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
  • Stroke
  • Subarachnoid hemorrhage
  • Epilepsy
  • Status epilepticus
    • Multiple sclerosis
      • Consider a theoretical risk of neurotoxicity to demyelinated nerves with regional anesthesia
    • Myasthenia gravis
      • Perform instrumental delivery as muscles fatigue quickly
      • Regional anesthesia is preferred over general anesthesia
      • Avoid magnesium as it can precipitate a myasthenic crisis
• Respiratory disease
  • Asthma
    • Screen for pulmonary hypertension
• Hematological disease
  • Increased risk of VTE, e.g. Factor V Leiden, antiphospholipid syndrome
  • Increased risk of bleeding, e.g. von Willebrand’s disease, thrombocytopenias
  • Reduced oxygen-carrying capacity, e.g. sickle cell disease, thalassemia, spherocytosis
    • Regional anesthesia is safe to use but pay attention to the timing of anticoagulant if used
    • Therefore, provide a recent assessment of platelet count in thrombocytopenia
• 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

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:
    • Alternative laryngoscope
    • Remove cricoid pressure
  • 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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