Korean J Anesthesiol.  1999 May;36(5):823-827. 10.4097/kjae.1999.36.5.823.

The Factor that Determines Mechanical Ventilation during Cesarean Section under General Anesthesia: Weight before pregnancy vs. weight during delivery

• Oh MK
• Seung IS

• KMID: 2240072
• DOI: http://doi.org/10.4097/kjae.1999.36.5.823

Abstract

BACKGROUND: During general anesthesia the adult patient's tidal volume is determined by patient's weight. Therefore patients with severe ascites, huge abdominal mass or pregnancy have considerable ventilatory change during the operation because the great change in their body weight, that might cause unwanted respiratory alkalosis or acidosis. The purpose of this study is to identify the effects of such changes in ventilation between pre-delivery and post-delivery periods during the cesarean section.
METHODS
Eighteen 36weeks or older pregnant patients (ASA 1), scheduled for elective cesarean section under general anesthesia, are selected for the study. PhysioFlex was used for ventilation. Pre-induction maternal gas analysis were performed in all cases. They were randomly divided into two groups according to the ventilator setting for minute ventilation, one set by pre-pregnant weight (Group 1) and the other by pregnant (term) weight (Group 2). Blood gas analysis were performed 5 minutes after induction and 20 minutes after delivery. End-tidal CO2 and inspiratory airway pressure were also measured.
RESULTS
All patients show mild hyperventilation with normal acid-base status at pre-induction period. There were no significant differences in arterial PCO2 value between two groups. Group 1 shows mild metabolic acidosis compared with group 2 (by pH at 20 minutes after delivery).
CONCLUSION
Term(just prior to operation) body weight rather than pre-pregnant weight is preferable for ventilator setting in the case of cesarean section under general anesthesia.

Keyword

Anesthesia, general; Lung, minute ventilation; Monitoring, arterial blood gas analysis; Surgery, cesarean section

MeSH Terms

Acidosis
Adult
Alkalosis, Respiratory
Anesthesia, General*
Ascites
Blood Gas Analysis
Body Weight
Cesarean Section*
Female
Humans
Hydrogen-Ion Concentration
Hyperventilation
Pregnancy
Pregnancy*
Respiration, Artificial*
Tidal Volume
Ventilation
Ventilators, Mechanical