Saddle Block Anesthesia - An Overview

Introduction:

Saddle anesthesia is used as the primary mode of anesthesia in several surgeries. It is a very simple and safe technique, and induction of anesthesia is easy with this method. It is the preferred method because of its accuracy in producing anesthesia along the nerve distribution and has been used with satisfying results. For a successful block, first, the anatomical structures should be identified, proper patient and instrument preparation is to be done, and harmonious coordination among specialists involved in the surgery is important.

What Is Saddle Block Anesthesia?

Saddle block anesthesia is the anesthesia of the area of the body that comes in contact with a saddle and hence the name. It is a type of low spinal block that mainly anesthetizes areas like the perineum, perineal area, and inner sides of thighs and legs. Several medicines and drugs can be administered through this route, which includes Lidocaine, Bupivacaine, Procaine, Cocaine, and many such anesthetic agents. Prolonged anesthesia can be achieved by administering long-acting anesthetics like Pontocaine and Cinchocaine. It is desirable to other anesthesia techniques like general anesthesia and subarachnoid anesthesia. It is a popular anesthesia technique for surgeries done in the perineal area and has many advantages.

What Is the Anatomy and Physiology of the Spinal Cord?

To attain successful anesthesia with this technique, it is crucial to understand the anatomy and normal physiology of the spinal cord and the structures adjacent to it. The vertebral canal is the anatomical space formed by the vertebral column and contains the spinal cord. It is long and tubular and passes through the foramen of the vertebrae. It is also known as the spinal canal, spinal cavity, or vertebral cavity. It originates from the foramen magnum (largest and oval-shaped foramen at the base of the skull), where it is present together with the medulla oblongata and extends downwards to terminate at the level of first lumbar (L1) in adults and second lumbar (L2) in infants. It ends with a tapering called conus medullaris. The total length of the spinal cord is approximately 17 inches. Three layers of meninges cover the spinal cord called the dura (outermost layer), the arachnoid (middle layer), and the pia mater (innermost layer). Epidural or extradural space is between the dura layer and the bony spinal or vertebral canal. This space is a low-pressure space filled with fat tissue, areolar tissue, arteries, lymphatic vessels, and internal vertebral venous plexus. A possible space between the dura and the arachnoid mater is called subdural space. The subarachnoid space containing the cerebrospinal fluid is between the pia mater and the arachnoid. It is the target site of anesthetic injection.

What Are the Indications of Saddle Block Anesthesia?

Saddle blocks are widely used in many surgical procedures. Some of them are listed below.

• Obstetric and Gynecologic Procedures:
  • Normal childbirth.
  • Low or outlet forceps delivery (delivery done with a pair of forceps when the fetus's head is at the pelvic floor and is visible without separating the outer lips of the vagina.
  • Episiotomy repair surgery (episiotomy is the cut made in the perineum to enlarge the vaginal opening to make it easy for the baby to pass through).
• Urological Procedures:
  • Fournier's gangrene is a bacterial infection of the scrotum, penis, and perineum.
  • TURP (transurethral resection of the prostate) surgery to remove a part of the prostate in men to treat urinary problems.
• Anorectal Procedures:
  • Piles or hemorrhoids are swollen and inflamed veins in the rectum and the anus.
  • The pilonidal sinus is a small tunnel or hole in the skin of the buttocks containing pus or fluid.
  • Anal fistula and fissure.

What Are the Contraindications of Saddle Block Anesthesia?

There are some conditions where a saddle block is not possible. A few of them are listed below.

• Absolute Contraindications:
  • Skin infection at the injection site.
  • Bleeding or clotting disorders.
  • Patient denial.
  • Allergy to an anesthetic agent or its components.
• Relative Contraindications:
  • Septicemia.
  • History of headache after a post-dural puncture.
  • Spinal deformities by birth.
  • Raised intracranial pressure.
  • Neurological disorder.

What Is the Technique of Saddle Block Anesthesia?

• Instruments Needed:
  • Sterile surgical gloves.
  • Sterile disposable drapes.
  • Sterile gauze swabs.
  • Sterile hypodermic needle.
  • Quincke spinal needle (22-25 gauge).
  • Povidone iodine solution.
  • Anesthetic agent (Lidocaine, Tetracaine or Bupivacaine).
  • Ultrasound or fluoroscopy device for the image-guided block.
  • Hemodynamic monitoring devices.
• Patient Preparation:
  • A large bore cannula is inserted to obtain intravenous access to give intravenous fluids.
  • Patient's vitals, like heart rate, blood pressure, and other values, are recorded.
  • No pre-anesthetic medication is required for this block.
  • Emergency drugs like vasopressor and Atropine should be available.
  • The patient is positioned in a sitting position, and the operating site is sterilized.
• Technique:
  • To avoid injury to the conus medullaris, the intercristal line is marked, and the spinous process at the levels of L4 lumbar vertebrae is identified on this line.
  • The interspace between L3 and L4 lumbar vertebrae is located, and a hypodermic needle is inserted into this space through the skin.
  • The injection gives rise to a small superficial swelling on the skin.
  • A spinal needle is inserted into this interspace with a 15-degree angulation towards the head.
  • The needle is advanced till two pops are felt of the ligamentum flavum first and then of the dura-arachnoid membrane.
  • The stylet can be withdrawn to confirm the correct dural placement of the needle, and cerebrospinal fluid leakage is observed.
  • With the use of a smaller gauge, it is necessary to confirm the subarachnoid placement of the needle and to ensure that the needle has not been displaced. It is done by attaching a syringe to the needle and aspirating CSF.
  • If the aspiration is negative for CSF, the needle needs repositioning.
  • The patient is made to remain in the sitting posting for the next 3 to 10 minutes.
  • The degree of sensory anesthesia can be tested by a pinprick test or temperature sensation test to cold with an alcohol swab.
  • Motor anesthesia can be measured by a Bromage scale (the scale uses the ability of leg movements).

What Are the Advantages of Saddle Block Anesthesia?

• It has a rapid and smooth induction of anesthesia.
• It produces a dense block of nerves.
• It is a safe and simple method of anesthesia.
• It numbs the entire area of nerve distribution with increased accuracy.
• It requires a low dosage of drugs.
• It gives complete relief from delivery pain without harming the baby.
• It allows rapid recovery and early patient mobilization leading to a shorter hospital stay.

What Are the Complications of Saddle Block Anesthesia?

• Nerve injury.
• Nerve root damage causing peripheral neuropathy.
• Spinal cord injury leading to paraplegia.
• Cauda equina syndrome (paresthesia of the anal region, loss of bladder or bowel control, and back pain radiating to legs).
• Epidural hematoma (bleeding due to accidental injection into vessels).
• Back Pain and headache (post-dural puncture headache).
• Meningitis.
• Epidural abscess.
• Total or high spinal block.

Conclusion

Saddle blocks are desirable since they do not require tracheal intubation, which can lead to other respiratory problems. In addition, it prevents the need for increased doses of post-operative opioids because of their postoperative analgesic effect. The coordinated work between a surgeon, an anesthesiologist, and nursing staff is required to achieve successful spinal anesthesia with minimal postoperative complications.