Anesthesia Student Survival Guide.pdf - Index of

316 ● AnesthesiA student survivAl Guide
Spinal Anesthesia
Single­shot spinal anesthesia produces rapid, reliable surgical anesthesia
with a fairly predictable duration. Because peritoneal traction occurs, a T4
sensory level is considered ideal for most patients. Vagal afferents may explain
the sensation of visceral discomfort even though the block appears to
be “adequate.” Prior to surgical incision, the presence of surgical anesthesia
must be verified with objective testing (e.g., pin-prick). Prolonged operations
are often best managed with a catheter-based technique (e.g., combined-spinal
epidural, continuous epidural, continuous spinal).
Intrathecal injection of small doses of lipophilic opioids (e.g., fentanyl)
may help to alleviate some of the visceral discomforts of a cesarean section.
Intrathecal morphine can provide good post-operative analgesia, though pruritus,
nausea, and respiratory depression limit the enthusiasm of some practitioners
for this technique.
Preemptive bolus administration of intravenous fluid may help reduce
the hemodymanic consequences of spinal anesthesia. If hypotension occurs,
it must be treated aggressively with intravenous fluid, ephedrine, or low dose
phenylephrine. As always, attention must be given to proper left uterine
displacement, because this aggravates hypotension.
Bradycardia will typically manifest when the block reaches a high thoracic
level (T4). Bradycardia and hypotension unresponsive to initial resuscitative
attempts must be promptly treated with epinephrine. Respiratory compromise
may occur with a high spinal (level above T1).
Epidural Anesthesia
In contrast to spinal anesthesia, epidural anesthesia affords a more gradual
onset of hemodynamic changes that may be preferable in some scenarios.
Unfortunately, epidural anesthesia is less profound, frequently patchy or unilateral,
requires high doses of local anesthetic, and takes more time to establish.
For safety and convenience, epidural anesthesia is usually established via
intermittent bolus of an indwelling epidural catheter. With a lumbar epidural,
15–25 mL of local anesthetic (0.5% Bupivacaine, 0.5% Ropivacaine, 1.5–2%
Lidocaine, 3% Chloroprocaine) is typically required to achieve surgical anesthesia.
If patients are appropriately monitored, epidural morphine may be
included for post-operative pain. Epinephrine is often added to epidural local
anesthetics to decrease systemic absorption.