Carotid Ultrasound for Post-Spinal Anesthesia Hypotension in Elderly Hip Surgery

Hip osteoarthritis (OA) is one of the most common types of arthritis. Common symptoms of hip OA include joint pain, swelling, stiffness, and limited mobility. Early intervention can help slow the progression of the disease and improve the quality of life for patients. Total hip arthroplasty (THA) is among the five most commonly performed surgical procedures worldwide. It is a functional prosthetic intervention involving the replacement of a damaged joint.

This surgery can be performed under either general anesthesia (GA) or regional anesthesia (most commonly spinal anesthesia). Key factors influencing morbidity and mortality include preoperative assessment, anesthetic technique selection, intraoperative management, and postoperative care. Hypotension is the most common side effect associated with spinal anesthesia. The likely mechanism involves spinal nerve sympathectomy, which leads to peripheral arterial vasodilation, reduced venous return, and, consequently, a decrease in cardiac output.

The main cause of spinal anesthesia-induced hypotension (SAH) is sympathetic blockade, which results in vasodilation with relative hypovolemia and reduced cardiac output. Many elderly patients arrive at the operating room in a relatively hypovolemic state due to preoperative fasting, reduced thirst mechanisms, and diminished renal capacity to conserve water and salt.

Traditional approaches to post spinal anesthesia hypotension (PSAH) prevention have demonstrated limitations. Fluid boluses fail to adequately increase cardiac volume in approximately 50% of hemodynamically unstable patients, and in fluid non-responsive individuals, such empirical loading may even exacerbate the patient's condition. The absence of a definitive tool to reliably predict PSAH makes it challenging to differentiate patients who would benefit from vasopressors versus those who would respond to fluid boluses.

The ongoing quest for simple, reliable, and non-invasive methods to predict PSAH has led to the exploration of various ultrasonographic parameters. While techniques like transthoracic bioimpedance and transthoracic echocardiography (TTE) offer insights into hemodynamic status, TTE demands high operator proficiency and is time-consuming, and bioimpedance devices are often expensive and not readily available. In contrast, ultrasonographic assessment of the inferior vena cava collapsibility index (IVCCI) and corrected carotid flow time (CFTc) have emerged as potentially time efficient, easy-to-perform, and widely available indicators of fluid responsiveness, capable of identifying changes in cardiac output.

The IVC diameter provides an indirect assessment of intravascular volume. Preoperative IVCCI has been proposed as a dependable indicator for predicting the likelihood of hypotension within 30 minutes following spinal anesthesia. Similarly, CFTc, which represents the carotid systole time corrected for heart rate, is a simple measurement that may correlate with intravascular volume, with fluid administration increasing CFTc and volume depletion decreasing it.

However, direct comparative studies evaluating the efficacy of both CFTc and IVCCI in predicting PSAH, particularly in the geriatric population, have been scarce. Therefore, this study is designed to evaluate the predictive value of preoperative CFTc for hypotension after spinal anesthesia in patients undergoing geriatric hip surgery.