**3.2 Monitoring fluid and transfusion administration**

All anesthesia techniques may undergo complications. Patient monitoring cannot prevent all adverse events, but there is clear evidence that its application reduces perioperative risks [38, 39]. Total hip replacement surgery can be performed either under general or locoregional anesthesia, and the monitoring must clearly follow standards. All patients should receive electrocardiographic tracing, pulse oximeter, and frequency monitoring. Blood pressure can be reached by noninvasive measurement every 3–5 minutes, otherwise by different interval according to the clinician's opinion [40]. Additional monitoring such as invasive blood pressure, echocardiography, central venous pressure, cardiac output, or other derivative parameters can be adopted in high complexity patients [40, 41]. During general anesthesia and deep sedation, patient's ventilation must be monitored continuously by capnometry in order to confirm a correct ventilation, wherein signs such as respiratory excursions, respiratory rate, and chest auscultation can integrate instrumental monitoring. Although often patients undergoing hip replacement surgery are in spontaneous breathing, capnometry can be used in these cases. Patient's body temperature should also be monitored during anesthesia or sedation in order to minimize patient's discomfort and risk of bleeding. Temperature monitoring and active control systems should be systematically used either in subjects particularly vulnerable to the risk of unintentional hypothermia, such as children and elderly, or during long-lasting procedures with extensive tissue exposure [41]. When neuromuscular blockers are administered, a peripheral stimulator must be available for the monitoring of neuromuscular transmission, and the resumption of normal activity must be measured by the train-of-four (TOF) monitoring. In the last 15 years, specific brain monitoring systems have been introduced into clinical practice. They are based on the analysis of electroencephalogram (EEG) processing or on evoked potentials. However, their use in the routine cannot be considered an integral part of standard monitoring although their use is strongly recommended during total intravenous anesthesia. However, the literature on the possibility of preventing intraoperative awareness using brain monitoring is quite controversial [42, 43]. The use of goal-directed fluid protocols in intermediate-risk patients undergoing hip replacement was studied in few clinical trials. A fluid protocol based on pulse pressure variation (PPV) assessed using continuous invasive arterial pressure measurement seems to be associated with a reduction in postoperative complications and red blood cell transfusion as compared to standard no-protocol treatment [44, 45]. The goal-directed fluid therapy can be guided, in addition to standard monitoring (invasive blood pressure), with devices using pulse contour analysis able to extrapolate the main hemodynamic parameters from the analysis of the pressure wave. Some studies show that by maximizing the stroke volume and the oxygen delivery index, there is a reduction of postoperative complication and a reduction of hospitalization [44, 45]. The rotational thromboelastometer is a point-of-care instrument that studies the viscoelastic properties of whole blood

#### *Anesthesia for Hip Replacement DOI: http://dx.doi.org/10.5772/intechopen.104666*

and graphically displays the properties of the clot and its kinetics, from formation to lysis. In particular, it determines the clotting time, the initial time of fibrin formation, the kinetics of fibrin formation and clot development, the strength and stability of the clot, the lysis time, and the platelet function. The thromboelastometer is indicated for the diagnosis, treatment, and monitoring of hemostasis during perioperative bleeding. Among the most frequent causes of bleeding, fibrinolysis is an important one and may be prevented by the infusion of tranexamic acid (TXA) before surgery. Tranexamic acid (TXA) is a synthetic substance, structurally attributable to the amino acid lysine. Tranexamic acid blocks the lysine binding site on the fibrinolytic enzyme plasmin, which is essential for binding plasmin to fibrin. In this way, the fibrinolysis is blocked. TXA reduces blood loss and transfusion administration regardless of the surgical technique. With intravenous preoperative routine use these benefits were seen with both the anterior surgical approach and bilateral hip replacement [46, 47]. The usual dosage of TXA consists of an initial dose of 10–15 mg/kg before surgery that may be followed by an infusion of 1 mg/kg/hour over 4–6 hours or by repeating the initial dose in the postoperative period according to the presence or high risk of bleeding. Recently, local TXA administration in total hip replacement has been investigated, but its use is still controversial. The local application of TXA has been suggested in the consideration of some potential advantages such as easy application, directly affecting the bleeding site, minimizing systemic drug absorption, and, thus, reducing the potential complications of intravenous TXA administration. Local administration should be performed at the end of the surgery, once the fascia is closed, with local injection of 2 g of TXA [48]. In support of this practice, it has been reported that the intravenous use of TXA in total hip replacement significantly reduced blood loss and blood transfusion rates [49]. A recent study shows that the addition of oral TXA for 24 hours postoperatively does not reduce blood loss beyond that achieved with a single 1-g IV perioperative dose alone [50]. An assessment of the risks and benefits in patients is usually recommended. Indeed, in patients with previous thromboembolic events, over 60 years of age, female sex, or undergoing oncological surgery, there is a hypercoagulability's induction and may be not recommended to administer a dose following the initial bolus. As fibrinogen ensures clot formation, the preoperative dosage in patients undergoing elective hip surgery is strongly recommended. Its monitoring during intraoperative bleeding allows for an early supplementation. Fibrinogen's concentrates are the most used molecules. The most recent published guidelines indicate the trigger levels of fibrinogenemia <1.5–2 g/L during massive bleeding. When the indication comes from the monitoring of coagulation carried out through thromboelastographic and metric methods, there is a saving in the use of fibrinogen concentrates. In any case, the use of fibrinogen's concentrate has been shown to have a better cost-benefit ratio. The most common dosage used is 25–50 mg/kg. Intraoperative recovery (RIO) is a blood-saving technique used during intraoperative bleeding. This procedure allows one to reduce the risk of allogeneic transfusions [51]. The blood aspirated and anticoagulated goes into a reservoir, and from there, through filters for microaggregates, it passes into a cell separators bowl to be concentrated by centrifugation, washed with physiological solution and then reinfused. The RIO is indicated with a blood loss of at least 1000 mL or in any case when is expected a blood loss ≥20% of the global volemia, in patients with antibodies which may cause difficulties in transfusion from donor, and in patients who refuse donor blood transfusion. In the case of RIO, the reinfusion consists of red blood cells only. Therefore, in the case of recovery and reinfusion of large volumes, it is important to monitor the platelet count and coagulation [52].
