Spinal anesthesia is one of the most commonly used regional anesthetic techniques for lower limb surgeries because it provides effective sensory and motor blockade, satisfactory intraoperative analgesia, rapid onset, and avoidance of airway instrumentation. It is frequently used for orthopedic and other lower extremity procedures, particularly in patients for whom regional anesthesia may provide advantages over general anesthesia. Despite these benefits, spinal anesthesia is associated with important cardiovascular changes, of which intraoperative hypotension is one of the most frequent complications. Intraoperative hypotension following spinal anesthesia primarily results from sympathetic blockade, which causes arterial and venous vasodilation, reduction in systemic vascular resistance, venous pooling, and decreased venous return to the heart. The resulting reduction in cardiac output and arterial blood pressure can range from mild, transient hypotension to severe cardiovascular compromise. The incidence and severity of hypotension are influenced by several factors, including age, baseline blood pressure, level of sensory block, dose and type of local anesthetic, patient position, intravascular volume status, and associated comorbidities.

The reported frequency of hypotension following spinal anesthesia varies considerably between studies because different definitions and blood-pressure thresholds have been used. Carpenter et al. demonstrated that hypotension is a significant adverse effect of spinal anesthesia and identified several patient- and procedure-related risk factors. Their findings highlighted the importance of recognizing patients who may be particularly susceptible to hemodynamic disturbances during spinal anesthesia.³

Similarly, Hartmann et al. investigated hypotension following induction of spinal anesthesia using automated data collection and demonstrated that clinically important hypotension occurs relatively frequently. Their study emphasized the contribution of patient characteristics and anesthetic factors to the development of hypotension and supported careful perioperative blood-pressure monitoring.⁴

The problem may be particularly important among elderly patients undergoing lower limb surgery. Meyhoff et al. investigated whether hypotension occurring during the onset of spinal anesthesia could be predicted in elderly patients and demonstrated that patient characteristics and changes occurring soon after spinal anesthesia may provide useful information regarding the development of hypotension.⁵ This is clinically relevant because lower limb surgery frequently involves elderly patients, particularly those undergoing orthopedic procedures.

The consequences of spinal anesthesia-induced hypotension can be clinically significant. A substantial reduction in arterial blood pressure may compromise perfusion of vital organs and, particularly in patients with limited cardiovascular reserve, may increase the risk of myocardial, cerebral, or renal hypoperfusion. Therefore, early recognition and appropriate management of hypotension are important components of safe spinal anesthesia. Preventive and therapeutic strategies include appropriate fluid administration, modification of anesthetic dose, patient positioning, and the use of vasopressor agents when indicated.¹,⁶

Several studies have evaluated methods for preventing and treating hypotension associated with spinal anesthesia. Lee et al. reviewed the mechanisms, incidence, prevention, and management of spinal-induced hypotension and emphasized that hypotension is principally related to sympathetic blockade and that its management should be individualized according to patient and surgical characteristics.¹ Pharmacological management may include vasopressors such as ephedrine and phenylephrine, although their use and relative effectiveness depend on the clinical setting.⁶

Tarkkila and Isola developed a regression model to identify patients at increased risk of hypotension, bradycardia, and nausea during spinal anesthesia.² Their work demonstrates the importance of identifying risk factors before and during spinal anesthesia so that appropriate preventive measures can be instituted.

The definition of intraoperative hypotension is also important when determining its frequency. Klöhr et al. demonstrated substantial variation in the definitions of hypotension used in the literature, particularly with respect to absolute systolic blood-pressure values and percentage reductions from baseline.⁷ Consequently, clearly defining hypotension in a clinical study is essential to allow meaningful interpretation and comparison with previous research.

Hemodynamic disturbances are also relevant specifically to orthopedic and lower limb procedures. Lower-limb surgery may require different levels and durations of spinal blockade depending on the type and duration of surgery. Bajwa and Kulshrestha discussed the anesthetic and perioperative hemodynamic considerations associated with orthopedic procedures, emphasizing the importance of cardiovascular monitoring during regional anesthesia.⁸

Evidence from studies of major lower-limb orthopedic surgery also suggests that the dose and technique of spinal anesthesia influence the risk of hypotension. Recent evidence in elderly patients undergoing hip fracture surgery indicates that lower-dose spinal anesthesia may reduce the incidence of hypotension while maintaining satisfactory surgical anesthesia.¹⁰ Furthermore, comparisons of unilateral and bilateral spinal anesthesia for lower-extremity surgery suggest that unilateral spinal anesthesia may be associated with fewer hemodynamic changes, including hypotension, compared with conventional bilateral spinal anesthesia.¹⁰

Although international literature has extensively examined hypotension associated with spinal anesthesia, local data from Pakistan and particularly Azad Jammu and Kashmir remain limited. The frequency of intraoperative hypotension may differ according to patient characteristics, surgical practices, anesthetic techniques, spinal anesthetic doses, perioperative fluid management, and institutional protocols. Therefore, determining the local frequency of this complication is important for improving anesthetic practice and patient safety.

The present study is therefore designed to determine the frequency of intraoperative hypotension during spinal anesthesia in patients undergoing lower limb surgeries at a tertiary care hospital in Azad Kashmir. The findings may provide useful local evidence regarding the magnitude of this common anesthetic complication and may help anesthesiologists identify patients at increased risk, improve intraoperative monitoring, and develop appropriate preventive and management strategies

A descriptive cross-sectional study was conducted on 200 patients undergoing lower limb surgeries under spinal anesthesia at a tertiary care hospital in Azad Kashmir. Patients aged ≥18 years who received spinal anesthesia were included, while patients with pre-existing hypotension, major cardiovascular instability, or contraindications to spinal anesthesia were excluded. Baseline blood pressure and heart rate were recorded before spinal anesthesia. Blood pressure was monitored regularly throughout the surgery. Intraoperative hypotension was defined as a fall in systolic blood pressure ≥20% from baseline and/or systolic blood pressure <90 mmHg. Data regarding age, sex, ASA status, type of surgery, baseline blood pressure, and occurrence of hypotension were recorded. Data were analyzed using SPSS version 21.0 and presented as frequencies, percentages, means, and standard deviations. A p-value <0.05 was considered statistically significant. Ethical approval and informed consent were obtained before the study.

A total of 200 patients undergoing lower limb surgeries under spinal anesthesia were included in the study. The mean age of the patients was 42.6 ± 15.3 years, with an age range of 18–75 years. There were 128 (64%) males and 72 (36%) females.

In terms of ASA physical status, 126 (63%) patients were ASA I, while 68 (34%) were ASA II and 6 (3%) were ASA III. The most commonly performed procedures were orthopedic lower-limb surgeries, including fracture fixation, open reduction and internal fixation, and other elective lower-limb procedures.

Intraoperative hypotension developed in 72 (36%) patients, whereas 128 (64%) patients did not develop hypotension. Among patients who developed hypotension, most episodes occurred within the first 20–30 minutes following administration of spinal anesthesia. The mean baseline systolic blood pressure was 126.8 ± 12.4 mmHg, which decreased to a mean lowest systolic blood pressure of 96.4 ± 10.8 mmHg among patients who developed hypotension.

Hypotension was more frequently observed among patients aged ≥50 years compared with younger patients. It was also more common among patients with higher ASA physical status. Most patients who developed hypotension responded adequately to intravenous fluid administration, while some required vasopressor therapy according to the anesthesiologist's judgment.

Overall, the study demonstrated that intraoperative hypotension was a relatively common complication of spinal anesthesia, occurring in approximately one-third (36%) of patients undergoing lower limb surgery.

Table 1. Demographic characteristics of study participants (n=200)

Table 2. Frequency of intraoperative hypotension

In the present study, 200 patients undergoing lower limb surgeries under spinal anesthesia were evaluated, and intraoperative hypotension occurred in 72 patients (36%). Thus, approximately one-third of the patients developed hypotension following spinal anesthesia. This finding demonstrates that intraoperative hypotension remains a common hemodynamic complication of spinal anesthesia in patients undergoing lower limb surgery. The frequency of hypotension in the present study was almost identical to that reported by Kyokong et al., who prospectively evaluated 1,220 patients receiving spinal anesthesia and reported an incidence of hypotension of 36.8%. They also found that increasing age and a higher sensory block level were important risk factors for hypotension.¹¹ This close similarity supports the finding of the present study and indicates that spinal anesthesia-induced hypotension may occur frequently despite differences in patient populations and clinical settings. Similarly, Carpenter et al. reported hypotension in 33% of 952 patients receiving spinal anesthesia. Their study identified higher sensory block level, age ≥40 years, and lower baseline systolic blood pressure as important factors associated with hypotension.¹⁵ The incidence of 36% observed in our study is therefore slightly higher but broadly comparable with their findings. The difference between studies may partly be explained by differences in the definition of hypotension. In the present study, hypotension was defined as a fall in systolic blood pressure of ≥20% from baseline and/or an absolute systolic blood pressure below 90 mmHg. In contrast, different studies have used different thresholds and combinations of absolute and relative reductions in blood pressure. Such methodological differences can substantially influence the reported incidence of spinal anesthesia-induced hypotension. Hartmann et al. reported a lower incidence of clinically relevant hypotension, approximately 5.4%, among 3,315 patients receiving spinal anesthesia. However, their definition required a greater than 30% reduction in mean arterial pressure together with therapeutic intervention.¹³ Their lower reported incidence compared with our 36% may therefore be explained primarily by the stricter definition of clinically relevant hypotension. Hartmann et al. also identified age, BMI, ASA status, sensory block height, and urgency of surgery among variables associated with hypotension. In the present study, hypotension was observed more frequently among older patients. This finding is consistent with previous evidence. Kyokong et al. demonstrated increasing age as an independent risk factor for hypotension following spinal anesthesia.¹¹ Carpenter et al. similarly found that patients aged ≥40 years had increased odds of developing hypotension.¹⁵ These findings may be explained by age-related reductions in cardiovascular compensatory mechanisms and impaired ability to maintain venous return following sympathetic blockade. The association between age and hypotension is particularly relevant in lower limb orthopedic surgery because elderly patients frequently undergo procedures such as hip fracture repair and other major lower extremity operations. A meta-analysis of elderly patients undergoing hip fracture surgery found that the dose of spinal anesthetic influenced the risk of hypotension, with lower-dose spinal anesthesia being associated with substantially fewer hypotensive events.¹⁷ The present study also demonstrated that hypotension occurred in patients with different ASA physical statuses, with a greater tendency among patients with higher ASA status. This observation is consistent with previous research identifying ASA status and pre-existing cardiovascular conditions as potential contributors to hemodynamic instability following spinal anesthesia. Hartmann et al. found ASA physical status among variables associated with hypotension.¹³ The level of sensory blockade is another important determinant of hypotension. Carpenter et al. reported significantly increased odds of hypotension when the peak block height was ≥T5, while Kyokong et al. similarly identified a high sensory block level as an important risk factor.¹¹,¹⁵ Excessive sympathetic blockade can produce greater peripheral vasodilation and venous pooling, resulting in reduced venous return and consequently reduced arterial blood pressure. The findings are also consistent with research specifically involving lower limb surgery. A randomized study comparing unilateral and conventional spinal anesthesia in patients undergoing unilateral lower limb surgery reported hypotension in 8.1% and 13.5% of patients, respectively. Although these rates were lower than the 36% observed in our study, the conventional group demonstrated greater falls in systolic blood pressure from baseline.⁹ Differences in patient selection, anesthetic technique, dose, and definition of hypotension may explain the lower incidence in that study. More recent evidence also emphasizes the influence of spinal anesthetic technique on hemodynamic stability. A systematic review and meta-analysis involving 1,358 patients undergoing lower extremity or lower abdominal surgery found that unilateral spinal anesthesia significantly reduced the risk of hypotension compared with bilateral spinal anesthesia.¹⁹ Similarly, a randomized study in elderly patients undergoing lower limb orthopedic surgery reported hypotension rates of 16% versus 44% depending on the bupivacaine technique used.¹⁸ This suggests that anesthetic dose, baricity, distribution of the block, and technique can substantially affect intraoperative blood pressure. The occurrence of hypotension following spinal anesthesia is clinically important because significant reductions in arterial pressure may compromise tissue perfusion, particularly in elderly patients and those with cardiovascular comorbidities. Consequently, careful preoperative assessment, appropriate patient selection, adequate monitoring, optimization of intravascular volume, and early treatment of hypotension are important components of safe spinal anesthesia.¹,¹⁶ Overall, the 36% frequency of intraoperative hypotension observed in the present study is comparable with several published studies, particularly the 36.8% incidence reported by Kyokong et al.¹¹ and the 33% incidence reported by Carpenter et al.¹⁵ However, considerable variation exists among studies because of differences in patient characteristics, surgical procedures, spinal anesthetic doses, block levels, fluid management, and definitions of hypotension. These findings highlight the importance of establishing local data for patients undergoing lower limb surgery under spinal anesthesia in tertiary-care hospitals in Azad Kashmir.

The present study concludes that intraoperative hypotension is a common hemodynamic complication of spinal anesthesia in patients undergoing lower limb surgeries, occurring in 36% (72/200) of the studied patients. The occurrence of hypotension was more frequent among older patients and those with higher ASA physical status. These findings emphasize the importance of careful preoperative assessment, adequate preparation, continuous intraoperative blood-pressure monitoring, and prompt recognition and management of hypotension. Appropriate anesthetic planning and timely intervention may help maintain hemodynamic stability and improve patient safety during lower limb surgeries under spinal anesthesia