Suspension of Mechanical Ventilation in Ureteroscopic Lithotripsy Under General Anesthesia

Study Overview
=================
Brief Summary
-----------------
For some upper ureteral and renal stones,ureteroscopic lithotripsy needs to be performed under general anesthesia with interrupted suspension of mechanical ventilation, which could result in hypercapnia and hypoxia. In this study, the investigators hypothesize that 10 cmH2O PEEP added to the respiratory circuit with 1 L/min 100% oxygen might extend the time of ventilation suspension but have no effect on carbon dioxide retention in blood.

Detailed Description
-----------------
For some upper ureteral and renal stones,ureteroscopic lithotripsy is often perdurbed by the patient's respiratory movement either under epidural anesthesia or general anesthesia with mechanical ventilation. So intermittent suspension of mechanical ventilation under general anesthesia can ensure the surgery to be performed continuously and successfully. But this could result in hypercapnia and hypoxia. So far, there have been few studies focused on the change of the internal environment in blood as result of suspending breath. In this study, the investigators hypothesize that 10 cmH2O PEEP added to the respiratory circuit with 1 L/min 100% oxygen might extend the time of ventilation suspension but have no effect on carbon dioxide retention in blood.

Conditions
-----------------
Hypercapnia, Hypoxia

Intervention / Treatment
-----------------
* Other: PEEP


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: ASA I III general anesthesia sign the informed consent Exclusion Criteria: ASA IV or V woman who is pregnant or plans to bear

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Supportive Care
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: with PEEP<br>10 cmH2O PEEP added to the respiratory curcuit during suspension of mechanical ventilation | Other: PEEP<br>* PEEP means that when mechanical ventilation is suspended, the value of expiratory valve in the anesthesia machine is set at 10 cmH2O with 1 L/min 100% oxygen.<br>* Other names: positive end-expiratory pressure;|
| Placebo Comparator: without PEEP<br>0 cmH2O PEEP added to the respiratory curcuit during suspension of mechanical ventilation | |

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change in blood gas | we chose different time points to mesure the changes in blood gas. | Baseline before suspension of ventilation, 5 min after suspension, 10 min after suspension, 15 min after suspension, 5 min after re-ventilaiton, 10 min after re-ventilation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in systolic blood pressure | we chose different time points to mesure the changes in systolic blood pressure | Baseline before suspension of ventilation, 5 min after suspension, 10 min after suspension, 15 min after suspension, 5 min after re-ventilaiton, 10 min after re-ventilation |