Chapter 6: Pre-ICU Syndromes

Rapid Response Teams

The Joint Commission's National Patient Safety Goals, directs health care providers to improve the identification of clinical deterioration in hospitalized patients and select “a suitable method that enables health care staff members to directly request additional assistance from a specially trained individual(s) when the patient's condition appears to be worsening.”¹

Rapid response systems are designed to address this goal and RRTs or METs have become increasingly prevalent in the US hospital systems as the means to intervene in the care of hospitalized patients with acute clinical deterioration.^2,3 RRTs are called to evaluate and treat not only the patients who had a cardiorespiratory arrest (for which traditional code teams exist), but also to assess patients who are having symptoms indicative of an impending cardiorespiratory or neurologic deterioration, thus supplementing traditional code teams in scope and frequency of response.^2,3,4,5 RRTs may be called for signs of clinical deterioration, such as vital sign abnormalities, arrhythmias, dyspnea, and altered consciousness. A demand on the limited number of intensive care unit (ICU) beds requires more acute and complex patient care to be delivered on the general wards, outside of the ICU.⁶

Rapid Response Activation

The RRT team is activated in instances of perceived patient deterioration and recognition of clinical deterioration. RRT calls are most commonly prompted by cardiorespiratory and neurologic symptoms identified by hospital staff (clinical and nonclinical) or even family members.

The identification of prearrest physiology such as abnormal vital signs, or a sudden change in vital signs, can help identify clinical deterioration minutes to hours before a serious adverse event, often providing sufficient time to deliver an intervention.^7,8,9 Indeed, diurnal variation of RRT activation rates generally correlate with the timing of caregiver visits.¹⁰ Delays in provider notification and failure to seek help in a timely manner by ward personnel can also contribute to suboptimal outcomes and increased mortality even when RRT systems are in place.^11,12 Providing objective criteria as a guide for the activation of RRT improves utilization of the RRT systems.

Studies have searched for the minimal criteria for RRT activation. Universally, vital signs monitoring and evaluation of mental status is reproducible and effective.¹³ Trigger systems that rely on these parameters alone are known as single and multiple parameter systems based on the number of physiologic criteria included (Figure 6–1). Continuous vital sign monitoring is not feasible for non-ICU patients; so the optimal frequency of vital sign monitoring is patient dependent and difficult to generalize to all patient populations.¹⁴

In a review of current early warning systems for recognizing and responding to clinically deteriorating patients, relevant policies were examined to determine the vital sign parameters and trigger thresholds that activate RRT. Most hospitals scored respiratory rate, heart rate, systolic blood pressure, and consciousness level as triggers, and some additionally scored urine output, oxygen saturation, and need for oxygen administration. The thresholds for classifying the values as abnormal varied between the hospitals and were chosen seemingly arbitrarily based on local preferences and expertise.¹⁵ A study of 400 rapid response calls at a large Australian teaching hospital found the most common reasons for RRT activation to be hypoxia (41%), hypotension (28%), altered consciousness (23%), tachycardia (19%), increased respiratory rate (14%), and oliguria (8%). Infection, pulmonary edema, and arrhythmias featured prominently as underlying morbidities and were thought to be responsible for 53% of all triggers for RRT calls.¹⁶

Traditional ICU scoring systems, such as the sequential organ failure assessment (SOFA) score or the multiple organ dysfunction score (MODS) which are used to predict ICU mortality have been adopted by some institutions as markers for clinical deterioration of non-ICU patients.

The National Early Warning Score Design and Implementation Group (NEWSDIG) in the United Kingdom developed the VitalPac Early Warning Score (ViEWS), a validated scoring system for the early detection of clinical deterioration and prediction for cardiac arrest or need for ICU transfer. The aggregate weighted system scores physiologic parameters to determine the need for more frequent monitoring or ICU-level care. The parameters include respiratory rate, oxygen saturation, supplemental oxygen use, temperature, systolic blood pressure, heart rate, and level of consciousness. Higher scores indicate the need for more frequent reassessment and higher level of care (Figure 6–2A, B, C). Similar scoring systems such as the cardiac arrest risk triage (CART) have been developed using logistic regression. The CART score has been validated for in-hospital cardiac arrest (AUC 0.84) and the need for ICU transfer (AUC 0.71).¹⁷ Over 100 track and trigger systems have been developed in recent years, making it extremely difficult to accurately compare and validate them with each other.

More recently, prediction models using vital sign, demographic, location, and laboratory data in electronic health records have been developed as early warning systems for adverse outcomes on the wards. The models are able to calculate a risk score based on computerized data to alert caregivers with automated, real-time, information regarding patient deterioration. Compared to manually calculated systems, automated systems are the least error prone to calculation errors and are the least labor intensive. Although potentially quite useful, these automated scoring systems should not be regarded as the sole solution for detecting patient deterioration; the systems are highly sensitive and may overestimate clinical deterioration or need for higher level of care. Rather, their use could be an adjunct to alert staff to the need to further clinically assesses patients.¹⁸

A large systematic review demonstrated that implementation of single parameter triggering systems alone are unlikely to improve hospital survival, and that there was only weak evidence in the reduction of cardiac arrest. In contrast, aggregate weighted scoring systems improved hospital survival and reduced both unexpected ICU admission and cardiac arrest rates.¹⁹

Outcomes

Typical call rates are 20 to 40 per 1000 admissions and the in-hospital mortality of such patients is 24% to 34%.^3,20 Although the MERIT study, a multicenter, cluster-randomized, controlled trial of RRT systems failed to demonstrate that implementation of RRTs led to a decrease in cardiac arrests, ICU admissions, or unexpected deaths;²¹ post hoc analysis showed a significant improvement in outcomes when the data were analyzed in an as-treated model rather than an intention-to-treat model.²² Further single-center trials also point to improved outcomes in hospitals that implemented RRTs.²⁰ A meta-analysis of 18 studies reviewing the effectiveness of RRT systems in acute care settings demonstrated that the implementation of RRTs is associated with reduced rates of cardiorespiratory arrests outside of the ICU with relative risk reduction of 33%.²³ In addition, a retrospective study of nearly 6 million admissions over a 10-year period showed the presence of a hospital RRT system for more than 2 years was associated with 0.14% absolute risk reduction of in-hospital mortality across a major metropolitan health network, which translated to 56 lives saved per year in a hospital with 40,000 admissions per year.²⁴ Mortality benefits after the introduction of RRTs are not always immediate and may take time to become apparent.

In general, triage decisions based on rapid response evaluation regarding transfer of patients to the ICU or general ward care seem to be appropriate. In a large study, 12.7% of patients that had RRT activation required repeat RRT activation and of those around 80% were transferred to the ICU. A total of 0.4% died within 24 hours of the index RRT activation, with half of the mortalities occurring as unexpected cardiac arrests on the wards, while the other half occurred in the setting of ICU care, or palliative care, after the repeat RRT call.²⁵

Inappropriate triage and disposition of unrecognized critical illness at the time of initial admission are contributing factors to unfavorable patient outcomes. Indeed, RRTs occurring early in hospitalizations (hospital days 0 and 1) constitute approximately 27% of all calls and partially reflect suboptimal triage decisions.¹⁰

Team Composition

The composition of the RRT can vary significantly based on the hospital system and available resources.²⁶ Teams are often comprised of multidisciplinary staff that may include critical care medicine fellows or attendings, internal medicine housestaff or hospitalists, respiratory therapists, physician assistants, nurse practitioners or an ICU nurse. Studies evaluating ideal team composition are sparse.²⁷ It is difficult to assess the optimal team composition and subsequent outcomes due to the amount of variation that exists. While it has been shown that response teams led by attending intensivists and senior medical residents had similar outcomes, teams led by nurses alone had equivocal outcomes.¹⁹

The Society of Critical Care Medicine has identified the five primary ICU admission diagnoses as: respiratory system diagnosis with ventilator support, acute myocardial infarction, intracranial hemorrhage or cerebral infarction, percutaneous cardiovascular procedure with drug-eluting stent, and septicemia or severe sepsis. Additional diagnoses that often require ICU admission include: toxins, heart failure, arrhythmias, renal failure, and gastroinestinal hemorrhage.²⁸ The correlating rapid response triggers for these conditions are often identified as hypotension, altered mental status, and respiratory distress.

Hypotension and Shock

Hypotension is not defined by a fixed number, but often precedes or is the manifestation of shock. Classically shock has been divided into four categories: hypovolemic, obstructive, cardiogenic, and distributive.²⁹ Hypovolemic shock is explained by hemorrhage or fluid losses. Obstructive shock indicates a structural impediment to the circulatory apparatus as seen with pericardial tamponade, tension pneumothorax, or pulmonary embolism. Cardiogenic shock occurs secondary to valvular dysfunction, arrhythmia, or ventricular compromise. Distributive shock is often a marker of an inflammatory process disrupting the integrity of small vessels that can be seen in sepsis or anaphylaxis. The classification may be overly simplistic as septic patients in distributive shock may also present with relative hypovolemia and cardiomyopathy contributing to their shock state. Still, the classification provides a useful framework through which to approach a difficult problem.

Shock is the clinical diagnosis that represents the imbalance between oxygen delivery and demand. Physiologically it is based on the principle of oxygen delivery to end organs, accomplished by adequate circulating blood volume and red blood cells, vascular tone, and cardiac function. These physiologic principles are the backbone for the early goal-directed therapy in the treatment of severe sepsis and septic shock.³⁰ Clinical signs of end-organ damage such as decreased urine output and encephalopathy as well as biomarkers (increased lactate, creatinine, troponins, and liver enzymes) are indicative of hypoperfusion and shock.

Altered Mental Status and Neurologic Deterioration

Altered mental status is a broad term encompassing a spectrum of alterations of an individual's normal mental facilities. The differential diagnosis of altered mental status can be more succinctly divided into four categories: primary intracranial processes, systemic or metabolic diseases secondarily affecting the central nervous system, exogenous toxins, and drug withdrawal.³¹ Differential diagnosis may be difficult upon initial evaluation. Focal neurologic symptoms often indicate an intracranial process such as a stroke or seizure. Encephalopathy and delirium are more often associated with systemic illness, toxins, and withdrawal. Furthermore, toxidromes have been described with specific drug exposures and poisonings.

Deterioration in mental status can be measured serially with the Glasgow Coma Scale (GCS). A GCS of 8 or less is associated with the inability to protect one's airway and the risk of aspiration, prompting emergent transfer to a monitored setting, or intubation.³²

Respiratory Distress and Failure

Acute respiratory failure and the need for mechanical ventilation are among the most common causes of ICU admission. The cause for respiratory failure can be of a primary pulmonary pathology or secondary to cardiac, infectious, metabolic, neurologic, and overall systemic illness. An increased work of breathing, low oxygen saturation, or depressed respiratory status should all prompt an ICU evaluation as such patients rapidly deteriorate into cardiopulmonary collapse. Pulse oximetry and blood gases are readily available and can be repeated serially to determine the degree of oxygenation and ventilation deficit. When appropriate, the need for mechanical ventilation should not be delayed. In select cases, such as exacerbation of heart failure or obstructive pulmonary disease, a trial of noninvasive positive pressure ventilation (NIPPV) while implementing targeted therapies has been shown to be effective and may alleviate the need for mechanical ventilation.³³

Implementation of RRT is meant for the early identification of pre-ICU syndromes and prevention of cardiac arrests. While the causes for shock, neurologic deterioration, or respiratory failure may not be initially evident, the “Hs and Ts” (Table 6–1), described in Advanced Cardiac Life Support guidelines, provide a framework for diagnostics and treatment. They are major contributing factors to developing cardiac arrest that can be identified and potentially treated at the bedside, before transfer to the ICU. The rapid identification of these factors helps guide therapy in the crucial moments leading up to a cardiac arrest. These findings are present, or are the presenting symptoms, in many patients requiring ICU-level care.

First steps when evaluating the critically ill patient include cardiac monitoring, vital signs, pulse oximetry, and establishing intravenous access. The advanced cardiac life support and advanced trauma life support algorithms have popularized an “ABCD” approach to critically ill patients: irway, breathing, circulation, and neurological disability and differential diagnosis (Table 6–2).³⁴ A rapid primary survey evaluating for and intervening upon life-threatening conditions is a fundamental underpinning of effective resuscitation and is a useful model to follow in critical care. Clinically experienced physicians will proceed in an order dictated by their experience—often delegating tasks to team members. For the less experienced physician the framework is a reminder of the critical elements that must be assessed and intervened upon with immediacy.

Equipment and Medications

Equipment and medications are limited on general wards. When responding to a rapid response, the appropriate equipment should be brought to the bedside. The following are examples of equipment and medications that supplement standard intubation supplies and cardiac arrest medications required for the ACLS algorithm.

• Airway/equipment bag: The contents of the bag should include equipment for intubation of the difficult airway. This includes laryngeal mask airways, a bougie or endotracheal tube introducer, video laryngoscopes, peep valves, and a cricothyroidotomy kit. The addition of an intraosseous infusion kit allows for rapid circulatory access when appropriate intravenous access is lacking.

• Medication bag: The contents of the bag should include medications for appropriate induction of anesthesia prior to intubation and blood pressure support. This includes propofol, etomidate, short-acting paralytics and vasoactive medications such as phenylephrine or norepinephrine.

• Portable ultrasound: Goal-directed ultrasonography during a rapid response assists in formulating a diagnosis, focusing therapy, and guiding procedures without having to transport critically ill patients to imaging suites.

The medications and equipment listed above are used as an example. Local hospital practice, protocols, equipment availability, and expertise should dictate the contents of RRT equipment.

Postoperative, Postprocedure, and Specialized Care

Often admissions to the ICU are not related to the above-described, unexpected, syndromes. Rather, they are admissions that require postoperative, postprocedural, or specialized care. These are planned or protocoled admissions that are based on local hospital policy and procedure and the need for additional monitoring. Specialized units include, but are not limited to, surgical, cardiothoracic, neurologic, neurosurgical, burn, trauma, respiratory, and cardiac units. Unplanned, or unexpected, postoperative or postprocedural admissions are often related to the previously described syndromes.

The majority of ICU admissions can be characterized by the presence of respiratory failure, a shock state, neurologic deterioration, or a combination of the three. While often times the need for ICU care is evident on initial presentation to the hospital, it is not always possible to predict the need. Pre-ICU syndromes develop rapidly, unexpectedly, and have the potential for detrimental outcomes. It is imperative to have functional rapid response systems, in terms of both triggering and response, to expedite care to such patients in a ward setting.