Preoperative Evaluation by Internal Medicine in Cataract Surgery

Preoperative Assessment by Internal Medicine in Cataract Surgery: Focus on Surgical Risk

Evaluation by an internal medicine physician before cataract surgery is crucial to identify and manage systemic conditions that could increase the risk of anesthetic, surgical, or postoperative complications. Here are the key details:

Objectives of the Internal Medicine Assessment

Assess cardiovascular and pulmonary risk to tolerate sedation/anesthesia.

Optimize chronic conditions (diabetes, hypertension, anticoagulation).

Detect uncontrolled infections or comorbidities that contraindicate surgery.

Coordinate with the ophthalmologist to customize the perioperative plan.

Specific Clinical Assessment

1. Complete Medical History

✔ Current medical conditions:

Diabetes (risk of postoperative macular edema if HbA1c >8%).

Uncontrolled hypertension (increased risk of choroidal hemorrhage).

COPD or sleep apnea (risk with deep sedation).

✔ Medications:

Anticoagulants (warfarin, OCPs): Discontinue or adjust dose?

Antiplatelet agents (aspirin, clopidogrel): Generally continued.

Insulin or hypoglycemic agents: Adjust fasting schedules.

2. Focused Physical Examination

Cardiopulmonary: Murmurs, arrhythmias, crackles (indicate ECG if symptoms are present).

Neurological: Evaluate tremors or involuntary movements (affecting surgical positioning).

Airway: Anticipate intubation difficulties (if general anesthesia is required).

3. Laboratory and Imaging Studies

Blood chemistry

Glucose, electrolytes (Na⁺, K⁺, Cl⁻), creatinine, BUN, total protein, albumin.

Why is this important?

✔ Uncontrolled diabetes (fasting glucose >126 mg/dL or HbA1c >7-8%):

Increases the risk of postoperative diabetic macular edema.

Requires adjustment of hypoglycemic agents/insulin during preoperative fasting.

✔ Electrolyte imbalance (e.g., hypokalemia <3.5 mEq/L):

Can cause arrhythmias under sedation.

✔ Kidney disease (elevated creatinine):

Affects the elimination of drugs used during/during anesthesia.

Blood count:

Hemoglobin (Hb), hematocrit (Hct), leukocytes, platelets.

Why is it important?

✔ Anemia (Hb <10 g/dL):

Can delay surgery if symptoms are present (fatigue, tachycardia).

Risk of tissue hypoxia during sedation.

✔ Leukocytosis (>11,000/μL):

Suggests active infection (relative contraindication for elective surgery).

✔ Platelets <100,000/μL:

Increased risk of bleeding (relevant if peribulbar anesthesia is planned).

Lipid profile

Total cholesterol, LDL, HDL, triglycerides.

Why is this important?

✔ Uncontrolled hyperlipidemia (LDL >160 mg/dL):

Associated with increased cardiovascular risk during the perioperative period.

Patients on statins should continue them (they prevent ischemic events).

✔ Triglycerides >500 mg/dL:

Risk of acute pancreatitis (contraindication for elective surgery).

Liver Function Tests (LFTs)

Total/direct bilirubin, AST, ALT, alkaline phosphatase, albumin, INR.

Why is it important?

✔ Elevated AST/ALT (>3 times the upper limit):

Suggests active hepatitis or drug toxicity (e.g., statins, acetaminophen).

May alter anesthetic metabolism.

✔ Elevated INR (>1.5 without anticoagulants):

Indicates liver failure or vitamin K deficiency.

Increases risk of bleeding (requires preoperative correction).

✔ Albumin <3.5 g/dL:

Associated with malnutrition or chronic liver disease.

Increased risk of postoperative corneal edema.

Thyroid Profile

TSH, free T4, T3 (in selected cases).

Why is it important?

✔ Uncontrolled hypothyroidism (TSH >10 mIU/L):

Risk of severe bradycardia under sedation.

Increased sensitivity to anesthetic drugs.

✔ Hyperthyroidism (TSH <0.1 mIU/L):

Risk of thyrotoxic crisis due to surgical stress.

Relative contraindication until hormones are normalized.

Glycated hemoglobin (HbA1c)

Especially in patients with diabetes or altered blood glucose levels. Diabetic patients or those with fasting glucose >126 mg/dL.

Average blood glucose over the past 2-3 months.

Importance in cataract surgery:

✔ Diabetes control:

HbA1c >8%: Increases the risk of:

Postoperative diabetic macular edema.

Delayed corneal healing.

Ideal presurgical goal: HbA1c <7-8% (according to the ophthalmologist's criteria).

✔ Clinical decisions:

If the value is very high (>9%), surgery may be postponed until glycemic control is optimized.

Patients with high HbA1c require strict glucose monitoring on the day of surgery.

Coagulation times (PT/PTT/INR). Use of anticoagulants, liver disease, or previous bleeding.

PT (Prothrombin time) and PTT (Partial thromboplastin time): Evaluate the extrinsic and intrinsic pathways of coagulation.

INR (International Normalized Ratio): Standard for anticoagulated patients.

Importance in cataract surgery:

✔ Patients on anticoagulation (e.g., warfarin, acenocoumarol):

INR >3.0: Increases risk of intraocular hemorrhage (especially with peribulbar anesthesia).

Management:

Surgery under topical anesthesia: Does not always require discontinuation of anticoagulants (low risk).

If peribulbar/retrobulbar anesthesia is used: Adjust dose or temporarily discontinue (depending on thromboembolic risk).

✔ Patients with liver disease or vitamin K deficiency:

Elevated PT/PTT indicate risk of spontaneous bleeding.

Serum electrolytes. Patients on diuretics, CKD, arrhythmias, or symptoms of imbalance (weakness, confusion).

Fluid and electrolyte balance is crucial for cardiac and neuromuscular function.

Importance in cataract surgery:

✔ Hypokalemia (K⁺ <3.5 mEq/L):

Increases the risk of arrhythmias under sedation.

Requires preoperative correction (K⁺ supplementation).

✔ Hyponatremia (Na⁺ <135 mEq/L):

Can cause perioperative confusion or seizures.

✔ Hypercalcemia (Ca⁺ >10.5 mg/dL):

Associated with parathyroid or metastatic disease.

Can alter muscle and cardiac contraction.

Chest X-ray

Very useful in severe COPD or suspected active infection. Also to rule out pathology in healthy patients

Electrocardiogram (ECG)

To rule out pathology in healthy patients and better assess patients with heart disease

⚠️ Conditions That May Delay Surgery

❌ Acute infection (respiratory, urinary, etc.).

❌ Decompensation of chronic diseases:

HBP with BP >180/100 mmHg.

Hyperglycemic crisis (blood glucose >250 mg/dL).

❌ Severe anemia (Hb <8 g/dL).

❌ INR >3.0 in patients on warfarin (requires reversal with vitamin K).

❌ TSH >20 mIU/L with symptoms (myxedema).

Perioperative Drug Management

Anticoagulants (warfarin):

Surgery under topical anesthesia: Not always discontinued (low risk of bleeding).

If peribulbar block is required: Discontinue 3-5 days prior (depending on thromboembolic risk).

Metformin: Discontinue 24-48 hours prior (risk of lactic acidosis with IV contrast).

Diuretics: Adjust dose to avoid intraoperative hypotension.

Risk Scales Used

ASA (American Society of Anesthesiologists): Classifies the patient into grades I (healthy) to V (moribund).

ASA I-II: Low risk (ideal candidates for outpatient surgery).

ASA ≥III: Requires multidisciplinary management (e.g., cardiologist).

Coordination with the Ophthalmologist

The internist should communicate:

✔ Patient stability for surgery.

✔ Specific recommendations (e.g., need for intraoperative glucose monitoring in diabetics).

✔ Allergies or adverse reactions to drugs.

Why is this assessment essential?

It reduces cardiopulmonary complications associated with sedation by 30% (Journal of Perioperative Medicine).

Avoids last-minute cancellations due to hyperglycemia or uncontrolled hypertension.

Allows for choosing the safest type of anesthesia (topical vs. regional).

Key Facts

80% of postoperative complications in older patients are related to non-optimized comorbidities (OAA).

Unnecessary discontinuation of anticoagulants causes more thromboembolic events than bleeding (NEJM).

Diabetics with HbA1c >8% have a 3-fold increased risk of macular edema (Ophthalmology).