Anaesthesia for Non Obstetric Surgery in Pregnant Patients Presenter: Dr. Satya Pal Moderator: Dr. Geetanjali University College of Medical Sciences & GTB Hospital, Delhi email: anaesthesia.co.in@gmail.com www.anaesthesia.co.in

Incidence 0.3% to 2.2% of pregnant women undergo surgeries Annual incidence - 75,000 – 80,000 (USA) Centralized data unavailable in India Commonest surgery - Appendicectomy

Incidence Am J Obstet Gynecol 1989 Trimester breakdown of nonobstetric surgery undertaken during pregnancy. A Am J Obstet Gynecol 1989

Surgeries in pregnancy Pregnancy related Cervical encirclage Fetal surgery Ovarian Cystectomy Not related to pregnancy Appendicectomy, Cholecystectomy Trauma Malignancies

How these patient are different from other surgical patients? Two patients - mother - fetus Physiological changes in mother

Why this topic is important? Must ensure safe anaesthesia for both mother and child Standard anaesthetic procedure may have to be modified to accomodate both maternal physiological changes and presence of fetus Risk to the fetus is more- the effect of disease process, teratogenicity of anaesthetic agents, intraoperative impairment of uteroplacental circulation, and risk of abortion or preterm delivery

KEY AREAS Normal alterations in maternal physiology during pregnancy The potential fetal effects from anaesthesia and surgery Maintenance of uteroplacental perfusion and fetal oxygenation Practical considerations Importance of maternal counselling and reassurance Special situations OPTIMAL ANAESTHETIC MANAGEMENT OF THESE PREGNANT PATIENTS AND THEIR FETUSES REQUIRES AN UNDERSTANDING OF THESE KEY AREAS

Altered maternal physiology Respiratory system: ↑ O2 consumption & ↓ FRC rapid desaturation or hypoxemia ↑ Alveolar ventilation  chronic respiratory alkalosis & ↓ bicarbonate and base buffer ↑ mucosal vascularity & weight gain difficult mask ventilation or intubation Cardiovascular system: Supine hypotension syndrome ↓ uteroplacental perfusion Distention of epidural venous plexus ↑ likelihood of intravascular injection and enhanced spread of LA

Altered maternal physiology Hematological changes ↑ Blood volume with lesser increase in RBCs volume dilutional anemia ↑ Factor I, VII, VIII, X, XII & FDP  Increased risk of thromboembolic complications Benign leukocytosis difficult to differentiate from infection Gastrointestinal system changes ↓ LES tone, distortion of gastropyloric anatomy & ↑ gastric pressure from gravid uterus risk of regurgitation and aspiration

Altered maternal physiology… Altered response to anaesthesia Alveolar hyperventilation, reduction of FRC and reduction of MAC rapid induction of general anaesthesia ↓ thiopental requirements ↓ protein binding due to low albumin  ↑ free fraction of drugs ↑ sensitivity to peripheral neural blockade ↓ L.A. dose requirement

KEY AREAS Normal alterations in maternal physiology during pregnancy The potential fetal effects from anaesthesia and surgery Maintenance of uteroplacental perfusion and fetal oxygenation Practical considerations Importance of maternal counselling and reassurance Special situations The fetal effects of AA has already been discusses in detalis in previous seminar, we will be discussing the teratogenic effects of AA

FETAL EFFECTS Teratogenicity Any significant postnatal change in function or form in an offspring after prenatal treatment Factors that influence teratogenicity of a drug Species susceptibility Threshold or amount of exposure Duration and timing of administration Genetic predisposition Manifestation of teratogenicity (Death, Structural abnormality, Growth restriction, functional deficiency)

FETAL EFFECTS… Teratogenicity… Maximum sensitivity of organs for development of structural abnormalities Brain 18-36 days Heart 18-40 days Eyes 24-40 days Limbs 24-36 days Gonads 37-50 days Organogenesis: complete at 13 weeks day 31 to day 71after 1st day of last menstrual period

FETAL EFFECTS… Documented teratogens: Radiation increased risk of malignant disease, genetic disease, cong. malformation &/or fetal death Maternal metabolic imbalance Alcoholism, cretinism, diabetes, folic acid deficiency, hyperthermia, prolonged hypoxia, hypercarbia and severe hypoglycemia Infection CMV, Herpes virus, Parvo virus B-19, rubella virus, toxoplasmosis Drugs

FETAL EFFECTS… Radiology: a threat?? Effects are dose related Less than 50 mGy is safe Absorbed fetal dose for all conventional radiographic imaging is less than 50 mGy “No single diagnostic procedure results in a radiation dose that threatens the well-being of the developing embryo and fetus” (American College of Radiology)

Diagnostic ultrasonography: Considered to be devoid of embryotoxic effects Potential side effects Fetal hyperthermia – with prolonged scans Post-natal neurobehavioral effects – with repeated exposures Hande et al. Teratogenic effects of repeated exposures to X-rays and or ultrasound in mice. Neurotoxic Teratol 1995

Documented teratogenic drugs (Adapted: ACOG Educational Bulletin ) ACE inhibitors Lithium Alcohol Mercury Androgens Phenytoin Antithyroid drugs Vitamin A derivatives Carbamazepine Streptomycin/kanamycin Chemotherapy agents Tetracycline Cocaine Thalidomide Coumadin Trimethadione Diethylstilbestrol Valproic acid Lead

FETAL EFFECTS… Anaesthetic agents and teratogenicity Teratogenic effects of anaesthetic agents are probably minimal to non-existent and have never been conclusively documented

FETAL EFFECTS… Safe drugs: I/V induction agents Narcotics Neuromuscular blockers Inhalational agents Local anaesthetics Drugs of concern: Nitrous oxide, BZD

FETAL EFFECTS… Nitrous oxide Animal studies Weak teratogen in rodents Interferes with function of methionine synthetase by oxidation of vitamin B12 decreased THF decreased DNA synthesis Decreased uterine blood flow : prevented by addition of halogenated inhalational agents

FETAL EFFECTS… Nitrous oxide… Human studies No proved teratogenicity Significant exposure for prolonged duration results in altered enzyme activity No teratogenic effects in clinically administered dose.

FETAL EFFECTS… BENZODIAZEPINES (BZD) Earlier retrospective studies: Association between maternal diazepam ingestion during 1st trimester and infant with cleft lip and palate Later prospective studies: - No higher risk when used in 1st trimester Long term maternal administration – fetal BZD dependence & withdrawal Peripartum administration – Fetal hypotonia, hypothermia, respiratory depression, feeding difficulties

FETAL EFFECTS… A single shot of short acting BDZ or Nitrous oxide in clinically administered anaesthetic concentration is unlikely to have any teratogenic effects

FETAL EFFECTS… BEHAVIORAL TERATOLOGY Behavioral abnormality in absence of any observable morphological changes CNS is specifically sensitive during period of major myelination which extends from 4th IU month to 2nd postnatal month Animals prenatal administration of systemic drugs e.g., Barbiturates, meperidine, promethazine & halothane behavioral changes Human implication remains unknown

FETAL EFFECTS… “There are not adequate data to extrapolate the animal finding to humans” (Anesthetic & Life Support Drug advisory Committee of US FDA)

Fetal effects… To summarize, anaesthesia and surgery are associated with higher incidence of abortion, IUGR and perinatal mortality. These adverse outcomes can often be attributed to the procedure, the site of the surgery (e.g., proximity to the uterus), and/ or the underlying maternal condition No evidence that anaesthesia results in overall increase in congenital abnormality No evidence of clear relation between outcome and type of anaesthesia EFFECT OF ANAESTHESIA ON FOETUS

KEY AREAS Normal alterations in maternal physiology during pregnancy The potential fetal effects from anaesthesia and surgery Maintenance of uteroplacental perfusion and fetal oxygenation Practical considerations Importance of maternal counselling and reassurance Special situations OPTIMAL ANAESTHETIC MANAGEMENT OF THESE PREGNANT PATIENTS AND THEIR FETUSES REQUIRES AN UNDERSTANDING OF THESE KEY AREAS

Uteroplacental perfusion and fetal oxygentation Fetal oxygenation depends on maternal oxygen delivery and uteroplacental perfusion Most serious risk during nonobstetric surgery is Intrauterine asphyxia Maintenance of fetal well being : Maternal oxygenation Maternal carbon dioxide tension Uterine blood flow

Uteroplacental perfusion and fetal oxygentation… Maternal oxygenation: Severe maternal hypoxia can occur with: difficult / oesophageal intubation pulmonary aspiration total spinal anaesthesia systemic LA toxicity Moderate hyperoxia improves fetal oxygenation and is not associated with intrauterine retrolental fibroplasia and premature DA closure Any complication LIKE CAN cause profound maternal hypoxemia and is a potential threat to the fetus.. On contrary

Uteroplacental perfusion and fetal oxygentation… Maternal CO2: Fetal CO2 correlates to maternal levels Maternal hyperventilation can results in Umbilical artery constriction Alkalosis: shift maternal oxyhemoglobin dissociation curve to left. Hypocapnia: ↑ ventilation  ↓ venous return ↓ cardiac output  ↓ uterine blood flow.

Factors affecting the Uteroplacental perfusion Maternal hypotension deep levels of anaesthesia high levels of spinal or epidural blockade aortocaval compression, hemorrhage/ hypovolumia Anaesthetic agents causing uterine vasoconstriction or hypertonus (eg. ketamine>2mg/kg, toxic doses of LA) Catecholamines Pain, anxiety, light anaesthesia  increased plasma catecholamines decreased UBF Factors directly REDUCING UBF…………uterine hypertonicitydecrease uterine blood flow volatile anaesthetic agents: low conc.uterine relaxation & vasodilation maintain UBF high conc.falling cardiac outputprogressive fetal hypoxia & acidosis

KEY AREAS Normal alterations in maternal physiology during pregnancy The potential fetal effects from anaesthesia and surgery Maintenance of uteroplacental perfusion and fetal oxygenation Practical considerations Importance of maternal counselling and reassurance Special situations OPTIMAL ANAESTHETIC MANAGEMENT OF THESE PREGNANT PATIENTS AND THEIR FETUSES REQUIRES AN UNDERSTANDING OF THESE KEY AREAS

PRACTICAL CONSIDERATIONS Timing of surgery Fetal monitoring Full stomach precautions Left uterine displacement Anaesthetic considerations Tocolytic agents

PRACTICAL CONCERNS… When to do the surgery?? Depends on the balance between maternal and fetal risk and urgency of the surgery 1st trimester – Organogenesis Increased fetal risk for teratogenesis and abortion 3rd trimester – Peak of physiological changes of pregnancy Increased maternal risk Increased risk of preterm labour Thus 2nd trimester is considered to be a ideal time for non emergency, essential surgeries

PRACTICAL CONCERNS… When to do the surgery?? Carvalho B, Anesth Analg Suppl IARS

PRACTICAL CONCERNS… Fetal monitoring Intermittent or continuous FHR monitoring should be considered for major surgical procedures whenever technically feasible: Ease of monitoring Type & site of surgery (difficult during abdominal surgery) Gestational age (after 18-20 wks) Tool to monitor intrauterine fetal well being Done by transabdominal doppler or vaginal doppler probe Requires the presence of a trained practitioner to monitor and interpret the tracing Transabdominal monitoring may not be possible during abdominal surgeries or when the mother is obese so vaginal doppler probe may be used in selected patients

Good indicator of fetal well being after 25-27 wks FHR variability Good indicator of fetal well being after 25-27 wks Loss of beat to beat variability and decreased baseline FHR are common – Anaesthetic agent administration Declerations suggests fetal hypoxemia Causes of FHR declerations Inadvertent maternal hypoxemia, or inadequate uterine perfusion  evaluation of maternal position, B.P, oxygenation, acid base status and inspection of surgical sites as retractors may impair uterine perfusion.

PRACTICAL CONCERNS… Anaesthetic considerations in1st Trimester Maternal ↑ oxygen requirement Modified drug pharmacokinetics Careful airway manipulation Fetal Risk of teratogenicity Impaired UBF

PRACTICAL CONCERNS… Anaesthetic considerations in 2nd and 3rd trimester Maternal Prone to hypoxia Aspiration prophylaxis Preparation for difficult airway Increased risk of thromboembolic complications Avoid hyperventilation

PRACTICAL CONCERNS... Fetal Surgery related Premature labour / IUGR Intrauterine asphyxia Surgery related Disease related problem Diagnostic difficulties Prolonged exposure to anaesthetics Surgical manipulations – ↑ fetal risk Anatomic and surface landmarks unreliable Diagnostic difficulties as nausea, vomiting, constipation and distension are commmon symptoms of normal pregnancy and abdominal pathology, second increase TLC, Thirdly difficulty in performing radiology

PRACTICAL CONCERNS…. DIAGNOSTIC DIFFICULTY As nausea, vomiting, constipation, and distention are common symptoms of both normal pregnancy and abdominal pathology Increase WBC count Reluctance to perform necessary studies involving radiation Anatomic and surface landmarks can be unreliable Because of these diagnostic difficulties, the disease (e.g., intrabdominal pathology) may be advanced at the time of surgery

PRACTICAL CONCERNS… TOCOLYTICS AGENTS Prophylactic use in nonobstetric surgery is controversial May be considered abdominal surgeries involving uterine manipulations or Surgeries with high risk of premature labour i.e., cervical encirclage Uterine contractions should be monitored during the surgery and tocolytic therapy to be instituted if required Not recommended at or after 34 wks Do not affect the outcome

PRACTICAL CONCERNS… Tocolytic agents Drugs Side effects ß2 agonist Terbutaline Ritodrine Isoxsuprine fetal tachycardia, hypoglycemia, hypotension, Pulmonary edema, myocardial ischemia Calcium channel blockers Nifedipine (one of the most commonly used) transient hypotension Magnesium sulphate least commonly used interaction with NMBs, CNS depression Indomethacin peptic ulcer, thrombocytopenia, premature closure of D.A. Atosiban (newer agent) oxytocin antagonist Blunts Ca2+ influx in myometrium and inhibit contractility

KEY AREAS Normal alterations in maternal physiology during pregnancy The potential fetal effects from anaesthesia and surgery Maintenance of uteroplacental perfusion and fetal oxygenation Practical considerations Importance of maternal counselling and reassurance Special situations OPTIMAL ANAESTHETIC MANAGEMENT OF THESE PREGNANT PATIENTS AND THEIR FETUSES REQUIRES AN UNDERSTANDING OF THESE KEY AREAS

Counselling and reassurance Patient should be reassured about the safety of anaesthesia and the lack of documented associated teratogenicity Warned about the increased risk of 1st trimester miscarriage and premature delivery in later trimesters Educate the patient about the symptoms of premature labour and reinforce the need of left uterine displacement Documentation of details of the risk discussed should be maintained in patients records

ANAESTHETIC MANAGEMENT

Pre-anaesthetic preparation.. Counselling and reassurance Consult obstetrician & discuss about the use of tocolytics Overnight fast Aspiration prophylaxis Anxiolytic premedication- to allay anxiety and apprehension Transport in left lateral position O.T. preparation – drugs, machine, difficult airway cart, suction and monitors Anxiolysis as it can decrease UBF

ANAESTHETIC MANAGEMENT… Choice of Anaesthesia Choice of Anaesthetic technique depends on- Patient’s present surgical status (site and nature of surgery) Present gestational age of the fetus Pregnancy induced physiological changes Other coexisting comorbidities No technique has been proven to have superiority over the other in fetal outcomes Regional techniques may be preferable Safe anaesthetic management is more important than particular agent or technique

AIM : To maintain oxygenation, normotension, eucapnia and euglycemia

ANAESTHETIC MANAGEMENT… Monitoring Maternal monitoring: Noninvasive / invasive blood pressure Electrocardiography Pulse oximetry Capnography Temperature monitoring Use of peripheral nerve stimulator Blood glucose levels Fetal monitoring: External doppler device (FHR ) Tocodynamometer (Uterine contractility) Glucose levels during prolonged surgery or patients GDM

ANAESTHETIC MANAGEMENT… .. General anaesthesia Maintain left uterine displacment Preoxygenation Rapid sequence induction (Thiopent. sod. & succinyl choline, cricoid pressure  tracheal intubation using cuffed E.T. tube) Maintenance : A moderate conc. of inhalational agent ( ≤ 2 MAC) with high conc. of oxygen (FiO2 = 0.5) is recommended. The use of nitrous oxide should be limited during extremely long operations in first trimester by giving high conc of oxygen Inhalational agents decreases uterine tone and inhibits contractions, in concentrations below 2 MAC TO PREVENT FALL IN CO

Opioids and induction agents decreases FHR variability to greater extent than volatile agents Positive pressure ventilation may reduce UBF Avoid hyperventilation Patients on magnesium for tocolysis – reduce dose of NMBs Reversal agent to be given slowly (increased release of Ach increased uterine tone and preterm labour) Extubation when fully awake after return of protective airway reflexes

ANAESTHETIC MANAGEMENT..… Regional anaesthesia Advantages: Minimal fetal drug exposure Avoidance of complications of general anaesthesia If no sedative or narcotics are supplemented – no change in FHR variations to confuse interpretation Post operative analgesia

Management of regional anaesthesia Pre-op preparation and monitoring same as of General anaesthesia Reduced LA requirement / ↑ LA Toxicity Careful aspiration and test dose Avoid hypotension i.e., adequate preloading, maintain left uterine tilt, choice of vasopressor Patients on magnesium are more prone to hypotension, often resistant to treatment with vasopressors

ANAESTHETIC MANAGEMENT… Postoperative management Oxygenation in left uterine tilt Vitals monitoring Obstetrician consultation for FHR & uterine activity monitoring Pediatric consultation in case of premature labour Adequate pain relief – reduce the risk of premature labour Tocodynamometry is useful in high risk patients as postoperative analgesia may mask awareness of early contractions and delay tocolysis Early mobilization or DVT prophylaxis if required

ANAESTHETIC MANAGEMENT… Postoperative Pain management Painincreased endogenous catecholamines uterine vasoconstrictiondecreased UBFintrauterine hypoxia Techniques: Nerve blocks Local infiltration Opioids NSAID NSAIDS  1st and 2nd trimester - safe 3rd trimester - risk of premature closure of DA, Pulm HTN, delayed labour NSAID can be used before 32 wks and Acetaminophen is safe

ANAESTHETIC MANAGEMENT… Recommendations approved by American Society of Anaesthesiologists (ASA) and American College of Obstetricians and Gynecologists (ACOG) 2011 No currently used anaesthetic agents have been shown to have any teratogenic effects in humans when using standard concentrations at any gestational age Fetal heart rate monitoring may assist in maternal positioning and cardiorespiratory management, and may influence a decision to deliver the fetus

Recommendations… It is mandatory to obtain an obstetric consultation before performing any non obstetric surgery or any invasive procedures A pregnant woman should never be denied indicated surgery, regardless of trimester. Elective surgery should be postponed If possible, non-urgent surgery should be performed in the second trimester when preterm contractions and spontaneous abortion are least likely.

KEY AREAS Normal alterations in maternal physiology during pregnancy The potential fetal effects from anaesthesia and surgery Maintenance of uteroplacental perfusion and fetal oxygenation Practical considerations Importance of maternal counselling and reassurance Special situations OPTIMAL ANAESTHETIC MANAGEMENT OF THESE PREGNANT PATIENTS AND THEIR FETUSES REQUIRES AN UNDERSTANDING OF THESE KEY AREAS

Special situation – Laparoscopy No longer a contraindication in pregnant patients Concerns: - Uterine and fetal trauma - Fetal acidosis from absorbed carbon dioxide. - Decreased maternal cardiac output and uteroplacental perfusion due to increased abdominal pressure.

Special situation – Laparoscopy Guidelines by Society of American Gastrointestinal Endoscopic Surgeons (SAGES) 2008 Safe during any trimester of pregnancy Obtain preoperative obstetrician consultation Intermittent lower extremity pneumatic compression devices to prevent venous stasis The fetal heart rate and uterine tone should be monitored in both preoperative and postoperative periods End tidal CO2 should be maintained

Special situation – Laparoscopy Left uterine displacement should be maintained An open (Hassan) technique, a veres needle or an optical trocar technique to enter abdomen Low pneumoperitoneum pressures (10-15mm Hg) should be used Tocolytic agents should not be used prophylactically but should be considered when evidence of preterm labour is present

Special situation – Fetal surgery Anaesthetic considerations remains similar to those of non obstetric surgeries Two surgical patients Maternal safety is important Choice of anaesthetic technique Minimally invasive endoscopic procedure – Neuraxial anaesthesia Open intrauterine procedures – General anaesthesia

Special situation – Fetal surgery…. Important considerations Consider anaesthetic requirement of fetus including amnesia, analgesia and immobilty Control of uterine tone is essential More intensive intraop FHR monitoring

Special situation – Electroconvulsive Shock Therapy Used to treat major depression and BPD during pregnancy when rapid control of symptoms is needed Advantage – Avoids potential teratogenicity from psychotropic medications Not a risk factor for premature labour, miscarriage or stillbirth Anaesthetic management Confirm the absence of uterine contractions using tocodynamometry before and after ECT Monitor FHR before and after ECT

Special situation – Neurosurgery (e.g., Aneurysm, AV malformation) Hypotensive anaesthetic techniques ( 25 – 30% reduction in SBP or mean BP less than 70 mmHg) can cause decrease in UBF Dose (less than 0.5 mg/kg/hr) and duration of Sodium Nitroprusside should be limited FHR monitoring should be performed continuously specially if induced hypotension or hyperventilation is planned so that necessary adjustments can be made if fetal distress occurs Hypovolemia and very large doses of mannitol should be avoided as they cause fetal dehydration Endovascular treatments – uterine shielding during periods of radiation

Special situation – Trauma during pregnancy Trauma is the leading cause nonobstetric cause of morbidity and mortality Primary management goals are similar to the care of nonpregnant trauma cases Avoidance of hypoxia, hypotension, acidosis and hypothermia are important for the maintenance of UBF and fetal well being More prone to develop pulmonary edema In stable patients without ongoing blood loss – Conservative fluid management CVP monitoring should be considered if renal insufficiency or fluid overload occurs

Special situation – Trauma during pregnancy… Primary aim should be optimization of the mother and the obstetric management is planned later No radiological tests should be withheld because of fetal concerns, uterus should be shielded during radiation procedures Indications for an Emergency Cesarean delivery in a pregnant trauma patients Traumatic uterine rupture Stable mother with viable fetus that is in distress An unsalvagable mother who still has a viable fetus A gravid uterus that is interfering with intraoperative surgical repair

References Obstetric Anaesthesia, Principles and Practice. David H Chestnut, 4th Ed Miller’s anesthesia. Ronald D Miller. 7th ed. Wylie and Churchill Davidson’s ‘A Practice of Anaesthesia’ 7th ed. Clinical Anesthesia; Barash, Cullen, Stoelting, 6th edition Yao & Artusio’s Anesthesiology. 7th edition Nonobstetric surgery during pregnancy, ACOG committee opinion, No. 474, Feb 2011 Roisin Ni M, David A. Anesthesia on pregnant patients for nonobstetric surgery. Journal of clinical anesthesia (2006) 18, 60-66

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