Vital Signs and Monitoring Devices

Normal adult ranges are the baseline every other number is read against

A vital sign means nothing until you know what it is being compared to. These are the adult figures.

Table 13.1Normal adult ranges are the baseline every other number is read against

Pediatric ranges differ by age and are covered in depth in the reference cards. The single most important difference is directional: children compensate well and then fail suddenly, and bradycardia in a child is usually a late sign of hypoxia rather than a heart problem.

Pulse: rate, rhythm, and strength — and the site depends on the patient

Take the pulse at the radial artery in a responsive adult or child, the carotid in an unresponsive adult or child, and the brachial in an infant, whose neck is too short to find a carotid reliably. Count for 30 seconds and double it; count a full 60 seconds if the rhythm is irregular, because doubling half of an irregular rhythm doubles the error with it.

Report three things, not one. Rate is the number. Rhythm is regular or irregular. Strength is strong, weak, or thready — and a weak thready pulse at a normal rate is a more worrying finding than a strong pulse at 110.

Respirations: count them without telling the patient you are counting

Breathing is the one vital sign under voluntary control, and a patient who knows you are counting their breaths will change them. The standard approach is to keep your fingers on the radial pulse after you have finished counting it and count respirations while the patient believes you are still on the pulse.

As with the pulse, the number is not the whole finding. Note depth (normal or shallow), effort (easy, labored, accessory muscle use, retractions), and any sounds — the wheezing, stridor, snoring and gurgling covered in the airway chapter. A rate of 20 that is shallow and labored is a sicker patient than a rate of 24 that is deep and easy.

Skin and pupils are the two vitals you assess by looking

Skin has three components. Color: pink is normal; pale suggests poor perfusion or blood loss; cyanotic (blue-gray) means poor oxygenation; flushed suggests heat exposure or certain poisonings; jaundiced (yellow) points to liver problems; mottled, a blotchy pattern, is a sign of poor perfusion seen particularly in children. In patients with darker skin, check the color of the nail beds, the inside of the lips, and the conjunctiva rather than the face. Temperature and condition: cool and clammy is the classic shock picture; hot and dry suggests heat stroke.

Capillary refill, measured by pressing a nail bed and releasing, should return within 2 seconds. It is a reliable perfusion indicator in children and less reliable in adults, where cold ambient temperature confounds it.

Pupils are remembered as PEARRL: Pupils Equal And Round, Regular in size, react to Light. Unequal pupils suggest a head injury or stroke; pinpoint pupils suggest opioids; widely dilated pupils suggest stimulants, hypoxia, or a drop in blood flow to the brain; pupils that are fixed and do not react at all are a serious neurological finding.

Trend the numbers, because one set of vitals is a snapshot and two sets are information

A single set of vital signs tells you where the patient is. Two sets tell you where they are going, which is the part that changes decisions. Reassess every 5 minutes for an unstable patient and every 15 minutes for a stable one, and document each set with a time, because a pressure that fell from 130 to 100 over ten minutes is a different patient from one who has been 100 all along.

Core vitals & rapid pulse-based BP estimate

The core vital signs are the pulse, respirations, the skin (its color, temperature, and condition), the pupils, and blood pressure (BP). Before a cuff is on the patient, the pulses you can feel say something about perfusion. A palpable radial pulse means blood is reaching the periphery; losing the radial pulse while a carotid pulse remains means the pressure has fallen far enough that it no longer does, a sign of significant shock. Older texts attach numbers to each site (radial about 80 mmHg, femoral 70, carotid 60), but when that rule was tested against measured pressures it overestimated them, so do not quote it as a reading.

A rough sign of perfusion only: measure the blood pressure as soon as you can.

Blood pressure methods & pulse oximetry

Blood pressure can be measured in three ways. By auscultation, you listen with a stethoscope for the Korotkoff sounds: the first sound you hear marks the systolic pressure, and the point at which the sound disappears marks the diastolic. By palpation, you feel for the return of the pulse as the cuff deflates; this gives the systolic pressure only. The third method is an automatic blood pressure monitor.

Pulse oximetry measures the percentage of hemoglobin that is saturated with oxygen (O2). It cannot tell you how the patient is breathing, only how saturated the blood is. A patient in obvious respiratory distress, with accessory muscle use and cyanosis, can still show 98% on the pulse oximeter, so the number never overrides what you see clinically. The reading is also unreliable with poor perfusion or shock, nail polish, cold extremities, and carbon monoxide poisoning, which produces a falsely high reading.

The technique errors that make a blood pressure reading wrong

A blood pressure is only as good as how it was taken, and the errors are systematic rather than random, which means they mislead in a predictable direction.

Cuff size is the most common. The bladder should cover roughly 80 percent of the circumference of the upper arm and about two-thirds of its length. A cuff that is too small reads falsely high; a cuff that is too large reads falsely low. This is why an adult cuff on a child's arm produces a reassuring number in a child who is not reassuring.

Arm position: the arm should be supported at the level of the heart. An arm held below heart level reads high; above, low. Deflation rate: about 2 mmHg per second. Deflating quickly skips past the true systolic and diastolic points and reads low and narrow.

Where not to take it: avoid an injured extremity, an arm with a dialysis fistula, an arm on the side of a previous mastectomy, and an arm with an IV running. Use the other arm.

Monitoring devices: glucose, and what capnography adds that pulse oximetry cannot

A blood glucose reading is useful only if you know the normal range and interpret the result together with the patient's mental status and history, never in isolation. A normal fasting value runs roughly 70–99 mg/dL, and a value below 70 mg/dL is the commonly used threshold for hypoglycemia. A patient with an altered mental status and no obvious cause has earned a glucose check.

Capnography measures exhaled carbon dioxide, normally about 35–45 mmHg, and it answers a question pulse oximetry cannot: whether the patient is ventilating, not merely whether their blood is saturated. That distinction matters most in exactly the situation where oximetry is most reassuring and most wrong — a patient on high-flow oxygen whose saturation stays high for minutes after their ventilation has become inadequate. Capnography also drops immediately when air stops moving, which is why it detects a displaced airway or a fall in perfusion faster than a saturation reading does.

The same caution applies to every device on this list: vitals and monitors refine a picture built from the patient in front of you, and they never replace it. Circulation in children in particular is assessed with different pulse points and a heavier reliance on capillary refill.