CASE BASED LEARNING

BOOK CASE SCENRIO

A 52 year old

Anxious man.

Presents for revision of a previous tympano-mastoidectomy on an

Ambulatory basis.

The patient is otherwise in good general health.

He has undergone several previous procedures

Resulted in post operative nausea and vomiting.

QUESTIONS

Is the anxious patient a good candidate for surgery under monitored anaesthesia care (MAC)?

What general anaesthetic techniques are most likely to minimize postoperative nausea and vomiting (PONV)?

Are regional anesthetics less likely to result in PONV in this patient?

Why is control of blood loss important during middle ear surgery?

Are long-acting neuromuscular blocking agents contraindicated in middle ear surgery?

Is the anxious patient a good candidate for surgery under monitored anaesthesia care (MAC)?

MAC

MAC is a planned procedure during which the patient undergoes local anesthesia together with sedation and analgesia - (ASA).

ASA Newsletter 1998;62(12).

First choice in 10-30% of all the surgical procedures.

The 3 fundamental elements of conscious sedation are:

A safe sedation

The control of the patient anxiety

The pain control. MINERVA ANESTESIOL 2005;71:533-8

Able to answer to orders appropriately and to protect airways.

Consciousness evaluation

Clinical

BIS.

Discharge - fast.

MINERVA ANESTESIOL 2005;71:533-8

Retroauricular tympanoplasty and tympanomastoidectomy under local anesthesia with sedation can be well tolerated by the patient, with minimum discomfort.

SARMENTO KM JR, TOMITA S.

Prospective study of 83 surgeries in 62 patients .

28 type I tympanoplasties, 12 tympanoplasties with ossicular reconstruction, 40 canal wall up mastoidectomies, and 3 revision tympanoplasties.

Local infiltration - lidocaine 2% with 1:100 000 epinephrine infiltrated in the retroauricular area and from below the pinna.

Sedation was achieved with 50mg of intramuscular promethazine 1h before surgery and intravenous midazolam (0.03mg/kg) at the beginning of surgery.

Subsequent doses of midazolam were given to maintain adequate sedation, up to 10mg.

The discomfort during surgery was assessed by the patient with a score from 0 to 4.

0=no discomfort and 4=extreme discomfort).

Discomfort due to pain had a mean score of 0.83.

Noise discomfort (from drilling and manipulation of instruments) had the lowest mean score (0.70),

Discomfort from body and neck position had the highest mean score (1.51).

Acta Otolaryngol. 2008 Sep 11:1-3

What general anaesthetic techniques are most likely to minimize postoperative nausea and vomiting (PONV)?

PONV

30% - postoperative nausea and vomiting (PONV).

Anesthesiology 1992;77:162–84.

RISK FACTORS FOR PONV

Age

Gender

Obesity

Surgical procedure (Ear surgery).

History of motion sickness or PONV. Br J Anaesth 1996;76:347–51.

Anxiety.

ANXIETY

Increased anxiety before undergoing anesthesia and surgery is a risk factor for the development of PONV.

Anesthesiology 1992;77: 162–84.

Operations in or around the ear are considered high risk for PONV – 70%

Anesth Analg 1996;82:S37.

Anaesthesia 1997;52:544–6.

47% of 162 adults who had middle ear or mastoid surgery experienced PONV.

Remained significantly longer in PACU than patients who did not have this complication.

Anesth Analg 1996;82:S37

Surgery in or around the ear may disturb the vestibular labyrinth, which (along with the chemoreceptor trigger zone) incites the vomiting center.

The trigger zone is located in the area postrema (near the trigonum of the vagus nerve), which contains a high concentration of 5-HT3 receptors.

The vomiting reflex may be activated when serotonin stimulates the vagal afferents through the 5-HT3 receptors.

J. Clin. Anesth., vol. 11, November 1999

ANTI-EMETIC CHOICES FOR PONV

Promethazine - phenothiazine, has predominantly antidopaminergic effects with moderate antihistaminic and anticholinergic properties.

It has been recommended as an antiemetic for patients having ear surgery.

Promethazine can cause significant sedation and lethargy.

Can Anaesth Soc J 1984;31:407–15.

Ondansetron, a 5-HT3 receptor antagonist, decreased PONV after tympanoplasty.

Can J Anaesth 1996;43:939–45.

Scopolamine.

Droperidol.

Prolongation of the QT interval.

Dexamethasone. Anesth Analg 2000;90:186-94

Metochlopramide.

A combination of antiemetics that have differing receptor sites may produce better results than either drug alone.

The combination of promethazine and ondansetron significantly reduces the incidence of PONV during the first 24 hours after middle ear surgery.

The combination reduces significantly the severity of vomiting.

Anesth Analg 1996;83:117–22.

Propofol infusion reduces PONV as compared to volatile anesthetics.

Anesthesiology 1999;91:253-61.

Nitrous increases PONV. Anesthesiology 1996;85: 1055-62.

TIVA with propofol in place of a volatile anesthetic and nitrous oxide is equivalent to the use of a volatile anesthetic with a prophylactic antiemetic drug.

N Engl J Med 2004;350:2441-51.

Opioid-sparing techniques, including the use of other analgesics such as nonsteroidal antiinflammatory drugs and regional blocks.

Do not use high dose neostigmine (>2.5mg).

Hydration with 20 mL/kg of appropriate intravenous fluid preoperatively significantly decreases postoperative nausea on day 1 .

Anesth Analg 1995;80:682-6.

NON PHARMACOLOGIC TREATMENTS

Acupuncture, electroacupuncture, transcutaneous electrical nerve stimulation, acupoint stimulation, and acupressure.

Similar to pharmacologic agents in preventing early and late vomiting. Anesth Analg 1999;88:1362-9.

Acupressure wristbands may be effective in preventing PONV after short surgical procedures when applied prior to emetic stimulus exposure.

Anesth Analg 1997;84:821-5.

TYMPANO-MASTOIDECTOMY

Tympanoplasty and mastoidectomy.

Middle ear surgery.

Still operative field,

Minimal bleeding.

CONDUCT OF GA FOR MIDDLE EAR SURGERY

Anesthesia is induced with a hypnotic and short-acting muscle relaxant or by inhalation.

Maintainence with a volatile anesthetic.

Antiemetics should be given because postoperative vomiting is very common with ear surgery

Are regional anesthetics less likely to result in PONV in this patient?

Regional anesthesia rather than general anesthesia should be used when possible.

Why is control of blood loss important during middle ear surgery?

BLOODLESS FIELD

Delicate microsurgery of the ear requires adequate hemostasis.

Volatile anesthetics and/or vasodilators.

MAP – 60-70mm Hg.

Elevation of the head of the bed to approximately 15° to decrease venous congestion and local application of epinephrine for vasoconstriction usually improve operating conditions.

Are long-acting neuromuscular blocking agents contraindicated in middle ear surgery?