1. General Anesthesia Part 2
Practical conduct of
General Anesthesia Part 2
Prepared by
Dr. Mahmoud Abdel-Khalek
Jan 2015

2. Induction of Anesthesia
1. Inhalational Induction:
Sevoflurane, isoflurane
2. Intravenous Induction:
Thiopental
Propofol
Ketamine
The proposed procedure should be explained to the patient before starting. A technique using a cupped hand around the fresh gas delivery tube may be preferred for young children, otherwise a face mask is used. The mask or hand is introduced gradually to the face from the side; the use of a transparent perfumed mask can render the procedure less unpleasant. While talking to the patient and encouraging normal breathing, the anesthetist adjusts the mixture of the fresh gas flow and observes the patient’s reactions. Initially, nitrous oxide 70% in oxygen is used and anesthesia is deepened by the gradual introduction of increments of a volatile agent, e.g. sevoflurane which can be increased up to an inspired concentration of 6%. Maintenance concentrations of isoflurane (1–2%) or sevoflurane (2–3%) are used when anesthesia has been established.

3. Inhalational Induction
The proposed procedure should be explained to the patient before starting. A technique using a cupped hand around the fresh gas delivery tube may be preferred for young children, otherwise a face mask is used. The mask or hand is introduced gradually to the face from the side; the use of a transparent perfumed mask can render the procedure less unpleasant. While talking to the patient and encouraging normal breathing, the anesthetist adjusts the mixture of the fresh gas flow and observes the patient’s reactions. Initially, nitrous oxide 70% in oxygen is used and anesthesia is deepened by the gradual introduction of increments of a volatile agent, e.g. sevoflurane which can can be increased up to an inspired concentration of
6%. Maintenance concentrations of isoflurane (1–2%) or sevoflurane (2–3%) are used when anesthesia has been established
Complications and Difficulties
Slower induction of anesthesia
Problems particularly during stage 2 of anesthesia e.g. Airway obstruction, bronchospasm, Laryngeal spasm, hiccups
Environmental pollution

4. 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
It is the most appropriate method for rapid induction of
the patient undergoing emergency surgery, in whom
there is a risk of regurgitation of gastric contents.
Doses of the common i.v. agents are shown in
Table The induction dose varies with the patient’s
weight, age, state of nutrition, circulatory status, premedication
and any concurrent medication.

5. 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 mg

6. 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 mg used to reduce the pain on injection

7. Airway Management
Following induction, airway is secured employing any of the following:
Face Mask
LMA
ETT

8. 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

9. Muscle relaxants: Depolarizing muscle relaxant

10. Muscle relaxants: Depolarizing muscle relaxant

11. 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.

12. 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)
Control of the depth of anesthesia to achieve
adequacy without overdose by varying the inspired
concentration of volatile agent requires constant
assessment of the patient’s reaction to anesthesia
and surgery. 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.

13. 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
Control of the depth of anesthesia to achieve
adequacy without overdose by varying the inspired
concentration of volatile agent requires constant
assessment of the patient’s reaction to anesthesia
and surgery. 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.

14. Anaesthesia using neuromuscular blocking 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

15. NMBD’s (Muscle Relaxants)

19. Ventilation Settings

20. Thank you

21. 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

22. Common Positions of for Surgery

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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 are
protected from crushing prior to
lowering of the bottom of the OR bed
section

33. 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

34. 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

35. 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.

36. 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

37. 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

38. 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.

39. Anticholinesterases

40. Anticholinergics

41. Anticholinergics

42. 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.

43. 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.