Author: Alexander A. Simakov, MPH FP-C MSIV, Medical Student Council, International Ex Officio Representative
Things were much simpler back in the Roman days. When one
was stabbed by a sword he/she bled and died of “cold” — or hypovolemic — shock.
If the person got lucky and was only wounded by the dirty blade, they probably
died of “warm” — or septic — shock. Today our knowledge has advanced well past
“cold” and “warm,” and leaves us with at least 10 types of shock commonly
encountered in the emergency department (ED) and intensive care unit (ICU)
(Table 1). Each represents a constellation of physiologic effects that require
a tailored approach to management. Cardiovascular support with the assistance
of vasopressors is a common method, while identification and treatment of the
underlying disease process remains the ultimate goal.1
Simply put, shock is inadequate end-organ perfusion. When
approaching a patient in shock, one must be aware of the various parameters
that may aid in the definitive diagnosis (Table 2), while other hints, such as
patient presentation and lab values, will be of initial benefit. Therefore, we
cannot completely discard the principles of “cold” and “warm,” but may rather
use them as primary markers and then focus on the ABGs,
lactic acid, urine output, invasive pressure monitoring and all those other
modern tools we now have available. While pulmonary artery catheterization was
popular in the past, recent trends show a decline since studies have failed to
show a benefit from its routine use.2-4
Institutional shock protocols may vary slightly, and
therefore, a definitive guide to the pharmacological selection process may not
apply here. However, a list of commonly used vasoactive medications is
presented in Table 3, and it is not uncommon to see a multitude of these agents
used at the same time as we try to balance out the body’s response to shock,
and assist it in its ultimate goal of survival. It is also of note that the
selection of the initial agent may simply be based on the patient’s current
cardiovascular status, i.e. heart rate and/or blood pressure, with subsequent
agents added as needed. What about fluid resuscitation? Generally speaking, we
have to “fill the tank” before applying vasopressors. This is particularly
important for hypovolemic and distributive shock, but may be tricky in
cardiogenic shock due to the potential for pulmonary edema. Clinical judgment
will guide you in selecting the proper volume of fluid resuscitation in shock
and recognizing when a fluid overload state has been reached (listen to those
lung sounds!).
References
1. Shoemaker WC. Temporal physiologic patterns of shock and
circulatory dysfunction based on early descriptions by invasive and noninvasive
monitoring. New Horiz. 1996; 4:300.
2. Connors AF Jr, Speroff T, Dawson NV, et al. The
effectiveness of right heart catheterization in the initial care of critically
ill patients. SUPPORT Investigators. JAMA.
1996; 276:889.
3. Harvey S, Harrison DA, Singer M, et al. Assessment of the
clinical effectiveness of pulmonary artery catheters in management of patients
in intensive care (PAC-Man): a randomised controlled trial. Lancet. 2005; 366:472.
4. Shah MR, Hasselblad V, Stevenson LW, et al. Impact of the
pulmonary artery catheter in critically ill patients: meta-analysis of
randomized clinical trials. JAMA.
2005; 294:1664.
5. http://circ.ahajournals.org/content/118/10/1047.full
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