Definition and objectives of an intensive care unit
The intensive care unit (ICU) is a distinct organizational and geographic entity for clinical activity and care, operating in cooperation with other departments integrated in a hospital. The ICU is preferably an independent unit or department that functions as a closed unit under the full medical responsibility of the ICU staff in close concert with the referring medical specialists [2, 3]. It has a defined geographical location concentrating the human and technical resources, such as manpower, professional skills and competencies, technical equipment, and the necessary space. The characteristics of medical, nursing, and allied health personnel staffing; technical equipment; architecture; and functioning should be clearly defined [4–6]. Interdisciplinary written arrangements about workflow, competencies, medical standards, regulations of cooperation, and mechanisms for decision-making are helpful to embed competencies and to standardize clinical workflow.
The objectives of an ICU are the monitoring and support of threatened or failing vital functions in critically ill patients who have illnesses with the potential to endanger life, in order to perform adequate diagnostic measures and medical or surgical therapies to improve outcome. The patient population may present with a large variety of pathologies but shares the potential reversibility of one or more threatened vital functions. Every ICU should provide the know-how and equipment based on the mission statement of the individual ICU to assure “state-of-the-art intensive care medicine.”
Timely mobilization of the ICU team and its support services plays an important role in the efficient use of acute care facilities, for the coverage, triage, and outreach management of critically ill patients outside the ICU. Shared protocols between the ICU and other departments of the hospital (e.g., the emergency department) enhance throughput and decrease overall hospital mortality of critically ill patients .
These proposed guidelines are valid for ICUs caring for adult patients. Neonatal/pediatric ICUs may have to be adapted accordingly. Specific pediatric units are desirable if the turnover rate justifies such a unit and warrants expertise. Whenever possible pediatric patients should be treated in specialized pediatric ICUs .
An ICU will be situated in a hospital with appropriate departments to ensure that the multidisciplinary needs of intensive care medicine are met [9–11]. Surgical and medical diagnostic and therapeutic facilities must be represented, and medical, anesthesiological, surgical, and radiological consultants must be available for ICU purposes on a 24 h/day basis. Not all hospitals will develop their ICU facilities in the same way, with the same competencies and identical structures and equipment. ICUs must be adapted to the region and the hospital they serve in terms of size, staffing, and technology.
An ICU should accommodate as a minimum at least 6 beds [12, 13], with 8–12 beds considered as the optimum. Hospitals with several smaller units should be encouraged to rearrange these units into a single larger department to improve efficiency. On the other hand, a larger ICU may take the opportunity to create separate, specialized functional subunits with 6–8 beds, sharing the same geographical, administrative, and other facilities. Cohorting of patients in such subunits may be based on specific processes of care or pathology. The size of the unit is also influenced by the geographical and economic situation. A volume-effect in terms of sufficient numbers of admitted patients and numbers of therapeutic interventions is also recognized to maintain the quality of activities such as the provision of mechanical ventilation and renal replacement therapy [14–16].
Director of the intensive care unit
The responsibility for the administrative and medical management of the unit is held by a physician, whose professional activities are devoted full-time or at least 75% of the time to intensive care, who holds the position of director of the ICU. The head of the ICU has the sole administrative and medical responsibility for this unit and cannot hold top-level responsibilities in other departments or facilities of the hospital. The head of the ICU should be a senior accredited specialist in intensive care medicine as defined at country level, usually with a prior degree in anesthesiology, internal medicine, or surgery and have had a formal education, training, and experience in intensive care medicine as described by the ESICM guidelines .
Medical staff members
The head of the ICU is assisted by physicians qualified in intensive care medicine. The number of staff required will be calculated according to the number of beds in the unit, number of shifts per day, desired occupancy rate, extra manpower for holidays and illness, number of days each professional is working per week, and the level of care and as a function of clinical, research, and teaching workload. Extended work shifts have been shown to negatively impact the safety of patients as well as medical staff [18–20]. The number of full time equivalent (FTE) physicians qualified in intensive care medicine per six to eight intensive care beds (at level of care II, see section “Activity Criteria”) can be calculated (according to the European working hours directives) with the formula provided in paragraph 9 of the ESM . An experienced physician certified in intensive care medicine is on duty and available upon request at short notice in the hospital during “off duty hours.” The regular medical staff members of the ICU treat patients using state-of-the-art techniques and may consult specialists in different medical, surgical, or diagnostic disciplines whenever necessary.
The regular medical staff members have the task of coordinating the referring physician and consulting medical specialties. The staff members of the ICU take over the medical and administrative responsibilities of the care of the patients admitted to the unit. They define admission and discharge criteria and carry the responsibility for diagnostic and therapeutic protocols to standardize care in the ICU. An important task of the medical staff in training centers is to supervise and teach the doctors in training. For this purpose formal daily rounds are organized to give information and plan therapy. All ICU health professionals involved in direct patient care should participate in these rounds.
Trainees in medical and surgical specialties (e.g., anesthesiology, internal medicine, pulmonology, surgery) may, after 2 years of training in their primary specialty and within the frame of their specialty, work in an ICU under clearly defined supervision. Depending on the legal framework operating in the individual country, these training periods should have a minimum duration of 6 months (optimally 1 year) for those planning to qualify in intensive care medicine and 3 months (optimally 6 months) for others. During these training periods, the trainees are involved full-time in the activities of the ICU.
Trainees assure supervised continuity and participate in the duties of the ICU under the supervision of a qualified intensive care physician. The regular staff carries final medical responsibility. Under ideal conditions, there should be an overlapping in the training periods to reinforce the expertise in the group of trainees.
Continuity of medical activity
The continuity of medical care in the ICU during nights, weekends, and holidays is assured by the regular medical staff of the ICU on a 24 h/day basis [22–24]. They can be assisted by skilled and experienced residents from other departments with basic training in intensive care medicine, provided there is a back-up of the regular staff around the clock [25–28]. This activity needs to be considered in the calculation of requested regular staff.
Organization and responsibilities
Intensive care medicine is the result of close cooperation among doctors, nurses, and allied health care professionals (AHCP). An efficient process of communication has to be organized between the medical and nursing staff of the ICU. Tasks and responsibilities have to be clearly defined.
The nursing staff is managed by a dedicated, full-time head nurse, who is responsible for the functioning and quality of the nursing care. The head nurse should have extensive experience in intensive care nursing and should be supported by at least one deputy head nurse able to replace him (her). The head nurse should ensure the continuing education of the nursing staff. Head nurses and deputy head nurses should not normally be expected to participate in routine nursing activities. The head nurse works in collaboration with the medical director, and together they provide policies and protocols, and directives and support to the team.
Intensive care nurses are registered nursing personnel, formally trained in intensive care medicine and emergency medicine. A specific program should be available to assure a minimum of competencies amongst the nursing staff [29, 30]. An experienced nurse (head nurse or a dedicated nurse) is in charge of education and evaluation of the competencies of the nurses. In the near future, a specific curriculum for ICU nurses should be available. In addition to clinical expertise, some nurses may develop specific skills (e.g., human resource management, equipment, research, teaching new nurses) and assume the responsibility for this aspect of unit management.
Staff meetings together with physicians, nurses, and AHCP must be regularly organized in order to carry out the following:
Discuss difficult cases and address ethical issues
Present new equipment
Share information and discuss organization of the ICU
Provide continuous education
The number of intensive care nurses necessary to provide appropriate care and observation is calculated according to the levels of care (LOCs) in the ICU [31–44]. For the description of the LOCs refer to the section “Activity criteria.”
Nurses in training
Nurses in specialty training for intensive care and emergency nursing must be trained in ICUs under the supervision of sufficient training personnel. They should not be seen as substitute for regular intensive care nursing staff but may be gradually assigned to patient care according to their actual level of training.
Allied health care personnel 
One physiotherapist with dedicated training and expertise in critically ill patients should be available per five beds for level III care on a 7 day/week basis.
Maintenance, calibration, and repair of technical equipment in the ICU must to be organized. This facility can be shared with other departments of the hospital but a 24-h availability has to be organized with priority for the ICU.
Should be on call around the clock. Interpretation of the medical imaging by the radiologist must be available at all times.
Should be on call during normal working hours.
Speech and language therapist
Should be available to consult during normal working hours.
Should be available to consult during normal working hours.
Should be available to consult during normal working hours.
Should be available to consult during normal working hours. A sufficient collaboration with pharmacy is of particular importance with respect to patient safety.
One medical secretary is required per 12 intensive care beds. Basic tasks are patient administration, external and internal communication exchange, and typing of reports and documents. One secretary per six beds may be desirable if she/he is also involved in arranging laboratory journals and medical files. Another approach is to calculate the number of medical secretarial assistants as one FTE per 500–700 admissions. Support for formal teaching activities may increase the need.
A specialized group of cleaning personnel familiar with the ICU environment should be available for the ICU. They should be familiar with infection control, prevention protocols, and hazards of medical equipment. Cleaning and disinfection of the patient areas are performed under the nurse’s supervision. A checklist of the cleaning status must be kept. Regular updates should be provided to ensure cleaning protocols reflect best practice.
To assure optimal patient care, a complex and time-critical interplay among different groups of professionals, using a wide range of pharmacological interventions, treatments, and procedures, is needed. Accordingly, the workflow in the ICU is complex and dynamic, with many shared tasks and overlapping activities. Thus, well-structured collaboration among physicians, nurses, and all other professionals working in the ICU is essential.
This includes the following:
Presence of inter-professional clinical rounds 
Standardized and structured processes of handover and of interdisciplinary and interprofessional information transfer
Use of a clinical information system (patient data management system)
Finally, although beyond the scope of these recommendations, it needs to be mentioned that a growing body of literature indicates that management and climate in the ICU can influence the satisfaction of patient relatives, the well-being of health care workers, and might even have an impact on patient outcomes [9–11, 47, 48].
Definition of intensive care patients
Two types of patients are likely to benefit from admission to an ICU [40, 49–51]:
Patients requiring monitoring and treatment because one or more vital functions are threatened by an acute (or an acute on chronic) disease (e.g., sepsis, myocardial infarction, gastrointestinal haemorrhage) or by the sequelae of surgical or other intensive treatment (e.g., percutaneous interventions) leading to life-threatening conditions.
Patients already having failure of one of the vital functions such as cardiovascular, respiratory, renal, metabolic, or cerebral function but with a reasonable chance of a meaningful functional recovery. In principle patients in known end-stages of untreatable terminal diseases are not admitted. Sometimes the need for palliative care requiring intensive care measures may be considered.
In addition, patients with brain death or in whom brain death is expected to occur and in whom organ donation is considered may be admitted.
Definition of levels of care (LOCs)
Three LOCs are proposed: III, II, and I.
Level of care III (highest)
LOC III represents patients with multiple (two or more) acute vital organ failure of an immediate life-threatening character. These patients depend on pharmacological as well as device-related organ support such as hemodynamic support, respiratory assistance, or renal replacement therapy.
Level of care II
LOC II represents patients requiring monitoring and pharmacological and/or device-related support (e.g., hemodynamic support, respiratory assistance, renal replacement therapy) of only one acutely failing vital organ system with a life-threatening character.
Level of care I (lowest)
LOC I patients experience signs of organ dysfunction necessitating continuous monitoring and minor pharmacological or device-related support. These patients are at risk of developing one or more acute organ failures. Included are patients recovering from one or more acute vital organ failures but whose condition is too unstable or when the nursing workload is too high/complex to be managed on a regular ward.
For these different LOCs, the following minimum nurse/patient ratios are considered to be appropriate:
Nursing FTE per ICU bed
Several LOCs can be integrated into the same ICU in a flexible organization model . The nurse/patient ratios represent mean annual data and may need to be customized for each country [40, 49–51, 53]. The planned and operating nursing staff can be matched by using the Workload Utilization Ratio or similar instruments .
Hospital facilities may include a high dependency unit (HDU) that is characterized by the maximum provided LOC that does not exceed level I. The choice to organize a mixed ICU/HDU or rather to opt for two separate units (ICU and HDU) can be made bearing in mind the following considerations:
The bedside equipment has the least impact on ICU cost (in contrast to the salaries of personnel). In a mixed ICU/HDU all beds should be equipped to the highest level. Otherwise “internal” moves to adequately equipped beds will lead to problems described in point 2.
Moving patients between separate units or internally to adequately equipped beds carries certain risks including loss of information, hampers continuity in management, and creates an avoidable and unnecessary workload .
A mixed ICU/HDU unit necessitates additional creativity to use the available manpower as efficiently as possible. On days with concentrated high activity some fully equipped beds may remain empty. Capacity calculation should then be performed based on available manpower and workload rather than on number of equipped beds.
Required number of intensive care beds
The number of intensive care beds has to be calculated as a function of the type of the hospital, admission of specific disease categories, the geographic location of the hospital, number of acute beds, etc. A survey of the international literature shows figures in Europe of an average of 5% of hospital beds up to 10% in university hospitals. In the United States, the numbers are higher, but the cost-benefit of these ratios remains controversial. These numbers are indicative and depend also on the referral function of a hospital [12, 53, 56, 57].
Standards for architecture, medical and surgical staff and others have to be calculated for a 100% activity and occupancy rate. In practice, only 75% of the beds will be occupied if the occupancy rate is calculated on an hourly basis. This will allow the unit to cope with major emergencies and to avoid premature discharges.
Quality control encompasses a wide variety of activities and items needed to objectivate and explain the excellence of performance, and benchmark with peers. A list of respective criteria is provided in paragraph 2 of the ESM.
Each ICU should evaluate its activity, bearing in mind that a critical minimum amount for each disease category is necessary to maintain medical and nursing expertise at adequate levels [14–16, 22, 23]. In this process of self-evaluation, choices may have to be made regarding transfer of patients to regional/national centers of excellence experienced in a specific domain of intensive care medicine or for specific critical care disease categories.
Every ICU is required to have a quality assessment and improvement program in order to compare with a national/European benchmark. This should include a report of complications and adverse events, and a system in which indicators that reflect quality and safety of care are continuously monitored.
These indicators should cover the process of care (i.e., mechanical ventilation, sedation, medication, IV lines, management, or complications), outcome (i.e., risk-adjusted mortality), and structure (i.e., staffing adequacy, protocol availability, medication errors protocol) [58, 59]. Morbidity and mortality conferences are strongly recommended. It is beyond the scope of present recommendations to go into detail to determine which quality indicators are best suited for these purposes [60–62].
The participation in regional, national, or international data collection and comparison systems should be encouraged, in order to maximize the safety and quality culture of the ICU.
Management of equipment
Disposable material raises problems of storage and distribution because of its volume and turnover. A policy of frequent review of disposable material is absolutely fundamental for economic and quality purposes. A feature of intensive care medicine is that a very large number and variety of specific items must be kept within the unit. A small part can be stored at the bedside; the majority will be stored in the storage room. A simple system of stock control must be operated.
Criteria for the selection, purchasing, storage, servicing, sterilization, and replacement of durable equipment are provided in paragraph 3 of the ESM.