Introduction

Cardiothoracic post-anaesthesia care has evolved significantly in the last 20 years and poses several challenges for the post-anaesthetic care unit (PACU) practitioner. Firstly, the shift towards minimally invasive procedures, where possible, has been beneficial for both cardiac and thoracic patients, who often have more than one pre-existing comorbidity. This has led to a higher turnover of patients and an increased focus on the principles of enhanced recovery. However, another development within PACU care has been the pressure on the availability of high-dependency and intensive care beds, which has led to more PACUs developing specialist fast-track critical care and extended recovery facilities for these patients (Mallett, Albarran & Richardson 2013). These developments have served to increase critical care capacity by encouraging practitioners to adopt a more flexible approach to the delivery of critical care and minimise cancellations of elective or scheduled surgery. This has facilitated the prompt admission of emergency cases to the most appropriate critical care area according to their level of need.

In view of these developments, it is important to consider the legal and ethical challenges faced by PACU practitioners, in terms of working within the boundaries of safe practice. The National Competency Framework for Adult Critical Care Nurses (2015) sought to address these issues by assessing competence at three levels, according to the level of skill, knowledge and expertise required by PACU practitioners to maintain competence and the level of care required by these patients. One of the main issues is consistency of exposure to critical care practice; lack of consistent exposure can leave PACU practitioners vulnerable to practising outside their scope of practice (NMC 2015, HCPC 2018).

Moreover, the demographics of the population have changed. We have an aging population who are living longer, with complex care needs due to pre-existing comorbidities such as obesity, ischaemic heart disease, chronic obstructive pulmonary disease and diabetes mellitus (Klein & Arrowsmith 2013). This is by no means an exhaustive list; however, it does highlight some current healthcare challenges.

Minimally invasive procedures have facilitated enhanced recovery programmes aimed at reducing the length of hospital stays and improving patient outcomes. However, in cardiac surgery, the use of minimally invasive techniques is limited due to patient factors and surgical factors. For instance, bariatric patients, and patients who have had previous cardiothoracic surgery or have extensive pulmonary disease will often not be suitable candidates. Surgeons need considerable exposure to develop the necessary techniques and longer operating times for these patients can therefore represent a significant cost. Nevertheless, with appropriate patient selection, patients recover faster, and experience less surgical trauma and pain, which improves their quality of life (Glowaski 2015).

Health and safety

In the PACU, health and safety includes all the equipment and safety checks, checking stock levels of consumable items, drugs, point of care testing (Glucometer, Haemacue), the blood fridge, emergency trolley, difficult airway trolley, ventilator/portable ventilator, transfer bag, and ensuring that all infusion pumps are fully charged. Each recovery bay should have a selection of oxygen delivery devices, both fixed and variable, to suit the needs of all patients (particularly patients with chronic obstructive pulmonary disease), including venturi masks, Hudson masks, a Mapleson C circuit and self-inflating bag (Ambu). Humidified oxygen should be readily available if needed. A selection of airway adjuncts, suction and suction catheters should be available and working. The emergency call bell should be tested every day to ensure it is working properly.

Every bay area should be cleaned before each patient arrives to prevent the risk of cross-infection. Personal protective equipment should be worn, and standard precautions used, to protect the practitioner from exposure to bodily fluids and blood-borne viruses such as hepatitis and human immunodeficiency virus. All completed checks must be documented and signed by the PACU practitioner, at the beginning of every shift, to allow for tracking and traceability so the person(s) responsible for performing those checks are clearly identifiable. The implications and consequences of not performing these checks properly and thoroughly are possible morbidity or mortality for the patient, loss of registration for the practitioner and possible litigation for the hospital (HCPC 2018; NMC 2015; Hatfield 2014).

Staffing and organisation

Staffing ratios need to reflect the acuity of patient care required. A high turnover of patients will require a high ratio of staff to cope with the influx of patients and to manage their discharge safely and effectively. Furthermore, a level 2/3, patient (who requires extended, complex postoperative care) can have very demanding care needs. These patients are at higher risk of developing complications related to their airway, breathing and circulation than any other group of patients. Firstly, they have pre-existing disease in these systems. Secondly, the surgery and anaesthesia are going to directly affect the functioning of these systems. Lastly, these systems are inter-related, so complications arising in one system will lead to complications in others. This is particularly true with the cardiovascular system, respiratory system, nervous system and musculoskeletal system (see Table 13.1).

Handover

Teamwork and collaboration are vital in the handover of care from the operating theatre to the PACU to ensure patient safety and improve patient outcomes.

The SBAR tool (National Health Service Improvement 2017) provides a systematic, standardised approach that facilitates this handover of care of the acutely ill patient. The situation relates to the patient’s stability and any adverse events that have occurred in the operating room. Adverse events relating to the anaesthetic, or that may affect haemodynamic stability, are usually communicated by the anaesthetist; whereas the surgical aspect is usually communicated by the scrub practitioner and/or surgeon. The patient’s current cardiovascular and respiratory status, and any specific treatment and care required, are also communicated in the handover (Intensive Care Society 2012; Mallet et al. 2013).

An example of how the SBAR can be adapted is highlighted in Table 13.2. This format should be repeated when the patient is discharged from the PACU, ensuring that the discharge criteria are met.

Table 13.2: The Situation, Background, Assessment and Recommendations (SBAR) tool

Monitoring requirements

The first principle is to look at the patient first (and not the monitor) to assess the patient’s condition. Secondly, do not assess one system in isolation, such as the respiratory system, as vital signs are inter-related. One vital sign will often affect other vital signs – for example, hypotension often leads to tachycardia. Thirdly, it is important to observe trends rather than individual values. Lastly, it is important to consider any pre-existing comorbidities and the patient’s preoperative values when assessing their postoperative physiological status. For example, if a patient was only able to achieve an oxygen saturation of 92% on 28% oxygen preoperatively, because of their COPD, it would be unreasonable to expect better readings postoperatively. Best practice is to compare previous readings and assess for any trends for early detection of deterioration in the patient (Jevon, Ewens & Pooni 2012). Specific monitoring requirements will be discussed in more detail as part of the ABCDE approach to assessment.

The ABCDE approach

The ABCDE approach refers to assessing the patient’s:

• Airway

• Breathing

• Circulation

• Disability

• Exposure.

Airway

There are three important aspects to consider in managing the airway in cardiothoracic patients:

• Airway patency

• Mobilisation of secretions through physiotherapy, postural drainage and suctioning

• Humidification.

The sooner these patients are able to maintain their own airway, the better the outcome.

Airway patency

Airway obstruction falls into two categories:

• Anatomical obstruction

• Physiological obstruction.

Physiological obstruction can be caused by laryngospasm because of excess secretions irritating the vocal cords, trauma to the larynx or premature endotracheal extubation. Furthermore, excess secretions, particularly following bronchoscopy, can obstruct the airway. It is therefore important that all sputum is checked for consistency, colour and amount for signs of bleeding (particularly if a biopsy has been taken). Pink frothy sputum indicates pulmonary oedema, and green or yellow sputum could indicate infection. The wearing of personal protective equipment is recommended, particularly gloves and visors to protect PACU practitioners from blood splatter, contamination from blood-borne viruses, tuberculosis and airborne pathogens (British Thoracic Society 2016).

Cardiothoracic patients are at risk of aspiration for many reasons. Firstly, they may have a hiatus hernia. Hiatus hernia is more common in overweight patients, due to the raised intra-abdominal pressure exerted on the cardio-oesophageal sphincter which can force part of the stomach through the diaphragm and into the thoracic cavity. Secondly, the effects of anxiety increase gastric acid production which lowers the pH of the gastric contents. This means that gastric aspirate will cause more damage to the lungs. Consequently, these patients are commonly prescribed proton pump inhibitors, and antacids preoperatively to reduce the amount and the pH of stomach contents respectively.

Bronchospasm is common, and in patients with acute hypercapnic respiratory failure (AHRF) sometimes Heliox (a breathing gas composed of a mixture of helium and oxygen) can be used to reduce airway resistance and improve oxygenation (BTS 2016). Furthermore, bronchospasm can be caused by trauma to the bronchial tree, the presence of pre-existing conditions (such as asthma and COPD) and certain drugs such as opioids and non-steroidal anti-inflammatory drugs.

Pulmonary oedema is common in cardiothoracic patients. It can be caused by barotrauma to the lungs that has occurred during complete airway obstruction or it can be cardiac in origin; due to circulatory overload and/or cardiac failure. Therefore, it is important to establish whether it is cardiac or respiratory in origin.

Airway management

Basic airway manoeuvres are skills that must be developed to maintain the safety of patients in the PACU. A patient with an obstructed airway is at risk of hypoxia. The loss of an airway could be due to loss of muscle tone in the tongue and pharynx. Simple airway manoeuvres such as head tilt/chin lift can rectify this or, alternatively, use the jaw thrust in patients with a suspected cervical injury or history of rheumatoid arthritis where there could be a risk of causing trauma to the spinal cord.

Mobilisation of secretions

Mobilisation of secretions is important to prevent the development of hypostatic or ventilator-assisted pneumonia caused by the accumulation and consolidation of copious secretions. The following measures will help to minimise these risks:

• Frequent turning

• Encouragement of deep breathing/assisted coughing

• Early ambulation

• Effective pain management (Intensive Care Society 2014).

Physiotherapy

Regular chest physiotherapy is often prescribed for these patients and it may start within the PACU. Early intervention can prevent pneumonia, particularly in patients with chronic lung conditions such as cystic fibrosis.

In terms of postural drainage, patients in a semi-recumbent position will achieve greater postural drainage than a patients who are supine. This will reduce the risk of developing pneumonia (ICS 2014). Furthermore, the ventilation-perfusion ratio is the least compromised in this position because the optimal surface area of lung is available for oxygenation of the pulmonary circulation.

Humidification

The nasopharynx, which provides natural humidification for the airway, has been bypassed during anaesthesia. It is essential that adequate humidity is provided to keep the airway moist following cardiothoracic surgery, for the following reasons:

• It prevents the drying of secretions

• It prevents the tube/airway blocking with secretions

• It maintains cilia function.

Types of humidification

The patient must be sufficiently hydrated with intravenous (IV) fluids to allow the mucosal surface to remain moist and to ensure that the secretions stay thin and can be easily mobilised by the cilia. Oxygen delivery devices should be connected to a humidifier. Heated humidification should be considered for thick tenacious secretions and mucosal dryness (BTS 2016), particularly in patients who are still ventilated or have a tracheostomy in situ. Furthermore, in an intubated patient, a heat and moisture exchanger with a bacterial filter should be attached to the circuit, to prevent heat loss from the patient’s lungs.

Saline nebulisers should be considered if problems with inadequate humidification persist. Mobilisation of secretions, physiotherapy, postural drainage and the use of nebulisers can all help to reduce the risk of segmental collapse within the lungs.

Basic oropharyngeal suction can be applied to clear secretions from the oropharynx and help to maintain and clear the upper airway. Secretions obstructing the lower airway (below the larynx), which cannot be mobilised by the patient through deep breathing and coughing, may need to be aspirated using endobronchial suction.

Procedure for endobronchial suctioning:

• A clear explanation of the procedure, with reassurance, will help reduce the patient’s anxiety and fear.

• Partial occlusion of the airway by the suction catheter, combined with aspiration of air from the lung while using an open suction system, can result in severe hypoxia, cardiac arrhythmias, and even cardiac arrest. Suctioning procedures must never exceed 15 seconds even if no visible signs of stress are noted.

• The upper airway is lined with delicate tissue, and care must be taken to avoid damage to these tissues during suctioning. Suction must be applied only intermittently and with catheter rotation to avoid trauma to the mucosal walls of the trachea and bronchi.

• Suction is applied only during withdrawal to decrease the volume of air removed from the lungs and decrease the hypoxic effect and trauma to the airway.

• The maximum outer diameter of the suction catheter should be no more than half the internal diameter of the tracheostomy tube. A suction catheter of greater diameter could lead to obstruction of the air flow around the catheter during the procedure. When a closed suction system is used, this atmosphere will be oxygen enriched or will be supplied by the ventilator.

The closed ventilation suction system catheter allows the practitioner to maintain mechanical ventilation during the suction procedures. Suctioning without disconnecting the patient from the ventilator reduces many of the problems associated with open suction systems. This system has two advantages:

• It reduces the possibility of cross-contamination, protecting both the patient and practitioner with an enclosed catheter and thumb valve

• The dual-lumen system makes it easier to instil saline for lavage and irrigation as well as to administer endotracheal medications through a separate inner lumen.

Breathing

The early return of spontaneous breathing after extubation is particularly important in cardiothoracic patients to prevent ventilator-associated complications such as pneumothorax or pneumonia. Postoperative ventilation is avoided, whenever possible, due to the risk of regional lung collapse and pulmonary infection. Ventilation in thoracic patients is usually due to complications in surgery or inappropriate selection of patients preoperatively (Klein & Arrowsmith 2013).

It is important to assess how effectively the patient is breathing. The efficacy of breathing can be determined by assessing air entry and chest movement, monitoring pulse oximetry and analysing arterial blood gases.

Hypoventilation can occur postoperatively due to the residual effects of:

• Anaesthetic agents

• Opioids

• Benzodiazepines

• Inadequate reversal of neuromuscular blocking drugs.

All these drugs will suppress respiration. Therefore, administration of these agents in cardiothoracic patients must be closely monitored so that the doses administered provide the maximum therapeutic effect without the associated potential adverse effects. Nitrous oxide is best avoided in these patients due to the risk of diffusion hypoxia which can adversely affect oxygenation.

Air entry is a significant aspect of postoperative patient care, particularly following cardiothoracic surgery. The PACU practitioner should be able to establish and compare the breath sounds in the apices and bases of each lung. Absent or abnormal breath sounds should be reported to the anaesthetist. Air entry and chest movements may not be equal on both sides in thoracic patients, so it is important for the PACU practitioner to establish the patient’s previous medical and surgical history to consider any pathology (e.g. tumour) or previous surgery (e.g. pneumonectomy) that would explain unequal air entry or chest movement.

Breathing should be symmetrical in most patients. Asymmetrical breathing/chest movement may be due to pneumo/haemothorax, damage to the pleura during surgery, due to trauma (penetrating injury) or consolidation of secretions. The development of asymmetrical breathing in patients with intrapleural drains may indicate blockage or disconnection and should be reported immediately to the anaesthetist or surgeon, as immediate intervention is required to reconnect the drain and remove the blockage. The rectification of these complications should always be confirmed by a chest radiograph (Woodrow 2013).

Pulse oximetry monitoring is integral to assessing the efficacy of breathing. The major benefit of pulse oximetry is that it gives an instantaneous reading that provides the PACU practitioner with an overall picture of the patient’s condition. However, pulse oximetry does not replace observing the patient, especially the patient’s pallor (pale, clammy, sweaty), which can often indicate deterioration sooner. Pulse oximetry must always be considered as an adjunct to overall physiological assessment of the patient (Jevon, Ewens & Pooni 2012).

Pulse oximetry has limitations, in that it will detect hypoxaemia (poor oxygenation within the capillaries) but not hypoxia (poor oxygenation of the tissues). Hypoxia is common in hypothermia because it slows the release of oxygen from the haemoglobin, which can lead to poor peripheral perfusion and low oxygen saturations. Since oxygen saturations are calculated by how much light is reflected, other conditions that alter the colour of haemoglobin will also affect the accuracy of pulse oximetry – for example, carbon monoxide poisoning, the presence of methylene blue and jaundice. Furthermore, wearing nail polish and false nails can interfere with its accuracy.

Its accuracy also depends on using the right probe for the patient and their circumstances; for example, an ear probe may be more appropriate if the patient is hypothermic or restless. Prolonged pressure can cause pressure ulcers on the fingers, particularly where the perfusion is poor, so care must be taken when using probes in patients with clubbing of the fingers. Inappropriate use of finger probes (for example, on the ear and the nose) can increase the risk of pressure ulcers. To minimise this risk and prevent stiffness in the finger joints, the finger probe should be moved hourly and the digit regularly flexed to prevent mechanical injury (Jevon, Ewens & Pooni 2012).

It is important to document supplemental oxygen when monitoring oxygen saturations. Oxygen saturations should not be observed in isolation. It is also important to observe trends (more than absolute values) in order to assess the patient’s physiological status and to detect early signs of deterioration. Pulse oximetry should always be assessed in conjunction with other vital signs – particularly capnography to ensure adequacy of ventilation, and gaseous exchange to support oxygenation and prevent carbon dioxide retention.

The final tool in assessing the efficacy of breathing is arterial blood gas analysis. When analysing an arterial blood gas sample, a small amount of arterial blood is taken to assess:

• The effectiveness of gaseous exchange and ventilation

• The patient’s metabolic status and response to critical illness.

Arterial blood gas analysis is important to ensure that the patient is achieving adequate oxygenation and tissue perfusion, to evaluate ventilation and the patient’s acid-base balance and to prevent cellular damage which could lead to organ failure. The normal values are:

• PAO₂: 10-3kPa

• PCO₂: 4.5-6kPa

• SAO₂: 95-100%

• pH: 7.35–7.45

• HCO₃ (Bicarbonate): 22–28mmol/l.

• Base excess: -2 to +2 (Woodrow 2012).

The PACU practitioner should understand the basics of acid-base balance and how it is controlled. Acid-base balance is controlled through three mechanisms:

• Renal

• Chemical buffering.

Normal cellular function relies on the pH of blood and the cerebral spinal fluid (CSF) to remain within the normal parameters. The enzymes involved in cellular processes cease to function if the pH is not maintained within the normal range.

The aim of the respiratory mechanism is to maintain the pH by exhaling carbon dioxide through the lungs. In the blood, carbon dioxide combines with water to create carbonic acid. In the lungs, carbonic acid dissociates into water and carbon dioxide with the help of an enzyme known as carbonic anhydrase:

In patients with AHRF, the pH cannot be maintained through the respiratory mechanism alone because the carbon dioxide rises faster than it can be exhaled by the lungs. This leads to respiratory acidosis, which is the failure to excrete sufficient carbon dioxide. In these patients, the pH will be low and the carbon dioxide will be high. However, in chronic lung disease, the pH is maintained through the metabolic pathway. In the metabolic pathway, these acids are removed through the kidneys and buffered by bases (e.g. bicarbonate). Bicarbonate binds with the hydrogen ions to neutralise them.

The kidneys play a vital role in controlling the number of hydrogen ions and bicarbonate ions that are reabsorbed or excreted to maintain blood pH. In patients with chronic lung disease their carbon dioxide can remain high, but their pH can remain normal because their kidneys use this pathway to compensate (this is known as renal compensation). Metabolic acidosis is the failure to excrete or buffer sufficient hydrogen ions. A patient with metabolic acidosis will have a negative base excess of <-2 and bicarbonate level of <22mmol/l (Woodrow 2012).

The four-step approach to easy arterial blood gas interpretation