Clinical Review ABC of intensive care

Circulatory support

BMJ 1999; 318 doi: (Published 26 June 1999) Cite this as: BMJ 1999;318:1749
  1. C J Hinds,,
  2. D Watson

    Circulatory support is required not only for hypotension or shock but also to prevent complications in patients at risk of organ failure. Shock can be defined as “acute circulatory failure with inadequate or inappropriately distributed tissue perfusion resulting in generalised cellular hypoxia.” It is a life threatening medical emergency.

    Types of shock

    • Cardiogenic shock: caused by “pump failure”—for example acute myocardial infarction

    • Obstructive shock: caused by mechanical impediment to forward flow—for example, pulmonary embolus, cardiac tamponade

    • Hypovolaemic shock: caused by loss of circulating volume. These losses may be exogenous (haemorrhage, burns) or endogenous (through leaks in the microcirculation or into body cavities as occurs in intestinal obstruction)

    • Distributive shock: caused by abnormalities of the peripheral circulation—for example, sepsis and anaphylaxis

    Tissue perfusion may be jeopardised by cardiogenic, obstructive, hypovolaemic, or distributive shock. These factors often combine. For example, in sepsis and anaphylaxis, vascular dilatation and sequestration in venous capacitance vessels lead to relative hypovolaemia, which is compounded by true hypovolaemia due to fluid losses through increased microvascular permeability.

    Continuous monitoring of blood pressure. A cannula placed percutaneously in an artery is connected to a pressure transducer through a fluid filled non-compliant manometer line incorporating a continuous and intermittent flush device. Adapted from Hinds CJ, Watson D. Intensive care: a concise textbook. WB Saunders, 1996.

    If abnormalities of tissue perfusion are allowed to persist, the function of vital organs will be impaired. The subsequent reperfusion will exacerbate organ dysfunction and, in severe cases, may culminate in multiple organ failure. Early recognition of patients who are shocked and immediate provision of effective circulatory support is therefore essential. Such support is usually best provided in an intensive care unit or high dependency area.

    Cardiovascular monitoring

    Blood pressure

    Patients with a low cardiac output can sometimes maintain a reasonable blood pressure by vasoconstriction, while vasodilated patients may be hypotensive despite …

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