Anaesthesia for the parturient with obesity

Learning objectives.

By reading this article, you should be able to:

• •Discuss the preoperative considerations for the parturient with obesity.
• •Describe the neuraxial and non-neuraxial options for delivering analgesia and anaesthesia in the peripartum period.
• •Discuss the complications associated with obesity in pregnancy.

Key points.

• •Maternal obesity is increasing worldwide and is associated with adverse outcomes for both mother and baby.
• •Multidisciplinary team involvement is vital for managing the parturient with obesity.
• •Neuraxial analgesia should be offered early in labour.
• •Continuous neuraxial techniques are optimal for Caesarean delivery.
• •General anaesthesia poses significant risk in these high-risk patients.

Obesity is a worldwide health problem; its prevalence is increasing in all age groups, including those of childbearing age. Currently in the UK, 23.1% of the antenatal population is obese, with prevalence being highest amongst minority ethnic groups and those from low socio-economic background.^1,2 Similar data have been reported from the USA and Australia.³ Although once thought to be a disease of high-income countries, the rate of maternal obesity is also increasing in countries, such as India, Bangladesh and Nepal, highlighting the global nature of the disease.⁴ These rising rates of obesity are a significant concern for obstetric units, as they are associated with adverse outcomes for both mother and baby. Table 1 summarises the key maternal and fetal complications associated with obesity. Most worrying is the association between maternal obesity and maternal mortality. In the UK, the Confidential Enquiry into Maternal Deaths (CEMD) reports since 2003 have consistently identified that obesity is over-represented in parturients who died from direct causes. In the most recent triennial CEMD report (2015–2017), 34% of women who died were obese and 24% were overweight.⁵ Although the overall contribution of anaesthesia to maternal death remains low, obesity is a risk factor for anaesthesia-related maternal morbidity and mortality in CEMD reports since 2010. It is therefore not surprising that current guidance for managing pregnant patients with obesity advocates enhanced antepartum monitoring and detailed delivery planning with multidisciplinary involvement. As such, it is essential that all anaesthetists working on delivery units are able to anticipate and manage the challenges associated with these high-risk patients.

Table 1.

Maternal and neonatal complications associated with obesity.

Maternal complications	Neonatal complications
Gestational diabetes	Preterm delivery
Gestational hypertension and pre-eclampsia	Miscarriage
Obstructive sleep apnoea	Small for gestational age
Cardiovascular disease	Large for gestational age
Thromboembolism	Macrosomia
Infection and sepsis	Stillbirth
Instrumental delivery	Shoulder dystocia
Failed instrumental delivery	Neural tube defects
Caesarean delivery	Neonatal death
Postpartum haemorrhage	Neonatal ICU admission
Longer hospital stay

Definition and classification

Obesity is defined as an excessive or abnormal fat accumulation posing significant health risk. The WHO uses BMI to classify degree of obesity. A BMI between 18.9 and 24.9 kg m⁻² is normal, BMI 25–29.99 kg m⁻² is overweight and BMI >30 kg m⁻² is obese. Obesity is further subclassified as Class 1 (BMI 30–34.9 kg m⁻²), Class 2 (BMI 35–39.9 kg m⁻²) and Class 3 (BMI >40 kg m⁻²). Further definitions for Class 3 obesity include morbid obesity (BMI 40–49.9 kg m⁻²), super obesity (BMI 50–59.9 kg m⁻²) and super-super obesity (BMI >60 kg m⁻²). There is a lack of consensus on optimal weight gain during pregnancy, and current guidance suggests focusing on a healthy diet may be more applicable than targeted weight gains.¹

Considerations for anaesthesia

Preoperative assessment

The anatomical and physiological changes of pregnancy coupled with those of obesity make these parturients a particularly high-risk population. As such, the Royal College of Obstetricians and Gynaecologists recommends that women with BMI >40 kg m⁻² should have a formal consultation with an anaesthetist in the third trimester of pregnancy.¹ Ideally, the consultation should be conducted early in the third trimester to allow time for further investigations and optimisation before delivery, if needed. A senior anaesthetist should conduct the preoperative assessment, and the anaesthesia plan for delivery should be clearly documented in the patient's notes. Table 2 shows the preoperative considerations for the anaesthetist in parturients who are obese.

Table 2.

Preoperative considerations for parturients with obesity.

System	Specific considerations
Airway
Increased risk of difficult intubation in the parturient with obesity	•Detailed examination, including Mallampati score, thyromental distance, mouth opening and jaw protrusion
Respiratory
Increased risk of OSA	•Detailed history exploring features of OSA or its sequelae •Referral for sleep studies and opinion from pulmonologist if deemed appropriate
Cardiovascular
Increased risk of cardiovascular disease (hypertension, ischaemic heart disease and cardiomyopathy)	•Focused cardiac history: chest pain, palpitations, reduced exercise tolerance, orthopnoea and paroxysmal nocturnal dyspnoea •Focused examination: pedal oedema, bibasal crackles and raised jugular venous pressure •Low threshold for ECG, echocardiogram and cardiology referral for optimisation
Gastrointestinal
Increased risk of aspiration associated with hiatus hernia and reflux disease	•Appropriate starvation times before elective surgery; consider clear fluids only in labour •Premedication with H2 antagonist and antacid •Consider premedication with metoclopramide for prokinesis
Metabolic
Increased risk of pre-existing insulin resistance and gestational diabetes	•History of microvascular and macrovascular complications of insulin resistance •Referral to endocrinologist for optimisation

The consultation should include a standard history with specific attention to screening for potential comorbidities associated with obesity, such as obstructive sleep apnoea (OSA), hypertension, cardiac disease, gastro-oesophageal reflux and diabetes. A detailed physical examination of the airway, respiratory and cardiovascular systems should also be conducted. Some clinical features of cardiorespiratory disease, such as dyspnoea and pedal oedema, may be difficult to distinguish from changes associated with pregnancy, and there should always be low threshold for ordering an ECG and transthoracic echocardiogram. The spine should also be examined to identify patients in whom neuraxial placement could be challenging, and it may be beneficial to use ultrasound (US) before any neuraxial procedures.

The consultation also provides an opportunity for patient education and counselling. Patients should be informed of their risk for dysfunctional labour and higher Caesarean delivery (CD) rate. As a consequence, they should be advised to have an epidural catheter sited early in labour for two main reasons. Firstly, epidural catheter placement is likely to be challenging, requiring multiple attempts, and may be more successful when the patient is calm and compliant with positioning before strong contraction pain commences. Secondly, patients with obesity are at higher risk of epidural catheter failure compared with women of normal BMI.⁶ Early placement allows time to ensure that the catheter is working adequately should assisted or operative delivery be needed, and therefore reduces the risk of needing GA in a parturient with a potentially difficult airway. Patients should also be educated about the potential need to use US to assist with i.v. and epidural catheter placement, and possible need for arterial line placement for arterial blood pressure monitoring. The anaesthetic consultation should not only highlight to the patient that she is high risk, but also provide reassurance that the modifications in her anaesthetic care are being taken to maximise safety for her and her baby.

Logistical planning

Women with obesity should only have their baby delivered in obstetric units that have services adequate to meet their potentially complex care needs. All maternity units should regularly assess their capabilities for managing women with BMI >30 kg m⁻², including staffing, equipment and accessibility. In the UK, women with BMI >35 kg m⁻² should be delivered in a consultant-led unit with appropriate anaesthesia and neonatal services.¹ It is important that delivery units have adequate staffing with advanced clinical training to manage these patients throughout the peripartum period. Caregivers should attend manual handling courses and use transfer equipment (patient lifts and hover air mattress) wherever possible to minimise risk to patients and staff.

Specialised anaesthetic equipment should be readily available, such as difficult airway equipment, US machines, long spinal and epidural needles, appropriately sized non-invasive blood pressure (NIBP) cuffs and invasive arterial monitoring. Invasive arterial monitoring should be directed by the patient's comorbidities and possible problems affecting the accuracy and reliability of NIBP measurements. Poor fitting of NIBP cuffs in women who are obese occurs because of problems with size and the conical shape of the upper arm, which can cause overestimation of the blood pressure and discomfort for the patient. An NIBP cuff on the forearm may be used if it is not possible to use an appropriately sized blood pressure cuff on the upper arm.⁷ This method of NIBP measurement will provide consistent blood pressures that are correlated with upper arm pressures, albeit slightly higher. Venous access might be challenging, necessitating US-guided peripheral i.v. catheter placement. Central venous access may also need to be established if peripheral access is difficult or other comorbidities are present. Long spinal and epidural needles should also be available. Institutions managing patients who are obese for delivery should have operating tables, labour beds and wheelchairs with higher weight-bearing capacities. Similarly, appropriately sized gowns, pneumatic compression devices and stockings should be routinely available.

Even with appropriate equipment, transporting women with BMI >50 kg m⁻² to the operating theatre in the event of an emergency can be challenging. Continuous communication with the obstetric team is needed to identify women likely to need operative delivery early, so patients can be moved in a timely manner. Special consideration may also be given to labouring those patients in an operating theatre, if feasible, as a means to reduce decision-to-delivery times.

Peripartum anaesthetic management: analgesia for labour

Neuraxial analgesia

Neuraxial techniques are the ideal option for labour analgesia in parturients with obesity. They provide the most effective analgesia with the fewest adverse effects for both mother and baby. Furthermore, with neuraxial techniques, labour analgesia can be readily converted to surgical anaesthesia should the need for CD arise, therefore avoiding the need for GA with its associated risks in patients who are obese. Epidural catheter placement or modification of the technique (combined spinal–epidural [CSE] and dural puncture epidural [DPE]) remains the most common mode for delivering neuraxial analgesia in obese parturients. However, intrathecal catheters (ITCs) can be considered in certain situations.

Placement of epidural catheters can be notoriously challenging in these patients because of the increased amount of subcutaneous tissue that makes anatomical landmarks difficult to palpate. The sitting, flexed position is preferred, as it allows better appreciation of the midline and reduces the distance from the skin to the epidural space compared with the lateral position.⁸ Using US before the procedure can also help localise the midline and provide estimation of the depth to the epidural space. In addition, it has also been shown to reduce the number of attempts and number of needle redirections for successful epidural catheter placement. It is therefore important that anaesthetists managing labour units are adequately trained and skilled at using US for labour epidural catheter placement. In extreme circumstances, a standard-length epidural needle may not be sufficient, and a longer needle will be required to identify the epidural space. Nonetheless, it is advisable to use a standard-length epidural needle for the first attempt, as longer needles might be more challenging to control with the potential for causing complications. Continuous communication with the patient during epidural catheter placement is vital: it educates the patient about optimal positioning and alleviates her anxiety. In addition, feedback from the patient can help the anaesthetist redirect the needle towards the midline if encountering difficulties. Once the epidural catheter has been placed, it is important that it is secured appropriately to reduce migration and dislodgement. The patient should be asked to move from the sitting flexed position to the sitting upright position before securing the catheter with tape. Changing position from flexed to sitting causes redistribution of subcutaneous tissue, and the catheter frequently appears to be drawn inwards. Securing the catheter to the skin before position change may risk leaving an inadequate depth or having the catheter pulled out of the epidural space.⁹

The technical difficulty of epidural catheter placement in patients with obesity is associated with increased risk of accidental dural puncture (ADP) compared with patients of normal BMI (4% vs 1%).¹⁰ However, the impact of BMI on developing postdural puncture headache (PDPH) in the event of ADP is conflicting. Whilst some studies have shown that the risk of developing PDPH is reduced in parturients with high BMI, other studies have not confirmed this finding. Overall, the evidence suggests that high BMI may offer some protection against developing PDPH, with the effect probably being most noticeable in parturients with BMI >50 kg m⁻².¹¹ Furthermore, even though the risk of developing PDPH may be reduced in women who are obese, the incidence of developing PDPH still remains considerable with rates of at least 40–45% being reported.¹² In addition, whilst pushing during the second stage of labour increases the risk of PDPH and women with obesity might be less likely to push given the high CD rate, data suggest that high BMI may reduce the risk of PDPH even after controlling for pushing.^10,11

There are no studies specifically comparing traditional epidural to CSE technique for labour analgesia in parturients who are obese. A labour CSE technique provides fast, reliable analgesia without sacral sparing. In addition, when epidural catheters are placed as part of a CSE technique, they have lower failure rates compared with traditional epidural techniques.^13,14 This has been attributed to the confirmation of CSF return when using a needle through a needle technique that provides some reassurance that the epidural space has been located and that the epidural catheter is likely to be midline. Similarly, a DPE technique can be used. In the DPE technique, the epidural space is identified, the dura is punctured without giving intrathecal medications and an epidural catheter is threaded in the routine manner. When compared with traditional epidural technique for labour analgesia, DPE may be associated with better sacral spread and less unilateral or patchy block.¹⁵ It is presumed that the dural hole acts as a conduit, allowing delivery of small amounts of local anaesthetic into the intrathecal space from the epidural space. Furthermore, similar to the CSE technique, return of CSF with dural puncture helps to confirm correct and midline placement, therefore increasing the chances for a successful block. Although the DPE technique has not been specifically investigated in patients with obesity, it would seem logical that the perceived benefits of the technique may prove advantageous.

Once an epidural catheter has been sited, delivery of local anaesthetic mixtures through the epidural catheter can be achieved with continuous epidural infusion, patient-controlled epidural analgesia or programed intermittent epidural bolus. These maintenance strategies have not been compared in parturients with obesity, and local anaesthetic delivery should be commenced as per departmental protocols.

An ITC can also be placed to provide continuous labour analgesia. Whilst placement of an ITC is usually only considered after inadvertent ADP, elective placement in women with BMI >50 kg m⁻² may be an option for neuraxial analgesia, especially in those patients with clinical features suggesting potential difficult airway management. Intrathecal catheters allow safe, reliable delivery of labour analgesia and can be carefully extended to provide surgical anaesthesia should CD be needed, thereby reducing the particular risks of GA in the labouring patient with obesity. However, managing ITCs requires specific training, and communication with all members of the labour and delivery team is vital to avoid potential drug errors. Ideally, departments should have protocols in place to safely manage an ITC. Furthermore, it is important to note that there is at least a 40–50% risk of PDPH associated with their use.

Irrespective of the neuraxial technique chosen, patients should be routinely reassessed to allow for early detection of poorly functioning catheters and timely replacement if needed. A well-functioning neuraxial catheter for labour analgesia ultimately mitigates the risk for GA should CD be needed, and also improves patient satisfaction.

Non-neuraxial options

In the event that neuraxial analgesia is contraindicated or not possible, non-neuraxial options for analgesia should be offered. Inhaled nitrous oxide and oxygen mixtures are routinely available in the UK and can provide some analgesia, albeit inferior to neuraxial options, without adverse effects on mother and baby. Opioids should be judiciously used in parturients with obesity because the incidence of OSA and the risk of respiratory depression are both increased. Alternative therapies, such as acupuncture and transcutaneous electrical nerve stimulation, could also be considered, although the effectiveness of these therapies is unproved in general and has not been specifically investigated in managing patients who are obese.

Peripartum anaesthetic management: CD

Irrespective of whether neuraxial anaesthesia or GA has been chosen as the primary anaesthetic, all patients with obesity should be placed in the ‘ramped position’ with left uterine displacement. This position can be achieved by using commercially available devices, such as a Troop Elevation Pillow, (Mercury Medical, Clearwater, FL, USA) or by placing blankets under the upper body and shoulders so the head is above the chest. This position will improve respiratory mechanics, but more importantly, it has been shown to improve the laryngeal view compared with the traditional 'sniffing' position should intubation be needed. Special attention should also be given to ensuring pressure points are protected, as the risk of perioperative nerve injuries is higher in patients with obesity.

Retraction of the panniculus may be needed for adequate exposure for surgery especially when Pfannenstiel incision is used. Many obstetricians choose to tape the panniculus in the cephalad direction. However, commercially available self-retaining retractors, such as the traxi Panniculus Retractor (Clinical Innovations, Salt Lake City, Utah, USA), can also be used. Cephalad retraction is associated with aortocaval compression that can lead to maternal hypotension and non-reassuring fetal heart tones.¹⁶ Anecdotally, it also causes some difficulty in breathing and may increase the cephalad spread of spinal block. Therefore, vigilant monitoring whilst the retraction is being instituted is needed. As an alternative, vertical angled suspension of the panniculus has also been suggested to reduce the risks of hypotension and respiratory compromise associated with cephalad retraction.

Obesity is a risk factor for surgical site infection after CD. Whilst some institutions give cefazolin 3 g to obstetric patients weighing >120 kg (rather than the standard dose of 2 g), the benefit of this increased dose is unclear and evidence is conflicting.¹⁷ Re-dosing cefazolin at 2 h and giving cephalexin and metronidazole for 48 h postpartum have been suggested to maintain appropriate tissue concentrations and reduce surgical site infection.^18,19 However, further studies validating this practice are needed before routine use can be recommended.

Neuraxial anaesthesia

Neuraxial anaesthesia is always preferred in patients with obesity presenting for CD unless contraindicated. Choice of neuraxial anaesthetic technique will depend on urgency of case, airway examination and surgical plan.

Single-shot spinal anaesthesia can deliver fast onset, reliable anaesthesia and may be a viable option in patients with reassuring airway examination and without cardiopulmonary compromise. However, the finite duration of the spinal block limits its use in parturients with morbid obesity, when extra time for patient positioning and extra time from incision to delivery are expected. If the spinal block begins to regress before surgery has ended, GA with all its inherent risks may be required. Original concerns of using a standard intrathecal hyperbaric bupivacaine dose in parturients with obesity and the potential risk of high spinal block have not been supported by clinical trials.²⁰ Dose reductions are therefore not recommended and may increase the risk of inadequate block and intraoperative pain.²¹ However, patients with BMI >50 kg m⁻² are likely to need lower intrathecal doses of bupivacaine for CD compared with women with lower BMI.²² Giving a standard intrathecal dose in parturients with >50 kg m⁻² may result in high spinal block, and therefore, single-shot spinal anaesthesia should only be used after careful consideration in these patients. Furthermore, single-shot spinal anaesthesia with a 25G pencil-point needle can be technically challenging in women with excessive truncal adiposity, especially when longer spinal needles are needed. Advancing a Tuohy needle may be technically easier, and once the epidural space has been located, it can be used as an introducer for the long spinal needle as part of a needle-through-needle CSE technique.

More commonly, catheter-based techniques are chosen to deliver extended neuraxial anaesthesia for CD. If a patient has a labour epidural catheter in situ, this can be easily used to provide surgical anaesthesia. However, in the event new neuraxial anaesthesia needs to be established, epidural anaesthesia de novo carries a risk of patchy block and sacral sparing. It may be more prudent to use a CSE technique that combines the dense block of spinal anaesthesia with the flexibility to extend duration of the block with the epidural catheter if needed. Another advantage of the CSE technique is that it can be modified where a small dose of intrathecal bupivacaine can be administered and the block gradually extended to achieve adequate surgical anaesthesia. This may be particularly useful in women with super obesity, where intrathecal local anaesthetic dose should be reduced, or in parturients with cardiovascular disease, where a slowly titrated anaesthetic causes minimal haemodynamic instability. Similarly, continuous spinal anaesthesia using an ITC can be used to deliver a slow titrated anaesthetic. However, establishing an ITC may prove most beneficial for emergency CD in a patient with obesity with concerning airway features who does not have an epidural catheter in situ. Ultimately, the risk of PDPH must be weighed against the benefit of avoiding airway intervention on an individualised basis.

With the increasing rates and severity of obesity, surgical techniques may need to be modified for adequate exposure and access whilst reducing postoperative infection rates. Traditional Pfannenstiel incisions may not be suitable and supraumbilical midline incisions may be needed. In these cases, it might be challenging to provide adequate anaesthesia for the upper end of the incision with a lumbar neuraxial technique alone. Furthermore, the vertical supra-umbilical incision might cause postoperative diaphragmatic splinting and increase the risk of respiratory complications. Therefore, a double catheter technique combining a lumbar spinal catheter or CSE technique with a thoracic epidural catheter can be used in those cases.²³ The lumbar technique is used primarily for intraoperative anaesthesia, whilst the thoracic catheter is placed for postoperative analgesia and to provide additional intraoperative anaesthesia for the upper end of the incision if needed.

General anaesthesia

There are significant risks associated with GA for parturients who are obese. The importance of patient positioning, preoxygenation, presence of adequate personnel and difficult airway equipment cannot be emphasised enough.

Optimal patient positioning should not only address concerns surrounding difficult intubation, but should also aim to improve respiratory mechanics for preoxygenation. The reduction in functional residual capacity (FRC) associated with pregnancy is worsened by obesity, and when coupled with increased oxygen consumption, parturients with obesity will desaturate rapidly on induction of GA. It is therefore vital that adequate preoxygenation is performed until Peʹo₂ is >90%. Patients should be in the ramped position, as this will improve the FRC and increase the safe apnoea time (time from induction to critical desaturation; Spo₂ 88–90%), in addition to improving view at laryngoscopy. The head-up position can also be considered, as it may reduce gastro-oesophageal reflux and challenges with inserting the laryngoscope blade in women with large breasts, increase FRC and safe apnoea time and improve laryngoscopic view.²⁴

Using either continuous positive airway pressure (CPAP) or pressure support ventilation has been shown to enhance preoxygenation in non-pregnant patients with obesity, and prevent desaturation during rapid sequence induction.²⁵ Apnoeic oxygenation is a well-established technique in non-obstetric patients that prolongs apnoea time during laryngoscopy and can be easily achieved using nasal prongs delivering oxygen 5–15 L min⁻¹. The Obstetric Anaesthetists' Association (OAA) and Difficult Airway Society (DAS) guidelines mention the potential role of apnoeic oxygenation based on research from the non-obstetric population, and its use should be considered when preoxygenating parturients with obesity. More recently, there is emerging interest in using high-flow humidified nasal oxygen (HFNO), also known as transnasal humidified rapid insufflation ventilatory exchange (THRIVE), for preoxygenation and apnoeic oxygenation, which can deliver humidified oxygen up to 70 L min⁻¹. Although this technique has shown promising results to improve preoxygenation and safe apnoea time in non-obstetric patients who are obese, the role of HFNO in obstetrics is less clear and warrants further investigation.

Giving a general anaesthetic to a parturient with obesity poses multiple airway challenges, including difficult face-mask ventilation and an increased risk of failed intubation. Consequently, there should be at least two anaesthetists, one of whom is considered a senior provider. All anaesthesia providers should be familiar with the OAA and DAS guidelines, and the difficult airway equipment should be readily available in the event of a failed intubation.²⁴ Use of videolaryngoscopy as the first-line technique for intubation should be strongly considered. However, alternative methods, such as a short-handled Macintosh blade, should also be readily available.

There should be careful attention to the dosing of induction agents to ensure adequate depth of anaesthesia. The fifth National Audit in the UK identified obstetric surgery and obesity as independent risk factors for accidental awareness under GA (AAGA).²⁶ Most incidents of AAGA occurred during induction of anaesthesia with the use of neuromuscular block. Unfortunately, there is limited information on the pharmacokinetic profile of commonly used i.v. anaesthetic agents in the parturient with obesity. However, it is advised that lean body weight should be used to calculate initial doses of i.v. induction agents rather than total body weight.²⁷ By contrast, suxamethonium should be dosed to total body weight because of increased circulating plasma cholinesterase. If non-depolarising neuromuscular blocking drugs are being used on induction of anaesthesia, these should be given based on ideal body weight.²⁸

Emergence from anaesthesia is also a critical time, and the anaesthesia provider must be vigilant, as the risk of aspiration exists during this time as well. To minimise risk, the stomach should be decompressed with an orogastric tube and the patient should be awake, obeying commands and able to protect her airway before tracheal extubation. Extubation should be carried out with the patient in the head-up position to allow control of the airway and improve respiratory mechanics. If the parturient has OSA, it is advised to commence CPAP immediately to avoid airway obstruction and hypoxia. There is also increased risk for airway obstruction and hypoventilation on emergence and during the early postoperative period, so special vigilance is required. The patient should be transported out of the operating theatre in the head elevated (semi-recumbent) position, and should also be maintained in this position during the immediate recovery period.

Postpartum considerations

Obesity increases the risks for postpartum complications, including infection (endometritis, wound, urinary and respiratory), venous thromboembolism (VTE), respiratory depression and cardiovascular complications. Postpartum management should therefore focus on minimising the risk of developing these complications. The location of where the parturient with obesity is best managed after surgical delivery should be individualised; it should account for the presence of other comorbidities, peripartum complications and need for invasive monitoring or respiratory support. Parturients with obesity who are otherwise healthy with an uncomplicated delivery can be safely managed on a postpartum ward. Patients identified as requiring a higher level of postoperative monitoring and treatment may require admission to maternal high-dependency unit or ICU.

Optimal post-delivery analgesia is paramount in the parturients who are obese, as it will improve respiratory mechanics and mobilisation, whilst reducing risk of VTE. The cornerstone for managing pain after CD is using multimodal analgesia inclusive of a long-acting neuraxial opioid, which is considered the gold standard. Neuraxial morphine and diamorphine are most commonly used, but respiratory depression is a concerning adverse effect associated with their use, especially for parturients with obesity. However, current evidence suggests that the incidence of respiratory depression after neuraxial morphine use is low, even in the presence of morbid obesity.²⁹ The administration of neuraxial long-acting opioids for pain after CD in parturients who are obese is therefore recommended, using contemporary low doses with appropriate monitoring for respiratory depression. Although the UK has not published any guidelines on respiratory monitoring after administration of long-acting neuraxial opioids for CD analgesia, the Society for Obstetric Anesthesia and Perinatology (USA) recently published a consensus statement providing guidance for respiratory monitoring after neuraxial morphine use based on individual stratified risk.³⁰ Morbid obesity and OSA are risk factors for developing respiratory depression, and consequently, higher levels of respiratory monitoring for 24 h after administration are advised. When neuraxial opioid is omitted from the analgesic regimen because neuraxial anaesthesia is contraindicated or urgency of CD necessitates GA, managing CD pain in parturients with obesity could be challenging. In these cases, i.v. opioid patient-controlled analgesia may be used cautiously in a clinical area with provision for higher levels of monitoring for sedation and respiratory depression. Furthermore, using local anaesthetic techniques, such as transversus abdominis plane (TAP) or quadratus lumborum (QL) block, or wound infiltration should be considered routinely in patients who have not received long-acting neuraxial opioid, as they have been shown to reduce systemic opioid consumption in the postoperative period.³¹ However, it must be noted that in parturients with morbid obesity, TAP or QL block may be technically challenging, even with US guidance. Alternatively, if a double catheter technique had been used during CD, the thoracic epidural catheter could be used for postoperative analgesia.

Maternal obesity increases the risk of developing VTE in the antepartum and postpartum periods. Appropriately sized pneumatic compression devices and stockings should be used throughout the peripartum period. Patients should be encouraged to mobilise early and pharmacological thromboprophylaxis should be commenced. There is variation between international guidelines for thromboprophylaxis, and therefore any drug therapy must be prescribed in accordance to local protocols.

Conclusions

Maternal obesity is growing at an alarming rate worldwide and is associated with adverse outcomes in both mother and baby. Multidisciplinary team involvement is vital for successful management, and as such, anaesthetists working on labour suites must be familiar with the complexities of managing these patients throughout the antepartum and peripartum periods. Apart from the clinical challenges associated with managing these patients, there are significant logistical challenges. Careful planning will improve maternal and neonatal safety.

Declaration of interests

ASH is an editor and editorial board member of BJA Education. SDP declares that they have no conflict of interest.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Biographies

Selina Patel is an assistant professor of anesthesiology at the University of Miami Miller School of Medicine. Her clinical and research interests focus on obstetric anaesthesia.

Ashraf Habib is a professor of anesthesiology, obstetrics and gynaecology, and chief of the Division of Women's Anesthesia at Duke University Medical Center. His major clinical and research interests are obstetric anaesthesia, acute pain and enhanced recovery after surgery.

Matrix codes: 1A02, 2B04, 3B00