Article Text
Abstract
Neuraxial blockade is frequently chosen by anesthesiologists in conducting anesthesia, especially for caesarian delivery, lower abdominal, inguinal, urogenital, rectal and lower extremity surgery. Despite all of its benefits, there are also some undesirable consequences. Spinal induced hypotension is the most common and is frequently encountered in the obstetric and elderly patients.
The main mechanism producing spinal hypotension is the sympathetic block followed by arterial dilatation with a reduction in systemic vascular resistance; venous pooling in the legs is another contributor to hypotension by decreasing venous return and further reduction in cardiac output.
Over the years clinicians and researchers have struggled to find the proper technique for preventing and managing it. The current available strategies include proper positioning, especially for the parturient, lower extremity wrapping, compression or elevation to minimize venous pooling, fluid preloading and co-loading with either crystalloid or colloid solutions to increase the effective blood volume and pharmacological interventions with agents that produce peripheral vasoconstriction such as phenylephrine, norepinephrine or ephedrine. In the past few years other new methods have emerged such as the use of 5HT3 receptor antagonists or ultrasound evaluations of the vena cava.
All of these methods aim to maintain blood pressure by increasing either vascular resistance or return of blood to the heart, or both, but none of them seem to be perfect. Currently only the vasopressors have proven to be the mainstay for the prophylaxis and treatment of spinal induced hypotension.