Med 239 Ekg Technician and Cardiology Ch 7 and 8 Review
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Cardiac monitoring
The critically sick patient may require complex monitoring during their episode of critical illness.
Monitoring tools that may exist used include:
A combination of certain or all of these tools may be required, depending on the severity of critical illness. It is vital that the nurse understands:
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Continuous ECG monitoring
It is usual for about patients who are admitted to disquisitional care units to take continuous ECG recording. This enables continuous ascertainment of heart charge per unit and rhythm, and also facilitates the setting of alarm parameters to warn of whatsoever disturbances to centre charge per unit. ECG monitoring does not supervene upon the need to take the pulse manually, as manual recordings will provide data about the forcefulness and amplitude of the pulse.
The ECG provides a graphical representation of the electrical action of the center. Monitoring electrodes are placed on the patient'due south chest, and these find the electrical activity of the middle. Activity moving towards the electrode will produce an upwards or positive deflection, whereas activity moving away from the electrode volition produce a downward or negative deflection.
The bones ECG waveform is labelled PQRST (and U) (see Figure seven.i).
Monitoring systems may be either 3-atomic number 82 systems or 5-pb systems.
The three-atomic number 82 ECG system
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Figure 7.2 Three-lead ECG electrode positioning. RA, right arm; LA, left arm.
(Reproduced from Adam SK and Osborne S, Disquisitional Intendance Nursing: science and practice, Second Edition, 2005, with permission from Oxford Academy Press.)
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Troubleshooting ECG recordings
Occasional problems may occur with the recording, and y'all may exist required to 'troubleshoot' the ECG if continual alarming or problems with the trace occur. Mutual bug and their solutions are listed in Tabular array 7.1.
Table seven.one Troubleshooting guide
| Trouble | Solution |
|---|---|
| Excessive triggering of alarms |
|
| Wandering or irregular baseline |
|
| Intermittent trace |
|
| No ECG trace |
|
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12-pb ECG monitoring
Recording a 12-lead ECG
Recording of a 12-lead ECG may be required in lodge to provide a more comprehensive view of the heart.
The 12-lead ECG is therefore composed of:
Twelve-lead ECGs may be recorded using a continuous system or may be serially recorded using a split 12-lead ECG arrangement. When serial ECGs are being recorded it is vital that the patient's electrodes are placed in the same position to let comparison. There is oft difficulty in placing the chest electrodes correctly (correct placement is shown in Effigy vii.three). The anatomical positions for chest electrode placement are described in Tabular array 7.2.
Table seven.ii Anatomical positions for chest electrode placement
| Breast atomic number 82 | Anatomical position |
|---|---|
| V1 | Quaternary intercostal space to the right of the sternum |
| V2 | Fourth intercostal space to the left of the sternum |
| V3 | Midway between V2 and V4 |
| V4 | 5th intercostal space, mid-clavicular line |
| V5 | Anterior axillary line at the level of V4 |
| V6 | Mid-axillary line at the level of V4 |
Interpretation of the 12-lead ECG
This is complex and requires appropriate preparation. Therefore 12-atomic number 82 ECGs should ever exist reviewed past a suitably qualified nurse or doctor. A systematic tool is required for the estimation of the 12-lead ECG, equally the latter needs to exist reviewed in a logical fashion.
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Blood pressure monitoring
The accurate monitoring of blood pressure is an essential chemical element of monitoring the critically sick patient. Occasionally this may be performed using not-invasive blood pressure level systems, but more than ofttimes a tranduced arterial monitoring system is used.
Non-invasive blood pressure recordings
A non-invasive organization may be used for monitoring claret pressure in the early stages of critical disease if an arterial line is not deemed advisable, or information technology may be used temporarily until an arterial line has been inserted.
Not-invasive systems are usually a reliable method of recording the patient's blood pressure, only if used frequently may cause excessive disturbance and discomfort to the patient.
Transduced arterial line recordings
Arterial lines let the continuous monitoring of the systemic arterial pressure, and also provide vascular access for arterial blood sampling. They are generally used for the majority of critically ill patients. The use of transduced arterial monitoring is essential for:
The arterial line is ordinarily situated in the radial artery, but may be located in other arteries (e.one thousand. the brachial or femoral artery). The patient should ideally undergo an Allen's test to check for adequate collateral circulation prior to insertion.
There are a number of prophylactic issues to exist noted, as there are several risks associated with arterial lines and arterial monitoring. These include:
In club to maintain the safety of the line information technology is vital to be able to:
The transducer organization
The transducer system works by transmitting pressures from the intravascular space through a fluid-filled non-compliant tube to a transducer. The transducer so converts this into an electrical point which is in plow converted past the monitor into a trace and a digital reading.
It is essential that the transducer system is consistently situated as levelled to an external reference signal to ensure authentic readings. The reference point will depend upon local policy, but it is usual to utilize either the phlebostatic axis or the sternal notch.
Once the reference bespeak has been adamant, the transducer should be zeroed prior to use and intermittently during use (frequency should be guided by local policy). Zeroing or recalibration is performed by:
Arterial waveforms
The arterial waveform should be clearly displayed on the cardic monitor at all times. The normal waveform is represented in Figure 7.iv and consists of:
The pressures generated past the arterial monitoring include:
Abnormal arterial waveforms
Variation in systolic blood pressure
Usually, there is only a minimal variation in systolic blood pressure level during inspiration and expiration despite changes that occur in intra-thoracic pressure during the animate cycle. Pulsus paradoxus is when a non-ventilated patient has more than ten mmHg drop in systolic claret pressure during inspiration equally compared to expiration. Reverse pulsus paradoxus, oft referred to every bit a 'swing' in the arterial waveform, occurs when the systolic blood pressure of a mechanically ventilated patient increases during inspiration and decreases with expiration. The well-nigh mutual cause of a variation in systolic blood force per unit area is hypovolaemia. Other possible causes include tamponade, pericarditis, large pulmonary embolus, and tension pneumothorax.
Damping
Accurate arterial blood pressure level monitoring requires a monitoring organization which is optimally damped and is confirmed past:
Overdamping and underdamping may bear upon the reliability of the continuous claret pressure results (see Table vii.3). Troubleshooting actions for a problem with damping abnormalities include:
Table 7.iii Abnormal damping of arterial waveforms
| Problem | Signs | Causes |
|---|---|---|
|
|
|
|
|
|
Removal of an arterial line
The cannula may exist removed if there are problems associated with its use (e.thousand. poor distal perfusion) or if it is no longer required. It is vital that care is taken to minimize complications associated with removal. Care should be taken to apply adequate pressure for sufficient time to ensure haemostasis.
Farther reading
Nirmalan M and Nighttime PM. Broader applications of arterial pressure wave form analysis. Continuing Educational activity in Anaesthesia, Critical Intendance and Hurting 2014; 14: 285-90.Find this resource: Romagnoli S et al. Accuracy of invasive arterial pressure monitoring in cardiovascular patients: an observational study. Critical Care 2014; 18: 644.Observe this resource:
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Central venous pressure monitoring
The central venous pressure (CVP) is recorded by using a central line that is normally inserted into either the internal jugular vein or the subclavian vein.
The tip of the line is situated in the superior vena cava and reflects the pressure in the right atrium. It is theoretically suggested that in a good for you patient this provides information about intravascular blood volume and right ventricular end diastolic pressure, although a recent meta-analysis questions the reliability of this.1 See p. [link].
Nevertheless, the CVP may exist used equally a guide to handling, but it is of import to remember that no single measurement should exist used to guide patient treatment. An overview of the trend in the patient'south assessment results is much more likely to exist clinically useful in relation to guiding fluid direction.
At that place are a number of safety issues to exist noted, as there are several risks associated with CVP monitoring, and complications may occur in upward to 15% of patients. These include problems during insertion, such as:
Problems may as well be noted after insertion. These include:
Transducing the CVP
Information technology is essential that the transducer organization is adequately zeroed to an external reference bespeak to ensure accurate readings. The reference signal volition depend upon local policy, but it is usual to use either the phlebostatic axis or the sternal notch.
Once the reference point has been determined the transducer should be zeroed prior to use and intermittently during apply (frequency should be guided past local policy). Zeroing or recalibration is performed by:
CVP values and waveforms
Normal CVP is considered to exist in the range 2–10 mmHg (positive pressure ventilation and addition of PEEP will increase CVP values).
The normal waveform consists of an A, C, and V wave (see Figure seven.5). Each of these waves represents a different part of the cardiac cycle.
The CVP may exist altered by changes in the patient's status, but it is important that these are viewed aslope other clinical information from the CVS assessment.
Conditions that may cause CVP to rise include:
Conditions that may cause CVP to fall include:
Removal of a CVP line
Information technology may exist necessary to remove the CVP line in lodge to supervene upon it if there are signs of infection. A new line will need to exist inserted prior to the removal of the old line if vasoactive or other infusions are utilizing the CVP line. The patient may also no longer require the line.
It is vital that no complications arise from the removal of the CVP line. Therefore, if the patient'southward condition permits, the procedure should be performed as follows:
Reference
1 Marik PE and Cavallazzi R. Does the central venous force per unit area predict fluid responsiveness? An updated meta-analysis and a plea for some common sense. Disquisitional Care Medicine 2013; 41: 1774–81. Find this resource:
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Cardiac output monitoring
The last decade has seen a significant increase in the number of cardiac output measurement tools bachelor in critical intendance units. Some units may apply a variety of systems, whereas in others in that location may be only one tool or a limited range bachelor. Dissimilar cardiac output systems will provide additional information to estimation of cardiac output. The choice of cardiac output measurement tool is dependent on:
For decades the pulmonary artery catheter has been regarded as the gold-standard tool for cardiac output monitoring. However, increasingly a diverseness of other tools are beingness utilized to measure cardiac output. Many of the newer systems are less invasive than traditional methods. The critical intendance nurse may use systems such as the following:
Pulmonary artery (PA) catheter
This is used to measure cardiac output, and also provides other measurements that may be useful in clinical do. The pulmonary artery catheter is situated in the right side of the heart and enters the pulmonary artery. It is therefore able to measure out:
Cardiac output is measured using thermodilution. Other variables are also calculated, including:
The pulmonary artery catheter typically consists of four lumens.
Insertion of a PA catheter
The nurse's part is to assist with insertion, and a strict aseptic technique is required. The catheter is inserted through a large vein (subclavian or internal jugular vein). The catheter is advanced through the right side of the heart into the pulmonary artery and somewhen into the 'wedged' position. The nurse may need to observe the monitor during insertion to advise about waveform alterations and monitor for signs of cardiac arrhythmias. Information technology is important that the airship is deflated after insertion, and that the line is secured firmly to the patient.
Complications related to PA catheter insertion and use include:
Measuring cardiac output
Thermodilution
Older pulmonary avenue catheter systems determine cardiac output by thermo dilution.
Thermofilament
Newer pulmonary artery catheter systems allow for continual cardiac output monitoring without the need for insertion of cold fluid.
Measurement of pulmonary avenue occlusion pressure
It may be necessary for PAOP (wedge pressure level) to exist measured from time to fourth dimension, as this provides an indication of left atrial pressure and indirectly reflects left ventricular end diastolic pressure. This measurement is obtained by inflation of the balloon, and is best recorded at the cease of expiration. It is essential that the correct technique is used.
Normal values for PA catheter measurements
Pulse contour analysis
The pulse contour organisation allows cardiac output studies to be recorded without the need for additional line insertion. The system is able to record continuous cardiac output by using data from the pulse profile of the arterial trace. Therefore cardiac output studies can be recorded without using additional monitoring lines such equally a PA catheter.
However, some pulse contour systems do require the use of thermodilution techniques to recalibrate the arrangement to ensure that the data provided are authentic. Some systems apply pulmonary thermodilution to recalibrate the calculation organization, and will therefore provide some continuous data and some 'one-off' measurements that are utilized to summate other variables.
Considering in that location is no necessity for a PA catheter, some of the measurements traditionally associated with PA studies cannot exist recorded (e.g. PAOP). Withal, other variables that can have an impact on treatment plans can be recorded. Therefore data from pulse contour analysis differ from those produced by other cardiac output measurement systems.
Pulse contour variables that can exist measured or calculated include:
In improver, some pulse contour systems utilize transpulmonary thermodilution to provide the following variables:
The equipment required for studies using pulse contour systems varies depending upon the manufacturer. The 2 main systems are:
FloTrac©system
Normal values can be found in the user manual for each organisation.
These systems provide additional data, and the normal values for the additional measurements are listed in Table vii.4.
Tabular array vii.4 PiCCO© and FloTrac© data variables
| Measurement | PiCCO© | FloTrac© |
|---|---|---|
| Stroke volume variation | < 10% | < 13% |
| Intravascular blood volume | 800–1000 mL/m2 | — |
| Extravascular lung water | three–7 mL/kg | — |
| Cardiac part index | four.5–6.v L/min | — |
| Global end diastolic book | 680–800 mL/yardii | — |
| Stroke volume index | — | 33–47 mL/shell/k2 |
| Cardiac index | 3–5 L/min/m2 | 2.5–four 50/min/k2 |
Lithium dilution cardiac output
This method utilizes the injection of lithium chloride to calculate the cardiac output.
The system is besides able to generate continuous cardiac output by utilizing pulse power derivation, and is not dependent upon waveform morphology to calculate continuous cardiac output measurements.
Cardiac output is measured using the following equation:
Information technology is therefore essential to measure the patient'southward packed cell volume (PCV) to enable accurate measurements to be obtained.
Because the organization utilizes the injection of lithium chloride to summate the cardiac output, some precautions are necessary. These include:
The system has shown a skilful correlation with PA catheter thermodilution as long every bit at that place is no indicator loss and there is good claret period. Repeated blood sampling of 3–iv mL of blood is needed, and concerns have been raised well-nigh the need for this in a critically ill patient.2
Variables calculated from the lithium dilution arrangement (LiDCO©) are listed in Table seven.v.
Table 7.five LiDCO© data variables
| Systolic pressure variation |
|
| Pulse pressure variation |
|
| Stroke book variation |
|
| Stroke volume index | 3.3–four.7 mL/m2/beat |
| Left ventricular stroke work | 58–104 gm/m/vanquish |
| Right ventricular stroke work | eight–16 gm/m/shell |
| Coronary artery perfusion pressure | 60–fourscore mmHg |
| Right ventricular end diastolic volume | 100–160 mL |
| Right ventricular cease systolic volume | 50–100 mL |
| Right ventricular ejection faction | forty–sixty% |
Doppler cardiac output measurement
Cardiac output can also exist estimated by using Doppler ultrasound to measure claret period through the aorta, and utilizing this to summate cardiac output. Mostly most systems employ a probe placed into the patient's oesophagus to measure blood menstruum in the descending aorta. Some systems are externally placed (truly non-invasive), and are positioned suprasternally to allow calculation or measurement of flow. However, the oesophageal probe is used most oft. This system requires no invasive lines and can be utilized in areas exterior of disquisitional care by experienced practitioners such every bit disquisitional intendance outreach teams.
The systems work past measuring ultrasound waves that are reflected off moving red blood cells.
For the organisation to piece of work accurately it is essential that the Doppler probe is positioned correctly and that the waveform produced past the Doppler is sharp and well defined. Doppler measurement is useful for most patients. Notwithstanding, caution is needed in the following situations:
Reference
2 Drummond KE and Murphy E. Minimally invasive cardiac output monitors. Continuing Educational activity in Anaesthesia, Disquisitional Care & Pain 2012; 12: 5–10.Discover this resources:
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Vasoactive medications
The diverse monitoring tools discussed in this chapter highlight the need to dispense blood force per unit area by using vasoactive medication. Therefore a knowledge of vasoactive drugs and their indications, contraindications, and mechanisms of activeness is essential for the disquisitional care nurse.
A vasoactive medication is one that is by and large used when fluid manipulation in the critically sick patient is unsuccessful. Put simply, a vasoactive medication may be defined as a drug that has the ability to change the bore of a blood vessel. However, many vasoactive medications likewise have a direct event on other elements of the cardiac arrangement, so information technology is perhaps more appropriate to consider all of the effects of vasoactive medication. These include:
These categories can be summarized as follows:
The effects of vasoactive medications are predominantly mediated past the medication binding to a receptor that causes the issue. These include α- and β-receptors, and information technology is important to note that medications may bind to more than one type of receptor. The main receptor sites and effects are listed in Table 7.6.
Table vii.6 Receptor sites and effects
| Receptor | Location | Action |
|---|---|---|
| α1 |
|
|
| α2 |
|
|
| β1 | Heart |
|
| βii |
|
|
| Dopaminergic | Vascular smoothen muscle | Renal and splanchnic vasodilator |
The most common vasoactive medications used in disquisitional illness include:
Each of these drugs will bind to one or more than receptors, and this will upshot in changes to vasomotor tone, contractility of the centre muscle, and speed of contraction and thus heart rate. Table 7.7 lists the receptors for each of these primal medications. Further information near each of these drugs is provided after in this affiliate.
Table 7.7 The consequence of vasoactive medications on receptors
| αi-receptor | β1-receptor | β2-receptor | Dopaminergic receptor | |
|---|---|---|---|---|
| Adrenaline | ++ | +++ | ++ | 0 |
| Noradrenaline | +++ | ++ | 0 | 0 |
| Dobutamine | 0 | +++ | + | 0 |
| Dopexamine | 0 | ++ | +++ | + |
| Dopamine | ||||
| Low dose | 0 | 0 | +++ | |
| Moderate dose | 0 | ++ | + | 0 |
| Loftier dose | +++ | +++ | 0 | 0 |
Vasoactive medications may crusade side effects, and information technology is important that the benefits of the medication are non outweighed past its side furnishings. Side effects may be dose dependent and include:
Overview of specific vasoactive medications
Noradrenaline
Adrenaline
Dobutamine
Dopexamine
Dopamine
Reference
3 Dellinger R et al. Surviving sepsis campaign: international guidelines for management of severe sepsis and septic stupor. Critical Care Medicine 2013; 41: 580–637.Find this resource:
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Intra-aortic balloon pump
An intra-aortic balloon pump is a mechanical device that sits in the aorta and is used equally a temporary measure out to support acute heart failure.
The intra-aortic balloon pump uses counter pulsation to support the failing heart—that is, the airship inflates during diastole and deflates during early on systole. This causes volume deportation of blood within the aorta both proximally and distally. The volume displacement increases coronary blood flow and has the potential to subsequently meliorate systemic perfusion past increasing cardiac output.
The purposes of the balloon pump are to:
It is ordinarily used to support patients:
Intra-aortic balloon pumps are contraindicated in:
The timing of the counter-pulsation therapy is disquisitional, equally it is vital that the airship inflates after the aortic valve has closed and deflates before the opening of the aortic valve. Timings are ordinarily coordinated by using either the ECG complex or the arterial waveform. Suboptimal timing of the counter-pulsation therapy can lead to haemodynamic instability. Therefore it is essential that the panel is ready correctly by an adept practitioner.
Nursing care for the patient with an intra-aortic balloon pump involves:
Side effects include:
The device is normally removed once the patient is more than stable. This may be indicated by a decreasing need for inotropic back up and improved cardiac output. Information technology is important that the intra-aortic balloon pump is gradually weaned, and the device should never be abruptly stopped as this may lead to thrombus formation.
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Pacing
Cardiac pacing is ordinarily indicated when at that place are cardiac conduction problems. These may be related to cardiac ischaemia or damage, or may be linked to other aspects of critical illness.
Pacing is ordinarily used:
Most pacing in critical care is of a temporary nature, although occasionally permanent systems may exist required. Temporary pacing units ordinarily consist of:
Pacing systems may be:
Transvenous pacing
Epicardial pacing
Overriding arrhythmias
Occasionally pacing may be used to 'override' fast arrhythmias. This involves the doctor setting the pacemaker to a faster rate than the patient's tachycardia (unremarkably 10–15 beats/min faster). It may exist used to suppress supraventricular tachycardia, atrial flutter, and ventricular tachycardia. However, it is not constructive in suppressing atrial fibrillation or sinus tachycardia.
Source: https://oxfordmedicine.com/view/10.1093/med/9780198701071.001.0001/med-9780198701071-chapter-7
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