التخدير النصفي بالصور (ابرة الظهر )

The medication is injected into a sac of fluid in your lower back (the subarachnoid space) which contains the spinal nerves.

The medication blocks the nerves in the lower half of the body. The loss of feeling is temporary and should last from 1 to 4 hours depending on the medication given and other factors

–In an epidural, an indwelling catheter may be placed that avails for additional injections later, while a spinal is a one-shot only.

–The onset of analgesia is approximately 15-30 minutes in an epidural, while it is approximately 5 minutes in a spinal.
–An epidural usually doesn’t cause significant neuromuscular block, while a spinal more often does. An epidural may be given at a thoracic or lumbar site, while a spinal must be injected below L2 to avoid piercing the spinal cord.

صورة توضح مكان دخول الابرة بين فقرات الظهر في الغضروف بعيدا عن الاعصاب

Position of the patient

The patient may be in the sitting position or lateral position (lying on one side). The sitting patient is asked to slouch and bend forward slightly from the waist to increase the curvature of the spine. The lying patient is asked to draw the knees up to the chin for the same reason.

 Coagulopathy.

Insertion of an epidural needle or catheter into the epidural space may cause traumatic bleeding into the epidural space. Clotting abnormalities may lead to the development of a large haematoma leading to spinal cord compression.

 Therapeutic anticoagulation.
( see later)

 Skin infection at injection site.

Insertion of the epidural needle through an area of skin infection may introduce pathogenic bacteria into the epidural space, leading to serious complications such as meningitis or epidural abscess.

 Raised intracranial pressure.

Accidental dural puncture in a patient with raised ICP may lead to brainstem herniation (coning).

 Hypovolaemia.

The sympathetic blockade produced by epidurals, in combination with uncorrected hypovolaemia, may cause profound circulatory collapse.
Relative
 Uncooperative patients

may be impossible to position correctly, and be unable to remain still enough to safely insert an epidural.

 Pre-existing neurological disorders,

such as multiple sclerosis, may be a contraindication, because any new neurological symptoms may be ascribed to the epidural.

 Fixed cardiac output states.

Probably relative rather than absolute. This includes aortic stenosis, hypertrophic obstructive cardiomyopathy (HOCM), mitral stenosis and complete heart block. Patients with these cardiovascular abnormalities are unable to increase their cardiac output in response to the peripheral vasodilatation caused by epidural blockade, and may develop profound circulatory collapse which is very difficult to treat.

 Anatomical abnormalities of vertebral column may make the placement of an epidural technically impossible.
 Prophylactic low dose heparin
　
Regional anesthesia and anticoagulants
　
 Full oral anticoagulation with warfarin or standard heparin (SH) are absolute contraindications to epidural blockade.

 Partial anticoagulation with low molecular weight heparin (LMWH) or low dose warfarin (INR <1.5) are relative contraindications.

 Low dose standard heparin (SH), 5,000units bd s/c is not associated with an increased risk of epidural haematoma. Wait for 4 hours after a dose before performing epidural.

 LMWH : allow 12hr interval between LMWH administration and epidural; this also applies to removal of epidural catheters.

 NSAID’s (including aspirin) do not increase the risk of epidural haematoma.

 Intraoperative anticoagulation using 5000units i/v heparin following epidural/spinal injection appears safe, but careful postoperative observations are recommended. .

 Fibrinolytic and thrombolytic drugs: avoid epidural block for 24 hrs, check clotting prior to insertion.

 Thrombocytopaenia: epidurals are relatively contraindicated below platelet count of 100,000/mm3.

An epidural haematoma should be suspected in patients who complain of severe back pain a few hours/days following any central neuraxial block or with any prolonged or abnormal neurological deficit (including. sensory loss, paraesthesiae, muscle weakness and disturbance of bladder control and anal sphincter tone). A high index of suspicion is required, with early orthopaedic or neurosurgical referral for decompression of the haematoma. Even with early recognition, the morbidity of this condition is still very high

Important complications of regional anaesthesia
 Pain – 25% of patients still experience pain despite spinal anaesthesia

 Post-dural headache from CSF leak

 Hypotension and bradycardia through blockade of the sympathetic nervous system

 Limb damage from sensory and motor block

 Epidural or intrathecal bleed

 Respiratory failure if block is ‘too high’

 Direct nerve damage

 Hypothermia

 Damage to the spinal cord – may be transient or permanent

 Spinal infection

 Aseptic meningitis

 Haematoma of the spinal cord – enhanced by use of LMWH preoperatively

 Anaphylaxis
 Urinary retention