Recent years have witnessed increasing interest in postoperative pain management. The aim of postoperative pain management is to provide subjective comfort in addition to inhibiting trauma-induced nociceptive impulses to blunt autonomic and somatic reflex responses to pain.

Brachial plexus block remains the only practical alternative to general anesthesia for significant surgery on the upper limb. It provides a superior quality of analgesia and avoids the common side-effects associated with general anesthesia such as postoperative nausea and vomiting. The brachial plexus supraclavicular block is extremely useful in patients with significant co-morbidities such as severe respiratory and cardiovascular disease, morbid obesity and in those with potential airway difficulties. These blocks are therefore particularly useful in the ambulatory surgical setting for a wide variety of patients and procedures [1].

Many modifications were done over the years, but the ultrasound guided technique has become a standard because of its simplicity and reproducible success. Ultrasound (USG) guided supraclavicular block is considered to be one of the most effective anesthetic procedures for upper extremity surgeries. The use of ultrasound has several benefits including block under direct visualization, faster onset and reduction in the dose of local anesthetic [2]. USG guidance also improves accuracy of needle placement, visualization of local anesthetic spread in real time, compensation for anatomical variation and avoidance of intraneural or intravascular injection.

Various local anesthetic agents like bupivacaine, levobupivacaine, ropivacaine and lignocaine have been used with safety and efficacy in performing such blocks [3]. Local anesthetic preferentially binds to the inactivated state of voltage gated sodium channels, but has also been found to bind potassium channels, G-protein coupled receptors, N-methyl-D-aspartate (NMDA) receptors, and calcium channels in vitro [4]. Concentration of local anesthetic which has been used for a blockade of different local anesthetics varies from 0.5%, 0.25% and 0.375%. It has been observed that it is not the concentration but volume that affects the effective dose of local anesthetic [5]. Out of various agents    which  are    used    for    brachial   plexus    block, levobupivacaine is the agentwhich not only prolongs motor and sensory blockade but is also less cardiotoxic and neurotoxic.

Local anesthetics alone for supraclavicular brachial plexus block provide good operative conditions but have shorter duration of postoperative analgesia. This problem can be overcome by using long-acting local anesthetics like bupivacaine or by using adjuvant in regional anesthesia. Adjuvant added to brachial plexus block should prolong the analgesia, without having systemic side effects, prolong motor block and should also reduce the total dose of local anesthetic. Various studies [6-7] have investigated several adjuvants including opioids, clonidine, neostigmine added to local anesthetic in brachial plexus block to achieve quick, dense and prolonged block. However, the results are either inconclusive or associated with side effects.

Dexamethasone, a high-potency long-acting glucocorticoid has been shown to prolong peripheral nerve blockade and duration of analgesia as perineural adjuvant to bupivacaine [8]. The proposed mechanism of action may stem from decreased nociceptive C-fiber activity via a direct effect on glucocorticoid receptors and inhibitory potassium channels. Other suggested mechanisms include a local vasoconstrictive effect, resulting in reduced local anesthetic absorption or a systemic anti-inflammatory effect following vascular uptake of the drug [9].

Dexamethasone has been used in different doses ranging between 1 to 8 mg [10]. But it has been found that 1, 2 and 4 mg dexamethasone when added to 0.25% bupivacaine resulted in similar prolongation of motor blockade and analgesia [11]. Spinal anesthesia has enjoyed a long history of success and has been in use for mankind for more than a century now [12]. Spinal anesthesia involves the use of small amounts of local anesthetic injected into the subarachnoid space to produce a reversible loss of sensation and motor function. The easy and long history of spinal anesthesia may give the impression that it is a simple technique but this is not true.

The injection of local anesthetic in the subarachnoid space can result in hemodynamic and respiratory changes. If it was possible to limit anesthesia for the surgical field, certain undesirable effects of spinal anesthesia could be avoided. Spinal anesthesia is often used for orthopedic surgery especially in lower limb surgeries [13]. However, because of the high prevalence of hypotension and bradycardia risk is always there especially in elderly age group because of their compromised hemodynamic status [14-16].

Localized spinal analgesia in surgery was described as early as 1909 by Jonnesco [17]. Since that time various techniques have evolved, each attempting to confine the extent of somatic and sympathetic paralysis to the site of operation [18]. Among such techniques are segmental spinals, in which localization is affected by placing catheters to predetermined levels in the subarachnoid space and “unilateral” spinals in which limitation of spread is accomplished by using hyperbaric or hypobaric solutions.

The term unilateral spinal anesthesia is used when block is of operative side only with absence of block on non-operative side [19]. When surgery involves only one lower limb, such block is advantageous as it minimizes cardiovascular effects, avoids motor block of non-operative limb and facilitates early discharge [20-21]. Although unilateral spinal is often practiced, but the potential to control the speed of drug, there by restricting the distribution of spinal block to the operative side, remains controversial and frequently debated [22-23]. Low dose local anesthetic solutions by using a pencil-point needle and slow intrathecal injection have been reported to obtain satisfactory unilateral spinal anesthesia (USpA) [24]. USpA techniques allow the administration of small doses of local anesthetic and thus provide a more controllable sensory and sympathetic level of anesthesia. Finally, USpA has more stable cardiovascular parameters compared with conventional bilateral spinal block [25].

USpA aims to limit the distribution of spinal block to the operated side, because most of the operative procedures involve only one lower limb [26]. Compared with the conventional technique, it requires a bit longer preparation time to get the drug fixed to the side to be operated in preference to non-operating limb. It produces fewer hemodynamic side-effects and has higher cardiovascular stability, increased autonomy after surgery and better patient acceptance [27]. It also reduces the incidence of clinically relevant hypotension following spinal anesthesia. Hypotension is the most frequent side effect of spinal anesthesia, occurring in more than 30% of patients

Spinal anesthesia typically cause decrease in arterial blood pressure with only minor decrease in heart rate, stroke volume, or cardiac output even with poor left ventricular function. In conventional spinal anesthesia, it is not possible to limit the accompanied sympathetic block that normally exceeds the sensory block by 2-6 segments [28]. Hypotension occurs from decrease in systemic vascular resistance from sympathetic block with vasodilation and redistribution of central blood volume to lower extremities and splanchnic beds. Various prophylactic and rescue regimens have been advocated for hemodynamic disturbances with emphasis on prevention of hypotension.

A potential way for prophylaxis of hypotension is by manipulation of spinal anesthesia to achieve a predominantly unilateral block [29]. The unilateral spinal anesthesia has been claimed by many as an alternative technique, to restrict the undesired sympathetic block [30].  Unilaterality can be maintained if patient remains in a lateral position for surgery; however, eventual turning of the patient into a supine position result in partial redistribution to bilateral anesthesia. Thus, patient’s position during and immediately after spinal anesthesia influences the spinal distribution of drug i.e. patient position is fundamental basis for unilateral block [31]. It also results in rapid recovery and greater satisfaction among outpatients, in addition to preventing unnecessary nerve block in the contralateral limb

One of the major issues in orthopedic surgery is requirement of lateral position for many surgeries like total hip replacement, bipolar hip arthroplasty etc. Lateral position can lead to uneven distribution of spinal anesthesia in both lower limbs.

While clinicians describing this unilateral technique allude to an associated decrease in anesthetic morbidity, not many controlled clinical studies have been reported comparing this technique to conventional bilateral spinals. In some studies, reported earlier the true “unilaterality” of the sympathetic blockade was termed dubious. Some clinicians have expressed doubt that such unilateral sympathetic paralysis can be obtained, and they feel, therefore, that the rationale behind the unilateral spinal is fallacious.

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