Anaesthesia for laparoscopic nephrectomy: Does end-tidal carbon dioxide measurement correlate with arterial carbon dioxide measurement?

Comparison of arterial to end-tidal carbon dioxide gradient P (a-ET)CO2 in volume versus pressure controlled ventilation in patients undergoing robotic abdominal surgery in the Trendelenburg position. A randomised controlled study

Background and Aims:

Robotic surgery is increasingly prevalent as an advancement in care. Steep head-down positions in pelvic surgery can increase the ventilation-perfusion mismatch and increase ventilatory requirements to offset carbon dioxide (CO₂) increases consequent to pneumoperitoneum. The primary objective was to assess the impact of two ventilatory strategies, volume versus pressure-controlled ventilation on the arterial to end-tidal carbon dioxide gradient P (a-ET)CO₂ in patients undergoing robotic surgery in the Trendelenburg position. The effects on alveolar to arterial oxygen gradient P (A-a)O₂, peak airway pressure (P_aw)_, dynamic compliance (C_dyn) and haemodynamics were also assessed.

Methods:

Fifty-one patients, 18-75 y, American Society of Anesthesiologists I-III undergoing robotic surgery in Trendelenburg position were randomised to volume-controlled ventilation (Group VCV) or pressure-controlled ventilation (Group PCV). The P (a-ET)CO₂ was measured at baseline T0, 10 min after Trendelenburg position T1, 2 h of surgery T2, 4 h T3 and at T_e, 10 min after deflation. The P (A-a) O₂, P_aw, C_dyn, heart rate and blood pressure were also measured at the same time.

Results:

The P (a-ET)CO₂ at T1, T2, T3 and at T_e was lower in Group PCV versus Group VCV. The P_aw was lower at T1, T2, and T3 and C_dyn higher at T3 and Te in Group PCV at comparable minute ventilation. Haemodynamics and P (A-a)O₂ were comparable between the groups.

Conclusion:

Pressure-controlled ventilation reduces P (a-ET)CO₂ gradient, P_aw and improves C_dyn but does not affect P (A-a) O₂ or haemodynamics in comparison to volume-controlled ventilation in robotic surgeries in the Trendelenburg position.

End-tidal carbon dioxide measurements as a surrogate to arterial carbon dioxide during pediatric laparoscopic surgeries: a prospective observational cohort study

BACKGROUND

Maintaining normocapnia during mechanical ventilation in anesthetized children during laparoscopic surgeries is highly recommended. There is a debate regarding the use of capnography (ETCO2) as a trend monitor for evaluation of arterial carbon dioxide levels (PaCO2). We analyzed the relationship between ETCO2 and PaCO2 with time in elective pediatric laparoscopic surgeries.

METHODS

This study was a prospective observational cohort analysis of 116 paired comparisons between PaCO2 and ETCO2 computed from 29 children (ASA I, 12-72 months). Arterial blood samples were withdrawn before, at 15 minutes and 30 minutes during pneumoperitoneum and 1 minute after deflation. ETCO2 value was recorded simultaneously, while arterial blood was withdrawn. PaCO2-ETCO2 relationship was evaluated by Pearson's correlation coefficients and Bland Altman Method of agreement.

RESULTS

Out of the 116 comparisons analyzed, a PaCO2-ETCO2 difference beyond 0 to ≤ 5 mmHg was recorded in 71 comparisons (61.2%) with negative difference in 34 comparisons (29.3%). A positive significant correlation between PaCO2 and ETCO2 was recorded before (r = 0.617, p = 0.000) and at 15 minutes (r = 0.582, p = 0.001), with no significant correlation at 30 minutes (r = 0.142, p = 0.461), either after deflation (r = 0.108, p = 0.577). Bland-Altman plots showed agreement between ETCO2 and PaCO2 before inflation with mean PaCO2-ETCO2 difference 0.14 ± 5.6 mmHg (limits of 95% agreement -10.84-11.2, simple linear regression testing p-value 0.971), with no agreement at 15 minutes (0.51 ± 7.15, -13.5-14.5, p = 0.000), 30 minutes. (2.62 ± 7.83, -12.73-17.97, p = 0.000), or after deflation (1.81 ± 6.56, -10.93-14.55, p = 0.015).

CONCLUSION

Usage of capnography as a trend monitor in pediatric laparoscopic surgeries may not be a reliable surrogate for PaCO2 levels.

TRIAL REGISTRATION

Clinical Trials. gov (Identifier: NCT03361657).

A prospective comparative study of arterial blood gas parameters in smoker versus non-smoker patients undergoing laparoscopic cholecystectomy

Background and Aims:

Smoking is a risk factor for postoperative pulmonary complications in patients undergoing general anaesthesia. These may get amplified with effects of pneumo-peritoneum and carbon dioxide (CO₂) insufflation during laparoscopic surgeries. Our aim was to compare metabolic and blood gas analysis of smokers versus non-smoker patients during laparoscopic surgeries under general anaesthesia.

Methods:

After permission from institutional review board, 60 patients undergoing laparoscopic cholecystectomy were divided into two groups, smokers and non-smokers (30 each). Along with baseline haemo-dynamic parameters, arterial blood gas sampling was done to assess and compare PCO₂, pH and bicarbonate (HCO₃) values at various time intervals with respect to pneumo-peritoneum creation, between smokers and non smokers.

Results:

Baseline systolic blood pressure was higher and oxygen saturation was significantly lower in smoker group. PCO₂ and end-tidal CO₂ were significantly higher in smokers at all intervals (P < 0.001). pH was significantly lower and HCO₃ higher, in smokers after creation of pneumo-peritoneum. Increase in PCO2 due to pneumo-peritoneum was higher in the smoker group (3.49 ± 8.5) mmHg versus non smoker (0.56 ± 4.86) mmHg, although statistically not significant. Change in pH and HCO₃ was similar between smokers and non-smokers.

Conclusion:

There is a significant difference in baseline arterial blood gas characteristics between smokers and non-smokers. Metabolic effects of CO₂ insufflation and increased intraabdominal pressure appears to be more enhanced in smokers.

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.