Challenges in obstretic anesthesiology - NYSORA

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Challenges in obstretic anesthesiology

Learning objectives

  • Anesthetic management of medical problems in obstetric patients
  • Safe obstetrical general anesthesia
  • Methods of pain relief during labor

Definition and mechanisms

  • Pregnant women may need anesthesia at any stage of gestation due to incidental surgery (e.g. appendicitis), trauma, delivery, or complications in the immediate postnatal period (e.g. bleeding, breast abscess)
  • As pregnancy progresses, multisystemic physiological changes develop rapidly
  • The obstetric anesthesiologist must understand these to provide optimum care to pregnant women
  • Consider:
    • Significant cardiovascular or cerebrovascular disease
    • Significant respiratory disease, which may worsen throughout pregnancy
    • Morbid obesity (BMI >40) or super morbid obesity (BMI >50)
    • Significant hematological disease which may previously have resulted in failure to reach viable gestation
    • Corrected or palliated congenital heart disease
  • Be aware that pregnant patients are more sensitive to the effects of general anesthesia than non-pregnant patients

Anesthetic management of medical problems in obstetric patients

  • Acquired cardiac disease
    • Ischaemic heart disease (obesity and advanced age is increasingly seen in the obstetric population)
    • Aortic dissection
    • Cardiomyopathy
    • Symptomatic valvular heart disease
    • Sudden adult death syndrome (SADS)
    • Antenatal management:
      • Assess symptoms and functional status (NYHA class)
      • Review recent ECG and echocardiography
      • Multidisciplinary planning for labor and delivery
    • Labor and delivery:
      • Perform continuous maternal monitoring with ECG and invasive blood pressure monitoring for high-risk patients
      • Provide epidural analgesia
      • Be aware of the hypertensive response to laryngoscopy in case of general anesthesia
    • Postnatal management:
      • Be cautious with uterotonic agents due to side effects
      • Perform hemodynamic monitoring during the first 24 hours because of the risk of decompensation with autotransfusion postpartum
  • Congenital cardiac disease
    • Maintain preload
      • Avoid prolonged fasting
      • Administer IV fluids
    • Maintain afterload
      • Avoid spinal anesthetic 
      • Administer phenylephrine for hypotension (or noradrenaline in on-responders)
      • Administer oxytocin slowly (2 units/minute) 
    • Avoid tachycardia
      • Administer effective analgesia
      • Perform early cardioversion for any tachyarrhythmia
    • Keep pulmonary vascular resistance low
      • Administer oxygen
      • Avoid hypercarbia by preventing sedation
  • Neurological disease
  • Respiratory disease
  • Hematological disease
  • Back problems
    • Spinal surgery
      • Regional anesthesia is safe to use in most types
      • Avoid scar sites
    • Scoliosis surgery
      • Avoid regional anesthesia in women with implanted rods 
    • Spina bifida
      • Exclude tethered spinal cord
      • Regional anesthesia can be applied at an unaffected level if tethered spinal cord is excluded
      • Be cautious of accidental dural punctures
      • Reduce the epidural volume as dural permeability is reduced

Maternal-to-fetal transfer

Medication classExamplesCrossing of uteroplacental barrier?
Intravenous agentsThiopental
Inhalational agentsIsoflurane
Neuromuscular blocking agentsVecuronium
Neuromuscular blocking reversal agentsNeostigmine
Anticholinergic agentsAtropine

Obstetric general anesthesia

  • Pre-OR preparation
    • Airway assessment
    • Fasting status
    • Antacid prophylaxis
    • Intrauterine fetal resuscitation if appropriate
  • Rapid sequence induction
    • Check airway equipment and IV access
    • Optimize position: head up + left uterine displacement
    • Pre-oxygenate and consider nasal oxygenation
    • Perform cricoid pressure
    • Deliver appropriate induction and neuromuscular blocker doses
    • Consider facemask ventilation
  • 1st intubation attempt:
    • If poor view of the larynx, optimize the attempt by:
      • Reducing/removing cricoid pressure
      • External laryngeal manipulation
      • Repositioning head/neck
      • Using bougie/stylet
    • Verify successful tracheal intubation or if the intubation attempt fails, ventilate with a facemask
  • 2nd intubation attempt:
    • Consider:
    • Verify successful tracheal intubation or if the intubation attempt fails, ventilate with a facemask
  • Declare failed intubation:
    • Priority is to maintain oxygenation
      • Supraglottic airway device
      • Facemask – oropharyngeal airway
  • Further management: see non-obstretic surgery

Pain relief during labor

  • During the first and early second stages of labor, visceral pain (mediated by the T10 to L1 spinal segments) is experienced
    • This is usually felt in the abdomen, sacrum, and back 
  • In the latter part of the first stage and into the second stage, somatic pain (mediated via T12-L1 and S2-4) is experienced
    • This is located in the vagina, rectum, and perineum

Methods for pain relief during labor

See caesarean delivery for anesthesia


Suggested reading

  • Delgado, C., Ring, L., Mushambi, M.C., 2020. General anaesthesia in obstetrics. BJA Education 20, 201–207.
  • Pollard BJ, Kitchen, G. Handbook of Clinical Anaesthesia. Fourth Edition. CRC Press. 2018. 978-1-4987-6289-2.

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