Nursing Care and Hemodynamic
Whats Is Hemodynamic monitoring
Hemodynamic
monitoring is the use of advanced technology and application of physiological
principles to clinically assess the cardiac function and circulatory system in
critically ill patients.
The pulmonary artery catheter was first introduced in
1970 by Dr. Jeremy Swan (Swan et al., 1970), and continues to be a frequently
used tool in the critical care setting. The catheter tip is positioned in the
distal pulmonary artery and is used to monitor pulmonary artery systolic,
diastolic, and mean pressures, and to obtain blood samples to determine mixed
venous oxygenation.
The distal balloon port is used to measure the pulmonary
artery wedge pressure (PAWP) when the balloon port is inflated with 1.5 cc of
air. Additional hemodynamic parameters and data are obtained from other ports
and lumens of the catheter, such as right atrial pressure, cardiac output
measurements, blood (core) temperature, and saturation of venous oxygenation
(SVO.)
Invasive Methods of Blood Pressure Monitoring
Using
data obtained at the bedside from the pulmonary artery catheter and other
physiologic indices such as cardiac output, heart rate, preload, afterload, and
contractility, critical care nurses and physicians are able to make rapid
assessments and determinations about the clinical status of the critically ill
patients.
The catheter enables clinicians to assess ventricular function,
diagnose complications following acute myocardial infarction, differentiate
shock states, cardiac and pulmonary disorders, manage high-risk cardiac
surgical patients, and monitor unstable patients with complexities such as
sepsis and multiple organ dysfunction.
The original balloon-tipped,
flow-directed thermodilution catheter has evolved since 1970 and has added
enhancements such as saturation of venous oxygenation (SVO), right ventricular
volumes and ejection fraction, continuous monitoring of cardiac output, and
intracardiac atrioventricular sequential pacing.
Digital Non Invasive Methods of Blood Pressure Monitoring
Newer
technologies to monitor cardiac output using noninvasive methodology include
the Esophageal Doppler monitor and the Exhaled Carbon Dioxide (CO) monitor, The
Esophageal Doppler monitor measures cardiac output via a probe placed within at
nasogastric tube that measures aortic blood flow, enabling the clinician to
assess stroke volume and heart rate adjusted cardiac output.
A second technology,
Exhaled CO₂, is a noninvasive method of cardiac output monitoring that measures
blood flow from exhaled CO; using a modified Fuck Equation. Its clinical
application is limited to the operating room setting since the technology
requires measurement of blood flow from exhaled CO.
Under controlled
ventilation but it has great potential for the future when the technology can
be used for different modes of mechanical ventilation with or without
spontaneous breathing. Examining the impact of these new technologies may have
on patient outcomes is an important area for future nursing research.
Hemodynamic Monitoring and Nursing Care
Hemodynamic
monitoring has great relevance to nurses in critical care because of the
important role it plays in the care of critically ill patients. Critical care
nurses are responsible for continuous monitoring, interpretation, and trending
of hemodynamic indices and for communicating critical information to physician
colleagues.
Understanding the implications of subtle changes in pressures and
parameters will directly impact a patient’s response to complex therapeutic
interventions such as fluid administration and manipulation of vasoactive
drips. Utilizing research to examine existing practices and to change practice
is vital to ensure research-based practice and positive patient outcomes.
Nursing Focus While Monitor Hemodynamics of Patient
The
majority of nursing research on hemodynamic monitoring has been focused on the
technical and clinical variables affecting accuracy of pulmonary artery
pressure monitoring. Because many variables affect accuracy, this topic is
particularly relevant for nurses caring for critically ill patients.
The
standard in critical care has traditionally been to reference (level the
air/fluid interface stopcock at the phlebostatic axis) and zero the catheter
system a minimum of once per shift and at times more often, to offset zero
drift, and to ensure accuracy.
The results of one nursing study suggested that
zeroing disposable transducers may be required only once during hemodynamic
monitoring, before initial readings are obtained (Ahrens, Pennick , &
Tucker, 1995).
These findings encourage practitioners to reevaluate a long-held
critical care nursing standard and demonstrate the value of keeping pace with
new technology. Replication studies are needed in this area to validate this
practice.
Why Hemodynamic Monitoring Is Important In Nursing
A
major focus in recent nursing research has been to study hemodynamic pressures
in various backrest elevations. There is considerable nursing research
supporting accurate and reliable measurement of hemodynamic pressures in
backrest elevations from 0° to 60° if the air/fluid interface (zeroing
stop-cock) is leveled or referenced at the phlebostatic axis.
Lateral
positioning may be used if the air/fluid interface is leveled at the
phlebostatic axis, but the patient must be at a 90° side position with the
backrest flat to ensure accuracy. The phlebostatic axis in the right lateral
90° position is the fourth intercostal space at midsternal, compared to the
fourth intercostal space at the left sternal border in the left lateral 90°
position ( Paolella , Dorfman, Cronan , & Hasan, 1988) .
The question of
accuracy and reliability of measurements in lateral positioning other than 90°
has been the subject of two recent nursing studies. In one study, pulmonary
artery (PA) pressures were obtained with patients in the 60° lateral position
(Aitken, 2000). The dependent mid-clavicular line at the level of the fourth
inter costal space was used as the zero-reference level.
Statistically
significant differences were found and the author concluded that PA pressures
cannot be obtained with patients in the 60° lateral position. Another group of
researchers studied the effect of 30° lateral recumbent position on PA and PAWP
pressures (Bridges, Woods, Brengelmann, Mitchell, & Laurent-Bopp, 2000).
Using an angle-specific left atrial reference point, the investigators found a
statistically significant difference between measurements of PA pressures with
the patient supine and those obtained in 30° lateral position.
Mean differences
were small and the author considered the measures clinically equivalent to
those of patients in supine position. The optimal reference point for lateral
positions other than 90° with backrest flat continues to be an area that will
require further study and validation in future research studies.
Recent
studies have examined cardiac output technology in patients with low cardiac
output. Continuous cardiac output technology was found to be more precise than
measurements using the bolus technique in one study of patients with
low-cardiac output (Albert, Spear, & Hammel, 1999).
The practice of using
room-temperature injectate versus iced solution was supported in another study
examining traditional thermodilution methods of cardiac output in patients with
low cardiac output (Kiely, Byers, Greenwood, Carroll, & Carroll, 1998).
To
ensure accuracy and reliability, all he myodynamia pressures are read at end
expiration in ventilated patients as well as those breathing spontaneously.
Numerous studies continue to support the use of a strip chart recorder to
provide more reliable and accurate hemodynamic readings than do digital data
(directly off the monitor) in both ventilated and spontaneously breathing
patients.
Since
the advent of the pulmonary artery catheter, technology in hemodynamic
monitoring has advanced at a rapid pace. Future studies must continue to keep
pace with the ever changing technology.
Technical difficulties in measurement,
as seen in patients with severe respiratory variation, in ventilated patients
on high levels of positive end expiratory pressure (PEEP), and in the presence
of large “y” waves on the hemodynamic waveform, are examples of
clinical issues that continue to confound critical care nurses.
Critically
evaluating the use of both new and traditional technology is essential to the
provision of good patient care.The
potential risk versus benefit of pulmonary artery catheterization is an
important ethical consideration in hemodynamic monitoring.
Questions have been
raised within major medical journals and the media about the safety and
efficacy of pulmonary artery catheterization. As a result of the controversy,
organizations such as the Society of Critical Care Medicine have intensified
efforts to conduct large randomized controlled trials to critically evaluate
the safety and effectiveness of PA catheters in critically ill patients.
The
results of studies on the clinical competency of critical care nurses’
knowledge of PA catheters have been less than impressive, and underscore the
need to provide ongoing training and competency assessments of nursing staff to
ensure safe and quality patient care. Hemodynamic monitoring is a valuable tool
if used judiciously by specially trained and competent medical and nursing
professionals.