Anesthesia for special situations in Obstetrics firstname.lastname@example.org
Encerclage • Cervical suture (Shirodkar or McDonald cerclage) • Cervical incompetence • Emergency during pregnancy/electively at 12–16 weeks’ gestation • Day-case basis • Grossly disrupted cervix - abdominal approach
Problems/special considerations • Anxiety • Standard anaesthesia • Risks of anaesthesia in pregnancy • Monitoring of fetus • If membranes bulging • Head-down position • Tocolysis
Management • Spinal anaesthesia - technique of choice • Epidural anesthesia – acceptable • Less extensive block than LSCS (from T8–10 to sacral roots) • Less doses required • Doses of LA- 75% of those used for LSCS
General anaesthesia • Adv – Uterine relaxation • Disadvantage • Effect on fetus • Risk of regurgitation and aspiration • Paracervical and pudendal block • Intravenous analgesia/sedation
External cephalic version (ECV) • To convert a breech or shoulder presentation to a cephalic one • Manipulation of fetus through the mother’s abdominal wall and anterior wall of the uterus • Success rate - 50–80%.
External cephalic version (ECV) • 36–37 weeks’ gestation • Less chances of reversion • Risk of premature delivery • Contraindications • multiple pregnancy • APH/ placenta praevia • ruptured membranes • fetal abnormalities • factors which indicate LSCS, • Relative Contraindications • Previous LSCS /IUGR/PE/obesity
Problems/special considerations • NPO • Continuous fetal monitoring • Mother - tilted supine position • Rotationary pressure to fetus whilst attempting to lift presenting part out of pelvis • Tocolytic drugs • Maternal discomfort/Anxiety- reduced chance of success • Sedation (e.g. benzodiazepines) /epidural analgesia • Obstetricians – Not in favour of adjuncts • Complications • maternal or fetal bradycardia, • onset of labour • placental abruption (5–28%)
Fetal Surgery Fetal surgery is the performance of procedures on the fetus , designed to alter the natural history of a fetal disease that is diagnosed in utero
Physiological changes of pregnancy with anesthetic implications
Fetal physiology • Complex • Pathways for cortical transmission of noxious stimuli – 3rd Tri • Anesthetic requirement of fetal lambs is lower than pregnant ewe • Noxious stimuli - physiologic response evidenced by in cortisol, b-endorphin, in pulsatility index of MCA
Fetal physiology • Placenta - organ of respiration • Lung in utero - fetal lung fluid • Restricted egress of fluid - pulmonary hyperplasia • Continuous drainage - hypoplasia
Fetal Physiology • Parallel system • Myocardium - non-contractile elements • in preload – minimal SV & CO • Extrinsic compression of fetal heart • 16–22 wks - BV of FP unit 120–162 mL/kg • 2/3 of BV contained in placental portion of FP unit
Fetal Physiology • Coagulation factors produced in fetus • Do not cross placenta • Increase with gestational age • Fetal temp. linked to mat.temp. • Fetus exposed through hysterotomy can’t increase heat production • Hypothermia • Lack of shivering • No non-shivering thermogenesis • Immature skin barrier • Increased evaporative losses.
Uteroplacental blood flow • Intact UP blood flow - respiration & nutrition • Uterine blood flow = fetal umbilical venous PO2 • Uterine blood flow ∞ UPP • Uterine blood flow ∞ 1/UVR • Mat. hypotension, AC compression, ut.cont. decrease uterine blood flow
Uteroplacental blood flow • Studies comparing ephedrine and phenylephrine - no clinical diff. in neonatal outcome • More support to phenylephrine
Uteroplacental blood flow • Anesthetics - variable effects • Epidural anesthesia – no effect • IV induction agents – no effect • Volatile agents - decrease uterine tone • Light levels of volatile anesthesia – decrease in BP/ uterine vasodilation maintains blood flow • Deep levels of volatile anesthesia-uterine vasodilation cannot compensate for reduction in BP and CO and fetal acidosis occurs
Uteroplacental blood flow • Maternal hypocapnea - decrease uterine blood flow and fetal PaO2 • Hypercapnea may increase fetal PaO2 • Mechanical factors • Occlusion of the umbilical cord from loss of amniotic fluid or surgical manipulation • Integrity of UP interface must be maintained
Placental transport • Placental drug transfer • size, lipid solubility, protein-binding, pKa, pH of fetal blood, blood flow • LAs / opioids- acid diss.constant /trapped in ionized form in fetus if pH < drug’s pKa • Sevo/Des- low MW and lipid insoluble rapid transfer with high F/M ratio
F/M ratio • Hal/ iso - 0.7–0.9 / 0.7 • N2O - 0.83 • Thiopental crosses rapidly - 0.4 to 1.1 • Propofol - 0.5 to 0.85 • Diazepam - Within mins. 1.0/ 2.0 after an hour • Midazolam - 0.76 • Fentanyl - 0.16 to 1.2 • Vecuronium - 0.06–0.11 • Glycopyrrolate - 0.22 • Ephedrine - 0.7
Surgical issues Minimally invasive interventions • Most frequent • Fetal blood sampling, intrauterine transfusion, selective feticide, radiofrequency ablation of nonviable twin, fetal cardiac puncture for laser atrial septostomy • Uterine cavity accessed percutaneously with needles/sheaths • Noninvasive visualization -ultrasound / fetoscopes thru sheaths. • Endoscopes - 1.0 to 3.8 mm ED • Early or mid-gestation.
Open mid-gestation surgery • Maternal laparotomy • Incision transverse, more cephalad than LSCS • Only necessary anatomy delivered via hysterotomy • Rest of the fetus remains bathed in amniotic fluid • After surgery , fetus replaced in uterus • Warm Ringer’s lactate infused with antibiotics • Uterus closed and flap of omentum sewn over it
Ex-utero intrapartum therapy (EXIT) procedure • Performed near term to optimize lung maturity • Placental support for surgery • Laryngoscopy,rigid bronchoscopy, intubation, tracheostomy, resection of large lung lesions • Newborn in NICU
Anesthetic plan Teamwork/communication • Pediatric surgery, obstetrics, pediatric anesthesia, obstetric anesthesia, cardiology, radiology, neonatology, neonatal nursing, and operating room nursing • Weekly meetings • Multidisciplinary team meeting held with family to introduce the team, discuss details, and address concerns
Basic anesthetic objectives (1) maternal safety (2) avoidance of teratogenic agents (3) avoidance of fetal asphyxia (4) adequate fetal anesth.and monitoring (5) uterine relaxation (6) prevention of preterm labor.
Preoperative preparation • Standard anesthetic history and physical examination • Specific questions to evaluate respiratory or circulatory compromise • Severe symptoms of aortocaval compression would need meticulous left uterine displacement • GE reflux may change the anesthetic plan
Preop. preparation • Type and screen for minimally invasive fetoscopic cases • Open cases - cross-matched blood for mother • O-neg blood for fetus cross-matched with maternal sample. • Location of placenta affects patient positioning • Estimated fetal weight used to determine dosage of fetal drugs
Preoperative preparation • Fetal ultrasound, echocardiography,MRI • Aspiration prophylaxis
Minimally invasive -Anaesthesia • Local anesthetic infiltration/sedation/ neuraxial/GA • Medications can be given directly to the mother thus indirectly to fetus • Can also be given directly to the fetus by surgical team • Intramuscular, intravenous, intracardiac • Fetal monitoring - fetal heart rate by ultrasound/Echocardiography in cardiac interventions.
TTTS protocol • Maternal fasting, IV catheter, aspiration prophylaxis, tocolysis • Opioids/ benzodiazepines or propofol • Diazepam vs remifentanil (0.1 mg/kg/min) • Remi had less fetal movement and reported better operating conditions • Tocolysis – preop. indomethacin,postop. magnesium infusions, and post-discharge oral nifedipine or s/c terbutaline • Close accounting of irrigation
Anesthetic for complicated twin gestations for balloon dilation of fetal aortic stenosis • Maternal general endotracheal anesthesia • IM fentanyl, vecuronium, atropine to fetus
Open mid-gestation-Anesthesia • Intense uterine relaxation • fetal manipulation • Prevent initiation of labor • Preinduction epidural • General endotracheal anesthesia with high-dose volatile agents • Desflurane -rapid emergence from deep anesthesia • IV NTG • Mat. hypotension
Open mid-gestation-Anesthesia • Large-bore peripheral IV line • Arterial catheter • Judicious IV fluids • Vasopressors
Open mid-gestation-Anesthesia • After exposure of the fetus, IM fentanyl (20 mcg/kg), atropine (20 mcg/kg), vecuronium (0.2 mg/kg) • Amniotic fluid replaced with continuous infusion of warmed Ringer’s lactate using a Level 1 infusion device • Monitoring of fetus includes direct observation, HR by ultrasound,fetal echo., pulse oximetry • Fetal SaO2- 40% to 70%
Open mid-gestation-Anesthesia • Watch for fetal bradycardia,maternal or fetal bleeding, maternal BP • Careful observation and understanding of the events • Decrease in fetal SaO2/bradycardia indicates fetal distress • Blood products • In large chest lesions, transfusion of warm PRBC improves fetal hemodynamic stability
Open mid-gestation-Anesthesia • With closure of the uterus, tocolysis with bolus of IV magnesium sulfate • Epidural block initiated/ volatile anesthetic reduced. • Extubated awake
Intraoperative fetal resuscitation • Fetal distress during surgery • cord compression or kinking, placental separation, high uterine tone, mat. hypotension, hypoxia, or anemia, Fetal hypothermia, hypovolemia and anemia
Intraoperative fetal resuscitation • Cardiac dysfunction from high doses of volatile anesthetics • Good condition of the mother ensured • Umbilical cord patency, aortocaval compression avoided, integrity of the uteroplacental unit confirmed • Uterine displacement/admin.of mat. vasopressors, admin.of medications or blood directly to the fetus
Anesthetic principles for pregnant women undergoing EXIT surgery • Understanding the anatomical and physiological changes of pregnancy • Maintaining an adequate uteroplacental blood flow • Avoiding and promptly treating hypotension • Avoiding aorto-caval compression • Selecting anesthetic drugs and techniques with a good record for safety
Selecting anesthetic drugs and agents with rapid titratability • Providing adequate fetal surveillance until delivery • Making appropriate perioperative adjustments in technique as guided by the results • Preventing placental separation following partial delivery of the fetus • Maintaining the fetoplacental circulation following partial delivery of the fetus • Providing fetal anesthesia for fetal airway manipulations
Fetal magnetic resonance imaging scan at 28 wks gestation revealing an encapsulated cervical mass arising from right anterolateral region of fetal neck