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@joelex.net

2. Vital Signs Accepted Temperature Heart rate Respiratory rate Blood pressure Suggested Nutritional status Smoking status Spirometry Orthostatic vital signs Pulse oximetry

3. Vital Signs Accepted Temperature Heart rate Respiratory rate Blood pressure Suggested Nutritional status Smoking status Spirometry Orthostatic vital signs Pulse oximetry

4. Temperature Core temperature >37 ± 0.6oC (98.6 ± 1.08oF) ± 2 SD Fever: >2 SD above the mean Oral: >37.8oC or >100oF Rectal: >38.0oC or >100.4oF Hypothermia: <35oC or <95oF. Hyperthermia: >40oC or >104oF

5. Temperature Most accurate sites Distal third of esophagus Anterior inferior quadrant of tympanic membrane Pulmonary artery

6. Temperature Mercury-in-glass thermometers (no longer available) required time Mouth = 7 minutes Rectum = 3 minutes Axilla = 10 minutes

7. 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)

8. Temperature: Oral Measurement affected by hot or cold drinks, cold ambient air, tachypnea Measurement NOT affected by cigarette smoking, oxygen flow

9. 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

10. Temperature: Rectal Complications reported: rectal perforation, pneumoperitoneum, bacteremia, dysrhythmia, shock Stool freezes in hypothermic patients: probe placed in frozen stool gives false low readings

11. Temperature: Ear Double ear thermometry 61% sensitive / 95% specific for fever May miss ~40% of fevers Cerumen impaction ?accuracy TM perforation reported

12. Temperature: Ear Underestimates core temperature if ambient temperature <24.6oC (76oF)

13. Temperature: Armpit Axillary = Skin Positive means positive: 98% specific Misses fever frequently: 33% sensitive

14. Temperature: Other Assessment by touch Parents 75% accurate Physicians 70% accurate

15. Temperature: Other Fresh-voided urine measured immediately: accurate core temperature

16. 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%

17. Pulse Palpate at brachial artery: can appreciate pulse contour and amplitude Routine measurement of pulse amplitude not reproducible without instrumentation

18. Pulse New norms being proposed: Bradycardia <50 beats/min Tachycardia >90 beats/min High temperature without tachycardia: drug fever, typhoid fever, central neurogenic fever

19. 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

20. Respiratory Rate: Kids Infants: if RR >60, ~80% hypoxic

21. Respiratory Rate: Kids Prehospital respiratory rate <10 / min or >29/min associated with major injury in 73% Rate by stethoscope higher than if obtained by observation by up to 2.6 breaths / minute

22. Pulse Oximetry (SpO2) Patient having seizure: most accurate SpO2 is earlobe AJCC article: 62% of clinicians think that SpO2 provides information about ventilatory status

23. 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

24. 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

25. 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

26. 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

27. 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 >80 mm Hg

28. 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 >80 mm Hg

29. 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

30. Blood Pressure If weight >95 kg, arm circumference >35 cm: larger cuff changes… …33% of systolic HTN to borderline …62% of borderline systolic HTN to normal …79% with borderline diastolic HTN to normal

31. Blood Pressure In general, automated readings yield higher SBPs and lower DBPs (range 4.0 to 8.6 mmHg)

32. 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

33. 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

34. 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

35. Blood Pressure White coat hypertension prevalent in 20% to 94% More common in women, elderly, nonsmokers

36. 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

37. 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

38. Blood Pressure Ratio of pulse rate over SBP ? shock index (SI), normal range of 0.5 to 0.7. SI >0.85 to 0.90 suggests acute illness in medical patients Increase in potential for gross hemodynamic instability in a trauma patient

39. Blood Pressure Paradoxical bradycardia with hypotension from hemoperitoneum can be treated with atropine, but increases dysrhythmias; preferred treatment is volume replacement

40. 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

41. 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

42. Orthostatic Vital Signs Sympathetic reflexes geared for maintenance of arterial pressure > 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

43. 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 ? >30/min

44. 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

45. Orthostatic Vital Signs Conclusion: hypovolemia secondary to acute blood loss accurate if… …large postural pulse change (>30 beats/min) …severe postural dizziness (can't complete vital signs)

46. 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

47. 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

48. 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

49. Orthostatic Vital Signs Orthostatic vital sign changes in volume-depleted elderly:never been accurately studied 8% to 40% of normovolemic nursing home patients have orthostatic hypotension

50. Orthostatic Vital Signs Potential causes: Medications Non-neurogenic causes: impaired venous return, hypovolemia, cardiac insufficiency Neurogenic causes: multisystem atrophy, diabetic neuropathy

51. Orthostatic Vital Signs Clinically normovolemic children 25% have postural increase in pulse of >20 beats/minute 11% have postural fall in systolic blood pressure of >20 mm Hg

52. Orthostatic Vital Signs Children: if near-syncope occurs or heart rate ?>25 beats/min, orthostatic vital signs are… … 95% specific … 75% sensitive

53. joe@joelex.net