MANAGEMENT OF THE PATIENT AT HIGH RISK E O

MANAGEMENT OF THE PATIENT AT HIGH RISK
FOR POSTOPERATIVE NAUSEA AND VOMITING
ETHAN OLIVER BRYSON*, ELIZABETH A.M. F ROST**
***
AND M EG R OSENBLATT
Abstract
Postoperative nausea and vomiting continue to be problematic areas
in anesthesia as evidenced by frequent reports of therapies in the
literature. No single therapy has been proven curative for all cases, in part
because of the several emetic centers, all of which may be blocked by
different classes of drugs and the diverse risk factors which act alone or in
combination to cause vomiting. Identification of the patient most at risk
allows for cost effective prophylactic management. An appropriate
anesthetic technique can be planned that, relying on evidence based
medicine, will decrease if not prevent the incidence of this most troubling
complication.
Introduction
The incidence of postoperative nausea and vomiting (PONV) is
reported between 18% and 30% in most large series regardless of location
or patient population1 but these figures include nausea without emesis and
no distinction is made between mild and severe vomiting. The actual
incidence of severe incapacitating vomiting remains steady, at about 0.1%
to 0.6% of all anesthetics performed2. Given the prevalence of PONV, the
From the Department of Anesthesiology, Mount Sinai Medical Center, New York, NY, USA.
* MD Senior Resident in Anesthesiology.
**MD Professor.
*** MD Associate Professor.
15
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ETHAN OLIVER BRYSON ET AL
possibility that any patient could develop nausea and or vomiting
requiring postoperative treatment, must be considered during
preanesthetic assessment to allow development of a preemptive plan.
Preanesthetic Assessment
The preanesthetic interview should cover questions designed to
determine the patient’s risk for developing PONV, and the
anesthesiologist should consider the many variables (see Table 1) in
formulating a perioperative plan. The overall risk that a particular patient
will develop PONV depends upon factors unique to the patient, the
surgical procedure, and the anesthetic technique.
Table 1
Several factors have been identified as having
a higher risk for PONV
Patient Factors
 Age
 Gender
 Menstrual status
 Weight
 Smoking status
 History of PONV or
motion sickness
 Fasting status
 Co-morbidities
Surgical Factors
 Type and area of surgery
 Duration of procedure
Anesthetic Factors
 Use of nitrous oxide
 Use of potent inhaled agents
 Use of opioids
Patient Factors Associated with PONV
Patient age has been shown to be a contributing factor in the
development of PONV3 with children showing a greater propensity
towards PONV. Among pediatric patients the incidence has been shown
to be as high as 34% in the 6-10 year age group but considerably lower in
younger patients, and the incidence decreases with the onset of puberty4.
Geriatric patients have a much lower incidence.
In adult patients, gender has been shown to have a greater influence
MANAGEMENT OF THE PATIENT AT HIGH RISK FOR POSTOPERATIVE NAUSEA AND VOMITING
17
on the development of PONV than age, with premenopausal women and
postmenopausal women less than 60 years of age, more susceptible than
men5. This gender difference is not observed in the pediatric population
or in adults older than 60 years of age and consequently the etiology is
thought, by some, to involve variations in serum gonadotropins6. Several
studies have noted differences in the incidence of PONV experienced by
women at different stages in the ovulatory cycle, with menstruation and
the pre-ovulatory phase increasing the risk6. A premenopusal woman in
the immediate pre-menstrual phase of her cycle is at greater risk for
developing PONV than a male of the same age undergoing the same
procedure or, presumably a comparable female at a different stage in her
cycle.
Whether or not weight alone is an independent risk factor for the
development of PONV remains controversial. Several studies have
suggested that patient weight is associated with the risk for development
of PONV with obesity, defined by a body mass index (BMI) of greater
than 30, increasing the risk7. A number of factors have been suggested as
to why this correlation exists, including the potential for air to be forced
into the stomach during the handling of a difficult airway, as may be
encountered in the obese patient, the larger percentage of body fat in
which fat soluble anesthetic agents can be stored and delayed gastric
emptying8. More recently, however, a systematic review of available data
by Kranke et al suggests that BMI is not correlated with an increased risk
for the development of PONV9. An increased BMI may increase the
incidence of PONV in patients with other independent risk factors. Body
mass index is calculated by dividing weight in kilograms by height in
meters squared.
A number of conditions that may or may not be related to the surgery
have been identified as risk factors. Patients deemed to have a “full
stomach” and who are not fasting are at greater risk of regurgitation. Co
morbidities such as gastroesophageal reflux disease, hiatal hernia, liver
disease, and gastroparesis with associated decreased gastric motility and
delayed gastric emptying are some examples10. Gastroparesis and ileus are
commonly associated with opioid administration as part of an anesthetic
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ETHAN OLIVER BRYSON ET AL
regimen but may also be secondary to diabetes mellitus or a number of
other medical conditions, including scleroderma and amyloidosis11. Anxiety
is known to reduce the pH of gastric fluid and increase its volume, making
the patient more likely to develop PONV10 but depression without
associated anxiety has not been identified as a risk factor.
The patient factor most closely associated with an increased risk for
developing PONV is a prior history of the complication or a propensity to
motion sickness12. These patients may have a well-developed vomiting
reflex arc but the exact mechanism is unclear. Also, for reasons that are
not understood, smoking, appears to confer a preventive effect.
Surgical Factors Associated with PONV
Some surgical procedures are more likely to cause PONV than
others, even in patients not otherwise at risk, and independent of the
anesthetic agents used13. Surgical operations that have been linked to a
higher incidence of PONV include gynecologic or general abdominal
procedures, head and neck surgery, eye surgery, and laparoscopic
procedures in general. The duration of surgical procedure also affects the
incidence of PONV, independent of other factors, with a longer duration
of procedure positively correlated with a greater likelihood of the
development of PONV13. Increasing the duration by 30 minutes may
increase the risk of PONV by 60%.
Anesthetic Factors Associated with PONV
Nausea, vomiting and retching can occur after general or spinal and
epidural anesthesia, peripheral nerve blocks, and even after monitored
anesthesia care cases. While the patient and surgical factors noted above
cannot be controlled by the anesthesiologist, there are a number of
decisions that can be made and techniques employed to reduce the
incidence of PONV in patients art risk. Factors under the control of the
anesthesiologist are divided into preoperative, intraoperative, and
postoperative factors.
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Preoperative factors
Several agents used preoperatively have been shown to affect the
incidence of PONV. Benzodiazepines such as midazolam, often used as
premedication to reduce anxiety and produce amnesia, appear to decrease
the incidence of PONV14. A similar beneficial effect is seen when the
alpha agonist clonidine is used for preoperative sedation15. Premedication
with opioids increases the incidence of PONV16 but when pain is a factor,
the relief of pain pre-operatively is associated with less PONV3. Agents
used as preoperative vagolytics and antisialagogues such as atropine and
glycopyrrolate have been associated with an increased incidence of
PONV, but it appears that atropine may be considerably less emetogenic
than glycopyrrolate17. Agents such as metoclopramide, which promote
gastric empyting, may result in a decreased incidence of PONV, likely
due to decreased gastric volume17.
Intraoperative agents
While the potent anesthetic agents used for the maintenance of
general anesthesia today do not result in the near 100% rate of PONV
observed with cyclopropane and ether, they are associated with an
elevation in the incidence of PONV, with a direct correlation between
length of exposure and dosage18. Nitrous oxide increases PONV, and
omission of this gas from the anesthetic regime, especially in patients at
risk, significantly reduces episodes of PONV19. All of the volatile
anesthetic agents, however, have been shown to cause vomiting and there
are no statistical differences between the emetogenicity of halothane,
enflurane, isoflurane, sevoflurane, or desflurane, even when used at or
below 1 MAC18. The technique of pure inhaled anesthesia, using the
potent inhaled agents with or without nitrous oxide and not
supplementing with opioid analgesics, is less emetogenic than the more
commonly used balance technique in which intravenous opioids
combined with N2O are used, but is associated with a significantly higher
incidence of PONV than total intravenous anesthesia (TIVA) with
propofol and no N2O20. When propofol is substituted for the inhaled
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ETHAN OLIVER BRYSON ET AL
agents, the incidence of PONV is reduced by about 20%18.
Intravenous agents used intraoperatively have also been associated
with PONV, both positively and negatively. Propofol has been shown to
reduce the incidence of PONV when used for induction or maintenance of
general anesthesia, though a single induction dose does not reduce the
incidence of PONV if the case is long and propofol is not used for
maintenance21. When etomidate or ketamine is used for induction of
anesthesia an increase in the incidence of PONV is observed22, though the
residual effects of ketamine may have a benefit in the reduction of
postoperative pain and the reduced need for postoperative narcotics, both
of which contribute to a decreased incidence of PONV23. Induction of
general anesthesia with barbiturates such as sodium thiopental has not
been shown to affect PONV but studies which looked at TIVA with
barbiturates showed a level of PONV greater than that observed with
propofol24. Reversal of residual neuromuscular blockade with
cholinesterase inhibitors can increase the incidence of PONV25, however
some studies have suggested that the emetic effect can be lessened by
substituting atropine for glycopyrrolate26.
Management of the airway during positive pressure ventilation,
either during induction and prior to intubation, or intraoperatively, such
as might occur during mask ventilation or after placement of a
Laryngeal Mask Airway®, can result in the distension of the stomach
and increase the incidence of PONV. One study suggests that care of
the airway by inexperienced persons increases the incidence of PONV 27
while another study points out that the incidence of PONV may not be
lessened by the routine emptying of gastric contents via an orogastric
tube 28, although this technique is commonly used at the end of a case in
patients at high risk.
The use of regional anesthesia may reduce the incidence of PONV in
patients at risk by avoiding general anesthesia and the need for opioids to
control pain. When a long acting agent is used, significant postoperative
analgesia can be provided with a single injection. The placement of an
epidural or peripheral nerve catheter allows continuous infusion of a local
anesthetic, extending the period of postoperative analgesia and reducing
MANAGEMENT OF THE PATIENT AT HIGH RISK FOR POSTOPERATIVE NAUSEA AND VOMITING
21
or eliminating the need for systemic opioids. Opioids infused with the
local anesthetic through the catheter are absorbed systemically and have
the potential to contribute to PONV. Though considerably less likely to
cause PONV, the techniques are not entirely without increased risk, and if
the regional technique fails, general anesthesia may be necessary29.
Hypotension may result from neuraxial anesthesia with spinal and
epidural placement and increase the incidence of nausea and vomiting,
both intra and postoperatively. The impact of this vascular perturbation
can be lessened by prehydration prior to neuraxial block and maintenance
of blood pressure with vasoactive agents as necessary, or by using a
peripheral nerve block when appropriate30.
The technique of monitored anesthesia care, the use of local
anesthesia with sedation and monitoring by an anesthesiologist, can be
used for many procedures, and is associated with a decrease in the
incidence of PONV, especially when propofol is used31. If opioids are
used as analgesic adjuncts, the incidence of PONV is increased, as would
be expected. However, the use of nonsteroidal anti-inflammatory drugs
(NSAIDS) such as ketorolac (Toradol®) can reduce the need for opioids
and therefore avoid the increased incidence of PONV. Also, a multimodal
approach combining reduced dosages of narcotics and NSAIDs allows
potentiation of analgesic effect and decreased severity of complications
from both groups.
Postoperative factors
Once the patient has emerged from anesthesia, an number of factors
can influence the incidence of PONV. Postoperative pain and the method
of pain control employed, dizziness and disorientation, early ambulation
and oral intake, and hydration all play a role in determining the onset and
severity of PONV.
Pain itself is emetogenic and a well recognized causative factor of
PONV3, but the treatment of postoperative pain with opioids can increase
PONV, so much that some patients opt to forgo pain management to
avoid the associated malaise32. Direct stimulation of the chemoreceptor
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ETHAN OLIVER BRYSON ET AL
trigger zone and vestibular apparatus as well as the decreased gastric
emptying and bowel atony caused by all opioids used for postoperative
analgesia make selection of effective pain management difficult at best.
Strategies that lessen the dose of opioids used such as patient controlled
analgesia (PCA) and supplementation with non-narcotic analgesic agents
are associated with a decreased risk33. Patient controlled epidural
anesthesia (PCEA) and continuous epidural nerve blocks which rely on
local anesthetics alone, avoid the administration of emetogenic agents
while also controlling postoperative pain. Yet another means to reduce
the adverse gastrointestinal effects associated with the administration of
opioids may come in the development of specific  opioid receptor
antagonists which do not cross the blood brain barrier and thus preserve
the analgesic actions but prevent bowel atony. Such agents including
methylnaltrexone and alvimopam are currently under investigation.
Residual anesthetic effects in the immediate postoperative period
may contribute to dizziness and disorientation and increase the incidence
of PONV, an effect exacerbated by hypovolemia, anemia, hypoxia, or
opioids administered for postoperative pain control3. Early ambulation or
movement can trigger an episode of PONV and some anesthesiologists
suggest that patients with a history of PONV should restrict their
movements postoperatively if possible34. Hypovolemia can be avoided
with the liberal administration of fluids intraoperatively and such
treatment has been shown to reduce the incidence of dizziness but has not
been shown to affect the incidence of PONV34. Many patients who
develop PONV do so after their first postoperative oral intake; therefore it
is not currently recommended to mandate that patients demonstrate ability
to drink without vomiting before being discharged from the postanesthesia care unit. However, there are studies suggesting that restricting
oral intake does not reduce the incidence of PONV35.
Prevention and Treatment of PONV
Despite the relatively high overall incidence of PONV, most
afflicted patients have minimal nausea associated with a small number of
MANAGEMENT OF THE PATIENT AT HIGH RISK FOR POSTOPERATIVE NAUSEA AND VOMITING
23
emetic episodes, so the routine use of antiemetic prophylaxis is neither
indicated nor cost-effective36. Commonly seen side effects of antiemetic
prophylaxis range in severity from dry mouth, blurry vision, and headache
to dysphoria, sedation, and extrapyramidal symptoms. Given the potential
for harmful side effects if patients are treated empirically, a rationale for
prophylactic care must be developed. Because patients at high risk for
developing PONV are also at higher risk for developing intractable
PONV requiring repeated doses of rescue medications and unplanned
postoperative hospital admission, the risks of prophylaxis in this group
are considerably less than the risks associated with no treatment37. Since
side effects from commonly used prophylactic agents can require
intervention and result in a prolonged stay in the post anesthetic care unit
or an unplanned hospital admission, it is up to the anesthesiologist to
balance the risks of not administering antiemetic prophylaxis with any
untoward effects and identify only those patients who will likely benefit
from prophylactic administration.
Once it has been determined by the anesthesiologist that antiemetic
prophylaxis will be administered, the choice of agent or combination of
agents must be made (see Table 2). The antiemetic agents available work
by different mechanisms at different receptor sites (Figure 1) and have
different pharmacologic profiles and side effects (see Table 3).
Fig. 1
The antiemetic
drugs have
different sites of
actions, thus
explaining why
single drug
therapy may not
be effective.
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ETHAN OLIVER BRYSON ET AL
Table 2
Agents Used for PONV Prophylaxis(*)
Prophylaxis
Adult Dose
Timing of Dose
 Promethazine
25 mg PO, PR
1 hour prior to induction
12.5-25 mg IV
at the end of surgery
5-15 mg PO
1 hour prior to induction
5-10 mg IV
at the end of surgery
10-25 mg PO
1 hour prior to induction
100 mg PR
1 hour prior to induction
50 mg PO
1 hour prior to induction
10-50 mg IV
after induction
 Hydroxyzine
25-100 mg IM
after induction
 Cyclizine
50 mg IM
after induction
 Scopolamine Patch
1.5 mg transdermal
applied morning of
 Prochlorperazine
 Chlorpromazine
 Diphenhydramine
surgery
 Metoclopramide
10-20 mg IV
after induction
 Dexamethasone
5-10 mg IV
at the end of surgery
 Trimethobenzamide
300 mg PO or
1 hour prior to induction
200 mg PR
 Ondansetron
200-250 mg IV
at the end of surgery
8 mg PO (available as an orally
1 hour prior to induction
disintegrating preparation)
4 mg IV
after induction
 Granisetron
0.1-1.0 mg IV
at the end of surgery
 Droperidol
0.625-1.25 mg IV
at the end of surgery
 Dolasetron
100 mg PO
1 hour prior to induction
12.5 mg IV
at the end of surgery
(*) Dose ranges as per medication package inserts.
MANAGEMENT OF THE PATIENT AT HIGH RISK FOR POSTOPERATIVE NAUSEA AND VOMITING
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Table 3
Antiemetics by class with side effects Adverse effects appear to be specific
to the site of action.
Phenothiazines (promethazine, prochlorperazine, chlorperazine)
 Extraphyramidal effects
 Sedation
 Confusion
 Excitation
Butyrophenones (droperidol)
 Extraphyramidal effects
 Sedation
 Lethargy
 Agitation
Antihistamines (diphenhydramine, hydroxyzine, cyclizine)
 Sedation
Anticholnergies (scopolamine)
 Dry Mouth
 Sedation
 Dysphoria
 Confusion/Disorientation
 Hallucinations/Visual Disturbances
Benzamides (metoclopramide, trimethobenzamide)
 Extrapyramidal effects
 Dystonia
Seratonin Antagonists (ondansetron, granisetron, dolasetron, tropesitron)
 Headache
 Light-Headedness
 Dizziness
 Constipation
Should prophylactic therapy not be effective and breakthrough or
opioid induced PONV occur, then further treatment is indicated, either by
combination therapy or moving to a different class (Table 4).
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ETHAN OLIVER BRYSON ET AL
Table 4
Agents Used in the Treatment of PONV(*)
Treatment
Adult Dose
Pediatric Dose
Frequency
 Promethazine
12.5-25 mg IV
0.25-1 mg/kg PR
single dose
 Prochlorperazine
5-10 mg IV
0.1 mg/kg PR
q12 hrs
 Droperidol
0.625-1.25 mg IV
25-75 mcg/kg IV
single dose
 Diphenhydramine
10-50 mg IV
1 mg/kg IV
q6-8 hrs
 Hydroxyzine
25-100 mg IM
1 mg/kg IV, IM
q6 hrs
 Cyclizine
50 mg IM
1 mg/kg IM
q4-6 hrs
 Scopolamine
0.3-0.65 mg IV, IM
6 mcg/kg IV, IM, SC
q4-6 hrs
 Metoclopramide
10-20 mg IV
0.1-0.25 mg/kg IV
q6 hrs
 Trimethobenzamide
300 mg PO, IV
100 mg PR, PO
q6 hrs
200 mg PR
if < 15 kg
(up to 25 mg)
200 mg PR, PO
if > 15 kg
 Ondansetron
1-4 mg IV
0.05-0.1 mg/kg IV
single dose
 Granisetron
0.1-1.0 mg IV
40 mcg/kg IV
single dose
 Dolasetron
12.5 mg IV or
0.35 mg/kg IV
single dose
100 mg PO
(up to 12.5 mg)
(up to 4 mg max)
(*) Dose ranges and timing of doses as per package inserts.
Promethazine (Phenergan®), prochlorperazine (Compazine®), and
chlorpromazine (Thorazine®) are all phenothiazines, thought to exert
their antiemetic effects by directly acting on the central dopaminergic
receptors of the chemoreceptor trigger zone3. These agents are most
effective in the treatment of opioid induced PONV, but their use as the
primary treatment for PONV is limited by their tendency to cause
sedation. Also, these agents have a narrow therapeutic index, and
confusion, excitation, and extraphyramidal effects occur at higher doses.
One study suggests that preoperative treatment with a phenothiazine is as
effective in preventing PONV as newer, more expensive agents, and that
effective prophylaxis can be achieved with lower doses that are
associated with fewer side effects38.
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Droperidol (Inapsine®) is the only butyrophenone currently used in
the treatment of PONV. Like the phenothiazines, droperidol acts
competitively on central dopaminergic receptors and is associated with
sedation, lethargy, agitation and extraphyramidal effects, but the
incidence of the more serious side effects is lower39. Excessive
postoperative sedation is common when patients are given higher doses of
droperidol, and in the past this complication has limited use in outpatient
anesthesia. Recent studies have shown that lower doses are just as
effective in the prevention and treatment of PONV and are associated
with less postoperative sedation. The addition of a “black box” warning to
the droperidol drug information sheet by the FDA has reduced the use of
droperidol, an effective and safe prophylactic agent, to that of rescue
agent for intractable cases of PONV. The concern is that, in some patients
who receive droperidol, a prolonged QTc interval develops, putting these
patients at risk to develop the ventricular arrhythmia, torsade de pointes.
Despite the limited evidence that antiemetic doses trigger this
arrhythmia40 the “black box” warning requiring electrocardiographic
monitoring remains part of the package insert.
Diphenhydramine (Benadryl®), hydroxyzine (Atarax®, Vistaril®),
and cyclizine (Marezine®) are all antihistamines which work to prevent
nausea and vomiting by acting on the H1 receptors. Use as postoperative
agents is limited by the excessive sedation associated with administration.
These agents are most effective in the control of emesis caused by
vestibular stimulation as is seen in patients with motion sickness and after
middle ear surgery. They are rarely effective as a single agent but are
often combined with drugs such as the phenothiazines known to produce
extrapyramidal effects in order to mitigate the severity of these side
effects3.
Scopolamine is an anticholinergic agent that acts on the muscarinic
and histaminic receptors of the vestibular apparatus and the nucleus of the
tractus solitarus to reduce the incidence of PONV. It has been found to be
very effective in patients treated with opioids for post-operative pain
control and after middle ear surgery, though use is limited by a high
incidence of sedation and dry-mouth41. Other troubling side effects
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ETHAN OLIVER BRYSON ET AL
include dysphoria, confusion, disorientation, visual disturbances and
hallucinations3. Some studies have suggested that the efficacy of
scopolamine in the prevention of PONV is no more than that of placebo42,
though recently scopolamine, in the form of a transdermal patch applied
the evening before or the morning of surgery, has been shown to reduce
the incidence of PONV as effectively as ondansetron43. The authors of
this study reported effective PONV prophylaxis in a high risk patient
population by applying the transdermal scopolamine patch the morning of
surgery. The reduced incidence of PONV was achieved with an
insignificant incidence of side effects such as dry mouth but at only 25%
the cost of IV ondansetron incurred by this institution.
Metoclopramide and trimethobenzamide are benzamides that act on
both central dopamine and serotonin receptors, with both prokinetic and
antiemetic effects. Metoclopramide increases gastrointestinal tract
motility, decreasing gastric emptying time and gastric volume, and is
usually well tolerated in adult patients. Side effects seen in this class of
agents include extrapyramidal effects and dystonia, though these actions
are more often seen in the pediatric population. Unlike the other agents
discussed above, metoclopramide is not associated with sedation, making
it a more attractive agent for outpatient treatment or prophylaxis.
However, some studies have suggested that metoclopramide is
considerably less effective than other agents, sedating or not, in the
treatment of established PONV44.
Ondansetron, granisetron, dolasetron, tropisetron and other serotonin
antagonists have been shown to provide effective treatment and
prophylaxis of PONV and are associated with a low incidence of mild
side effects44. These agents are not dopamine, muscarinic or histamine
receptor antagonists, and, as such, are not associated with the side effects
common to those classes. Side effects common to the serotonin
antagonists include headache, light-headedness, dizziness and
constipation. In one study, preoperative ondansetron was shown to be as
useful as droperidol in the prevention and treatment of PONV, though
less cost effective considering that the administration of droperidol was
not associated with an increased length of stay or other adverse side
MANAGEMENT OF THE PATIENT AT HIGH RISK FOR POSTOPERATIVE NAUSEA AND VOMITING
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effects45. Granisetron has also been shown to effectively reduce the
incidence of PONV in patients at risk, including pediatric patients and
menstruating women46.
Agents that do not act directly on receptors known to be involved
with emetogenesis may be effective in reducing the incidence of PONV
indirectly by mitigating symptoms known to be emetogenic. Anxiolytics
such as midazolam, for example, may effectively reduce the nausea and
vomiting that commonly accompanies anxiety. Agents which reduce the
need for opioids, as discussed previously, can be used as prophylaxis in
patients at risk for PONV. Ephedrine and other agents that help maintain
blood pressure may be used to prevent the nausea associated with
hypotension postoperatively3.
The use of single dose steroids as prophylaxis for the prevention of
PONV has become commonplace in many institutions. Dexamethasone,
previously used in combination therapy, has been shown to reduce the
incidence of PONV when used as the sole agent, and is now frequently
used as such47. Several studies have examined the efficacy of this agent in
the context of different types of surgical procedures. A recent randomized
clinical trial found a significant decrease in the incidence of PONV after
laparoscopic cholecystectomy when dexamethasone was administered
preoperatively as the sole antiemetic agent48. Patients receiving
dexamethasone in this study reported no more adverse events than those
who received a placebo, and patients in the dexamethasone group who did
develop PONV were significantly less likely to require rescue
antiemetics.
When used as the sole antiemetic agent for women undergoing
laparoscopic gynecological surgery, dexamethasone was shown to reduce
the incidence of PONV significantly49. The authors of this study
concluded that, given its availability, low cost and few side-effects,
dexamethasone should be more frequently used as the prophylactic
antiemetic in women undergoing gynecologic laparoscopic surgery.
Since pharmacologic interventions have been unable to eliminate
PONV, investigators have looked into the potential benefits of
nonpharmacologic interventions. In one randomized, prospective, doubleM.E.J. ANESTH 19 (1), 2007
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ETHAN OLIVER BRYSON ET AL
blind and placebo-controlled study, the K-D2 point (the Korean hand
acupressure point in Koryo Hand Therapy) was evaluated for efficacy in
the prevention of postoperative nausea and vomiting. Placement of
capasaicin ointment on the K-D2 point of both hands 1 h before
laparoscopic cholecystectomy resulted in a significantly lower incidence
of PONV, and the need for rescue anti-emetic treatment was also lower50.
Stimulation of the P6 acupressure point has been associated with
decreased postoperative nausea and vomiting in high risk women and has
also been shown to increase patient tolerance to experimental
nauseogenic stimuli, as well as reducing the number of symptoms
experienced51.
The combination of antiemetic agents has been shown to
significantly reduce the incidence of PONV in patients at risk, below that
which is seen with any one agent alone52. Combination therapy is most
cost-effective for patients at high risk for the development of PONV and
medium risk patients are often successfully treated with a single agent53.
A summary of strategies is demonstrated in Table 5. It is interesting to
note that in one survey patients were willing to pay $100.00 out of pocket
to prevent PONV. Seventy six percent felt that avoiding PONV was
important54. The cost of a single incidence of postoperative vomiting has
been calculated to exceed $300.0037. While dexamethasone and
droperidol are the least expensive of the antiemetics, single doses of the
serotonin antagonists are usually less than $20.00.
Table 5
Anesthetic Strategies to Reduce the Incidence
of PONV in Patients at Risk
 Pre-medicate as needed to reduce anxiety
 Pre-hydrate to avoid hypotension
 Avoid nitrous oxide and potent inhaled agents when possible
 Choose regional techniques when possible
 Use propofol for induction and maintenance of anesthesia
 Use agents that reduce the need for opioids
 Administer combination antiemetic prophylaxis prophylactically and intraoperatively
MANAGEMENT OF THE PATIENT AT HIGH RISK FOR POSTOPERATIVE NAUSEA AND VOMITING
31
Management of a High Risk Case
A 30 year old lady presented for laparoscopic tubal ligation and
possibly oophorectomy. She gave a history of prolonged vomiting after an
ovarian cystectomy 1 year ago which required an extra 3 days of
hospitalization. She had a BMI of 34 and was a non smoker. Her history
was significant for anxiety and depression and both her parents were
diabetic.
The decision was made to proceed with a spinal technique, thus
avoiding the agents associated with general anesthesia that are known to
increase the incidence of PONV. The patient was premedicated with 2 mg
of midazolam and 10 mg of metoclopramide. One liter of fluid was
administered prior to placing the neuraxial block. The patient received 10
mg dexamethasone and 4 mg ondansetron immediately after placement of
the regional anesthetic and positioning was completed. Blood pressure
was checked every 2 minutes in order to recognize and treat hypotension
quickly. The intraoperative course was uncomplicated. Food and water
were withheld until the patient felt a need to drink and asked for oral
intake. The intravenous cannula was left in place until shortly before
discharge the same evening. Pain was managed with ketorolac
(Torodol®) 30 mg IV initially and later with acetaminophen orally. On
follow-up 24 hours later the patient reported no symptoms of PONV.
While one should never promise a patient an emesis free course, it is
often possible to prevent a repeat of a previous unpleasant experience.
Summary
The anesthesiologist is charged with both the prevention and
treatment of PONV. While fully one third of patients will develop PONV,
this manifests itself in the form of one or two episodes of emesis
associated with nausea, and the incidence of intractable PONV is less
than 1%. Prophylaxis for PONV is neither cost-effective nor indicated for
low risk patients, and most medium risk patients can be effectively treated
with a single agent. When administering an anesthetic to a patient at high
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ETHAN OLIVER BRYSON ET AL
risk for developing PONV, the plan should include pre-medication to
reduce anxiety, agents that reduce the need for intraoperative and
postoperative opioids, and the use of regional anesthetic techniques
whenever possible. If general anesthesia cannot be avoided, agents such
as propofol for induction and maintenance of anesthesia should be used to
avoid or reduce the need for nitrous oxide and the potent inhaled agents.
A combination of antiemetic prophylactic agents should be administered
to those judged to be at high risk for developing PONV, and adequate
intravenous therapy should avoid dehydration and hypotension
postoperatively.
MANAGEMENT OF THE PATIENT AT HIGH RISK FOR POSTOPERATIVE NAUSEA AND VOMITING
33
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