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The intensive care unit


This chapter provides an overview of general adult intensive care, the key components of which are resuscitation and stabilisation; physiological optimisation to prevent deterioration and organ failure; support of failing organ systems; and management and communication with patients and family of likely treatment outcomes, including potential failure. Levels of care have been described from level 0 (ward-based care) to level 3 (patients requiring advanced respiratory support alone or a minimum of two organs being supported) ( Box 48.1 ). However, the ideal is a comprehensive system where the needs of all critically ill hospital patients are met with consistency rather than just those who are admitted to designated intensive care (ICU) or high-dependency (HDU) units.

Box 48.1
Levels of ICU care

Level 0

  • Requires hospitalisation

  • Patient's needs can be met through normal ward care

Level 1

  • Patients recently discharged from a higher level of care

  • Patients in need of additional monitoring/clinical interventions

  • Patients requiring critical care outreach service support, clinical input or advice

Level 2

  • Patients needing preoperative optimisation

  • Patients needing extended postoperative care

  • Patients stepping down to from level 3 care

  • Patients receiving single organ support including basic cardiovascular, renal or respiratory support

Level 3

  • Patients receiving advanced respiratory support alone.

  • Patients requiring a minimum of two organs supported

In the UK the ICU generally accounts for 1%–2% of the total number of acute hospital beds. The design of ICUs varies from hospital to hospital, but they are designated areas with high nurse-to-patient ratios (1:1, 1:2), continuous medical staff availability, provision for invasive monitoring and the ability to deliver organ support technologies. Minimum standards for the provision of intensive care services are published by the Faculty of Intensive Care Medicine (see further reading ).

Staffing an intensive care unit

The ICU team is multidisciplinary and involves contributions from a variety of medical and nursing staff, including physiotherapists, rehabilitation teams, dieticians, psychologists and pharmacists. Each has complementary experience and skills and good teamwork ensures high standards of quality patient care. Models of ICU decision making differ, broadly defined as ‘closed’ (ICU team takes primary responsibility for admission, management and discharge decisions) ‘semi-open’ (shared decision-making with referral multidisciplinary team, or MDT) and ‘open’ (decisions led by referring teams). However, such categories fail to appreciate the shared models in which patient decision-making is individualised; all decisions should also involve the patient and appropriate family members according to professional guidance and relevant legislation (see Chapter 21 ). Excellence in communication is paramount, both within the ICU and with other teams.

ICU consultants

Twenty-four-hour cover by a named consultant with appropriate expertise increases the quality of ICU care and decreases mortality. Difficult therapeutic and ethical decisions are often required; it is essential that these are taken by an individual with sufficient experience to allow a reasonable assessment of the likely outcome. Because of the nature of critical illness, the ICU consultants should be informed immediately of any significant change in their condition. Similarly, they should be informed of any potential admissions and see all patients within 12 h of admission and twice daily thereafter. The consultant's base specialty is less important than his or her appropriate training and experience.

ICU residents

The ICU junior medical staff have a pivotal role in the monitoring and co-ordination of all aspects of care. Each patients’ clinical state should be reassessed frequently because it may change quickly. There are many training opportunities available in the unit, and training should be focused on a competency-based programme.

ICU nursing staff

Nurses provide most of the direct patient care in the ICU; they have greatly extended roles, experience and responsibility. They undergo specific training to enable them to perform titration of fluid replacement, analgesia, vasoactive drug therapy and weaning from mechanical ventilation. It is essential that the bedside nurse is present and takes part during discussions with patients or their representatives in order to provide consistency in communication and decision making. These discussions must be recorded accurately in the patient's notes. The majority of ICU nurses have enormous experience with critically ill patients and are an invaluable resource in ensuring therapies are appropriate and patient centred.

Physiotherapists

Physiotherapists provide therapy for maintenance of respiratory function, including pulmonary secretion clearance, neuromuscular rehabilitation, and expertise on suitability for weaning from mechanical ventilation. Physiotherapy is used to help preserve joint and muscle function in the bedbound patient and promote independent mobilisation where possible. Early mobilisation and rehabilitation is considered important in recovery from critically illness, and advice from physiotherapists on a patient's changing physical status is invaluable.

Pharmacists

Polypharmacy is inevitable in the critically ill and there is great potential for drug interactions and incompatibility of infusions. Drug doses should be modified in critical illness because of altered pharmacodynamics or pharmacokinetics, especially in patients with hepatic or renal failure (see Chapters 1 and 20 ). Pharmacists have a vital role in providing detailed advice on drug therapies.

Dieticians

Maintenance of gut integrity and nutrition are important priorities in critical illness. The dietician will assess the patient's nutritional status and requirements and provide individually tailored support.

Microbiologist

Critically ill patients are at high risk of nosocomial infections. Contributing factors include:

  • the underlying pathological process itself and its consequences;

  • impaired organ function and disturbed homeostasis;

  • treatments such as immunosuppressant drugs, including steroids;

  • the presence of surgical/traumatic wounds, multiple invasive vascular catheters and other devices;

  • loss of protective airway reflexes and the potential for pulmonary aspiration;

  • alterations in gut mucosal integrity and normal microbial flora;

  • the environmental presence of multiresistant micro-organisms.

To treat sepsis effectively and prevent the spread of resistant pathogens, there should be a nominated microbiologist, familiar with the flora and resistance patterns of the unit, to advise daily on microbiology results and antibiotic therapy.

Outreach teams

The critical care outreach team collaborates between the unit and other areas of the hospital. Its main aims are:

  • to identify the deteriorating patient early with the aim of averting admission to ICU or facilitating appropriate ward-based treatments;

  • to alert the ICU admission team and assist timely admission to the unit if required;

  • to aid in appropriate discharge and follow-up from critical care.

A number of scoring systems based on abnormal physiological variables, such as the National Early Warning Score (NEWS) ( Table 48.1 ), can be recorded by ward staff; the outreach team can be contacted once a trigger score has been reached. Care should be taken with younger, fitter patients, who have good physiological reserve and whose NEWS score may not deteriorate until physiological decompensation occurs (e.g. in presence of bleeding or severe sepsis). Children and obstetric, neurological, renal and other specialty groups have adapted scores to allow for altered background physiological status.

Table 48.1
National Early Warning Score (NEWS) 2
Adapted from https://www.rcplondon.ac.uk/projects/outputs/national-early-warning-score-news-2 .
NEWS Score 3 2 1 0 1 2 3
Respiratory rate; breaths min –1 ≤8 9–11 12–20 21–24 ≥25
S p o 2 Scale 1 (%) ≤91 92–93 94–95 ≥96
S p o 2 Scale 2 a (%) ≤83 84–85 86–87 88–93; 93–94 on air 93–94 on O 2 95–96 on O 2 ≥97 on O 2
Breathing air or supplemental oxygen Oxygen Air
Systolic BP; mmHg ≤90 71–100 101–110 111–219 ≥220
Pulse; beats min –1 ≤40 41–50 51–90 91–110 111–130 ≥131
ACVPU U, P, V, C A
Temperature; °C ≤35 35.1–36 36.1–38 38.1–39 ≥39.1

AVPU is a simple assessment where A, alert; C , new-onset confusion disorientation or agitation; V, responds to verbal commands only; P, responds to pain; U, completely unresponsive.
Aid to clinical assessment to be used as part of initial evaluation of acute illness in all adult patients (aged 16 or more) and monitored throughout their hospital stay.
The NEWS-2 system uses 6 variables that are already monitored. Scores recommend frequency of monitoring, urgency of clinical review and competencies of the clinical team needed.
NEW score of ≥5 should trigger urgent clinical review and action.
NEW score of ≥7 should trigger urgent clinical review and action by a tea, with critical care competencies and usually transfer to a higher dependency area.
Potentially unreliable in patients with high spinal cord injury because of associated autonomic dysfunction.

a Use scale 2 if target range is 88%–92% as determined by clinician (e.g. in hypercapnic respiratory failure).

ICU admission and ethical decision-making

Early referral by the specialty medical team for an opinion regarding admission to ICU is preferable, before acute life-threatening deterioration occurs. The use of early warning scores based on vital signs can be helpful in this regard.

Most interventions in ICU are painful and potentially distressing. Mortality, morbidity and functional outcomes are often uncertain, resources are finite and costs are high. Even if financial resources were unlimited, the time that professionals have is finite. If the capacity of an individual patient to benefit or survive critical illness is limited, complex ethical issues can arise surrounding admission, provision and discontinuation of intensive care therapy. Hence it is important to identify those patients who will not benefit from further resuscitation or critical care support because of their acute illness or underlying diseases, so that harmful or futile interventions are not undertaken. Examples include very frail patients and those receiving palliative care. In these cases, appropriate ward-based care can be agreed and instituted. However, generic admission policies are usually unhelpful; decisions should be individualised to each patient, accounting for their wishes, values and outcomes most relevant to them.

The harms and benefits of all proposed interventions should be explained and understood by patients, families and the wider MDT, but this is often difficult to achieve within the time frames available for emergent decisions. Often patients do not have capacity to understand the complexity of the situation, and a shared decision in the ‘best interests’ of the patient should be taken by ICU teams, referring specialties and patient family or friends. Importantly, best interests should include all outcomes important to the patient, including social and emotional factors in addition to medical outcomes. Best interests decisions can be difficult and distressing for both staff and the patient's family. If a patient has made an advance directive, its contents must be respected, although application is often ethically and legally challenging and such documents remain rare in UK practice.

In essence the aim of intensive care is to support patients while they recover from the acute process that has generated the need for admission to ICU. It is not to prolong death when there is very little or no hope of meaningful recovery. In many cases, unless the outlook is obviously hopeless, patients may be admitted for a trial of treatment to assess the degree of reversibility and capacity for improvement over time. Conversely, admission of patients with little or no prospect of survival may occasionally be justified and appropriate. For example, admission to ICU of patients with perceived devastating brain injuries will ensure safety in prognostication, allow time for relatives to comprehend the situation and potentially reduce the impact of their bereavement, and facilitate appropriate palliative care.

Decisions about admission to ICU, institution or limitation/withholding of therapy, and withdrawal of life-sustaining treatment should be made using the fundamental principles of medical ethics:

  • 1.

    Respect for autonomy

  • 2.

    Beneficence

  • 3.

    Non-maleficence

  • 4.

    Distributive justice

Although many doctors can recount these four principles, application of them in practice is often partial. Instead many clinicians rely on heuristic default behaviours when faced with difficult decisions. This is problematic as it is rarely responsive to an individual patient's circumstances or preferences. Where possible the patient's previously expressed, autonomously held wishes and views should be respected, but patients and families do not have the automatic right to treatment regardless of the impacts elsewhere. Despite the potential for conflict inherent in such decision making, a shared decision can nearly always be made. Where disagreements occur they are often a result of misunderstanding and the breakdown of communication and relationships. Many legal systems will have a mechanism for the courts to take ultimate decisions in situations of conflict, but recourse to these ‘solutions’ is very rarely needed, and decisions taken in this way have very high emotional, financial and social costs.

Assessment of patients

When dealing with a newly admitted patient with acute disease, assessment and resuscitation often take place simultaneously and follow the standard pattern of recognising and dealing with problems in the order of airway, breathing and circulation. It is essential to approach the assessment of the patient in a systematic manner.

History

Often the patient is unable to give a full and accurate history. All possible details should be obtained from the patient's notes, a thorough handover from referring or transferring staff, old notes (which may need to be retrieved from the referring hospital), and information from the patient's primary care doctor. Speaking to the patient's relatives gives invaluable insight into the patient's premorbid condition. It is important that details in the history are not overlooked as it is relatively easy for misinformation to be perpetuated from one handover to the next.

Examination

It is imperative to adhere to unit policy regarding infection control. Scrupulous hand hygiene and the use of gloves and aprons are necessary before examination of the patient. A systematic approach is vital. Remember that although the patient may appear to be unconscious, hearing and other senses may still be intact, and dignity and respect should be maintained at all times.

Airway

Note how the airway has been secured, how long any tube (tracheal/tracheostomy) has been in place, relevant cuff pressures and type and volume of respiratory secretions. In a patient with traumatic injuries, ensure that the cervical spine has been stabilised appropriately.

Breathing

Auscultate the lungs to check for bilateral and equal air entry and added sounds. Check the type and adequacy of ventilation, as well as latest arterial blood gas results, and review the most recent and relevant past imaging data. If intercostal drains are present, ascertain their duration and drainage.

Circulation

Note the heart rate, rhythm, arterial pressure, jugular venous pressure (JVP), heart sounds, CVP, peripheral perfusion using clinical evaluation and monitored variables. Look for the presence of dependent or peripheral oedema. Venous and arterial catheter sites may reveal evidence of infection. Note the type and dose of positive inotropic or other vasoactive drugs required.

Disability (central nervous system)

Ascertain the patient's level of consciousness as well as the dose and duration of sedative/analgesic drugs. Scoring systems for sedation are widely used (see later). It is increasingly standard practice to perform daily sedation holds unless contraindicated (e.g. raised ICP after traumatic brain injury). Make a note of evidence of focal neurological deficits, seizures, or weakness and whether there are purposeful symmetrical movements to verbal command or painful stimulus. Specialist monitoring may be used to measure ICP and cerebral perfusion pressure (CPP).

Gastrointestinal tract

Examination of the abdomen will reveal whether it is soft, tender or distended. The absence of bowel sounds may be misleading in a patient who is sedated and undergoing artificial ventilation; bowel activity is better ascertained from the observation chart. It should be noted whether the patient is being fed enterally or parenterally. If enteral feeding is being provided, note whether the patient is absorbing the feed and whether any prokinetic drugs are required; stress ulcer prophylaxis is routine. Other information gained from examination may include recent surgical activity, the function of stomas, appearance of wounds and contents of abdominal drains.

Renal system

The important features are urine output, current and cumulative fluid balance and abnormalities of serum electrolytes or acid–base balance. The patient may be receiving renal replacement therapy, so make sure catheters and anticoagulation are adequate.

Limbs/skin and wounds

Look for evidence of adequate perfusion (ensure documentation of primary and secondary surveys after trauma), presence of peripheral pulses, adequate capillary refill and evidence of swelling, tenderness, DVT or compartment syndrome. Surgical wounds and trauma sites should be inspected for adequate healing or infection.

Catheters and infection

All invasive catheters and tubing should be inspected for signs of local exit site infection; their duration should be noted as well as review of their ongoing requirement. Evidence suggesting catheter-related sepsis should prompt removal of lines and culture, but they should not be routinely replaced as a method of preventing infection. Note the patient's temperature with changes over time and check against markers of infection such as pulse, white cell count (WCC), C-reactive protein (CRP) and procalcitonin.

Investigations/interventions

Many units use a standard pro forma for admission documentation and other algorithms or protocols to encourage consistent high standards of clinical care. Prescription charts, laboratory results (haematology, biochemistry and microbiology), radiological images, and other investigations should be reviewed daily, making particular note of antibiotic requirements and appropriateness of stress ulcer and venous thromboembolism (VTE) prophylaxis.

Management plans

Finally a management action plan needs to be formulated, with special regard to pre-existing, active and ongoing problems. A plan for each organ system requiring support should be put into place as well as for ventilation and/or weaning. A review of nutrition, 24-h fluid balance and changes to drug therapy should also be undertaken and any planned procedures or interventions should be discussed. Communicate back any change in plans to the relevant nursing staff and bear in mind that relatives appreciate honest, up-to-date progress reports. It is important to note that patient confidentiality should never be compromised via discussion or documentation. Full assessment and examination should be repeated at least daily even in stable patients, because the physiological state of critically ill patients can change rapidly.

Transfers

Patients require intra- or interhospital transfers for a variety of reasons, including investigations (e.g. radiological imaging), treatment, provision of specialised services (e.g. transfer to major trauma centre), lack of ICU bed capacity or repatriation. Though usually accomplished safely, any transfer involves risks; the decision should be made by a senior clinician, planned carefully, and the patient's condition stabilised as far as possible beforehand ( Box 48.2 ). Local protocols should be instituted and followed. At least two experienced, competent attendants should accompany the patient; for level 2 and 3 critically ill patients this should involve an anaesthetist or intensivist competent in airway management and resuscitation. Meticulous preparation is needed, including communication with the receiving unit. Vital drugs, monitoring and equipment should be available. An oxygen supply, venous access, monitoring with power backup, emergency drugs, tracheal intubation equipment and the necessary infusions/pumps should be available.

Box 48.2
Adapted from the Intensive Care Society. (2011) Guidelines for the transport of the critically ill adult, 3rd ed. London, Intensive Care Society.
Pretransfer checklist to ensure the patient is stable enough for transport

Airway

  • Airway safe or secured by tracheal intubation

  • Tracheal tube position confirmed on chest radiograph

Ventilation

  • Adequate spontaneous respiration or ventilation established on transport ventilator

  • Adequate gas exchange confirmed by arterial blood gases

  • Sedated and paralysed as appropriate

Circulation

  • Heart rate and blood pressure optimised

  • Tissue and organ perfusion adequate

  • Any obvious blood loss controlled

  • Circulating blood volume restored

  • Haemoglobin adequate

  • Minimum of two routes of venous access

  • Arterial catheter and central venous access if appropriate

Neurological

  • Seizures controlled, metabolic causes excluded

  • Raised intracranial pressure appropriately managed

Trauma

  • Cervical spine protected

  • Pneumothoraces drained

  • Intrathoracic and intra-abdominal bleeding controlled

  • Intra-abdominal injuries adequately investigated and appropriately managed

  • Long bone/pelvic fractures stabilised

Metabolic

  • Blood glucose > 4 mmol L –1

  • Potassium < 6 mmol L –1

  • Ionised calcium > 1 mmol L –1

  • Acid–base balance acceptable

  • Temperature maintained

Monitoring

  • ECG

  • Blood pressure

  • Oxygen saturation

  • End-tidal carbon dioxide

  • Temperature

Monitoring in ICU

Patients in ICU are monitored continuously using a variety of invasive and non-invasive techniques ( Table 48.2 ). It is important to know that all equipment is working, accurate and calibrated correctly, and device monitoring is used for this purpose (see Chapter 17 ). The following sections describe the monitors that are used predominantly in the ICU; other monitors used during anaesthesia are discussed in Chapter 17 .

Table 48.2
Minimum and additional monitoring in critically ill patients
Monitor Comments
Minimum Basic monitoring for all patients
ECG, pulse rate, S p o 2 , arterial pressure, urine output, temperature
Fluid input/output

  • All inputs and outputs including calculation of overall fluid balance (minimum 24-hourly)

Drug infusions

  • Drug type, concentrations, infusion rates, volumes

Conscious level

  • Sedation score routine; other assessment of conscious level (e.g. GCS, CAM-ICU) where indicated

Additional (level 2/3)
Cardiovascular

  • Invasive arterial monitoring

    • Arterial pressure, adequacy of oxygenation ( P a o 2 , S a o 2 ), ventilation ( P a co 2 ) pH, acid–base abnormalities, lactate, cardiac output using pulse-contour analysis

  • CVC

    • CVP, infusion of vasoactive or irritant drugs; S cvo 2 , arteriovenous P co 2 difference, cardiac output (e.g. lithium dilution techniques)

  • Cardiac output

  • Pulmonary artery catheter

Neurological

  • GCS, CAM-ICU or other

  • CSF drainage

  • Processed EEG/CFAM

  • ICP

  • JVS

Respiratory and ventilator function

  • Airway pressures, lung volumes (often via the ventilator)

    • Lung compliance, resistance, gas trapping, intrinsic PEEP

  • Capnography

    • Confirmation of tracheal tube position, ventilation, gas flow patterns

  • Arterial plethysmography

  • Tracheal tube cuff pressure

  • Oesophageal pressure

Gastrointestinal

  • Input/output for enteral feed and aspirates, bowel output and stool chart

  • Intra-abdominal pressure

Additional fluid input/output

  • All outputs from external stomas or drains

  • Inputs and outputs

Haematological

  • FBC, laboratory or near-patient coagulation tests (e.g. TEG or ROTEM)

CAM-ICU, Confusion assessment method for ICU; CFAM, cerebral function analysis monitor; GCS, Glasgow Coma Scale score; JVS, jugular venous saturation; TEG, thromboelastograph; ROTEM, rotational thromboelastometry.

Arterial pressure

Arterial cannulation allows continuous measurement of arterial blood pressure, serial blood gas and other sampling. Significant respiratory variation in the amplitude of the arterial pressure wave (‘respiratory swing’) is characteristic of hypovolaemia. This pulse pressure variability (which relates to stroke volume variability caused by changes in venous return) can be formally measured by modern monitoring systems and is described as a percentage. Abnormal arterial waveforms can be seen in hyperdynamic circulations and conditions such as aortic stenosis, aortic regurgitation and left ventricular failure. Normal waveforms give an indication of cardiac output, myocardial contractility and outflow resistance.

Echocardiography

Echocardiography is emerging as a very useful tool in the critically ill, especially in the assessment of haemodynamics and response to therapeutic interventions; however, this often can prove challenging. Focused echocardiography is used to answer specific clinical questions as an extension to the clinical examination (e.g. to assess myocardial activity, filling or the presence of a pericardial collection). There are a number of systematic approaches to echocardiography that can be employed, depending on the skill and experience of the operator. It is likely that the use of echocardiography in critical care will increase in the future.

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