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Use of Intra-aortic balloon pump (IABP)

Hemodynamic management
Hypotension and low cardiac output

BP = CO x SVR
CO = HR x SV (stroke volume)
Stroke volume is determined by preload, contractility, and afterload
Bradycardias or tachydysrhythmias that decrease ventricular filling can decrease C.O.
There are numerous causes for hypotension post-operatively. Proper management of the hypotensive patient in the ICU requires that the precise etiology for the hypotension is determined and therapy is directed towards reversal of this specific problem. Equation 1 demonstrates that hypotension can be caused by a “pump problem” (low cardiac output) or a low SVR (arterial “circuit” problem). The following is an approach to managing the hypotensive patient;

Look at the recent hemodynamic parameters.
Assess the cardiac output/index. Is this a “pump” problem? Or is it due to low SVR?
Look at the cardiac rhythm.
Look at the CVP to assess preload.
Is the afterload high ?
Is contractility decreased ?
Is this tamponade? Is this an acute graft occlusion or spasm? Is this an acute dehiscence of a valve repair?
Look at the recent hemodynamic parameters obtained from the Swan-Ganz catheter. Obtain another set as soon as possible if they have not recently been done or if there has been a sudden change.
Assess the cardiac output/index.
If the cardiac index is in the normal range or high, then the patient does not have a significant “pump” problem and the cause of the hypotension is secondary to diminished peripheral arterial tone (low SVR). A vasopressor agent should be considered. The differential diagnosis of low SVR includes;
SIRS – a proportion of patients post CPB will have significant cytokine increases
Sepsis
Anaphylactic or anaphylactoid reactions including protamine reactions,
Drug-induced, toxicological – nitrates, antihypertensives, narcotics and sedatives, etc
Adrenal insufficiency (Was the patient steroid dependent pre-operatively?)
Hyperthyroidism, hypothyroidism,
Neurogenic (spinal) shock