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Introduction   

Clinically low blood pressure, or hypotension, may be brought on by several different factors including dehydration, adverse effects of medication, shock, cardiac failure, hemorrhage, and sepsis. Persistent hypotension that does not respond to fluid resuscitation may be difficult to manage on a medical-surgical or progressive unit.  

For patients with challenging comorbidities, severely acute disease processes, or who do not respond to initial treatment, the intensive care unit can manage the higher acuity of persistent hypotension and deliver treatment and medications needing close hemodynamic monitoring.  

Definition 

A eugenic blood pressure range is between 90/60 and 120/80 mmHg. As individual blood pressures vary, concern for treatment is guided by the patient’s presentation to determine if the measured blood pressure requires intervention. Asymptomatic hypotension is rarely a concern and may be monitored for progression. However, symptomatic hypotension may be defined as blood pressure that is below acceptable values to promote adequate tissue perfusion and requires intervention (1).  

Generally, in the ICU, the mean arterial pressure (MAP) is monitored to ascertain that blood pressure is sustainable for hemodynamic stability. It is a more accurate and reliable method of determining hypoperfusion than the systolic and diastolic readings alone. The MAP is a calculation of the average blood pressure during one isolated, full cardiac cycle and will vary depending on the systolic and diastolic pressures, cardiac output, as well as systemic resistance. MAP can easily be calculated with the following formula: 

MAP = SBP + 2 (DBP) 

In hypotensive episodes that are severely symptomatic or persistent, the cause must be identified, if not already evident, and treatment aimed at supportive care. While treating the underlying condition that is the cause of the hemodynamic instability, hypotensive treatment is supportive and may require volume boluses (albumin, blood, or crystalloid fluids) and/or pharmaceutical agents that are titratable and require invasive monitoring (1). 

Case Study 

A 75-year-old female is admitted to a medical-surgical unit with pneumonia. During the admission assessment, it was found that her blood pressure is 78/56 and she states feeling dizzy and nauseous. Her skin is cold and clammy, and her breathing is shallow at 10 breaths per minute. 

Assessment 

Blood pressure that is too low to sustain optimal perfusion rapidly causes a cascade of signs and symptoms. This sequalae can affect every body system due to a decrease in delivering oxygen-rich blood and nutrients to the tissues and cells of the organs vital to life leading to systemic collapse and shock (1). 

A focused assessment will be guided by the suspected underlying cause of the hypotension. A thorough history and physical examination of the patient should include previous cardiac history, any recent illness or infection, medications taken daily, and what treatment has been already completed if the patient is transferring from another unit. Following, a systems-based assessment will primarily focus on supporting hemodynamic function until the patient is stabilized. 

Cardiovascular 

A thorough evaluation of the cardiovascular system via hemodynamic parameters is required.  

Monitoring of blood pressure may be non-invasively obtained with a sphygmomanometer or less commonly via the vascular unloading technique, such as finger-cuff technology. An automatic cuff may not be able to capture an accurate blood pressure and the nurse should be cognizant of varying results or if the cuff continues to inflate without capturing a number. In this case, a manual blood pressure should be attempted.  

For hypotension that does not respond to initial treatment, the care team may consider inserting an invasive method of blood pressure measurement that is continuous and eliminates the variability and discrepancies that have been found with intermittent non-invasive measuring methods (2).  

The most accurate method of hemodynamic monitoring of blood pressure is through an arterial line. Also referred to as an art-line or an A-line, this is a minimally invasive procedure, where a size 4 to 7 French sheath is placed into the radial or femoral artery (3). With the use of a transducer, a continuous measurement of blood pressure is available to initiate appropriate treatment, assess interventions, and guide continued clinical care.  

Nursing considerations for managing an arterial line include positioning, ensuring the line is zeroed, appropriate placement of transducer at the level of phlebostatic axis, and knowledge of identifying arterial blood pressure waveforms. Education and skills verification must be completed as part of critical care training before managing to ensure safe handling and use, as well as recognition of the two most common artifacts with correction to ensure accurate readings are observed (2,3).  

An ECG may be obtained to evaluate for any dysrhythmias. For patients that have a prior cardiac history, continuous telemetry is appropriate, and the nurse should ensure this is ordered by the attending healthcare provider with optimal capture of the cardiac rhythm. An initial telemetry strip should be printed upon placement to provide a baseline to compare against any potential changes that would indicate a decline (1). 

Respiratory 

The respiratory systems must be evaluated for any infection or condition leading to pulmonary edema. The auscultated lung sounds, respiratory rate, pattern, and effort, expectorate, and symmetry of chest movement are evaluated and documented in the chart. Continuous O2 monitoring and documentation of any need for supplemental oxygen including the delivery method are a standard for ICU patients. 

Temperature 

Any temperature variation from normal must be noted and trended. Hypotensive crisis related to systemic inflammatory response syndrome and sepsis are partially assessed based on a temperature that is < 36°C or > 38.3°C. Any temperature in these parameters should be considered statistically significant and be communicated with the primary care team (5). 

Laboratory Values  

There are several laboratory values that may be monitored to assess for cardiac ischemia and injury, heart failure, and systemic tissue damage. The following are the most commonly assessed to diagnose underlying factors and guide treatment (5, 8): 

Cardiac Biomarkers 

• Troponin I (cTnl) assesses for proteins that are released when damage to the heart muscle occurs. Elevated levels,> 0.04 ng/mL may be indicative of a cardiac event such as a myocardial infarction but may also be related to renal damage, heart failure, or a pulmonary embolism. With cardiac ischemia and injury, the level will peak approximately 24 hours post-occurrence of infarction and then remain elevated for up to 14 days. 

• Creatinine kinase (CK) is an enzyme that is involved in muscle cell function. The normal value is between 22 and 198 U/L. When elevated, cardiac or skeletal muscle damage is likely to have occurred. 

Sepsis markers 

• White Blood Count will assess for an immune response to the presence of inflammation or infection with >12,000/mm3 or <4,000/mm3, or a shift of bands to the left >10% 

• Lactate dehydrogenase is a reliable marker of organ dysfunction. This evaluates the presence and concentration of lactic acid which is a byproduct of anaerobic metabolism. A value that is higher than 2.0 indicates organ damage from hypoperfusion.  

• Procalcitonin becomes elevated with the presence of bacterial infection and can assist in diagnosis and managing sepsis. A level that is greater than 2.0 ng/mL indicates a high chance that a bacterial infection is systemic and will progress to sepsis or septic shock. 

• Blood Gases 

• As shock progresses, arterial blood gases reveal metabolic acidosis. This can be recognized with a decrease in HCO3 and decreased arterial pH level. With early fluid resuscitation, aerobic metabolism is maintained, and acidosis can be normalized. 

Case Study 

Despite a 1L fluid bolus of Normal Saline 0.9%, the patient remains hypotensive at 82/47. Pallor is noted, with diaphoresis. The attending healthcare provider is notified that the patient has not responded to the ordered therapy and a transfer request to the ICU is placed. A rapid response is called overhead when the patient has a syncopal episode lasting twenty seconds and blood pressure cannot be obtained with the automatic blood pressure cuff. The primary nurse is reporting to the ICU nurse while other members of the care team transport the patient to the ICU. 

Pathophysiology 

Severe hypotension requiring critical care management may be caused by a cascade of physiological deviations that can be broken down into four major types of shock. While not all shock presents as hypotension, it is a major factor in the hypotensive events that are managed within the ICU. The four types of shock include distributive, obstructive, cardiogenic, and hypovolemic.  

Distributive shock may be caused by paraplegia, infection, sepsis, and sedation.  

Obstructive shock is due to a physical blockage preventing the normal flow of blood through the cardiovascular system. 

Pulmonary embolism and cardiac tamponade are the most common causes of obstruction that lead to reduced cardiac output.  

Cardiogenic shock is related to an anomaly in the electrical or pumping efficacy of the heart resulting in marked circulatory dysfunction.  

Hypovolemia is the last major category that leads to reduced systemic circulation and may be due to dehydration or massive fluid loss, such in the case of hemorrhage or fluid shifts seen with ascites related to hepatorenal syndrome. When the cause is multifactorial, it may be labeled as mixed (4, 6).  

Other forms of sustained hypotension are identified as non-shock related and may be due to certain medication functions, especially cardiogenic drugs such as anti-hypertensive agents, or to disease processes that do not result in shock (4, 5, 8). 

Medications that may be the cause of hypotension are typically anesthesia-related or cardiac agents. These include ACE inhibitors, beta-adrenergic antagonists, calcium channel blockers, antidysrhythmic, cardiac glycosides, and nitrates. Depending on the mechanism of action within the drug category, these medications have the potential to lower systemic vascular resistance, decrease cardiac output, decrease heart rate, and suppress electrical conductivity leading to a potential for hypotensive episodes (4, 5, 8). 

Case Study 

While being transported, the patient has a run of symptomatic SVT at a rate of 160 bpm that responds to on delivery of synchronized cardioversion. The patient’s respiratory rate continues to decline and intubation with mechanical ventilation is initiated.  

Clinical Signs and Symptoms 

The following are the major organ systems along with accompanying signs and symptoms that occur with severe hypotension (all from 5, 8): 

Neurological 

• Lightheadedness 
• Syncopal episodes 
• Fatigue 
• Declined cognitive function. 

Respiratory 

• Rapid, shallow breathing 
• Cyanosis 

Integumentary 

• Diaphoresis 
• Cool, clammy skin 
• Poor circulation, capillary refill < 3 seconds 

Circulatory 

• Angina 
• Myocardial infarction 
• Weak, thready pulse 
• Tachycardias 
• Ectopy 
• Decreased cardiac output. 
• Mean Arterial Pressure < 65 mmHg. 

Digestive 

• Nausea, vomiting 
• Gastrointestinal ischemia 

Renal 

• Reduced urine production 
• Acute kidney injury as indicated by elevated creatinine. 

Medical Management 

Initial treatment for any symptomatic hypotension typically begins with crystalloid fluid therapy of at least 250 ml but may be up to three liters for massive fluid loss from hemorrhage. Mass transfusion protocols may be initiated if the source of bleeding is not quickly recognized or stopped (1, 6, 8).  

Alpha1-adrenergic agonists such as methoxamine, midodrine, and phenylephrine will increase systemic volume resistance, thereby resulting in increased blood pressure. Sympathomimetic medications, such as epinephrine, norepinephrine, dobutamine, and dopamine all have cardiogenic effects to increase cardiac output and systemic volume resistance. After fluid volume resuscitation, a vasopressor such as norepinephrine should be started first. An inotrope may be added if it is known that the patient’s cardiac contractility is decreased.  

The properties of alpha- and beta-adrenergic agonists include vasoconstriction, increased force of cardiac contraction, or an increased rate of cardiac conduction depending upon which receptors are targeted. The dosage and rates of these medications should be titrated as ordered with facility policy followed for monitoring and documentation standards.  

These cardiac medications are caustic to vessels and should be delivered via a central line at the earliest opportunity (5). 

Hypotension induced by an anaphylactic reaction has additional precautions and treatment. The first line of treatment is to establish and maintain an airway. Administration of 0.3 mg epinephrine 1:1000 intramuscular injection will block the release of inflammatory mediators. If the patient is on a beta-blocker, 5-15 mcg/min of a glucagon infusion may be necessary to achieve bronchodilation and reverse hypotension this will override the alpha and beta receptors that epinephrine typically requires to reach clinical efficacy (5, 8). 

Nursing Interventions 

Positional maneuvers may augment medical management. A Trendelenburg can promote venous return to the heart, increase MAP, and assist with lessening neurological symptoms by enhancing brain perfusion (1, 7). 

A urinary catheter should be placed per order to capture strict measurement of input and output for documentation. The goal for urine output is to maintain at least > 0.5 mL/kg/hr. (4, 5, 8).  

Case Study 

The patient’s continued supportive care has continued for two days, without improvement. 

Conclusion

Hypotension management can be tricky depending upon the patient’s response to initial therapy. The underlying cause is a priority to identify treatment early for the best outcomes. Often, sustained hypotension is not easily managed on a medical-surgical unit and the patient will be transferred to an ICU, where the expertise and knowledge of the critical staff provide the medical management and interventions to deal with what can quickly evolve into shock. The best practice remains early fluid resuscitation along with supportive cardiogenic agents such as vasopressors and inotropics. 

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