Often times, we have to deal with HOTN after spinal placed in obstetric patients. Patient may feel nauseated and throw up due to HOTN. Besides co-loading of crystalloid, ondansetron can be given 5-15mins prior to spinal placement to reduce the extend of HOTN. It is a cheap and readily available drug in our anesthesia cart.
why it works:
- 5-HT3 antagonist
- MOA – blocks serotonin at central & peripheral 5-HT3 receptors notably at CTZ and vagal afferents pathway.
- In the presence of decreased blood volume, 5-HT may be an important factor inducing the Bezold-Jarish Reflex via 5-HT3 receptors.
- Ondansetron attenuates the 5-HT3 mediated vagal responses associated with spinal.
Evidence based studies to support the findings:
- Sahoo et al (Int J Obstet Anesth 2010): RCT demonstrated 4mg IV given 5 mins prior to spinal placement significantly reduces the amount of pressors used in elective C-section.
- Owczuk et al (Reg Anesth Pain Med, 2008): RCT demonstrated that ondansetron given IV attenuates arterial blood pressure drop due to spinal anesthesia
Try it out and let me know what you think.