Scolaris Content Display Scolaris Content Display

Study flow diagram.
Figuras y tablas -
Figure 1

Study flow diagram.

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
Figuras y tablas -
Figure 2

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Figuras y tablas -
Figure 3

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Trial sequential analysis of nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum for cardiopulmonary complications. Analysis was performed with an event rate of 2.9% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The accrued sample size was so small that the trial sequential boundaries could not be drawn. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity‐adjusted required information size was 3781 participants, corresponding to 3.7% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.
Figuras y tablas -
Figure 4

Trial sequential analysis of nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum for cardiopulmonary complications. Analysis was performed with an event rate of 2.9% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The accrued sample size was so small that the trial sequential boundaries could not be drawn. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity‐adjusted required information size was 3781 participants, corresponding to 3.7% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.

Trial sequential analysis of nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum for surgical morbidity. Analysis was performed with an event rate of 2.8% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity adjusted required information size was 3919 participants, corresponding to 3.6% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.
Figuras y tablas -
Figure 5

Trial sequential analysis of nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum for surgical morbidity. Analysis was performed with an event rate of 2.8% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity adjusted required information size was 3919 participants, corresponding to 3.6% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.

Trial sequential analysis of helium pneumoperitoneum versus carbon dioxide pneumoperitoneum for cardiopulmonary complications. Analysis was performed with an event rate of 3.0% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity adjusted required information size was 3651 participants, corresponding to 3.5% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.
Figuras y tablas -
Figure 6

Trial sequential analysis of helium pneumoperitoneum versus carbon dioxide pneumoperitoneum for cardiopulmonary complications. Analysis was performed with an event rate of 3.0% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity adjusted required information size was 3651 participants, corresponding to 3.5% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.

Trial sequential analysis of helium pneumoperitoneum versus carbon dioxide pneumoperitoneum for serious adverse events. Analysis was performed with an event rate of 2.3% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity adjusted required information size was 4793 participants, corresponding to 2.7% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.
Figuras y tablas -
Figure 7

Trial sequential analysis of helium pneumoperitoneum versus carbon dioxide pneumoperitoneum for serious adverse events. Analysis was performed with an event rate of 2.3% (Pc) in the control group, a risk ratio reduction of 20%, alpha 5%, beta 20%, and observed diversity 0%. The cumulative Z‐curve did not cross the naive 5% statistical boundaries (red horizontal lines). The results showed that the observed diversity adjusted required information size was 4793 participants, corresponding to 2.7% of the total sample size in the included trials. Accordingly, the meta‐analysis did not support or refute an intervention effect as data were too few.

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 1 Cardiopulmonary complications.
Figuras y tablas -
Analysis 1.1

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 1 Cardiopulmonary complications.

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 2 Procedure‐related general complications.
Figuras y tablas -
Analysis 1.2

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 2 Procedure‐related general complications.

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 3 Analgesia requirements.
Figuras y tablas -
Analysis 1.3

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 3 Analgesia requirements.

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 4 Cardiopulmonary changes.
Figuras y tablas -
Analysis 1.4

Comparison 1 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 4 Cardiopulmonary changes.

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 1 Cardiopulmonary complications.
Figuras y tablas -
Analysis 2.1

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 1 Cardiopulmonary complications.

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 2 Pneumoperitoneum‐related serious adverse events.
Figuras y tablas -
Analysis 2.2

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 2 Pneumoperitoneum‐related serious adverse events.

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 3 Pain scores (cm) (first postoperative day).
Figuras y tablas -
Analysis 2.3

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 3 Pain scores (cm) (first postoperative day).

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 4 Analgesia requirements (morphine mg).
Figuras y tablas -
Analysis 2.4

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 4 Analgesia requirements (morphine mg).

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 5 Number of participants requiring analgesia.
Figuras y tablas -
Analysis 2.5

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 5 Number of participants requiring analgesia.

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 6 Cardiopulmonary parameters.
Figuras y tablas -
Analysis 2.6

Comparison 2 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 6 Cardiopulmonary parameters.

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 1 Cardiopulmonary complications.
Figuras y tablas -
Analysis 3.1

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 1 Cardiopulmonary complications.

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 2 Pneumoperitoneum‐related serious adverse events.
Figuras y tablas -
Analysis 3.2

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 2 Pneumoperitoneum‐related serious adverse events.

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 3 Pain scores (cm) (first postoperative day).
Figuras y tablas -
Analysis 3.3

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 3 Pain scores (cm) (first postoperative day).

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 4 Hospital costs (CNY).
Figuras y tablas -
Analysis 3.4

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 4 Hospital costs (CNY).

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 5 Cardiopulmonary parameters.
Figuras y tablas -
Analysis 3.5

Comparison 3 Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum, Outcome 5 Cardiopulmonary parameters.

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 1 Cardiopulmonary complications.
Figuras y tablas -
Analysis 4.1

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 1 Cardiopulmonary complications.

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 2 Procedure‐related general complications.
Figuras y tablas -
Analysis 4.2

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 2 Procedure‐related general complications.

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 3 Pneumoperitoneum‐related serious adverse events.
Figuras y tablas -
Analysis 4.3

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 3 Pneumoperitoneum‐related serious adverse events.

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 4 Mortality.
Figuras y tablas -
Analysis 4.4

Comparison 4 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 4 Mortality.

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 1 Cardiopulmonary complications.
Figuras y tablas -
Analysis 5.1

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 1 Cardiopulmonary complications.

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 2 Procedure‐related general complications.
Figuras y tablas -
Analysis 5.2

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 2 Procedure‐related general complications.

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 3 Pneumoperitoneum‐related serious adverse events.
Figuras y tablas -
Analysis 5.3

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 3 Pneumoperitoneum‐related serious adverse events.

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 4 Mortality.
Figuras y tablas -
Analysis 5.4

Comparison 5 Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 4 Mortality.

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 1 Cardiopulmonary complications.
Figuras y tablas -
Analysis 6.1

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 1 Cardiopulmonary complications.

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 2 Procedure‐related general complications.
Figuras y tablas -
Analysis 6.2

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 2 Procedure‐related general complications.

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 3 Pneumoperitoneum‐related serious adverse events.
Figuras y tablas -
Analysis 6.3

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 3 Pneumoperitoneum‐related serious adverse events.

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 4 Mortality.
Figuras y tablas -
Analysis 6.4

Comparison 6 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data), Outcome 4 Mortality.

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 1 Cardiopulmonary complications.
Figuras y tablas -
Analysis 7.1

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 1 Cardiopulmonary complications.

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 2 Procedure‐related general complications.
Figuras y tablas -
Analysis 7.2

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 2 Procedure‐related general complications.

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 3 Pneumoperitoneum‐related serious adverse events.
Figuras y tablas -
Analysis 7.3

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 3 Pneumoperitoneum‐related serious adverse events.

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 4 Mortality.
Figuras y tablas -
Analysis 7.4

Comparison 7 Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data, Outcome 4 Mortality.

Summary of findings for the main comparison. Nitrous oxide versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery

Nitrous oxide versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery

Patient or population: people undergoing laparoscopic general abdominal or gynaecological pelvic surgery under general anaesthesia

Setting: secondary and tertiary care

Intervention: nitrous oxide pneumoperitoneum

Comparison: carbon dioxide pneumoperitoneum

Outcomes

Anticipated absolute effects* (95% CI)

Relative effect
(95% CI)

No of participants
(studies)

Quality of the evidence
(GRADE)

Comments

Risk with carbon dioxide pneumoperitoneum

Risk with nitrous oxide pneumoperitoneum

Cardiopulmonary complications

Follow‐up: 0 to 1 month

29 per 1000

57 per 1000
(11 to 302)

RR 2.00
(0.38 to 10.43)

140
(2 studies)

⊕⊝⊝⊝
Very low1,2

Trial sequential analysis showed a diversity‐adjusted required information size of 3781 participants to support or refute nitrous oxide pneumoperitoneum.

Procedure‐related general complications

Follow‐up: 0 to 1 month

28 per 1000

28 per 1000
(5 to 160)

RR 1.01
(0.18 to 5.71)

143
(2 studies)

⊕⊝⊝⊝
Very low1,2

Trial sequential analysis showed a diversity‐adjusted required information size of 3919 participants to support or refute nitrous oxide pneumoperitoneum.

Pneumoperitoneum‐related serious adverse events

Follow‐up: 0 to 1 month

See comment

See comment

Not estimable

196
(3 studies)

⊕⊕⊝⊝
Low3,4

None of the studies reported any pneumoperitoneum‐related serious adverse events.

Mortality

Follow‐up: 0 to 1 month

See comment

See comment

Not estimable

196
(3 studies)

⊕⊕⊝⊝
Low3,4

None of the studies reported any deaths.

Quality of life

None of the studies reported quality of life.

Pain scores (first postoperative day)

VAS, lower score indicates less pain.
Scale: 0 cm to 10 cm

Follow‐up: 1 day

See comment

See comment

Not estimable

140
(2 studies)

⊕⊝⊝⊝
Very low3,4,5

Neither trials reported the standard deviation for pain scores on the VAS scale. Substantial clinical heterogeneity in between the 2 studies.

Analgesia requirements

Follow‐up: 1 week

The mean analgesia requirement in the carbon dioxide pneumoperitoneum was 54.4 mg of oxycodone and 2.0 tablets/24 hours of ibuprofen

The mean analgesia requirement in the nitrous oxide pneumoperitoneum was 0.69 standard deviations lower
(1.42 lower to 0.04 higher)

SMD ‐0.69
(‐1.42 to 0.04)

193
(3 studies)

⊕⊝⊝⊝
Very low3,4,6

Hospital costs

None of the studies reported costs.

*The basis for the assumed risk is the mean comparison group proportion in the studies. The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

CI: confidence interval; RR: risk ratio; SMD: standardised mean difference; VAS: visual analogue scale.

GRADE Working Group grades of evidence
High quality: We are very confident that the true effect lies close to that of the estimate of the effect.
Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect.
Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect.

1 Downgraded two levels for very serious risk of bias.

2 Downgraded one level for serious imprecision (the confidence interval of risk ratio overlapped 0.75 and 1.25, and small sample size).

3 Downgraded one level for serious imprecision (small sample size).

4 Downgraded one level for serious risk of bias.

5 Downgraded one level for indirectness.

6 Downgraded one level for severe inconsistency (substantial heterogeneity as indicated by the I2 statistic).

Figuras y tablas -
Summary of findings for the main comparison. Nitrous oxide versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery
Summary of findings 2. Helium versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery

Helium versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery

Patient or population: people undergoing laparoscopic general abdominal or gynaecological pelvic surgery under general anaesthesia

Setting: secondary and tertiary care

Intervention: helium pneumoperitoneum

Comparison: carbon dioxide pneumoperitoneum

Outcomes

Anticipated absolute effects* (95% CI)

Relative effect
(95% CI)

No of participants
(studies)

Quality of the evidence
(GRADE)

Comments

Risk with carbon dioxide pneumoperitoneum

Risk with helium pneumoperitoneum

Cardiopulmonary complications

Follow‐up: 0 to 1 month

30 per 1000

44 per 1000
(10 to 183)

RR 1.46
(0.35 to 6.12)

128
(3 studies)

⊕⊝⊝⊝
Very low1,2

Trial sequential analysis showed a diversity‐adjusted required information size of 3651 participants to support or refute helium pneumoperitoneum.

Procedure‐related general complications

Follow‐up: 0 to 1 month

See comment

See comment

Not estimable

144
(4 studies)

⊕⊝⊝⊝

Very low3,4

None of the studies reported any significant procedure‐related general complications in either group.

Pneumoperitoneum‐related serious adverse events

Follow‐up: 0 to 1 month

0 per 1000

44 per 1000
(0 to 0)

Peto OR 8.28
(0.86 to 80.03)

128
(3 studies)

⊕⊝⊝⊝
Very low1,3,5

Trial sequential analysis showed a diversity‐adjusted required information size of 4793 participants to support or refute helium pneumoperitoneum.

Mortality

Follow‐up: 0 to 1 month

See comment

See comment

Not estimable

144
(4 studies)

⊕⊕⊝⊝
Low1,3

None of the studies reported any deaths.

Quality of life

None of the studies reported quality of life.

Pain scores (first postoperative day)

Visual analogue scale, lower score indicates less pain.
Scale: 0 to 10

Follow‐up: 1 day

The mean pain scores (first postoperative day) in the carbon dioxide pneumoperitoneum was 3.01 cm

The mean pain scores (first postoperative day) in the helium pneumoperitoneum was
0.49 cm higher
(0.28 lower to 1.26 higher)

MD 0.49 (‐0.28 to 1.26)

108
(2 studies)

⊕⊝⊝⊝
Very low1,3,5

Analgesia requirements (morphine mg)

Follow‐up: 2 days

The mean analgesia requirements (morphine) in the carbon dioxide pneumoperitoneum was 36.6 mg

The mean analgesia requirements (morphine) in the helium pneumoperitoneum was 12 mg higher
(4.44 higher to 19.56 higher)

MD 12.00 (4.44 to 19.56)

90
(1 study)

⊕⊝⊝⊝
Very low1,3,5

Hospital costs

None of the studies reported costs.

*The basis for the assumed risk is the mean comparison group proportion in the studies. The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

CI: confidence interval; MD: mean difference; OR: odds ratio; RR: risk ratio.

GRADE Working Group grades of evidence
High quality: We are very confident that the true effect lies close to that of the estimate of the effect.
Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect.
Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect.

1 Downgraded one level for serious risk of bias.

2 Downgraded two levels for very serious imprecision (the confidence interval of risk ratio overlapped 0.75 and 1.25, and small sample size).

3 Downgraded one level for serious imprecision (small sample size).

4 Downgraded two levels for very serious risk of bias.

5 Downgraded one level for indirectness.

Figuras y tablas -
Summary of findings 2. Helium versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery
Summary of findings 3. Room air versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery

Room air versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery

Patient or population: people undergoing laparoscopic general abdominal or gynaecological pelvic surgery under general anaesthesia

Setting: secondary and tertiary care

Intervention: room air pneumoperitoneum

Comparison: carbon dioxide pneumoperitoneum

Outcomes

Anticipated absolute effects* (95% CI)

Relative effect
(95% CI)

No of participants
(studies)

Quality of the evidence
(GRADE)

Comments

Risk with carbon dioxide pneumoperitoneum

Risk with room air pneumoperitoneum

Cardiopulmonary complications

Follow‐up: 1 month

See comment

See comment

Not estimable

146
(1 study)

⊕⊝⊝⊝
Very low1,2

Trial did not report any cardiopulmonary complications.

Procedure‐related general complications

The study did not report procedure‐related general complications.

Pneumoperitoneum‐related serious adverse events

Follow‐up: 1 month

See comment

See comment

Not estimable

146
(1 study)

⊕⊝⊝⊝
Very low1,2

Trial did not report any pneumoperitoneum‐related serious adverse events.

Mortality

Follow‐up: 1 month

See comment

See comment

Not estimable

146
(1 study)

⊕⊕⊝⊝
Low2,3

The study did not report any deaths.

Quality of life

The study did not report quality of life.

Pain scores (first postoperative day)

Visual analogue scale, lower score indicates less pain.
Scale: 0 to 10 cm

Follow‐up: 1 day

The mean pain scores (first postoperative day) in the carbon dioxide pneumoperitoneum was 2.60 cm

The mean pain scores (first postoperative day) in the room air pneumoperitoneum was
0.80 cm lower
(1.15 lower to 0.45 lower)

MD ‐0.80 (‐1.15 to ‐0.45)

146
(1 study)

⊕⊝⊝⊝
Very low1,2

Analgesia requirements

The study did not report analgesia requirements.

Hospital costs (CNY)

Follow‐up: 1 month

The mean hospital costs in the carbon dioxide pneumoperitoneum was CNY12,012.00

The mean hospital costs in the room air pneumoperitoneum was CNY2667.00 lower
(3275.68 lower to 2058.32 lower)

MD ‐2667.00 (‐3275.68 to ‐2058.32)

146
(1 study)

⊕⊝⊝⊝
Very low1,2

*The basis for the assumed risk is the mean comparison group proportion in the studies. The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

CI: confidence interval; MD: mean difference.

GRADE Working Group grades of evidence
High quality: We are very confident that the true effect lies close to that of the estimate of the effect.
Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect.
Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect.

1 Downgraded two levels for very serious risk of bias.

2 Downgraded one level for serious imprecision (small sample size).

3 Downgraded one level for serious risk of bias.

Figuras y tablas -
Summary of findings 3. Room air versus carbon dioxide for establishing pneumoperitoneum during laparoscopic abdominal surgery
Table 1. Sensitivity analysis by changing between worst‐case scenario analysis and best‐case scenario analysis for missing data

Changing between worst‐case scenario analysis and best‐case scenario analysis for missing data

Outcomes

Risk ratio (95% CI)

Main analysis

Worst/best‐case

Best/worst‐case

Cardiopulmonary complications (nitrous oxide vs carbon dioxide)

2.00 (0.38, 10.43)

2.64 (0.64, 10.93)

1.02 (0.27, 3.86)

Procedure‐related general complications/surgical morbidity (nitrous oxide vs carbon dioxide)

1.01 (0.18, 5.71)

1.82 (0.40, 8.31)

0.56 (0.12, 2.58)

Pneumoperitoneum‐related serious adverse events (nitrous oxide vs carbon dioxide)

No events

Peto OR

7.46 (0.47, 119.30)

Peto OR

0.14 (0.01, 2.19)

Mortality (nitrous oxide vs carbon dioxide)

No events

Peto OR

7.46 (0.47, 119.30)

Peto OR

0.14 (0.01, 2.19)

Cardiopulmonary complications (helium vs carbon dioxide)

1.46 (0.35, 6.12)

4.58 (1.21, 17.36)

1.46 (0.35, 6.12)

Procedure‐related general complications/surgical morbidity (helium vs carbon dioxide)

No events

8.47 (1.11, 64.60)

0.20 (0.01, 3.61)

Pneumoperitoneum‐related serious adverse events (helium vs carbon dioxide)

Peto OR

8.28 (0.86, 80.03)

Peto OR

9.19 (2.56, 33.01)

Peto OR

8.28 (0.86, 80.03)

Mortality (helium vs carbon dioxide)

No events

Peto OR

8.89 (1.94, 40.64)

Peto OR

0.12 (0.01, 2.07)

Peto OR: Peto odds ratio, which was calculated for rare events (mortality, serious adverse events).

Figuras y tablas -
Table 1. Sensitivity analysis by changing between worst‐case scenario analysis and best‐case scenario analysis for missing data
Comparison 1. Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Cardiopulmonary complications Show forest plot

2

140

Risk Ratio (M‐H, Fixed, 95% CI)

2.0 [0.38, 10.43]

2 Procedure‐related general complications Show forest plot

2

143

Risk Ratio (M‐H, Fixed, 95% CI)

1.01 [0.18, 5.71]

3 Analgesia requirements Show forest plot

3

193

Std. Mean Difference (IV, Random, 95% CI)

‐0.69 [‐1.42, 0.04]

3.1 Oxycodone (mg)

2

140

Std. Mean Difference (IV, Random, 95% CI)

‐0.97 [‐1.71, ‐0.22]

3.2 Ibuprofen (tablets/24 hours)

1

53

Std. Mean Difference (IV, Random, 95% CI)

‐0.16 [‐0.70, 0.38]

4 Cardiopulmonary changes Show forest plot

1

Mean Difference (IV, Fixed, 95% CI)

Subtotals only

4.1 Heart rate (beats/minute)

1

100

Mean Difference (IV, Fixed, 95% CI)

‐0.60 [‐4.13, 2.93]

4.2 Mean arterial pressure (mmHg)

1

100

Mean Difference (IV, Fixed, 95% CI)

‐3.80 [‐7.90, 0.30]

4.3 Oxygen saturation (%)

1

100

Mean Difference (IV, Fixed, 95% CI)

0.0 [‐0.39, 0.39]

4.4 Peak airway pressure (cm H2O)

1

100

Mean Difference (IV, Fixed, 95% CI)

‐0.30 [‐2.17, 1.57]

Figuras y tablas -
Comparison 1. Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum
Comparison 2. Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Cardiopulmonary complications Show forest plot

3

128

Risk Ratio (M‐H, Fixed, 95% CI)

1.46 [0.35, 6.12]

2 Pneumoperitoneum‐related serious adverse events Show forest plot

3

128

Peto Odds Ratio (Peto, Fixed, 95% CI)

8.28 [0.86, 80.03]

3 Pain scores (cm) (first postoperative day) Show forest plot

2

108

Mean Difference (IV, Fixed, 95% CI)

0.49 [‐0.28, 1.26]

4 Analgesia requirements (morphine mg) Show forest plot

1

90

Mean Difference (IV, Fixed, 95% CI)

12.0 [4.44, 19.56]

5 Number of participants requiring analgesia Show forest plot

1

18

Risk Ratio (M‐H, Fixed, 95% CI)

0.42 [0.17, 1.04]

6 Cardiopulmonary parameters Show forest plot

3

Mean Difference (IV, Fixed, 95% CI)

Subtotals only

6.1 Blood pH (start)

2

34

Mean Difference (IV, Fixed, 95% CI)

0.01 [‐0.01, 0.04]

6.2 Blood pH (middle)

3

52

Mean Difference (IV, Fixed, 95% CI)

‐0.00 [‐0.03, 0.02]

6.3 Blood pH (end)

2

34

Mean Difference (IV, Fixed, 95% CI)

0.10 [0.06, 0.14]

6.4 Partial pressure of carbon dioxide (mmHg) (start)

2

34

Mean Difference (IV, Fixed, 95% CI)

0.31 [‐1.79, 2.40]

6.5 Partial pressure of carbon dioxide (mmHg) (middle)

3

52

Mean Difference (IV, Fixed, 95% CI)

‐0.84 [‐3.70, 2.02]

6.6 Partial pressure of carbon dioxide (mmHg) (end)

2

34

Mean Difference (IV, Fixed, 95% CI)

‐12.78 [‐16.78, ‐8.77]

Figuras y tablas -
Comparison 2. Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum
Comparison 3. Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Cardiopulmonary complications Show forest plot

1

146

Risk Ratio (M‐H, Fixed, 95% CI)

0.0 [0.0, 0.0]

2 Pneumoperitoneum‐related serious adverse events Show forest plot

1

146

Peto Odds Ratio (Peto, Fixed, 95% CI)

0.0 [0.0, 0.0]

3 Pain scores (cm) (first postoperative day) Show forest plot

1

146

Mean Difference (IV, Fixed, 95% CI)

‐0.8 [‐1.15, ‐0.45]

4 Hospital costs (CNY) Show forest plot

1

146

Mean Difference (IV, Fixed, 95% CI)

‐2667.0 [‐3275.68, ‐2058.32]

5 Cardiopulmonary parameters Show forest plot

1

Mean Difference (IV, Fixed, 95% CI)

Subtotals only

5.1 Heart rate (beats/minute) (start)

1

146

Mean Difference (IV, Fixed, 95% CI)

‐0.10 [‐3.11, 2.91]

5.2 Heart rate (beats/minute) (middle)

1

146

Mean Difference (IV, Fixed, 95% CI)

‐7.30 [‐9.78, ‐4.82]

5.3 Heart rate (beats/minute) (end)

1

146

Mean Difference (IV, Fixed, 95% CI)

‐8.70 [‐11.72, ‐5.68]

5.4 Blood systolic pressure (mmHg) (start)

1

146

Mean Difference (IV, Fixed, 95% CI)

‐1.0 [‐5.12, 3.12]

5.5 Blood systolic pressure (mmHg) (middle)

1

146

Mean Difference (IV, Fixed, 95% CI)

2.80 [‐0.44, 6.04]

5.6 Blood systolic pressure (mmHg) (end)

1

146

Mean Difference (IV, Fixed, 95% CI)

‐2.0 [‐5.42, 1.42]

5.7 Partial pressure of carbon dioxide (mmHg) (start)

1

146

Mean Difference (IV, Fixed, 95% CI)

‐0.20 [‐1.39, 0.99]

5.8 Partial pressure of carbon dioxide (mmHg) (middle)

1

146

Mean Difference (IV, Fixed, 95% CI)

‐0.30 [‐1.37, 0.77]

5.9 Partial pressure of carbon dioxide (mmHg) (end)

1

146

Mean Difference (IV, Fixed, 95% CI)

0.10 [‐1.43, 1.63]

Figuras y tablas -
Comparison 3. Room air pneumoperitoneum versus carbon dioxide pneumoperitoneum
Comparison 4. Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data)

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Cardiopulmonary complications Show forest plot

2

143

Risk Ratio (M‐H, Fixed, 95% CI)

2.64 [0.64, 10.93]

2 Procedure‐related general complications Show forest plot

2

143

Risk Ratio (M‐H, Fixed, 95% CI)

1.82 [0.40, 8.31]

3 Pneumoperitoneum‐related serious adverse events Show forest plot

2

143

Peto Odds Ratio (Peto, Fixed, 95% CI)

7.46 [0.47, 119.30]

4 Mortality Show forest plot

2

143

Peto Odds Ratio (Peto, Fixed, 95% CI)

7.46 [0.47, 119.30]

Figuras y tablas -
Comparison 4. Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data)
Comparison 5. Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Cardiopulmonary complications Show forest plot

2

143

Risk Ratio (M‐H, Fixed, 95% CI)

1.02 [0.27, 3.86]

2 Procedure‐related general complications Show forest plot

2

143

Risk Ratio (M‐H, Fixed, 95% CI)

0.56 [0.12, 2.58]

3 Pneumoperitoneum‐related serious adverse events Show forest plot

2

143

Peto Odds Ratio (Peto, Fixed, 95% CI)

0.14 [0.01, 2.19]

4 Mortality Show forest plot

2

143

Peto Odds Ratio (Peto, Fixed, 95% CI)

0.14 [0.01, 2.19]

Figuras y tablas -
Comparison 5. Nitrous oxide pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data
Comparison 6. Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data)

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Cardiopulmonary complications Show forest plot

3

128

Risk Ratio (M‐H, Fixed, 95% CI)

4.58 [1.21, 17.36]

2 Procedure‐related general complications Show forest plot

4

144

Risk Ratio (M‐H, Fixed, 95% CI)

8.47 [1.11, 64.60]

3 Pneumoperitoneum‐related serious adverse events Show forest plot

3

128

Peto Odds Ratio (Peto, Fixed, 95% CI)

9.19 [2.56, 33.01]

4 Mortality Show forest plot

4

144

Peto Odds Ratio (Peto, Fixed, 95% CI)

8.89 [1.94, 40.64]

Figuras y tablas -
Comparison 6. Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (worst/best‐case scenario analysis for missing data)
Comparison 7. Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Cardiopulmonary complications Show forest plot

3

128

Risk Ratio (M‐H, Fixed, 95% CI)

1.46 [0.35, 6.12]

2 Procedure‐related general complications Show forest plot

4

144

Risk Ratio (M‐H, Fixed, 95% CI)

0.2 [0.01, 3.61]

3 Pneumoperitoneum‐related serious adverse events Show forest plot

3

128

Peto Odds Ratio (Peto, Fixed, 95% CI)

8.28 [0.86, 80.03]

4 Mortality Show forest plot

4

144

Peto Odds Ratio (Peto, Fixed, 95% CI)

0.12 [0.01, 2.07]

Figuras y tablas -
Comparison 7. Helium pneumoperitoneum versus carbon dioxide pneumoperitoneum (best/worst‐case scenario analysis for missing data