7: Collapse, cardiac arrest and shock in pregnancy

CHAPTER 7
Collapse, cardiac arrest and shock in pregnancy


This chapter addresses the aetiology, identification and treatment of collapse and cardiac arrest, and shock during pregnancy. As the management of adult cardiac arrest is well documented in the Resuscitation Council (UK) guidelines, which are regularly updated, this chapter discusses only those differences specific to obstetric patients.


7.1 Cardiac arrest in pregnancy


Incidence


Cardiac arrest in pregnancy is rare, with maternal mortality rates varying by age, socioeconomic status and ethnic background. The higher rates are seen amongst older women, some ethnic minority groups and those living in the most deprived areas of the UK (MBRRACE‐UK, 2015a).


Principles of resuscitation during pregnancy


The principles of resuscitation for the pregnant woman are similar to those of any adult cardiac arrest patient. Due to the physiological changes, after 20 weeks of pregnancy, some modifications to standard adult cardiac arrest algorithms are required to improve the efficiency of resuscitation.


Although the fetus can tolerate quite significant levels of hypoxia, it is still reliant on the mother’s body for delivery of oxygenated blood. Consequently, resuscitation of the mother should always be initiated immediately, even if her injuries appear to be unsurvivable, and resuscitation should not be terminated in the pre‐hospital setting. This approach will maximise the chances of both maternal and fetal survival.


The following section provides a summary of the main physiological changes that will require the pre‐hospital practitioner to modify their approach:


Airway


The mucosal lining of the upper airways become oedematous and slightly swollen due to hormonal changes of pregnancy. Airway insertion, specifically the nasopharyngeal airway, is associated with an increased risk of failure or minor trauma compared with the non‐pregnant patient. In general, airways with a smaller internal diameter should be selected, and nasopharyngeal airways avoided (Battaloglu and Porter, 2016).


Particularly during the late stages of pregnancy, the gastro‐oesophageal sphincter becomes lax, gastric emptying is delayed, gastric pressure rises and gastric fluids become more acidic, representing a significantly increased risk of regurgitation and aspiration pneumonia. Consequently, rapid escalation of airway interventions to insertion of a cuffed endotracheal (ET) tube is essential. Whilst this is the gold standard in airway management, if unavailable or an attempt fails, a supraglottic airway device such as an i‐gel® will allow effective oxygenation but not protection from aspiration.


Breathing


It is estimated that the relaxed diaphragm will be elevated by the gravid uterus by up to 4 cm in the third trimester. The decreased compliance of the chest wall and splinting of the lungs by the diaphragm makes lung expansion much more difficult to achieve and requires higher pressures to facilitate, again potentially increasing the risk of gastric distension, regurgitation and aspiration. The added weight of engorged breasts may also contribute to reducing chest wall movement. Consequently, the mother’s functional residual capacity will be reduced and the requirement of good bag–valve–mask (BVM) technique is paramount. The sizing of the face mask will remain unchanged.


Circulation


Due to the risk of aortocaval compression, a collapsed patient must be positioned in a left lateral tilt of between 15° and 30° or with the uterus manually displaced. However, when faced with a patient in cardiac arrest, the ability to deliver effective chest compressions is compromised when the patient is tilted and this will adversely affect the efficacy of any resuscitation attempt. Manual uterine displacement is now the recommended technique to overcome this. In addition to enabling effective chest compressions, manual uterine displacement enables easier access for airway management, bilateral vascular access and defibrillation.


Failure to reduce the risk of aortocaval compression will mean that oxygenated blood cannot be circulated to the mother or fetus. Occasionally, repositioning the uterus relative to the major blood vessels may reveal a profound syncope induced by aortocaval compression that has been misdiagnosed as a cardiac arrest.


Pre‐hospital management


Patient positioning


Manual uterine displacement can be performed from the left of the patient (Figure 7.1) where the practitioner ‘cups’ and ‘lifts’ the uterus upwards and to the left off the maternal vessels. If the patient is loaded into an ambulance head first, manual uterine displacement can also be achieved from the right of the patient (Figure 7.2), where the uterus is pushed upwards and to the left. Care must be taken not to inadvertently push down, which would increase the amount of inferior vena cava compression and cancel any potential benefit.

Photo demonstrating manual uterine displacement, wherein the practitioner’s hands are cupping and lifting the uterus upwards and to the left off the maternal vessels of a patient lying on the floor.

Figure 7.1 Manual uterine displacement (‘cupping’ technique)

Photo demonstrating manual uterine displacement wherein the practitioner (right of the patient) is pushing the patient’s uterus upwards and to the left, while another practitioner is holding the patient’s head.

Figure 7.2 Manual uterine displacement (push technique)


Lateral tilt can be achieved by using an improvised wedge under the patient or by placing the patient on an immobilisation device before tilting (see Chapter 6). It is also a technique that can be used when fewer team members are present, for instance when transferring a patient in the ambulance with only one clinician in the saloon.


Airway


The sizing and insertion of an oropharyngeal airway and supraglottic airway (SGA) device are unaltered. Care should be taken when inserting a nasopharyngeal airway due to the increased friability of the upper airway mucosa. With regard to selecting an ET tube it is recommended that the size should start at 7.0 and proceed to smaller tube selection if needed (size 6.0 and 5.0) as there is an association between larger tubes and glottic and tracheal damage in women (MBRRACE‐UK, 2017).


Intubation of the trachea during the late stages of pregnancy can also be particularly challenging, due to:



  • Presence of full dentition
  • Short obese (oedematous) neck
  • Engorged breasts
  • Oedema and swelling of the upper airway
  • Risk of regurgitation during intubation

Any strategy for the intubation of patients in the late stages of pregnancy must have the aim of minimising the time from commencing laryngoscopy to inflation of the tracheal tube cuff to reduce the risk of aspiration. All such interventions are, therefore, ‘crash’ intubations (Box 7.1). Additionally, any practitioner attempting to secure the airway must have a ‘failed intubation’ plan that should include the availability of a SGA device, such as the i‐gel® or laryngeal mask airway (LMA).

Mar 9, 2019 | Posted by in EMERGENCY MEDICINE | Comments Off on 7: Collapse, cardiac arrest and shock in pregnancy
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