INTRODUCTION Spinal anesthesia, or spinal block, is a regional anesthesia technique that, along with epidural anesthesia and caudal block, belongs to the group of neuraxial blocks. Spinal anesthesia is used as an alternative to general anesthesia, usually in surgical procedures on the lower extremities (foot, knees, hips), pelvis and lower abdominal surgeries when it is not necessary to completely put the patient to sleep, i.e. general anesthesia. The peculiarity of the spinal anesthesia technique is the application of local anesthetic in the spinal space, i.e. in the surroundings of the spinal cord filled with cerebrospinal fluid. In this case, the spinal needle passes between the vertebrae through the soft tissues, ligaments and the hard meninges (dura mater). August Bier performed one of the first spinal anesthesias for human surgery in 1898. The development of the precision of the spinal anesthesia technique and the use of certain groups of local anesthetics contributed to a significantly reduced complication (headache, low blood pressure, lower back pain) and transient neurological symptoms (shaking after the procedure, difficulty urinating, allergic reaction, prolonged temporary loss of sensation, injury structure in the area of the spine, etc.).The success of the spinal block depends on the current anatomy of the spine, the type, dose and concentration of the applied local anesthetic, the cooperation of the patient and the skill and experience of the anesthesiologist. With the onset of a spinal block, it is possible to achieve spinal anesthesia (the patient loses all sensation and movement) (spinal anesthesia), or only spinal analgesia (loss of pain sensation only) distal to the segment of the spine on which the local anesthetic was applied. Depending on the type and dose of local anesthetic, spinal anesthesia works for an average of 2-3 hours, after which sensory sensations and motor skills begin to return. The patient for spinal anesthesia undergoes the same anesthesiological preparation as for general anesthesia. During spinal anesthesia, the patient's vital functions are monitored continuously and non-invasively, just as during general anesthesia. In the postoperative course, the patient is also monitored until complete recovery of sensation and motor function. Nursing plays an active and important role in the preparation of the patient before spinal anesthesia (by taking a nursing history, i.e. insight into the patient's current therapy, chronic diseases, previous anesthesia and adverse reactions to local anesthetics, then in sampling the findings and completing the medical documentation for the anesthesia examination, preparing the patient for regional anesthesia and the application of premedication as prescribed by the anesthesiologist), during the actual performance of the spinal block (preparation of sterile materials and local anesthetics and assisting in the performance of spinal anesthesia), in the supervision of spinal anesthesia during surgery and in the immediate postoperative period (non-invasive monitoring of the patient's vital functions, monitoring dynamics of recovery of sensory sensation and motor function). It is necessary to emphasize the importance of obtaining the consent of the patient and the operator for the application of spinal anesthesia. Namely, a potentially restless and uncooperative patient can inadvertently make it difficult or even compromise the performance of a surgical procedure. That is why timely communication between all members of the surgical-anesthesiology team is of particular importance. If the decision for spinal anesthesia is agreed upon, the most optimal technique of spinal anesthesia is applied both for the safe performance of a specific operation (eg spinal block with sedation) and for the overall well-being of the patient (bilateral or unilateral spinal block). In doing so, the anesthesiological assessment of the patient and the final decision of the anesthesiologist are particularly respected. METHODS In this review, a brief history and technique of spinal anesthesia is presented, which is compared with the modern application and performance of classical, bilateral and unilateral spinal block. The advantages of spinal anesthesia were particularly highlighted (less confusion and drowsiness after the procedure, complete relief of pain immediately after the procedure, reduced need for strong analgesics, reduction in the incidence of nausea and the urge to vomit, earlier return to eating and drinking after the procedure, less impact of anesthetics on the heart and lungs, and lower risk of lung infections), disadvantages (uncomfortable position on the operating table, altered sensation in the lower part of the body during operations in the lower abdomen (hernioplasty, caesarean section, etc.), hypotension, bradycardia, skin itching, nausea, paresthesias in the area lower extremities and/or buttocks, severe post-puncture headache in 1 out of 100 cases) as well as risks related to existing diseases of the patient himself (migraine headaches, concomitant chronic diseases, pre-existing nerve injury, neurological diseases, infection in the area of application of the spinal block).The review work is based on an insight into professional and scientific works related to spinal anesthesia available in the PubMed database and the Portal of Croatian scientific and professional journals (Hrčak-srce) over the last five years. CONCLUSIONSpinal anesthesia can be bilateral (block of both lower extremities) or unilateral (block of only one lower extremity). Unilateral spinal anesthesia, in contrast to bilateral, achieves a complete block of sensory, motor and sympathetic function related to only one leg. The doses of local anesthetics and analgesics for unilateral block are smaller and adapted to the needs of anesthesia of only one limb. Consequently, unilateral block maintains greater hemodynamic stability compared to bilateral. Therefore, it is indicated precisely in high-risk patients for operations on the lower extremity, especially if peripheral nerve block techniques cannot provide anesthesia for the intended operative field. Both types of anesthesia provide excellent anesthesia. It is characteristic of a bilateral block that it fully occurs within 3-5 minutes, while a unilateral block requires a full 15 minutes, during which the patient must lie on his side. Recovery from a unilateral block, including sensory, motor and autonomic, is much faster and more pleasant, the incidence of accompanying unwanted side effects is lower, which are less likely with a unilateral block