Induction

Induction is the process of putting a patient "to sleep." A general anesthetic is usually administered one of two ways: either with intravenous agents or with an inhalation agent via a mask. Patients with raised ICP can be nauseated and may be vomiting. In addition neonates may have congenital anomalies such as bowel atresia that puts them at risk for emesis during intubation and subsequent aspiration. Nausea and vomiting are indications for a rapid sequence induction and a rapid intubation (see below).

Preparation

In emergency cases or in hospitalized patients, an intravenous line may be in place and will facilitate induction. However, during elective surgical procedures in infants and children, an IV is usually not placed and the child will often go to sleep with a mask induction. Infants and young children under 18 months of age are frequently transported directly to the OR and undergo a mask induction. Children older than 18 months will likely have separation anxiety upon leaving their parents. If this is not treated with the appropriate premedication, all parties concerned, from the child to

Table 1. Potential sources of latex in the operating room

Latex-Containing Equipment

Bag on anesthesia circuit (gray). Bladder and black tubing of BP cuff.

Gloves (sterile and unsterile). Tourniquets used to place IV. Clip or neonatal pulse oximeter probe.

Syringes (seal). Stethoscope tubing. Band aids.

Rubber caps on medication vials.

Head strap for mask fit.

Rubber ports—IV tubing/buretrol diaphragm.

Nasopharyngeal airways.

Tape.

Pacifiers.

Latex-Free Options

Bag on anesthesia circuit (green).

Wrap tubing and patient's arm with gauze, or use a latex-free BP cuff with white tubing.

Latex-free gloves.

White latex-free tourniquet.

Plastic pulse oximeter probe (w/

balloons).

Latex-free syringes.

Plastic stethoscope.

Gauze with latex-free tape.

Use medications in glass vials or remove rubber seal to avoid piercing rubber stopper with needle.

Avoid use.

Tape over injection ports, inject via stop cocks only, or use adult IV tubing.

Plastic nasopharyngeal airways.

Latex-free tape.

the parents and the medical staff, will be faced with a distressed child, which greatly increases the difficulties during future procedures. In neurosurgical patients, premedication needs to be considered in the setting of increased ICP since drugs which decrease anxiety or treat pain may result in hypoventilation, increased PCO2, increased cerebral blood flow and potentially an increase in ICP. In the patient with elevated intracranial pressure who is lethargic, placement of an IV is often easily achieved without the need for medication.

Premedication

Two common methods of premedication include oral medications or intramuscular injections. The goal is to decrease both the patient's and parents' anxiety, as well as induce anesthesia in a safe manner. The parents' anxiety is often visibly decreased when they observe that their child is calm, happy and/or asleep after premedication. The potential rise in ICP due to premedication needs to be balanced with the disadvantages of a rough mask induction of an uncooperative and scared child. A successful mask induction, with or without premedication, involves establishing a rapport with the patient, although premedication will often increase their acceptance of the mask. Occasionally, an older child will request an IV and in these cases EMLA cream, a paste of local anesthetics, may be placed on the skin overlying a suitable vein, producing numbness of that area. Certainly, an IV may be placed in the child who is a preadolscent or a teenager, provided skilled personnel are available.

Table 2. Age appropriate vital signs

(/min)

Systolic BP (mm Hg)

Respiratory Rate

(/min)

Preterm

120-180

40-60

SS-60

Newborn

9S-14S

S0-70

3S-40

6 mos

110-180

60-110

2S-30

1 - 2 yrs

100-160

6S-11S

20-24

2 - 3 yrs

90-1S0

7S-12S

16-22

3 - 5 yrs

6S-13S

80-120

14-20

5 - 8 yrs

70-11S

92-120

12-20

9 - 12 yrs

SS-110

92-130

12-20

12 - 14 yrs

SS-10S

100-140

10-14

Used with permission from Preoperative evaluation. In: Charlotte Bell, ed. The Pediatric Handbook. 2nd ed. St. Louis: Mosby, 1997:11.

Used with permission from Preoperative evaluation. In: Charlotte Bell, ed. The Pediatric Handbook. 2nd ed. St. Louis: Mosby, 1997:11.

Induction Agents

A judicious choice of induction agents is required for the neurosurgical patient. Ketamine (1-3mg/kg) may result in raised ICP, although this may be blunted by early hyperventilation. Propofol (1-2mg/kg) and thiopental (3-5mg/kg) in the usual doses may result in hypotension, particularly in the hypovolemic patient (see Table 2 for normal values).

Etomidate (0.2- 0.3 mg/kg) maintains stable hemodynamics without adversely affecting ICP, and is the sedative/hypnotic of choice in a trauma patient with a suspected head injury. Following the administration of the sedative/hypnotic, either succinylcholine (1-2mg/kg) or rocuroniun (1-1.2 mg/kg) is recommended to facilitate rapid intubation. Succinylcholine can raise ICP, an effect blunted by a defasciculating dose of a nondepolarizing muscle relaxant. The clear advantage of succinylcholine remains its extremely short duration of action, a pharmacokinetic property unavailable in a nondepolarizing agent. There are many absolute and relative contraindications for the use of succinylcholine, but its utility in the rapid acquisition of an airway in an emergent situation makes it the current standard. In a patient with evidence of a previous stroke or an evolving neurological deficit, the use of succinylcholine can result in hyperkalemia (Table 3).

Rapid Sequence Induction

A rapid sequence induction technique consists of preoxygenation, and the administration of intravenous sedatives and paralytic agents, during which cricoid pressure is applied and endotracheal intubation is accomplished. A modified rapid sequence technique may be helpful in a combative, uncooperative child who will not accept preoxygenation. In the modified technique, gentle mask ventilation is delivered in the presence of cricoid pressure. Cricoid pressure is applied by pushing the circular cricoid cartilage, the only circumferential cartilage in the trachea, aginst the esophagus. The aim of this maneuver is to prevent stomach contents from entering the airway by obstructing its path to the pharynx. When effective preoxygenation has not been achieved, a modified rapid sequence intubation technique avoids oxygen desaturation.

Table 3. Drug recommendations for endotracheal intubation

Type of Drug

Medication

Dose (mg/kg)

Advantages

Disadvantages

Induction agent

Barbituate

Thiopental

3-5 mg/kg

Decreases CBF

Hypotension

Hypnotic

Propotol

1 - 2 mg/kg

Decreases CBF

Hypotension

Hypnotic

Etomidate

0.2-0.3 mg/kg

Stable hemodynamics

Sedative/ Analgesic

Ketamine

1 - 3 mg/kg

Stable hemodynamics

Raises ICP

Muscle relaxant

Depolarizing

Succcinyl-choline

1 - 2 mg/kg

Rapid onset (60 sec)

Hyperkalemia raises ICP

Nondepolarizing

Rocuronium

1 -1.2 mg/kg

Quick onset (90 sec)

Intermediate duration

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