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BIOC33H3 (127)

Critical Care

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Biological Sciences
Stephen Reid

Chapter 66: Critical Care  Critical care units or intensive care units (ICUs) are designed to meet the special needs of acutely and critically ill patients.  ICU care has expanded from delivering care in a standard unit to bringing ICU care to patients wherever they might be. o The electronic or virtual ICU is designed to augment the bedside ICU team by monitoring the patient from a remote location. o The rapid response team, composed of a critical care nurse, a respiratory therapist, and critical care physician or advanced practice nurse, goes outside the ICU to bring rapid and immediate care to unstable patients in non–critical care units.  Progressive care units, also called high-dependency units, intermediate care units, or stepdown units, serve as transition units between the ICU and the general care unit or discharge. o The American Association of Critical Care Nurses’ (AACN) offers certification for progressive care nurses (PCCN) working with acutely ill adult patient.  The critical care nurse is responsible for assessing life-threatening conditions, instituting appropriate interventions, and evaluating the outcomes of the interventions. o Critical care nursing requires in-depth knowledge of anatomy, physiology, pathophysiology, pharmacology, and advanced assessment skills, as well as the ability to use advanced biotechnology. o The AACN offers critical care certification (CCRN) in adult, pediatric, and neonatal critical care nursing.  Advanced practice critical care nurses have a graduate (master’s or doctorate) degree and are employed in a variety of roles: patient and staff educators, consultants, administrators, researchers, or expert practitioners. o A clinical nurse specialist (CNS) typically functions in one or more of these roles. Certification for the CNS in acute and critical care (CCNS) is available through the AACN. o An acute care nurse practitioner (ACNP) provides comprehensive care to select critically ill patients and their families that includes conducting comprehensive assessments, ordering and interpreting diagnostic tests, managing health problems and disease-related symptoms, and prescribing treatments. Certification as an ACNP is available through the AACN. COMMON PROBLEMS OF CRITICAL CARE PATIENTS  Nutrition: o The primary goal of nutritional support is to prevent or correct nutritional deficiencies. This is usually accomplished by the early provision of enteral nutrition (i.e., delivery of calories via the gastrointestinal [GI] tract) or parenteral nutrition (i.e., delivery of calories intravenously). o Parenteral nutrition should be considered only when the enteral route is unsuccessful in providing adequate nutrition or contraindicated (e.g., paralytic ileus, diffuse peritonitis, intestinal obstruction, pancreatitis, GI ischemia, intractable vomiting, and severe diarrhea).  Anxiety: o The primary sources of anxiety for patients include the perceived or anticipated threat to physical health, actual loss of control or body functions, and an environment that is foreign. o Assessing patients for anxiety is very important and clinical indicators can include agitation, increased blood pressure, increased heart rate, patient verbalization of anxiety, and restlessness. o To help reduce anxiety, the nurse should encourage patients and families to express concerns, ask questions, and state their needs; and include the patient and family in all conversations and explain the purpose of equipment and procedures. o Antianxiety drugs and complementary therapies may reduce the stress response and should be considered.  Pain: o The control of pain in the ICU patient is paramount as inadequate pain control is often linked with agitation and anxiety and can contribute to the stress response. o ICU patients at high risk for pain include patients (1) who have medical conditions that include ischemic, infectious, or inflammatory processes; (2) who are immobilized; (3) who have invasive monitoring devices, including endotracheal tubes; (4) and who are scheduled for any invasive or noninvasive procedures. o Continuous intravenous sedation and an analgesic agent are a practical and effective strategy for sedation and pain control.  Impaired communication: o Inability to communicate can be distressing for the patient who may be unable to speak because of sedative and paralyzing drugs or an endotracheal tube. o The nurse should explore alternative methods of communication, including the use of devices such as picture boards, notepads, magic slates, or computer keyboards. For patients who do not speak English, the use of an interpreter is recommended. o Nonverbal communication is important. Comforting touch with ongoing evaluation of the patient’s response should be provided. Families should be encouraged to touch and talk with the patient even if the patient is unresponsive or comatose.  Sensory-perceptual problems: o Delirium in ICU patients ranges from 15% to 40%.  Demographic factors predisposing the patient to delirium include advanced age, preexisting cerebral illnesses, use of medications that block rapid eye movement sleep, and a history of drug or alcohol abuse.  Environmental factors that can contribute to delirium include sleep deprivation, anxiety, sensory overload, and immobilization.  Physical conditions such as hemodynamic instability, hypoxemia, hypercarbia, electrolyte disturbances, and severe infections can precipitate delirium.  Certain drugs (e.g., sedatives, furosemide, antimicrobials) have been associated with the development of delirium.  The ICU nurse must identify predisposing factors that may precipitate delirium and improve the patient’s mental clarity and cooperation with appropriate therapy (e.g., correction of oxygenation, use of clocks and calendars).  If the patient demonstrates unsafe behavior, hyperactivity, insomnia, or delusions, symptoms may be managed with neuroleptic drugs (e.g., haloperidol).  The presence of family members may help reorient the patient and reduce agitation. o Sensory overload can also result in patient distress and anxiety.  Environmental noise levels are particularly high in the ICU and the nurse should limit noise and assist the patient in understanding noises that cannot be prevented.  Sleep problems: o Patients may have difficulty falling asleep or have disrupted sleep because of noise, anxiety, pain, frequent monitoring, or treatment procedures. o Sleep disturbance is a significant stressor in the ICU, contributing to delirium and possibly affecting recovery. o The environment should be structured to promote the patient’s sleep-wake cycle by clustering activities, scheduling rest periods, dimming lights at nighttime, opening curtains during the daytime, obtaining physiologic measurements without disrupting the patient, limiting noise, and providing comfort measures. o Benzodiazepines and benzodiazepine-like drugs can be used to induce and maintain sleep. ISSUES RELATED TO FAMILIES  Family members play a valuable role in the patient’s recovery and should be considered members of the health care team. They contribute to the patient’s well-being by: o Providing a link to the patient’s personal life o Advising the patient in health care decisions or functioning as the decision maker when the patient cannot o Helping with activities of daily living o Providing positive, loving, and caring support  To provide family-centered care effectively, the nurse must be skilled in crisis intervention. o Interventions can include active listening, reduction of anxiety, and support of those who become upset or angry. o Other health team members (e.g., chaplains, psychologists, patient representatives) may be helpful in assisting the family to adjust and should be consulted as necessary.  The major needs of families of critically ill patients have been categorized as informational needs, reassurance needs, and convenience needs. o Lack of information is a major source of anxiety for the family. The family needs reassurance regarding the way in which the patient’s care is managed and decisions are made and the family should be invited to meet the health care team members, including physicians, dietitian, respiratory therapist, social worker, physical therapist, and chaplain. o Rigid visitation policies in ICUs should be reviewed, and a move toward less restrictive, individualized visiting policies is strongly recommended by the AACN. o Research has demonstrated that family members of patients undergoing invasive procedures, including cardiopulmonary resuscitation, should be given the option of being present at the bedside during these events. HEMODYNAMIC MONITORING  Hemodynamic monitoring refers to the measurement of pressure, flow, and oxygenation within the cardiovascular system. Both invasive and noninvasive hemodynamic measurements are made in the ICU.  Values commonly measured include systemic and pulmonary arterial pressures, central venous pressure (CVP), pulmonary artery wedge pressure (PAWP), cardiac output/index, stroke volume/index, and oxygen saturation of the hemoglobin of arterial blood (SaO ) 2 and mixed venous blood (SvO ).2  Cardiac output (CO) is the volume of blood pumped by the heart in 1 minute. Cardiac index (CI) is the measurement of the CO adjusted for body size.  The volume ejected with each heartbeat is the stroke volume (SV). Stroke volume index (SVI) is the measurement of SV adjusted for body size.  The opposition to blood flow offered by the vessels is called systemic vascular resistance (SVR) or pulmonary vascular resistance (PVR).  Preload, afterload, and contractility determine SV (and thus CO and blood pressure).  Preload is the volume within the ventricle at the end of diastole.  PAWP, a measurement of pulmonary capillary pressure, reflects left ventricular end- diastolic pressure under normal conditions.  CVP, measured in the right atrium or in the vena cava close to the heart, is the right ventricular preload or right ventricular end-diastolic pressure under normal conditions.  Afterload refers to the forces opposing ventricular ejection and includes systemic arterial pressure, the resistance offered by the aortic valve, and the mass and density of the blood to be moved.  Systemic vascular resistance (SVR) is the resistance of the systemic vascular bed. Pulmonary vascular resistance (PVR) is the resistance of the pulmonary vascular bed. Both of these measures can be adjusted for body size.  Contractility describes the strength of contraction. Agents that increase or improve contractility are termed positive inotropes. Contractility is diminished by negative inotropes, such as certain drugs (e.g., calcium channel blockers, β-adrenergic blockers) and conditions (e.g., acidosis). Principles of Invasive Pressure Monitoring  To accurately measure pressure, equipment must be referenced and zero balanced to the environment and dynamic response characteristics optimized.  Referencing means positioning the transducer so that the zero reference point is at the level of the atria of the heart or the phlebostatic axis.  Zeroing confirms that when pressure within the system is zero, the monitor reads zero. Zeroing is recommended during initial setup, immediately after insertion of the arterial line, when the transducer has been disconnected from the pressure cable or the pressure cable has been disconnected from the monitor, and when the accuracy of the measurements is questioned.  Optimizing dynamic response characteristics involves checking that the equipment reproduces, without distortion, a signal that changes rapidly. A dynamic response test (square wave test) is performed every 8 to 12 hours and when the system is opened to air or the accuracy of the measurements is questioned. Types of Invasive Pressure Monitoring  Continuous arterial pressure monitoring is indicated for patients experiencing acute hypertension and hypotension, respiratory failure, shock, neurologic injury, coronary interventional procedures, continuous infusion of vasoactive drugs, and frequent ABG sampling. o High- and low-pressure alarms should be set based on the patient’s current status. Measurements are obtained at end expiration to limit the effect of the respiratory cycle on arterial pressure. o Arterial lines carry the risk of hemorrhage, infection, thrombus formation, neurovascular impairment, and loss of limb. o To help maintain line patency and limit thrombus formation, a continuous flush irrigation system is used to deliver 3 to 6 ml of heparinized saline per hour.  Neurovascular status distal to the arterial insertion site is assessed hourly. Neurovascular impairment can result in loss of a limb and is an emergency.  Pulmonary artery (PA) pressure monitoring is used to guide acute-phase management of patients with complicated cardiac, pulmonary, and intravascular volume problems. o PA diastolic (PAD) pressure and PAWP are sensitive indicators of cardiac function and fluid volume status and are routinely monitored. o Monitoring PA pressures can allow precise therapeutic manipulation of preload, which allows CO to be maintained without placing the patient at risk for pulmonary edema. o A PA flow-directed catheter (e.g., Swan-Ganz) is used to measure PA pressures, including PAWP. When properly positioned, the distal lumen port (catheter tip) is within the PA and is used to monitor PA pressures and sample mixed venous blood specimens (e.g., to evaluate oxygen saturation). o Additional lumens have exit ports in the right atrium or right atrium and right ventricle (if two).  The right atrium port is used for measurement of CVP, injection of fluid for CO determination, and withdrawal of blood specimens.  If a second proximal port is available, it is used for infusion of fluids and drugs or blood sampling. o A thermistor (temperature sensor) lumen port located near the distal tip is used for monitoring blood or core temperature and is used in the thermodilution method of measuring CO. o PA measurements are obtained at the end of expiration. o PAWP measurement is obtained by slowly inflating the balloon with air (not to exceed balloon capacity) until the PA waveform changes to a PAWP waveform.  The balloon should be inflated for no more than four respiratory cycles or 8 to 15 seconds.  CVP is a measurement of right ventricular preload. It can be measured with a PA catheter using one of the proximal lumens or with a central venous catheter placed in the internal jugular or subclavian vein.  The PA catheter is commonly used to measure CO via the intermittent bolus thermodilution CO method or the continuous CO method.  SVR, SVR index, SV, and SV index can be calculated each time that CO is measured. o Increased SVR indicates vasoconstriction from shock, hypertension, increased release or administration of epinephrine and other vasoactive inotropes, or left ventricular failure. o Decreased SVR indicates vasodilation, which may occur during shock states (e.g., septic, neurogenic) or with drugs that reduce afterload. o Changes in SV are becoming more important indicators of the pumping status of the heart than other parameters. Noninvasive Hemodynamic Monitoring  Impedance cardiography (ICG) is a continuous or intermittent, noninvasive method of obtaining CO and assessing thoracic fluid status.  Impedance-based hemodynamic parameters (CO, SV, and SVR) can be calculated from Zo, dZ/dt, MAP, CVP, and the ECG.  Major indications for ICG include early signs and symptoms of pulmonary or cardiac dysfunction, differentiation of cardiac or pulmonary cause of shortness of breath, evaluation of etiology and management of hypotension, monitoring after discontinuing a PA catheter or justification for insertion of a PA catheter, evaluation of pharmacotherapy, and diagnosis of rejection following cardiac transplantation. Venous Oxygen Saturation  Both CVP and PA catheters can include sensors to measure oxygen saturation of hemoglobin in venous blood termed mixed venous oxygen saturation (ScvO , SvO ).2 2  SvO 2ScvO re2lects the dynamic balance between oxygenation of the arterial blood, tissue perfusion, and tissue oxygen consumption (VO ). 2 o Normal SvO /Scv2 at re2t is 60% to 80%. o Sustained decreases in SvO /Sc2O may i2dicate decreased arterial oxygenation, low CO, low hemoglobin level, or increased oxygen consumption or extraction. If the SvO /ScvO falls below 60%, the nurse determines which of these factors has 2 2 changed. o Sustained increases in SvO /Sc2O may 2ndicate a clinical improvement (e.g., increased arterial oxygen saturation, decreased metabolic rate) or problems (e.g., sepsis). Complications with PA Catheters  Infection and sepsis are serious problems associated with PA catheters. o Careful surgical asepsis for insertion and maintenance of the catheter and attached tubing is mandatory. o Flush bag, pressure tubing, transducer, and stopcock should be changed every 96 hours.  Air embolus is another risk associated with PA catheters.  Pulmonary infarction or PA rupture from: (1) balloon rupture, releasing air and fragments that could embolize; (2) prolonged balloon inflation obstructing blood flow; (3) catheter advancing into a wedge position, obstructing blood flow; and (4) thrombus formation and embolization. o Balloon must never be inflated beyond the balloon’s capacity (usually 1 to 1.5 ml of air). And must not be left inflated for more than four breaths (except during insertion) or 8 to 15 seconds. o PA pressure waveforms are monitored continuously for evidence of catheter occlusion, dislocation, or spontaneous wedging. o PA catheter is continuously flushed with a slow infusion of heparinized (unless contraindicated) saline solution.  Ventricular dysrhythmias can occur during PA catheter insertion or removal or if the tip migrates back from the PA to the right ventricle and irritates the ventricular wall.  The nurse may observe that the PA catheter cannot be wedged and may need to be repositioned by the physician or a qualified nurse. Noninvasive Arterial Oxygenation Monitoring  Pulse oximetry is a noninvasive and continuous method of determining arterial oxygenation (SpO ),2and monitoring SpO may2reduce the frequency of ABG sampling.  SpO is normally 95% to 100%. 2  Accurate SpO m2asurements may be difficult to obtain on patients who are hypothermic, receiving intravenous vasopressor therapy, or experiencing hypoperfusion.  Alternate locations for placement of the pulse oximetry probe may need to be considered (e.g., forehead, earlobe). Nursing Management: Hemodynamic Monitoring  Baseline data regarding the patient’s general appearance, level of consciousness, skin color and temperature, vital signs, peripheral pulses, and urine output are obtained.  Baseline data are correlated with data obtained from biotechnology (e.g., ECG; arterial, CVP, PA, PAWP pressures; SvO /ScvO2). 2  Single hemodynamic values are rarely significant; the nurse monitors trends in these values and evaluates the whole clinical picture with the goals of recognizing early clues and intervening before problems escalate. CIRCULATORY ASSIST DEVICES  Circulatory assist devices (CADs) decrease cardiac work and improve organ perfusion when conventional drug therapy is no longer adequate.  CADs provide interim support in three types of situations: (1) the left, right, or both ventricles require support while recovering from acute injury; (2) the heart requires surgical repair (e.g., a ruptured septum), but the patient must be stabilized; and (3) the heart has failed, and the patient is awaiting cardiac transplantation. Intraaortic Balloon Pump  The intraaortic balloon pump (IABP) provides temporary circulatory assistance to the compromised heart by reducing afterload (via reduction in systolic pressure) and augmenting the aortic diastolic pressure resulting in improved coronary blood flow and perfusion of vital organs.  The IABP consists of a sausage-shaped balloon, a pump that inflates and deflates the balloon, control panel for synchronizing the balloon inflation to the cardiac cycle, and fail-safe features.  IABP therapy is referred to as counterpulsation because the timing of balloon inflation is opposite to ventricular contraction.  The IAPB assist ratio is 1:1 in the acute phase of treatment, that is, one IABP cycle of inflation and deflation for every heartbeat.  Complications of IABP therapy may include vascular injuries such as dislodging of plaque, aortic dissection, and compromised distal circulation. o Thrombus and embolus formation add to the risk of circulatory compromise to the extremity. o Mechanical complications are rare and include improper timing of balloon inflation causing increased afterload, decreased CO, myocardial ischemia, and increased myocardial oxygen demand. o To reduce risks of IABP therapy, cardiovascular, neurovascular, and hemodynamic assessments are necessary every 15 to 60 minutes depending on the patient’s status.  The patient is relatively immobile, limited to side-lying or supine positions with the head of the bed elevated less than 45 degrees. The leg in which the catheter is inserted must not be flexed at the hip to avoid kinking or dislodgement of the catheter. Ventricular Assist Devices  Ventricular assist devices (VADs) provide longer-term support for the failing heart (usually months) and allow more mobility than the IABP.  VADs are inserted into the path of flowing blood to augment or replace the action of the ventricle. Some VADs are implanted (e.g., peritoneum), and others are positioned externally.  Some VADs provide biventricular support.  Indications for VAD therapy include (1) extension of CPB for failure to wean or postcardiotomy cardiogenic shock, (2) bridge to recovery or cardiac transplantation, and (3) patients with New York Heart Association Classification IV who have failed medical therapy. Nursing Management: Circulatory Assist Devices  Nursing care of the patient with a VAD is similar to that of the patient with an IABP. o Patients are observed for bleeding, cardiac tamponade, ventricular failure, infection, dysrhythmias, renal failure, hemolysis, and thromboembolism. o A patient with VAD may be mobile and require an activity plan.  Ideally, patients with CADs will recover through ventricular improvement, heart transplantation, or artificial heart implantation.  However, many patients die, or the decision to terminate the device is made and death follows. Both the patient and family require psychologic support. ARTIFICIAL AIRWAYS  Endotracheal intubation (ET intubation) involves the placement of a tube into the trachea via the mouth or nose past the larynx.  Indications for ET intubation include (1) upper airway obstruction (e.g., secondary to burns, tumor, bleeding), (2) apnea, (3) high risk of aspiration, (4) ineffective clearance of secretions, and (5) respiratory distress.  A tracheotomy is a surgical procedure that is performed when the need for an artificial airway is expected to be long term.  Oral ET intubation is the procedure of choice for most emergencies because the airway can be secured rapidly, a larger diameter tube can be used thus reducing the work of breathing (WOB) and making it easier to remove secretions and perform fiberoptic bronchoscopy.  Nasal ET intubation is indicated when head and neck manipulation is risky. Endotracheal Intubation Procedure  All patients undergoing intubation need to have a self-inflating bag-valve-mask (BVM) available and attached to oxygen, suctioning equipment ready and intravenous access.  Premedication varies, depending on the patient’s level of consciousness (e.g., awake, obtunded) and the nature of the procedure (e.g., emergent, nonemergent).  Rapid sequence intubation (RSI) is the rapid, concurrent administration of a combination of both a paralytic agent and a sedative agent during emergency airway management to decrease the risks of aspiration, combativeness, and injury to the patient. RSI is not indicated in patients who are comatose or during cardiac arrest.  Before intubation is attempted, the patient is preoxygenated using a self-inflating BVM with 100% O f2r 3 to 5 minutes. o Each intubation attempt is limited to less than 30 seconds. If unsuccessful, the patient is ventilated between successive attempts using the BVM with 100% O . 2  Following intubation, the cuff is inflated, and the placement of the ET tube is confirmed while manually ventilating the patient with 100% O .2 o An end-tidal CO det2ctor is to confirm proper placement by measuring the amount of exhaled CO fr2m the lungs.  The detector is placed between the BVM and the ET tube and either observed for a color change (indicating the presence of CO 2 or a number.  If no CO 2s detected, than the tube is in the esophagus. o The lung bases and apices are auscultated for bilateral breath sounds, and the chest is observed for symmetric chest wall movement. o A portable chest x-ray is immediately obtained to confirm tube location (3 to 5 cm above the carina in the adult).  The ET tube is connected either to humidified air, O2, or a mechanical ventilator.  ABGs should be obtained within 25 minutes after intubation to determine oxygenation and ventilation status.  Continuous pulse oximetry monitoring provides an estimate of arterial oxygenation. Nursing Management: Artificial Airway  Maintaining Correct Tube Placement o The nurse must monitor the patient with an ET tube for proper placement at least every 2 to 4 hours. o Proper tube position is maintained by confirming that the exit mark on the tube remains constant while at rest, during patient care, repositioning, and patient transport. o The nurse observes for symmetric chest wall movement and auscultates to confirm bilateral breath sounds. o It is an emergency if the ET tube is not positioned properly.  The nurse stays with the patient, maintains the airway, supports ventilation, and secures the appropriate assistance to immediately reposition the tube.  It may be necessary to ventilate the patient with a BVM.  Maintaining Proper Cuff Inflation o The cuff is an inflatable, pliable sleeve encircling the outer wall of the ET tube that stabilizes and seals the ET tube within the trachea and prevents escape of ventilating gases. o The cuff can cause tracheal damage.  To avoid damage, the cuff is inflated with air, and the pressure in the cuff is measured and monitored.  Normal arterial tracheal perfusion is estimated at 30 mm Hg and cuff pressure should be maintained at 20 to 25 mm Hg.  Depending on the institution’s policy, cuff pressure is measured and recorded after intubation and on a routine basis (e.g., every 8 hours) using the minimal occluding volume (MOV) technique or the minimal leak technique (MLT).  The steps of the MOV technique are as follows: (1) for the mechanically ventilated patient, place a stethoscope over the trachea and inflate the cuff to MOV by adding air until no air leak is heard at peak inspiratory pressure (end of ventilator inspiration); (2) for the spontaneously breathing patient, inflate until no sound is heard after a deep breath or after inhalation with a BVM; (3) use a manometer to verify that cuff pressure is between 20 and 25 mm Hg; and (4) record cuff pressure in the chart.  The procedure for MLT is similar with one exception. A small amount of air is removed from the cuff until a slight leak is auscultated at peak inflation.  Both techniques are intended to prevent the risks of tracheal trauma due to high cuff pressures.  If adequate cuff pressure cannot be maintained or larger volumes of air are needed to keep the cuff inflated, the cuff could be leaking or there could be tracheal dilation at the cuff site and the ET tube should be repositioned or changed and the physician should be notified.  Monitoring Oxygenation and Ventilation o Oxygenation: Assessment of ABGs, SpO , SvO /S2vO , a2d clin2cal signs of hypoxemia such as a change in mental status (e.g., confusion), anxiety, dusky skin, and dysrhythmias. o Ventilation: Assessment of PaCO , con2inuous partial pressure of end-tidal CO
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