Page 213 - ACCCN's Critical Care Nursing

190 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

Autonomic control It is important to create a health history, if not already
The cardiovascular control centre connects with the hypo- obtained. This history should aim to elicit a description
thalamus to control temperature, the cerebral cortex and of the present illness and chief complaint. A useful guide
the autonomic system to control cardiac activity and in taking a specific cardiac history is to use directed ques-
peripheral vascular tone. Information about blood pres- tions to seek information regarding symptom onset,
sure and resistance is sensed by neural receptors (barore- course, duration, location, precipitating and alleviating
ceptors) in the aortic arch and the carotid sinuses, which factors. Some common cardiovascular disease related
detect changes in blood supply to the body and the brain. symptoms to be observant for include: chest discomfort
Impulses from these receptors initiate a blood-pressure or pain, palpitations, syncope, generalised fatigue, dys-
regulating reflex in the cardiovascular centre, which acti- pnoea, cough, weight gain or dependent oedema. Chest
vates the parasympathetic system and sympathetic system pain, discomfort or tightness should be initially consid-
to alter cardiac activity and dilation or constriction of ered indicative of cardiac ischaemia until proven other-
arterioles and veins to lower or raise blood pressure. The wise by further examination and diagnostic assessment.
cardiovascular system also maintains a constant resting Additionally, a health history should be inclusive of
tone of intermediate tension in the arteries. known cardiovascular risk factors, such as hyperlipidae-
mia or hypertension, and any medications the patient
Hormonal control may be taking including over the counter medications.
Changes in blood pressure are also detected by the Prior to inspecting or palpating the patient, the nurse
adrenal medulla, which secretes catecholamines as cardiac should take note of the patient’s general appearance
output declines. The two main catecholamines, norepi- noting whether the patient is restless, able to lie flat, in
nephrine (noradrenaline) and epinephrine (adrenaline), pain or distress, is pale or has decreased level of con-
mimic the action of the sympathetic system. Noradrena- sciousness. Patients with compromised cardiac output
line directly stimulates the alpha-adrenergic receptors of will likely have decreased cerebral perfusion and may
the autonomic system, causing vasoconstriction and have mental confusion, memory loss or slowed verbal
raising blood pressure, while adrenaline has a wider responses. Additionally, assessment of any pain should
range of effects, including stimulating β 1 -adrenergic be noted.
receptors, resulting in increased cardiac contractility and
heart rate and thereby also raising blood pressure. Specific physical assessment in relation to cardiovascular
function should be inclusive of:
Renal control ● vital signs
Renal control of blood pressure in the long-term occurs ● respiratory assessment for signs of pulmonary oedema
via control of blood volume. Generally, as blood pressure (shortness of breath or basal crepitations)
or volume rises, the kidneys produce more urine; con- ● assessment of neck vein distension for signs of right
versely, as blood pressure or volume falls, the kidneys sided venous congestion
produce less urine. ● assessment for signs of peripheral oedema
● capillary refill time with >3 sec return indicative of
In addition to longer term fluid regulation, during acute
illness or time of acute hypotension, the renin-angiotensin- sluggish capillary return
aldesterone system (RAAS) plays an important role in ● 12-lead ECG for signs of ischaemia or cardiac
maintaining blood pressure. This negative feedback pathology
system results in both reabsorption of intravascular fluid ● appearance and temperature of the skin for signs of
and increases peripheral resistance, in an effort to increase peripheral constriction or dehydration
blood pressure. Further details on the RAAS system can ● core body temperature measurement
be found in Chapter 18. ● urine output with <0.5 mL/kg/hour a potential indi-
cator of decreased renal perfusion. 12
ASSESSMENT ASSESSMENT OF PULSE

It is essential that the critical care nurse conducts a com- In the critical care environment, the heart rate can be
prehensive cardiac assessment on a critically ill patient. observed from a cardiac monitor; however, this does not
The nursing assessment aims to both define patient car- give qualitative information about the arterial pulse. Rou-
diovascular status as well as to inform implementation of tinely performed as part of most patient assessments,
an appropriate clinical management plan. The focus of information gathered from pulse assessment can give
the cardiovascular assessment varies according to the useful cues and direct further assessments. Although the
setting, clinical presentation and treatments commenced, radial pulse is distant from the central arteries, it is useful
if any. However, the main priority should be to determine for gathering information on rate, rhythm and strength.
whether the patient is haemodynamically stable or requir- Heart rate below 60 beats per minute is defined as ‘bra-
ing initiation or adjustment of supportive treatments.
dycardia’ (‘brady’ is Greek for slow, and ‘kardia’ means
A thorough cardiac assessment requires the critical care heart). A heart rate greater than 100 beats per minute is
nurse to be competent in a wide range of interpersonal, called ‘tachycardia’ (’tachy’ in Greek meaning swift). An
observational, and technical skills. A cardiac assessment important aspect of pulse assessment involves assessment
should be performed as part of a comprehensive patient for regularity. Detection of an irregular pulse should
assessment and should consider the following elements. trigger further investigation and prompt ECG assessment