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Chapter: Clinical Anesthesiology: Perioperative & Critical Care Medicine: Postanesthesia Care

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Routine Recovery

Airway patency, vital signs, oxygenation, and level of consciousness must be assessed immediately upon PACU arrival.

ROUTINE RECOVERY

 

General Anesthesia

 

Airway patency, vital signs, oxygenation, and level of consciousness must be assessed immediately upon PACU arrival. Subsequent blood pressure, heart rate, and respiratory rate measurements are routinely made at least every 5 min for 15 min or until stable, and every 15 min thereafter. Pulse oximetry should be monitored continuously in all patients. The occurrence of hypoxemia does not necessarily correlate with the level of consciousness. Neuromuscular function should be assessed clini-cally (eg, head-lift and grip strength). At least one temperature measurement must also be obtained. Additional monitoring includes pain assessment (eg, numerical or descriptive scales); the presence or absence of nausea or vomiting; and fluid input and output, including urine flow, drainage, and bleed-ing. After initial vital signs have been recorded, the anesthesia provider should give a brief report to the PACU nurse that includes (1) the preoperative his-tory (including mental status and any communica-tion problems, such as language barriers, deafness, blindness, or mental disability); (2) pertinent intra-operative events (type of anesthesia, the surgical procedure, blood loss, fluid replacement, antibiotic and other relevant medication administration, and any complications); (3) expected postoperative problems; (4) anticipated need for PACU medica-tion administration, such as antibiotics; and (5) postanesthesia orders (analgesia and nausea/vom-iting therapy; epidural or perineural catheter care; including the need for acute pain service involve-ment, administration of fluids or blood products, postoperative ventilation, chest x-ray for follow-up of central venous catheterization, etc.).All patients recovering from general anesthe-sia must receive supplemental oxygen and pulse oximetry monitoring during emergence because transient hypoxemia can develop even in healthy patients. A rational decision regarding continuation of supplemental oxygen therapy at the time of PACUdischarge can be made based on Spo2 readings on room air. Arterial blood gas measurements maybe obtained to confirm abnormal oximetry read-ings, but are not necessary in most patients. Oxygen therapy should be carefully controlled in patients with chronic obstructive pulmonary disease and ahistory of, or potential for, CO 2 retention. Patients should generally be nursed in the back-up position, whenever possible, to optimize oxygenation. However, elevating the head of the bed before the patient is responsive can lead to airway obstruction. In such cases, the oral or nasal airway should be left in place until the patient is awake and able to main-tain airway. Deep breathing and coughing should be encouraged periodically.

Regional Anesthesia

 

Patients who are heavily sedated or hemodynami-cally unstable following regional anesthesia should also receive supplemental oxygen in the PACU. Sensory and motor levels should be periodically recorded following regional anesthesia to document regression of the block. Precautions in the form of padding or repeated warning may be necessary to prevent self-injury from uncoordinated arm move-ments following brachial plexus blocks. Blood pres-sure should be closely monitored following spinal and epidural anesthesia. Bladder catheterization may be necessary in patients who have had spinal or epidural anesthesia for longer than 4 hr.

 

Pain Control

 

Moderate to severe postoperative pain is most commonly treated with oral or parenteral opioids. However, perioperative opioid administration is associated with side effects (nausea and vomit-ing, respiratory depression, pruritis, ileus, and uri-nary retention) which may have significant adverse effects on postoperative convalescence. In response to this problem, a variety of opioid sparing strategies have been increasingly embraced over the past two decades to decrease opioid requirements, and thus opioid-related side effects, while maintaining satis-factory analgesia . Preoperative oral administration of nonsteroidal antiinflammatory drugs (NSAIDs), acetaminophen, and gabapentin or pregabalin may significantly reduce postoperative opioid requirements, and these medications may be resumed postoperatively if the patient can continue oral medication. Additional analgesic modalities utilizing local anesthetics, such as intraoperative wound infiltration, postoperative wound catheter infusions, single-shot and continuous catheter peripheral nerve blocks, and continuous epidural infusions, also reduce postoperative opioid analgesic requirements, and thus also reduce opioid-related side effects.

 

Mild to moderate postoperative pain can be treated orally with acetaminophen, ibuprofen, hydrocodone, or oxycodone. Alternatively, ketorolac tromethamine (15–30 mg in adults) or acetamino-phen (15 mg/kg, or 1 g if patient >50 kg) may be administered intravenously.

 

Insituations where moderate to severe postop-erative pain is present, or oral analgesia is not possi-ble, parenteral or intraspinal opioids, single-shot or continuous nerve blocks, and continuous epidural analgesia are used, often in combination techniques. Parenteral opioids are most safely administered by titration of small doses. Considerable variability in opioid requirements should be expected in surgi-cal patients recovering in the PACU, and adequate analgesia must be balanced against the risk of exces-sive sedation and respiratory depression. Opioids of intermediate to long duration, such as hydro-morphone 0.25–0.5 mg (0.015–0.02 mg/kg in chil-dren) or morphine 2–4 mg (0.025–0.05 mg/kg in children), are most commonly used. Meperidine is most often used in small doses to treat postoperative shivering. Opioid requirements are often markedly increased in patients with a history of chronic pain and chronic opioid therapy, because of opioid toler-ance, and in patients with a history of opioid addic-tion, because of opioid tolerance and psychological dependence. Consultation with a pain specialist is often extremely helpful in these situations.

 

Analgesic effects of parenteral opioids usually peak within minutes of administration. Maximal respiratory depression, particularly with morphine and hydromorphone, may not occur until 20–30 min later. When the patient is fully awake, patient-controlled analgesia can be instituted for inpatients. Intramuscular administration of opioids is discour-aged because delayed and variable onset (10–20 min or longer) and delayed respiratory depression (up to 1 h).

When an epidural catheter is used, epidural bolus administration of fentanyl (50–100 mcg) or sufentanil (20–30 mcg) with 5–10 mL of 0.1% bupi-vacaine can provide excellent pain relief in adults. Epidural morphine (3–5 mg) may also be used, but delayed respiratory depression with epidural admin-istration of this opioid mandates close monitoring for 24 hr afterward .

 

Agitation

 

Before the recovering patient is fully respon-sive, pain is often manifested as postoperativerestlessness. Serious systemic disturbances (such as hypoxemia, respiratory or metabolic acidosis, or hypotension), bladder distention, or a surgical complication (such as occult intraabdominal hem-orrhage) must also be considered in the differential diagnosis of postoperative agitation. Marked agita-tion may necessitate arm and leg restraints to avoid self-injury, particularly in children. When serious physiological disturbances have been excluded in children, cuddling and kind words from a sympa-thetic attendant or the parents often calms the pedi-atric patient. Other contributory factors include marked preoperative anxiety and fear, as well as adverse drug effects (large doses of central anticho-linergic agents, phenothiazines, or ketamine). Phy-sostigmine 1–2 mg intravenously (0.05 mg/kg in children) is most effective in treating delirium due to atropine and scopolamine. If serious systemic disturbances and pain are excluded, persistent agita-tion may require sedation with intermittent intrave-nous doses of midazolam 0.5–1 mg (0.05 mg/kg in children).

 

Nausea & Vomiting

 

Postoperative nausea and vomiting (PONV) is com-mon following general anesthesia, occurring in 30% to 40% of all patients. Moreover, PONV occurs at


home within 24 hr of an uneventful discharge (post-discharge nausea and vomiting) in a significant number of ambulatory surgery patients. The etiol-ogy of PONV is usually multifactorial and associ-ated with anesthetic and analgesic agents, the type of surgical procedure, and intrinsic patient factors, such as a history of motion sickness. It is also impor-tant to recognize that nausea is a common complaint reported at the onset of hypotension, particularly following spinal or epidural anesthesia.

 

Table 56–1 lists commonly recognized riskfactors for PONV. An increasedincidenceofnauseaand vomiting is reported following opioid adminis-tration and intraperitoneal (especially laparoscopic), breast, and strabismus surgery. The greatest inci-dence seems to be in young women; nausea may be more common during menstruation. Increased vagal tone manifested as sudden bradycardia com-monly precedes, or coincides with, emesis. Propo-fol anesthesia decreases the incidence of PONV, and a preoperative history of smoking lessens the likelihood of PONV. Selective 5-hydroxytryptamine

(serotonin) receptor 3 (5-HT 3) antagonists, such as ondansetron 4 mg (0.1 mg/kg in children), granisetron 0.01–0.04 mg/kg, and dolasetron 12.5 mg (0.035 mg/kg in children), are effective in preventing PONV, and, to a lesser extent, in treating established PONV. It should be noted that unlike ondansetron, which is usually effective immediately, dolasetron requires 15 min for onset. An orally disintegrating tablet preparation of ondansetron (8 mg) may be useful for treatment and prophylaxis against post-discharge nausea and vomiting. Metoclopramide, 0.15 mg/kg intravenously, is a less effective alternative to 5-HT3 antagonists. 5-HT3 antagonists are not associated with the acute extrapyramidal (dystonic)manifestations and dysphoric reactions that may be encountered with metoclopramide or phenothi-azine-type antiemetics. Transdermal scopolamine is effective, but can be associated with side effects, such as sedation, dysphoria, blurred vision, dry mouth, urinary retention, and exacerbation of glaucoma, particularly in elderly patients. Dexamethasone 4–10 mg (0.10 mg/kg in children), when utilized as an antiemetic, has the additional advantages of pro-viding a varying degree of analgesia and a sense of patient well-being. Moreover, it seems to be effec-tive for up to 24 hr, and, thus, may be useful for postdischarge nausea and vomiting. Oral aprepitant (Emend®) 40 mg may be administered within 3 hr prior to anesthesia induction. Intravenous droperi-dol 0.625–1.25 mg (0.05–0.075 mg/kg in children), when given intraoperatively, significantly decreases the likelihood of PONV. Unfortunately, droperidol carries a US Food and Drug Administration “black box” warning, indicating that large (5–15 mg) doses can prolong the QT interval and have been associ-ated with fatal cardiac arrhythmias. Nonpharmaco-logical prophylaxis against PONV includes ensuring adequate hydration (20 mL/kg) after fasting, and stimulation of the P6 acupuncture point (wrist). The latter may include application of pressure, electrical current, or injections.

Controversy exists regarding routine PONV prophylaxis for all patients. Because of the cost of treatment of established PONV, it may be cost-effective to provide prophylaxis to all patients in cer-tain populations (eg, outpatients). Clearly, patients with multiple risk factors should receive prophy-laxis. In addition, the use of two or three agents that act on differing receptors is more effective than sin-gle-agent prophylaxis.

Shivering & Hypothermia

 

Shivering can occur in the PACU as a result of intra-operative hypothermia or the effects of anesthetic agents, and it is also common in the immediate post-partum period. The most important cause of hypo-thermia is a redistribution of heat from the body core to the peripheral compartments. A relatively cool ambient operating room temperature, prolonged exposure of a large wound, and the use of large amounts of unwarmed intravenous fluids or high flows of unhumidified gases can also be con-tributory. Nearly all anesthetics, particularly volatile agents and spinal and epidural anesthesia, decrease the normal vasoconstrictive response to hypother-mia by decreasing sympathetic tone. Although anes-thetic agents also decrease the shivering threshold, shivering commonly observed during or after emer-gence from general anesthesia represents the body’s effort to increase heat production and raise body temperature and may be associated with intense vasoconstriction. Emergence from even brief gen-eral anesthesia is sometimes also associated with shivering, and although the shivering can be one of several nonspecific neurological signs (postur-ing, clonus, or Babinski’s sign) that are sometimes observed during emergence, it is most often due to hypothermia. Regardless of the mechanism, its inci-dence seems to be related to the duration of surgery and the use of a volatile agent. Shivering may occa-sionally be sufficiently intense to cause hyperther-mia (38–39°C) and significant metabolic acidosis, both of which promptly resolve when the shivering stops. Other causes of shivering should be excluded, such as bacteremia and sepsis, drug allergy, or trans-fusion reaction.

Hypothermia should be treated with a forced-air warming device, or (less satisfactorily) with warming lights or heating blankets, to raise body temperatureto normal. Intense shivering causes precipitous rises in oxygen consumption, CO2 production,and cardiac output. These physiological effects are often poorly tolerated by patients with pre-existing cardiac or pulmonary impairment. Hypothermia has been associated with an increased incidence of myo-cardial ischemia, arrhythmias, increased transfusion requirements due to coagulopathy, and increased duration of muscle relaxant effects. Small intravenous doses of meperidine (10–25 mg) can dramatically reduce or even stop shivering. Intubated and mechan-ically ventilated patients can also be sedated and given a muscle relaxant until normothermia is rees-tablished by active rewarming and the effects of anes-thesia have dissipated.

Discharge Criteria

A. PACU

 

All patients must be evaluated by a qualified anes-thesia provider prior to discharge from the PACU unless strict discharge criteria are adopted. Stan-dards for discharging patients from the PACU are established by the department of anesthesiology and the hospital medical staff. They may allow PACU nurses to determine when patients may be trans-ferred without the presence of a qualified anes-thesia provider if all PACU discharge criteria have been met. Criteria can vary according to whether the patient is going to be discharged to an intensive care unit, a regular ward, the outpatient department (phase 2 recovery), or directly home.

 

Before discharge, patients should have been observed for respiratory depression for at least 20–30 min after the last dose of parenteral opioid. Other minimum discharge criteria for patients recovering from general anesthesia usually include the following:

 

·        Easy arousability

 

·        Full orientation

 

·        The ability to maintain and protect the airway

 

·        Stable vital signs for at least 15–30 min

 

·        The ability to call for help, if necessary

 

·        No obvious surgical complications (such as active bleeding)

 

Postoperative pain and nausea and vomiting must be controlled, and normothermia should be reestablished prior to PACU discharge. Scoring sys-tems are widely used. Most assess Spo2 (or color),


consciousness, circulation, respiration, and motor activity (Table 56–2). The majority of patients can meet discharge criteria within 60 min from the time of PACU arrival. Patients to be transferred to other intensive care areas need not meet all requirements.

In addition to the above criteria, patients receiv-ing regional anesthesia should also be assessed for regression of both sensory and motor block-ade. Complete resolution of the block prior to PACU dismissal avoids inadvertent injuries due to motor weakness or sensory deficits; however,

many institutions have protocols that allow earlier discharge to appropriately monitored areas, and patients may be discharged with peripheral nerve blocks from single-shot or continuous perineural catheter infusions for the purpose of regional anal-gesia. Documenting regression of a block is impor-tant. Failure of a spinal or epidural block to resolve 6 hr after the last dose of local anesthetic raises the possibility of spinal subdural or epidural hematoma, which should be excluded by prompt radiological imaging and neurologic evaluation.

 

In some centers, outpatients who meet the above discharge criteria when they come out of the operating room may be “fast-tracked,” bypassing the PACU and proceeding directly to the phase 2 recov-ery area. Similarly, inpatients who meet the same criteria may be transferred directly from the operat-ing room to their ward, if appropriate staffing and monitoring is present.

B. Outpatients

 

In addition to emergence and awakening, recovery from anesthesia following outpatient procedures includes two additional stages: home readiness (phase 2 recovery) and complete psychomotor recovery. A scoring system has been developed to help assess home readiness discharge (Table 56–3). Recovery of proprioception, sympathetic tone, blad-der function, and motor strength are additional crite-ria following regional anesthesia. For example, intact proprioception of the big toe, minimal orthostatic blood pressure and heart rate changes, and normal plantar flexion of the foot are important signals of recovery following spinal anesthesia. Urination and drinking or eating before discharge are usually no longer required; exceptions include patients with a history of urinary retention and those with diabetes.

 

All outpatients must be discharged home in the company of a responsible adult who will stay with them overnight (the latter is required if they have received an anesthetic). Patients must be provided with written postoperative instructions on how to obtain emergency help and to perform routine follow-up care. The assessment of home readiness is the responsibility of the qualified anesthesia pro-vider, preferably one who is already familiar with the patient, although authority to discharge a patient


home can be delegated to a nurse, if approved dis-charge criteria are applied.

 

Home readiness does not imply that the patient has the ability to make important decisions, to drive, or to return to work. These activities require complete psychomotor recovery, which is often not achieved until 24–72 hr postoperatively. All outpa-tient centers must use some system of postoperative follow-up, preferably phone contact the day after discharge.

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