ZOLL IVTM™ System
Physicians' Manual
600248-001 Rev 3
21
Icy, Quattro & Solex Catheters
Cardiac Surgery
Afterdrop
Evidence that general hypothermia is of benefit to patients undergoing
cardiopulmonary bypass (CPB) has existed since the 1940’s. Not withstanding the
development of warm cardioplegia and beating heart techniques, hypothermic CPB
remain a standard method used in open-chest cardiac surgery. CPB is done with a
blood oxygenator system (“the pump”) that has high heat exchange capabilities.
Upon completion of the cardiac procedure, the blood is rewarmed nearly to
normothermia before discontinuing the bypass pump. After disconnection from the
bypass pump, it is common for patient’s body temperature spontaneously drop back
2º to 5ºC in the absence of interventions to the contrary [15]. This is thought to occur
due to thermodilution of core blood as peripheral vascular beds vasodilate post-
operatively. The patient would once again be hypothermic (termed “afterdrop”).
The effects of this “afterdrop” are varied. “Hypothermia predisposes the patient to
cardiac dysrrhythmia, increases systemic vascular resistance, precipitates shivering,
which increases oxygen consumption and carbon dioxide production, and impairs
coagulation. Furthermore, hypothermia causes a decrease in cardiac output by
producing bradycardia along with the increase in peripheral
vasoconstriction”[32][27][13][21].
Proper temperature control also requires that the patient not become hyperthermic.
As normal self-regulating mechanisms struggle to become reestablished, shivering
and other warming measures may produce “rebound” hyperthermia. Stevens’ (cit)
also found approximately 40% of the cardiopulmonary bypass patients they observed
reached hyperthermia four hours or more after arrival in the ICU. To avoid this
complication, Stevens and her group recommend discontinuation of active rewarming
efforts at 36.0ºC, and administration of acetaminophen to reduce additional
temperature increase upon achievement of normothermia. The concern of
hyperthemia is the increased metabolic demand results in greater cardiac work. A
device that warms a patient should, ideally, be able to prevent hyperthermia.
Fast-Track Recovery After Cardiac Surgery
The trend in post-operative care for patients recovering from CPB is to seek early
extubation and ambulation. This is termed the “fast-track” approach. The
development of the Fast Track recovery of CPB patients was driven primarily by a
desire to allow higher throughput in existing centers capable of supporting CPB.
Fast-track recovery produces shorter intubation time, and reduced intensive care and
overall lengths of stay. This approach involves optimization of all aspects of the CAB
procedures from the anesthetics used to the post-operative care. It has been shown,
however, that this can be done without increasing morbidity or mortality. Average
USA postoperative lengths of stay for isolated, primary elective CABG were 6.4 days
in 1997 with more complex cases averaging 10.5 days. Some authors report “Ultra-
Fast Track” results 70% of patients being discharged in less than or equal to 4 days
[25].
Typically patients are cared for in a cardiac surgery recovery area by cross-functional
teams with the aim being extubation within 4-6 hours after the termination of the
procedure [26][20][14][17]. “Safe extubation requires that the patient be alert and
