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Page 4 of 10 Krauss et al. Plast Aesthet Res 2018;5:39 I http://dx.doi.org/10.20517/2347-9264.2018.41

Figure 1. Remote ischemic conditioning: Examining the changes in tissue perfusion on the right hand of the test person after inducing
ischemia on the left arm with a tourniquet

green (ICG) angiography, dynamic infrared thermography (DIRT), and photospectrometry which facilitate
flap design [28,52,53] . One exception where ischemic preconditioning is routinely applied is the pedicled groin flap.
[54]
It still poses as a viable option when free or local flaps cannot be used to reconstruct tissue defects .
Remote ischemic conditioning
[55]
The idea of remote ischemic preconditioning was introduced by Przyklenk et al. in 1993 with their findings
in a dog model that brief cycles of ischemia in a remote vascular bed are also capable of protecting myocardial
cells from damage caused by the occlusion of coronary arteries. Plastic surgeons applied this idea to their
line of work. Today three forms of remote ischemic conditioning exist: pre-, per-, and post-conditioning. In
animal models it could be demonstrated that the induction of ischemia and reperfusion in a body part distant
from the flap prior to its elevation could reduce the occurrence of flap necrosis in adipocutaneous flaps as
well as in muscle flaps. They also found that ischemia and reperfusion could be induced non-invasively by
the application of a tourniquet on a body area distant from the flap prior to flap elevation [56,57] . After those
first promising results many experimental studies focused on the ideal type of application regarding remote
ischemic conditioning. They found that inflating the tourniquet on the upper extremity had better effects on
cutaneous microcirculation than on the lower extremity and that three circles of 10 min ischemia each were
superior to shorter cycles or more frequent applications [58,59] [Figure 1]. Those findings indicate that remote
ischemic preconditioning has to be a systemic phenomenon but the mechanisms behind “classic” and remote
ischemic conditioning are not yet fully understood. Various factors such as the release of nitric oxide, heat-
shock proteins, adenosine, ATP-sensitive K+ channels, cyclooxygenase as well as bradykinin through sensory
nerve stimulation seem to be involved [60-66] . The protective effect of remote ischemic preconditioning against
ischemia reperfusion-injury can be divided into two different timeframes. The acute effects last about four
hours after the initial application of the preconditioning stimulus whereas the late effects occur after 24 h and
[67]
last for at least another 24 h . Furthermore the clinical application of remote ischemic conditioning is rather
convenient as it is non-invasive and time-effective. The first study to examine remote ischemic conditioning
in the clinical setting regarding flap surgery has shown promising results including an improvement of
[68]
microcirculation in pedicled and free flaps . Although there are many promising results regarding remote
ischemic preconditioning there are also certain drawbacks. Some recent studies in the field of cardiac surgery
revealed that the positive effects of remote ischemic preconditioning in laboratory studies may not be applied
[69]
successfully in the clinical setting meaning there are no significant effects on the clinical outcome .
Thermic preconditioning
Other research groups have focused on the protective effects of hypo- and hyperthermia concerning