Thursday, March 18, 2021

Anesthesia for Emergency Appendectomy Case File

Posted By: Medical Group - 3/18/2021 Post Author : Medical Group Post Date : Thursday, March 18, 2021 Post Time : 3/18/2021
Anesthesia for Emergency Appendectomy Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 11
A 27-year-old woman presents to the emergency department complaining of abdominal pain, nausea, and vomiting. Her pain began in the peri-umbilical region and has now migrated toward the right lower quadrant of the abdomen. Her serum HCG is negative. A surgery consult is obtained, and based on her history, physical, and findings suggestive of acute appendicitis seen on abdominal CT scan, she is scheduled for emergency appendectomy. The patient is otherwise healthy and takes no regular medications. Her surgical history includes a tonsillectomy at age 10, and a dilatation and curettage (D&C) at age 25. She has not had problems with previous anesthetics.

➤ What would you include in your preoperative evaluation of this patient?
➤ What medications will you use for induction and maintenance of anesthesia?
➤ How will you manage postoperative pain in this patient?

ANSWERS TO CASE 11:
Anesthesia for Emergency Appendectomy

Summary: A healthy woman presents with acute appendicitis. The urgent nature of the surgery precludes any delay due to risk of rupture and subsequent peritonitis.

Preoperative evaluation: Complete history and physical examination, and time of last ingestion of food or contrast. Because of her age and healthy status, no laboratory tests are required.

Medications used for induction and maintenance of anesthesia: 
Combination of a narcotic, an inhalational agent, and a muscle relaxant. The patient will receive general anesthesia, with a rapid sequence induction to minimize the chances of aspiration. The choice of induction agent will not significantly impact her hemodynamic status, as the patient is neither hypovolemic nor hypotensive.

How to manage postoperative pain: Postoperative pain is managed with intravenous narcotics. Other postoperative issues that may present are nausea, vomiting, and ileus.


ANALYSIS

Objectives
1. Consider the elements of the preoperative evaluation and optimization prior to emergency abdominal surgery (airway examination, comorbidities, hemodynamic status, perforated vs. nonperforated appendicitis, NPO guidelines, and other testing as indicated by the patient’s comorbidities).
2. Understand the techniques used in patients with “full stomachs” including rapid sequence induction and aspiration prophylaxis.
3. Consideration implication of surgical procedure on anesthesia: full stomach precautions and rapid sequence induction, laparoscopic versus open appendectomy, fluid management, premedication, prophylaxis for postoperative nausea and vomiting, postoperative pain control.


Considerations
Several special considerations are warranted in this healthy, young woman scheduled for an emergency surgical procedure. Appendectomy is a minor surgical procedure with a low probability of significant blood loss, so an adequately running peripheral intravenous suffices for intravenous access.

A physical examination and review of the patient’s vital signs can help determine the patient’s volume status and hemodynamic stability. Volumedepleted patients should receive resuscitative fluids before proceeding with anesthesia. Many patients presenting with acute appendicitis are febrile and tachycardic at baseline, so a “tilt test” may be helpful to determine degree of intravascular depletion.

Since the patient is of reproductive age, it is important to inquire about the possibility of pregnancy. Many institutions routinely perform pregnancy tests in women of reproductive age undergoing surgery; others inquire, and a pregnancy test may be performed if the history indicates such a possibility.

The anesthetic plan in this patient is general anesthesia with endotracheal intubation, controlled mechanical ventilation, and standard monitoring. Since the procedure is an emergency, the patient is unlikely to have fasted as she would have before a scheduled surgical procedure. Moreover, pain in and of itself reduces gastric emptying. Thus she is said to have a “full stomach,” and will thus require precautions to prevent the aspiration of gastric contents. In the operating room, the standard monitors are applied, and the patient is preoxygenated (≥ 3 minutes). Anesthesia is induced with propofol 1.5 to 2.5 mg/kg. Cricoid pressure (Sellick maneuver) is applied by an assistant to reduce the risk of passive regurgitation of gastric contents. Succinylcholine 1 to 2 mg/kg is administered for paralysis, and the patient is intubated.

Patients are typically paralyzed for abdominal surgery in order to facilitate exposure of the surgical field, and minimize trauma to the abdominal muscles. Once the patient recovers from the short-acting neuromuscular blocker, succinylcholine, she is treated with a longer-acting, nondepolarizing blocker, vecuronium.

Two potential postoperative problems are optimally addressed preemptively, and prior to emergence. First, morphine 0.1 mg/kg is administered during the case as an adjuvant to anesthesia and for postoperative pain relief. Second, young women are most likely to experience postoperative nausea and vomiting. Ondansetron, 4 mg, is given in the last 15 minutes of case to reduce the incidence of this unpleasant complication.

At the end of the surgery, the patient’s muscle relaxation is reversed with neostigmine 0.05 mg/kg and glycopyrrolate 0.01 mg/kg. Before she is fully responsive, the normal airway reflexes are absent, and she is unable to protect her airway from the aspiration of stomach contents. She is extubated once she is alert, following commands, and shows good strength. Following extubation, the patient is transferred to the post-anesthesia care unit (PACU) for postoperative care.


APPROACH TO
Anesthesia for Emergency Appendectomy


DEFINITIONS
PREOXYGENATION: Since room air is only 21% oxygen, and since the patient will be paralyzed and apneic during intubation, it is desirable for the patient to have additional oxygen reserves. This is accomplished by asking her to breathe 100% oxygen for 3 minutes prior to induction. Alternatively, six large breaths of 100% oxygen have been shown to be equally effective.

In addition to inspiring oxygen, “denitrogenation” also occurs as the nitrogen in plasma, which reflects the nitrogen concentration in room air, seeks equilibrium, and diffuses out across the alveolus. This process of denitrogenation is actually as important as the inspiration of oxygenation in preventing alveolar hypoxia and hypoxemia. The rationale for preoxygenation is that in the event that a patient cannot be ventilated or intubated, he or she will have adequate oxygen in reserve to survive long enough to awaken and resume breathing.

RAPID SEQUENCE INDUCTION (RSI): A technique of rapid induction and intubation used to minimize the risk of aspiration. It involves preoxygenation by mask, the administration of an intravenous induction agent immediately followed by a rapid acting neuromuscular blocking drug, and the use of cricoid pressure. Mask ventilation before endotracheal intubation is avoided to prevent insufflation of gas into the patient’s stomach.

CRICOID PRESSURE (SELLICK MANEUVER): Cricoid pressure is the posterior displacement of the cricoid cartilage against the vertebral body in attempt to occlude the esophagus. It is applied by an assistant before the loss of consciousness (and protective airway reflexes), and is released only after correct placement of the endotracheal tube has been confirmed.

SUCCINYLCHOLINE: A depolarizing neuromuscular blocker often used for rapid sequence induction because of its rapid onset (usually <60 seconds). Potential side effects include myalgias, bradycardia and arrhythmias, hyperkalemia in certain patients (recent burn injury, upper and lower motor neuron disease, prolonged bed rest, muscular dystrophies, and closed head injuries). Succinylcholine can trigger malignant hyperthermia in susceptible patients.

MALIGNANT HYPERTHERMIA (MH): A potentially lethal hypermetabolic syndrome that occurs in susceptible patients after exposure to a triggering anesthetic agent. The presenting signs include tachycardia, acidosis, hypercarbia, sustained muscle contraction, hypoxemia, and hyperthermia. Common triggering agents include succinylcholine, and volatile anesthetics including halothane, enflurane, desflurane, sevoflurane, and isoflurane.

POSTOPERATIVE NAUSEA AND VOMITING (PONV): A common side effect seen in patients undergoing general anesthesia. Risk factors include prior history of postoperative nausea, motion sickness, major abdominal surgery, nonsmoker, female gender, and use of opioids.


CLINICAL APPROACH

Aspiration
The American Society of Anesthesiologists has described and standardized guidelines for fasting or “NPO (nothing by mouth) Guidelines” for patients prior to elective surgery. The guidelines require an abstinence from clear liquids for 2 hours, and from milk or a light meal for 6 hours. But the patients undergoing emergency surgery are in a different category. Pain, trauma, and abdominal emergencies are associated with a delay in gastric emptying, thus increasing the risk of these patients for the aspiration of gastric contents. Certain diseases, such as diabetes delay gastric transit time and may also pose an aspiration risk. Other conditions associated with increased aspiration risk are ileus, obesity, pregnancy, hiatal hernia, scleroderma, and altered mental status which occurs following stroke.

The risk of aspiration with anesthesia is 5 events per 10,000 anesthetics. Since the mortality from aspiration is significant and varies from 3% to 70%, all patients presenting for emergency surgery should be treated as though they have a full stomach. Early studies showed that the risk of aspiration and the resulting damage to the respiratory mucosa increase with a gastric volume of more than 25 mL and pH less than 2.5. So some practitioners attempt to reduce the volume and increase the pH of the gastric contents. Nonparticulate antacids such as sodium citrate decrease the acidity, but increase gastric volume. Histamine receptor antagonists such as ranitidine decrease the secretion of gastric acid, but do not affect the acidity of the contents already present in the stomach (thus reducing the value of their administration just prior to an anesthetic). Metoclopramide stimulates gastric emptying, and increases the lower esophageal sphincter tone. Anticholinergic drugs like glycopyrrolate decrease the gastric secretions, but also decrease the lower esophageal sphincter tone, an undesirable trait in the presence of a full stomach. However, none of these drugs have been shown to alter the incidence of aspiration, and none of them are approved by the Food and Drug Administration for aspiration prophylaxis.

The use of a nasogastric tube to decompress the stomach is common, but controversial, as it does not guarantee gastric emptying. Somewhat paradoxically, a nasogastric tube may actually be detrimental by mechanically decreasing tone of the upper and lower esophageal sphincters, and acting as a “wick” to facilitate the movement of gastric contents into the pharynx.

Patients presenting for abdominal emergencies can also present with ileus. Factors predisposing for ileus include narcotics, antacids, anticoagulants, phenothiazines, ganglionic blockers, metabolic derangements like hyponatremia, hypokalemia, hypomagnesemia, sepsis, infection, and inflammation. Ileus can also persist in the postoperative period as well. Small bowel function commonly recovers within a day and gastric motility within 1 to 2 days. However, colonic motility can take up to 5 days. Thus even though patients status post abdominal surgery may have been fasted, they still require attention to the risk of aspiration if an additional operation is required.


Preoperative Optimization: Resuscitation of Blood Volume
Patients presenting with an acute abdomen are often quite dehydrated as a result of vomiting and loss of fluids into the intestine. This may be reflected as tachycardia, oliguria, altered sensorium, decrease in skin turgor, dry mucus membranes, and orthostatic hypotension. It may also manifest as increased variation of pulse pressure with respiration, if not outright tachycardia. An elevated hematocrit is suggestive of dehydration, and serum electrolytes may be abnormal since severe vomiting can lead to metabolic alkalosis due to loss of gastric acid. Patients should receive adequate and appropriate volume resuscitation prior to the induction of anesthesia to prevent significant hypotension due to vasodilation caused by some anesthetic drugs, as well as the removal of the patient’s endogenous sympathetic responses to pain once anesthesia is induced.

The anesthetic options for an open appendectomy are general anesthesia or central neuraxial anesthesia. The usual practice is general anesthesia, using a rapid sequence induction and tracheal intubation. Previously known as a “crash” induction, the rapid sequence induction is not without hazard. Complications include failure to ventilate due to closure of the vocal cords, cricoid ring fracture, esophageal rupture, and profound hypotension. It involves the application of cricoid pressure to minimize the risk of aspiration. First described by Sellick in 1961, it is designed to cause temporary occlusion of the upper end of the esophagus by posterior pressure of the cricoid cartilage ring against the cervical vertebra. Active vomiting, cervical spine injury, and tracheal injury are contraindications to the use of cricoid pressure.

Propofol is most frequently used as the induction agent of choice due to its rapid onset, short duration of action, and smooth and pleasing emergence. However, propofol causes vasodilation, so its use presupposes that the patient is well hydrated and not demonstrating signs of hypovolemia. The typical dose of propofol is 1.5 to 2.5 mg/kg for induction, although the individual dose requirement varies markedly. In patients in whom hypotension is a concern, ketamine (1 mg/kg i.v.) or etomidate (0.1-0.4 mg/kg i.v.) are suitable alternatives. Because of its rapid onset, succinylcholine (1-1.5 mg/kg i.v.) is the neuromuscular blocking drug of choice in rapid sequence inductions. Its short duration allows the paralyzed patient, who can neither be ventilated nor intubated, to resume breathing promptly, thus lessening the likelihood of morbidity when compared to the longer-acting neuromuscular agents.

Once intubation is accomplished and proper endotracheal tube placement is confirmed, cricoid pressure can be released. If intubation is unsuccessful, cricoid pressure should be maintained continuously during subsequent intubation attempts and during mask ventilation.

Another possible approach is neuraxial anesthesia (such as spinal). Indeed, spinal may be preferred in pregnant patients in order to minimize the systemic concentrations of general anesthetics. However, the sensory level required for a routine appendectomy is T4, which is quite high.

An open appendectomy is a short procedure, hence the anesthetic agents used should have a short half-life to facilitate quick emergence. Desflurane and sevoflurane have low blood-gas partition coefficients, thus low solubility in blood, and are suitable for short procedures. The role of nitrous oxide in the maintenance of anesthesia is controversial due to its effect on bowel distention and postoperative nausea and vomiting. Muscle relaxants are required for adequate surgical visualization. In general, intermediate-acting nondepolarizing agents are used in appropriate doses.

It is important to ensure that the patient is awake and following commands prior to extubation. If a patient can follow commands, then his or her laryngeal reflexes, which enable the larynx to close during vomiting, are likely to be intact. Conversely, patients who are unable to follow commands are also unlikely to be able to protect their own airways.

If a patient vomits, the head of the bed should be dropped ten degrees and the pharynx suctioned. Intact laryngeal reflexes enable the patient to clear secretions and protect their airway. Respiratory criteria for extubation include adequate tidal volumes, a normal respiratory rate, and the ability to cough and breathe deeply. A sustained head lift lasting 5 seconds typically predicts that the muscle relaxants have been successfully reversed.


Postoperative Complications
Nausea and vomiting are troublesome complications of anesthesia, especially in young women. The etiology of postoperative nausea and vomiting is multifactorial. The vomiting centre is located in the area postrema of the brainstem and receives vagal afferents from the gastrointestinal tract. Selective serotonin receptor antagonists like ondansetron, dolasetron, and granisetron have proven to be effective in alleviating postoperative nausea and vomiting with minimal side effects when administered just prior to the end of a case. Other classes of drugs including anticholinergics, dopamine antagonists and antihistamines may also be utilized, but have significant side effects. Clonidine, dexamethasone, and acupuncture have also been found to be effective. Combination of therapies for the prevention of postoperative nausea and vomiting provides maximal benefit.

The management of postoperative pain should begin in the operating room. The goal is to minimize any potential sensitization of the spinal cord and brain propagated by tissue injury and pain stimuli. One method of the preemptive analgesia involves central neuraxial blockade. However, if a general
anesthetic is used, local field block in the area of the incision is effective as well. Opioids are most widely used to control postoperative pain but have significant side effects like ileus, respiratory depression, nausea, and vomiting. Nonsteroidal anti-inflammatory drugs (NSAIDs) may also be used for postoperative pain control in these patients.


Comprehension Questions
11.1. During a rapid sequence induction, when would it be appropriate to release cricoid pressure?
    A. When the patient becomes unconscious.
    B. After the induction agent has been given but before the neuromuscular blocking drug is given.
    C. After proper placement of the endotracheal tube has been confirmed.
    D. Cricoid pressure is not indicated in this instance.

11.2. Which of the following is the most significant risk factor for postoperative nausea and vomiting?
    A. Female gender
    B. Surgery on the breast
    C. Smoking
    D. Nonsteroidal anti-inflammatory agents given during surgery
    E. Age over 60 years

11.3. Which of the following is the major advantage of spinal anesthetic in the pregnant patient?
    A. A peripheral neuraxial block minimizes central sensitization to pain.
    B. The level of a spinal anesthesia necessary for an appendectomy is quite low.
    C. Spinals rarely cause headaches in pregnant patients.
    D. A spinal anesthetic allows for anesthesia without significant plasma concentrations of the anesthetic.


ANSWERS
11.1. C. Cricoid pressure or Sellick’s maneuver is intended to occlude the esophagus to prevent passive regurgitation of gastric contents into the airway. It should be maintained throughout the induction sequence until proper endotracheal tube placement has been confirmed or until successful intubation occurs and during mask ventilation, if needed. Cricoid pressure is indicated in this case.

11.2. A. Postoperative nausea and vomiting is most common in women, young people, and patients who have received opioids during surgery. Surprisingly, perhaps the one advantage of smoking (option C) is that smokers tend to have less postoperative nausea and vomiting than nonsmokers. Similarly, the incidence of postoperative nausea and vomiting is lower in the geriatric population.

11.3. D. The major advantage of spinal anesthetic in the pregnant patient is that a spinal anesthetic allows for anesthesia without significant plasma concentrations of the anesthetic. While a peripheral block may minimize central sensitization to pain, it is hardly adequate as an anesthetic for an appendectomy. The level of a spinal anesthesia necessary for an appendectomy is T4, which is quiet high. And, a common complication of spinal anesthesia is “spinal headache.”


Clinical Pearls
➤ An appendectomy is a surgical emergency.
➤ A rapid sequence induction is generally used for patients undergoing anesthesia for emergency surgery, as this is thought to reduce the risk of pulmonary aspiration of gastric contents.
➤ The patient’s hemodynamic status should be taken into account when choosing an induction agent. Patients who appear to be septic or volume depleted should have appropriate volume resuscitation before the induction of anesthesia.
➤ Adequate pain control prior to emergence and in the postoperative period has many advantages and is the hallmark of an appropriate anesthetic plan.

References

Fengler BT. Should etomidate be used for rapid-sequence intubation induction in critically ill septic patients? Am J of Emerge Med. 2008;26:229-232. 

Hurford WE, Bailin MT, Davison JK, et al., eds. Clinical Anesthesia Procedures of the Massachusetts General Hospital. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2002:174-175, 293, 573-574. 

Jackson WL. Should we use etomidate as an induction agent for endotracheal intubation in patients with septic shock?: A critical appraisal. Chest. 2005; 127:1031- 1038. 

Jaffe RA, Samuels SI, eds. Anesthesiologist’s Manual of Surgical Procedures. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004:407-410, 472-474. 

Lejus C, et al. Randomized, single blinded trial of laparoscopic versus open appendectomy in children: effects on postoperative analgesia. Anesthesiology. 1996;84:801-806.

Mazurek AJ, et al. Rocuronium versus succinylcholine: are they equally effective during rapid sequence induction of anesthesia? Anesthesia and Analgesia. 1998;87:1259-1262. 

Miller RD, et al eds. Miller’s Anesthesia. 6th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2005:1635, 1647, 2456, 2599-2600. 

Sluga M, et al. Rocuronium versus succinylcholine for rapid sequence induction of anesthesia and endotracheal intubation: a prospective, randomized trial in emergent cases. Anesthesia and Analgesia. 2005;101:1356-1361. 

Stoelting RK, Miller RD, eds. Basics of Anesthesia. 5th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2007:180, 575, 581.

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