High Neuraxial Block (Total Spinal)

Nausea is the warning sign - Nausea, agitation, and akathisia after a neuraxial dose mean the block is climbing, not that she needs more ondansetron. Nausea after a spinal flags hypotension severe enough to matter and should send you straight to a blood pressure and a level check.

Check the level, don't assume it - Bilateral pinprick to a dermatome map is the test — sacral coverage up to a dense T4 is the cesarean target. Cough strength is the respiratory canary: intercostal and abdominal paralysis costs expiratory effort long before tidal volume fails.

Dyspnea is often proprioceptive - Blockade of chest wall and abdominal afferents makes patients feel they cannot breathe when ventilation is fine. Confirm adequate ventilation, then reassure. A patient who cannot cough or whose level is still rising is a different problem.

Bradycardia is the accelerator fibers - Sympathectomy sits two to six dermatomes above the sensory level, so a T4 block can take out T1-T4 cardiac accelerators and leave unopposed vagal tone — bradyarrhythmia, heart block, even sinus arrest. The Bezold-Jarisch reflex adds to it. Have atropine and glycopyrrolate drawn before you dose.

Hypotension - Venodilation pools blood and cuts venous return, and hypovolemia makes it much worse. Phenylephrine or ephedrine, fluid, and left uterine displacement. A modest 5 to 10 degree head-down improves venous return without meaningfully changing spread. Prophylactic IV ondansetron reduces both the hypotension and the bradycardia of spinal anesthesia for cesarean.

Total spinal - Loss of consciousness, apnea, fixed dilated pupils. Treat with ABCs: take over the airway and ventilate, fluid, sympathomimetics, and keep left uterine displacement. Support her through it and the block wears off.

Aspirate and test dose every top-up - Most obstetric high blocks come from an epidural catheter that is intrathecal, including one that has worked for hours. A heart rate rise of about 10 bpm, perioral numbness, or tinnitus points intravascular; rapid dense motor block points intrathecal. If you would rather not give epinephrine, the double test dose works — two 5 mL boluses of plain 2% lidocaine 3 to 5 minutes apart, checking motor block after the first and sensory level after the second.

Dilute regimens are safer - Labor infusions of dilute local anesthetic with a low-dose lipophilic opioid lower the risk of both a high or total spinal and local anesthetic systemic toxicity (LAST) if the catheter is misplaced.

Subdural injection is the mimic - Gradual onset over 10 to 30 minutes, extensive sensory block with minimal motor block, hypotension worse than an epidural but milder than a spinal. If it keeps tracking cephalad it pools intracranially and produces dyspnea and loss of consciousness.

She has a full stomach - Give aspiration prophylaxis before the block, not after the crisis: sodium citrate 30 mL PO, famotidine 20 mg IV, or pantoprazole 40 mg IV, with metoclopramide 10 mg IV.

If she arrests - High-quality CPR with manual left uterine displacement — aortocaval compression will defeat the resuscitation. If the fundus is at or above the umbilicus and there is no ROSC, perimortem cesarean delivery at 4 minutes.

A high neuraxial block is excessive cephalad spread of local anesthetic in the subarachnoid or epidural space. In obstetrics the usual mechanism is an epidural dose landing intrathecally — an unrecognized intrathecal catheter or a catheter that migrated. Sympathetic blockade runs two to six dermatomes above the sensory level, so the T4 level needed for cesarean already means a near-complete sympathectomy with vasodilation, venous pooling, and little time for cardiovascular compensation. Above T1 the cardiac accelerator fibers (T1-T4) drop out and bradyarrhythmias, heart block, or sinus arrest follow the hypotension. Higher still, intercostal and abdominal paralysis takes out cough and expiratory effort, and phrenic (C3-C5) blockade or brainstem hypoperfusion produces apnea and loss of consciousness — a total spinal, classically with fixed dilated pupils.

Pregnancy makes all of this easier to produce. Engorged epidural veins reduce CSF volume, so a term parturient reaches a higher level on less drug.