Page 1542 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 112: Principles of Postoperative Critical Care 1061

postoperative and trauma patients is similar to nonsurgical critically ill management and monitoring. If not, then conditions such as sepsis,
patients. This chapter is designed to assist in specific postoperative and shock, and encephalopathy should be considered. In these patients, deci-
trauma situations not covered elsewhere in this textbook. sions regarding extubation can be difficult.
Patients returning from the operating room frequently have moder-
IMMEDIATE POSTANESTHESIA CARE ate to severe hypothermia. The causes are multifactorial and include IV
■ EMERGENCE fluids and blood products that are not warmed prior to infusion, cool air
temperature for operating personnel comfort, vasodilation from the use
When a patient presents to the ICU following surgery, they are of volatile anesthetics, large open wounds and raw surfaces, and evapo-
unresponsive because of a variety of medications, including volatile ration. Although there may be times when hypothermia is useful, for
anesthetics, benzodiazepines, narcotics, and neuromuscular blockers. example, post-cardiac arrest or anoxic brain injury, the majority of post-
3
Volatile anesthetics tend to dissipate quickly but can maintain their operative patients should be returned to normothermia. Postoperative
effects for 20 to 60 minutes postoperatively. The speed of emergence is hypothermia has been shown to worsen coagulopathy, increase transfu-
directly proportional to alveolar ventilation, but inversely proportionate sion requirements, increase susceptibility to infection, increase risk of
4
to solubility of the agent within the blood. The longer the anesthesia cardiac ischemia, and increase shivering and overall discomfort. The
time, the more total tissue uptake occurs, which can affect the duration goal should be rewarming during emergence and on presentation to
of time it takes to emerge from the anesthesia. Recovery is generally fast- the ICU. Forced-air rewarming devices should be used to normalize
est with desflurane and nitrous oxide and slowest with isoflurane. If the temperature (36°C) and reduce shivering, in order to reduce the risk of
patient has been hypoventilated during and after the surgery, this may further complications. 5
diazepines have variable duration of action depending on the amount ■ POSTOPERATIVE EXTUBATION
also lead to delayed emergence from anesthesia. Narcotics and benzo-
administered during surgery. Recovery from intravenous anesthetics is In the immediate postoperative period, many patients can be extubated
6,7
mainly dependent on redistribution rather than the elimination half- quickly following surgery. However, several factors in addition to
life of the drug. As the total dose administered during an anesthetic anesthetic reversal need to be considered prior to extubation including
application increases, cumulative effects become apparent and lead to plans to return to the operating room in the near future, ongoing bleed-
prolonged emergence; the half-life will become more involved in the ing, inadequate resuscitation, or severe metabolic acidosis. The overall
duration of emergence. Propofol and remifentanil lead to the short- ease of intubation and any complications during the initial intubation
est emergence time. Advanced age, renal impairment, and/or hepatic should also be considered. Patients with neurological damage who are
disease can all affect duration of action of IV anesthetics. An adequate unable to follow commands and/or have an absent gag and cough reflex
amount of time should be given for these to wear off before becoming suffer increased rates of reintubation and increased risks of morbidity. If
unduly concerned about mental status. The anesthetic record is an excel- patients are unable to be extubated within the immediate postoperative
lent source, as well as the verbal report from the anesthesia team, which period, daily reassessment should be performed. Assessments of physi-
is imperative to obtain on patient arrival to the ICU. ologic reserve are paramount to ensure successful extubation. Patients
Neuromuscular blockade can have prolonged duration of action should breathe without mechanical assistance to allow assessment of
in some cases and should be considered when a patient is unable to respiratory rate, vital signs stability, end-tidal carbon dioxide levels,
move adequately or cannot hold up the head for 10 seconds. In some and comfort. If trauma is involved, especially in the case of chest wall
instances, a false sense that the blockade has worn off can be seen and, damage, assessment of coordination of the chest wall with the respira-
following extubation, the patient has difficulty maintaining ventilation tory pattern is important, as is ability to control pain.
determining whether paralysis has been completely reversed. If paraly- ■ MALIGNANT HYPERTHERMIA
without assistance. A train-of-four twitch monitor should be used in
sis is persistent, neostigmine (0.5-2 mg) and glycopyrrolate can be used Malignant hyperthermia (MH) was first reported in 1962 after
to reverse the action of the neuromuscular blockers. The diaphragm Denborough described a series of anesthetic deaths within a par-
has been shown to be the most resistant skeletal muscle with regard ticular family. MH is a hypermetabolic crisis that is induced by certain
to effects from neuromuscular blockade. It also tends to be the first to anesthetic agents, including succinylcholine, sevoflurane, isoflurane,
recover. Patients who were able to hold either their head or leg up for desflurane, and halothane. A familial relationship does seem to exist but
5 seconds in a study by Pavlon were able to perform all airway- is not a reliable indicator. The overall incidence is rare—approximately
protection tests necessary for postoperative extubation. 1 in 15,000 patients. Approximately 50% of those who experience an
1
Delayed emergence can occur because of several reasons, the most MH crisis have had a previous anesthetic agent without complication.
common being residual anesthetic, sedative, and analgesic drug effects. The frequency is reduced in women and patients older than 50. Pediatric
Emergence can also be delayed by electrolyte abnormalities such as patients and those with musculoskeletal disorders including myotonia,
hyperglycemia and hyponatremia. Use of other sedating or interacting osteogenesis imperfecta, King-Denborough syndrome, and Duchenne
agents such as alcohol or recreational drugs prior to anesthesia may muscular dystrophy have the highest prevalence. In addition, certain
also contribute. If the length of emergence becomes prolonged, then surgical procedures have also associated with an increased risk including
naloxone in 0.04 mg increments and/or flumazenil in 0.2 mg increments repair of cleft palate, tonsillectomy and adenoidectomy, repair of ptosis,
can be given to rule out opioid or benzodiazepine effects, respectively. 1 strabismus correction, and orthopedic procedures. Unrecognized MH
1
Patients may become restless before they are fully responsive or they carries an approximately 80% mortality, while treated aggressively, the
may experience disorientation, anxiety, and pain. Generally, this is self- mortality rate is only 10%.
limited; however, hypoxemia, acidosis, hypotension, bladder distention, The earliest indication that an MH crisis is developing is an increase
or other complications should be considered and evaluated. Despite this in end-tidal carbon dioxide levels. Fever, tachycardia, tachypnea, and
restlessness, it is usually possible to have patients follow commands and rigidity of the masseter muscle (trismus) will generally develop in
participate in working toward extubation. Small doses of narcotics and/ patients. Patients will then quickly become unstable if not aggressively
or benzodiazepines may be necessary to help relax the patient enough treated; further symptoms and findings will include hypotension, cyano-
to avoid self-harm, self-extubation, or other complications. This usually sis, cardiac arrhythmias, and severe hyperpyrexia. As the crisis develops,
can be accomplished without causing further sedation. Generally, the temperature may raise as much as 1°C to 2°C every 5 minutes. 8
2
use of low-dose fentanyl or morphine for pain and/or 0.5 to 1 mg of The hallmark treatment of MH is dantrolene, which was specifically
midazolam intermittently can control agitation. In most cases, agitation developed to treat the condition. Dantrolene is a skeletal muscle relaxant
or somnolence should improve within 30 to 60 minutes with appropriate that must be administered intravenously. It comes in powder form and

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