Practical conductof

General AnesthesiaPart 2

Prepared byDr. Mahmoud Abdel-Khalek

Jan 2015

Induction of Anesthesia

1. Inhalational Induction: – Sevoflurane, isoflurane

2. Intravenous Induction:– Thiopental– Propofol– Ketamine

Inhalational Induction

Complications and Difficulties

Slower induction of anesthesia Problems particularly during stage 2 of anesthesia e.g. Airway

obstruction, bronchospasm, Laryngeal spasm, hiccups Environmental pollution

IV Induction Suitable for most routine purposes and avoids

many of the complications associated with the inhalational technique

most appropriate method for rapid induction of the patient undergoing emergency surgery

Complications and difficulties

Regurgitation and Vomiting– Trendelenburg position and suction

Intra-arterial injection of thiopental– Pain, blanching in the hands as a result of crystal

formation in capillaries– Cannula left in place, 40mg papverine + LA,

sympathectomy Perivenous injection

– Blanching, pain, tissue necrosis– Hyaluronidase to speed dispersal

Cardiovascular depression– Elder, Hypovolemic, Untreated hypertensive– ↓ dose and speed, 1000 mL crystalloid, Ephedrine 3- 12

mg

Complications and difficulties

Respiratory depression– Slow injection, assist ventilation if necessary

Histamine release– Especially with thiopental, maybe severe reaction– Fluids., antihistamines, epinephrine

Porphyria– Barbiturates

Other complications– Pain on injection, hiccup, muscular movements– Lidocaine 10- 40 mg used to reduce the pain on injection

Airway Management

Following induction, airway is secured employing any of the following:– Face Mask– LMA– ETT

Relaxant anesthesia for intubation• After IV or inhalational induction of anesthesia, the

short-acting depolarizing muscle relaxant succinylcholine may be used to provide relaxation for tracheal intubation.

• After loss of consciousness, the patient breathes 100% oxygen or 50% nitrous oxide in oxygen and succinylcholine is administered in a dose of 1–1.5 mg kg–1

• Assisted ventilation is maintained via the face mask until muscle relaxation occurs and laryngoscopy and intubation are performed

• Inhalational anesthesia may be continued with manual ventilation until the effects of the relaxant have ceased

Muscle relaxants: Depolarizing muscle relaxant

Muscle relaxants: Depolarizing muscle relaxant

Maintenance of Anesthesia

Anesthesia may be continued using either– Intravenous anesthetic agents (TIVA)– Inhalational agent and spontaneous breathing– Inhalational agent and mechanical ventilation

to achieve the components of the familiar anesthetic triad of sleep, neuromuscular relaxation and analgesia.

Inhalational anesthesia with spontaneous ventilation

This is an appropriate form of maintenance for– superficial body surgery e.g. Drainage of an abscess– minor procedures which produce little reflex or painful

stimulation e.g. Fracture reduction– operations for which profound neuromuscular blockade

is not required e.g. Dilatation and curettage The “Anesthesia Machine” is used to deliver

inhalational anesthetics to the patient through any of the following:– Face Mask– Endotracheal tube (ET Tube)– Laryngeal Mask Airway (LMA)

Technique of inhalational anesthesia with spontaneous

ventilation N2O+ O2+ Volatile agent+ Spontaneous breathing The volatile agent used in an inspired concentration of:

– isoflurane 1–2%, sevoflurane 2–3%, or desflurane 3–6% Control of the depth of anesthesia by varying the inspired

concentration of volatile agent This rapid control is one of the main advantages of

inhalational anesthesia The signs of inadequate depth of anesthesia include

tachypnoea, tachycardia, hypertension and sweating

Anaesthesia using neuromuscularblocking drugs

As an alternative to deep anaesthesia with spontaneous ventilation and volatile agents leading to multisystem depression, the triad of sleep, suppression of reflexes and muscle relaxation may be provided separately with specific agents

The use of a neuromuscular blocking agent provides muscle relaxation, permitting lighter anaesthesia with less risk of cardiovascular depression

Indications– The technique is appropriate for major abdominal,

intraperitoneal, thoracic or intracranial operations– Prolonged operations in which spontaneous ventilation

would lead to respiratory depression– Operations in a position in which ventilation is impaired

mechanically

NMBD’s (Muscle Relaxants)

Ventilation Settings

Thank you

Positioning for Surgery

Goals of proper position

To maintain patient’s airway and avoid

constriction or pressure on the chest cavity

To maintain circulation

To prevent nerve damage

To provide adequate exposure of the operative

site

To provide comfort and safety to the patient

Common Positions of for Surgery

Supine

Most common with the least amount of harm Placed on back with legs extended and uncrossed at the

ankles Arms either on arm boards abducted <90* with palms up or

tucked (not touching metal or constricted) Spinal column should be in alignment with legs parallel to

the OR bed– Head in line with the spine and the face is upward– Hips are parallel to the spine

Padding is placed under the head, arms, and heels with a pillow placed under the knees

Safety belt placed 2” above the knees while not impeding circulation

Prone Anesthetized supine, usually on the stretcher, prior to turning Turning is synchronized and supported face down, resting on

the abdomen and chest Chest rolls x2 placed lengthwise under the axilla and along

the sides of the chest from the clavicle to iliac crests (to raise the weight of the body off of the abdomen and thorax)

One roll is placed at the iliac or pelvic level Arms lie at the sides or over arm boards Head is face down and turned to one side with accessible

airway Forehead, eyes and chin are protected Padding to bilateral arms and under

knees Pillow placed under bilateral feet Female breasts and male genitalia must

be free from pressure and torsion Safety strap placed 2” above knees

Lateral

Anesthetized supine prior to turning Shoulder & hips turned simultaneously to prevent torsion of

the spine & great vessels Lower leg is flexed at the hip; upper leg is straight Head must be in cervical alignment with the spine Breasts and genitalia to be free from torsion and pressure Axillary roll placed to the axillary area of the downside arm

(to protect brachial plexus) Padding placed under lower leg, to ankle and foot of upper

leg, and to lower arm (palm up) and upper arm Pillow placed lengthwise between

legs and between arms (if lateral arm holder is not used)

Stabilize patient with safety strap and silk tape, if needed

Trendelenburg The patient is placed in the supine position while

the OR bed is modified to a head-down tilt of 35 to 45 degrees resulting in the head being lower than the pelvis

Arms are in a comfortable position – either at the side or on bilateral arm boards

The foot of the OR bed is lowered to a desired angle

Velcro adhesive MUST be checked prior to placing the patient on the table padding

Surgical tape may be indicated to assure the table padding is fixed to the table to prevent pad slippage

Trendelenburg

In addition to a safety strap, strips of 3” tape may be used to assist with holding the patient in the proper position

Used for procedures in the lower abdomen or pelvis – Enables the abdominal viscera to be moved

away from the pelvic area for better exposure

Reverse Trendelenburg

The entire OR bed is tilted so the head is higher than the feet

Used for head and neck procedures Facilitates exposure, aids in breathing and

decreases blood supply to the area A padded footboard is used to prevent the patient

from sliding toward the foot

Fowler’s Position (Sitting/Lawnchair/Beachchair)

Patient begins in the supine position Foot of the OR bed is lowered slightly, flexing the knees,

while the body section is raised to 35 – 45 degrees, thereby becoming a backrest

The entire OR bed is tilted slightly with the head end downward (preventing the patient from sliding)

Feet rest against a padded footboard Arms are crossed loosely over

the abdomen and taped or placed on a pillow on the patient’s lap

A pillow is placed under the knees. For cranial procedures, the head is

supported in a head rest and/or with sterile tongs

This position can be used for shoulder or breast reconstruction procedures

Jackknife Modification of the prone position The patient is placed in the prone position on the OR bed

and then inverted in a V position The hips are over the center break of the OR bed between

the body and leg sections Chest rolls are placed to raise the chest Arms are extended on angled arm boards with the elbows

flexed and the palms down A pillow is placed under the ankles to free the feet and toes

of pressure

The OR bed leg section is lowered, and the OR bed is flexed at a 90 degree angle so that the hips are elevated above the rest of the body

Used in gluteal and anorectal procedures

Lithotomy With the patient in the supine position, the legs are raised

and abducted to expose the perineal region The patient’s buttocks are even with the lower break in the

OR bed (to prevent lumbosacral strain) The arms are placed on padded arm boards, tucked at the

sides, or placed across the abdomen The legs and feet are placed in stirrups that support the

lower extremities Stirrups should be placed at an even height The legs are raised, positioned, and lowered slowly and

simultaneously, with the permission of the anesthesia care provider

Adequate padding and support for the legs/feet should eliminate pressure on joints and nervous plexus

The position must be symmetrical The perineum should be in line with the longitudinal axis of

the OR bed The pelvis should be level The head and trunk should be in a straight line

High Lithotomy Frequently used for procedures that requires a vaginal or

perineal approach The patient is in the supine position with legs raised and

abducted by stirrups Once the feet are positioned in stirrups, the footboard is

removed and the bottom section of the OR bed is lowered It may be necessary to bring the

patient’s buttocks further down to the edge of the OR bed break

Coordination with the anesthesia care provider is necessary to ensure that the patient’s hands/fingers areprotected from crushing prior to lowering of the bottom of the OR bed section

Low Lithotomy All of the positioning techniques used to high

lithotomy apply Placed in supine position with the legs raised and

abducted in crutch-like or full lower leg support stirrups

The angle between the patient’s thighs and trunk is not as acute as for the high lithotomy position

Used in vaginal procedures

Effects of Positioning - Obese Patients

Supine:– Normal blood flow may be impeded due to compression of

vena cava and aorta by abdominal contents– Impairs diaphragmatic movement and reduces lung capacity

Trendelenburg:– Tolerated less well than supine– Added weight of abdominal contents on the diaphragm may

lead to atelectasis and hypoxemia Prone:

– Problematic– Requires additional support and monitoring of the patient and

pressure on the abdomen– Ventilation may be markedly more difficult

Lateral:– Well tolerated– Correct sizing and placement of axillary roll is important– Ensure that pendulous abdomen does not hang over side of OR

bed Head-Up: (Reverse Trendelenburg/Semi-recumbent)

– Most safe– Weight of abdominal contents unloaded from diaphragm– Use of well-padded footboard to prevent sliding

Adverse effects of each position The lithotomy position

– Nerve damage on the medial or lateral side of the leg from pressure exerted by the stirrups, which must be well padded.

– Care must be taken to elevate both legs simultaneously so that pelvic asymmetry and resultant backache are avoided.

– The sacrum should be supported and not allowed to slip off the end of the operating table.

The lateral position– Asymmetrical lung ventilation– Care is required with arm position and IV infusions– The pelvis and shoulders must be supported to prevent

the patient from rolling either backwards (with a risk of falling from the table) or forwards into the recovery position.

Adverse effects of each position The prone position

– Abdominal compression which may result in ventilatory and circulatory embarrassment. To prevent this, support must be provided beneath the shoulders and iliac crests.

– Excessive extension of the shoulders should be avoided. – The face, and particularly the eyes, must be protected

from external pressure or trauma. – The tracheal tube must be secured firmly in place as it is

almost impossible to reinsert it with the patient in this position

The Trendelenburg position– Upward pressure on the diaphragm because of the

weight of the abdominal contents. – Damage to the brachial plexus may occur as a result of

pressure from shoulder supports, especially if the arms are abducted

Adverse effects of each position The sitting position

– requires careful support of the head– Venous pooling and resultant cardiovascular instability

may occur The supine position

– carries the risk of the supine hypotensive syndrome during pregnancy or in patients with a large abdominal mass

Reversal of muscle relaxation At the end of surgery, residual neuromuscular

blockade is antagonized and spontaneous ventilation should begin before the tracheal tube is removed and the patient awakened

Residual neuromuscular blockade is antagonized with– neostigmine 2.5–5 mg (0.05–0.08 mg kg–1 in children)– Atropine 1.2 mg or glycopyrronium 0.5 mg (in adults) to

counteracts the muscarinic side- effects of the anticholinesterase

Resumption of spontaneous ventilation should occur and assured by monitoring the end-expired PCO2

Tracheobronchial suction (see below) has the beneficial side-effect of stimulating respiration if used at this stage.

Anticholinesterases

Anticholinergics

Anticholinergics

Emergence and recovery After completion of surgery, anesthetic agents are withdrawn and oxygen 100% is delivered. Following removal of the tracheal tube or LMA,

the patient’s airway is supported until respiratory reflexes are intact.

The patient’s muscle power and coordination are assessed by testing hand grip, tongue protrusion or a sustained head lift from the pillow in response to command.

Return of adequate muscle power must be ensured before the patient leaves theatre.

Emergence and recovery Full monitoring of the patient should not be discontinued

before recovery of consciousness. The patient is then ready for transfer from the operating

table to a bed or trolley. Oxygen is delivered by face mask during transport, and

further recovery takes place in a recovery area of theatre or in the recovery ward

The lateral recovery position is adopted unless the anesthetist is satisfied that this is unnecessary.