortisol at 45 min and at the conclusion of the procedure over the preoperative value. With ANOVA, each variable showed significant increases from preoperative values, at 45 min, and at the end of the case. Except for the increased epinephrine when helium was used, there were no significant differences in the other variables between helium and CO2. Laparoscopic cholecystectomy produces significant increases in stress hormone levels. Prevention of acidosis with helium insufflation does not appear to protect against increases in stress hormones. Epinephrine levels with helium insufflation are higher than with CO2, and elevations in stress hormones suggest that laparoscopic cholecystectomy is not physiologically minimally invasive.

Does increasing end-tidal carbon dioxide during laparoscopic cholecystectomy matter?

To examine the adverse effects of peritoneal carbon dioxide (CO2) insufflation during laparoscopic cholecystectomy, both hemodynamic and respiratory alterations were continously monitored in 17 adult patients using noninvasive Doppler ultrasonography and a continuous spirometric monitoring device. During the surgery, which was performed under inhalational general anesthesia, intraabdominal pressure was maintained automatically at 10mmHg by a CO2 insufflator, and a constant minute ventilation, initially set to 30-33 mmHg of end-tidal CO2 (ETCO2), was maintained. Despite considerable depth of anesthesia, peritoneal CO2 insufflation induced a significant and immediate increase of mean blood pressure (+42%) and systemic vascular resistance (+62%), accompanied by a slight depression of cardiac index (-12%, nonsignificant), while the ETCO2 gradually increased and maximized around 30min following the initial CO2 insufflation. The stress of 10mmHg pneumoperitoneum was a major cause of hemodynamic changes during laparoscopic cholecystectomy. Some clinical strategies such as deliberate intraabdominal insufflation at the initial phase might be required to minimize these hemodynamic changes.

[Gynecologic laparoscopy with or without curare]

OBJECTIVE

To assess physiological changes and operating conditions during general anaesthesia with or without neuromuscular blockade in patients undergoing gynaecologic laparoscopy.

STUDY DESIGN

Prospective, randomized, double-blind study.

PATIENTS

Fifty non-obese patients, mean age 31 years, randomly allocated into either a group of 25 with curare (AC) or a group of 25 without curare (SC).

METHODS

All patients were anaesthetized with propofol (2.5 mg.kg-1), sufentanil (0.4 microgram.kg-1) midazolam (2 mg) and N2O-O2. In addition, those of the AC group were given atracurium 0.25 mg.kg-1 for intubation, followed by additional boluses to maintain twitch height < 10% of the control value. Blood pressure, heart rate, peak airway pressure, end-tidal carbon dioxide pressure were recorded before and during pneumoperitoneum maintained at a pressure of 15 mmHg. Operating conditions were assessed at 10-min intervals, using a four point scale.

RESULTS

In both groups, blood pressure and heart rate decreased following induction. The decrease in blood pressure was more important in the SC group at 5 min and before pneumoperitoneum (25 vs 15%); P < 0.05). The time course of PETCO2 and peak airway pressures were similar between groups. Operating conditions were not influenced by the muscle relaxant.

CONCLUSIONS

Neuromuscular blockade influences neither most of the clinical haemodynamic and respiratory changes induced by pneumoperitoneum for gynaecologic laparoscopy not the operating conditions.

The adverse hemodynamic effects of laparoscopic cholecystectomy

Recent studies suggest that significant physiologic derangements can occur during laparoscopic surgery. Eighteen patients admitted for laparoscopic cholecystectomy were studied. The mean age was 46.7 (range 19-78). A standard anesthetic technique, reverse Trendelenburg positioning, and an abdominal insufflation pressure of 15 mmHg with CO2 were used with all subjects. Central venous pressure (CVP) and arterial pressures were measured invasively. Stroke volume and cardiac index were calculated using quantitative transesophageal echocardiography. Baseline measurements were taken after induction. Additional measurements were taken at 15-min intervals throughout the procedure. There was a statistically significant increase in mean arterial pressure (15.9%), systolic blood pressure (11.3%), diastolic blood pressure (19.7%), and CVP (30.0%) from control baseline values. Significant decreases in stroke volume (29.5%) and cardiac index (29.5%) occurred within 30 min of the induction of pneumoperitoneum and positioning (P < 0.05, ANOVA). Laparoscopic cholecystectomy significantly and reversibly decreases cardiac performance. Compromised patients may be at increased risk for complications not previously recognized with this procedure.

General anesthesia by mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children

We prospectively examined the cardiorespiratory changes seen with general anesthesia by mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children. Anesthesia consisted of isoflurane in 50% oxygen/air and a caudal epidural block. The patient was allowed to ventilate spontaneously without assistance. Baseline measurements of heart rate, systolic/diastolic blood pressure (BP), end-tidal CO2 (PETCO2), tidal volume, respiratory rate, and oxygen saturation were recorded every 1 min for 5 min before the start of laparoscopy and every minute during the laparoscopic procedure. A total of 20 patients were enrolled in the study, ranging in age from 15 to 80 months (mean 40.8 months) and in weight from 10.5 to 27 kg (mean 15.9 kg). The length of the laparoscopy varied from 3 to 18 min (mean 6.9 min). No significant changes (increase or decrease of 20% from baseline) of heart rate or BP occurred. Oxygen saturation remained at 98%-100% throughout the procedure in all patients. The baseline tidal volume before the start of laparoscopy was 6.27 +/- 1.9 mL/kg and increased to 7.3 +/- 2.2 mL/kg during laparoscopy (p = 0.01). The baseline respiratory rate was 27.7 +/- 7.0 breaths/min and increased to 33.5 +/- 7.2 breaths/min during laparoscopy (p = 0.0001). PETCO2 increased from a baseline value of 37.5 +/- 6.5 to 44.6 +/- 6.8 mm Hg (p = 0.0001). The increase in PETCO2 was 10 or greater in 3 patients and exceeded 50 mm Hg in 3 patients, with a maximum value of 66 torr.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in end-tidal carbon dioxide during gynecologic laparoscopy: spontaneous versus controlled ventilation

STUDY OBJECTIVE

To study the changes in PETCO2 during spontaneous and controlled ventilation in patients undergoing gynecologic laparoscopy.

DESIGN

Randomized, unblinded study.

SETTING

Department of Gynecology, University Hospital, Linköping, Sweden; Central Hospital, Norrköping, Sweden.

PATIENTS

Forty healthy patients undergoing gynecologic laparoscopy.

INTERVENTIONS

Patients were divided into 4 groups: Group 1 breathed spontaneously via an endotracheal tube, while the other three groups underwent controlled ventilation to an initial PETCO2 of 3 kPa (22 mmHg) (Group 2), 4 kPa (30 mmHg) (Group 3), or 5 kPa (37 mmHg) (Group 4).

MEASUREMENTS AND MAIN RESULTS

PETCO2 levels were measured at fixed time intervals. Arterial blood gas analyses were done to compare the difference between PETCO2 and PaCO2. In Group 1, PETCO2 increased soon after insufflation and remained above 6 kPa (44 mmHg) throughout the procedure. In Groups 2, 3, and 4, PETCO2 also rose after insufflation, and an initial PETCO2 of 4 kPa (30 mmHg) was ideal, as all PETCO2 values were less than 5.5 kPa (41 mmHg). Occasional episodes of arrhythmia were seen in Group 1. However, no major adverse effects were observed in any of the groups.

CONCLUSIONS

In view of the high PETCO2 levels, spontaneous breathing should be avoided during gynecologic laparoscopy, and ventilation to an initial PETCO2 of 4 kPa (30 mmHg) is recommended during controlled ventilation.

Extraperitoneal endosurgical lymphadenectomy with insufflation in the staging of bladder and prostate cancer

A new technique of endosurgical pelvic lymph node dissection was performed for the staging of 10 prostate and 8 bladder cancers. The technique, involving an exclusive extraperitoneal space development with CO2 insufflation, is described in detail. Using the standard endosurgical (laparoscopic) equipment, we performed a complete bilateral ilio-obturator lymph node dissection in 15 patients (83%). In the remaining three patients, because of technical difficulties, only unilateral dissection was performed. The average operating time was 84 minutes. Morbidity was low (one instance of sepsis). Prospective assessment of CO2 homeostasis showed that arterial CO2 pressure (PaCO2) increased significantly but could be controlled by increasing minute ventilation output. Our results show that perioperative assessment of end-tidal CO2 partial pressure is necessary and sufficient for the adaptation of minute ventilation output. Two patients with prostate cancer had positive nodes. No intraoperative or postoperative morbidity related to the procedure was observed in patients submitted to radical surgery. Extraperitoneal endosurgical pelvic lymphadenectomy with CO2 insufflation is a rapid, safe, and effective method in the staging of urologic pelvic malignancies and represents an alternative to traditional open surgery as well as to conventional transperitoneal laparoscopic lymphadenectomy.

Anaesthesia for laparoscopic general surgery

Laparoscopic surgery minimises postoperative morbidity. Patient benefits include reduction in postoperative pain, better cosmetic result and quicker return to normal activities. Hospital stay is shortened resulting in a reduction in overall medical cost. The intraoperative requirements of laparoscopic surgery however can lead to serious physiological changes and complications. While there is a low but definite perioperative mortality rate associated with minor gynaecologic laparoscopic procedures, laparoscopic general surgical procedures are performed on older patients and patients with acute surgical conditions and are likely to be associated with a higher incidence of perioperative complications. The major problems during laparoscopic surgery are related to the cardiopulmonary effects of pneumoperitoneum, systemic carbon dioxide absorption, extraperitoneal gas insufflation, venous gas embolism and unintentional injuries to intra-abdominal structures. An appraisal of the potential problems is essential for optimal anaesthetic care of patients undergoing laparoscopic surgery. Appropriate anaesthetic techniques and monitoring facilitate surgery and allow early detection and reduction of complications. The need for rapid recovery and short hospital stay impose additional demands on the anaesthetist for skillful practice.

Capnometry and anaesthesia

In the last decade, capnography has developed from a research instrument into a monitoring device considered to be essential during anaesthesia to ensure patient safety. Hence, a comprehensive understanding of capnography has become mandatory for the anaesthetist in charge of patients in the operating room and in the intensive care unit. This review of capnography includes the methods available to determine carbon dioxide in expired air, and an analysis of the physiology of capnograms, which are followed by a description of the applications of capnography in clinical practice. The theoretical backgrounds of the effect of barometric pressure, water vapour, nitrous oxide and other factors introducing errors in the accuracy of CO2 determination by the infra-red technique, currently the most popular method in use, are detailed. Physiological factors leading to changes in end-tidal carbon dioxide are discussed together with the clinical uses of this measurement to assess pulmonary blood flow indirectly, carbon dioxide production and adequacy of alveolar ventilation. The importance of understanding the shape of the capnogram as well as end-tidal carbon dioxide measurements is emphasized and its use in the early diagnosis of adverse events such as circuit disconnections, oesophageal intubation, defective breathing systems and hypoventilation is highlighted. Finally, the precautions required in the use and interpretation of capnography are presented with the caveat that although no instrument will replace the continuous presence of the attentive physician, end-tidal carbon dioxide monitoring can be effective in the early detection of anaesthesia-related intraoperative accidents.