Sonographer And Contrast Agent
The impact
of contrast agents (transpulmonary and agitated saline) on the clinical
applications of echocardiography has been dramatic over the last
decade.Currently, the Food and Drug Administration approved indications for
transpulmonary agents include the enhancement of left ventricular endocardial
border definition.The augmentation of Doppler signals and intracardiac shunt
detection can also be enhanced with the administration of contrast agents. The
use of contrast agents in each of these clinical situations is well established
and has become standard practice in many echocardiography laboratories. The development of newer agents promises to
bring additional advances in the utility of contrast echocardiography,
including the real-time assessment of myocardial perfusion coronary flow
detection and flow reserve measurements the delivery of pharmacologic or
genetic therapy and in combination with continuous ultrasonography, as a
therapy for discriminatingly dissolving life-threatening blood clots. As these
applications continue to expand, so must the role and responsibilities of the
cardiac sonographer.
Contrast
echocardiography requires a high level of competence and expertise, in addition
to the skills frequently required in standard cardiac sonography practice, such
as assisting with transesophageal echocardiography and performing stress
echocardiography, interventional and/or interoperative procedures, and fetal
echocardiography. The American Society of Echocardiography (ASE) highly
recommends that cardiac sonographers take the appropriate steps to become
trained in the administration of the contrast agents used in
echocardiography.The sonographer is often the first person to recognize the
need for contrast, but the physician is ultimately responsible for ordering its
use, which ideally should be done on a case-by-case basis. However, we
recognize that there are situations in which the physician is not immediately
available, and in such instances, another option might be the use of standing
orders,with explicit indications listed as to when to use a contrast agent.This
alternative would require active involvement of the laboratory medical director
for the development of standing orders and specific protocols.
The cardiac
sonographer’s role in performing contrast echocardiography consists of 4
components:
1. A
thorough understanding of microbubble physics, instrumentation, and the
application of cardiac ultrasonographic scanning techniques for the acquisition
of high-quality images during contrast administration.
2.
Recognition of the indications for use of a contrast agent for left
heart-chamber border delineation, enhancement of Doppler signals, and
intracardiac/intrapulmonary shunt detection.
3.
Obtainment of intravenous (IV) access or evaluation of an existing IV line for
administration of a contrast agent by a sonographer.
4.
Performance of the IV injection or the infusion of the contrast agent.
It is
recognized that, given the variety of practice situations, some of these components
(ie, [3] and [4]), may not necessarily be a part of the sonographer’s
responsibilities. However, in the interest of providing a timely patient
diagnosis especially in situations in which the test results will affect the
patient’s clinical management, a qualified cardiac sonographer can determine
the need for a contrast agent and, if necessary, establish IV access and even
potentially administer a contrast agent.This may be the case if the physician
or a registered nurse is not present but is available in the immediate area and
can provide direct supervision for the insertion of an IV line or for the
administration of the contrast agent. It is preferable that a physician and/or
a nurse have direct involvement with a contrast study because the sonographer
cannot administer a contrast agent (ie, bolus injections) and simultaneously
perform a quality echocardiographic examination without additional support.
All persons
involved in contrast echocardiography must be well trained and demonstrate
competency. Cardiac sonographers need to be credentialed in their respective
discipline (adult and/or pediatric). Importantly, when direct supervision by a
physician or registered nurse is available and established, and when written
laboratory protocols are in place, a credentialed sonographer can initiate the
process, obtain IV access, and have a registered nurse or physician administer
the appropriate agent. In rare situations, another qualified sonographer could
administer the appropriate contrast agent if the registered nurse or physician
is not available at the time of the study.
When To
Perform Contrast Echocardiography
The cardiac
sonographer has the responsibility to carry out the physician’s order for the
performance of the examination and therefore initially determines the overall
technical quality of the echocardiogram. Thus this person is often in the
primary position to identify the need for contrast enhancement. It is well
established that in up to 20% of resting studies, the endocardial border
definition of the left ventricle is suboptimal. This has been defined as the
inability to visualize at least 2 myocardial segments of the left ventricle.
Suboptimal visualization of certain segments, such as the anterior or lateral
walls, may be even worse during stress echocardiography. The enhancement of
left ventricular endocardial border definition can be facilitated by using
transpulmonary contrast agents.
Other
clinical situations that may require the use of contrast are the Doppler signal
enhancement of tricuspid regurgitation jet velocity for estimating pulmonary
artery pressure, and the improvement of aortic, pulmonic, and mitral valve
spectral signals for further analysis of valvular disease severity. In
addition, if 2-dimensional echocardiography identifies previously unsuspected
findings suggestive of intracardiac or intrapulmonary shunt, this may
necessitate the performance of a right-heart contrast study to determine the
presence or absence of shunt flow. The cardiac sonographer often can identify
the need for a contrast agent in these clinical situations and can improve the
efficiency and accuracy of the echocardiographic examination.
To address
these clinical issues, the sonographer must have a physician’s order for the
contrast agent and a preapproved and written procedure plan, established by the
medical director, for initiation of the appropriate contrast agent indicated in
the particular situation. The supervising or interpreting physician’s approval
for the study should be obtained whenever possible on a case-by-case basis.
However, in the consideration of procedure time, patient satisfaction, or
unnecessary delay, a standing order or laboratory policy directive can be
considered an alternative means to accomplish timely completion of the echocardiographic
examination. In some instances, the echocardiography laboratory medical
director could provide standing orders, with the approval of the hospital
administration and medical staff and in accordance with state laws regarding
administration of pharmaceutical agents.
It is
recommended that only credentialed sonographers who practice in accredited or, at least, Level II laboratories be granted the authority to
determine the need for contrast agent usage when the supervising physician is
not immediately available. The ASE’s view is that these persons have achieved a
standard of competency, are well experienced, and can apply independent
judgment with sufficient problem-solving skills to assume the responsibility of
determining when to incorporate contrast agents.
Intravenous
Access For Contrast Injection
The third
component of the cardiac sonographer’s role in performing contrast
echocardiography involves obtaining proper IV access for injections of the
agent. This represents an opportunity for the sonographer to learn new skills,
gain an enhanced role in the laboratory, and provide higher-quality patient
care. Echocardiography laboratories that have registered nurses, physicians, or
IV teams readily available to assist in contrast studies are at an advantage
and represent the ideal situation, but they may reflect a minority of
laboratory settings. The task of obtaining IV access should not be considered a
role reserved only for nurses and physicians. Many allied health professionals
are trained to perform venipuncture, including phlebotomists, emergency medical
technicians, and radiologic and nuclear medicine technologists. Respiratory
therapists perform direct radial artery cannulization to obtain blood samples
for blood gases. As with any health care professional who performs IV insertion
techniques, the sonographer must complete the appropriate training and
certification process before assuming this skill.
The
difficulty in obtaining IV training is recognized; however, it may be
facilitated by the active involvement of the echocardiography laboratory
medical director, or through consultation with nursing administration or
perhaps with the clinical laboratory director. The hospital system might offer
a program, and courses might be offered in a community college or by
independent clinical laboratories. In addition, professional organizations and
ultrasound contrast companies are investigating avenues for IV training. When
available, local resources are the best approach for the sonographer seeking
certification.
It is
recommended that IV training encompass knowledge of venous anatomy and
appropriate sites of access, risks to patients and the health care
professional, use of sterile technique, infection control, and safety
precautions. Additional components of training are the confirmation of venous
access and the knowledge of proper supplies, including the selection and
inspection of the various angiocatheters and needles to be used. A checklist
that outlines the procedure and process may be useful. Sonographers should
obtain appropriate patient consent and provide an explanation of the procedure.
Other elements that must be in place are documentation of the training
provided, certification, periodic skill assessment, and close supervision.
An
additional consideration for cardiac sonographers is those patients with
existing IV lines, whether in the arm or other sites. It is recommended that
sonographers who use these sites have thorough knowledge of the catheter type,
IV patency, and medications being infused and have direct contact with the
patient’s nurse for consultation and assistance. This will ensure proper use of
the existing IV line and prevent complications.
The ASE
recommends that only credentialed sonographers who have had proper IV training,
with verified competency, be allowed to perform this procedure, and these
persons must be fully aware of the risks and benefits of IV insertion. It is
strongly recommended that contrast studies be done only in settings where
direct supervision by a physician or nurse is available. Patient safety remains
the most important component.
Injection Or Infusion Of Contrast
Agent
After IV
access is secured, the injection or infusion of the contrast agent is the
remaining component of the contrast echocardiography examination. The
recommended approach is that a registered nurse or physician performs the
actual injection or infusion of the agent while the cardiac sonographer focuses
on acquisition of the images. However, in situations in which the nurse or
physician is not readily available and a written policy is in place, a
sonographer might perform this function. Other allied health professionals
perform injections or administer drugs on standing, preapproved written orders
or after obtaining verbal orders from a physician.
Any person
who administers the contrast agent must have knowledge of the proper technique
for injection or infusion, the approved indications, the agent’s safety profile
(ie, contraindications), the possible allergic reactions, and the potential
risk to the patient. This requires carefully explaining the procedure to the
patient, answering questions and addressing concerns, and obtaining consent
(written, when necessary). The current contrast agents have an excellent safety
profile, and complications are extremely rare. However, of particular concern
are patients with intracardiac or intrapulmonary right-to-left shunts, in whom
the potential for adverse events are greater. Importantly, a nurse or physician
should be available for immediate response, and the necessary emergency
equipment and medications should be available in case of allergic reaction.
It is the
official position of the ASE that cardiac sonographers who administer contrast
agents must have demonstrable training and skills with thorough product
knowledge, and laboratories must have clearly defined written policies and
procedures in place, including standing orders from the laboratory medical
director. Only credentialed cardiac sonographers should be given this
responsibility, and the use of contrast agents should be carried out in
accredited or, at least, Level II echocardiography laboratories.
