Anaesthesia for caesarean section in a morbidly obese parturient with history of lignocaine allergy: A case report

Abstract

Morbidly obese obstetric patients present multiple challenges to the anaesthetist for labour analgesia and anaesthesia for caesarean section. The superiority of regional anaesthesia (RA) using local anaesthetics (LA) to all other techniques in the obese parturient, as well as avoiding complications of general anaesthesia (GA) in a caesarean delivery makes LA allergy in parturients an important issue. We report the first known case of lignocaine allergy in a morbidly obese parturient.

Introduction

True allergic reactions to LA are rare, with an incidence of <1%.^1–5 They can occur resulting from sensitivity to either the ester or amide component; other causative agents in LA reactions include methylparaben used as a preservative in multiple dose vials, or antioxidants used in some formulations. Most allergic reactions associated with LA are associated with para-amino benzoic acid, a metabolite of ester LA.^1,4 Obese patients have increased risk of abnormal labour; increased rates of instrumental delivery and caesarean sections. ⁶ Obesity is also a risk factor for anaesthesia-related maternal mortality, and thus, morbidly obese women are considered high-risk.^6,7 In the obstetric morbidly obese population, to simply avoid using LA would not be as straightforward. RA techniques for labour analgesia and caesarean sections have notable advantages.^7,8 We report the challenges in a morbidly obese parturient who has concurrent lignocaine allergy and her anaesthetic management.

Case report

A primiparous 29 year old female weighing 116 kg with a body mass index (BMI) of 52, was admitted to hospital for induction of labour at term. She had a previous hypersensitivity to non-steroidal anti-inflammatory drugs (NSAIDs) with angioedema, and a definite lignocaine allergy. With regards to the latter, she developed facial angioedema and intraoperative bronchospasm while undergoing GA for tonsillectomy in 2018. She was subsequently assessed by an allergist and had a positive drug provocation test to subcutaneous lignocaine 1%, where she developed chest tightness, breathlessness and pruritus, progressing to flushing over her face and widespread urticaria. She has a past medical history of well controlled asthma, morbid obesity and panic disorder. A previous sleep study was negative for obstructive sleep apnoea.

In the labour ward, she received patient controlled analgesia (PCA) remifentanil for her labour analgesia. She was monitored with 1:1 nursing, placed on supplemental oxygen and had vital signs (including sedation score) monitored closely. Her labour pains were well controlled with PCA remifentanil, with no side effects such as respiratory depression or sedation. 12 hours after the PCA remifentanil was started, she needed an emergency caesarean section due to failure to progress and non-reassuring fetal status (NRFS) seen on her cardiotocography.

The patient was premedicated with sodium citrate and ranitidine prior to transfer to the operating room. An informed consent for GA was obtained. She was prepped in operating room by lying in a semi-supine position, using the Troop Elevation Pillow. Preoxygenation was challenging as she was anxious and uncooperative. Nevertheless, end tidal oxygen (ETO2) 90% was obtained prior to induction with propofol (200 mg) and rocuronium (60 mg) with cricoid pressure applied. On the first attempt, a C-MAC D-blade video laryngoscope was used. However, the blade could not be advanced further due to bulky surrounding tissue. The procedure was abandoned. She was preoxygenated again by face-mask ventilation with oral airway and two-person technique. On second attempt, a McGrath with MAC 3 blade was used. The vocal cords were visualized when external laryngeal pressure was applied. A bougie was advanced to facilitate endotracheal intubation. The anaesthesia was maintained using sevoflurane in 50:50 oxygen and nitrous oxide. Upon delivery, baby’s apgar scored 9 and 9 at 1 and 5 min respectively. Intraoperative medications included intravenous morphine, paracetamol, dexamethasone and ondansetron. She was reversed with sugammadex (200 mg) and extubated awake. Postoperatively, she was transferred to the high dependency unit for respiratory monitoring and started on PCA morphine for pain control.

Discussion

Management of a parturient with lignocaine allergy poses many challenges for the anaesthetist as there is a profound dependence on LA for the management of anaesthesia and analgesia for labour and delivery.^1,3 Our patient with a BMI of 52, had a definite lignocaine allergy. She received PCA remifentanil for her labour analgesia with subsequent GA for her emergency caesarean section.

Cross-reactivity between and within LA

LA comprise of a lipophilic aromatic ring connected by an intermediate chain to a hydrophilic amine group, and are classified as either ester or amide compounds based on the intermediate chain. Esters LA are associated with a higher incidence of allergic reactions due to a p-aminobenzoic acid metabolite, which do not occur with amide LA such as bupivacaine and ropivacaine.^2,5 Our case had reported allergy to lignocaine, an amide LA, which is very rare.

Majority of the LA used in central neuraxial blockade are amides. Chloroprocaine, which is an ester LA, is an alternative used in the obstetric setting, where it is to provide fast onset neuraxial anaesthesia. ⁹ It is generally considered as a safe drug to use during pregnancy as it is rapidly metabolised by pseudocholinesterase, eliminating the concern for systemic toxicity and fetal exposure. However, it is not widely practised due to several disadvantages such as no standardised dosing, prolonged neural blockade and increased LA toxicity risk in patients with plasma cholinesterase deficiency.^1,8 Inadvertent subarachnoid space injection with epidural dose may cause cauda equina syndrome and adhesive arachnoiditis.^1,8 Previously, the concern of neurotoxicity from its preservatives had limited its use in spinal anaesthesia. The United States Food and Drug Administration only recently approved the use of a preservative-free chloroprocaine to provide short duration spinal anaesthesia. ¹⁰ The product is currently not available in Singapore.

Cross-reactivity between the amide and ester groups exists, though rarely reported. ¹¹ This cross-reactivity may be attributed to paraben allergy in preservative containing amide preparations or co-sensitisation. ¹¹ Despite this, the use of ester chloroprocaine in epidural analgesia or anaesthesia for parturients with amide lignocaine allergy has been documented in case reports or small case series since 1980.^1,8 There have also been isolated reports of cross-reactivity within the amide group.^2,8,11 It is therefore important to consider the possibility of cross-reactivity between different agents. ¹¹

Testing prior to next pregnancy

This cross-reactivity between different LA agents highlights the necessity for patients to undergo allergy testing prior to administration of other ester or amide LA.^5,11 Pregnancy is a relative contraindication to performing skin prick tests due to the possibility of inducing a systemic allergic reaction that could induce uterine contractions, or necessitate the use of epinephrine in emergency treatment which is thought to cause constriction of the umbilical artery. ¹² Ideally, women with a suspected allergy to LA should be referred to an allergist pre-pregnancy to test for suitable alternatives. ⁶ Our patient was not tested for other LA allergies. Apart from being able to be utilised for caesarean section through epidural top-ups, there are many other advantages of a labour epidural, using the LA that is tested safe for her. The advantages obese patients would benefit from a RA technique for labour and delivery include providing superior pain relief, the ability to convert the epidural analgesia to surgical anaesthesia and lowered adverse effects from alternatives; these are outlined below.^1,7,8,13

Considerations in anaesthesia for the obese parturient

Increased pre-pregnancy weight is associated with an increased incidence of fetal macrosomia and labour abnormalities such as shoulder dystocia, which are risk factors for more painful contractions and complicated labour. ⁶ Obesity also increases the need for caesarean section, as in the case of our patient. ¹³ Placement of a well-functioning epidural catheter is one of the safest methods of providing labour analgesia. In addition to providing superior pain relief, labour epidural analgesia can be converted to surgical anaesthesia if the need for caesarean delivery arises.^1,6–8,13 The next best alternative, PCA remifentanil, does not provide as good pain relief and has a higher rate of adverse effects such as sedation, respiratory depression.^7,8 These are more relevant in an obese patient who is at increased risk of drowsiness leading to airway obstruction.^6,7 As seen in our case, close monitoring was required by nursing staff upon commencement of PCA remifentanil to look out for adverse effects.

Obese parturients are at an increased risk for difficult airway, aspiration, deep vein thrombosis and perioperative cardiovascular and respiratory complications. ⁸ Central neuraxial anaesthesia is preferred for caesarean deliveries as it avoids airway manipulation, minimises aspiration risk, prevents fetal exposure to volatile anaesthetics and decreases the risk of post-partum haemorrhage.^7,8,13 The case reported had to undergo GA due to avoidance of all LA, which may result in anaphylaxis, threatening the lives of both mother and fetus. ⁴ Our patient had a challenging preoxygenation phase, face mask ventilation and intubation. Current guidelines advocate greater utilisation of methods to improve the view at laryngoscopy. ¹⁴ A video-larygoscope should be readily available with strong consideration to use on all obese parturients as routine.^13,14 A ramp position is also important to obtain the optimal laryngoscopic view either by using a folded blanket under the upper body or by using a commercial device, such as Troop Elevation Pillow, which is designed specifically to facilitate airway management for obese patients. ¹⁵ The Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE), which provides pre-oxygenation and maintains oxygenation without ventilation, should also be considered in order to prolong the time to desaturation. ¹³ Other modifications included the use of rocuronium and sugammadex in anticipation of failed airway management and rapid reversal.

Conclusion

We report a case on morbidly obese parturient with known lignocaine anaphylaxis. Early referral to the anaesthetist is recommended for counselling regarding labour analgesia and possible anaesthesia options. ³ Allergy testing ideally should be done pre-pregnancy for other amides and esters LA so they can be administered when the patient comes to hospital for delivery.^3–5