10 Anaesthesia for aesthetic surgery

There is evidence in the literature to suggest that plastic surgery originated in India more than 2500 years ago and it is believed that an ancient Indian surgeon, Sushruta, performed a rhinoplasty, the oldest plastic surgery operation, in 600 BC¹. In ancient times, amputation of the nose was performed as a punishment for committing adultery, amongst other crimes. This explains the need for nasal reconstruction during that period. Sushruta, known as the ‘father of Indian plastic surgery’, wrote Sushruta Samhita, a compendium written in Sanskrit about most advanced surgical practices prevalent at that time. As well as introducing an ethical code, he highlighted all of the basic principles of plastic surgery, such as pedicle flap techniques, repair of ear lobe defects, and repair of both traumatic and congenital cleft lips. In addition he classified burns, described surgical instruments, the practice of mock operations, cadaveric dissection, and used wine to dull the pain of surgical incisions.

Aesthetic or cosmetic surgery on the face is performed to improve the appearance of the face and is one of the fastest growing medical practices in the United Kingdom. An increasing number of women as well as men are opting for cosmetic surgery to address dissatisfaction with their body image². Physical appearance plays an important role in how we are perceived by others. Each individual has their own perceptions as to what constitutes beauty. This in turn is influenced by current standards and fashions in the society within which they live^{3  –5}. These issues have led patients to consider aesthetic surgery to enhance their self-esteem and attractiveness. As demands for aesthetic surgery increase, it becomes important to understand why patients are prepared to undergo invasive aesthetic surgery. Aesthetic surgery is performed both with and without surgical instruments, and sometimes both modalities are used.

These procedures range from minor to major procedures and modality of anaesthesia (local anaesthesia [LA] with or without sedation or general anaesthesia [GA]) depends on the planned surgery. These procedures are both surgical as well as non-surgical. Surgical procedures may include reconstructive plastic surgery and removal of skin growths, scar revision, forehead lift, corrective eyelid surgery, facial reconstruction (facelift both laser and open, facial injuries), liposuction, jaw surgery (orthognathic surgery), corrective nose surgery (rhinoplasty), and ear surgery (otoplasty). Non-surgical procedures include the removal of pigmented lesions, tattoos, birth marks, treatment of vascular lesions, and botox injections. In adults, these procedures are usually carried out under LA but GA is invariably necessary for children. This chapter concentrates primarily on the anaesthetic management of aesthetic procedures requiring anaesthesia and the involvement of an anaesthetist.

Anaesthesia for aesthetic surgery on the face poses many challenges for the anaesthetist due to the range of surgical procedures performed. Careful manipulation of physiology to achieve optimal surgical conditions, attention to anatomical details in securing the airway device, and close cooperation between anaesthetist and surgical team are vital. Anaesthetic techniques for aesthetic surgery may involve infiltration of LA agent, regional anaesthesia (RA) with or without intravenous sedation, or GA. A thorough preanaesthetic assessment is required to determine if the patient is suitable for GA, sedation, LA, or a combination of these. Any pre-existing medical condition should be optimized before embarking on anaesthesia and surgery. Patients who wish to have their surgery under LA, with or without sedation, should be prepared as for GA. This will facilitate intervention should the LA be inadequate. For example, the patient may be unable to lie still enough throughout the procedure or indeed become increasingly anxious, intolerant, or restless. The assessment and pre-optimization of the oral and maxillofacial surgery patient is discussed in detail in Chapter 2.

The profile of patients presenting for aesthetic surgery differs from that of other surgical patients because these patients are generally fit and healthy (American Society of Anesthesiologists [ASA] class 1 and 2). Anaesthetists should be aware of the psychological issues that surround these patients. The patient’s expectations often go beyond what is possible surgically and consequently changes in their physical appearance alone may fail to fulfil their needs and even lead to deterioration in their psychological status. Patient’s needs and expectations have to be explored and evaluated carefully before undertaking any surgical aesthetic procedures. The presence of an active psychotic disorder is commonly thought to contraindicate cosmetic surgery^{3  ,4}.

The basic requirements for all elective surgical procedures are that the patients be safe, comfortable, and stable. It is also desirable for them to be immobile and not too talkative, especially when the operative site is the face. LA by infiltration or nerve block has many advantages in aesthetic surgery and is often an ideal approach to painless surgery. It is important to understand the pharmacological properties of LA agents and other agents (see Chapters 7 and 21) used during LA. Readers are advised to read an authentic textbook of pharmacology for more details⁷.

LA agents reversibly inhibit signal transmission in the nerve by blocking sodium influx via protein-based sodium channels⁶. The agents used are manufactured as water-soluble hydrochloride salts. In an aqueous solution, each LA has a unique fixed dissociation constant (pKa) that determines the equilibrium between the charged cation and the uncharged base. It is the lipid-soluble uncharged base that freely diffuses through the lipid bilayer of neurons. After diffusing through the neuronal lipid bilayer, the LA molecule again dissociates into its basic and cationic forms. The charged cation then enters the protein-based sodium channel and renders the channel impermeable to sodium, thus preventing the propagation of action potentials and impulse conduction⁸. With time, depending on the pH, the lipid solubility, and protein binding, the LA diffuses out of the channel rendering the neurons once again susceptible to depolarization.

All LAs in clinical use consist of a benzene ring linked to a hydrocarbon chain by an ester or amide bond. Tetracaine, procaine, 2-chloroprocaine, and cocaine are ester-linked LAs. Amide-linked LAs include bupivacaine, mepivacaine, prilocaine, etidocaine, ropivacaine and lidocaine. Allergic reactions are more common with ester LAs. Allergic reactions to amides are rare. Esters such as benzocaine and procaine, break down to structures similar to p-aminobenzoic acid (PABA), a common component of cosmetics and sunscreens and should be avoided in patients with known sensitivity to such compounds.

The lipid solubility of LAs determines LA potency and is pH dependent. A high pH favours increased lipid solubility, anaesthetic potency, and speed of onset. Substitutions on the benzene ring or tertiary amine portion of the LA molecule alter its pKa value, lipid solubility, and protein binding, determining the speed of onset, potency, and duration of action, respectively.

Commonly used LAs in clinical use are poorly soluble in water; they are prepared as hydrochloride salts with commercial solutions having a pH in the range of 4 to 6. The addition of sodium bicarbonate can increase the rate of onset of some LAs by increasing the amount of lipid-soluble uncharged base, which readily penetrates neural tissue. It may also decrease the associated pain on injection as a result of neutralizing the pH. In practice, 1 ml of 8.4% sodium bicarbonate can be added to a 30 ml vial of 1% lidocaine or 0.2 ml can be added to a 30 ml vial of 0.25% bupivacaine. Adding further bicarbonate will result in precipitation of the LA.

Multidose vials of LA contain antimicrobial preservatives and can have potentially cytotoxic effects. The most frequently used antimicrobials are methyl-, ethyl-, and propyl-parabenzoates. Sodium ethylenediaminetetraacetic acid (EDTA), which has ion chelating properties, and anti-oxidants, are added to commercially available LAs to scavenge divalent cations and prevent oxidation thus retarding LA degradation. Preservative-free preparations are available and recommended for patients suspected of having allergy with any of these preservatives.

Low concentrations of the vasoconstrictor epinephrine can be added to LAs. This has the effect of prolonging the duration of anaesthesia and decreasing systemic absorption, thus minimizing the risk of attaining toxic blood levels. The addition of 5 mcg epinephrine to 1ml of LA produces the commonly used 1:200 000 concentration. It must be used with caution in patients known to suffer from coronary vascular disease.

By catalysing the hydrolysis of hyaluronic acid, a major constituent of the interstitial barrier, hyaluronidase lowers the viscosity of hyaluronic acid, thereby increasing tissue permeability. It is commonly used in diluted form during liposuction but the exact recommended dose is not clear⁹. However, in clinical practice it is not unusual to see 1500 IU mixed with 1000 ml of 0.9% sodium chloride.

RA implies blockade of peripheral nerves or nerve. The sensory nerve supply of the face is complex (see Chapter 6) and multiple nerves may need to be blocked to achieve good anaesthesia. There are relatively few absolute indications for RA in aesthetic surgery, as opposed to merely being an option. In general terms, RA techniques can be advantageous by reducing the overall stress of surgery and anaesthesia, providing better postoperative pain control, decreasing the incidence of postoperative nausea, vomiting, and dysphoria, and possibly improving wound healing. There can also be compelling reasons for avoiding GA in unfit or high-risk patients. Alternatively supplementing GA with some form of RA can give ideal conditions for surgery. Although safer than GA, RA is not without its complications. Complications of RA (see Chapters 7 and 21) include neurotoxicity, allergy, and systemic toxicity, the details of which can be found in any standard pharmacology or anaesthetic textbook.

Modern anaesthetic medications are extremely short acting and have minimal side effects. Fast emergence and early discharge have become normal practice. Conscious sedation describes a state that allows patients to tolerate unpleasant procedures while maintaining adequate cardiorespiratory function and the ability to respond purposefully to verbal commands and tactile stimulation, and is described in detail in Chapter 8. Conscious sedation allows patients to tolerate, and sometimes forget, unpleasant procedures by relieving anxiety, discomfort, or pain. Too much sedation can rapidly convert conscious sedation into a state of GA and expose the patient to the risks associated with an unsecured airway and a lack of protective reflexes. This is the reason why conscious sedation should only be employed in the presence of a competent trained clinician, invariably an anaesthetist, in an environment where the patient’s vital signs can be continuously monitored and where resuscitation equipment is immediately available.

The assessment and preoptimization of the oral and maxillofacial surgery patient is discussed in detail in Chapter 2. GA has been popular for major aesthetic surgery but RA and conscious sedation are increasingly popular. The proposed surgery can dictate the anaesthetic modality. For example, rhinoplasty is almost always done under GA although LA has been advocated, whereas most adult patients will accept LA and conscious sedation for a pinnaplasty. Not all aesthetic surgical procedures can be performed under LA or RA. Lengthy operations and having to maintain uncomfortable positions for a prolonged period of time can deter even the most motivated of patients. Concomitant sedation may help alleviate this discomfort but should be used judiciously. Oversedation must be avoided, especially in the elderly. Disinhibition, agitation, dysphoria, and unconsciousness can result from excessive sedation¹⁰. In terms of cardiovascular stability and recovery from anaesthesia, there are distinct advantages of using a target-controlled infusion of propofol or remifentanyl to sedate patients. If the surgery is to be carried out under LA, the anaesthetist must ensure that the patient understands the procedure and its risks. In addition they must be capable of cooperating, have no known allergies to the proposed LA agents, and be able to maintain the required operative position without undue discomfort and hazard for the duration of surgery.

Brow lift is the resuspension of the brows and elimination of upper facial rhytids to help give a youthful appearance of the upper face. It usually has better cosmetic results when combined with upper blepharoplasty. Blepharoplasty is the surgical rejuvenation of the periorbital region to eliminate the tired and aged appearance of the eyes. Blepharoplasty involves resection of skin, orbicularis muscle, and fat.

Blepharoplasty as an isolated procedure is often performed under LA with or without sedation. Patient cooperation may be needed in opening and closing the eye during the procedure to ensure good results. This procedure can also be done by carbon dioxide laser but must be done under safety parameters of eye protection and fire and burn prevention (see below).

Infiltration of LA is performed carefully avoiding haematoma and injection into the muscle. The injection is usually performed by the surgeon. Occasionally GA is required on indication or at the patient’s request.

Combined brow lift and blepharoplasty is routinely performed under GA. A simple laryngeal mask airway (LMA) anaesthesia following intravenous induction and spontaneous ventilation with inhalational agent is commonly employed.

Rhinoplasty is the surgical manipulation of the nasal form for aesthetic and or functional improvement. When surgery is combined with nasal septal surgery it is called septorhinoplasty. Patients usually request reduction of nasal hump, reduction, augmentation, or improved tip definition. The exact surgical procedures from surgical perspective are different and it is either performed as open or closed technique depending on the patient’s requirements and the surgeon’s preference. An open approach utilizes a transcolumellar incision to allow elevation of a nasal skin flap, degloving the lower alar cartilages for direct and wide exposure of the nasal frame. The closed approach utilizes intercartilaginous, intracartilaginous, infracartileginous, rim, hemitransfixion, and transfixion incisions.

Although septoplasty can be performed under LA, rhinoplasty or septorhinoplasty is routinely preformed under GA. The essential surgical requirements include patient immobility, clear surgical field (minimum bleeding), and smooth recovery. GA with an oral endotracheal tube or flexible LMA with either spontaneous or controlled ventilation can be used. LA and packing of nostrils are also used with GA.

It is important to know the anatomy and sensory nerve supply of the face (see Chapter 6) before embarking on LA. The nose is supplied by the ophthalmic division and maxillary division of the trigeminal nerve. The skin of the nose is supplied by the supratrochlear branch of the frontal nerve of the ophthalmic; the anterior ethmoidal branch of the nasociliary (ophthalmic); and the infraorbital branch of the maxillary. The fifth nerve provides the sensory supply to the anterior one-third of the septum, and the lateral walls are innervated by the anterior ethmoidal branch of the nasociliary nerve. The long sphenopalatine nerves from the sphenopalatine ganglion, innervates the posterior two-thirds of the septum and lateral walls.

The nasal cavities are packed with gauze soaked in 4–5% cocaine. Paste is also applied to the area of sphenopalatine ganglion behind the middle turbinate. The mucosa will become avascular as a result of the vasoconstrictor properties of cocaine. Cocaine is a powerful vasoconstrictor so adrenaline is not necessary. Alternatively, Moffett’s solution, a mixture of 2 ml of 8% cocaine hydrochloride, 2 ml of 1% sodium bicarbonate, and 1 ml of 1 in 200 000 adrenaline solution is used.

Blockade of the sphenopalatine ganglion gives a good surgical field. If the septum is to be operated on, 2 ml of 1% lidocaine with adrenaline should be injected into the columella and base of the septum as this area is covered by squamous epithelium which will not absorb the topically applied agents. In fact, use of the combination may precipitate cardiac arrhythmias and should be avoided.

GA for rhinoplasty can include total intravenous anaesthesia (TIVA) with remifentanyl which allows greater flexibility in quickly modulating the blood pressure by altering the rate of the remifentanyl infusion. Alternatively, conventional intravenous induction with propofol followed by inhalational agents will suffice. Maintaining a head-up posture during surgery and recovery reduces venous congestion and bleeding. Recent trends have been to use a classic or flexible LMA for rhinoplasty. It must be remembered that the laryngeal mask does not protect the airway in an anaesthetized patient and consequently many anaesthetists still prefer to use a cuffed endotracheal tube (Ring–Adair–Elwyn [RAE] tube). The endotracheal tube or LMA must be taped to the patient’s chin to keep it out of the surgeon’s field of vision. The usual perioperative precaution for surgery in the head and neck region applies. A significant blood pooling can occur in the nasopharyngeal area when nasal osteotomies are used to narrow or straighten the nasal dorsum. A throat pack is used to protect the airway from blood and to reduce the amount of blood which can enter the oesophagus and then into the stomach. Any ingested blood in the stomach is a well-known factor for postoperative nausea and vomiting. Attention must be paid to removing the throat pack at the end of procedure. Even though the throat pack is soaked with saline, it is still very abrasive to the oesophageal mucosa and the patient usually complains of a sore throat postoperatively. The application of a surgical splint or dressing of the nose is an art and varies with surgeon’s preference. Most surgeons also pack both nostrils. The patient should be only allowed to wake up when the splint has stiffened and contoured. Postoperative recovery should be smooth and excessive coughing will increase bleeding. Equally, the patient must be fully awake before the extubation as application of a face mask will be very difficult, especially when nostrils are packed. Postoperative pain is not a major problem but mouth dryness due to mouth breathing may be distressing.

Surgical facelift is performed to reduce facial folds and wrinkles to create a more youthful appearance. Surgical facelift involves removing excess fatty tissue of the face, tightening of underlying facial muscles, and smoothing facial skin. Facelift surgery is categorized as full, lower, or mid or mini facelift. Incisions are commonly made above the hairline following the natural facial creases (e.g. the line where the ear meets the side of the face), so that any scarring forming after the face lift will remain unseen. Facial skin is separated from the underlying tissue. Excess fat and skin are removed, and the surrounding muscles are tightened to improve the contours and appearance of the patient’s face. Redundant skin is excised. The skin is then repositioned with stitches or staples, and the treated area is wrapped in bandages. Facelift surgery may be combined with forehead lift, upper and/or lower blepharoplasty, removal of submental or submandibular fat, and liposuction. The procedure is also combined occasionally with septorhinoplasty.

Most patients are usually aged 45–65 years and they are generally fit and well. Often simple facelift surgery can be performed using LA with or without sedation but GA is always an option. Patients must be assessed before GA. The procedure may be unpredictable, especially if the facelift is combined with other surgical procedures. The patient’s head is usually nearer the anaesthetic machine and easy access to an intravenous access must be ensured. TIVA or propofol induction, followed by inhalational agent is suitable. Securing the airway is an important factor. The airway can be maintained with a reinforced LMA or an endotracheal tube (RAE). The usual perioperative precautions for surgery in the head and neck region apply. The use of LA infiltration helps. To avoid hypothermia, warming blanket should be used. The continued use of muscle relaxant is avoided if intraoperative testing of VII nerve function is intended.

Liposuction or lipoplasty is a body contouring procedure which is done in almost any area of the body, including the face. The subcutaneous fat is aspirated via a small skin incision with a specialized blunt-ended cannula. The most common method of liposuction is the use of a power suction canister or spring-loaded syringes especially for the face. The area of liposuction is usually instilled with saline mixed with LA, epinephrine, and other adjuvants. Fibrous area is difficult to suction and is less conducive to the spread of the tumescent fluid. An ultrasonic suction device can help liquefy the fat and makes subsequent suction of fat easier. However, an ultrasonic device can increase seroma formation and produce heat injury to the skin. The suction cannulae and syringes vary in sizes and lengths. An appropriate sized cannula is inserted in the least visible area through the skin incision and is moved backwards and forwards in repetitive fashion to break the fat tissue and then suction is applied.

Patients are usually fit and well but adequate anaesthesia is essential. Liposuction involving a small area can be performed under LA with or without sedation. However, if area involved is larger, GA may be necessary. The use of LMA after intravenous induction, spontaneous ventilation, and maintenance with a modern inhalalational anaesthetic agent usually suffice. Alternatively TIVA may be used. Postoperative pain is not a major problem and simple analgesics are required.

Dermabrasion is used to minimize the appearance of fine wrinkles, acne, scars, and sun damage by carefully scraping away the top layers of the skin. The purpose of dermabrasive surgery is to reorganize or restructure the collagen of the papillary dermis without injuring the reticular dermis. Dermabrasion was first introduced by Kromayer in 1905, who observed that if superficial mechanical injury did not penetrate the reticular dermis, scarring would not occur. The technique originally involved the use of cylindrical knives for treating scars and other cosmetic defects¹¹. Later methods involved the use of rasps, burrs, and punches. Kromayer also described the use of carbon dioxide snow and ether to produce anaesthesia and rigidity prior to dermabrading. Dermabrasion can be performed with sandpaper, wire brush, scalpel, or laser. The thickness of skin layers varies greatly from one area to another, and although all areas may be dermabraded without scarring, it is the face that is ideally suited to dermabrasion. Scars which are raised above the skin are particularly susceptible to dermabrasion. Concerns regarding the incidence of postoperative infection have made it less popular in recent years. Although this procedure has been performed for a long time, and is almost always done using a small, sterilized electric sander, now laser techniques have become popular as they can be applied with much greater precision. The development of carbon dioxide laser dermabrasion has allowed greater control of the procedure and has the advantages of facilitating a bloodless field and being much less painful than surgical dermabrasion.

The anaesthetic technique for dermabrasion is similar to that for a facelift. The procedure is usually short and endotracheal intubation is not required. The use of LMA and intravenous induction and spontaneous ventilation with modern inhalational agents is routine. The procedure can be uncomfortable in the immediate postoperative period and the skin may remain indurated for several weeks.

Prominent ears are usually an isolated finding. Prominence is examined in thirds to determine where the prominence lies. The surgery is tailored to correct the specific excesses. The antihelical fold is flattened and may require reshaping. The surgery usually involves an elliptical skin incision behind the ear, dissection, cartilage scoring or resection, and mattress suturing. A porous polyethylene implant may be used if cartilage is deficient.

The majority of patients are children and the anaesthetic considerations are as for any other paediatric anaesthetic (see Chapter 19). Surgery can be performed under simple laryngeal mask anaesthesia. Adult patients will accept LA for pinnaplasty. LA can be achieved by infiltrating each ear with 10 ml of 1% lidocaine with 1:200 000 epinephrine. GA technique in adult is similar to that required of a facelift or blepharoplasty (see earlier sections). As the dermatomes supplying the back of the ears correspond to the vomiting centre in the brain, the incidence of postoperative nausea and vomiting (PONV) is much higher in these patients and prophylactic antiemetic should be considered. This must be explained to the patient in the preoperative consultation. Postoperative pain usually requires non-steroidal and simple analgesics. Dressing should be firm without being excessively tight. Scalp discomfort and itching can cause discomfort.

Laser is increasingly used for aesthetic and non-aesthetic procedures in both paediatric and adult practice. There are numerous textbooks devoted to lasers and their development and readers should consult an authentic textbook for further details. A recent land mark article by Takac et al.¹¹ contains a very good description of lasers and their applications in clinical medicine.

Laser is electromagnetic radiation falling between infrared and ultraviolet on the spectrum mainly in the visible light spectrum. Properties of laser light are monochromacity (the same colour), coherence (all of the light waves are in phase both spatially and temporally), and collimation (all rays are parallel to each other and do not diverge significantly even over long distances). Lasers were first conceived by Einstein in 1917 when he wrote ‘Zur Quantum Theorie der Strahlung’ (the quantum theory of radiation) which led to the concepts of stimulated and spontaneous emission and absorption¹². Later in 1958, Arthur Schawlow and Charles Townes extended lasers into the optical frequency range¹³. In simple terms, a laser is a device that emits light or electromagnetic radiation through a process called stimulated emission and its acronym is Light Amplification by Stimulated Emision of Radiation. To understand the above concept, it is necessary to understand the basic physics of the atom. If an excited atom is struck by another photon of energy before it returns to the ground state, two photons of equal frequency and energy, travelling in the same direction and in perfect spatial and temporal harmony, are produced. This phenomenon is termed stimulated emission of radiation. An external power source (or ‘pumping system’ which may be optical, mechanical or chemical) hyperexcites the atoms in the laser medium so that the number of atoms possessing upper energy levels exceeds the number of atoms in a power energy level, a condition termed a population inversion. These atoms then spontaneously emit photons of light. The laser chamber or optical cavity contains an active lasing medium which usually determines the name of each laser. There are four types of lasing material commonly employed: 1) solid state lasers use a solid matrix material such as a ruby crystal; 2) gas lasers use a gas or mixture of gases such as helium, argon, and carbon dioxide; 3) dye lasers employ a complex organic dye in liquid solution or suspension such as rhodamine; 4) semiconductor lasers use two layers of semiconductor substances such as gallium arsenide. The energy from the electromagnetic spectrum can be described in terms of wavelength, frequency, and energy.

Wavelength is the distance from peak to peak, or trough to trough, of a wave and is measured in the unit of microns (millionths of a metre) or nanometers (nm, thousandths of a micron). The wavelength determines the colour of the beam, the amount of energy the photons will carry, and hence determines how a beam will interact with the tissues of the body. The wavelengths of commonly used clinical lasers range from far infrared, near infrared, visible beams, through to ultraviolet beams (Table 10.1).

Frequency is inversely related to wavelength in the following way:

Frequency (f)=speed of light (3×108 ms)/wavelength

The frequency of visible light is very high and is expressed in tera Hz (tera = 10¹²).

This also explains the concept of ‘frequency doubling’, for example, neodymium:yttrium aluminium garnet (Nd:YAG) laser normally emits at 1064 nm or can be frequency doubled to emit at 532 nm using a crystal such as potassium titanyl phosphate (or ‘KTP’) crystal. For this reason it is also referred to as ‘KTP laser’.

Pulse repetition is the number of pulses emitted in one second quoted in hertz (Hz). All matter in the universe is made up of atoms which consist of negatively charged ‘electrons’ orbiting around a positively charged nucleus. Exciting atoms to emit photons can produce light. To produce laser light, atoms of some material such as a gas, a liquid dye, or a crystal rod must be excited. If an electron absorbs energy it can go on to a higher level and be in an ‘excited state’. Energy can be delivered into an atom by an electrical power supply or flash of light. By doing so the atom becomes unstable, hence the electron returns to a lower level spontaneously by emitting a photon. The photon released in this way can stimulate another electron to release its photon and so on. These photons have identical energy and frequency and travel in ‘phase’ or coherence.

A laser consists of a gain medium inside a highly reflective optical cavity, an energy supply to the gain medium to stimulate continuous emission releases the light as a laser beam. Principal components of a laser include gain medium, laser pumping energy, high reflector, output coupler, and laser beam

The gain medium is a material of controlled purity, size, concentration, and shape with properties that allow it to amplify light of a specific wavelength by stimulated emission. It can be in any state, either a gas, liquid, or solid. Argon, helium, carbon dioxide, and krypton are in gaseous form, Ng:YAG, ruby and alexandrite are solids, and rhodamine a liquid.

The process by which supplied energy amplifies the light is called ‘pumping’. The energy source is typically an electrical current or light at a different wavelength provided by a flash lamp.

In its simplest form, the laser optical cavity consists of two mirrors arranged such that light bounces back and forth, each time passing through the gain medium.

One of the two mirrors in the cavity, called the ‘output coupler’ is partially transparent and allows some of the light to pass through and escape as a beam of light.

The laser beam generated is a beam of coherent electromagnetic radiation which is of uniform wavelength, parallel, non-divergent, and undirectional in the same phase. Different gain medium produce different types of laser beam. The output of a laser varies with respect to time. Beams can be emitted as continuous constant-amplitude output, known as continuous wave (CW), or as a single pulse or series of pulses.

The length of time the laser beam is activated is known as the pulse duration and is measured in seconds. It determines how tissues will react to light of specific wavelength. Many systems deliver pulses with a fixed or variable pulse delay between the pulses to maximize effectiveness, at the same time minimizing damage to adjacent tissues.

Many medical laser systems can be Q-switched whereby the population inversion is allowed to build up by making the optical cavity conditions (the ‘Q’) unfavourable for generating a laser beam. Then, at the desired level of pump energy stored in the laser medium, the ‘Q’ is adjusted, electro- or acousto-optically to more favourable conditions, releasing the pulse. This results in high peak powers as the average power of the laser is packed into a few nanoseconds. For achieving an even greater density of power, modelocking can be deployed. In modelocking extremely short pulses of laser are emitted in the order of tens of picoseconds down to less than 10 femtoseconds such as in a titanium sapphire laser. This achieves extremely high power density suitable for ablation applications.

The types of lasers used in clinical practice use a variety of laser media and energy pumps. Some clinical lasers use a gaseous medium such as carbon dioxide, argon, krypton, or helium-neon and are pumped by electric discharge through the gas. Gas layers may produce a continuous or an intermittently pulsed output. Other lasers use solid rods of laser-passive material containing small quantities of ionic impurities, known as dopants, which are the actual laser materials. Dopants commonly used for their laser potential include chromium (ruby laser), neodymium (Nd), and holmium (Ho). A synthetic crystal YAG is commonly used as a passive host matrix. Lasers are also made from dyes in liquid media and semiconductors. A list of different lasers used for surgical procedures is included in Table 10.2.

In the United Kingdom, the Medicines and Healthcare products Regulatory Agency (MHRA) is the executive body responsible for protecting and promoting public health and patient safety. The MHRA have published guidance on the safe use of lasers in the medical environment¹⁴. Most lasers used in medical practice are in Class 4, so a formal educational and safety programme must be completed before using such devices in the clinical setting. Illuminated signs indicating lasers are in use must be obvious outside the entrance to the clinical area. All staff must be trained in the use of lasers and be totally familiar with the dangers to both patient and personnel. Staff should wear masks to protect from inhalation of vaporized laser smoke and appropriate goggles to protect their eyes (see next section). Means of actively scavenging laser smoke should be deployed.

Lasers are potentially dangerous technologic devices; hence their clinical use is subject to regulation. Light can interact with body tissues as it gets transmitted, scattered, or absorbed by the tissues. The effect of a particular laser on body tissues depends on the nature of the tissue being irradiated, the power density of the beam, and the wavelength. Selective photothermolysis refers to the concept of targeting a chromophore in a specific manner utilizing the light energy to cause a temperature medicated localized injury in a manner that avoids damage to adjacent non-targeted tissues^{15  ,16}.

The eye is particularly susceptible to damage from laser beams either directly or through reflection. The optical gain of the eye can result in an extremely concentrated area of radiant energy falling on the cornea or retina. This can result in permanent damage in a matter of seconds. Carbon dioxide can cause serious corneal injury whereas argon, KTP, and Nd:YAG lasers may burn the retina.

The eyes of both patient and theatre personnel should always be protected by approved laser safety glasses appropriate to the laser modality in use (laser specific or wavelength specific). Regular eyeglasses may be sufficient but contact lenses are not. Protective eyewear must be undamaged and have permanent labels with wavelength and optical density tolerance, side shields, damage threshold of greater than 10 seconds, no surface reflection, good fit, and approval from the laser safety officer of the hospital. If protective eye glass interferes with the operative field then moistened sterile eye pads and towels should protect the patient’s eyes. Scleral shields are also available in case where surgery is performed near or on the eyelids. All operating room windows must be covered with an opaque material that will absorb the appropriate wavelength of the lasers in use and specially designed warning signs should be posted.

Misdirected laser energy may damage an organ or large blood vessel. Vessels larger than 5 mm are not coagulable by laser. With an Nd:YAG system it is impossible to assess immediately or accurately because organ damage or bleeding may not occur until oedema and necrosis have become maximal several days later.

Many items used in the operating theatre, such as drapes, gowns, sponges, plastic cannula, endotracheal tube, LMA, infusion giving set, are made of materials that can be a fire hazard if not kept from interaction with high intensity laser beam heat. Protection from fire can be prevented by using fire retardant (or moist drape), availability of water basin, availability of a fire extinguisher, use of non-alcohol containing prep solutions, avoiding plastic and rubber instruments, fire-resistant endotracheal tube or LMA, and keeping the inspired oxygen concentration to a minimum. If the endotracheal tube or LMA is not fire retardant, it should be covered with aluminium foil or saline wet swabs. The endotracheal tube provides the least leakage of oxygen to the area and is the best option of securing an airway. It is important to avoid the use of metal and reflective materials.

The destruction of cells by laser releases smoke, carbon particles, and fine particulates smaller than 0.31 microns which can be transported and deposited in the alveoli. Many staffs do not like smells. Carbon dioxide lasers seem to produce more smoke because of vaporization of tissues. An ordinary surgical face mask is not sufficient in preventing particulate inhalation and the use of a powerful smoke evacuator at the surgical site is recommended.

When a laser is used clinically the skin absorbs some light from the laser spectrum which is then converted to heat, producing side effects or damage to adjacent tissue. To prevent this, the heat must be dissipated rapidly from the tissues. This can be achieved by pretreatment cooling using ice packs or with damp gauze. The alternative, a Dynamic Cooling Device (Candela), can be used which allows a burst of cryogenic spray to be fired for a fraction of a second before the laser is delivered. Simultaneous cooling with water-cooled tips or moving air systems have also been used with success. Post-treatment cooling can be achieved with damp gauze, ice packs, moving air gel, and creams. This has the added benefit of reducing redness and is soothing for the patients.

Carbon dioxide laser is commonly used for resurfacing surgery and this is preferred to surgical facelift to avoid scarring and for quicker recovery. Laser resurfacing reduces fine lines, wrinkles, and skin discolouration. It is also used for facial scarring due to acne or injury. The skin healing is quicker and the connective tissue becomes stronger, hence tightening the facial skin. The duration of surgery may take hours as the skin layers are lasered several times.

A general medical history should be obtained prior to treatment, including information on wound healing, any bleeding diathesis, history of infectious diseases, particularly hepatitis and human immunodeficiency virus (HIV) infection. The presence of HIV proviral DNA has been demonstrated in the laser plume generated by carbon dioxide laser irradiation of HIV-infected tissue culture¹⁷.

Most patients experience only a transient stinging sensation during laser or intense pulsed light source treatment that is well tolerated, thus limiting the need for anaesthesia. However, cumulative pulses may produce increasing and intolerable discomfort. Anaesthesia is often required in young children or individuals with large lesions. In many instances, use of topical anaesthetics such as eutectic mixtures of LA (EMLA) or Ametop cream alone is sufficient. Application of a thick layer of LA cream under an occlusive dressing for 60 minutes followed by removal 10–30 minutes before treatment is necessary for maximal effectiveness. If needed, local infiltration or regional nerve block may be performed with lidocaine. Epinephrine should generally be avoided during local infiltration of haemangiomatous lesions because it may constrict the targeted vessels. Premedication with hypnotics, sedatives, or analgesics may be required in anxious patients.

Where GA is unavoidable for aesthetic laser procedures, then minimally explosive mixtures of inspired gases, such as air with less than 30% supplementary oxygen, should be used. Only dedicated laser protective airway devices should be used and protected from accidental direct contact with the laser beam by means of saline soaked dressings. Endotracheal cuffs should be filled with saline rather than air. Intravenous induction and controlled ventilation with an endotracheal tube and inhalational agent or TIVA is a standard anaesthetic technique in routine use.

Postoperative pain or discomfort is essentially like a severe burn. Intraoperative analgesia and its continuation in the postoperative period is important for keeping the patient pain-free. Occlusive ointment and analgesic provide pain relief. PONV may occur and should be prevented and treated as soon as possible. Patients may shiver and this is usually associated with long duration of surgery.

Laser treatment is popular and is used for a wide variety of other maxillofacial aesthetic procedures. The choice of laser modality is in part influenced by the lesions to be treated (see Table 10.2).

Every person has a few obvious brown spots on their skin. Freckles, ‘age spots’, ‘liver spots’, and various birthmarks are just a few of the commonly known marks, generally referred to as pigmented lesions. Melanin is what gives our skin its colour. We all have varying amounts of melanin. Pigmented lesions are dark in colour simply because melanin is abnormally concentrated in one area of the skin. High concentrations of melanin can be due to various factors. Pigmented lesions can be successfully lightened or removed with modern laser technology. A laser is designed to produce one or more specific light wavelengths which are preferentially absorbed by the pigment. Pigmented lesions are either lightened or removed when the laser light passes through the skin but is absorbed by abnormal concentrations of melanin. The rapid absorption of light energy causes the destruction of the melanin. This reduction in local concentration leaves the treated skin looking uniform in colour and texture.

Tattoo ink is removed by using a specific wavelength which passes through the skin but is absorbed by the ink. The rapid absorption of light energy causes the tattoo ink to destruct and it is then removed by the body’s natural filtering systems.

Port-wine stain birthmarks respond remarkably well to laser treatment. The abnormal blood vessels that cause these marks are reduced in size by the laser. This results in a lightening of the treated area. Skin growths, facial ‘spider veins’, and warts respond to laser surgery. Most situations take more than one laser treatment, but some respond to a single treatment.

The pulsed dye laser delivers an intense but gentle burst of yellow light to the skin. The light is specifically absorbed by the blood vessels in the dermis. These blood vessels are coagulated and then reabsorbed by the body during the natural healing process.

Botox injections are usually performed for frown lines, smile lines, forehead lines, brow lift, laugh lines, jaw muscles, neck horizontal lines, excessive sweating and body odour, facial contouring. This procedure is usually performed in an office setting or the high street. Botox is derived from a purified protein and can be used in adults below 65 years of age for medical and aesthetic indications. Botox temporarily blocks the release of acetylcholine, preventing the muscles from contracting and enabling them to relax¹⁸. During treatment, very small doses of botox are administered via a few tiny injections into the muscles responsible for frown lines between the brows. The procedure takes approximately 10 minutes and there is minimal downtime afterward. Discomfort is minimal and brief. Botox injections are performed with or without injection of LA agents and the help of an anaesthetist is not required.

Pulse Repetition Frequency (PRF) is designed to rejuvenate the skin by removing pigment and stimulating collagen and elastin production. PRF is helpful for fine facial wrinkles, large pores, and post-acne scarring, pigmentation, prominent blood vessels, and unwanted hair.

Aesthetic surgery provides many challenges for the anaesthetist. The procedures can range from a minor to major surgery requiring prolonged anaesthesia. Success or failure of aesthetic surgery not only depends on surgical skill but also on careful selection of the anaesthesia technique.