Transcript ANESTHETIC CONSIDERATIONS

Anesthesia for Thyroidectomy
SAAD A. SHETA
MBCh B, MA, MD
Associate Professor,
Consultant Anesthesiologist
KSU
THYROID
Anatomy
 SIMPLE GOITER(↓ I )
 HYPERTHYROIDISM
 AUTO IMMUNE THYOIDITIS (HASHIMOTO’S)
 CANCER
 VIRAL DE QUERVANS THYOIDITIS
THYROID
Pathophysiology
THYROID
Physiology
Thyroid hormones
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controls metabolic processes
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follicular cells synthesize/secrete thyroid hormones (T4, T3) when
stimulated by TSH, low iodide levels, iodide uptake
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Regulated by negative feedback loop of hypothalamus-anterior
pituitary-thyroid initiated by TRH causing TSH release
Thyroid hormones
TRH (Hypothalamus)
T4 thyroxine
TSH (Ant. Pituitary)
Thyroglobin (iodinated by peroxidase) back to cell
THYROID
Anesthetic consideration
HYPERTHYROIDISM
MULTI NODULAR DIFFUSE ENLARGEMENT
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PREGNANCY
THYOIDITIS
THYROID ADENOMA
CHORIOCARCINOMA
TSH SECRETING TUMOURS
Diagnostics :
Thyroid Function Tests
Test
Purpose
Total plasma Thyroxine (T4) level
Detect > 90% hyperthyroidism
Influenced by T4- binding protein (TBG)
Resin Triiodothyroxine Uptake
(RT3U)
▲T4 level
Thyroid dysfunction Vs ▲ T4 binding globulin (TBG)
total Triiodothyroxine (T3) level
↑ in hyperthyroidism
↓ in hypothyroidism (or cirrhosis & nutrition)
Thyroid Stimulating Hormone (TSH)
level
Primary Hypothyroidism
↑ in hypothyroidism (beforeT4 level ↓)
Thyroid Scan
Iodide Concentrating Capacity
Functioning thyroid rarely malignant
Ultrsonography
Cystic (rarely malignant)
Antibodies to TG components
Hashimoto’s thyoiditis
Diagnostics:
Differential Diagnosis
Condition
T4
RT3U
T3
TSH
Hyperthyroidism
↑
↑
↑
normal or ↓
Primary
Hypothyroidism
↓
↓
↓
↑
Secondary
Hypothyroidism
↓
↓
↓
↓
Pregnancy
↑
↓ or normal
normal
normal
Hyperthyroidism:
*Propylthiouracil
Medical Treatment
Inhibit thyroid hormone synthesis
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Inhibit peroxidase
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*inhibit peripheral conversion of T3 to T4
Potassium or sodium iodide
Prevent hormone release
propranalol
Decrease heart rate
(quicker 7-14 days vs. 2 -6 weeks)
IV propranalol (0.2 – 10 mg )
IV esmolol (50 – 500 ug)
Emergency Surgery
Hyperthyroidism : Surgical Treatment
SUBTOTAL OR PARTIAL THYROIDECTOMY
 removal of about 5/6’s of thyroid gland to treat hyperthyroidism
 enlarged glands affecting breathing or swallowing problems;
tracheal or esophageal obstruction
ANESTHETIC CONSIDERATIONS “PROBLEMS”
 FROM MAJOR MANIFESTATIONS
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Weight loss
Heat Intolerance
Muscle weakness (Large muscle group)
Diarrhea - Dehydration
Menstrual Abnormalities - Anemia
Hyperactive reflexes and Nervousness
Exophthalmos – Exposure keratitis
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Hypercalcaemia
Bone loss (↑alkaline phosphatase)
Thrombocytopenia
ANESTHETIC CONSIDERATIONS “PROBLEMS”
 CARDIOVASCULAR SYSTEM
 Tachycardia / palpitation
Cardiac Arrhythmias AF
 Hyperdynamic circulation
↑ myocardial contractility
↑ CO
Cardiomegally
High output HF
 Mitral valve prolapse
(papillary muscles dysfunction)
ANESTHETIC CONSIDERATIONS “PROBLEMS”
 Enlargement of the gland Retrosternal
 Lower tracheal compression
 SVC obstruction
 Respiratory obstruction
 Tracheomalasia (after removal)
 ABNORMAL GLUCOSE TOLERANCE
 EXOPHTHALMOS
 THYROTOXIC MYOPATHIES
ANESTHETIC CONSIDERATIONS “PROBLEMS”
 Thyroid Crisis
THYROID STORM IS A LIFE THREATENING EXACERBATION OF HYPERTHYROIDISM
PRECIPITATED BY (INJURY, INFECTION, SURGERY )
MOST OFTEN PO IN UNTREATED OR INADEQUATE TREATED PATIENT IN EMERGENCY SURGERY
Mimics Malignant Hyperthermia Pheochromocytoma, Inadequate anesthesia
Clinical Manifestation
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ANXIETY, CONFUSION, RESTLESSNESS , DELIRIUM
PYREXIA, FLUSHING, SWEATING, ABDOMINAL PAIN
TACHYCARDIA, AF, HIGH OUTPUT CHF
DEHYDRATION
ANESTHETIC CONSIDERATIONS “PROBLEMS”
MANAGEMENT
 Treat the precipitating cause (infection)
 Sedation, ETT, O2, IPPV (mat be required)
 Hydration (glucose containing IV fluids )
 Propranalol 0.5 mg, repeat till HR is < 100
 Propyl thiouracil 250 mg 6 hourly (Orally or via ETT)
 Sodium iodide 1 mg, IV, 12 hourly
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Digoxin (CHF with AF & rapid VR)
Dexamethazone or hydrocortisone
Circulatory Shock (vasopressor)
Cooling (Blanket, Pethedine)
ANESTHETIC CONSIDERATIONS “PREOPERATIVE”
 Careful assessment of upper airway & tracheal deviation
 Thoracic inlet X-ray, CT scan
 Patient must be rendered
EUTHYROID
 Use anti-thyroid drugs and B - blockers
 Resting pulse rate 85/min
 Benzodiazepines premedication
In Emergency Surgery (before Euthyroid)
 Iv propranalol (0.2 – 10 mg)
 Iv Esmolol (50 – 500 ug)
Caution with CHF
However , ↑Pump function by control fast V. rate)
 Consider PCWP
ANESTHETIC CONSIDERATIONS “INTRAOPERATIVE”
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Closely monitor temperature & CVS
Protect eyes (lacerations)
Use armored tracheal tube
Raise head 10-15 degrees (▼air embolism)
 Blunt the response to laryngoscopy
 Normal MAC (prevent Exaggerated SNS to Surgical Stimulation)
 Avoid Drugs that stimulate SNS (Ketamine)
 Liver susceptible to damage due to Enflurane
 Use muscle relaxants carefully (myopathies)
 Epinephrine free local anesthetics
ANESTHETIC CONSIDERATIONS “POSTOPERATIVE”
 Extubation
 Light Anesthesia
 Inspection of the cord
 Under optimal circumstances for intubation
 Injury to recurrent laryngeal nerve
 Bilateral stridor & laryngeal obstruction (re-intubation )
 Unilateral : hoarseness
 Selective injury of both RLNs
(adductive fibers , leave abductors relatively unopposed Caution: → Aspiration )
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Stridor
Bleeding / Haematoma
Dyspnoea
Pneumothorax
Air embolism
Hypo parathyroidism in 24 – 48 hrs (Hypocalcaemia → Laryngeal Spasm, Tetany)
Parathyroid glands
parathyroid hormone (PTH)
control calcium levels (with calcitonin)
Vitamin D :
facilitate absorption of ca ++, ph++, mg ++from the gut
facilitate bone reabsorption by parathormone
Parathyroid glands
parathyroid hormone (PTH)
INCREASE Ca ++
Plasma half life 2-5 minutes
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mobilize ca++ to extracellular fluid
 Active absorption of ca ++ from the small intestine
vitamin D dependent
 Increase bone resorption of ca ++
 Increase renal tubular resorption of ca++
Calcium
Hypercalcaemia > 10.5 mg/dl
Normal calcium 8.6 – 10.4 mg/dl
Hypocalcaemia < 8.5 mg/dl
serum calcium
40% clinically relevant fraction)
50 % bound to albumin
10 % bound to chelating agents
decrease in serum albumin 1 gm → decrease in serum calcium 0.8 mg/dl
Effects of Hypoparathyroidism
ORGAN
SYSTEM
CLINICAL
MANIFESTATIONS
Cardiovascular
Hypotension, CHF, ECG changes
Musculoskeletal
Muscle cramps, weakness,
Neurological
Neuromuscular irritability, laryngeospasm,
Inspiratory stridor,
Tetany, peripheral paresthesia, mental status
changes
Hypocalcaemia : Medical Treatment
Ca gluconate
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IV: 10 – 20 ml of (10 %)
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Infusion: 10 ml (10%) / 500 ml for 6hrs
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oral
maintain Ca ++ level to lower
normal
Vitamin D
Monitor
Ca ++
Ph++
Mg++