5.2: Complications of Spinal Anesthsia
- Page ID
- 56804
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Spinal anaesthesia can safely provide excellent operating conditions for surgery below the umbilicus. It may also be used, with skill, for some upper abdominal surgery. However the anesthetist must be aware that spinal anaesthesia will block sympathetic nerves, resulting in vasodilatation, which may cause a large fall in the patient’s blood pressure and a decrease in heart rate. A “high” spinal may make the patient unconscious and stop breathing (apnoea). The anesthetist must be skilled at resuscitation and airway management. Obstetric patients must be treated with care.
Contraindications
Spinal anaesthesia is not appropriate for all patients. It is contraindicated in patients who have clotting disorders, infection at the site of lumbar puncture or raised intracranial pressure. Patients must not be hypovolaemic. They should have a normal blood pressure,no postural blood pressure drop and no tachycardia.
Spinal anaesthesia may not be appropriate for patients with septicaemia, anatomical deformities of the back or neurological disease.
The anesthetist must be careful providing spinal anaesthesia for a patient with a difficult airway. It is wise to avoid attempting to intubate these patients but a total spinal or a surgical complication may require the anesthetist to immediately intubate the patient. The choice of anaesthesia for patients with a difficult airway is difficult. Spinal anaesthesia should only be performed if all resuscitation drugs and airway management equipment are available.
All patients must be monitored. The blood pressure, pulse and respiratory rate should be checked every five minutes. The blood pressure can fall rapidly, especially in patients who have a decreased blood volume.
Before performing a spinal anaesthetic the anesthetist must learn how to treat any complications of spinal anaesthesia. The main complications are failure of the anaesthesia, hypotension, nausea and vomiting, shivering, headache, backache,neurological damage and total spinal.
Failure to Perform the Spinal Anesthetic
Failure can occur for several reasons. If the spinal needle always strikes bone the patient’s position should be checked. The anesthetist must ensure that there is maximal lumbar flexion, that the spine is not rotated and that the needle is placed in the midline.If the spinal needle enters the subarachnoid space but no CSF appears then the anesthetist should wait at least 30 seconds, then rotate the needle 90 degrees and wait again. If there is still no CSF the anesthetist may aspirate the needle. If there is still no CSF flow then the spinal will need to be repeated.
Blood in the CSF
If blood flows from the needle the anesthetist should wait a short time to see if the blood clears. If blood continues to flow from the needle, it should be removed and replaced at a level above or below.
Pain on Injection
If the patient complains of pain while injecting the local anaesthetic the anesthetist must stop injecting and reposition the spinal needle.
No Spinal Block
If there is no spinal block (the patient has normal sensation and muscle power) after 10 minutes then the anesthetist may repeat the spinal with the same dose of local anesthetic.
Unilateral / Inadequate Block
If the block is one-sided or not high enough then the patient’s position can be changed to help improve the block. Hyperbaric local anesthetics will flow downwards and hypobaric local anesthetics will flow upwards. It is important to test the extent of the spinal block before allowing the surgeon to operate. Using loss of temperature is easy. A swab soaked in alcohol can be touched to the patient’s arm to show the patient how cold it is and then touched from the legs up, on both sides of the body, until the swab feels cold to the patient.
Hypotension
Spinal anaesthesia will block sympathetic nerves, which will cause vasodilatation and hypotension. The higher the block, the greater the hypotension it will produce. Patients may have other symptoms before the blood pressure falls and the anesthetist must check the patient for pallor, sweating, nausea or feeling unwell.
Intravenous fluids must be administered to all patients who receive spinal anaesthesia.Hypovolaemia must be corrected before starting the spinal anaesthetic. Hypotension is also more likely in obstetric patients when aortocaval compression may occur.Administering intravenous fluid before spinal anaesthesia may not be effective in preventing hypotension however it is wise to treat any dehydration due to fasting with 500 to 1000 ml of fluid. If the blood pressure does not increase with fluid administration or if the hypotension is severe the anesthetist must give a vasoconstrictor. The choice of intravenous vasoconstrictor drugs includes ephedrine 5 to 10 mg, methoxamine 2 mg, phenylephrine 0.5 mg, metaraminol 0.5 to 1 mg or adrenaline 0.05 mg. The anesthetist may need to give repeated doses. Sympathetic nerves to the heart, which increase heart rate, come from the thoracic levels T1 to T4. If the spinal anaesthesia blocks these nerves, then the patient will be hypotensive (due to the vasodilatation) and bradycardia.These patients may also require atropine as well as intravenous fluids and vasoconstrictors.
Nausea and Vomiting
Nausea and vomiting are usually symptoms of hypotension and will resolve when the hypotension is treated.
Backache
Mild backache is common after spinal anaesthesia. This is self-limiting
Headache
Headache after spinal anaesthesia (post-dural puncture headache PDPH) is more common in women and in younger patients. Also the larger the size of the spinal needle the more frequent the incidence. A 16 gauge needle will cause headache in 75% of patients, a 20 gauge in 15% and a 25 gauge in 1 to 3%. The headache is thought to be due to leakage of cerebrospinal fluid causing the stretching of meningeal vessels and nerves. Spinal headache may be mild to severe, is located at the front or back of the head and may involve the neck and upper shoulders. The severity of the headache changes with position, becoming worse when standing and less when lying down. Coughing,sneezing and vomiting increases the headache. Patients may also have nausea, loss of appetite, ringing in the ears, deafness, blurred vision and photophobia. Onset is usually 24 to 48 hours after the spinal anaesthetic. The headache will eventually resolve but may take weeks. Using a smaller gauge spinal needle will reduce the incidence of spinal headache. If available, a pencil-point spinal needle rather than a cutting-point spinal needle will further reduce the incidence. Post spinal headache can be treated with bedrest, intravenous and oral fluids, caffeine-containing drinks like coffee, tea or Coca Cola® and analgesics. The anesthetist may wish to treat severe post dural puncture headache with an epidural blood patch. 70% of patients will be treated successfully by one epidural blood patch and 90% by a second patch. An epidural needle is inserted into the epidural space and 15 to 20 ml of the patients own blood taken at the time is injected into the epidural space. Often the patient complains of back discomfort. The blood must be taken and given in a way that avoids all risk of infection.
Total Spinal
Total spinal is a very rare but life-threatening complication. It usually occurs when an epidural dose of local anaesthetic is mistakenly injected into the spinal space. The patient becomes very hypotensive and bradycardic as all sympathetic nerves are blocked. They will require large volumes of intravenous fluid and repeated doses of vasoconstrictors. Atropine can be used to treat bradycardia. As the height of the spinal block increases the patient will develop weakness and tingling of the arms and hands.This indicates that the spinal block has reached the lower cervical nerves. As the intercostal nerves are blocked the patient will have difficulty taking a deep breath. When the phenic nerves (C345) are blocked the patient will stop breathing. The anesthetist must always monitor the patient. Marked hypotension, bradycardia and weakness in the hands are warning signs that the patient may develop a total spinal. If these signs occur the anesthetist must treat the hypotension and bradycardia and prepare to establish a clear airway and ventilate with oxygen. Obstetric and non-fasted patients are at risk of aspiration and need endotracheal intubation. A total spinal may not relax the jaw and the patient may require suxamethonium for intubation.
Permanent Neurological Complications
Permanent neurological complications are extremely rare. They may occur from damage to the spinal cord or spinal nerves by the needle, injection of the wrong drug, infection(meningitis or epidural abscess) or damage to an epidural vein causing an epidural haematoma that compresses the spinal cord. If the anesthetist only performs a spinal asa sterile procedure then the risk of infection is extremely low. An epidural haematoma is only likely to happen in patients with abnormal coagulation (platelet count less than 100,000 or INR greater than 1.3). Patients with abnormal clotting must not have spinal or epidural anaesthesia.