Spinal anesthesia is a spinal cord-based form of regional anesthesia. It results in the temporary interruption of the excitation conduction of the spinal nerve roots (nerve roots that branch off from the individual segments of the spinal cord), and thus serves to block pain conduction as well as muscle relaxation. This is done with the help of a local anesthetic injected into the so-called subarachnoid space. The subarachnoid space is located between the pia mater (soft meninges) and the dura mater (hard meninges). The injection of the local anesthetic causes a temporary blockade of motor, sensory and sympathetic perceptual qualities. Spinal anesthesia is used primarily for major surgical procedures below the belly button. This means in the area of the lower abdomen, the pelvis, as well as the perineum and lower extremities. Advantages compared to general anesthesia are mainly for patients who suffer from an increased risk of complications, respiratory diseases or diabetes mellitus. Spinal anesthesia is an effective procedure to perform this variety of surgeries. However, because severe complications can occur, it should only be used by experienced physicians who are proficient in cardiopulmonary resuscitation. Spinal anesthesia is usually performed as bilateral (conventional) spinal anesthesia. Unilateral (one-sided) spinal anesthesia is an appropriate procedure for all surgeries involving only one lower extremity.
Indications (areas of application)
- Surgical procedures on the upper abdomen (caesarean section/caesarean section).
- Operative procedures on the lower abdomen (appendectomy/appendectomy).
- Inguinal hernia (hernia)
- Surgical procedures on the genitourinary tract (renal and urinary system; transurethral resection (TUR)/operation through the urethra).
- Surgical interventions in gynecology.
- Operations on the pelvis and lower extremity – for example, operations on the hip joint or lower leg amputation, knee.
- Perineum (region between the anus and the external sex organs).
- Vaginal delivery (natural birth; spontaneous delivery).
Contraindications
Absolute contraindications
- Lack of patient consent
- Infection at the injection site
- Specific cardiovascular disease – for example, a fresh myocardial infarction (heart attack), severe coronary heart disease (CHD), valvular vitiation (heart valve defects), cerebral atherosclerosis (arteriosclerosis; hardening of the arteries) with the risk of apoplexy (stroke), in severe hypertension (high blood pressure), as well as hypotension (low blood pressure).
- Neurological diseases – For forensic reasons, spinal anesthesia is not performed, for example, in multiple sclerosis (MS), because deterioration of these diseases could otherwise be seen in this context.
- Shock and/or hypovolemia (volume deficiency).
- Sepsis (blood poisoning)
- Spinal stenosis (narrowing of the spinal canal).
- Coagulopathy (disorders of blood clotting).
Relative contraindication
- Anamnestic severe back pain and/or headache.
- Local diseases of the spine: arthritis (joint inflammation), disc prolapse (herniated disc), osteoporosis (bone loss), osseous metastases (spinal metastases)
- High-risk patients
- Severe deformity of the spine
Desired anesthesia extension during surgical intervention:
- Upper abdomen (e.g., caesarean section): Th 4 – 6.
- Lower abdomen (appendectomy):Th 6 – 8.
- Inguinal hernia: Th 8
- Transurethral resection (TUR); vaginal delivery; hip surgery: Th 10
- Knee and below: L1
- Perineum S2-5
Before spinal anesthesia.
Preoperatively, the patient’s medical history (anamnesis) is first taken. Important here is information on allergies to drugs, especially local anesthetics, as well as systemic diseases that can lead to complications during the procedure (eg, cardiovascular disease). This is followed by a physical examination, interpretation of laboratory results, and patient education. This is followed by the administration of premedication (administration of medication prior to a medical procedure), which in this case is primarily for anxiolysis (anxiety relief).
The process
The decision to use spinal anesthesia is derived from the following factors: If the surgical area corresponds to the above-mentioned region and the duration of surgery is more than 10 minutes and less than 3 to 4 hours, spinal anesthesia is appropriate. Furthermore, it should be taken into account that spinal anesthesia should not be used if large blood losses are expected during the operation, since the blockade of the sympathetic nervous system (part of the nervous system that is responsible, among other things, for the constriction of the vessels and thus for hemostasis) increases the probability of bleeding complications. Immediately before spinal anesthesia, blood pressure and heart rate are measured, and these parameters are monitored throughout the procedure. This is followed by placement of venous access and administration of an electrolyte solution. For spinal anesthesia, the patient can be placed either in the lateral position or in a sitting position. It is important that the spinal column is curved (humped), as this pulls the vertebral bodies and spinous processes apart. First, a local anesthetic (local anesthesia) is applied to the puncture site, and then the subarachnoid space is localized. This is done using the loss of resistance technique, where the anesthesiologist is guided by the anatomical resistances encountered by his needle. For this purpose, he uses a syringe that is fluid-filled and whose plunger is smooth. The greatest resistance is formed by the ligamentum flavum (lat. : yellow band). First the needle passes the ligamentum, the anesthesiologist feels the next resistance when puncturing the dura-arachnoid. Now the needle is in the subarachnoid space and the local anesthetic can be completely injected after a test dose. Puncturing tattoos should be avoided, as this may release neurotoxic dyes into the CSF space. An animal study was able to demonstrate inflammatory reactions in the area of the dura mater or the arachnoid (spider skin; middle meninges between the dura mater (hard meninges; outermost meninges) and the pia mater) as a result. Depending on the density of the local anesthetic (LA; agents used for local anesthesia), a distinction is made:
- Isobaric LA: same density as CSF (1010 µg/ ml at 37 °C as awful); in this case, the block expands a little after storage.
- Hyperbaric LA: density is higher than CSF, ie: Blockade spreads downward according to the gravity (addition of glucose).
In unilateral (one-sided) spinal anesthesia, hyper- (or hypo)bare local anesthetic solutions are slowly injected in the lateral position. This procedure requires a slightly longer preparation time and a slower onset of action. In return, however, there is hemodynamic stability and better mobilizability of the patient after the operation. The onset of anesthesia is usually immediate, but may take up to 10 minutes to take effect. The spread of local anesthetic can be influenced by patient positioning and by pressing and coughing. Forms of spinal anesthesia:
- Spinal anesthesia in the saddle block (performed in a sitting position; patient is left in this position for about 5-6 minutes; hyperbaric LA spreads downward according to the gravity) – blockade of spinal segments S1-S5.
- Continuous spinal anesthesia – injection of local anesthetic continuously and as needed through a catheter.
- Combined spinal-epidural anesthesia (synonym: combination spinal-epidural anesthesia (CSE)) – procedure combines the rapid onset of action of spinal anesthesia with the longer duration of action of peridural anesthesia.
After surgery
In the recovery room, the patient must be monitored continuously in terms of blood pressure and heart rate. After spinal anesthesia, special, neurological monitoring is indicated, because in rare cases there is a possibility of spinal hemorrhage. This can lead to severe radicular pain (pain along the catchment areas of the nerve roots from the spinal cord), progressive motor and sensory deficits, and bladder voiding dysfunction and requires immediate neurological treatment. The patient must be monitored as an inpatient and should take it easy.
Possible complications
- Anaphylactic (systemic allergic) reaction.
- Arachnoiditis – infection of the arachnoid (spider skin).
- Bradycardia – slowing of heart activity (heart rate below 60 beats per minute).
- Blood pressure drop – due to sympathetic blockade (this part of the nervous system maintains blood pressure).
- Cauda equina syndrome – bladder emptying disorders, breech anesthesia (sensitive failures of the nerves in the sacrum (sacrum) area), fecal incontinence, paresis (paralysis).
- Purulent meningitis – bacterial meningitis.
- Aseptic meningitis – syndrome with acute onset of meningeal symptoms and fever and increased cell count in the neural fluid without growth of bacteria.
- Spinal hematoma – hemorrhage with compression of the spinal cord.
- Epidural abscess – infection in the peridural space with accumulation of pus.
- Cerebrospinal fluid hypotension syndrome – this is associated with the following symptoms: headache worsens within 15 min of sitting up or standing and improves within 15 min of lying down; associated with at least one of the following symptoms: Meningismus (painful neck stiffness), tinnitus (ringing in the ears), hypacusis (hearing loss), photophobia (photophobia), or nausea (nausea) affecting cranial nerves.
- Hypothermia (hypothermia)
- Cephalgia (headache), postspinal; postspinal headache (PKS).
- Myelitis (inflammation of the spinal cord).
- Micturition disorders (disturbances in the natural emptying of the urinary bladder; occur less frequently under unilateral spinal anesthesia than after bilateral blockade)
- Nerve root injury
- Paraplegia – paralysis of the legs
- Reaction to vasoconstrictor addition – tachycardia (heart palpitations), increase in blood pressure, sweating, mental overexcitement, headache.
- Respiratory disorders
- Total spinal anesthesia – bradycardia, drop in blood pressure, loss of consciousness, respiratory arrest.
- Transient neurological symptoms (TNS) – e.g., plegias (paralysis) and paresthesias (sensory disturbances), as well as bladder and micturition dysfunction
- Nausea (nausea) and vomiting.
- Vagovasal reaction – “blackening of the eyes”, collapse.
Peridural vs. spinal anesthesia
While the effect of spinal anesthesia is very fast and stronger, peridural anesthesia (PDA) requires a slightly longer latency period. In particular, the motor blockade with spinal anesthesia is stronger. The advantage here is a higher quality of anesthesia and better controllability with a smaller amount of anesthetic. Peridural anesthesia requires a higher dose of local anesthetics and is less predictable in its severity with lower anesthetic quality. In application, this means the following: Spinal anesthesia is popular for surgery because of better motor blockade, but it can lead to so-called postspinal headaches. Peridural anesthesia, because of its longer-term effects, is used in continuous nerve block, among other applications, which can take days to weeks to perform.
