As wehighlighted in the previous chapter, intraoperative management has greatinfluence for the surgical outcome and the anaesthetist plays a pivotal role(12). Fluidmanagement Different studies, demonstratedthe predictive relationship between the quantity of intraoperative fluid administratedand the rate of postoperative complications in free flap (18, 19). From theanalysis on 154 patients with head and neck reconstruction with fibular freeflap, fluid volume greater than 5500 ml was associated with an increase inmedical and surgical complications, and volume greater than 7000 ml wasidentified as the only significant risk factor for major complications (19). Freeflaps don’t present lymphatic drainage, therefore, every anaesthesiologistneeds to consider these characteristics in order to maintain intravascularblood volume, prevent flap oedema and the pro-coagulant state due to rapidadministration of crystalloids (20).
Regarding the use of colloids, data haveshown that volume higher than 20-30 ml/kg/24 h can increase perioperativemorbidity in this setting, and Hydroxyethyl starch seems more promising toexpand plasma volume and reduce blood viscosity if compared to gelatine-based colloids (21). Every patient can beidentified as fluid responsive by measuring cardiac output (CO), cardiac index(CI), stroke volume, or pulse pressure variation (SVV, PPV). According recent literature, a goal-directedfluid therapy, titrated to keep SVV ?13%, with the use of mini invasivearterial pulse contour device, results in improved oxygen delivery and reducesthe intravenous fluid administration, with better outcomes (22). We’ll discuss later on in this paper, other detailsregarding haemodynamic monitoring. Haemoglobin Haemoglobin target is a sliding value in head and neck andplastic 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). Evenif flap perfusion and peripheral oxygen delivery is a priority, several observational studies in head andneck cancer have highlighted how allogenic blood transfusion is associated withhigher rate of postoperative complications and worse prognosis, andanaesthesiologist usually follow blood conservation strategies in high-riskpatients (23). Blood Pressure(BP) management BP management, again, is notwell standardised in this type of surgery, and enhancement of flap perfusion intheatre is always a priority. The use of vasopressors in free flap surgery is amatter of controversy. Evidence from animal models have revealed that the useof vasopressors leads to vasoconstriction in the microcirculation of the flap,however, this has not been shown in the clinical settings (24).
Accordingdifferent clinical studies, a general intraoperative well recognised target formean arterial blood pressure (MAP) during anastomosis is a value equal or majorthan 70 mmHg, while a MAP lower than 60 mmHg is considered “hypotension” (25). Dobutamine and vasoconstrictorscan be safely used if the goals for BP and CI are not achieved with SVV<13-10%(26-28). no de?nitive consensus hasbeen reached regarding optimal ?uid protocols for patientsundergoing head and neck reconstruction with microvascu-lar free tissu e transfer.no de?nitive consensus hasbeen reached regarding optimal ?uid protocols for patientsundergoing head and neck reconstruction with microvascu-lar free tissu e transfer.no de?nitive consensus hasbeen reached regarding optimal ?uid protocols for patientsundergoing head and neck reconstruction with microvascu-lar free tissu e transfer.no de?nitive consensus hasbeen reached regarding optimal ?uid protocols for patientsundergoing head and neck reconstruction with microvascu-lar free tissu e transfer.no de?nitive consensus hasbeen reached regarding optimal ?uid protocols for patientsundergoing head and neck reconstruction with microvascu-lar free tissu e transGlycaemiccontrol Stress hyperglycaemiais a very common feature of complex patients: targets and relationships withoutcome are not clear, with contrasting results from literature (29).
Authorsfrom the national survey in UK evidenced how the majority of anaesthesiologist involvedin head and neck free flap reconstruction would commence an insulin infusionintra-operatively at a blood sugar level of 10–12 mmol/l, a minority of themwould use a slightly higher trigger of 12–14 mmol/l (21). The tight and fashinating link between insulin and the brain, with discernibleeffects on memory, learning abilities, and motor functions in fragile patientshas been widely explored in literature by Bilotta’s team (30). Type ofAnaesthesiaOnlyfew studies, evaluate the impact of anaesthesia management in microvascularreconstructive surgery. One of these, recently recorded the differences betweenpatients who received inhalation and total intravenous anaesthesia (TIVA) infree flap surgery (31). Patients in the TIVA group required less perioperativefluids (both crystalloid and colloid) to maintain hemodynamic stability,furthermore, after multivariate regression, patients in the TIVA group had asignificantly reduced risk of pulmonary complication compared with theinhalation group. Some anaesthetist may be concerned about the possibility ofmetabolic acidosis – propofol infusion syndrome – (PRIS), which would causedamage to a fresh anastomosis in flaps. Although there is an associationbetween PRIS and propofol infusion at doses higher than 4 mg/kg/h only if the whenduration of is greater than 48 h (32). Moreover, as part of a good anaestheticstrategy, patients undergoing head and neck or plastic cancer surgery should alwaysreceive intraoperative medications to mitigate postoperative nausea and/orvomiting (PONV) and a combination of corticosteroid and antiemetic is alwaysindicated (33).
? Antibiotics Many patients undergoing free flaps surgery have a number ofrisk factors potentially able to trigger postoperative infections (alcohol andsmoking abuse, radiation and chemotherapy, poor nutritional status, longoperation time). In this setting, antibiotic prophylaxis is still under debateand every centre have specific protocols. From a number of internationalstudies, the choice of antibiotic appears to affect the incidence ofpostoperative infections and flap site infections more than the duration (34,35). From a number of evidence ampicillin-sulbactam or cefuroxime are thepreferred prophylactic antibiotic for major clean-contaminated head and neckprocedures, 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). IntraoperativeMonitoring Againas a result form the UK national survey, a number of anaesthesiologist usedadditional monitoring including: core temperature, central venous pressure,bispectral index, cardiac output monitoring. Temperature monitoring is pivotal to ensure normothermia and the urinary bladder thermistor catheterhas been shown to correlate well with pulmonary artery thermistors (21, 38).Recentguidelines suggest that haemodynamic monitoring should be used in high riskpatients undergoing major surgery to enhance fluid optimisation, reduce mortality,morbidity and reduce costs.
Flo/Trac Vigileo system, based on arterial waveformanalysis, and patient’s age, sex, height, weight is often used in free flap reconstructivesurgery as mini invasive and reliable (39). As additional parameter, the recent “Hypotension ProbabilityIndicator” (HPI) could be promising: the advantage to predict a drop in themean arterial pressure, before hypotension occurs, can be more effective than a fluidtherapy titrated to maintain SVV less than 13% (40). Prospective studies arerequired to investigate the relationship between HPI and flap perfusion intheatre -Figure 2- (41). Figure 2. Hypotension probability indicator(HPI).
(From http://www.edwards.com/gb/devices/decision-software/hpi) Postoperative anaesthetic management andareas of controversy for patients undergoing microvascular reconstructivesurgery ITU admission A number of recent studies support that uncomplicated freeflap patients may be safely assisted outside ITU (42, 43). Panwar et al. recently,with an interesting cohort study, tried to understand if postoperativemanagement in ITU is necessary. Ninety-nine patients were included in thehistorical cohort of ICU patients, and 157 patients were enrolled in theprospective arm after creation of a head and neck surgical unit. They noted nosignificant changes in flap survival, inpatient morbidity, or mortality. Theydid, however, note a significant 1-day reduction of hospitalization and areduction in total costs (42,43).
From an interesting survey held in USA, nurses employed in an academic medical center and nurses with morethan 5 years of experience were significantly more comfortable with theirability to care for microsurgical patients (44). Ideally, uncomplicatedpatients receiving microvascular surgery should be stepdown in high-dependency units or equipped specialized surgical units, however, the pivotal role of nursing and health practitioner staff cannotbe underestimated, such as their workload. Early postoperative extubation and tracheostomy Airwaymanagement in patients undergoing major head and neck procedures with free flapreconstruction includes the protection of the airway if bleeding, swelling and oedemaoccur.
Surgical tracheotomy has rare severe complications but presents the dangerto prolong the hospital stay. According the last indications of ERAS protocols, the decision to perform atracheotomy is now linked to the presence specific conditions such as advancedcancer stage and location, otherwise, early extubation is always preferred (45). Early feeding Recent recommendations supportearly re-entrance of enteral nutrition in breast reconstructive microvascularsurgery and head and neck free flap patients (46, 47).
However, for head andneck patients, considerations as risk of wound dehiscence, fistula, andaspiration must be done. Recent studies compared early (prior topostoperative day 6) and late oral intake groups (postoperative day 6 or later)and the “early” group was not linked to any increased morbidity or adverseoutcome, at the same time, duration of hospital stay was lower (48, 49). Enteral feeding via either nasogastric (NG) or percutaneousendoscopic gastrostomy (PEG) tube is now recommended up to 12 h after surgery. Pain management Opioid-sparingand multimodal analgesia, prescribing NSAIDs, COX inhibitors, and paracetamol,is safe, effective, able to reduce narcotic side effects and to facilitaterapid recovery after surgery: when this approach is not sufficient, patient controlledanalgesia (PCA)can be eligible (50). For plastic reconstructive surgery, additional nerveblocks can be considered, such as the transversus abdominal plane block (TAPblock), while small catheter injecting local anaesthetics can be promising in anumber 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 toassess flap perfusion and viability including: Doppler, implantableDoppler, microdialysis, video-based application (Eulerian), fluorescenceangiography, near infrared spectroscopy (NIRS), contrast-enhanced duplex. Ofthese, 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 notoxygenated haemoglobin, has the advantage to be non-invasive, cheap, reliableand reproducible. In different studies, authors reported how regional oxygensaturation drops before the flap colour modified, improvingsalvage rates and decreasing flap losses(54, 55).
Mobilization & DVT prophylaxis Data on early mobilizationcome from studies in major abdominal procedures but few retrospective cohortstudies evidencedhow early mobilization (since day 1) withearly removal of drains, urinary and epidural catheter (sinceday 2), in head and neck and plastic reconstructive surgery is associatedwith fewer pulmonary complications (56, 57). For head and neck patients, early executionof speech and swallowing exercises should be respectively started since day 2and 4 after surgery (58). Different authors recommend for all microsurgerypatients a venous thrombosis prophylaxis since 6 h after surgery but, inpresence of an history of previous thrombosis or in presence of high score formacrovascular thrombosis (Caprini score is one of most valid in plasticreconstructive surgery -Figure3- ) aprompt referral to the haematology team should be considered (59, 60).
Figure 3. Caprini Score & algorithm. Conclusion Microvascularsurgery is among the best and advanced options for reconstruction in head andneck and breast fragile cancer patients.Anaestheticmanagement in these settings clearly affects the outcome and flap viability,however, evidences of standard care are still under investigation.
Main areasof controversy involve the need to develop standard multidisciplinary ERASprotocols, as well as standard perioperative management pathways (61, 62). Asdiscussed in this paper, the main fields of research and debate currently are: pre-operativerisk stratification, cardiac output monitoring and haemodynamic intraoperative targetslimits, intensive care admission indications, early extubation, mobilizationprotocols and pain management strategies. The necessity to embed anaesthetistsin new standard multidisciplinary recovery pathways makes their role as “perioperativedoctors” extremely challenging and the understanding conveyed in this paperwill guide future studies (21).