CHARGE Syndrome

Anesthetic Management of Pt. with CHARGE Syndrome

Definition:

➧ A syndrome characterized by: 

1-Coloboma of the eye (Figure 1) 

2-Heart defects (ASD, VSD, PDA, TOF, Rt. Aortic arch, Double outlet Rt. ventricle) 

3-Atresia of the choanae (Figure 2) 

4-Retarded growth development and/or central nervous system abnormalities 

Severe sensorineural, visual, and vestibular deficits are suggested as the cause of delay in walking development, rather than retardation. 

5-Genital hypoplasia in males (Hypogonadism) 

6-Ear anomalies (Figure 3) and/or deafness (Figure 4) 

➧ Diagnosis is made on the presence of at least four of the criteria.

Figure 1: Coloboma of iris

Figure 2: Atresia of the choanae

Figure 3: Ear anomalies

Figure 4: Deafness (BAHA)

➧ Other abnormalities include:

Muscular hypotonia, facial palsy, tracheo-oesophageal fistula, cleft lip and palate, micrognathia, laryngomalacia, pharyngolaryngeal hypotonia (inability to maintain the patency of the pharyngolaryngeal passage), subglottic stenosis and other upper airway abnormalities. 

➧ There is a high incidence of abnormal blood gas levels and sleep problems. Cardiorespiratory arrest is common in this group of patients. 

➧ Gastroesophageal reflux has been reported. 

➧ Anesthesia may be required for choanal atresia repair, cardiac surgery, tracheoesophageal fistula, ear surgery, Nissen’s fundoplication, and tracheostomy.

Anesthetic Management:

Preoperative Management: 

1. Preoperative assessment of congenital cardiac defects. 

2. Preoperative assessment of upper airway abnormalities. Pharyngo-laryngeal hypotonia causes variable obstruction, which becomes more pronounced during sleep and during inspiration. 

3. Precautions against aspiration of gastric contents. 

Intraoperative Management: 

1. A range of sizes of endotracheal tubes should be available due to subglottic stenosis. 

2. If micrognathia is present, inhalational induction is advisable. 

3. Tendency for upper airway collapse during light anesthesia due to laryngomalacia or pharyngolaryngeal hypotonia. Edematous arytenoids may result from gastroesophageal reflux. 

4. Tracheal intubation difficulties have been recorded and intubation problems are increased with increasing age. 

5. Tracheostomy may be required for long-term management. Some authors felt that early tracheostomy helped to avoid hypoxemic events in infancy. 

Postoperative Management: 

1. Postoperative monitoring of apnea. 

2. Feeding difficulties and a high incidence of gastroesophageal reflux. 

Postoperative Mortality: 

1. Apnea due to pharyngolaryngeal hypotonia. 

2. Postoperative deaths were frequently associated with pulmonary aspiration. 

3. Patients require multiple anesthetics, with an increased incidence of postoperative mortality.

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Ultrasound Artifacts

Ultrasound Artifacts

1-Reverberation artifact:

➧ The processing unit in the ultrasound machine assumes echoes return directly to the processor from the point of reflection. 

➧ Depth is calculated as D = V × T, where V is the speed of sound in biological tissue and is assumed to be 1,540 m/sec, and T is time. 

➧ In a reverberation artifact, the ultrasound waves bounce back and forth between two interfaces (the lumen of the needle) before returning to the transducer. 

➧ Since velocity is assumed to be constant at 1,540 m/sec by the processor, the delay in the return of these echoes is interpreted as another structure deep into the needle and hence the multiple hyperechoic lines beneath the block needle (Figure 1). 

Figure 1: Reverberation artifact

2-Mirror artifact:

➧ A mirror artifact is a type of reverberation artifact. 

➧ The ultrasound waves bounce back and forth in the lumen of a large vessel (subclavian artery). 

➧ The delay in the time of returning waves to the processor is interpreted by the machine as another vessel distal to the actual vessel (Figure 2). 

Figure 2: Mirror artifact

3-Bayonet artifact:

➧ The processor assumes that the ultrasound waves travel at 1,540 m/sec through biological tissue. However, we know that there are slight differences in the speed of ultrasound through different biological tissues. 

➧ The delay in the return of echoes from tissue that has a slower transmission speed, coupled with the processor’s assumption that the speed of ultrasound is constant, causes the processor to interpret these later returning echoes from the tip of the needle traveling in tissue with slower transmission speed as being from a deeper structure and thus giving a bayoneted appearance. 

➧ If the tip is traveling through tissue that has a faster transmission speed, then the bayoneted portion will appear closer to the transducer (Figure 3). 

Figure 3: Bayonet artifact

4-Acoustic Enhancement artifact:

➧ Acoustic enhancement artifacts occur distal to areas where ultrasound waves have traveled through a medium that is a weak attenuator, such as a large blood vessel. 

➧ Enhancement artifacts are typically seen distal to the femoral and the axillary artery (Figure 4). 

Figure 4: Acoustic enhancement artifact

5-Acoustic shadowing:

➧ Tissues with high attenuation coefficients, such as bone, do not allow the passage of ultrasound waves. 

➧ Therefore any structure lying behind tissue with a high attenuation coefficient cannot be imaged and will be seen as an anechoic region. (Figure 5). 

Figure 5: Acoustic shadowing artifact

6-Absent blood flow:

➧The Color-Flow Doppler may not detect blood flow when the ultrasound probe is perpendicular to the direction of blood flow (Figure 6). 

➧ A small tilt of the probe away from the perpendicular should visualize the blood flow (Figure 7, Figure 8). 

➧ Alternatively, for deep vascular structures, signals may be lost due to attenuation. 

➧ Increasing gain, while in Doppler Color-Flow mode, will increase the intensity of the returning signals, which may detect blood flow that was not previously detected. 

Figure 6: Radial a. Absent blood flow artifact

Figure 7: Radial a. Probe tilted away from the direction of blood flow

Figure 8: Radial a. Probe tilted towards the direction of blood flow

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Drugs with Rebound Phenomenon

Drugs with Rebound Phenomenon

➧ The rebound effect, or rebound phenomenon, is the tendency of some medications, in sudden discontinuation, to cause a return of the symptoms it relieved, to a degree stronger than they were before treatment first began. Medications with a known rebound effect can be withdrawn gradually, or, in conjunction with another medication that does not exhibit a rebound effect. 

1-Sedative Hypnotics: 

-Benzodiazepine withdrawal can cause rebound anxiety and insomnia. 

-Eszopiclone and Zolpidem) can cause rebound insomnia. 

2-Stimulants:

➧ e.g. Methylphenidate or Dextroamphetamine 

➧ Rebound effects include psychosis, depression, and a return of ADHD symptoms but in a temporarily exaggerated form. 

3-Antidepressants:

➧ e.g. SSRIs

➧ Cause rebound depression and/or panic attacks and anxiety when discontinued. 

4-Alpha-2 adrenergic agents:

➧ e.g. Clonidine and Guanfacine

➧ The most notable rebound effect is rebound hypertension. 

5-Beta-adrenergic antagonists:

➧ e.g. Bisoprolol

➧ Sudden withdrawal leads to rebound tachycardia and anginal pain. 

6-Highly potent corticosteroids:

➧ e.g. Clobetasol for psoriasis

➧ Abrupt withdrawal can cause rebound psoriasis and hypoglycemia. 

7-Warfarin: 

➧ Withdrawal leads to thromboembolism 

8-Alcohol:

➧ Withdrawal leads to alcohol withdrawal syndrome: (anxiety and convulsions). 

9- Painkillers:

➧ Withdrawal can cause rebound headaches. 

10-Topical decongestants:

➧ Nasal sprays e.g. Phenylephrine

➧ Continuous usage can lead to constant nasal congestion, known as Rhinitis medicamentosa, and discontinuation to rebound nasal congestion.

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Drugs affecting IOP

Drugs affecting IOP

➧ Normal intraocular pressure (IOP) is between (10 - 20 mmHg). The average value of IOP is 15.5 mmHg with fluctuations of about 2.75 mmHg.

➧ IOP also varies with other factors such as heart rate, respiration, fluid intake, systemic medication, and topical drugs.

➧ Intraocular vascular tone is predominantly affected by CO₂; hypocarbia decreases IOP through vasoconstriction of the choroidal blood vessels and decreases the formation of aqueous humor through reduced carbonic anhydrase activity. The increased IOP associated with hypoventilation and hypercarbia occurs as a result of vasodilation of CBV and increases in central venous pressure. 

A) Drugs that ↑ IOP:

1-Steroid-induced glaucoma:

Mechanism:

Is a form of open-angle glaucoma that is usually associated with topical steroid use, but it may develop with inhaled, oral, intravenous, periocular, or intravitreal steroid administration. 

Risk factors:

-Preexisting primary open-angle glaucoma

-Family history of glaucoma

-High myopia, diabetes mellitus

-History of connective tissue disease (especially rheumatoid arthritis). 

➧ Patients on chronic corticosteroid therapy can remain undiagnosed with an elevated IOP, which can result in glaucomatous optic nerve damage. 

➧ Steroid-induced IOP elevation typically occurs within a few weeks of beginning steroid therapy. In most cases, the IOP lowers spontaneously to the baseline within a few weeks to months upon stopping the steroid. In rare instances, the IOP remains elevated.

2-Topical anticholinergic or sympathomimetic dilating drops, TCA, MAOI, antihistamines, antiparkinsonian drugs, antipsychotic medications, and antispasmolytic agents:

Mechanism:

These medications produce pupillary dilation and precipitate an attack of acute angle-closure glaucoma in anatomically predisposed eyes that have narrow angles. 

3-Sulfa containing medications:

Mechanism:

Induce anterior rotation of the ciliary body causing angle-closure glaucoma. Typically, the angle-closure is bilateral and occurs within the first several doses of the sulfonamide-containing medication. Patients with narrow or wide-open angles are potentially susceptible to this rare and idiosyncratic reaction.

4-Ketamine: 

The effect on IOP varies. Early studies reported an increase in IOP after IV or IM administration of ketamine. Ketamine given after premedication with diazepam and meperidine does not affect IOP and IM administered ketamine may even lower IOP in children. 

5-Depolarizing muscle relaxants (Succinylcholine):

Causes a transient (4–6 min) but significant increase in IOP of (10 - 20 mm Hg). Although the mechanism is unclear, the increase is not attributable simply to induced muscle fasciculations. 

6-Large volume Local anesthetic:

Injecting a large volume (8–10 mL) of Local anesthetic into the orbit (e.g. peribulbar block).

7-Tracheal intubation:

Sympathetic cardiovascular responses to tracheal intubation. 

8- Caffeine

B) Drugs that ↓ IOP:

In general, CNS depressants lower IOP.

1-Intravenous anesthetics and volatile agents:

Mechanism:

Relax extraocular muscle tone, depress the CNS (i.e., the diencephalon), improve the outflow of aqueous humor, and lower venous and arterial blood pressures.

➧ e.g. thiopental, propofol, etomidate, decrease in IOP by 14 - 50 % have been noted.

➧ During controlled ventilation and normocapnia, volatile inhaled anesthetics reduce IOP in proportion to the depth of anesthesia.

2-Non depolarizing neuromuscular blocking drugs:

Either do not affect IOP or produce a slight decrease.

3-Benzodiazepines:

IV administered diazepam (0.15 mg/kg) and equipotent intravenous doses of midazolam (0.03 mg/kg).

4-Narcotic premedication:

Causes no change, or only a slight decrease, in IOP. 

5-Neuroleptanalgesia:

Produced by mixtures of (fentanyl and droperidol) decreases IOP by 12 % in normocapnic patients. 

6- Alcohol consumption:

This leads to a transient decrease in IOP.

7- Several pretreatment regimens:

➧ IV lidocaine (1.5 mg/kg) or sufentanil (0.05–0.15 µg/kg) given 3 - 5 min. before induction. 

➧ Oral administration of the centrally acting antihypertensive drug clonidine (5 µg/kg) 2 hrs before induction of anesthesia blunts the IOP response to intubation. 

➧ Intranasal administration of nitroglycerin

➧ β-adrenergic receptor blocking drugs

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Drugs Avoided in Patients with Renal Failure

Drugs Avoided in Patients with Renal Failure

➧ The excretion of water-soluble drugs and their active metabolites will be impaired. For drugs that are renally excreted the half-life increases slowly with deteriorating renal function until severe nephron loss at which point the half-life increases sharply with further reductions in renal function. Dialysis can only usually replace a small part of the excretory capacity of the healthy kidney. 

Antibacterial agents:

1-Injectable penicillin G or carbenicillin: may be associated with neuromuscular toxicity, myoclonus, seizures, or coma. 

2-Vancomycin 

3-Amphotericin 

4-Tetracyclines: except doxycycline (Vibramycin), have an antianabolic effect that may significantly worsen the uremic state in patients with severe disease. 

5-Aminoglycosides 

6-Imipenem/cilastatin (Primaxin): can accumulate in patients with chronic kidney disease, causing seizures if doses are not reduced. 

7-Sulphonamides 

8-Nitrofurantoin (Furadantin): has a toxic metabolite that can accumulate in patients with chronic kidney disease, causing peripheral neuritis. 

Anesthetic drugs:

1-Muscle relaxants:

➧ Depolarizing muscle relaxant:

-Suxamethonium: should be avoided if hyperkalemia is present. 

➧ Non-depolarising muscle relaxants (NDMRs): 

-NDMRs depends on the kidney for elimination)

-Gallamine: should be avoided 

-Pancuronium, pipecuronium, alcuronium, curare, and doxacurium: should be used with caution. Potentiation of neuromuscular blockade may occur in the presence of metabolic acidosis, hypokalemia, hypermagnesemia, or hypocalcemia and with medications such as aminoglycosides. Monitor neuromuscular blockade whenever possible. 

-Vecuronium and mivacurium: are safe to use in renal failure as only small percentages are excreted renally.

2-Opioids:

-Morphine: is metabolized in the liver to morphine-6-glucuronide which has about half the sedative effect of morphine with a markedly prolonged half-life. 

-Pethidine: is partially metabolized to norpethidine which is less analgesic and has excitatory and convulsant properties. 

-Tramadol and codeine: Metabolites can accumulate in patients with chronic kidney disease, causing central nervous system and respiratory adverse effects.

3-Inhalational agents:

➧ There is decreased elimination of the fluoride ions which are significant metabolites of enflurane, sevoflurane, and methoxyflurane which can worsen renal function, so these inhalational agents should be avoided especially if used at low flows. 

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs):

➧ NSAIDs should be avoided as all decrease renal blood flow and may precipitate complete renal failure. 

➧ Adverse renal effects of NSAIDs include acute renal failure; nephrotic syndrome with interstitial nephritis; and chronic renal failure.

➧ The risk of acute renal failure is three times higher in NSAID users than in non-NSAID users.

➧ Other adverse effects of NSAIDs include decreased potassium excretion, which can cause hyperkalemia, and decreased sodium excretion, which can cause peripheral edema, elevated blood pressure, and decompensation of heart failure.

➧ NSAIDs can blunt antihypertensive treatment, especially if beta-blockers, ACE inhibitors, or ARBs are used.

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