Everything You Always Wanted to Know About Vital Signs

1
Everything You Always Wanted to Know About Vital
Signs

• Joe Lex, MD, FAAEM
• Temple University Hospital
• Philadelphia, PA
• joe_at_joelex.net

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Vital Signs

• Accepted
• Temperature
• Heart rate
• Respiratory rate
• Blood pressure

• Suggested
• Nutritional status
• Smoking status
• Spirometry
• Orthostatic vital signs
• Pulse oximetry

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Vital Signs

• Accepted
• Temperature
• Heart rate
• Respiratory rate
• Blood pressure

• Suggested
• Nutritional status
• Smoking status
• Spirometry
• Orthostatic vital signs
• Pulse oximetry

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Temperature

• Core temperature gt37 0.6oC (98.6 1.08oF) 2
  SD
• Fever gt2 SD above the mean
• Oral gt37.8oC or gt100oF
• Rectal gt38.0oC or gt100.4oF
• Hypothermia lt35oC or lt95oF. Hyperthermia
  gt40oC or gt104oF

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Temperature

• Most accurate sites
• Distal third of esophagus
• Anterior inferior quadrant of tympanic membrane
• Pulmonary artery

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Temperature

• Mercury-in-glass thermometers (no longer
  available) required time
• Mouth 7 minutes
• Rectum 3 minutes
• Axilla 10 minutes

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Temperature Oral

• Disposable covers of electronic devices not
  completely effective in preventing probe
  contamination
• Right or left sublingual pocket bad placement
  falsely ?by 2.7oC (4.9oF)

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Temperature Oral

• Measurement affected by hot or cold drinks, cold
  ambient air, tachypnea
• Measurement NOT affected by cigarette smoking,
  oxygen flow

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Temperature Rectal

• Can cause autonomic changes in patient with
  recent MI
• Most accurate 8 cm or more from anus using
  indwelling thermistor
• Most probes only 3 to 5 cm
• Lag behind true core temperature changes by 4
  minutes or more

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Temperature Rectal

• Complications reported rectal perforation,
  pneumoperitoneum, bacteremia, dysrhythmia, shock
• Stool freezes in hypothermic patients probe
  placed in frozen stool gives false low readings

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Temperature Ear

• Double ear thermometry 61 sensitive / 95
  specific for fever
• May miss 40 of fevers
• Cerumen impaction ?accuracy
• TM perforation reported

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Temperature Ear

• Underestimates core temperature if ambient
  temperature lt24.6oC (76oF)

13
Temperature Armpit

• Axillary Skin
• Positive means positive 98 specific
• Misses fever frequently 33 sensitive

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Temperature Other

• Assessment by touch
• Parents 75 accurate
• Physicians 70 accurate

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Temperature Other

• Fresh-voided urine measured immediately accurate
  core temperature

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Pulse

• Blood flows through vessels at 0.5 m/sec
• Pressure waves move at 3 to 5 m/sec
• Thus pulse is a pressure wave
• Palpated HR approximates actual HR within 2

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Pulse

• Palpate at brachial artery can appreciate pulse
  contour and amplitude
• Routine measurement of pulse amplitude not
  reproducible without instrumentation

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Pulse

• New norms being proposed
• Bradycardia lt50 beats/min
• Tachycardia gt90 beats/min
• High temperature without tachycardia drug fever,
  typhoid fever, central neurogenic fever

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Pulse

• Femoral pulses during CPR may reflect either
  forward arterial flow or "to-and-fro" movement of
  blood from right heart to venous system
• Carotid pulse provides truer representation of
  flow

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Respiratory Rate Kids

• Infants if RR gt60, 80 hypoxic

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Respiratory Rate Kids

• Prehospital respiratory rate lt10 / min or gt29/min
  associated with major injury in 73
• Rate by stethoscope higher than if obtained by
  observation by up to 2.6 breaths / minute

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Pulse Oximetry (SpO2)

• Patient having seizure most accurate SpO2 is
  earlobe
• AJCC article 62 of clinicians think that SpO2
  provides information about ventilatory status

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Pulse Oximetry (SpO2)

• Anemia fewer hemoglobin molecules easier to
  saturate ? SpO2 may be high, but total oxygen
  content will be low
• Polycythemia more hemoglobin molecules difficult
  to saturate ? "hypoxemia" when oxygen content may
  be normal

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Pulse Oximetry (SpO2)

• Methylene blue absorbs light at 660 nm, similar
  to reduced Hgb
• Can artificially lower SpO2 reading to as low as
  1
• Similar with other injectable dyes indigo
  carmine, indocyanine green, fluorescein

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Pulse Oximetry (SpO2)

• Bilirubin does not affect pulse ox
• Venous pulsations from right heart failure,
  tourniquet or BP cuff, tricuspid regurgitation
  may be interpreted as arterial and therefore
  falsely low

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Pulse Oximetry (SpO2)

• Oximeter cannot determine whether hemoglobin is
  saturated with CO or O2
• Nail polishes (red, blue, green) do not impair
  readings
• Pulse oximeter overestimates arterial oxygen
  saturation in dark-skinned individuals with
  hypoxia

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Blood Pressure

• Palpated systolic blood pressures underestimates
  manometric values by nearly 30
• ATLS no longer teaches palpation
• Carotid ? SBP 60-70 mm Hg
• Femoral ? SBP 70-80 mm Hg
• Radial pulse ? SBP gt80 mm Hg

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Blood Pressure

• Palpated systolic blood pressures underestimates
  manometric values by nearly 30
• ATLS no longer teaches palpation
• Carotid ? SBP 60-70 mm Hg
• Carotid and femoral ? SBP 70-80 mm Hg
• Radial pulse ? SBP gt80 mm Hg

WRONG
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Blood Pressure

• Width of bladder 50 of distance from acromion
  process to lateral epicondyle
• Length of bladder 80 of midarm circumference or
  twice width
• About 40 of American adults require nonstandard
  size cuffs

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Blood Pressure

• If weight gt95 kg, arm circumference gt35 cm
  larger cuff changes
• 33 of systolic HTN to borderline
• 62 of borderline systolic HTN to normal
• 79 with borderline diastolic HTN to normal

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Blood Pressure

• In general, automated readings yield higher SBPs
  and lower DBPs (range 4.0 to 8.6 mmHg)

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Blood Pressure

• If arm not perpendicular to body, measurements 9
  to 14 mm Hg higher regardless of body position
• Infant flush method return of color after cuff
  deflation underestimates SBP by up to 40 mmHg ?
  DON'T USE

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Blood Pressure

• Forearm measurements show fair correlation to
  standard upper arm values within 20 mmHg in 86
  of systolic measurements and 94 of diastolic
  measurements
• Using stethoscope bell gives higher reading than
  diaphragm

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Blood Pressure

• Normal blood pressure increases with decreasing
  distance from the aorta
• Normal diurnal pattern increase throughout day
  with significant rapid decline during early, deep
  sleep

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Blood Pressure

• White coat hypertension prevalent in 20 to 94
• More common in women, elderly, nonsmokers

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Blood Pressure

• False low
• Cuff too wide
• Too much pressure with stethoscope head
• Rapid cuff deflation

• False high
• Cuff too narrow
• Anxiety
• Pain
• Tobacco use
• Exertion
• Unsupported arm
• Slow cuff inflation

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Blood Pressure

• High pulse pressure (60 mm Hg)
• Anemia
• Exercise
• Hyperthyroidism
• A-V fistula
• Aortic regurgitation
• Patent ductus

• Low pulse pressure (20 mm Hg)
• Hypovolemia
• Increased peripheral vascular resistance
• Decreased stroke volume

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Blood Pressure

• Ratio of pulse rate over SBP ? shock index (SI),
  normal range of 0.5 to 0.7.
• SI gt0.85 to 0.90 suggests acute illness in
  medical patients
• Increase in potential for gross hemodynamic
  instability in a trauma patient

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Blood Pressure

• Paradoxical bradycardia with hypotension from
  hemoperitoneum can be treated with atropine, but
  increases dysrhythmias preferred treatment is
  volume replacement

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Orthostatic Vital Signs

• When a normal subject stands
• heart rate increases by average 13 beats /
  minute
• systolic blood pressure slightly decreases or no
  change
• diastolic blood pressure slightly increases or
  no change

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Orthostatic Vital Signs

• Acute blood loss decreases pressure gradient
  between venules and right atrium ? decreased
  venous return
• Dominant compensatory mechanism ? carotid sinus
  baroreceptor inhibition of sympathetic outflow

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Orthostatic Vital Signs

• Sympathetic reflexes geared for maintenance of
  arterial pressure gt maintenance of cardiac output
• Reflexes intact ? 30 to 40 of blood volume lost
  before death
• Fluid shift interstitium to intra-vascular
  space 1 to 40 hours

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Orthostatic Vital Signs

• Young adult volunteers
• Bled 500 to 1200 mL
• No reliable change in postural BP
• Consistent postural ? in HR 35 - 40 even after
  500-mL loss
• Bled 1000 mL 2/6 could stand
• Both postural HR ? gt30/min

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Orthostatic Vital Signs

• Healthy adult blood donors
• 500 mL blood loss
• Heart rate ? 30 beats / minute 13.2 sensitive /
  99.5 specific
• Heart rate ? 20 beats / minute 44.7 sensitive /
  95.4 specific

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Orthostatic Vital Signs

• Conclusion hypovolemia secondary to acute blood
  loss accurate if
• large postural pulse change (gt30 beats/min)
• severe postural dizziness (can't complete vital
  signs)

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Orthostatic Vital Signs

• Mod blood loss 22 sensitive
• If negative, acute blood loss 1000 mL unlikely
  2 false-negative
• Blood loss 500 mL cannot be excluded 43-87
  false-negative
• Ethanol exaggerates postural pulse changes for up
  to 8 hours

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Orthostatic Vital Signs

• Method
• Measure BP and HR after patient supine for 2-3
  minutes
• Have patient stand for 1 minute and record BP,
  HR, symptoms

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Orthostatic Vital Signs

• Supine-to-sitting test not reliable for detecting
  1000 mL of blood loss 55 false-negative results
• All studies apply only to healthy individuals
  with acute blood loss

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Orthostatic Vital Signs

• Orthostatic vital sign changes in volume-depleted
  elderlynever been accurately studied
• 8 to 40 of normovolemic nursing home patients
  have orthostatic hypotension

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Orthostatic Vital Signs

• Potential causes
• Medications
• Non-neurogenic causes impaired venous return,
  hypovolemia, cardiac insufficiency
• Neurogenic causes multisystem atrophy, diabetic
  neuropathy

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Orthostatic Vital Signs

• Clinically normovolemic children
• 25 have postural increase in pulse of gt20
  beats/minute
• 11 have postural fall in systolic blood pressure
  of gt20 mm Hg

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Orthostatic Vital Signs

• Children if near-syncope occurs or heart rate
  ?gt25 beats/min, orthostatic vital signs are
• 95 specific
• 75 sensitive

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