Table 1. Findings of studies included in the review.

ICU: intensive care unit; CSF: cerebrospinal fluid; PDPH: post-dural puncture headache

Authors	Year	Summary
Rasmussen and Moller [9]	2000	Postoperative psychosis occurs in 10-37% of older patients after surgery, with varying frequencies based on research and types of operations, ranging from 0% to 73%. Repairing a broken hip is associated with a frequency of 16-62%.
Dyer et al. [10]	1995	Administering spinal anesthesia to older patients requires careful consideration of various factors to ensure safety and efficacy. Older patients often have specific health conditions and physiological changes that necessitate a tailored approach.
Bitsch et al. [11]	2006	Postoperative psychosis was investigated in relation to various clinical and preoperative factors. The level of intraoperative sedation was identified as a modifiable risk factor for postoperative psychosis.
Zakriya et al. [12]	2004	Hospitalization in the ICU and perioperative erythrocyte transfusion were found to be connected to the occurrence of postoperative psychosis.
Marcantonio et al. [13]	2000	Recovery after hip fracture surgery can be influenced by various factors, including the choice and administration of anesthesia. While spinal anesthesia is a common and effective option for hip fracture surgery, certain factors related to its administration can affect the postoperative functional outcome and recovery in patients.
Morrison et al. [15]	2003	Intraoperative levels of sedation can indeed influence the development of postoperative delirium, a condition characterized by acute confusion, altered mental status, and cognitive changes following surgery. The relationship between intraoperative sedation and postoperative delirium is complex and multifactorial, involving various aspects of the surgical and anesthesia process.
Vercauteren and Heytens [16]	2007	Anesthetists are concerned about the impact of anesthesia on patients with pre-existing neurological and muscle disorders. Despite limited research, many prefer general anesthesia due to legal concerns, but regional anesthesia offers clear benefits and should be considered.
Kanri et al. [17]	1990	Patients with spinal abnormalities like scoliosis pose challenges for administering sedation and anesthesia due to altered anatomy affecting needle positioning and anesthetic spread. Special considerations are needed, particularly regarding respiratory and airway control, making regional anesthesia problematic in such cases.
Ummenhofer et al. [18]	1998	The arachnoid mater acts as a reservoir for CSF and plays an active role in processing and transporting chemicals across the meninges. Recent studies indicate that it expresses metabolic enzymes influencing key chemicals like adrenaline and neurotransmitters important for spinal anesthesia, such as acetylcholine.
Carpenter et al. [19]	1998	Obese individuals have about 10 mL less CSF due to neural foramina constriction. Lumbosacral CSF capacity is clinically linked to spinal anesthesia effectiveness, comprising 80% of the peak block height and decline in sensory and motor blocks for hyperbaric lidocaine and isobaric bupivacaine.
Liu and McDonald [34]	2001	Patients on anticoagulants or with bleeding disorders face higher bleeding risks during or after surgery, emphasizing the need to assess their coagulation status before spinal anesthesia. Anticoagulants are used in surgery to manage thrombotic disorders. Analysis of neurologic injury claims highlights anticoagulation as a significant risk factor for spinal cord damage associated with spinal anesthesia.
Wedel and Horlocker [35]	2006	Infections from bacteria in the central neuraxis can lead to meningitis or spinal cord pressure due to abscess formation. The infection source may be from within the patient (endogenous) or external (exogenous) through contaminated equipment or drugs. Breaks in aseptic technique can transmit microorganisms. Indwelling catheters may facilitate infection spread from skin to the epidural or intrathecal space by becoming colonized.
Jeon et al. [36]	2010	Heart rate changes between left lateral and supine positions predict perioperative decline in obstetric patients during cesarean delivery under spinal anesthesia.
Zorko et al. [24]	2009	In a non-obstetric study, maintaining cardiac output with lactated Ringer's or 6% hydroxyethyl starch solution is equally effective as the Trendelenburg position for 10 minutes after a spinal block. Co-hydration is more efficient than pre-hydration, and colloid loading better maintains cardiac output and blood pressure.
Prakash et al. [37]	2013	Examining the use of lateral decubitus position to mitigate low blood pressure effects, it was found to have a delayed onset of low heart rate episodes, but the incidence of low blood pressure or medication use was comparable to patients in the supine position.
Bezov et al. [28]	2010	PDPH is a common complication of spinal anesthesia, often associated with large-bore needles or inadequately sealed puncture sites. Proper needle choice and technique can decrease the likelihood of PDPH. Modifiable risk factors for PDPH include needle size, shape, bevel orientation, insertion angle, style replacement, and operator experience.
Bezov et al. [27]	2010	Needle size is a key factor influencing the development of PDPH.
Flaatten et al. [31]	1989	Using smaller needle diameters, like 29G needles, decreases the occurrence of PDPH, but they may be too thin for practical use.
Xu et al. [38]	2017	Needle size is a key factor in PDPH development.
Tsen and Hepner [4]	2006	Commonly used spinal needle sizes range from 22G to 27G, although sizes ranging from 19G to 30G are available.
Turnbull and Shepherd [30]	2003	PDPH incidence after spinal anesthesia: 36% with 22G, 25% with 25G, 2-12% with 26G, and <2% with <26G needles.
Lynch et al. [29]	1994	PDPH occurrence varies with needle gauge in spinal anesthesia. Lower needle gauges are associated with higher PDPH incidence.
Tsantes et al. [21]	2020	PDPH occurrence is similar for pencil-point and cutting-point needles.
Naulty et al. [39]	1990	Multiple failed punctures with Quincke needle or another type of spinal needle may increase PDPH risk.
Zhang et al. [40]	2016	Repeated dural punctures with a spinal needle heighten the likelihood of PDPH.
Luostarinen et al. [41]	2005	Sometimes, CSF is too dense to pass through a small needle.
Imarengiaye and Edomwonyi [42]	2002	Cutting-point needles make it easier to pierce skin and ligaments, aiding dura mater identification.
Kokki et al. [43]	1998	Pencil-point needles may pose challenges in skin and ligament penetration, affecting dura mater identification.
Kokki et al. [44]	2000	PDPH occurrence is similar for pencil- and cutting-point needles.
Flaatten al. [45]	2000	Pencil-point needles significantly reduce PDPH incidence compared to Quincke (cutting-point) needles.
Schmittner et al. [47]	2011	According to some studies, noncutting needles may reduce headache rates associated with procedures like spinal anesthesia.
Cherng et al. [46]	2008	Rare but possible risk of nerve injury with spinal anesthesia, especially if needle trauma occurs. Perioperative nerve damage is a known side effect, but severe or permanent neurologic consequences are uncommon. Improper patient placement can lead to peripheral nerve damage. Anesthetists should be vigilant for nerve injuries during anesthesia administration.
GR et al. [49]	1961	Two types of neurologic issues with spinal anesthesia: those unrelated but concurrent and those directly caused by it. Precise prevalence, cause, and prognosis reporting is challenging due to difficulties distinguishing injuries caused by positioning, casts, or surgical trauma from those attributed to the anesthesia.
Phillips et al. [50]	1969	Neurologic issues linked to spinal anesthesia can stem from trauma, ischemia, infection, or neurotoxicity. However, neurologic damage from a needle or catheter is exceptionally rare.
Calthorpe [8]	2004	The evolution of spinal needles, specifically their tip design, commenced with insights into the anatomy and physiology of the central nervous system prevalent during the introduction of spinal anesthesia.
Hofhuizen et al. [22]	2019	Hypotension frequently occurs with spinal anesthesia and results from a reduction in systemic vascular resistance and cardiac output.