As we
highlighted in the previous chapter, intraoperative management has great
influence for the surgical outcome and the anaesthetist plays a pivotal role
(12).

 

 

Fluid
management

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Different studies, demonstrated
the predictive relationship between the quantity of intraoperative fluid administrated
and the rate of postoperative complications in free flap (18, 19). From the
analysis on 154 patients with head and neck reconstruction with fibular free
flap, fluid volume greater than 5500 ml was associated with an increase in
medical and surgical complications, and volume greater than 7000 ml was
identified as the only significant risk factor for major complications (19). Free
flaps don’t present lymphatic drainage, therefore, every anaesthesiologist
needs to consider these characteristics in order to maintain intravascular
blood volume, prevent flap oedema and the pro-coagulant state due to rapid
administration of crystalloids (20). Regarding the use of colloids, data have
shown that volume higher than 20-30 ml/kg/24 h can increase perioperative
morbidity in this setting, and Hydroxyethyl starch seems more promising to
expand plasma volume and reduce blood viscosity if compared to gelatine-based colloids (21). Every patient can be
identified as fluid responsive by measuring cardiac output (CO), cardiac index
(CI), stroke volume, or pulse pressure variation (SVV, PPV).  According recent literature, a goal-directed
fluid therapy, titrated to keep SVV ?13%, with the use of mini invasive
arterial pulse contour device, results in improved oxygen delivery and reduces
the intravenous fluid administration, with better outcomes (22). We’ll discuss later on in this paper, other details
regarding haemodynamic monitoring.

 

Haemoglobin

 

Haemoglobin target is a sliding value in head and neck and
plastic microvascular surgery. In UK, as a resulted from a national survey, practice for blood loss in theatre is varied,
with a mean trigger for blood transfusion of Haemoglobin 7.8 g/dl (21). Even
if flap perfusion and peripheral oxygen delivery is a priority, several observational studies in head and
neck cancer have highlighted how allogenic blood transfusion is associated with
higher rate of postoperative complications and worse prognosis, and
anaesthesiologist usually follow blood conservation strategies in high-risk
patients (23).

 

 

Blood Pressure
(BP) management

 

BP management, again, is not
well standardised in this type of surgery, and enhancement of flap perfusion in
theatre is always a priority. The use of vasopressors in free flap surgery is a
matter of controversy. Evidence from animal models have revealed that the use
of vasopressors leads to vasoconstriction in the microcirculation of the flap,
however, this has not been shown in the clinical settings (24). According
different clinical studies, a general intraoperative well recognised target for
mean arterial blood pressure (MAP) during anastomosis is a value equal or major
than 70 mmHg, while a MAP lower than 60 mmHg is considered “hypotension” (25). Dobutamine and vasoconstrictors
can be safely used if the goals for BP and CI are not achieved with SVV