Background to ICU
Intensive care revision for medical students finals, PLAB exams and MRCP PACES
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- Help familiarise the reader with what care intensivists can offer
- Help familiarise the reader with what care intensivists cannot offer
- Help the reader recognise those patients that require intensive care input and recognise those where it may be inappropriate
- Help the reader to understand the medical jargon associated with intensive care
- Help the reader improve their understanding of ICU so the referral process is much smoother
Modern ICUs originated in the 1950s in the midst of the polio epidemic. At this time young patients with polio who had tracheal intubation and positive pressure ventilation had an improved survival outcome. From this point ICU evolved as a separate and specialist area of the hospital.
The Intensive Care Society defines Intensive Care Units (ICUs) as: “Areas of the hospital that look after patients whose conditions are life threatening and need constant, close monitoring and support from equipment and medication to keep normal body functions going”.
ICUs have specialist equipment to assist with organ support and higher staffing levels to care for patients. These staff also have specialist training.
Patients will be admitted to ICU from all over the hospital: from the emergency department, direct from theatre, medical wards and obstetrics. Admissions may be planned i.e. after surgery, or emergency i.e. a critically unwell medical patient not responding to therapy. Unlike in the 1950s, when patients in ICUs were young and previously fit, patients now tend to be older and suffer multiple comorbidities.
Intensivists aim to identify the pathophysiological changes critical illness causes and the effect these have on the body’s organ systems. By recognising and treating these patterns the aim is to improve the outcome for critically ill patients.
ICUs manage a variety of problems. Common conditions requiring ICU care are:
- Critical illness causing failure of one or more body systems
- Sepsis of any source: Uncontrolled infection causing organ dysfunction is the commonest cause of admission to ICU.
- Post-operative or surgical complications
- Diabetic ketoacidosis and HHS
The role of ICU in these conditions falls into five main areas:
- Resuscitation and stabilisation
- Physiological optimisation of patients to prevent organ failure
- Facilitation of complex surgery
- Support of failing organ systems
- Recognition of futility
It is important as a doctor that you recognise critically unwell patients and the level of care that they require. You can then have a coherent conversation about this with your senior colleagues or ICU colleagues. Levels of care are 0,1,2,&3. The following definitions will assist you in classifying care needs. By using these definitions you can also ensure that nursing staff and bed managers are aware of the care that is needed and this will ensure inappropriate transfers do not occur.
Level 0: patients whose needs can be met on a normal ward
Level 1: patients at risk of their condition deteriorating, where higher care is needed but can usually be met in a monitored area of a normal ward. Critical care input may be needed e.g. with ITU outreach support
Level 2: Patients requiring a more detailed level of care, they may have single organ dysfunction, require post-operative care or require intense levels of nursing care. Level 2 care normally refers to high dependency units
Level 3: Patients requiring advanced respiratory support alone or basic respiratory support with more than one organ failing. The care needs of these patients are usually complex. Level 3 care refers to intensive care units.
Whilst ICUs can offer organ support and treatment for reversible illnesses and they can allow support whilst a diagnosis is sought and then treated, they cannot treat irreversible conditions. Even with reversible illnesses the outcome may still not be favourable. A stay in intensive care not only puts physiological stress on the body but also psychological stress. There are also risks of further complications whilst a patient is in ICU such as ventilator acquired pneumonias, line infections and sepsis from multi-resistant organisms. It is therefore imperative that as a referring doctor you assess whether your patient is appropriate for level 2 or 3 care before making a referral. Doing this will also aid your referral as it will be one of the first things an intensivists will ask.
Deciding whether a patient is appropriate for ICU care is a complex decision and should be made with the support of senior colleagues, nursing staff, the patients family and the patient themselves. If there is doubt about a patient’s suitability for admission to ICU, seeking advice from an intensivist is also appropriate. Some patients may have clear wishes and advanced directives. These should always be respected. If no clear decisions have been made previously and the patient is able to discuss their care this should be your first port of call to clarify their wishes. If the patient is not competent to have this discussion then the next of kin should be spoken to. However, ultimately the decision for resuscitation and ICU admission is the decision of the consultant caring for the patient. In addition, just because a patient has a DNAR does not mean they are inappropriate for level 2 care. Patients may not be appropriate for ICU care if:
- They have clear wishes to receive ward based care only
- They have no clear reversible cause for their illness
- They have multiple co-morbidities, frailty or advanced age that combined make it unlikely that they will survive an ICU stay (age alone should not be a discriminating factor)
- The medical team feel that the physiological and psychological stress of ICU is unlikely to be in the patient’s best interest
Setting ceilings of care can be complex and an ethical minefield, it is important that the multidisciplinary team (MDT) and next of kin are kept updated and all decisions are thoroughly discussed.
There are scoring systems available to try and predict the outcome of an ICU stay which can be implemented when making a decision as to whether a patient is suitable for higher level care. However there are flaws in these systems. Though they are based on large data sets and may accurately predict population outcomes, they are unreliable in predicting outcomes on an individual basis. In addition, the scoring systems do not necessarily encompass the outcome after ICU discharge; even if a patient is discharged to a ward there is still significant mortality risk.
One of the commonest scoring tools used is the APACHE II score (acute physiological and chronic health evaluation). The score is based on the worst physiological derangement in the first 24 hours (A), age (B) and chronic health. A score of greater than 35 indicates that the patient is unlikely to survive. There are some caveats to this e.g. a patient with severe DKA may score very highly but with appropriate therapy they do tend to reverse very quickly. This score is also based on population data and may not be accurate on an individual basis.
- The APACHE II comprises:
- Chronic organ failure or immunocompromise
- Acute renal failure
- Mean arterial pressure (MAP)
- Heart rate
- Resp rate
- Lab data
- A-a gradient (if FiO2>0.5) or PaO2 (if FiO2<0.5)
The following link will take you to the apache score: www.mdcalc.com/apache-ii-score-for-icu-mortality/
There are other scoring systems available, these are APACHE 3 score, SAPS (Simplified Acute Physiology Score), TISS (Therapeutic Intervention Scoring System) and SOFA score (The Sequential Organ Failure Assessment Score).
It is important that patients who are clinically deteriorating are identified, so that interventions can be put in place to avoid unnecessary escalation of care, peri-arrest or arrest situations.
In 2012 the Royal College of Physicians (RCP) worked in conjunction with the Royal College of Nurses (RCN) and now advocates that the National Early Warning Score (NEWS) is used across the NHS. This scoring system is based on six physiological parameters: respiratory rate, oxygen saturations, temperature, systolic blood pressure, pulse rate and level of consciousness. The patient is scored depending on their parameters and this can trigger a low, medium or high response. The RCP advocates that NEWS is used in all acute care areas to assess and monitor patients but it should not replace clinical judgement. Doctors are expected to respond in a timely way and conduct an appropriate assessment if they are called to a patient with a high NEWS score. This assessment should follow a structured ABCDE approach as advised by the Resuscitation Council in ALS guidelines. The Resuscitation Council have identified that many hospital peri-arrests or arrests may be preventable if the deterioration is detected.
In addition to the NEWS triggering nursing staff to call a doctor for assistance, in many trusts a high NEWS score will also prompt the intensive care outreach team to be called. The ICU outreach team are usually senior ICU nursing staff or physiotherapists who provide several invaluable roles. They can provide a liaison with ICU, they can help support the care of patients requiring level 1 care on the wards, they can assess and instigate interventions of at risk patients with high NEWS and they can promote education on the wards. As a junior doctor, working with the outreach team is incredibly valuable as not only can they offer their expertise but they can also help facilitate and expedite ICU admission if necessary. The outreach team will also support the intensivists if they need to commence level 2 or 3 care on the ward, in order to stabilise a patient prior to transfer to ICU. In addition with outreach assistance and intervention you may also be able to prevent some ICU admissions.
An important key point to remember is that if you are caring for a deteriorating patient, do not leave calling ICU until the last minute. If they are called early they may be able to offer some help and advice which may delay or prevent ICU admission. The outreach team will also be able to assist with this. As a junior doctor if you are struggling with a critically unwell patient you should always seek help early from the medical SpR, the ICU SpR and outreach.
Another key point is to have a baseline knowledge of what ICU can offer in terms of care, this will mean that when you call for help you will know what you are asking for. The following sections should aid you with this point.