Continuous Spinal Anesthesia - Indications, Uses, and Complications

Introduction:

Continuous spinal anesthesia (CSA) is an anesthetic technique that provides several clinical benefits for obstetric anesthesia and analgesia. With intrathecal (IT) catheters, the level of the sensory blockade can be adjusted to the required dermatomal level with high precision, enabling complete control of the hemodynamic consequences of sympathetic blockade associated with spinal anesthesia compared to epidural or single-shot spinal techniques. Effective management of maternal hemodynamics may benefit patients with cardiovascular disease who benefit from lower doses of local anesthetics. Furthermore, aspiration of cerebrospinal fluid (CSF) provides a visual endpoint for positioning the catheter and enables immediate confirmation of catheter placement. An intrathecal catheter, like an epidural catheter, can be re-injected during relatively long surgical procedures. Moreover, compared to epidural techniques, only a portion of the local anesthetic dose is needed for adequate analgesia and anesthesia. It also has a faster onset and provides a denser sensory block than epidural anesthesia.

What Are the Clinical Indications for CSA?

• Maternal Heart Disease: Titration of slow sensory level with minor incremental boluses enables patient and operator alteration to sympathetic blockade.

• Morbid Obesity: Catheter failures may be reduced when compared to epidural placement. The post-dural puncture headache (PDPH) rate is likely to be reduced slightly compared to non-obese parturients.

• History of Spinal Surgery: The high failure rate of epidural blocks (up to 40 percent) makes CSA a desirable alternative.

• Inadvertent Puncture of Dural Space: Prevents additional dural puncture during difficult epidural placement. Continuous intrathecal catheters can help reduce the post-dural puncture headache rate.

What Is the Clinical Use of CSA for Labour Analgesia?

• Bolus doses of ten percent epidural dosing and continuous epidural infusion have been suggested, but many researchers have discovered that higher doses are needed.

• A two millimeters per hour infusion of a generally used local anesthetic and Fentanyl mixture (0.1 percent Ropivacaine + Fentanyl two gram per milliliter or 0.0625 percentage Bupivacaine + Fentanyl two grams per ml) is a recommended starting dose for epidural infusion.

• Because standard epidural catheters have a dead space of about 1 ml, the starting dose will require a priming volume equal to the catheter volume.

• The provider can treat breakthrough pain with either bolus doses or a patient-controlled pump. If the provider chooses intermittent dosing, they may administer one millimeter of a saline flush with each bolus dose to clear the catheter.

• If patient-controlled pumps are accessible, boluses of two millimeters of the same solution every 15 minutes, up to a maximum of three boluses per hour, have the benefit of lowering the chance of infection by avoiding multiple manipulations of the intrathecal catheter, which may increase the likelihood of catheter contamination.

What Are the Complications Associated with CSA?

All complications associated with using local anesthetics and spinal anesthesia, in general, are considered CSA complications.

1. Time: The CSA procedure takes more time. However, it may be beneficial to insert the catheter before beginning the case and then quickly induce the block when fully prepared on the operating table, especially with high-risk patients who may experience changes in the depth of the blocks, and cardiovascular instability may occur during movement.

2. Post-Dural Puncture Headache (PDPH): PDPH is caused by a cerebrospinal fluid leak, and the severity is proportional to the size of the dura mater puncture. As a result, where the requirement for a catheter results in an increase in needle size above that generally required for a successful lumbar puncture in a given patient, there is an increased risk of PDPH.

3. Anticoagulation and Spinal Catheters: When a patient is anticoagulated with a spinal or epidural catheter in situ, there is a risk of bleeding and the formation of an epidural hematoma. Rao et al. observed the absence of neurological complications indicative of neuraxial bleeding.

4. Infection: Infection with the possibility of septic meningitis or epidural abscess is a significant complication, most likely with the long-term use of spinal catheters. Kamsler discovered substantial increases in cerebrospinal fluid white cell counts after only a few hours with intrathecal catheters in place. This happened with or without the utilization of local anesthetics, pointing to the catheter as the source.

5. Catheterization (Subdural or Intravascular): Despite the apparent free flow of cerebrospinal fluid from the needle, accidental catheterization of the subdural space may happen. Similarly, the catheter may enter a vessel despite the failure to obtain blood during an aspiration test. Unlike epidural anesthesia, the volumes of local anesthetic administered are typically insufficient to cause clinically significant sequelae such as high block or systemic toxicity.

6. Technical Challenges: Because it is a more complicated process than single-shot spinal anesthesia, CSA is susceptible to various technical issues that may contribute to morbidity or technique failure. Some of these occur more frequently with smaller needle and catheter sets.

   • Once the catheter has been positioned with the spinal needle, challenges with insertion into the subarachnoid space are usual. In order to alleviate these challenges, most commercially produced sets include a stylet and threading aid. Maneuvers to deal with this usually involve rotating the needle, rotating or flushing the catheter as it is advanced, and gently withdrawing the needle before trying to advance the catheter.

   • The needle may become stuck in the catheter, mainly if a blood clot is evident in its tip or lumen, restricting needle removal from the catheter. This necessitates a second lumbar puncture.

   • It can be challenging to remove the catheter stylet after the catheter has been inserted. If this is not possible, a second lumbar puncture is required.

   • Breakage of the catheter is the most dangerous technical complication of CSA. Therefore, when removing spinal catheters, especially fine catheters, extreme caution should be taken, including adequate positioning of the patient with spine flexion to open up the interspinous spaces.

7. Neurotoxicity and Nerve Trauma: In general, cauda equina syndrome, adhesive arachnoiditis, and other long-term or permanent neurological problems have been identified as side effects of spinal anesthesia.

8. Failure of the Method: Failure of the technique can be looked at from two perspectives: insufficient anesthesia following extremely successful catheter insertion and complete failure of the method.

Conclusion:

CSA is an old technique that has been trying to find its place in anesthesia for several decades. It continues to captivate people's interest due to its potential benefits, especially in high-risk patients and lengthy procedures. However, like any procedure, it has certain risks that must be understood and prevented, and it should only be used when the perceived benefits outweigh the risks in a given patient.