II. Clinical Evaluation of Shock and Low Cardiac Output States
Any patient at risk of developing LCO or shock requires thorough and
continuous monitoring of their hemodynamic status, responses to intervention, as
well as an evaluation of new physiologic derangements as they arise. Various
clinical, laboratory and physiologic variables are available to assess the
adequacy of CO and DO 2. Systemic perfusion is often assessed indirectly by
monitoring vital signs, signs of systemic perfusion as well as urine output.
Specifically, these include tachycardia, narrow pulse pressures, hypotension,
cold extremities, weak pulses, slow capillary refill, oliguria and/or anuria. In some
centers use of non-invasive tissue perfusion are routinely used in the intensive
care unit [1].
Vital Signs
Normative data is available for heart rate ranges based on age.
Tachycardia, especially if > 180-220 beats per minute, will compromise
ventricular filling and coronary artery filling time with a resultant decrease in SV,
CO and myocardial contractility. Tachycardia can occur secondary to pain,
agitation, acidosis, hypovolemia, anemia, hypoxemia, fever and low cardiac
output. It is also a compensatory mechanism to maintain CO early in the
development of cardiac tamponade. Tachyarrhythmias can also develop from a