I recently sent an article to a certain journal comparing Posterior Spinal Anesthesia obtained with 5 mg of 0.1% hypobaric bupivacaine for orifice surgery in the Jack-knife position with 5 mg 0.5% hyperbaric bupivacaine for the same type of surgery operated on lithotomy position. In the evaluation of the article, the Reviewer questioned why I perform spinal anesthesia in the surgery position (Jack-Knife position) because it is difficult and suggested performing it in the lithotomy position and then placing it in the prone position. I challenged his arguments by stating that this way the patient would not have sensitive spinal anesthesia because it would block the motor roots as well. I perform spinal anesthesia with puncture in the lateral decubitus position, seated, prone and many years ago when the surgical tables for femur surgery there was a space, I also perform the puncture with the patient in the supine position through this space. In this way I can conclude, since I teach spinal anesthesia in all possible positions that “what is difficult is what you do not know how to do”.

In 2017, I wrote an article trying to explain all the possibilities for a complete understanding of spinal anesthesia [1]. The administrations of a safe and efficacious anesthesia demands not only observation, but also knowledge of the anterior and posterior roots and the dermatomes needed to block enough for the surgical procedure. As well as using the different solutions in the arsenal for spinal anesthesia such as: hypobaric, isobaric and hyperbaric of the different types of local anesthetics. Most anesthesiologists prefer to use hyperbaric solutions, being completely unaware of hypobaric solutions, which allow hemi spinal anesthesia (Unilateral and Dorsal Anesthesia). Values of CSF determined in modern equipment vary from 1.00103 to 1.00013 among healthy adults of both genders [2]. This way, local anesthetic solutions of density greater than 1.00103 are called hyperbaric solutions. Densities under 1.00013 are called hypobaric solutions. All solutions with densities between 1.00103 and 1.00013 are called isobaric solutions, even when they have a different behavior in the CSF of the patient.

Using a densimeter (DMA 450), all densities of the different solutions of local anesthetics and adjuvants were evaluated [3]. This experimental study showed that all hyperbaric or hypobaric local anesthetics are changed by the addition of adjuvants; however, they remain hyperbaric or hypobaric. The results demonstrated that some solutions commonly called isobaric are, in reality hypobaric. Most anesthesiologists mix local anesthetics with adjuvants in the same syringe, thus completely changing the baricity of the various solutions. I only use adjuvants in insulin syringes first and then the chosen anesthetic.

Most anesthesiologists think that spinal anesthesia is a spinal puncture and injection of 15 mg hyperbaric bupivacaine, forgetting the understanding of spinal anesthesia [4]. When decreasing the concentration of bupivacaine 0.15% hypobaric to 0.1% hypobaric, there was a significant decrease in baricity resulting in a unilateral sensitive spinal anesthesia, without motor block or proprioception, remaining with the tendon movements for the proposed surgery [5]. This was only possible due to a complete understanding of spinal anesthesia.

Studying the thoracic spine with magnetic resonance imaging showed that there is a large space in T2, T5 and T10, protecting the spinal cord from injury during thoracic spinal anesthesia [6]. This was confirmed in 636 patients undergoing low-dose thoracic spinal anesthesia, reducing latency time, motor block and cardiocirculatory changes, without neurological sequelae [7]. Studying 369 cases of spinal anesthesia used for laparoscopic cholecystectomy procedures comparing lumbar puncture with thoracic technique, showed that thoracic spinal anesthesia is preferable for using lower doses, with less risks of hemodynamic and respiratory effects [8]. Recently a group from Italy is performing continuous thoracic spinal anesthesia in major abdominal surgery [9].

The spinal anesthesia is old, simple, easy and a popular technique. However, for your complete understanding, you must know the anatomy, physiology, pharmacology and the various puncture positions and the three solutions used: hyperbaric, isobaric and hypobaric. Spinal anesthesia is much more than a simple injection of local anesthetic into the cerebrospinal fluid. With complete knowledge of the solutions, the types of anesthesia (simple, unilateral, posterior, thoracic spinal anesthesia) you can choose the best spinal anesthesia technique for your patient, taking into consideration the surgery you will be doing and the estimated time of the necessary block.

In conclusion, the vast majority of anesthesiologists do not understand why hyperbaric solutions when injected and kept in the supine position provide a much longer sensory block than isobaric solutions, which provide a more prolonged motor block than the sensory one [10]. Just understand the sensory and motor roots.