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<13-10% (26-28).     no de?nitive consensus has been reached regarding optimal ?uid protocols for patien ts undergoing head and neck reconstruction with microvascu- lar free tissu e transfer. no de?nitive consensus has been reached regarding optimal ?uid protocols for patien ts undergoing head and neck reconstruction with microvascu- lar free tissu e transfer. no de?nitive consensus has been reached regarding optimal ?uid protocols for patien ts undergoing head and neck reconstruction with microvascu- lar free tissu e transfer. no de?nitive consensus has been reached regarding optimal ?uid protocols for patien ts undergoing head and neck reconstruction with microvascu- lar free tissu e transfer. no de?nitive consensus has been reached regarding optimal ?uid protocols for patien ts undergoing head and neck reconstruction with microvascu- lar free tissu e trans Glycaemic control   Stress hyperglycaemia is a very common feature of complex patients: targets and relationships with outcome are not clear, with contrasting results from literature (29). Authors from the national survey in UK evidenced how the majority of anaesthesiologist involved in head and neck free flap reconstruction would commence an insulin infusion intra-operatively at a blood sugar level of 10–12 mmol/l, a minority of them would use a slightly higher trigger of 12–14 mmol/l (21). The tight and fashinating link between insulin and the brain, with discernible effects on memory, learning abilities, and motor functions in fragile patients has been widely explored in literature by Bilotta's team (30).       Type of Anaesthesia Only few studies, evaluate the impact of anaesthesia management in microvascular reconstructive surgery. One of these, recently recorded the differences between patients who received inhalation and total intravenous anaesthesia (TIVA) in free flap surgery (31). Patients in the TIVA group required less perioperative fluids (both crystalloid and colloid) to maintain hemodynamic stability, furthermore, after multivariate regression, patients in the TIVA group had a significantly reduced risk of pulmonary complication compared with the inhalation group. Some anaesthetist may be concerned about the possibility of metabolic acidosis - propofol infusion syndrome - (PRIS), which would cause damage to a fresh anastomosis in flaps. Although there is an association between PRIS and propofol infusion at doses higher than 4 mg/kg/h only if the when duration of is greater than 48 h (32). Moreover, as part of a good anaesthetic strategy, patients undergoing head and neck or plastic cancer surgery should always receive intraoperative medications to mitigate postoperative nausea and/or vomiting (PONV) and a combination of corticosteroid and antiemetic is always indicated (33).?   Antibiotics   Many patients undergoing free flaps surgery have a number of risk factors potentially able to trigger postoperative infections (alcohol and smoking abuse, radiation and chemotherapy, poor nutritional status, long operation time). In this setting, antibiotic prophylaxis is still under debate and every centre have specific protocols. From a number of international studies, the choice of antibiotic appears to affect the incidence of postoperative infections and flap site infections more than the duration (34, 35). From a number of evidence ampicillin-sulbactam or cefuroxime are the preferred prophylactic antibiotic for major clean-contaminated head and neck procedures, less than or equal to 24 hours of antibiotic prophylaxis is likely sufficient, Clindamycin prophylaxis increases the risk of recipient surgical site infection, moreover, for patients with penicillin allergy, broader gram-negative coverage is recommended (34, 36, 37).     Intraoperative Monitoring   Again as a result form the UK national survey, a number of anaesthesiologist used additional monitoring including: core temperature, central venous pressure, bispectral index, cardiac output monitoring. Temperature monitoring is pivotal to ensure normothermia and the urinary bladder thermistor catheter has been shown to correlate well with pulmonary artery thermistors (21, 38). Recent guidelines suggest that haemodynamic monitoring should be used in high risk patients undergoing major surgery to enhance fluid optimisation, reduce mortality, morbidity and reduce costs. Flo/Trac Vigileo system, based on arterial waveform analysis, and patient's age, sex, height, weight is often used in free flap reconstructive surgery as mini invasive and reliable (39). As additional parameter, the recent "Hypotension Probability Indicator" (HPI) could be promising: the advantage to predict a drop in the mean arterial pressure, before hypotension occurs, can be more effective than a fluid therapy titrated to maintain SVV less than 13% (40). Prospective studies are required to investigate the relationship between HPI and flap perfusion in theatre -Figure 2- (41).     Figure 2.  Hypotension probability indicator (HPI).                                                                                 (From http://www.edwards.com/gb/devices/decision-software/hpi)       Postoperative anaesthetic management and areas of controversy for patients undergoing microvascular reconstructive surgery     ITU admission     A number of recent studies support that uncomplicated free flap patients may be safely assisted outside ITU (42, 43). Panwar et al. recently, with an interesting cohort study, tried to understand if postoperative management in ITU is necessary. Ninety-nine patients were included in the historical cohort of ICU patients, and 157 patients were enrolled in the prospective arm after creation of a head and neck surgical unit. They noted no significant changes in flap survival, inpatient morbidity, or mortality. They did, however, note a significant 1-day reduction of hospitalization and a reduction in total costs (42,43). From an interesting survey held in USA, nurses employed in an academic medical center and nurses with more than 5 years of experience were significantly more comfortable with their ability to care for microsurgical patients (44). Ideally, uncomplicated patients receiving microvascular surgery should be step down in high-dependency units or equipped specialized surgical units, however, the pivotal role of nursing and health practitioner staff cannot be underestimated, such as their workload.   Early postoperative extubation and tracheostomy     Airway management in patients undergoing major head and neck procedures with free flap reconstruction includes the protection of the airway if bleeding, swelling and oedema occur. Surgical tracheotomy has rare severe complications but presents the danger to prolong the hospital stay. According the last indications of ERAS protocols, the decision to perform a tracheotomy is now linked to the presence specific conditions such as advanced cancer stage and location, otherwise, early extubation is always preferred (45).   Early feeding     Recent recommendations support early re-entrance of enteral nutrition in breast reconstructive microvascular surgery and head and neck free flap patients (46, 47). However, for head and neck patients, considerations as risk of wound dehiscence, fistula, and aspiration must be done. Recent studies compared early (prior to postoperative day 6) and late oral intake groups (postoperative day 6 or later) and the "early" group was not linked to any increased morbidity or adverse outcome, at the same time, duration of hospital stay was lower (48, 49). Enteral feeding via either nasogastric (NG) or percutaneous endoscopic gastrostomy (PEG) tube is now recommended up to 12 h after surgery.   Pain management     Opioid-sparing and multimodal analgesia, prescribing NSAIDs, COX inhibitors, and paracetamol, is safe, effective, able to reduce narcotic side effects and to facilitate rapid recovery after surgery: when this approach is not sufficient, patient controlled analgesia (PCA) can be eligible (50). For plastic reconstructive surgery, additional nerve blocks can be considered, such as the transversus abdominal plane block (TAP block), while small catheter injecting local anaesthetics can be promising in a number of head and neck reconstruction such as free flaps with fibular harvest (51, 52).   Flap perfusion monitoring     Postoperatively, a number of different instruments are accountable to assess flap perfusion and viability including: Doppler, implantable Doppler, microdialysis, video-based application (Eulerian), fluorescence angiography, near infrared spectroscopy (NIRS), contrast-enhanced duplex. Of these, implantable arterial Doppler have recent and wide set of data showing efficacy, less false-positive and less flow variability (53, 54). NIRS on the other side, based on the differential absorption of light by regional oxygenated and not oxygenated haemoglobin, has the advantage to be non-invasive, cheap, reliable and reproducible. In different studies, authors reported how regional oxygen saturation drops before the flap colour modified, improving salvage rates and decreasing flap losses (54, 55).     Mobilization & DVT prophylaxis     Data on early mobilization come from studies in major abdominal procedures but few retrospective cohort studies evidenced how early mobilization (since day 1) with early removal of drains, urinary and epidural catheter (since day 2), in head and neck and plastic reconstructive surgery is associated with fewer pulmonary complications (56, 57). For head and neck patients, early execution of speech and swallowing exercises should be respectively started since day 2 and 4 after surgery (58). Different authors recommend for all microsurgery patients a venous thrombosis prophylaxis since 6 h after surgery but, in presence of an history of previous thrombosis or in presence of high score for macrovascular thrombosis (Caprini score is one of most valid in plastic reconstructive surgery -Figure3- ) a prompt referral to the haematology team should be considered (59, 60).                                                   Figure 3. Caprini Score & algorithm.   Conclusion     Microvascular surgery is among the best and advanced options for reconstruction in head and neck and breast fragile cancer patients. Anaesthetic management in these settings clearly affects the outcome and flap viability, however, evidences of standard care are still under investigation. Main areas of controversy involve the need to develop standard multidisciplinary ERAS protocols, as well as standard perioperative management pathways (61, 62). As discussed in this paper, the main fields of research and debate currently are: pre-operative risk stratification, cardiac output monitoring and haemodynamic intraoperative targets limits, intensive care admission indications, early extubation, mobilization protocols and pain management strategies. The necessity to embed anaesthetists in new standard multidisciplinary recovery pathways makes their role as "perioperative doctors" extremely challenging and the understanding conveyed in this paper will guide future studies (21).