67 Questions
What is the primary effect of sympathetic overactivity on gut smooth muscle?
Inhibition of gut smooth muscle via activation of α & β-adrenergic receptors
What is the effect of epidural block on sympathetic-mediated GI reflexes?
Block of sympathetic-mediated GI reflexes
What is the potential consequence of severe hypotension on local perfusion?
Worsened local perfusion
What is the effect of epidural analgesia on the incidence of postoperative ileus?
Decreases the incidence of postoperative ileus
What is the difference in postoperative ileus duration between epidural analgesia with local anesthetic regimen and opioid-based regimen?
36 hours
What is the effect of an imbalanced sympathetic and parasympathetic nervous system on GI blood flow and anastomotic mucosal perfusion?
Increased GI blood flow and anastomotic mucosal perfusion
What is the primary factor that determines the extent of the GI tract's response to regional anesthesia?
Type and extent of the block
What is postoperative ileus characterized by?
Disruption of normal coordinated movements of the GI tract
How long may the transit time of the stomach be extended in postoperative ileus?
24 to 48 hours
What is the main pathophysiologic event leading to postoperative ileus?
Neuroimmune interaction
What is a key factor in initiating postoperative ileus?
Manipulation of intestines and stress response
How long may the effects of postoperative ileus continue after surgery?
3 to 4 days
Which of the following is NOT a factor contributing to postoperative ileus?
Parasympathetic overactivity
Which type of epidural analgesia is commonly used for GI surgeries?
Thoracic epidural analgesia
What is the primary mechanism by which epidural administration of local anesthetics or opioids reduces postoperative morbidity?
By suppressing the surgical stress response and associated sympathetic overactivity
What is the potential consequence of severe hypotension on GI perfusion?
It worsens GI perfusion and may be associated with adverse outcomes
What is the primary advantage of epidural analgesia with local anesthetic regimen compared to opioid-based regimen?
It is associated with a shorter duration of postoperative ileus
What is the primary benefit of maintaining a balanced sympathetic and parasympathetic nervous system in the postoperative period?
It improves GI blood flow and anastomotic mucosal perfusion
What is the concern among clinicians regarding the effect of unopposed parasympathetic activity on enteric anastomosis?
Increased risk of anastomotic leaks
What did animal studies find when comparing epidural anesthesia to general anesthesia in terms of anastomotic bursting pressure?
No difference in anastomotic bursting pressure
What is the effect of neuroaxial blocks on GI blood flow and tissue oxygenation?
Improved GI blood flow and tissue oxygenation
What is the conclusion of the literature regarding the effect of neuroaxial blocks on enteric anastomotic leakage?
Neuroaxial blocks have no effect on enteric anastomotic leakage
What is the result of the systemic stress response and catabolic activity in the early postoperative period after GI surgery?
Postoperative weakness and muscle wasting
What is the benefit of epidural analgesia in the context of major GI surgeries?
decrease opioid requirements & reduce postoperative ileus. enhances enteral feeding.
What is the underlying mechanism by which epidural analgesia improves postoperative outcomes in major GI surgeries?
Block of afferent stimuli and the endocrine metabolic responses
What is the primary goal of an enhanced recovery after surgery (ERAS) protocol for major GI surgeries?
To facilitate oral nutrition
What is the relationship between epidural analgesia and postoperative ileus in the context of major GI surgeries?
Epidural analgesia reduces postoperative ileus
What is a major factor in reducing the incidence of postoperative nausea and vomiting?
Avoiding systemic opioids and using epidural analgesia
What is a common effect of spinal anesthesia, especially with T6 to L1 block?
GI hyperperistalsis
Which type of anesthesia is associated with the highest risk of nausea and vomiting?
Spinal anesthesia
In the setting of regional anesthesia, what should be paid attention to?
Unopposed vagal activity, LA systemic toxicity, hypotension, and medication administration
What is the primary effect of lumbar epidural anesthesia on blood vessels?
Dilation of both arterial and venous vessels
What is the effect of thoracic epidural anesthesia on mesenteric blood flow and oxygen consumption?
Maintained blood flow and oxygen consumption
What is the effect of vasoconstrictor on blood volume during thoracic epidural anesthesia?
Decreases blood volume in splanchnic region, but increases in thoracic region
What is the effect of adrenergic agonists on blood volume?
Moves existing blood volume from unstressed to stressed
What is the effect of fluid infusion on blood volume?
Increases total blood volume
What is the effect of splanchnic vasculature constriction on systemic circulation?
Shifts blood volume from splanchnic region to systemic circulation
What happens to the total blood volume when fluid is infused?
It increases
What is the effect of adrenergic agonists on blood vessels in normovolemic patients?
They constrict veins and have no effect on arteries
What happens to the stressed volume when α-adrenergic agonists are used?
It increases
What is the effect of α-adrenergic agonists on the stressed volume in veins?
They increase the stressed volume
What is the primary goal of Enhanced Recovery After Surgery (ERAS) protocols for gastrointestinal procedures?
To accelerate postoperative convalescence and reduce general morbidity
What is a key component of ERAS protocols for gastrointestinal procedures?
Multimodal analgesia and early mobilization
What is the benefit of using ERAS protocols in gastrointestinal procedures?
Shorter hospitalizations
What is NOT a key component of ERAS protocols for gastrointestinal procedures?
Opioid use
What is the focus of ERAS protocols for gastrointestinal procedures?
Perioperative regimen with emphasis on multiple interventions
What is the effect of perioperative oral carbohydrates on insulin sensitivity?
It decreases insulin resistance by 50%.
What is the benefit of enteric feeding in the postoperative period?
It prevents bacterial translocation or gut barrier failure.
What is the effect of carbohydrate loading on cellular metabolism?
It shifts the cellular metabolism to an anabolic state.
What is the recommended preoperative fasting period for solids, according to most societies?
6 hours
What is the benefit of early postoperative feeding?
It maintains metabolic and nutritional homoeostasis.
What is an additional benefit of epidural analgesia in the context of ERAS protocols?
Improving respiratory and cardiovascular function
What is a potential adverse effect of hypothermia in the postoperative period?
Increased risk of wound infection
What is the primary purpose of using nasogastric tubes following major intraabdominal surgery?
Gastric decompression
What is an adverse effect of bowel preparation on patients?
Decreasing exercise capacity
What is the effect of the presence of gastric tubes on the body?
Increasing gastric secretion and motility
What is a potential complication of using nasogastric tubes?
Wound infections
What is the purpose of intraabdominal drains in surgery?
To prevent accumulation of intraabdominal collections
What is the result of preoperative starvation period in patients undergoing elective surgery?
A fluid deficit that may stimulate the production of antidiuretic hormone
What is taken into account during intraoperative fluid management?
The preoperative fluid deficit, the presence of a regional anesthesia technique, hemorrhage, and third-space losses
What is the consequence of using intraabdominal drains in surgery?
They can be associated with bacterial contamination, wound infection, and other complications
What is the recent NPO guideline for patients undergoing surgery?
Patients should not have any clear fluids up to 2 hours prior to surgery
What is the effectiveness of routine use of drainage after colorectal anastomoses?
It has no effect on anastomotic leakage and other complications
What is the primary benefit of early postoperative ambulation in the prevention of postoperative complications?
Prevention of postoperative thromboembolism
What is the outcome of studies examining the effect of early postoperative ambulation on GI myoelectrical activity patterns?
GI myoelectrical activity patterns are not always expedited by early postoperative ambulation
What is the advantage of early postoperative ambulation besides the restoration of normal bowel function?
prevention and treatment of postoperative ileus
What is the goal of early postoperative ambulation in relation to postoperative ileus?
To restore normal bowel function
Study Notes
• Surgical stress response is a multifaceted, neurohumoral response to surgical stimulation, associated with considerable morbidity, including systemic inflammatory response syndrome, release of systemic inflammatory response, and adrenaline & noradrenaline hormones. • Epidural administration of local anesthetics or opioids can suppress these responses, resulting in block of afferent & efferent sympathetic-mediated GI reflexes, but leaving parasympathetic innervation intact. • Epidural block is associated with improved GI blood flow and anastomotic mucosal perfusion, controlling pain and decreasing the need for opioids. • Severe hypotension (>50% reduction in SBP) may be associated with worsened local perfusion, but vasoactive drugs like NOR can attenuate this effect and improve colonic perfusion. • Epidural analgesia can effectively decrease the incidence of postoperative ileus, with a Cochrane review showing that epidural usage reduces postoperative ileus by 36 hours when using local anesthetic regimen compared to opioid-based regimen. • Postoperative ileus is a temporary state of GI motor dysfunction, including disruption of normal coordinated movements of the GI tract, nonmechanical obstruction of bowel, activation of inhibitory reflexes, inflammatory mediators, bowel manipulation, electrolyte disturbances, opioid administration, sympathetic overactivity with surgical pain, and postoperative pain. • Transit time of stomach may extend 24 to 48 hours and colon transfer time may increase 48 to 72 hours, with some effects continuing for up to 3 to 4 days after surgery. • The main pathophysiologic event is neuroimmune interaction, based on the bidirectional communication between immune system within and outside the GI tract & autonomic nervous system. • Manipulation of intestines & stress response associated with postoperative pain are the key factors initiating postoperative ileus. • Epidural analgesia can decrease opioid requirements, reduce postoperative ileus, and enhance enteral feeding, facilitating oral nutrition. • Avoiding systemic opioids and using epidural analgesia helps reduce incidence of nausea & vomiting. • Unopposed vagal activity, LA systemic toxicity, hypotension, and medication administration should be considered when managing postoperative nausea and vomiting. • Spinal anesthesia poses the highest risk for the development of nausea & vomiting, seen in 20% of patients. • The degree of arterial hypotension induced by spinal/epidural anesthesia is directly related to the extent of the block, dose of LA used, and baseline hemodynamics. • Lumbar epidural anesthesia leads to arterial & venous dilation at the segments affected by anesthetic, while TEA is associated with pronounced mesenteric vasodilation & arterial hypotension. • Epidural anesthesia with sensory block at T4 to T5 increases blood volume in both the intrathoracic and splanchnic vasculature, while addition of vasoconstrictor decreases volume within splanchnic region but increases volume within the thorax. • Infusion of fluid or use of adrenergic agonists increases stressed volume, with α-adrenergic agonists being more beneficial than infusion of fluid in many situations. • ERAS is an interdisciplinary, multimodal concept aimed at accelerating postoperative convalescence and reducing general morbidity by simultaneously applying several interventions.
This quiz assesses your understanding of how regional anesthesia affects the gastrointestinal system, including the degree of impact on gastrointestinal motility and postoperative ileus. It also covers the effects of epidural analgesia on GI surgeries. Test your knowledge of anesthesia's effects on GI physiology.
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