Signs of volume overload – dyspnea, the presence of rales or crackles, pulmonary edema, increased jugular venous pressure and pitting edema of the ankles – may indicate a problem with increased preload. Medical interventions include a drug regimen of first line drugs – morphine, furosemide (Lasix), nitroglycerine and if necessary second line drugs like dopamine and Dobutamine. Morphine, in addition to relieving pain and anxiety, dilates peripheral vessels. This action redistributes blood, which pools in dependent areas, such as the legs, especially if the patient dangles his legs or has the head of the bed elevated. Pooling decreases the volume returned to the heart, which subsequently reduces the volume that a failing ventricle must manage. If the failing left ventricular ineffectively empties its contents, it can accept less blood from the pulmonary circulation, leading to blood pooling in the lungs, which can precipitate pulmonary edema. The dose of morphine, usually from 2 mg to 10 mg intravenously, is titrated according to the patient’s response. Some patients may experience hypotension due to arterial and venous dilation from only small doses, while others may require repeated high doses to achieve a therapeutic effect. Show Furosemide is an effective diuretic that diminishes total body blood volume by boosting urine output, as long as the heart works well enough to perfuse functioning kidneys. The initial recommended dose is 0.5 to 1.0 mg/kg by slow IV injection. Customary IV doses range from 20 mg to 40 mg, although the amount may be as much as 100 mg in emergencies. Blood pressure needs careful monitoring when administering IV diuretics especially when given to patients who already have hypotension. These patients may need additional medications to support blood pressure during diuresis. Electrolyte monitoring is also critical. Reduced serum magnesium and potassium may cause significant heart rhythm disturbances. Nitroglycerin, like morphine, produces venous dilation, redistributing blood volume to the peripheral areas and pooling blood away from the heart. Nitroglycerin is also effective in relieving cardiac chest pain because while it lessens the workload of the heart, it reduces cardiac muscle oxygen requirements. Additionally, higher IV nitroglycerin doses enhance oxygen delivery by improving circulation through the coronary arteries. Sublingual nitroglycerin is mainly a vasodilator that reduces preload in patients who take it for angina, whereas IV nitroglycerin in higher doses causes an arterial dilating effect reducing ischemia. Dopamine, a precursor of norepinephrine, administered as a continuous infusion, affects preload by causing vascular constriction or dilation through its effect on the sympathetic nervous system. Its effect is dose dependent. Low-dose dopamine, 2 mcg/kg/min to 4 mcg/kg/min has peripheral vasodilating effects but causes little or no increase in renal perfusion or force of myocardial contraction (positive inotropy) as previously thought. However, it may promote diuresis, which would decrease preload, as would its vasodilating effect. Because dopamine at this dose range has no direct effect on blood pressure, look for other causes, such as vascular volume depletion, anxiety, and pain if a patient receiving this drug has fluctuations in pressure. Moderate-range doses between 5 mcg/kg/min and 10 mcg/kg/min directly improve preload by causing venous constriction and increasing myocardial contractility through sympathetic stimulation. If a patient has acute pulmonary edema, dopamine is a second line treatment when the patient’s blood pressure is 70 mmHg to 100 mmHg and signs and symptoms of shock are present. Systemic and splanchnic (gut) vasoconstriction occurs when dopamine’s dose exceeds 10 mcg/kg/min. The risk of both myocardial and peripheral ischemia is greater as the dose increases. The need for supplemental oxygen should be evaluated, all chest pain promptly treated and peripheral perfusion indicators such as pulses and urine output closely monitored. Tachycardia may also be an adverse effect and for a patient who has coronary heart disease, the combination of increased contractility and tachycardia may significantly worsen ischemia. Dobutamine, a synthetic catecholamine, is also administered as continuous IV infusion and is indicated for the treatment of acute pulmonary edema when blood pressure is > 100 mmHg and signs of shock are absent. It is also used to treat severe systolic heart failure. Its effects are dose dependent. Dobutamine increases myocardial contractility and heart rate, decreases left ventricular preload, and indirectly causes a peripheral vasodilatation further enhancing the reduction in preload. It is usually administered at 5 – 20 mcg/kg/min. Doses greater than 20 mcg/kg/min increase the risk for myocardial ischemia due to the oxygen demand of a higher heart rate.
Don appropriate personal protective equipment (PPE) based on the patient’s signs and symptoms and indications for isolation precautions. The transducer system must be leveled and zeroed to provide accurate hemodynamic values. Route tubes and catheters having different purposes in different, standardized directions (e.g., IV lines routed toward the head; enteric lines toward the feet).undefined#ref4">4 OVERVIEWTransducer systems provide a catheter-to-monitor interface so intravascular and intracardiac pressure can be measured. The transducer detects a biophysical event and converts it to an electronic signal. Fluid-filled pressure monitoring systems used for bedside hemodynamic pressure monitoring are based on the principle that a change in pressure at any point in an unobstructed system results in similar pressure changes at all other points in the system. Intravascular and intracardiac pressure transducers detect the pressure generated in various areas of the cardiovascular system and convert that pressure wave into an electrical signal, which is transmitted to the monitoring equipment for representation as a waveform on the oscilloscope. Invasive measurement of intravascular (arterial) pressure requires insertion of a catheter into an artery. Invasive measurement of intracardiac (right atrial [RA] and pulmonary artery [PA]) pressure requires insertion of a catheter into the PA. A single-pressure transducer system is used to measure pressure from a single catheter (e.g., arterial or central venous) (Figure 1). A double-pressure transducer system is used to measure pressure from two catheters (e.g., arterial and central venous) or two ports (e.g., PA and RA) from a single catheter (e.g., PA catheter) (Figure 2). A triple-pressure transducer system is commonly used to measure pressure from the arterial and PA catheters (Figure 3). With this system, arterial pressure, PA pressure, and RA pressure can be obtained. All hemodynamic values (PA, RA, and arterial) are referenced to the level of the atria. The external reference point of the atria is the phlebostatic axis. Labeling the tubing reduces the chance of misconnection, especially in circumstances where multiple IV lines or devices are in use.3 Connections should not be forced, and equipment should only be used for its intended purpose.6 Forced connections or workarounds could indicate that the connection should not be made. EDUCATION
ASSESSMENT AND PREPARATIONAssessment
Preparation
PROCEDURE
Disposable Pressure Transducer System Setup
Monitor Setup
Leveling the Transducer
Zeroing the Transducer
Fast-flush Square Wave Test
Completing the Procedure
MONITORING AND CARE
EXPECTED OUTCOMES
UNEXPECTED OUTCOMES
DOCUMENTATION
REFERENCES
Adapted from Wiegand, D.L. (Ed.). (2017). AACN procedure manual for high acuity, progressive, and critical care (7th ed.). St. Louis: Elsevier. AACN Levels of Evidence
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