Anesthesia For Nonobstetric Surgery During Pregnancy May 6, 2005 R1 林群博

General Considerations Surgery during pregnancy: Surgery during pregnancy: 1.5%-2% of all pregnancies in USA 1.5%-2% of all pregnancies in USA The operations include: The operations include: Directly related to pregnancy Directly related to pregnancy Indirectly related to pregnancy Indirectly related to pregnancy Unrelated to gestation Unrelated to gestation

Concern For Anesthesia Two major categories: Two major categories: Teratogenicity of the anesthetic agents Teratogenicity of the anesthetic agents Maternal and fetal physiologic changes Maternal and fetal physiologic changes

Teratogenicity(1)

Teratogenicity(2) Virtually every drug and every inhalation anesthetic is teratogenic to some species under certain conditions Virtually every drug and every inhalation anesthetic is teratogenic to some species under certain conditions None has been identified as a definite human teratogen None has been identified as a definite human teratogen

Teratogenicity(3)

Nitrous Oxide Ability to oxide cobalamin (Vitamin B12), inhibit methionine synthase activity Ability to oxide cobalamin (Vitamin B12), inhibit methionine synthase activity DNA production, myelin deposition, and other folate and methylation process-dependent reactions might be affected DNA production, myelin deposition, and other folate and methylation process-dependent reactions might be affected

Anesthetic Consideration(1) Prudent to postpone elective surgical procedures until after delivery Prudent to postpone elective surgical procedures until after delivery The first trimester should be avoided for smiselective cases The first trimester should be avoided for smiselective cases Regional anesthesia should be entertained Regional anesthesia should be entertained Spinal anesthesia offers the least drug transfer for the degree of aesthesia achieved Spinal anesthesia offers the least drug transfer for the degree of aesthesia achieved Hypotension, aortocaval compression, maternal hypoxia, and acidosis: avoided and treated promptly Hypotension, aortocaval compression, maternal hypoxia, and acidosis: avoided and treated promptly Other forms of regional anesthesia yield higher local anesthetic blood levels and more placental transfer Other forms of regional anesthesia yield higher local anesthetic blood levels and more placental transfer

Anesthetic Consideration(2) Greater risks for aspiration: Greater risks for aspiration: Decrease in lower esophageal sphincter tone Decrease in lower esophageal sphincter tone Mechanical effects of the gravid uterus Mechanical effects of the gravid uterus Impaired gastric emptying Impaired gastric emptying

Intraoperative Monitoring Overall goal: maintain the mother and fetus in the best possible physiological condition Overall goal: maintain the mother and fetus in the best possible physiological condition Protect the patient from the usual stresses encountered in the operating room such as anxiety, pain, positioning, temperature changes, fluid and blood losses Protect the patient from the usual stresses encountered in the operating room such as anxiety, pain, positioning, temperature changes, fluid and blood losses

Essential monitoring: Essential monitoring: BP, PR, EKG, respirations, temperature, pulse oximetry BP, PR, EKG, respirations, temperature, pulse oximetry Left uterine displacement: Left uterine displacement: avoid aortocaval compression avoid aortocaval compression Avoid hyperventilation: Avoid hyperventilation: Respiratory alkalosis causes: Respiratory alkalosis causes: oxyhemoglobin dissociation curve shifted to the left oxyhemoglobin dissociation curve shifted to the left impair transfer of oxygen across the placenta impair transfer of oxygen across the placenta decreases umbilical blood flow decreases umbilical blood flow

Fetal Heart Rate Monitoring Identify intraoperative conditions leading to impaired uteroplacental blood flow and fetal oxygenation Identify intraoperative conditions leading to impaired uteroplacental blood flow and fetal oxygenation Variability decreased by hypoxia and by sedative drugs Variability decreased by hypoxia and by sedative drugs Slowing of FHR: hypoxemia, fall in temperature or administration of drugs or anesthetic agents Slowing of FHR: hypoxemia, fall in temperature or administration of drugs or anesthetic agents Fetal tachycardia: maternal fever, maternal/fetal sepsis, drug Fetal tachycardia: maternal fever, maternal/fetal sepsis, drug

Prevention of Preterm Labor Increased incidence of abortion and preterm delivery Increased incidence of abortion and preterm delivery Timing of the surgery Timing of the surgery Women undergoing third-trimester procedures are at greatest risk Women undergoing third-trimester procedures are at greatest risk Prophylactic use of tocolytics Prophylactic use of tocolytics Pain should be controlled : association between postoperative pain and anxiety and uterine irritability Pain should be controlled : association between postoperative pain and anxiety and uterine irritability

The most common abdominal procedures: The most common abdominal procedures: Appendectomy Appendectomy Cholecystectomy Cholecystectomy Adnexal surgery Adnexal surgery Laparoscopic surgery Laparoscopic surgery Neurosurgery Neurosurgery Cardiac surgery requiring bypass Cardiac surgery requiring bypass

Appendectomy Appendicitis: the most common nonobstetric surgical emergency during pregnancy Appendicitis: the most common nonobstetric surgical emergency during pregnancy Appears to occur more frequently in the second and third trimesters Appears to occur more frequently in the second and third trimesters The mortality of appendicitis complicating pregnancy is the mortality of delay The mortality of appendicitis complicating pregnancy is the mortality of delay

Cardiac Surgery During Pregnancy Blood volume and cardiac output: 30%-50% increase Blood volume and cardiac output: 30%-50% increase Patients with preexisting cardiac disease: exposed to a major stress when entering the second and third trimesters of gestation Patients with preexisting cardiac disease: exposed to a major stress when entering the second and third trimesters of gestation

Cardiopulmonary Bypass Increases the risks for fetus and adversely affects fetal oxygenation: Increases the risks for fetus and adversely affects fetal oxygenation: Nonpulsatile perfusion Nonpulsatile perfusion Inadequate perfusion pressure Inadequate perfusion pressure Inadequate pump flow Inadequate pump flow Embolic phenomena to the uteroplacental bed Embolic phenomena to the uteroplacental bed Release of renin and catecholamines Release of renin and catecholamines

Moderate hypothermia during bypass: Moderate hypothermia during bypass: Persistent fetal bradycardia Persistent fetal bradycardia Warm cardiopulmonary bypass will improve Warm cardiopulmonary bypass will improve Increasing pump flow if FHR<80 bpm Increasing pump flow if FHR<80 bpm Ensure adequate uteroplacental perfusion Ensure adequate uteroplacental perfusion Pump flow 30-50% greater than usual Pump flow 30-50% greater than usual Perfusion pressure at or above 60 mmHg Perfusion pressure at or above 60 mmHg Arterial blood gases for acid-base status, oxygenation, and ventilation Arterial blood gases for acid-base status, oxygenation, and ventilation

Neurosurgery During Pregnancy Subarachnoid hemorrhage from intracranial saccular aneurysm or arteriovenous malformation: not uncommon during pregnancy Subarachnoid hemorrhage from intracranial saccular aneurysm or arteriovenous malformation: not uncommon during pregnancy The factors predispose to rupture: The factors predispose to rupture: Increased cardiac output and blood volume Increased cardiac output and blood volume The softening of vascular connective tissue by The softening of vascular connective tissue by the hormone changes of pregnancy the hormone changes of pregnancy

The Usual Neurosurgical Approach Controlled hypotension Controlled hypotension Hypothermia Hypothermia Hyperventilation Hyperventilation Diuresis Diuresis

Controlled Hypotension Volatile anesthetic, nitroglycerin, nitroprusside Volatile anesthetic, nitroglycerin, nitroprusside Reduction in SBP of 25-30% or MBP< 70mmHg: reduction in uteroplacental blood flow Reduction in SBP of 25-30% or MBP< 70mmHg: reduction in uteroplacental blood flow Cross placenta: fetal hypotension Cross placenta: fetal hypotension Nitroprusside: converted to cyanide, which causes significant toxicity and fetal death Nitroprusside: converted to cyanide, which causes significant toxicity and fetal death Discontinued when: Discontinued when: Infusion rate> 0.5 mg/kg/hour Infusion rate> 0.5 mg/kg/hour Maternal metabolic acidosis Maternal metabolic acidosis Resistance to the agent Resistance to the agent

Hypothermia: fetal bradycardia Hypothermia: fetal bradycardia Hyperventilation: Hyperventilation: Decreased placental oxygen transfer Decreased placental oxygen transfer Umbilical vessel vasoconstriction Umbilical vessel vasoconstriction Diuesis: significant negative fluid shift for the fetus Diuesis: significant negative fluid shift for the fetus

Laparoscopic Surgery During Pregnancy Adding pneumoperitoneum to an enlarged uterus: Adding pneumoperitoneum to an enlarged uterus: Limit diaphragm expansion Limit diaphragm expansion Increase in peak airway pressure Increase in peak airway pressure Decrease in FRC Decrease in FRC Decrease thoracic cavity compliance Decrease thoracic cavity compliance Increased ventilation-perfusion mismatching Increased ventilation-perfusion mismatching

CO 2 pneumoperitoneum: hypercapnia and hypoxemia CO 2 pneumoperitoneum: hypercapnia and hypoxemia Hyperventilation: reduce uteroplacental blood flow Hyperventilation: reduce uteroplacental blood flow Reduce venous return and cardiac index: significant hypotension Reduce venous return and cardiac index: significant hypotension

Conclusions Understanding the physiological changes of pregnancy and their influence on the patient Understanding the physiological changes of pregnancy and their influence on the patient Maintaining an adequate uteroplacental perfusion Maintaining an adequate uteroplacental perfusion Selecting anesthetic drugs and techniques Selecting anesthetic drugs and techniques Using regional anesthesia whenever possible Using regional anesthesia whenever possible Inform the patient no anesthetic agent or adjuvant drug has as yet been proven to be teratogenic in humans Inform the patient no anesthetic agent or adjuvant drug has as yet been proven to be teratogenic in humans Providing fetal surveillance with external fetal heart rate monitoring and uterine activity Providing fetal surveillance with external fetal heart rate monitoring and uterine activity Making appropriate adjustments in techniques as guided by the results Making appropriate adjustments in techniques as guided by the results

Thanks For Your Attention!!