What are the increased risks for obstetric anesthesia in patients with a Body Mass Index (BMI) over 40?

From the Guidelines

Patients with a BMI over 40 are at a significantly increased risk for obstetric anesthesia complications, including difficult airway management, challenging neuraxial anesthesia placement, and increased risk of venous thromboembolism (VTE) and postpartum hemorrhage, as highlighted in the 2015 guidelines by the Association of Anaesthetists of Great Britain and Ireland 1.

Key Risks and Considerations

• Increased risk of aorto-caval compression due to positioning challenges
• Higher likelihood of difficult vascular access, necessitating early establishment of access in labor
• Greater technical challenges with general anesthesia and central neuraxial blockade, potentially leading to increased decision-to-delivery intervals for category-1 or -2 caesarean sections
• Elevated risk of VTE, with recommendations for higher dosing of anticoagulants as per the Royal College of Obstetricians and Gynaecologists’ Green-top Guideline 1
• Importance of early anesthesia consultation, especially for women with a BMI greater than 40 kg/m2, to discuss limitations and risks of anesthesia during delivery, as recommended in the 2020 systematic review on guidelines for managing pregnant women with obesity 1

Management Recommendations

• Early epidural placement should be considered to mitigate potential complications
• Use of ultrasound guidance for procedures to improve success rates and reduce complications
• Potentially lower initial doses of neuraxial medications with careful titration based on response to minimize risks
• Vigilant monitoring postoperatively due to higher rates of respiratory complications, including obstructive sleep apnea and atelectasis
• Consideration of antenatal thromboprophylaxis, especially in cases of extreme obesity or hospitalization prior to delivery, as suggested by various clinical practice guidelines 1

From the Research

Increased Risks for Obstetric Anesthesia in Patients with BMI over 40

The increased risks for obstetric anesthesia in patients with a Body Mass Index (BMI) over 40 include:

• Difficult airway management and increased risk of aspiration of gastric contents 2, 3
• Challenging neuraxial techniques due to poor anatomical landmarks and potential for technical difficulties 2, 3
• Increased risk of postpartum wound infections and deep venous thromboembolism 2
• Higher risk of cesarean delivery and associated complications 2, 3
• Comorbidities such as hypertension, diabetes, and obstructive sleep apnea, which can further complicate anesthetic management 4, 2, 3
• Need for careful preoperative preparation, including evaluation by an anesthesiologist, antacid prophylaxis, thromboprophylaxis, and antibiotic prophylaxis 2, 3
• Potential for intraoperative complications, such as difficult intubation, respiratory and hemodynamic instability, and massive hemorrhage 4, 3
• Importance of postoperative care, including efficacious analgesia, physiotherapy, and early mobilization, as well as monitoring and vigilance in an intensive care unit or step-down units 2, 3

Anesthetic Considerations

Anesthetic considerations for patients with BMI over 40 include:

• Preference for regional anesthesia over general anesthesia, unless contraindicated 2, 3
• Use of a combined spinal epidural technique or continuous spinal technique, which may be technically easier and allow for extension of the block as required 3
• Importance of intraoperative lung-protective strategies, recruitment maneuvers, and multimodal analgesia 4, 3
• Need for careful monitoring of ventilation and hemodynamic status, as well as thromboprophylaxis and antibiotic prophylaxis 2, 3

Preoperative Preparation

Preoperative preparation for patients with BMI over 40 includes:

• Evaluation by an anesthesiologist to assess the risk of anesthetic complications and develop a plan for anesthetic management 2, 3
• Institution of antacid prophylaxis, thromboprophylaxis, and antibiotic prophylaxis to reduce the risk of complications 2, 3
• Optimization of comorbidities, such as hypertension, diabetes, and obstructive sleep apnea, to reduce the risk of anesthetic complications 4, 2, 3