Vital Signs Measurement - Clinical Tree

Measuring the temperature, pulse, respiratory rate (RR), blood pressure, and pulse oximetry is generally recommended for all emergency department (ED) patients, in addition to assessment of pain in the appropriate patient population. For very minor problems or for some fast-track patients (e.g., suture removal), a full set of vital signs may not be required, and this is best decided on a case-by-case basis rather than by strict protocol. Vital signs may indicate the severity of illness and also dictate the urgency of intervention. Although a single set of abnormal values suggests pathology, findings on triage or the initial vital signs may be spurious and simply related to stress, anxiety, pain, or fear. It would be incorrect and not standard of care to attribute initial triage blood pressure, RR, or pulse rate to specific pathology or to retrospectively assume that diagnostic or treatment interventions should have been initiated based solely on these readings. The greatest utility of vital signs is in their continued observation and trends over time. Deteriorating vital signs are an important indicator of a compromised physiologic condition, and improving values provide reassurance that the patient may be responding to therapy. When a patient undergoes treatment over an extended period, it is essential that the vital signs be repeated as appropriate to the clinical scenario, particularly those that were previously abnormal. In some clinical circumstances, it is advisable to monitor the vital signs continuously.

Vital signs should be measured and recorded at intervals as dictated by clinical judgment, the patient's clinical state, or after any significant change in these parameters. Adhering to strict protocols or disease categories is not useful or productive. An abnormal vital sign may constitute the patient's entire complaint, as in a febrile infant, or it may be the only indication of the potential for serious illness, as in a patient with resting tachycardia.

Emergency medical service (EMS) personnel begin assessment of the patient's status and vital signs in the prehospital setting. Surges of epinephrine and norepinephrine commonly occur during transport by the EMS, and these catecholamines are known to alter vital signs and lead to increases greater than 10% in the heart rate. Vagal influences may also influence EMS-derived vital signs. Prehospital vital signs should always be interpreted with the entire clinical scenario in perspective.

Blood pressure and pulse are frequently evaluated together as a measure of blood volume. Capillary refill is discussed as an assessment of overall perfusion, circulatory volume, and blood pressure. Although body temperature is usually the last vital sign measured during resuscitation, it has special importance for patients suffering from thermal regulatory failure. With these considerations in mind, the current chapter is organized according to the priorities of patient resuscitation and evaluation. Assessment of pain as a vital sign is gaining acceptance and is discussed briefly at the end of this chapter.

Background

Early recognition of vital signs dates to the fourth century bc , when Herophilus first described sphygmology, or palpation of the pulse in terms of size, frequency, force, and rhythm. Chinese clinicians (second century bc ) timed the pulse by the RR of the examiner in the belief that four pulsations per respiration was normal for adults. The study of pulses was greatly influenced by Galen, who expanded the subject into a rather complex and obscure art form and wrote 18 books on the subject.

Blood pressure was first measured directly in 1733 by Hales, who recorded arterial pressure in a mare by cannulation with a brass pipe and a blood-filled glass column. Frank used large-bore catheters connected to a rubber membrane in a 1903 manometer. The invention of inflatable cuff manometers (Riva-Rocci, 1896) and discovery of the arterial phase sounds (Korotkoff, 1905) allowed the development of indirect measurement of blood pressure.

Clinical thermometry was introduced by Sanctorius in 1625, with early thermometers being filled with alcohol. Mercury column thermometers were introduced by Fahrenheit in 1714. Although their routine use was supported by Boerhaave, thermometry was not established as routine clinical practice until the 1870s.

Normal Values

The range of normal resting vital signs for specific age groups must be appreciated by the clinician to enable identification of abnormal values and their clinical significance. The normal ranges for vital signs are also influenced by gender, race, pregnancy, and residence in an industrialized nation. These ranges have not been validated in ED patients, who have many reasons for abnormalities in vital signs, including anxiety, pain, and altered physiology as a result of their disease states. Ranges of normal vital signs, commonly quoted as normal or abnormal in other settings, serve only as a guide and not an absolute criterion for diagnosis, treatment, further observation, or intervention in the ED.

Published vital sign norms for children are not as well accepted as those for adult patients. Table 1.1 and Table 1.2 report heart rate and RRs by age grouping and percentile for children from birth to 18 years of age. This data represents a large cross-sectional study using 6 months of nurse-documented heart rates and RRs from the electronic records of 14,014 children on general medical and surgical wards at two tertiary-care children's hospitals. Up to 54% of heart rate observations and up to 40% of RR observations in this sample were outside textbook reference ranges. During the newborn period, normal arterial blood pressure rises rapidly. Values for pulse and respiration in children older than 3 years reflect an average of male and female values for 0- to 1-, 3-, 9-, and 16-year-old populations. The values for blood pressure reflect an average of male and female values for the 1- to 6-month-old and the 3-, 9-, and 16-year-old populations. Other studies have assessed the reference values for RR in children demonstrating the same variability of pediatric “normal” vital sign ranges.

TABLE 1.1

Pediatric Heart Rate Limits Based on Age Group and Percentile

Adapted from Table 3 of Bonafide CP, Brady PW, Keren R, et al: Development of heart and respiratory rate percentile curves for hospitalized children, Pediatrics 131(4):e1150–e1157, 2013.

AGE GROUP	5TH PERCENTILE	50TH PERCENTILE	95TH PERCENTILE
0–3 months	113	140	171
3–6 months	108	135	167
6–9 months	104	131	163
9–12 months	101	128	160
12–18 months	97	124	157
18–24 months	92	120	154
2–3 years	87	115	150
3–4 years	82	111	146
4–6 years	77	106	142
6–8 years	71	100	137
8–12 years	66	94	129
12–15 years	61	87	121
15–18 years	57	82	115

TABLE 1.2

Pediatric Respiratory Rate Limits Based on Age Group and Percentile

Adapted from Table 4 of Bonafide CP, Brady PW, Keren R, et al: Development of heart and respiratory rate percentile curves for hospitalized children, Pediatrics 131(4):e1150–e1157, 2013.

AGE GROUP	5TH PERCENTILE	50TH PERCENTILE	95TH PERCENTILE
0–3 months	27	41	62
3–6 months	25	38	58
6–9 months	23	35	54
9–12 months	22	33	51
12–18 months	21	31	48
18–24 months	20	29	45
2–3 years	18	27	42
3–4 years	18	25	40
4–6 years	17	24	37
6–8 years	16	23	35
8–12 years	15	21	31
12–15 years	13	19	28
15–18 years	13	18	26

For the adult population, normal blood pressure values have been better established. Although systolic blood pressure increases with age, normotensive or normal systolic blood pressure is defined as 90 to 140 mm Hg, and normotensive or normal diastolic blood pressure is defined as 60 to 90 mm Hg. The recent literature suggests defining an “optimal” blood pressure as 115/75 mm Hg because values at or below this level have been associated with minimal vascular mortality. It has been suggested that the definition of hypertension be further expanded to integrate a global cardiovascular risk assessment. Although most patients have similar blood pressure in both arms, Pesola and colleagues found that 18% of their hypertensive population and 15% of their normotensive population had a difference of greater than 10 mm Hg in systolic blood pressure between arms.

Within the adult population, optimal definitions for normal systolic blood pressure probably vary with age, and particular differentiation should be made in regard to geriatric patients in the emergency setting. The recent literature suggests redefining values representative of hypotension in the elderly, especially in the setting of trauma. Systolic blood pressure readings ranging from approximately 90 to 120 mm Hg have been associated with occult hypoperfusion and increased mortality in geriatric trauma patients.

In 1928 the New York Heart Association, by consensus, established the normal limits for the resting heart rate as 60 beats/min and 100 beats/min. More recent data indicate that 45 beats/min and 95 beats/min may better define the heart rate limits of normal sinus rhythm in adults of all ages. Spodick and colleagues recommended that the operational definition for the limits of the resting heart rate in adults should be 50 beats/min and 90 beats/min. This view is widely supported among cardiologists, but these ranges have not been validated in the ED setting. There is currently no consensus on what constitutes a normal adult RR; however, an RR range of 12 to 24 breaths/min is generally accepted in the existing literature as the norm for adults.

Pregnancy results in alterations in the normal adult values of pulse and blood pressure. Pregnancy is characterized by significant increases in minute ventilation, and is thought to be due to the combined facilitatory effects of progesterone and estrogen on central and peripheral chemoreflex drives to breathe. The resting pulse rate increases throughout pregnancy from 10% to 15% over baseline values. The norms for systolic and diastolic blood pressure are dependent on patient positioning. When a pregnant patient is sitting or standing, systolic pressure is essentially unchanged. Diastolic pressure declines until approximately 28 weeks' gestation, at which time it begins to rise to nonpregnant levels. When a pregnant patient is in the lateral decubitus position, both systolic and diastolic pressure decline until the 28th week and then begin to rise to nonpregnant levels ( Table 1.3 ).

TABLE 1.3

Vital Signs During Pregnancy in the Lateral Decubitus Position (Means ± SD)

Adapted from Katz R, Karliner JS, Resnik R: Effects of a natural volume overload state (pregnancy) on left ventricular performance in normal human subjects, Circulation 58:434, 1978. By permission of the American Heart Association.

	Trimester
PARAMETER	1ST	2ND	3RD
Pulse rate (beats/min)	77 ± 2	85 ± 2	88 ± 2
Systolic BP (mm Hg)	98 ± 2	91 ± 2	95 ± 2
Diastolic BP (mm Hg)	53 ± 2	49 ± 2	50 ± 2

BP, Blood pressure; SD, standard deviation.

Respiration

Breathing is initiated and primarily controlled in the medullary respiratory center of the brainstem. The respiratory center is modulated by the pneumotaxic center, which limits the length of the inspiratory signal and greatly influences the RR and apneustic center in the pons. Respiratory frequency reveals only a glimpse of the entire clinical picture. The pattern, effort, and volume of respiration may be more indicative of altered respiratory physiology. An abnormality in respiration may be a primary complaint or a manifestation of other systemic diseases. Increased RRs may be seen in patients with a variety of pulmonary or cardiac diseases, and acidosis, anemia, temperature, stress, and drugs (such as stimulants and salicylates) can significantly alter the RR in the absence of cardiopulmonary dysfunction.

Indications and Contraindications

The only contraindications to careful measurement of RR are the scenarios of respiratory distress, apnea, and upper airway obstruction, which require immediate therapeutic intervention. RR and respiratory effort should be assessed as soon as patient care demands allow.

The respiratory status of both adults and children plays a crucial role in determining the overall assessment of illness. Although it is a sensitive yet nonspecific indicator of respiratory dysfunction, the RR can also predict nonpulmonary morbidity. Several prehospital and hospital-based illness or injury severity scores feature the RR as a cardinal value. A prehospital RR of less than 10 breaths/min or greater than 29 breaths/min is associated with major injury in 73% of children. Using tachypnea alone as a predictor of pulmonary pathology, infants with an RR higher than 60 breaths/min are found to be hypoxic 80% of the time. Pediatric studies have linked abnormal RRs to in-hospital mortality and the level of care required in the ED. In a retrospective study exploring predictors of critical care admission for adult ED patients who were initially triaged as having low to moderate acuity, an abnormal RR at the first nursing assessment increased the odds of critical care admission by a factor of 1.66. An RR higher than 25 breaths/min in prehospital trauma patients was associated with increased mortality. Pre-arrest respiratory insufficiency (RR >36 breaths/min or pulse oximetry <90%) was an independent predictor of mortality (odds ratio [OR], 4.2) in patients with EMS-witnessed cardiac arrest. Although some studies have associated abnormal RRs in adult ED patients with increased mortality, a 2011 large prospective cohort study of adult patients found that an initial abnormal RR on triage in the ED was not an independent predictor of hospital mortality.

Procedure

To measure RR (inspirations per minute), count the respirations when the patient is unaware that his or her breathing is being observed. Count for a full minute to most accurately determine the RR. The frequency of breathing is less regular than the pulse, and inaccurate measurement is more likely to occur if the count is taken for a shorter interval. It is common to measure respirations over 15 seconds and multiply by 4, but this can significantly alter the true RR per minute. An infant's RR can easily be determined by observing or palpating the excursion of the chest or the abdominal wall. Infants should be observed for grunting respirations, which are produced by expiration against a partly closed glottis (an attempt to maintain positive airway pressure).

Interpretation

Respiratory Rate

The reproducibility of RR measurements may be limited by significant interobserver variability. Clinicians should recognize this inherent variability and interpret the RR with caution. Rates obtained by nurses versus medical students varied significantly, as did those obtained by medical students versus residents and attending clinicians. Interobserver variability may account for a difference of up to 6 breaths/min, and variability in the same observer may account for up to 5 breaths/min. A study comparing RRs obtained by triage nurses with an electronic monitor found that neither provided an accurate measurement of the RR in the ED, suggesting that new clinical strategies for obtaining this vital sign may be necessary. RR is an independent risk marker for in-hospital mortality in community-acquired pneumonia and should be measured when patients are admitted to the hospital with pneumonia and other acute conditions.

Current texts vary considerably in their definition of a normal RR and cite published values that range from 8 to 24 breaths/min. In a study that specifically investigated normal RRs in an ED (afebrile ambulatory patients without respiratory complaints), females had a mean RR of 20.9 breaths/min and males had a mean RR of 19.4 breaths/min. The researchers concluded that a normal RR in the adult patient population was 16 to 24 breaths/min. Other studies have provided additional information on normal resting and sleeping RRs in children younger than 7 years. RRs obtained with a stethoscope were higher than those obtained by observation (mean difference, 2.6 breaths/min in awake and 1.8 breaths/min in asleep children). Smoothed percentile curves demonstrated a larger dispersion at birth (5th percentile, 34 breaths/min; 95th percentile, 68 breaths/min), whereas dispersion was less at 36 months of age (5th percentile, 18 breaths/min; 95th percentile, 30 breaths/min).

The RR will generally increase in the presence of fever. It is often difficult to determine whether tachypnea is a primary finding or is simply associated with hyperpyrexia. A study of children younger than 2 years in whom pneumonia was subsequently diagnosed found that age-appropriate limits for resting tachypnea in the presence of fever could be defined. A sensitivity of 74% and specificity of 77% for pneumonia were found when children 6 months of age had an RR higher than 59 breaths/min, when those aged 6 to 11 months had an RR higher than 52 breaths/min, and when those 1 to 2 years old had an RR higher than 42 breaths/min. Even in the face of physiologic compensation for fever, interpretation of the RR alone can help predict the presence of pulmonary disease.

Respiratory Pattern and Amplitude

Hyperventilation and hypoventilation can result from an extensive variety of disorders and may be related to pulmonary or extrapulmonary pathology. Abnormal respiratory patterns can be characteristic of metabolic or central nervous system pathologic conditions ( Fig. 1.1 ) and may aid in the differential diagnosis. Kussmaul respirations describe the hyperventilation pattern seen in diabetic patients with ketoacidosis. Decreased RR is commonly seen with opiate toxicity. Hyperpnea, or a normal RR but clinically significant hyperventilation secondary to increased tidal volume, may be seen with salicylate poisoning.

Figure 1.1, Abnormal respiratory patterns. CVA, Cerebrovascular accident; RR, respiratory rate; V t , tidal volume.

Recognition of subtle tachypnea can be difficult in the emergency setting, although it can be the solitary indicator of disease. Another instance of pathology that can confuse routine measurement of the RR is diaphragmatic breathing or retractions. The variability in counting respiratory effort versus effective respirations is not generally appreciated in a single recorded value.

Observe the respiratory patterns carefully in children. In infants, it is essential to distinguish normal periodic breathing from apnea . By definition, periodic breathing consists of three or more respiratory pauses longer than 3 seconds in duration with less than 20 seconds between pauses. There is no associated bradycardia or cyanosis. This contrasts with apnea and is a particular problem in preterm infants. Apnea is defined as a respiratory pause longer than 20 seconds. It may be associated with bradycardia and hypoxia. Periodic breathing and apnea are believed to be disorders on a continuum, both stemming from abnormal physiologic control of respiration. Periodic breathing is considered a benign disorder. Infants with symptomatic apneic episodes that result in apparent life-threatening events are thought to be at increased risk for sudden infant death syndrome.

Pulse

Examine the pulse to establish the cardiac rate and regularity of the rhythm. Though rarely diagnostic, peripheral pulses may yield clues about cardiac disease, such as aortic insufficiency, and information about the integrity of the peripheral vascular supply. Doppler ultrasound has utility in locating a pulse, assessing fetal heart tones beyond the first trimester of pregnancy, evaluating peripheral lower extremity vascular insufficiency with an ankle-brachial index, and assessing blood pressure in infants or in patients with low-flow states.

Physiology

Blood flowing into the aorta with each cardiac cycle initiates a pressure wave. Blood flows through the vasculature at approximately 0.5 m/sec, but pressure waves in the aorta move at 3 to 5 m/sec. Therefore palpated peripheral pulses represent pressure waves, not blood flow.

Indications and Contraindications

Assessment of blood flow by palpation of the pulse can be used to gauge the presence of cardiac contractility and not just the electrical rhythm. Caution should be taken to not overgeneralize the presence or strength of a pulse when predicting blood pressure. The necessity for repeated pulse evaluations is dictated by the clinical complaint and the status of the patient. Continuous monitoring is not routine but may be helpful when the clinical situation predicts significant variability in heart rate, as in the setting of sepsis. An association between absence of a radial pulse or absence of both radial and femoral pulses and hypotension has been demonstrated in hypovolemic trauma patients. The variability in individual response prohibits the use of this parameter as an absolute gauge of blood pressure.

No contraindications exist to assessment of the pulse rate. Keep in mind a few cautionary notes about examination of the carotid pulse. Avoid concurrent bilateral carotid artery palpation because this maneuver could theoretically endanger cerebral blood flow. Massage of the carotid sinus, found at the bifurcation of the external and internal carotid arteries at the level of the mandibular angle, may result in reflex slowing of the heart rate. To avoid inadvertent carotid sinus massage, palpate the carotid pulse at or below the level of the thyroid cartilage. In adults with atherosclerotic disease, there is a rare risk of precipitating a cerebrovascular event by vigorous palpation of the carotid artery. Minimize this risk by prior auscultation of the carotid artery. If a bruit is present, gently palpate the carotid pulse while avoiding vigorous palpation, or use a Doppler ultrasound probe to assess carotid flow instead.

Procedure

Depending on the clinical scenario, pulses are palpable at numerous sites, although for convenience the radial pulse at the wrist is routinely used. Use the tips of the first and second fingers to palpate the pulse. The two advantages of this technique are that (1) the fingertips are quite sensitive, thereby enabling the pulse to be located easily and counted, and (2) the examiner's own pulse may be erroneously counted if the thumb is used. Pulses are easily palpated at the carotid, brachial, femoral, posterior tibial, and dorsalis pedis arteries. Palpate the pulse at the brachial artery to appreciate its contour and amplitude. Locate the pulse at the medial aspect of the elbow and note that it is more easily palpated when the elbow is held slightly flexed. Determine the pulse rate by counting for 1 minute, particularly if any abnormality is present. Common convention in the acute care setting is to count a regular pulse for 15 seconds and multiply the resulting number by 4 to determine the beats per minute.

In neonates, use direct heart auscultation and umbilical palpation as the methods of choice to determine the heart rate. Instantaneous changes in newborn heart rates are best indicated to the resuscitation team by the clinician tapping out each heartbeat. In unstable children, palpate the central arteries, particularly the femoral and brachial pulses, instead of the more peripheral arteries. In a comparison of four methods of determining the heart rate in infants, listening at the apex of the heart was found to be more accurate than palpation of the brachial, carotid, or femoral pulses. Of the sites for palpation of the heart rate, the femoral artery has proved most valuable, especially in hypotensive infants.

Interpretation

Pulse Rate

Consider the individual's physiology when interpreting the pulse. In infants and children, interpret the pulse rate with reference to age (see Table 1.1 ). Pulse varies with respiration: it increases with inspiration and slows with expiration. This is known as sinus dysrhythmia and is physiologic.

Although bradycardia is most commonly defined as a heart rate lower than 60 beats/min in adults, a well-conditioned athlete may have a normal resting heart rate of 30 to 40 beats/min. As discussed earlier, a redefinition of bradycardia to less than 45 beats/min and tachycardia to greater than 95 beats/min has been proposed based on a normal healthy population. Such definitions include 95% of the population and do not address any given individual's normal baseline rate.

Consider whether a patient's abnormal pulse rate is a primary or secondary condition. Examine the entire set of vital signs when attempting to discern the cause of the abnormal rate. For example, hyperthermia causes sinus tachycardia. Drug fever, typhoid fever, and central neurogenic fever are considerations when no corresponding tachycardia is found in a patient with elevated body temperature. Hypothermia, with its reduced metabolic demands, may be associated with bradycardia. Some disease states are defined by their effect on heart rate, such as thyrotoxicosis with tachycardia or myxedema coma with bradycardia.

Consider the medications that the patient may be taking or the presence of a mechanical pacemaker. Digitalis compounds, β-blockers, and antidysrhythmics may alter the normal heart rate and the ability of this vital sign to respond to a new physiologic stress. These cardioactive medications may cause the abnormality in the patient's heart rate. Nonprescription drugs can be equally significant in their effect on heart rate. Sympathomimetic drugs such as cocaine and methamphetamine increase heart rate, as do anticholinergic drugs.

Heart Rhythm

In addition to determining the pulse rate, obtain information about the regularity of the pulse by palpation. An irregular pulse suggests atrial fibrillation or flutter with variable block, and accurate assessment of the pulse should be carried out by auscultation of the apical cardiac sounds. The apical pulse is frequently greater than the peripheral pulse because of inadequate filling time and stroke volume, with resultant nontransmitted beats. A greater pulse deficit generally reflects more severe disease.

Pulse Amplitude and Contour

Accurate examination and description of pulse amplitude and contour can provide additional clinical information and aid in decision making. Superimposition of one pathophysiologic state on another may modify the pulse. For example, sepsis may result in variable pulse amplitudes, depending on the stage in the development of the disease. Early in sepsis, cardiac output increases and vascular resistance decreases, causing bounding pulses. In advanced sepsis or septic shock, falling cardiac output and increased vascular resistance are seen, and pulses are diminished. Definable age-related changes in pulse amplitude and contour can be identified. Such changes are due to an increase in arterial stiffness, resulting in increased pulse wave velocity and progressively earlier wave reflection. This leads to increased pulse amplitude in the elderly at all commonly measured sites (carotid, femoral, and radial). In addition to these age-related changes, pulse wave analysis may be useful in determining arterial stiffness and the likelihood of atherosclerotic disease in a vascular laboratory setting. If present globally, weak pulses can be a significant finding in hypotensive patients, or an indication of limb ischemia if isolated to one extremity. Bounding pulses can be seen with a widened pulse pressure and are discussed later in the section on blood pressure. Routine measurement of pulse amplitude is not reproducible by simple palpation and requires instrumentation not available in EDs.

Pulses During Cardiopulmonary Resuscitation

Palpated femoral pulses during chest compression may represent either forward arterial blood flow or “to-and-fro” movement of blood from the right side of the heart to the venous system. A carotid pulse is preferred when assessing the adequacy of chest compressions during cardiopulmonary resuscitation (see Chapter 17 ).

Arterial Blood Pressure

Systolic blood pressure changes with each heartbeat. Changes in arterial blood pressure over time may indicate success of treatment or worsening of the patient's overall condition. An abrupt reduction in a patient's arterial blood pressure usually indicates the need for immediate intervention or reconsideration of therapy. The current section discusses indirect blood pressure monitoring; intraarterial techniques are considered elsewhere. Discussion of the specific use of the Doppler device for measurement of pulse and blood pressure and for measurement of orthostatic blood pressure and changes in pulse follow this section. Despite an association between the absence of hypotension and the presence of a radial pulse or between hypotension and the absence of both radial and femoral pulses in the setting of trauma, the variability in individual responses prohibits the use of this parameter as an absolute gauge of blood pressure.

Physiology

Arterial blood pressure indicates the overall state of hemodynamic interaction between cardiac output and peripheral vascular resistance. Arterial blood pressure is the lateral pressure or force exerted by blood on the vessel wall. It indirectly measures perfusion, and blood flow equals the change in pressure divided by resistance. Because peripheral vascular resistance varies, a normal blood pressure does not confirm adequate perfusion. Mean arterial blood pressure (MAP) can be estimated by adding one third of the pulse pressure (i.e., the difference between systolic and diastolic blood pressure) to diastolic pressure or by using the following measure :

MAP = \frac{Diastolic pressure \times 2 + Systolic pressure}{3}

$MAP = \frac{Diastolic pressure \times 2 + Systolic pressure}{3}$

Many modern bedside telemetry monitors automatically incorporate MAP measurements into the blood pressure systolic and diastolic pressure readings.

Indications and Contraindications

Patients with minor ambulatory complaints unrelated to the cardiovascular system may not necessarily need their blood pressure measured in the ED, and those with hemodynamic instability need frequent monitoring of blood pressure. In children, there is a significant amount of variability regarding standard situations that require measurement of blood pressure. In general, the younger the patient, the less likely blood pressure will be measured. In newborns, infants, and even toddlers, capillary refill is sometimes substituted for standard blood pressure measurement, although viewing these tests as equivalent can lead to significant errors.

In low-flow states, Doppler measurement of blood pressure may be obtained rapidly. Repeated measurements will provide an evaluation of the adequacy of resuscitation in patients whose blood pressure cannot be auscultated by standard techniques and in those in whom intraarterial blood pressure measurements are either contraindicated or technically unobtainable. Placing a catheter for direct intraarterial measurement of blood pressure may be performed safely in the ED, but is not standard of care and has a higher risk for complications. In particular, direct measurement of arterial pressure during pulseless electrical rhythms may help discriminate between a severe shock state and otherwise nonresuscitatable status. Alternative noninvasive devices for continuous blood pressure measurement (CBPM) have been introduced clinically, with varying success. One common method of CBPM uses finger cuffs equipped with infrared (IR) photoplethysmography and sophisticated technology for quantification of finger blood pressure levels. Finapres (Ohmeda, Madison, WI) was the first commercial product using this technique, and several newer products are on the market today. A number of commercial systems use an alternative method of arterial applanation tonometry to measure CBPM. Further study is needed for the validation of devices using these techniques.

Relative contraindications to specific extremity blood pressure measurement include an arteriovenous fistula, ipsilateral mastectomy, axillary lymphadenopathy, lymphedema, and circumferential burns over the intended site of cuff application.

Equipment

Two types of blood pressure monitoring equipment are currently available and used in EDs: cuff type and noninvasive waveform analysis.

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