Ординатура / Офтальмология / Английские материалы / Oxford American Handbook of Ophthalmology_Tsai, Denniston, Murray_2011

PREOPERATIVE ASSESSMENT (1) 687

Preoperative workup

•Operations under local anesthesia: minimal workup is required unless history and systemic examination suggest significant systemic disease that would be worthy of investigation in its own right.

•Operations under general anesthesia: general investigations usually include CBC, UA, glucose, and ECG; specific investigations (CXR, echocardiography) are directed according to patient history and examination. It is common practice to limit routine preoperative testing in healthy younger patients in whom a general history and examination is satisfactory.

Box 21.1 Specific systemic contraindications to ophthalmic surgery

•Uncontrolled BP (e.g., >180/100 mmHg)

•Myocardial ischemia (unstable ischemic heart disease or myocardial infarction (MI) in the last 3 months)

•Uncontrolled hyperglycemia

•Uncontrolled arrhythmias

•Excessive INR

•Acute systemic illness

688 CHAPTER 21 Perioperative care

Preoperative assessment (2)

Preoperative management

•Patients for intraocular surgery: appropriate preoperative drops (Table 21.1).

•Patients for general anesthesia: nothing by mouth (e.g., from 8 hours before).

•Patients with diabetes: normal (or near-normal) regime can be continued in most patients having local anesthesia; a sliding scale may be required in poorly controlled patients or some insulinrequiring patients having general anesthesia (coordinate care with anesthesiologist).

•Patients with hypertension: continue antihypertensives (including day of surgery); for example, consider postponing surgery if BP >180/100 mmHg.

•Patients with ischemic heart disease: continue usual antianginal medication and ensure their usual prn medication (e.g., sublingual nitroglycerin) is available in the operating room; postpone surgery if within 3 months of myocardial infarct.

•Patients with valvular heart disease: antibiotic prophylaxis is not required for intraocular procedures.

•Patients on aspirin: continue for intraocular and strabismus surgery; for orbital and oculoplastic surgery, it would ideally be discontinued for

2 weeks prior to surgery. However, this must be discussed with their PCP.

•Patients on anticoagulants: ideally the INR should be <3 for intraocular and strabismus surgery but <2 for orbital and oculoplastic surgery (see Table 21.2). This should be checked within 48 hours

of surgery. If this is not compatible with their therapeutic target, coordinate care with their hematologist or PCP. They may consider changing to heparin in the perioperative period.

Table 21.2 Target INR levels

690 CHAPTER 21 Perioperative care

Ocular anesthesia (1)

Cataract surgery has become the most commonly performed surgery in the United States. In the 1990s, there was a dramatic shift from general to local anesthesia for the majority of ophthalmic surgeries.

Topical anesthesia

Indications

•Cooperative patient + experienced surgeon + routine suitable operation (usually cataract surgery).

Method

•Repeated preoperative ± intraoperative anesthetic drop.

•Consider also intracameral lidocaine (1% isotonic preservative-free) and an anesthetic-soaked sponge in the inferior fornix.

Complications

•Pain, eye movement, epithelial toxicity; in an uncooperative patient, surgery may be hazardous with increased risk of operative complications.

Subtenon’s block

Indications

•Relatively complete anesthesia of the globe and akinesia desired; patient sufficiently cooperative to keep head still during surgery.

Method

Apply topical anesthetic to conjunctiva, ask the patient to look in the opposite direction to the intended injection site (e.g., superotemporally). Open conjunctiva around 8 mm from the limbus (e.g., inferonasally), dissect down to bare sclera with blunt curved scissors, insert subtenon’s cannula (blunt curved), and slide cannula posteriorly along the globe. Inject 2.5–3.0 mL lidocaine 2% (or lidocaine 2%/bupivicaine 0.5% mix).

Complications

•Failure (backflow if wide track, leaks out if conjunctiva perforated twice), conjunctival chemosis, conjunctival hemorrhage.

Peribulbar block

Indications

Relatively complete anesthesia of the globe and akinesia is desired. The patient needs to be sufficiently cooperative to keep the head still during surgery. An anesthesiologist trained in the technique is also needed.

Method

The surgeon asks the patient to fix his/her gaze on a target directly ahead, and uses a sharp, short needle (27 or 25 gauge, 25–31 mm) to inject a total of 4–8 mL lidocaine 2% (or lidocaine 2%/bupivicaine 0.5% mix) around the globe. This may require a single injection (either inferotemporal extraconal or medial extraconal) or a combined approach if akinesia is insufficient. Ocular compression (e.g., Honan balloon) is administered for 20–30 min.

OCULAR ANESTHESIA (1) 691

Complications

•Excessive positive pressure (surgery may become hazardous), ptosis, diplopia, ocular perforation (<0.1% but 0.7% if axial length >26 mm), brainstem anesthesia, oculocardiac reflex (0.03%), orbital hemorrhage.

692 CHAPTER 21 Perioperative care

Ocular anesthesia (2)

General anesthesia

Indications

Complete akinesia and deep anesthesia are required. The patient is unlikely to keep still (mental impairment, children, young adult, very anxious, uncontrolled tremor) or had a previous adverse reaction to local anesthetic. Globe trauma is contraindicative of local anesthesia.

Method

The patient must have adequately fasted (e.g., 8 hours) and all appropriate investigations must have been performed (e.g., CBC, UA, ECG when indicated). General anesthesia requires preoperative assessment (identify and, if possible, minimize anesthetic risk factors), premedication (sedation, amnesia, antiemesis), induction, intubation, maintenance, recovery, and postoperative analgesia.

Effect on IOP

Table 21.3 General anesthesia and IOP

Complications

These include respiratory depression (l hypoxia), cardiac depression (lmyocardial ischemia), aspiration of gastric contents, anaphylaxis, malignant hyperthermia, oculocardiac reflex, and difficult recovery (respiratory weaning, psychological problems).

TREATMENT OF ANAPHYLAXIS 693

Treatment of anaphylaxis

Anaphylaxis is most commonly encountered by the ophthalmologist when a patient undergoes FA. It is an extreme form of type I hypersensitivity reaction. Severe anaphylaxis occurs in 1 out of every 1900 FAs. Fatal anaphylaxis occurs in 1 out of every 220,000 FAs. Appropriate initial treatment should be instituted by the ophthalmic team while calling for emergency medical support.

First-line

↓

Check responsiveness + call for help

↓

Secure airway

↓

Give 100% O2

↓

Lay patient flat and elevate legs

↓

Give 0.5 mg (0.5 mL of 1:1000) adrenaline IM

This may be repeated if necessary every 5 min according to BP, pulse, and respiratory function

↓

Secure IV access

↓

Give 10 mg chlorphenamine IV

↓

Give hydrocortisone 200 mg IV

Meanwhile: Remove precipitant (where possible)

Monitor pulse, BP, respiratory function

Second-line

If hypotensive

↓

Give fluids IV

e.g. 500 mL normal saline over 15 min stat then titrate according to BP

If respiratory compromise

↓

Give nebulized bronchodilators

e.g., 2.5 mg salbutamol; titrate according to respiratory function

In severe cases the emergency medical/anesthetic team may add in IV aminophylline, perform emergency tracheotomy, or even intubate/ventilate

Figure 21.1 Management of anaphylaxis.

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Therapeutics

Ocular medication: general 696

Topical antibiotics 698

Topical anti-inflammatory agents 700

Topical glaucoma medications 702

Topical mydriatics 704

Systemic medication: glaucoma 705

Systemic corticosteroids: general 706

Systemic corticosteroids: prophylaxis 708

Other systemic immunosuppressants 709