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Fig. 11. Trachea intubation is completed, the tube is fixed round the head

In operations on the oral cavity a nasotracheal intubation is carried out. In order to reduce the risk of turbinated bone injury, a well-oiled tube of lesser diameter (No.6-6.5 in females, No. 6.5-7 in males) is passed, primarily, through the right nostril, as far as in this case the tube section will be faced the nasal septum. The tube is passed through the pharynx under the control of laryngoscope and directed into the true glottis blindly or with the help of Megill's forceps (curved packer).

A luminous stilette-light guide can be used as the guide for naso- and orotracheal intubation. It is introduced blindly with the intubation tube, fitted in, following the flexure of the tongue in the operating room with dim light. A luminescence of the anterior surface of the neck gives evidence of the location of the light guide tip in the trachea (if it gets into the esophagus, the intensity of luminescence is significantly lower). The tube is pushed somewhat ahead and a light guide is removed.

Tracheal intubation can be carried out by means of fibro-optic laryngoscope. A field of vision is impeded by mucus, blood and sweating of the fibroscope lenses, that can be prevented by preliminary immersion of the fibroscope tip into warm water.

If all the above-described procedures proved to be helpless, a retrograde tracheal intubation may be applied. It is performed in the patient on the background of ventilation through the airway. Along the median line a crico­thyroid membrane is punctured and intravenous catheter, with the diameter 1.25 mm, is introduced through which a guide-mandren, with the diameter of 0.6 mm and the length of 80 cm, is passed in the cranial direction.

Under the control of laryngoscope the tip of the guide is brought out through the mouth and the endotracheal tube is passed along it into the trachea via the vocal cords.

In increased risk of regurgitation and aspiration (full stomach, pregnancy, ileus, obesity, esophageal reflux) a rapid, successive induction in anesthesia is carried out.

After a thorough preparation of equipment and working place (suction machine, laryngoscope, tubes, APV apparatus) a preoxygenation with 100% 0₂ is carried out in the presence of the assistant for 3-5 min or the patient is asked to make 4 maximal inhalations of 100% 0₂. The neck is straightened, anesthetic (thiopental, propofol, ketamine) and dithylinum are administered, at the same time the assistant presses, rather strongly, on the cricoid cartilage squeezing the esophagus (Selick's technique).

Laryngoscopy and tracheal intubation are made fast (for 30-60 sec). In case of failure, the pressure, exerted on the cartilage, is being continued for the length of all subsequent attempts and ventilation with a mask using 100% 0₂.

Already during a preoperative examination a number of signs may be revealed pointing to possible difficulties in intubation:

— impossibility to open the mouth;

— restricted mobility of the cervical part of the spinal column;

— micrognathia;

— protruded upper incisors;

— short neck;

— obesity;

— macroglossia.

If the attempt to intubate the trachea fails one should carry out APV with a mask prior to repeated attempts or applying another method of intubation (for example, with the aid of fibrooptics). In planned operation, we may postpone the operation until certain conditions are prepared to apply another method. If it is impossible to postpone the operation (for example, cesarean section, internal hemorrhage and so on), APV with a mask should be continued on the background of Sellick's technique.

If a ventilation with a mask is impossible, a laryngomask may be placed, and in its absence or difficulties with its installation, it is necessary to perform

urgently a cricofhyreotomy.

Since the moment, when anesthesiologist becomes convinced of the sufficient depth of narcosis and the absence of serious disorders of vital activity that could occur during the induction stage, the operation begins. From this moment one of the most important tasks, facing the anesthesiologist, is the maintenance of anesthesia, namely, to provide for good anesthesia, analgesia, myorelaxation and the operation of vitally important functions, i. e. a creation of optimal conditions for the operation and ensuring patient's safety. These tasks can be performed by different methods.

For the first 100 years the inhalation anesthetics, practically, dominated completely, but for the subsequent 50 years they gave place to noninhalation ones, and, at present, both classes of anesthetics remain in the arsenal of anesthesiologists and the choice of method depends on the peculiarities of patients condition and surgical intervention.

In ambulatory, not very traumatic, short-term operations, painful diagnostic and therapeutic manipulations in the patients with physical state ASA 1,2 (classification of American Society of Anesthesiologists) the use of noninhalation agents is more indicated because they provide a rapid and comfortable induction, simplicity of administration and selectivity of action. In other situations (prolonged traumatic operations in grave patients) it is expedient to use a combination of noninhalation agents with inhalation ones that guarantees more reliably from a sudden patients awakening in the course

of operation.

While applying different anesthetics one may conduct anesthesia with the maintenance of spontaneous respiration or with APV that depends on the severity of the patient's condition, duration (APV — for more than 2 hours) and volume of operation, as well as on some specific tasks (for example, a need to maintain control of spontaneous breathing in some neurosurgical interventions). When APV is carried out, they may use a face or laryngeal mask, but endotracheal intubation is more reliable. APV parameters are calculated for the adult as follows: RV = 9 ml x m; RR = 8-10 per min., peak inspiratory pressure 30 cm water column; PMV = rs + 1 1., where m — a body

mass in kg.

No less important task facing anesthesiologist in the period of maintenance of anesthesia is to monitor the depth of narcosis and the state of vital functions. In order to determine the depth of narcosis, clinical signs of its stages according to Gwedell, taking into account certain features of pharmacodynamics of the applied agents, are used. At present, some works are under way to create computer programs for monitoring and dosing a depth of anesthesia, so-called TCA (Target Controlled Anestheia). Anesthesia with propofol infusion by a target concentration (A.A. Bunyatyan, 2000) may serve as an example. Having established the target concentration at the moment of loss of consciousness, it is maintained in the course of operation with the aid of constant load controlled by computer system by the parameter of spectral analysis of EEG and blood circulation.

As far as a monitoring of vital functions is concerned, the adequacy of pulmonary ventilation is estimated by the patient's appearance, lungs pulsoximetry, and in case of need a periodical determination of blood gases. Blood circulation is monitored by regular determination of AP and HR, CVP, as well as by a cardiomonitor.

While anesthesia is being conducted, the intraoperative needs in liquid are covered that consist, first and foremost, of the basic demand ensuring of which starts still in the period of patient's preparation for the operation and continues during and after the operation, losses in the so-called "third space" (accumulation of liquid in the injured tissues, in the lumen of the intestine and in natural cavities of the organism), losses with perspiration from the operative wound (about 20 ml/kg/hour), blood loss the volume of which may be judged, approximately, by the level in the capacity of suction unit, blood in the gauze serviettes and operative linen (they may be even weighed), on the floor and so on. In case of significant blood loss a plan of infusion therapy can be approximately drawn up on the basis of Algover's shock index (p. 207) in accordance with hematocrit indices and other indirect signs of the blood loss volume.

A recovery from anesthesia is as the important moment as the induction. into it. Anesthesiologist's task lies in the fact that the patient's consciousness will come back to him at the level of fulfilment of verbal commands and contact, as well as the restoration of muscular tension ensuring an adequate respiration and defense pharyngeal and cough reflexes, maintenance of stable hemodynamics. In order to achieve this, the depth of anesthesia must be such at the end of operation, as to be able to waken the patient quickly. After extubation an auxiliary ventilation with mask and a breathing with pure oxygen may be required. Taking into consideration a possibility of excitation stage before awakening, one should be extremely cautious in this period with suction of mucus from the trachea and oral cavity, so as not to cause laryngo-spasm, to avoid moving the patient from one place to another.

In respiratory failure, hypothermia, delayed recovery from anesthesia, unstable hemodynamics, presence of danger of aspiration and disturbance of the patency of respiratory tracts the patient is left intubated until these states are eliminated.

Extubation may be carried out on the patient staying awake or under narcosis.

In the first case, a regained consciousness, stable hemodynamics and

muscular tension sufficient in order to lift the head and to breathe independently with satisfactory indices of ventilation and oxygenation are necessary. Extubation in the excitation stage may cause a laryngospasm. An eye should be kept on the extubated patient as far as he may fall asleep again in the absence of painful stimulations that may lead to a mandibular

retraction.

Extubation, at the III stage of narcosis, reduces the risk of laryngo- and broncho-spasm that is expedient, for example, in the patients with bronchial asthma, and allows to avoid strain while coughing that is also reasonable after the operation for aneurysm of cerebral vessels, on the middle ear, chambers of the eye, for inguinal hernia, etc. Having waited for the restoration of respiration on the background of deep narcosis, after sanitation of stomatopharynx, a cuff is discharged, the tube is removed and inhalation anesthesia is being continued, gradually decreasing the concentration of inhaled anesthetic up to an awakening. In order to exclude an excitation while consciousness is being restored, one should eliminate hypoxia, hypercapnia, obstruction of respiratory tracts, pain, overfilling of the urinary bladder.

In delayed recovery from anesthesia a prolonged APV is required with establishing and eliminating the cause.

In case of adequate respiration and stable hemodynamics, a patient, accompanied by the anesthesiologist, is moved from the operating room, under observation of the personnel on duty, to the surgical department (better to the ward of the postoperative observation), and in need of further intensive observation and intensive care to the intensive care department. Regardless of the place of further patient's staying the anesthesiologist must make notes in the case history about his postoperative examination in the first 24-48 hours, paying attention to medicinal measures carried out, patients impression of the operation and anesthesia, give necessary recommendations on

treatment.

In spite of the fact that the aim of anesthesia lies in the patient's protection from surgical aggression, anesthesia represents, per se, a temporary reversible effect upon CNS and other vital functions, and, therefore, it is not deprived of the danger of complications. Statistics of mild and even serious complications (for instance, persistent neurologic disorders) have been insufficiently studied. As for a death rate, to some extent or other, associated with anesthesia, according to USA data (W.F. Hurford et al., 2000) even in the planned surgeries on the relatively healthy patients makes up from 1/50000 to 1/150000. Therefore, anesthesiologist must be ready for a fast elimination of undesirable effects of anesthesia not allowing their transition into serious complications. The following factors may lead to complications of anesthesia: — insufficient preparation of the patient because of incomplete study of his condition and underestimation of certain findings;

— unpreparedness of the working place;

— insufficient knowledge of equipment and experience to work with it;

— shortcomings in the checking of equipment readiness for operation;

— impossibility of monitoring;

— unreadiness for urgent situations;

— poor knowledge of the course of the operative intervention;

— insufficient knowledge how to use the technique of carrying on anesthesia;

— poor knowledge of pharmacology of used agents;

— poor interaction with surgical team;

— lack of consideration and carelessness;

— insufficient scope of vision;

— fatigue;

— unreadiness to apply for help.

Complications are minimal in local anesthesia (sometimes, ineffective anesthetization, anaphylactic reaction to local anesthetic, respiratory and circulatory disorders, neurologic disorders in regional anesthesia, etc.). Complications in general anesthesia may occur at the various stages of anesthesiologic provision: premedication, initial narcosis, maintenance of anesthesia and in the postoperative period. But the most responsible, in this connection, are the periods of induction of narcosis, recovery and early postoperative period. Complications may be caused by the specific effects of anesthetic, techniques of conducting anesthesia, the main and associated diseases and the character of surgeries.

The most probable are the complications on the side of organs of respiration. They occur because of the obstruction in the respiratory tracts (accumulation of sputum, mandibular retraction, aspiration during vomiting and regurgitation, laryngospasm, bronchospasm, etc.), respiration control disorders (depression of the respiratory center, hyperventilation in APV, hyperoxia and others), neuromuscular conduction (effect of myorelaxants, disorder of electrolyte metabolism, etc.), pulmonary lesions (pneumonia, atelectasis, edema and others).

No less threatening cardiovascular complications may be caused by inadequate gas exchange, blood circulating volume (BCV) changes, effects of anesthetics and other medicaments that are used in the course of operation or just after it, disorders in blood coagulation and anticogulative systems. They are manifested by a disturbance in cardiac rhythm up to its standstill, arterial pressure changes, embolisms and thromboses. Tachycardia may appear in gas exchange disorders, blood loss, inadequate anesthesia, reflex stimulation of the heart, atropine effect. A pronounced tachycardia may be a precursor of myocardial fibrillation. Bradycardia may develop as a result of severe hypoxia, overdosage of fluothane and narcotic analgetics, severe vagotonia. Arterial hypertension may arise in hypercapnia, under the action of ketamine, in the inadequate depth of anesthetization.

Complications on the part of digestive organs such as vomiting in irritation of reflexogenic zones (the root of the tongue, pharynx) on the background of insufficient depth of narcosis in the course of induction and recovery, in hypoxia, hyperhydration in the postoperative period, may become the cause of aspiration of vomit masses, in this connection, it is recommended to lay the patient down without a pillow with a turn of the head to the right side and not to leave him without observation up to a complete restoration of consciousness

and reflexes.

During narcosis when muscles of pharynx and esophagus are relaxed and the pressure in the stomach is elevated a regurgitation of gastric contents may occur, as a result of this, as in vomiting, an aspiration can take place with asphyxia and Mendelson's syndrome. Regurgitation is, particularly, dangerous because before the moment of aspiration it proceeds asymptomatically.

The best means of vomiting and regurgitation prevention is gastric evacuation prior to the operation. In the time of induction it is recommended to ventilate the lungs extremely carefully before intubation, in order not to pump the air into the stomach, to apply Sellick's technique during laryngoscopy and tracheal intubation, application of endotracheal tubes with inflated cuffs. Complications on the part of nervous system may be expressed as CNS injuries owing to prolonged hypoxia, hypercapnia or overdosage of anesthetics (delayed recovery from anesthesia, convulsions, mental disorders), as well as a lesion of peripheral system in the form of neuritides, pareses, paralyses due to a compression or overextension of brachial plexus, fibular nerve, etc., in the wrong patient's laying in the period of operation and after it.

Complications, associated with the disturbance of thermoregulation during narcosis occur in newborns and one year-old infants in the form of sclerema induration of subcutaneous fat with the development of respiratory failure, spontaneous hypothermia because of the increased heat emission on the background of blockade of thermoregulation and in the form of malignant hyperthermia in young people and children in the postoperative period, the cause of which is a hereditary burden. Prevention of complications consists in a thorough anamnesis concerning the pathology of thermoregulation (particularly, when fluothane and myorelaxants are used), control and maintenance of normal body temperature.

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