|Year : 2018 | Volume
| Issue : 9 | Page : 704-709
Anaesthetic management of obstetric emergencies
Pradeep A Dongare, Madagondapalli S Nataraj
Department of Anaesthesia, ESICMC-PGIMSR, Bengaluru, Karnataka, India
|Date of Web Publication||10-Sep-2018|
Dr. Pradeep A Dongare
Department of Anaesthesia, ESICMC-PGIMSR, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
Obstetric emergencies are a challenge both for the obstetrician and the anaesthesiologist. The incidence of caesarean sections as per the National Family Health Survey published in 2015–16 was 17.2%. In 7.6% of cases, the decision to conduct a caesarean section was taken after the onset of labour pains. Caesarean sections are classified depending on the urgency into four categories. The target decision to delivery interval for category 1 caesarean section is less than 30 min. This is used as an audit tool for the efficiency of an obstetric service. The management of these emergencies involves a rapid assessment, with minimal investigations. Although general anaesthesia is considered to have higher morbidity and mortality, category 1 caesarean sections may still warrant this technique. Rapid sequence spinal anaesthesia is replacing general anaesthesia for many of the category 1 indications. In category 2 and 3 caesarean sections, spinal anaesthesia still remains the technique of choice. Failed intubation, failed neuraxial block, extensive neuraxial block, awareness under anaesthesia, thromboembolism, amniotic fluid embolism, haemorrhage and maternal collapse are some of the complications. Haemorrhage is said to be the leading cause of mortality worldwide.
Keywords: Anaesthesia, caesarean, emergencies, obstetric
|How to cite this article:|
Dongare PA, Nataraj MS. Anaesthetic management of obstetric emergencies. Indian J Anaesth 2018;62:704-9
| Introduction|| |
The incidence of caesarean deliveries in India as per the National Family Health Survey report was 17.2%. Of all deliveries, in 7.6% of cases, the decision to conduct caesarean section was taken after the onset of labour pains. This gives us an indirect indicator of caesarean sections performed for emergent indications. Emergency anaesthesia has high maternal and child morbidity and mortality. Improving anaesthetic care is one of the key areas of action in the MBRRACE – UK Maternal report 2017. Formerly, caesarean deliveries were categorised as elective and emergency. The problem with this classification was that all non elective cases were categorised as emergencies irrespective of their nature of urgency. Rout et al. in the year 1997 described the indications for emergency caesarean section depending on the available time to delivery [Table 1] and classified them as emergencies, urgent and planned emergencies. From this classification a rational decision on the technique of anaesthesia to be employed was described [Table 2]. A classification of the urgency of caesarean delivery was developed by Lucas in 2000. It was based on a four scale category of urgency [Table 3]. This new classification was introduced in the 2004 edition of National Institute for Health and Care Excellence (NICE) guidelines. The NICE, established in 1999, is part of the National Health Service that aims at improving the quality and safety of medical care through standardisation of medical treatment by providing guidelines from scientific evidence and economic evaluation. We used the search words obstetric emergencies, decision to delivery interval (DDI), category 1 caesarean section, anaesthetic complications of caesarean section, amniotic fluid embolism in PUBMED, Google Scholar and EMBASE databases to access articles pertaining to this topic.
| Decision-To-Delivery Interval for Caesarean Section|| |
The earliest guidelines for DDI in caesarean section were put forth by ‘Organizational Standards for Maternity Service’ published by the Royal College of Obstetricians and Gynaecologists in 1995. It stated that the decision-to-delivery interval for category 1 caesarean section should be less than 30 min. Although this rule has not been validated, it is generally accepted that the neonates should be delivered within 30 min following the decision to deliver to have a better outcome. This timeline of 30 min is used as an audit tool rather than an objective guide. Of these 30 min, 5 min are for transporting the patient to the theatre, 5 min for draping and painting and the rest of the time for anaesthesia and delivery. The available time for anaesthesia determines the technique of anaesthesia used [Table 2].
A DDI of 30–75 min is described for category 2 caesarean sections by some authors.
The factors that can affect DDI can be divided according to the competence and responsibility of people involved in the functioning of the obstetrics department. Obstetrician-dependant factors include appropriate diagnosis of indications for caesarean section and proficiency during the procedure (incision-to-delivery interval). Midwives are responsible for preparation of the patient and the operating theatre as well as transport of the patient. Anaesthesiologists deem patients eligible for anaesthesia and are also responsible for efficiency of its administration. Furthermore, few additional factors namely sufficient number of qualified staff, regular training in emergency procedures, availability of operating theatres, as well as fast and safe transportation of patients between the admission room, obstetrics department and operating theatres also influence the DDI.
| Assessment|| |
The pre-anaesthetic evaluation of a parturient coming for emergency caesarean section should include a rapid assessment to determine the risk of difficult airway, obstetric haemorrhage and risk of aspiration. The preoperative investigations required are complete blood count, blood grouping and cross matching and if absolutely necessary renal function, liver function tests and coagulation profile. These investigations should be ordered and the administration of anaesthesia continued.
| Preoperative Preparation|| |
All patients coming for a caesarean section need to be prepared for general anaesthesia and measures to prevent haemorrhage have to be taken. Preoperative preparation includes in utero resuscitation of the foetus [Table 4], administration of acid aspiration prophylaxis, preparing for a potential difficult airway, securing intravenous access (should have a 2nd IV access ready), prepare for prevention of haemorrhage and invasive monitoring if required and if time permits, especially in category 1 caesarean sections. All mothers coming for emergency caesarean sections are at high risk of aspiration, especially as recent guidelines advocate that mothers consume solids and liquids during normal labour. Oral sodium citrate, ranitidine and metoclopramide IV can be used as acid aspiration prophylaxis. Sodium citrate 30 ml 0.3 M is to be administered at least 20 min before induction of general anaesthesia. Studies advocate that it can be administered just before shifting to the operation theatre. There is an increase in the gastric volume, but the pH is also increased. The other disadvantage with sodium citrate is the high incidence of nausea and vomiting. Hence, it is not advised in patients receiving regional anaesthesia.,
| Anaesthesia for Category 1 Caesarean Delivery|| |
Modes of anaesthesia
Rapid sequence induction of general anaesthesia is the choice in category 1 caesarean section unless general anaesthesia is contraindicated. In such situations, spinal anaesthesia and epidural anaesthesia (especially if epidural has already instituted for labour) may be considered. Rarely, local infiltration and caesarean section may also need to be considered.
Rapid delivery of the foetus is the goal in category 1 caesarean delivery when there is threat to life of mother or foetus. The time taken to achieve surgical anaesthesia should be kept as short as possible. Although regional anaesthesia has been advocated in well trained hands, general anaesthesia remains the technique of choice for such deliveries.
The role of anaesthesiologists starts from the time of decision to deliver by caesarean section is made. It includes maternal stabilisation and in utero foetal resuscitation as described in [Table 4]. With the declining trend towards selecting general anaesthesia for category 1 cases, there is an increased likelihood that a trainee's first experience of caesarean section under general anaesthesia will be an emergency case. Hence, best practice demands competency-based training and assessment of anaesthesiologists covering obstetric units. Certain special considerations are to be kept in mind to conduct safe general anaesthesia in challenging circumstances.
Prophylaxis against acid aspiration
All parturients are considered to be at high risk for aspiration due to a relaxed oesophageal sphincter caused by progesterone, prolonged gastric emptying time and pressure of gravid uterus on the diaphragm. H2 receptor antagonists (Ranitidine 50 mg intravenously) or proton-pump inhibitors (e.g., pantoprazole 40 mg intravenously) and prokinetic agents such as metaclopramide 10 mg intravenously are routinely used to reduce acid aspiration and the subsequent risk of chemical pneumonitis. Sodium citrate is also preferred because of its advantage of instantaneous action.
To prevent neonatal depression, induction of anaesthesia is usually carried out after the patient is catheterised, the abdomen is draped and surgeons scrubbed. Left lateral tilt is recommended to avoid aorto-caval compression. A 30° head-up tilt is preferred as it is found to be useful in improving maternal well-being through an increased functional residual capacity (FRC), reduced breast interference to intubation and reduced gastro-oesophageal reflux.
As FRC is reduced by 40% at term gestation and oxygen consumption is increased by 20%, oxygen reserves get rapidly depleted. This warrants pre-oxygenation with 100% oxygen using a tight-fitting face mask that can be achieved by tidal volume breathing for 3 min or performing 4 to 8 vital capacity breaths.
Intravenous induction agents
Rapid-sequence technique is preferred for induction of general anaesthesia. Thiopentone (5 mg/kg of lean body weight) and succinylcholine 1.5 mg/kg are currently the agents of choice. Recently, researchers have suggested that rocuronium–sugammadex combination may replace succinylcholine in the near future. Propofol is generally not preferred in obstetrics due to associated poorer neonatal profile, shorter duration of amnesia potentially leading to awareness and longer time to recovery of spontaneous ventilation. Other drugs that can be used in pregnancy are etomidate and ketamine.
Ideally cricoid pressure of 10 N should be applied on the cricoid cartilage towards the body of C6 vertebra, and the pressure should be directed perpendicular to the tilted table. The pressure is increased to 20 to 40 N after induction and kept in place until tracheal intubation with ETCO2 is confirmed and till the cuff of the tracheal tube is inflated.
Due to placental transfer of the drug and known incidence of low APGAR in neonates, opioids are usually avoided in obstetric cases till the extraction of foetus. To suppress the laryngeal reflexes during laryngoscopy, non-opioidal drugs such as esmolol, nitroglycerine and magnesium sulphate can be used. However, in pregnancies complicated by severe cardiac disease or hypertensive disorders, ultra-short-acting opioids such as remifentanil or fentanyl can be used, provided this information is passed onto attending neonatologist.
Supraglottic airway devices for general anaesthesia in obstetric patients
Supraglottic airway devices are rescue devices that can be used to maintain oxygenation in women with difficult mask ventilation as well as in those with difficult intubation. Second generation supraglottic airway devices hold great potential in the management of the obstetric airway. The LMA Proseal™ incorporates a second tube intended to permit continuity with the gastrointestinal tract and isolation from the airway, minimizing gastric insufflations during positive-pressure ventilation.
Minimum monitoring standards as recommended by American Society of Anesthesiologists is advised during general anaesthesia in obstetric patients. Monitoring of end-tidal carbon dioxide (ETCO2) is found to be beneficial in preventing oesophageal intubation and endobronchial intubation. Anaesthesia is generally maintained with inhalation agents such as isoflurane and sevoflurane. Halothane is usually avoided because of its uterine-relaxant effect. Nitrous oxide is preferred by some because of its rapid onset and intra-operative analgesia. End-tidal agent monitoring can be used to titrate the anaesthetic depth. The FiO2 level is guided by the underlying maternal and foetal conditions.
Given the risk of aspiration in unprotected airway, it is advised that the parturient is fully awake, with adequate reversal of residual neuromuscular block and pain free before considering for extubation.
Given the anatomical and physiological changes in pregnancy, the risk of cannot intubate cannot ventilate situation is a major disadvantage of general anaesthesia. The risk of failed intubation in pregnancy is at least 8 times higher than the general population.,
Top-up of epidural
It is advocated that women should be persuaded to have an epidural early in labour. This reduces the incidence of general anaesthesia (if emergency caesarean is required) in the parturient by 75%. With a well functioning epidural catheter, top-up technique has shown that decision to delivery time is as fast as that for general anaesthesia. As the speed of onset is important in top-up technique, the choice of local anaesthetic and the adjuvant used plays an important role. Commonly used local anaesthetics are 2% lignocaine, 2-chloroprocaine or 0.75% ropivacaine, with or without additives for epidural top-ups. For a successful block, it is important to inject the epidural top-up solution as early as possible after the decision of emergency caesarean section has been made. Injecting the top-up solution in labour room and commencement of monitoring before shifting the parturient to operating room avoids the delay in the onset of action of the local anaesthetic. Sometimes top-up technique leads to inadequate block for emergency caesarean section, leading to patient discomfort, pain and need to convert to general anaesthesia. If the efficacy of epidural analgesia during labour is poor, consider converting to spinal or general anaesthesia. When converting partially acting epidurals to spinal, the risk of high spinal exits, and the anaesthesiologist has to be aware of it.
Rapid sequence spinal anaesthesia
In skilled hands, spinal anaesthesia can be as rapid as general anaesthesia with low failure rate and has to be considered in emergency caesarean section. Currently, the emphasis is on ‘Rapid Sequence Spinal Anaesthesia’, where the term ‘rapid sequence’ is used to emphasise the idea of performing spinal with bare essentials and limiting the number of attempts at insertion. Parturients are informed that general anaesthesia will be used if there are any delays in establishing adequate surgical anaesthesia with the spinal technique. The drug of choice will be 0.5% bupivacaine heavy, 2 chlorprocaine, 0.75% ropivacaine or levobupivacaine. Addition of an adjuvant such as lipophilic opioid fentanyl will shorten the time of onset of the block. The umbilical artery pH of the neonates is about the same when the caesarean is performed under general anaesthesia, but umbilical arterial cord base excess has been shown to be less negative when regional anaesthesia has been used.
The sequence in a ‘Rapid Sequence Spinal’ are as follows:
- Deploy other staff to secure the intravenous line
- Preoxygenate during the attempt
- 'No Touch Technique' use only gloves, chlorhexidine on swab to paint and use glove packet as sterile surface
- Local injection not mandatory
- Add 25 mcg fentanyl, if there is time. If not consider increasing the dose of bupivacaine
- Only one attempt at spinal unless obvious correction allows a successful second attempt
- Start surgery once sensory level >T10 and ascending. Be ready for general anaesthesia and inform the mother.
Category 2 and 3 caesarean sections
It has been advocated that in category 2 caesarean sections, the DDI is maintained at 30–75 min. Although general anaesthesia may be considered, it is not the technique of choice. General anaesthesia has been known to increase the morbidity and mortality in mothers by as much as 16 fold. The complications that can occur with general anaesthesia (pulmonary aspiration, unanticipated difficult airway) in comparison to manageable complications of spinal or epidural anaesthesia make it the last technique of choice.
Complications of emergency caesarean sections
Subsequent to the NICE guidelines many studies have been conducted to know the effect of the DDI times on maternal and foetal outcome. Most of these studies have found an improved foetal outcome with no change in the rate of maternal complications.
The most common complications in emergency caesarean sections are mentioned in [Table 5]. Failed intubation and pulmonary aspiration which are more commonly encountered during emergency situations have been dealt with in this article.
The incidence of failed intubation is 10 times more in the obstetric population. This incidence further increases if the parturient is obese. The reasons for increased risk of failed intubation are increased fatty tissue, increased oedema of pharyngeal and laryngeal tissue, complete dentition, large tongue and large breasts. The present day practice of choosing spinal anaesthesia over general anaesthesia in parturients may reduce the man-hour experience in young trainees and contribute further to the incidence of failed intubation. The main motive while facing a failed intubation is to maintain oxygenation. The failed intubation drill has to be practiced regularly. The 2015 Difficult Airway Society and 2016 All India Difficult Airway Association guidelines advocate the change of blade or change to a video laryngoscope if the first attempt to intubation is unsuccessful. A second failed attempt should pre-empt the use of other oxygenation measures like the use of a supraglottic airway device. In emergent caesareans, the surgery can be continued if oxygenation can be maintained. In situ ations where oxygenation cannot be maintained emergency front of neck access needs to be established. In these situations, the mother's life takes precedence over trying to save the foetus.,
Pulmonary aspiration in pregnant women is mainly due to the effect of progesterone on the lower oesophageal sphincter tone and the mechanical displacement of the stomach upwards by the gravid uterus, reducing the angle between the stomach and the oesophagus. The incidence of aspiration in caesarean sections under general anaesthesia is around 1 in 400–600. Aspiration can lead to inability to visualise the larynx during intubation, obstruction to ventilation and acid aspiration syndrome. The treatment of aspiration involves supportive measures and oxygenation. Measures to prevent aspiration include anti-aspiration prophylaxis, antiemetics, head up tilt and rapid sequence intubation.
| Summary|| |
Management of category 1 caesarean sections remains a challenge. Although rapid sequence spinal anaesthesia is an alternative, general anaesthesia still remains the preferred technique. Rapid assessment, team effort and intervention by an experienced obstetrician and anaesthesiologist can reduce the morbidity and mortality associated with category 1 caesarean sections.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]