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​Overview and Implications

Shock is a state of organ hypoperfusion with resultant cellular dysfunction and death. Mechanisms may involve decreased circulating volume, decreased cardiac output, and vasodilation, sometimes with shunting of blood to bypass capillary exchange beds (Procter, 2020). It is a clinical state that occurs when a mismatch arises between oxygen supply and metabolic demand, resulting in cellular hypoxia. If not recognized and treated appropriately, shock will ultimately progress to organ failure (Broussard & Ural, 2018; Gaieski & Mikkelsen, 2018; Vincent & De Backer, 2013). It is one of the leading causes of death in hospitalized patients (Nichol & Ahmed, 2014).

There are several types of shock that a patient may experience during or after a procedure.  Mechanisms of organ hypoperfusion and shock may be due to a low circulating volume (hypovolemic shock), vasodilation (distributive shock), a primary decrease in cardiac output (both cardiogenic and obstructive shock), or a combination of all of them. Untreated shock is usually fatal. Even with treatment, mortality from cardiogenic shock after myocardial infarction [MI] (60 to 65 per cent) and septic shock (30 to 40 per cent) is high. Prognosis depends on the cause, preexisting or complicating illness, time between onset and diagnosis, and promptness and adequacy of therapy (Procter, 2020).

Organ dysfunction in patients can be represented by an increase in the Sequential Organ Failure Assessment (SOFA) score (Vincent et al., 1996) of two points or more, which is associated with an in-hospital mortality greater than 10 per cent. Patients with septic shock can be identified by a vasopressor requirement to maintain a mean arterial pressure of 65 mm Hg or greater AND serum lactate level greater than 2 mmol/L in the absence of hypovolemia (i.e. after adequate fluid resuscitation). This combination is associated with hospital mortality rates greater than 40 per cent (Singer et al., 2016).

Table 1 was created by Dr. Denny Laporta at the Jewish General Hospital, McGill University, Montreal, QC (Laporta, 2018). The table summarizes the various types of shock that may be encountered in the peri-procedure period. In hypovolemic shock the reduced cardiac output is due to a reduction in circulating volume and consequent venous return. It may be due to hemorrhage or when large volumes of fluid are lost perioperatively – expectedly or unexpectedly.

Table 1: Examples of shock1 occurring during or after a procedure

Peri-Procedure Period Type of shock Causes
HypovolemicBleeding
  • Excess loss of non-blood fluid
    •  Drainage
    •  3rd-spacing
CardiogenicMyocardial Infarction
  • Pre-existing
    • Cardiomyopathy (hypertrophic dilated)
    • Valvulopathy
ObstructivePulmonary embolism
  • Tension pneumothorax
  • Cardiac tamponade

Distributive

 

Septic syndrome
  • Other (non-infectious) causes of systemic inflammatory response (SIRS):
    • Anaphylaxis
    • Transfusion reaction
  • Other adverse drug reactions:
    • Antihypertensives
    • Anesthetics
  • Spinal shock (neuraxial blockade)
  • Adrenal insufficiency (chronic steroid use)
  • Miscellaneous
    • Burns
    • Liver failure
    • Thyroid storm

1These may occur as single causes or in combination

Goal

Reduce the incidence of procedure-associated shock.

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