N320 EXAM 2

Countershock

the use f electric current that is delivered to the heart to reset a heart rhythm

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Elective cardioversion

for of countershock that delivers an electrical current that is synchronized with the patient’s heart rhythm. Treats SVT, a-fib, a-flutter and ventricular tachycardia

Defibrillation

an emergency procedure used to treat ventricular tachycardia in a pulseless patient or ventricular fibrillation

Pacemaker

pulse generator used to provide an electrical stimulus to the heart when the heart fails to conduct or generate impulses on its own at a rate that maintains cardiac output.

Components of pacemaker

internal pulse generator and the leads

External pacemaker

temporary measure that delivers electric impulses to the myocardium transcutaneoulsy through two electrode pads

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Epicardial pacemaker

temporary pacemaker and used for open heart surgery. Pacing leads attached outside surface of the heart (epicardium) and the pacemaker is placed in the abdomen

Tranvenous pacemaker

temporary pacemaker that is achieved though electrical stimulation of the right ventricular or right atrial endocardium (inner most heart layer) by an electrode tipped catheter. Pacing lead attached to the inside surface of the heart and the pacemaker is placed in the shoulder area

Firing

refers to the pacemaker generating an electrical impulse that causes the heart muscle to contract and pumps blood through body

Capture

ability of the pacemaker to generate an electrical impulse that successfully triggers a contraction of the heart muscle

Sensing

ability of the pacemaker to detect the heart’s natural electrical activity and adjust its own electrical impulses accordingly

3 letter pacemaker code

1st letter: chamber(s) of the heart being PACED

2nd: chamber(s) of the heart. being SENSED

3rd: pacing mode ( inhibited, triggered, dual)

Inhibited pacemaker action

pacemaker is programmed to not deliver an electrical impulse IF the heart is beating on its own

Triggered pacemaker action

Pacemaker delivers an electrical impulse IN response to a sensed even such as a heart beat (Upon sensing intrinsic atrial activity, the pacemaker stimulates the ventricle after a time delay in order to mimic the physiological delay in the AV node)

Name the 7 possible pacemaker malfunctions

1. Failure to sense
2. failure to capture
3. failure to fire
4. over-sensing
5. under-sensing
6. pacemaker mediated tachycardia
7. lead fracture or dislodgment
8. pacemaker battery failure

Implantable cardioverter/defibrillator

fully implantable, battery operated system designed to recognize and terminate ventricular tachyarrhythmias that can be cause sudden death

Indications for ICD

1. prior aborted cardiac death
2. proven sustained tachycardia
3. prophylaxis for indiv. with some forms of cardiomyopathy

Hypothermia after cardiac arrest

basically to reduce brain damage by reducing the amount of oxygen the brain requires (slows down metabolism) GOAL: 32-34 degree celsius

Nursing concern when cooling patient

1. dysrhythmias
2. HYPOKALEMIA
3. HYPOTENSION
4. HYPERGLYCEMIA

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Nursing concerns when rewarming patient

1. HYPERKALEMIA
2. HYPOTENSION
3. HYPOGLYCEMIA

rewarm no more than 0.5-1 degree celsius PER hour

Cardiac output

the amount of blood pumped by the heart EACH minute

NORMAL: 4-8 L/min

What are the 4 determinants of cardiac output

1. heart rate
2. preload
3. contractility
4. afterload

Heart rate

the number of times the heart beats within a certain time period, usually a minute.

Stroke volume

the amount of blood ejected by each heart beat

Preload

the pressure or STRETCH exerted on the walls of the ventricle at the end of ventricular filling (diastole)

Afterload

the resistance to ventricular contraction. The pressure the ventricle must overcome to open the aortic or pulmonic valve and eject blood out of the ventricle into either the systemic (left) or pulmonary system (right)

Contractility

the property of myocardial muscle fibers that allows them to shorten

Right atrial pressure

an estimate of right ventricular preload

NORMAL 2-6

Pulmonary artery pressure (PAP)

reflects both right and left heart pressure

Pulmonary artery systolic pressure (PAS)

reflects the highest pressure generated by the right ventricle during systole (contraction)

NORMAL 20-30 mmHg

Pulmonary artery diastolic pressure (PAD)

reflects the lowest pressure within the pulmonary artery

NORMAL 8-15 mmHg

Pulmonary artery wedge pressure (PAWP)

reflects LEFT end-diastolic, which is a measure of preload in the left ventricle

Systemic Vascular resistance (SVR)

an estimate of left ventricular afterload

Pulmonary vascular resistance (PVR)

an estimate of right ventricular afterload

Left ventricular stroke volume (LVSWI)

represents the pressure the heart beats against and the volume the ventricle must pump forward (PAWP)

Right ventricular stroke volume index

the amount of work involve in moving blood in the right ventricle with each beat

Cardiac index

measured as a more accurate hemodynamic indictor of CO because it related CO to the patients body size

NORMAL 2.4-4 L/min/m2

Central venous pressure

an indicator of central blood volume

What are the five factors that affect diffusion

1. partial pressures
2. gas gradient
3. lung surface area
4. alveolar capillary thickness
5. length of gas exposure in the lungs

BONUS: oxyhemoglobin dissociation curve

Pulmonary perfusion is altered by these factors

1. cardiac output
2. gravity
3. ventilation-perfusion relationship
4. pulmonary shunts
5. pulmonary vascular resistance

Normal ranges for ABG

PaO2: 95-100

pH: 7.35-7.45

PaCo2: 35-45

HCo3: 22-26

Capnography

noninvasive graphic display of CO2 that is exhaled by the patient during breathing

Colorimetric capnography

used pH sensitive paper that changes color based on the patients exhaled pH to represent a range of end tidal Co2

Minute Ventilation

total volume of air expired in 1 minute

frequency of breaths x tidal volume

NORMAL 5-10 L/min

Ways to assess endotracheal placement

1. auscultation
2. chest x-ray
3. capnography
4. ultrasound
5. physical examination

Weaning patients of mechanical ventilation tests (6)

1. Tidal volume
2. Respiratory rate
3. negative inspiratory force
4. Vital capacity
5. maximum voluntary ventilation
6. ABGs

Continuous mandatory ventilation

mechanical ventilation where all of the patient's breaths are being provided by the ventilator

Assist/Control (A/C)

Each breath is either assisted (patient initiated) or controlled (ventilator initiated). Every breath is supported

Synchronized intermittent mandatory ventilation (SIMV)

Guarantees a set rate of breathing, but the patient can breathe above the set rate. Only the ventilator initiated breaths are supported

Continuous positive airway pressure (CPAP)

delivers constant small amount of positive pressure throughout the respiratory cycle. May be delivered via vent or facemask. Often used with sleep apnea. CPAP essentially delivers a little bit of PEEP

Pressure support ventilation (PSV)

used to assist spontaneous breathing, decreases work of breathing (for weaning pts)

Positive end expiratory pressure (PEEP)

the establishment and maintenance of present airway pressures greater than ambient at end of exhalation. Basically it keeps the airways and small lung spaces open to allow for adequate oxygenation when a person cannot breathe on their own