by Chew Keng Sheng
As the patient’s physiologic condition is dynamic and changes from time to time, we need to remember that the action plan is not static and can change in a moment. As such, we must not be too fixated with our earlier impression and fail or refuse to change it in light of discriminating evidence. This is further compounded by the challenge that the emergency department (ED) can be a high-acuity clinical environment that does not afford us the luxury of providing care in a structured manner as a low-acuity outpatient setting does.
Although establishing a definitive diagnosis is the goal in a conventional clinical approach, that is nearly impossible given the limited available clinical and laboratory data as well as the limited time we can spend with the patient in the ED. Unfortunately, establishing the definitive diagnosis may often be an unrealistic expectation of the general public. In fact, some patients are admitted to the hospital, and others are discharged home without a definitive diagnosis. Coming to terms with this unpleasant uncertainty of emergency medicine is necessary. It is, therefore, important to always maintain a healthy degree of skepticism in patient management by asking questions like, “What if I am wrong?” “What else could this presentation be due to?” “Do I have sufficient evidence to support or refute this diagnosis?”
A doctor working in the ED needs to have adequate knowledge of emergency conditions commonly presented to the ED. An emergency condition is any medical condition of sufficient severity (including intense pain) and when the absence of immediate medical attention could reasonably be expected to result in mortality and morbidity. Hence, unlike in conventional patient approaches, working in the ED requires a doctor first to ask this important question, “Is there a life or limb threatening condition that I must rule out in this patient”? A life-threatening condition is a threat to the airway, breathing, and circulation. Once a life or limb threatening condition is identified, interventions must be instituted immediately to address it before moving on to another form of examination and investigation.
Importance of Vital Signs
In addition to knowing emergency conditions, it is essential not to forget to look at the vital signs chart when formulating your action plan. Bear in mind that “normal” vital signs can be abnormal (Markovchick 2011). For example, an elderly patient with BP that usually ranges from 140 – 160/90 – 100 mmHg can mean that he is unstable with a BP of 110/70 mmHg and persistent vomiting and diarrhea. A patient with severe asthmatic exacerbations who was tachypneic and restless initially does not mean that he is now stable if he is “calmer” with a respiratory rate reduced to 10 breaths per minute. In other words, noting the trend of the vital signs is much more important than reading an isolated vital sign measurement.
Patients in the extreme age group may not mount a sufficient febrile response to an infection to cause an elevation in body temperature. Always remember to ask whether the patient has taken any anti-inflammatory or antipyretic medications (e.g., paracetamol, aspirin, non-steroidal anti-inflammatory drugs) before coming to the ED. The thermoregulatory center is located in the anterior hypothalamus; thus, any central nervous system infection or injury that affects the hypothalamus such as cerebrovascular accident and subarachnoid hemorrhage may affect thermoregulation. Certain drugs (e.g., anxiolytics, antidepressants, oral antihyperglycemics, beta-blockers), adrenal insufficiency, end-stage renal disease and thyroid disorders can also affect basal body temperature or temperature regulation.
When taking the pulse, the rate, regularity, and volume should be noted. The pulse rate should also be interpreted taking into consideration the patient’s age. For adolescents and adults, the maximum sustained HR estimation can be calculated with the this formula: maximum sustained HR = (220 – age in years) × 0.85.
Bradycardia is defined as a heart rate lower than 60 beats/min in adults. However, a well-conditioned athlete may have a normal resting heart rate as low as 30 to 40 beats/min. Ask also if the patient is taking any medication that could affect the pulse rate. For example, 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.
Physiologically, for every one-degree increase in Fahrenheit, the heart rate increases by ten beats/min. As 1 Celsius equals to 9/5 or 1.8 Fahrenheit, the increase of every one-degree Celsius results in an increase of pulse rate by 18 beats/min. This is known as the Leibermeister’s rule. However, there are conditions whereby the increase in temperature is not followed by an increased pulse rate. This is known as relative bradycardia (or the Faget sign). Causes of relative bradycardia can be divided into infective and non-infective causes. Infective causes include the following: Legionella, Psittacosis, Typhoid Fever, Typhus, Babesiosis, Malaria, Leptospirosis, Yellow fever, Dengue fever, Viral hemorrhagic fevers, Rocky Mountain spotted fever, etc. The non-infective causes beta-blockers (but not an angiotensin-converting-enzyme inhibitor, ACE inhibitor; calcium-channel blocker nor digoxin), central nervous system lesions (tumors and bleeds), lymphomas and drug fever (Cunha 2000).
The respiratory rate only informs us how fast or slow the breathing rate is; it does not inform us about the depth of the breathing or the oxygenation status of the patient. Therefore, besides looking at the rate, we should also pay attention to the depth of breathing and the pulse oximetry for the oxygen saturation.
Respiratory rate of >60 breaths per min in an acutely ill child under the age of 2 months is a predictor of hypoxia. Respiratory rate generally increases in the presence of fever; therefore, it can be difficult to determine whether the tachypnea is a primary finding of respiratory problems or is simply associated with the fever itself. Observe the breathing patterns of the patient as well. Look for any abnormal breathing patterns such as Cheyne-Stokes breathing (episodes of progressive shallow-deep-shallow cycles suggestive of stroke, trauma, carbon monoxide poisoning, and metabolic encephalopathy, etc.) and Kussmaul breathing (increased rate and depth of breathing). Click here for a video of Cheyne-Stokes breathing and a video of Kussmaul breathing.
Pulse oximetry is a non-invasive measurement of the oxygen saturation. The relationship between SaO2 and the partial pressure of arterial oxygen (PaO2) is described by the oxyhemoglobin dissociation curve (ODC). Because of the sigmoid shape of the ODC, a unit reduction of PaO2 change in this relatively flat portion of the ODC produces only a small change in SaO2 as compared to a unit of reduction of PaO2 in the relatively steep part of the curve that produces a much greater degree of reduction of PaO2. The point of intersection between the relatively flat portion of the curve and the relatively steep portion of the curve is known as the ICU point, and it corresponds to a SaO2 of around 92% and the PaO2 of 60 mmHg. Therefore, always attempt to maintain the SaO2 above 92%. PaO2 below 60 mmHg means that the patient can markedly desaturate. Conversely, at a PaO2 above 60 mmHg, increasing the PaO2 will not result in a marked increase in the SaO2. In fact, giving too much supplemental oxygen may result in an ever increasing PaO2 with a SaO2 maintained at 100%. Hyperoxia (too high PaO2) can be harmful as it can lead to adverse effects such as generation of reactive oxygen species and release of angiotensin II resulting in vasoconstriction. (Click here to access two articles for more explanation and diagrams: Hooley J. Decoding the Oxyhemoglobin Dissociation Curve and Brandis, K. Oxygen Dissociation Curve.
Blood pressure, defined as the force exerted by blood on the vessel wall, only indirectly measures perfusion, as blood flow equals to the change in pressure divided by resistance. But because peripheral vascular resistance varies, normal blood pressure does not necessarily mean good tissue perfusion. The normal blood pressure may be “maintained” by an increase in peripheral vascular resistance. Furthermore, hypotension is a late sign of shock; this is especially true in children. For example, in class II hemorrhagic shock (with a loss of 15%–30% blood volume), the findings usually include tachycardia, tachypnea, cool, clammy skin, and delayed capillary refill. However, the systolic blood pressure (BP) is still within the normal range even though the pulse pressure is decreased. The decrease in pulse pressure is due to the increased levels of circulating catecholamines, causing an increase in peripheral vascular resistance, and raising the diastolic BP.
For children, the blood pressure measurement varies according to age. A formula for estimating the 95th percentile BP (normal) in young children is as follows: BP = 80 + (2 x age in years). Hypotension is defined as less than the 5th percentile BP that can be estimated by the following formula: hypotension = less than 70 + (2 x age in years).
The algorithm of data gathering and creation of an action plan in the ED is shown below.
References and Further Reading
- Markovchick VJ. Chapter 1 – Decision making in emergency medicine. In: Markovchick VJ, Pons PT, Bakes KM eds. Emergency Medicine Secrets. 5th ed. Saint Louis: Mosby; 2011. p. 7-10.
- Cunha BA. The diagnostic significance of relative bradycardia in infectious disease. Clin Microbiol Infect 2000;6(12):633-4.
- Cheyne-Stokes breathing (https://www.youtube.com/watch?v=zrcXQhFK6ro) and a video of Kussmaul breathing (https://www.youtube.com/watch?v=TG0vpKae3Js).
- Hooley J. Decoding the Oxyhemoglobin Dissociation Curve. Available at URL: http://www.americannursetoday.com/wp-content/uploads/2014/12/ant1-CE-Oxyhemogglobin-1219.pdf and Brandis, K. Oxygen Dissociation Curve Available at URL: www.anaesthesiamcq.com/downloads/odc.pdf