- Delayed flap transfer involves partially raising a flap and dividing some of its blood supply at a preliminary stage to deliver a sublethal ischemic insult, stimulating vessel dilation, ischemic preconditioning, and neovascularization. - This allows for axialization of blood flow and conditioning of flap tissues to lower oxygen levels before full transfer, improving vascularity and survival. - Surgical delay specifically refers to segmentally interrupting blood supply to tissue like skin or muscle in stages over time to gradually extend vascular inflow to the distal flap portion.

1. Flap delay
Delayed transfer in pedicle flap was introduced by
Blair 1921
Delayed flap is one in which a preliminary surgical
stage is planned to partially raise the flap and divide a
portion of the blood supply, delivering a sublethal
ischemic insult that stimulates vessel dilation, ischemic
preconditioning, and neovascularization.
This allows for axialization of blood flow and
conditioning of the flap tissues to lower oxygen levels
in anticipation of flap transfer at a second stage. (Grabb
&Smith)
Flap delay consists in the segmental interruption of
blood supply to a piece of tissue (most commonly skin,
but can be muscle as well) in a staged manner so that
the vascular inflow from the main pedicle pgradually
extends to the distal portion of the flap, which would
otherwise not survive if raised in one stage. (Plastic
surgery key)
My definition
Partial interruption of blood supply to a piece of tissue
in a staged manner, delivering a sublethal ischemic
insult that stimulates vessel dilation, ischemic
preconditioning, and neovascularization so as to
improve the vascularity, survival and extend of the flap.

2. - “Delay procedure” is a surgical interruption of a
portion of the blood supply to a flap at a
preliminary stage before transfer with the goal of
increasing the surviving length of the flap
- “Delay phenomenon” is an increase in flap
survival length attributed to a previous surgical
delay.
Methods to do delay (augmentation of pedicle flap
viability)
- Mechanical
- Vascular
- Chemical
Surgical delay
Standard delay
Strategic delay
Pharmacological delay
A. Surgical delay
I. Standard delay
1. Bipedicle delay
Specifically, a skin flap is mapped out on the donor site
and incised on its two longitudinal sides. The flap is
then undermined to form a bipedicle flap and is sutured
back to the donor site.
Two to three weeks after construction of the bipedicle
flap, the third side (distal end) is cut in one or two
stages at 2–3 days apart.

3. At the end of this stage, a single pedicle flap is
completely raised and the distal portion of the flap is
moved to the recipient site for wound coverage without
skin necrosis.
Surgical delay increased skin flap capillary blood flow
between 2 and 7 days of delay. This increase in
capillary blood flow was mainly in the distal random
portion of the delayed skin flaps.
2. Outline delay
3. Partial flap raising
II. Strategic delay/Vascular delay
Vascular delay by embolization does not require
general anesthesia, but it requires local anesthesia and
catheterisation performed in the interventional
radiology department.
⁃ Open
⁃ Endoscopic
⁃ Endovascular
B. Nonsurgical Flap Delay
Using flash lamp-pumped pulsed-dye laser at a
wavelength of 585 nm, it was demonstrated that laser
delay is as effective as surgical delay Methods
⁃ Lasering lateral borders leads to dilation and
longitudinal rearrangement of the existing vessels
rather than angiogenesis,
⁃ Lasering the entire surface results in delay effect by
inducing angiogenesis due to activation and
degranulation of the mast cells (Ercocen et al.
2003).

4. Another group found that CO 2and Erbium: YAG lasers
are as effective as surgery for delay of skin flaps in the
rat model
C. Chemical delay
Chemical delay has also been studied as an alternative
to surgical delay. In a rat skin flap model, although not
as effective as the surgical delay procedure, the topical
combination of nicoboxil and nonivamide proved to be
of significant value in order to ameliorate ischemic
necrosis in experimental skin flaps.
Mechanism of surgical delay in augmentation of
pedicle flap viability
1. Surgical delay procedure reduces arteriovenous
(AV) shunt flow
Reinisch, hypothesized that, in acute skin flap surgery,
distal ischemic necrosis was caused by opening of AV
shunt flow as a result of sympathetic denervation.
He speculated that shunt flow occurred throughout the
skin flap and the flow in the proximal areas is sufficient
to supply both the AV and by capillary (nutrient) blood
flow, but the shunting became lethal in the distal areas
of the skin flap where the total blood flow was low.
In surgical delay, the bipedicle skin flap provided
sufficient blood supply during the early period of
sympathetic denervation and opening of AV shunts.

5. Reinisch’s hypothesis, and also suggested that surgical
delay allowed the skin flap to recover from its
hyperadrenergic state before converting the bipedicle to
single-pedicle skin flaps.
Taken together, these studies seem to indicate that AV
shunt flow does not play an important role in the
pathogenesis of distal ischemic necrosis in acute
pedicle skin flaps.
2. Surgical delay procedure depletes vasoconstriction
and prothrombotic substances in the skin flap
Local tissue content of vasoconstricting and
prothrombotic substances such as NE, TXA2, 5HT and
ET-1 are known to be elevated by surgical trauma.
The surgical delay procedure reduces local production
and also allows time to deplete the vasoconstricting and
prothrombic substances before converting the bipedicle
flap to single-pedicle flaps.
3. Surgical delay procedure induces vascular territory
expansion by opening existing choke arteries
We found that the capillary blood flow increased
significantly within 2 days of delay and a maximum
increase in skin flap capillary blood flow occurred
between 2 and 3 days of delay, and remained
unchanged between 4 and 14 days of delay without an
increase in density of arteries (arteriogenesis) assessed
by histology.

6. This increase in capillary blood flow occurred mainly
in the distal portion of the skin flap.
Therefore, these investigators described this
phenomenon as vascular territory expansion by
recruitment (opening) of existing arteries,
This phenomenon was labeled by these investigators as
angiosome territory expansion by opening of existing
choke blood vessels.
4. Surgical delay procedure induces angiogenesis
These investigators speculated that these cytokines
induced vasodilation and angiogenesis to augment skin
paddle viability in rat TRAM flaps.
5. Surgical delay is a perfusion preconditioning
technique in reconstructive soft tissue flap surgery
The purpose of the technique is to allow for enhanced
flap length and viability in reconstruction
6. Changes in Sympathetic Tone
Upon delayed flap elevation, the hyperadrenergic state
abates when the nerve endings are depleted of
norepinephrine, and vasodilation ensues, thus
increasing the blood supply and tissue viability
7. Dilation and Reorientation of Vessels

7. 8. Changes in Metabolism
Preconditioned tissues demonstrate decreased energy
requirements, altered energy metabolism, improved
electrolyte homeostasis, less-reactive oxygen species,
reduced release of activated neutrophils, reduced
apoptosis, and better perfusion, resulting in an increase
of the ischemic tolerance of tissues.

8. Regression of edema
inflammation caused by first
surgery
Loss of second vasoconstrictor system
Sensitisation of beta receptors
Direct smooth muscle action by unknown agent
Change in vascular architecture
Changes in metabolism