In a patient undergoing foot surgery under spinal anesthesia, which statement about immediate physiologic response to incision is true?

In a patient undergoing foot surgery under spinal anesthesia, which statement about immediate physiologic response to incision is true?

• A. Cardiovascular response blocked but adrenergic response not
• B. Adrenergic response blocked but cardiovascular response not
• C. Both adrenergic and cardiovascular responses will be blocked
• D. Neither adrenergic nor cardiovascular responses will be blocked

Answer: (C)

Spinal anesthesia shuts down both the sensory input from the incisional area and the sympathetic outflow to the body region below the block. When the skin is incised, a normal reaction would be a reflex sympathetic discharge that increases heart rate and blood pressure and promotes adrenergic (catecholamine) activity. With the spinal block, those nociceptive signals cannot reach the brain, and the efferent sympathetic pathways that would produce cardiovascular changes are also interrupted in the blocked segments. As a result, the immediate adrenergic response and the cardiovascular adjustments to incision are prevented, so both types of responses are blunted below the level of the block.

Spinal anesthesia shuts down both the sensory input from the incisional area and the sympathetic outflow to the body region below the block. When the skin is incised, a normal reaction would be a reflex sympathetic discharge that increases heart rate and blood pressure and promotes adrenergic (catecholamine) activity. With the spinal block, those nociceptive signals cannot reach the brain, and the efferent sympathetic pathways that would produce cardiovascular changes are also interrupted in the blocked segments. As a result, the immediate adrenergic response and the cardiovascular adjustments to incision are prevented, so both types of responses are blunted below the level of the block.