SHOCK

SHOCK OBJECTIVESUpon completion of this chapter/lecture, the learner should be able to:1. Define the four types of shock.2. Describe the path physiologic changes as a basis for the signs and symptoms of shock.3. Discuss the nursing assessment of the patient in shock.4. Based on assessment data, identify nursing diagnoses and expected outcomes associated with patient in shock.5. Plan appropriate interventions for the patient in shock.6. Evaluate the effectiveness of nursing interventions for patients in shoe

INTRODUCTION

Classification and EtiologyShock is a syndrome resulting from inadequate perfusion of tissues, leading to a decrease in the supply of oxygen and nutrients required to maintain the metabolic needs of cells. When the supply of oxygen and nutrients cannot meet the demand to sustain normal cellular metabolism, the body responds initially by activating intrinsic compensatory mechanisms to improve perfusion, especially in areas of high demand such as the brain, heart, and lungs. When compensatory mechanisms fail to-restore adequate perfusion, a cascade of cellular abnormalities can result in total organ dysfunction and, eventually, death

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Numerous classification systems have been used to define shock either by causes or by the underlying path physiologic effects. One such system classifies shock syndromes according to the underlying pathology:

Etiology Underlying pathology

Hypovolomic - hemorrhage - burns

- whole blood loss- plasma loss

Cardiogenic - myocardial infraction - dysrrythmia - blunt cardiac injury

- loss of cardiac contractility - reduced cardiac output - loss of cardiac contractility

Obstructive - Cardiac tamponade - tension pneumothorax - tension hemothorax

- compression of the heart with obstruction of a trial fillingmediastinal shift with obstruction of atrial fillingcombination of above

distributive - Neurogenic shock - Anaphylactic shock

- Septic shock

-Venous pooling- maldestribution of blood-Shunting in microcirculation and in later stage- decrease in venous resistance.-Poor distribution of blood

HYPOVOLEMIC SHOCKThe most common shock syndrome to affect a trauma patient is caused by hypovolemia. Hypovolemia a decrease in the amount of circulating blood volume may result from a significant loss of whole blood because of hemorrhage. It may also result from the loss of the semi permeable integrity of the cellular membrane leading to leakage of plasma and protein from the intravascular space to the interstitial space,

CARDIOGENIC SHOCKCardiogenic shock is a syndrome that results from ineffective perfusion caused by inadequate contractility of the cardiac muscle. Some of the causes of cardiogenic shock are myocardial infarction, blunt cardiac injury, mitral valve insufficiency, dysrhythmias, and cardiac failure.

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OBSTRUCTIVE SHOCKObstructive shock results from an inadequate circulating blood volume because of an obstruction or compression of the great veins, aorta, pulmonary arteries, or the heart itself. Cardiac tamponade may compress the heart during diastole to such an extent that the atria cannot adequately fill leading to a decrease in stroke volume. A tension pneumothorax may also lead to an inadequate stroke volume by diplacing the inferior vena cava and obstructing venous return to the right atrium.

DISTRIBUTIVE SHOCKThe fourth category of shock is distributive shock, which is a shock syndrome resulting from either poor distribution of blood flow or blood volume. Examples of shock because of a change in the distribution of blood volume are neurogenic and anaphylactic shock. Neurogenic shock may occur as a result of injury to the spinal cord in the cervical or upper thoracic region.

PATHOPHYSIOLOGY AS A BASIS FOR SIGNS AND SYMPTOMSShock is a syndrome that involves all cells and their chemical and metabolic balance. The consequences of inadequate tissue perfusion can be described organ by organ. The body responds to shock by initiating compensatory mechanisms as specific organ systems are affected. Untreated, shock can progress to irreversible stages as the body's own compensatory mechanisms fail to restore perfusion and as organ systems become unable to maintain homeostasis. Some of the compensatory mechanisms and their responses follow.

Vascular ResponseAs blood volume decreases, the peripheral blood vessels vasoconstriction as a result of sympathetic stimulation via inhibition of the baroreceptors. The arterioles constrict to increase total peripheral resistance and, ultimately, blood pressure. The venous capacitance system vasoconstricts to improve venous return to the right atrium

Cerebral ResponseAs shock progresses, the primary goal of the body is to maintain perfusion of the brain, heart, and lungs. Consequently, blood flow to these centers is

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preserved while blood flow to other organs, such as the liver, bowel, skin and to some extent, the kidneys, may be compromised. Sympathetic stimulation (compensatory vasoconsinction) has little effect on cerebral and coronary vessels, but the brain and heart can auto regulate blood flow based on the needs of the tissues.' Therefore, the brain and heart are preferentially perfused during early and intermediate stages of shock. If the blood pressure drops below 50 mm Hg and cerebral ischemia ensues, the collection of carbon dioxide in the brain's vasomotor center will stimulate the central nervous system ischemic response. This response yields further stimulation of the sympathetic nervous system. Alterations in level of consciousness may indicate cerebral ischemia.

Renal ResponseRenal ischemia activates the release of rernin, an enzyme stored in the kidneys' juxtaglomerular cells of the arterioles. When the kidneys do not receive an adequate blood supply, renin is release into the circulation.Renin causes angiotensinogen, a normal plasma protein, to release angiotensin 1. Angiotensin2 is then formed from angiotensin 1; the conversion to angiotensin II is enhanced by the angiotensin-converting enzyme (ACE) from the lungs where the majority of the conversion takes place. The effects of angiotensin II are:• Vasoconstriction of arterioles and some veins• Stimulation of the sympathetic nervous system• Retention of water by the kidneys• Stimulation of the release of aldosterone from the adrenal cortex (sodium retention hormone)As powerful as the renin-angiotensin mechanism is, it does take approximately 10 to 60 minutes to fully activated Decreased urinary output may be a sign of renal hypoperfusion

Adrenal Gland ResponseWhen the adrenal glands are stimulated by the sympathetic nervous system, there will be an increase in the release of catecholamines (epinephrine and norepinephrine) from the adrenal medulla. The epinephrine stimulates receptors in the heart to increase the force of cardiac contraction and increase the heart rate in order to improve cardiac output and. ultimately, improve blood pressure and tissue perfusion.

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Hepatic ResponseThe liver can store the body's excess glucose as glycogen. As shock progresses, glycogenolysis is activated by epinephrine to break down glycogen into glucose. In a compensatory response to shock, hepatic vessels constrict to redirect blood flow to other vital areas.

Pulmonary ResponseThe patient in shock may have tachypnea for two reasons: to maintain acid-base balance and to maintain an increased supply of oxygen for cells to produce energy.

Irreversible ShockUntreated shock, or shock in progressive and/or irreversible stages, will eventually cause compromises in most body systems. For example, prolonged hypovolemia will cause a decrease in arterial pressure since there is inadequate venous return, inadequate cardiac filling, and decreased coronary artery perfusion, since coronary arteries are perfused during diastole and diastolic pressure eventually falls, there will be decrease in coronary artery perfusion with a subsequent decrease in myocardial contractility.The membranes of the lysomes break down within cells and release digestive enzymes that cause intracellular damage.

NURSING CARE OF THE PATIENT IN HYPOVOLEMIC SHOCK

AssessmentA patient who arrives in the ED in profound shock because of trauma will require simultaneous assessment and interventionHISTORYRefer to Initial Assessment, for a description of general information that should be collected regarding every trauma victim.

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PHYSICAL ASSESSMENTInspection• Determine level of consciousness (LOC): A patient's LOC may progressively deteriorate. Restlessness, anxiety, or confusion may occur in shock as cerebral perfusion is diminished. After 30 to 40% of the blood volume is lost, the patient may be unresponsive to verbal and/or painful stimuli. A loss of greater than 40% of the total blood volume generally leads to unconsciousness. • Assess breathing effectiveness and rate of respirations• Identify obvious sources of external bleeding• Assess skin color Patient may be ashen or pale especially around the mouth: mucous membranes may be pale• Observe external jugular veins and peripheral veins for distention or flattening• Inspect the chest, abdomen, and extremities for signs of obvious bleeding, fractures, or major tissue injury

Auscultation• Obtain blood pressureBecause of vasoconstriction and low cardiac output, auscultated blood pressures may be difficult, obtain A Doppler Ultrasonic Flow Meter may assist with blood pressure measuremen• Auscultate breath soundsBleeding into the thoracic cavity may lead to diminished or even absent breath sounds.• Auscultate heart soundsHeart sounds may sound distant or muffled if blood collects in the pericardia] sac.• Auscultate bowel soundsThe absence of bowel sounds may indicate intra-abdominal bleeding patients in profound shock.

PercussionPercuss chest and abdomenDullness of the chest or abdomen may indicate the presence of blood. Early identification of sources of internal blood loss is essential.

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Palpation• Palpate carotid pulse• Palpate peripheral pulses• Palpate skin temperature and degree of diaphoresis

DIAGNOSTIC PROCEDURESRadiographic Studies• Chest radiograph to determine the presence of a hemothorax or pneumothorax and to assess the size of the mediastinum. Widening of the mediastinum may indicate injury to the aorta or other mediastinal vessels.• Pelvis radiograph to locate fractures, which may result in significant blood loss because of disruption of pelvic veins.• Femur radiograph, if fracture is suspected

Laboratory Studies• Venous blood sample for typing Baseline levels of the patient's hemoglobin, hematocrit, serum osmolarity, electrolytes. BUN, creatinine and serum lactate should be obtained.• Urinalysis including specific gravity• Arterial PH, PaO2, PaCO2 and base deficit

Planning and ImplementationRefer to Initial Assessment, for a description of the specific nursing interventions for patients with compromises to airway, breathing, circulation, and disability.* Adminster oxygen via a nonrebreather mask at a flow rate sufficient to keep the reservoir bag inflated during inspiration; usually requires a flow rate of at least 12 liters/minute and may require 15 liters/minute or more.Oxygen is essential for the patient in shock. Oxygen via a nonrebreather mask can deliver up to 100% with a snug fit of the mask around the nose and mouth. For the patient who requires bag-to-mask or bag-to-tube ventilation, oxygen must be delivered via a device with an appropriate oxygen reservoir.* Control any uncontrolled external bleedingRapid control of bleeding is essential to prevent the progression of shock. Control major external bleeding by direct pressure.

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* Prepare for surgery if control of internal bleeding is indicatedPrepare the patient for immediate transportation to surgery after appropriate interventions for stabilization have been instituted• Initiate intravenous replacement of fluidsPrior to the administration of blood or colloid solutions, initiate an isotonic, electrolyte-balanced, crystalloid solution via two large-bore 14- 16-gaugc intravenous catheter, lactate Ringer's solution is a "near-physiologic" solution that is similar to the body's extracellular fluid. Normal saline (0.9%) is considered the second fluid of choice for a hypovolemic patientAn initial bolus of 1 to 2 liters of lactated Ringer's solution may be given to adult patients as rapidly as possible.-The use of large-bore, short catheters, short intravenous tubing, and a rapid infusor device will contribute to rapid infusion. It is important to observe the patient's response to the bolus. by measuring blood pressure and heart rate as well as listening to breath sounds.• Initiate blood replacementPatients who do not adequately respond to a crystalloid fluid bolus are potential candidates for blood volume replacement.• Type-specific and cross matched bloodType-specific and crossmatched blood is the ideal, but may take longer to procure.• Type-specific bloodType-specific blood is usually available within minutes from blood banks.• Type O-negative packed cellsO-negative is considered the universal donor • O-positive packed cellsIf O-negative packed cells are scarce, type O-positive packed cells are sometimes used for male patients .since the risk of their plasma having anti D antibodies is remote (85% of white population and 95% of black population is Rh positive- Fresh frozen plasma (FFP). Cryoprecipitate (Factor VIII). And/or platelete administration may be considered when coagulopathy studies are known."• Administer blood through a filtering device designed to trap any clots. • Infuse blood through an intravenous line using normal saline• Warm fluids to 39 "C (102.2°F) to prevent hypothermia*• Consider auto transfusion for a patient with a hemothorax•Continue or consider application of a pneumatic antishock garment (TASG)• Position patient with legs elevated

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• Insert a gastric tube - Gastric distension may lead to vomiting and/or aspiration. • A urinary catheter provides for bladder drainage, allows for frequent monitoring of urinary output, and is necessary for any shock patient who is being prepared for surgery. Suspected injury to the urethra is a contraindication to catheterization through the urethra.• Attach leads and monitor the patient's cardiac rate and rhythm• Attach a pulse oximeter to monitor the patient's arterial oxygen saturation• Peripheral vasoconstrictors are contraindicated in a hypovolemic patient, but may be considered in patients who present in neurogenic shock with no other injuries causing hypovolenua.

Evaluation and Ongoing Assessment Additional evaluations include:• Monitoring urinary' output for response to fluid resuscitation and for overall renal function. The ability of the kidneys to form urine is a reflection of the patient's overall perfusion status.• Collaborating with other trauma team members as diagnostic studies and physical assessment identify the cause and source of hemorrhage• Monitoring temperature to determine hypothermia. Hypothermia in the patient with hemorrhagic shock has serious sequel including:• Decreased tissue extraction of oxygen from hemoglobin• Impaired cardiac contractility and decreased cardiac output• Coagulopathies because of disruption of cellular enzymatic function, platelet disturbances, and increased fibrinolysis

SUMMARYShock is a syndrome resulting from inadequate perfusion of tissues leading to a decrease in the supply of oxygen and nutrients required to maintain the metabolic needs of the body. The four types of shock are hypovolemic. cardiogenic, obstructive, and distributive. Hypovolemic shock is the most common shock in trauma patients, results from an inadequate intravascular blood volume. The organs and certain structures of the body respond to shock in a compensatory fashion. If compensatory mechanisms fail and/or treatment is not initiated, organ, tissue, and cellular ischemia ensue. Adherence to the six phases of the trauma nursing process allows for an organized approach to the assessment and management of compromises to

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airway, breathing, and circulation.

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