Anesthesia For Anesthesia For Nonobstetric Surgery Nonobstetric Surgery

During PregnancyDuring PregnancyMay 6, 2005 R1May 6, 2005 R1 林群博林群博

General ConsiderationsGeneral Considerations

Surgery during pregnancy:Surgery during pregnancy:

1.5%-2% of all pregnancies in USA1.5%-2% of all pregnancies in USA The operations include:The operations include:

Directly related to pregnancyDirectly related to pregnancy

Indirectly related to pregnancyIndirectly related to pregnancy

Unrelated to gestationUnrelated to gestation

Concern For AnesthesiaConcern For Anesthesia

Two major categories:Two major categories:

Teratogenicity of the anesthetic Teratogenicity of the anesthetic agentsagents

Maternal and fetal physiologic Maternal and fetal physiologic changeschanges

Teratogenicity(1)Teratogenicity(1)

Teratogenicity(2)Teratogenicity(2)

Virtually every drug and every Virtually every drug and every inhalation anesthetic is teratogenic inhalation anesthetic is teratogenic to some species under certain to some species under certain conditionsconditions

None has been identified as a None has been identified as a definite human teratogendefinite human teratogen

Teratogenicity(3)Teratogenicity(3)

Nitrous OxideNitrous Oxide

Ability to oxide cobalamin (Vitamin Ability to oxide cobalamin (Vitamin B12), inhibit methionine synthase B12), inhibit methionine synthase activityactivity

DNA production, myelin deposition, DNA production, myelin deposition, and other folate and methylation and other folate and methylation process-dependent reactions might process-dependent reactions might be affectedbe affected

Anesthetic Anesthetic Consideration(1)Consideration(1)

Prudent to postpone elective surgical Prudent to postpone elective surgical procedures until after deliveryprocedures until after delivery

The first trimester should be avoided for The first trimester should be avoided for smiselective casessmiselective cases

Regional anesthesia should be entertainedRegional anesthesia should be entertained Spinal anesthesia offers the least drug Spinal anesthesia offers the least drug

transfer for the degree of aesthesia achievedtransfer for the degree of aesthesia achieved Hypotension, aortocaval compression, Hypotension, aortocaval compression,

maternal hypoxia, and acidosis: avoided and maternal hypoxia, and acidosis: avoided and treated promptlytreated promptly

Other forms of regional anesthesia yield Other forms of regional anesthesia yield higher local anesthetic blood levels and more higher local anesthetic blood levels and more placental transferplacental transfer

Anesthetic Anesthetic Consideration(2)Consideration(2)

Greater risks for aspiration:Greater risks for aspiration:

Decrease in lower esophageal Decrease in lower esophageal sphincter tonesphincter tone

Mechanical effects of the gravid Mechanical effects of the gravid uterus uterus

Impaired gastric emptyingImpaired gastric emptying

Intraoperative Intraoperative MonitoringMonitoring

Overall goal: maintain the mother Overall goal: maintain the mother and fetus in the best possible and fetus in the best possible physiological conditionphysiological condition

Protect the patient from the usual Protect the patient from the usual stresses encountered in the stresses encountered in the operating room such as anxiety, operating room such as anxiety, pain, positioning , temperature pain, positioning , temperature changes, fluid and blood losseschanges, fluid and blood losses

Essential monitoringEssential monitoring: : BP, PR, EKG, respirations, temperature, pulse BP, PR, EKG, respirations, temperature, pulse

oximetryoximetry Left uterine displacementLeft uterine displacement:: avoid aortocaval compressionavoid aortocaval compression Avoid hyperventilationAvoid hyperventilation: : Respiratory alkalosis causes:Respiratory alkalosis causes: oxyhemoglobin dissociation curve shifted to oxyhemoglobin dissociation curve shifted to

the leftthe left impair transfer of oxygen across the placentaimpair transfer of oxygen across the placenta decreases umbilical blood flowdecreases umbilical blood flow

Fetal Heart Rate Fetal Heart Rate MonitoringMonitoring

Identify intraoperative conditions Identify intraoperative conditions leading to impaired uteroplacental leading to impaired uteroplacental blood flow and fetal oxygenationblood flow and fetal oxygenation

Variability decreased by hypoxia and Variability decreased by hypoxia and by sedative drugsby sedative drugs

Slowing of FHR: hypoxemia, fall in Slowing of FHR: hypoxemia, fall in temperature or administration of temperature or administration of drugs or anesthetic agentsdrugs or anesthetic agents

Fetal tachycardia: maternal fever, Fetal tachycardia: maternal fever, maternal/fetal sepsis, drugmaternal/fetal sepsis, drug

Prevention of Preterm Prevention of Preterm LaborLabor

Increased incidence of abortion and Increased incidence of abortion and preterm deliverypreterm delivery

Timing of the surgeryTiming of the surgery Women undergoing third-trimester Women undergoing third-trimester

procedures are at greatest riskprocedures are at greatest risk Prophylactic use of tocolyticsProphylactic use of tocolytics Pain should be controlled : association Pain should be controlled : association

between postoperative pain and between postoperative pain and anxiety and uterine irritability anxiety and uterine irritability

The most common abdominal The most common abdominal procedures: procedures:

AppendectomyAppendectomy

CholecystectomyCholecystectomy

Adnexal surgeryAdnexal surgery Laparoscopic surgeryLaparoscopic surgery NeurosurgeryNeurosurgery Cardiac surgery requiring bypassCardiac surgery requiring bypass

AppendectomyAppendectomy

Appendicitis: the most common Appendicitis: the most common nonobstetric surgical emergency nonobstetric surgical emergency during pregnancyduring pregnancy

Appears to occur more frequently in Appears to occur more frequently in the second and third trimestersthe second and third trimesters

The mortality of appendicitis The mortality of appendicitis complicating pregnancy is the complicating pregnancy is the mortality of delaymortality of delay

Cardiac Surgery During Cardiac Surgery During PregnancyPregnancy

Blood volume and cardiac output: Blood volume and cardiac output: 30%-50% increase30%-50% increase

Patients with preexisting cardiac Patients with preexisting cardiac disease: exposed to a major stress disease: exposed to a major stress when entering the second and third when entering the second and third trimesters of gestationtrimesters of gestation

Cardiopulmonary BypassCardiopulmonary Bypass

Increases the risks for fetus and Increases the risks for fetus and adversely affects fetal oxygenation:adversely affects fetal oxygenation:

Nonpulsatile perfusionNonpulsatile perfusion

Inadequate perfusion pressureInadequate perfusion pressure

Inadequate pump flowInadequate pump flow

Embolic phenomena to the Embolic phenomena to the uteroplacental beduteroplacental bed

Release of renin and catecholaminesRelease of renin and catecholamines

Moderate hypothermia during bypass:Moderate hypothermia during bypass: Persistent fetal bradycardiaPersistent fetal bradycardia Warm cardiopulmonary bypass will Warm cardiopulmonary bypass will

improveimprove Increasing pump flow if FHR<80 bpmIncreasing pump flow if FHR<80 bpm Ensure adequate uteroplacental perfusion Ensure adequate uteroplacental perfusion Pump flow 30-50% greater than usualPump flow 30-50% greater than usual Perfusion pressure at or above 60 mmHgPerfusion pressure at or above 60 mmHg Arterial blood gases for acid-base status, Arterial blood gases for acid-base status,

oxygenation, and ventilationoxygenation, and ventilation

Neurosurgery During Neurosurgery During PregnancyPregnancy

Subarachnoid hemorrhage from Subarachnoid hemorrhage from intracranial saccular aneurysm or intracranial saccular aneurysm or arteriovenous malformation: not arteriovenous malformation: not uncommon during pregnancyuncommon during pregnancy

The factors predispose to rupture:The factors predispose to rupture:

Increased cardiac output and blood Increased cardiac output and blood volumevolume

The softening of vascular connective The softening of vascular connective tissue by tissue by

the hormone changes of pregnancythe hormone changes of pregnancy

The Usual Neurosurgical The Usual Neurosurgical ApproachApproach

Controlled hypotensionControlled hypotension HypothermiaHypothermia HyperventilationHyperventilation DiuresisDiuresis

Controlled HypotensionControlled Hypotension Volatile anesthetic, nitroglycerin, Volatile anesthetic, nitroglycerin,

nitroprussidenitroprusside Reduction in SBP of 25-30% or MBP< Reduction in SBP of 25-30% or MBP<

70mmHg: reduction in uteroplacental blood 70mmHg: reduction in uteroplacental blood flowflow

Cross placenta: fetal hypotensionCross placenta: fetal hypotension Nitroprusside: converted to cyanide, which Nitroprusside: converted to cyanide, which

causes significant toxicity and fetal deathcauses significant toxicity and fetal death Discontinued when: Discontinued when: Infusion rate> 0.5 mg/kg/hourInfusion rate> 0.5 mg/kg/hour Maternal metabolic acidosisMaternal metabolic acidosis Resistance to the agentResistance to the agent

Hypothermia: fetal bradycardiaHypothermia: fetal bradycardia Hyperventilation: Hyperventilation:

Decreased placental oxygen Decreased placental oxygen transfertransfer

Umbilical vessel vasoconstrictionUmbilical vessel vasoconstriction Diuesis: significant negative fluid Diuesis: significant negative fluid

shift for the fetusshift for the fetus

Laparoscopic Surgery During Laparoscopic Surgery During PregnancyPregnancy

Adding pneumoperitoneum to an Adding pneumoperitoneum to an enlarged uterus: enlarged uterus:

Limit diaphragm expansionLimit diaphragm expansion

Increase in peak airway pressureIncrease in peak airway pressure

Decrease in FRCDecrease in FRC

Decrease thoracic cavity complianceDecrease thoracic cavity compliance

Increased ventilation-perfusion Increased ventilation-perfusion mismatchingmismatching

COCO22 pneumoperitoneum: pneumoperitoneum: hypercapnia and hypoxemiahypercapnia and hypoxemia

Hyperventilation: reduce Hyperventilation: reduce uteroplacental blood flowuteroplacental blood flow

Reduce venous return and cardiac Reduce venous return and cardiac index: significant hypotensionindex: significant hypotension

ConclusionsConclusions Understanding the physiological changes of Understanding the physiological changes of

pregnancy and their influence on the patientpregnancy and their influence on the patient Maintaining an adequate uteroplacental Maintaining an adequate uteroplacental

perfusionperfusion Selecting anesthetic drugs and techniquesSelecting anesthetic drugs and techniques Using regional anesthesia whenever possibleUsing regional anesthesia whenever possible Inform the patient no anesthetic agent or Inform the patient no anesthetic agent or

adjuvant drug has as yet been proven to be adjuvant drug has as yet been proven to be teratogenic in humansteratogenic in humans

Providing fetal surveillance with external fetal Providing fetal surveillance with external fetal heart rate monitoring and uterine activityheart rate monitoring and uterine activity

Making appropriate adjustments in techniques Making appropriate adjustments in techniques as guided by the resultsas guided by the results

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