**3.3 The importance of normothermia**

The relationship between the extent of transfusion support and body temperature is now well established [53, 54]. Hypothermia during surgical procedures is produced by the combination of several factors that participate in the loss of body heat: low temperature in the operating room, administration of unheated fluids, alteration of the mechanisms of thermoregulation induced by anesthesia, and perspiratio insensibilis mainly due to mechanical ventilation. A drop, even moderate, in body temperature is able to modify the physiological mechanisms of hemostasis by altering platelet function and inhibiting the temperature-dependent enzymatic reactions of coagulation [55]. It has been demonstrated that even mild hypothermia (reduction of <1°C in body temperature) can increase blood losses by up to 16%, with a relative increase in the possibility of receiving transfusion therapy (22%) [53, 56]. For these reasons, it is fundamental to ensure the monitoring of the temperature in the operating room and the use of measures aimed at the prevention of hypothermia such as administration of heated fluids, dressing, and active heating.

### **3.4 Neuraxial strategies**

Ideally, all neuraxial techniques for total hip replacement are validated. Therefore, the choice of the specific technique remains at the clinician's discretion. Different techniques can be chosen in relation to the patient, the type of surgical access (e.g., anterior versus posterolateral approaches), and the presumed duration of the surgery. Among the neuraxial procedures, the following are included:


The single-shot spinal anesthesia is the most used technique. It allows one to keep the patient awake during the surgery, to reduce intraoperative time, and to minimize the administration of intraoperative analgo-sedative drugs, thus allowing for a more rapid discharge from the operating room and reduction of stay [57, 58]. The puncture site is usually at the L3/L4 level, and the most used anesthetic drugs are levobupicavaine or hyperbaric versus isobaric bupivacaine [59]. It is a clinician's choice whether to perform a selective spinal or a total spinal anesthesia for both lower limbs. In any case, the most used dosages vary from 10 to 15 mg for both molecules. With the addition of adjuvant drugs (i.e., clonidine and/or morphine), the duration of anesthesia can be prolonged [60, 61]. Thin needles (27/25 gauge) with Whitacre tip type are less painful on insertion and reduce the number of local complications, such as headache or spinal hematoma [62]. Epidural catheter placement alone is rarely used in this type of surgery. The motor and sensory block necessary for the surgery phase can be reached with high doses of anesthetics. The needle normally used is the Thuoy needle (16/18G) through which a catheter is left in the epidural space. The catheter in place allows the anesthesia to be extended according to the clinician's decision. Managing total surgery time with epidural anesthesia alone may increase

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

the risk of local anesthetic overload toxicity. Combined spino-epidural anesthesia allows for a rapid onset and, if the surgery is prolonged, to continue anesthesia and postoperative analgesia [63, 64]. For elderly patients with fracture surgery, both the general anesthesia and the combined spinal-epidural anesthesia are able to maintain a good anesthesia effect, but the combined spinal-epidural anesthesia is preferable as it may shorten the onset time and it has less impact on the patient's hemodynamic parameters. In addition, combined spinal-epidural anesthesia is associated with lower incidence of complications [63, 64]. Continuous spinal anesthesia is rarely used in hip surgery. It represents a valid alternative to the combined technique as it guarantees an optimal anesthetic plan by reducing the dosage of local anesthetics. On the other hand, it is a procedure that requires an expert team who is familiar with the method [65]. The use of neuraxial anesthesia in routine hip surgery was associated with lower immediate postoperative pain scores, lower intraoperative, and immediate postoperative opioid requirements and may be associated with shorter anesthesia recovery time, without any major adverse events when compared with general anesthesia [66].
