ANAESTHETIC TECHNIQUES

The table below is intended to help you decide what type of anaesthetic might be most suitable for a given surgical procedure.



Suitable anaesthetic techniques for different types of surgery

Type of surgery Suitable anaesthetic technique
l Major head and neck General tracheal
l Upper abdominal
l Intrathoracic
l Ear, nose and throat
l Endoscopic
l Upper limbs General tracheal (LMA)
or Nerve block
or Intravenous regional
l Lower abdominal General tracheal
l Groin, perineum or Spinal
l Lower limbs General tracheal (LMA)
or Nerve or field block
or Combined general and conduction

For minor emergency operations when the patient probably has a full stomach, such as the suture of a wound or manipulation of an arm fracture, conduction (regional) anaesthesia is probably the wisest choice.

For major emergency operations, there is often little difference in safety between conduction and general anaesthesia.

It is a dangerous mistake to think that conduction anaesthesia is always safe.

When you have come to a decision on the most suitable technique, discuss it with the surgeon and surgical team, who may give you further relevant information. For example, the proposed operation may need more time than can be provided by the technique you have suggested or the patient may need to be placed in an abnormal position. Also check that you have all the drugs and equipment you may need.

You will probably have to decide on one of the following techniques:

There are advantages in combining light general anaesthesia with a conduction block: this technique reduces the amount of general anaesthetic that the patient requires and allows a rapid recovery, with postoperative analgesia being provided by the remaining conduction block.

PLANNING GENERAL ANAESTHESIA

For general anaesthesia, tracheal intubation should be routine, unless there is a specific reason to avoid it (see Figure 13.12 on page 13–29).

Tracheal intubation is the most basic of anaesthetic skills and you should be able to do it confidently whenever necessary. In smaller hospitals, most of the operations are emergencies; the lungs and lives of the patients are in danger if you do not protect them by this manoeuvre.

Remember that all relaxants are contraindicated prior to tracheal intubation if the patient has an abnormality of the jaw or neck or if there is any other reason to think that laryngoscopy and intubation might be difficult (see also Paediatric emergency anaesthesia, pages 14–18 to 14–20).

Safety of general and conduction techniques

There are potential risks with all types of anaesthetic. These can be minimized by careful assessment of the patient, thoughtful planning of the anaesthetic technique and skilful performance by the anaesthetist. You should keep records of all the anaesthetics that you give and regularly review complications and morbidity. Some of the possible complications to look for are listed below.




CHOICE OF TECHNIQUE IN EMERGENCY ANAESTHESIA

General or regional anaesthesia?

General and regional techniques both have a place in dealing with emergencies. The factors that favour the use of general anaesthesia are:

There are exceptions. For emergency caesarean section, spinal anaesthesia may be better, provided the mother is not shocked, septic or dehydrated. A strangulated inguinal hernia or torsion of the testis occurring in a patient in good general condition can also be performed under spinal anaesthesia.

On the other hand, cord prolapse during labour, shock or severe bleeding indicates general anaesthesia.

In some cases, either general or regional (spinal) anaesthesia may be appropriate:

A gunshot wound to the leg, when there is uncertainty about what will be found, would be better explored under general anaesthesia. A few days later, the same patient returning in a stable condition for wound toilet, could have a spinal anaesthetic.

Full stomach and regurgitation risk

As a general rule, all patients must come to the operating room starved (no solids for 6 hours, water allowed up to 2 hours preoperatively). You should assume that the stomach is not empty in injured or severely ill patients, in those that have received an opiate such as pethidine and in pregnant women.

Any method of anaesthesia, including awake techniques, can have an unexpected reaction that can, in theory, lead to unconsciousness, regurgitation and aspiration of stomach contents. You will need to judge each case on its merits, balancing the risk of regurgitation and aspiration against the risks of general or spinal anaesthesia. The general condition of the patient determines the risk of regurgitation more than the choice of technique. If an operation is postponed on the grounds that the patient is not starved, there may be a risk of it not being carried out at all.

Poor risk cases

A typical case where we are unsure of what method to use might be a patient in poor condition whose chronic illness has been neglected. Surgery may give improvement by cleaning, debridement of necrotic tissue or drainage of pus in the hope that healing will take place, suffering will be relieved and the patient will move a step nearer to leaving hospital. Large numbers of such patients are seen every day in hospital operating rooms in any country with a high rate of HIV seroprevalence.

Obstetric sepsis has a high incidence and is the biggest cause of hospital maternal mortality in some countries. Patients frequently develop sepsis up to ten days following septic abortion, ectopic pregnancy and normal or operative delivery. Sometimes, in advanced sepsis, there are disagreements among medical staff about whether to take the case at all.

“Gasping” means a type of respiration with feeble, jerky inspiratory efforts that cause movement of the head in a semiconscious patient. Prognosis is very poor. Predicting the outcome with or without an operation is one of the more difficult judgements in medical practice.

Ketamine is the drug of choice, 1–2 mg/kg IV, according to the condition. Oxygen is mandatory after ketamine because hypoxia usually occurs.

Intubation is recommended for laparotomy. A small abdominal incision and drainage may become a full laparotomy and washout in the intensive care unit. Management with inotropic support is usually needed postoperatively.

A critical moment in the operation is during the initial abdominal exploration and breaking down of adhesions. Endotoxaemia is maximal at this time and sudden death in asystole may occur. Epinephrine should be drawn up ready.

Ketamine is safest for patients who are to have uterine evacuation, where there has been haemorrhage or sepsis.

SPECIAL ANAESTHETIC ISSUES

The solo practitioner giving anaesthesia

Many hospitals in developing countries will have only one person assigned or trained to give anaesthesia. Even so, you should identify and train another person to help you and even take over your duties from time to time. It is quite possible for a single-handed paramedical health worker to have sole responsibility for a major emergency case in a remote location in a developing country that would, elsewhere, have a team of senior experts managing the different requirements of airway, drip, drug administration, ventilation, etc. It is also possible for you (if you are a solo, non-specialist practitioner) to do just as good a job as the experts.

However, there are certain things that require the help of a second person:

It is important for you to identify an assistant (not a replacement anaesthetist) who knows the hazards of anaesthesia, how you work and where things are kept. Above all, he or she needs to understand the meaning of acting quickly when things go wrong.

Never start a case if you are alone with the patient in the operating room.

The full stomach: cricoid pressure

A full stomach is one of the most dangerous situations in the practice of anaesthesia: if a patient aspirates stomach contents into the lungs, the resulting complications mean that the chance of survival will be slight. Aspiration of stomach contents may be one of the most common causes of death on the operating table in developing countries.

Cricoid pressure (pressing on the cricoid cartilage with a pressure of 30 Newtons: 3 kg) is intended to prevent passive regurgitation, but will not stop active vomiting. Active vomiting probably means the patient is awake and has intact protective reflexes; cricoid pressure is therefore not appropriate.

There are two situations where cricoid pressure should normally be applied:

There are additional dangerous situations where regurgitation is very likely:

Although it has never been subjected to controlled trials to prove its efficacy, properly applied cricoid pressure is believed to be an effective measure to prevent regurgitation.

If in doubt about the regurgitation risk, apply cricoid pressure – it costs nothing and may save a life.

Spontaneous versus controlled ventilation (IPPV)
Except for neurosurgery, there is no evidence that any operation has a better outcome when controlled ventilation is used instead of allowing the patient to breathe spontaneously. Thoracic procedures involving the open chest cannot, of course, be performed without controlled ventilation as the normal mechanics of breathing requiring negative pressure in the pleural cavity are disrupted.

The shocked patient may suffer a significant reduction in cardiac output if Intermittent Positive Pressure Ventilation (IPPV) is applied, owing to the increased thoracic gas pressure preventing venous return to the heart. Overzealous IPPV, either by hand or ventilator, may be a terminal event in a patient with hypovolaemia.

The use of spontaneous breathing has an additional safety effect of allowing you to monitor cerebral perfusion: breathing will stop if the brain is not being perfused with blood at an adequate pressure. Also, overdose of volatile agent in a spontaneously breathing patient is unlikely.

Where facilities for anaesthesia are limited, ventilators often do not have alarms to warn about disconnection and trained, experienced anaesthetists are not available. Emergency surgery under general anaesthesia in these conditions is safer when performed with the patient breathing spontaneously.

Ventilation in chest and head injuries

The patient with combined chest and other trauma may require intubation as part of general anaesthesia for a laparotomy (such as in cases of a ruptured spleen) or craniotomy (in cases of extradural haematoma). Intermittent Positive Pressure Ventilation (IPPV) is not necessarily part of the early management of chest trauma unless there are specific indications, for example, during cardiopulmonary resuscitation or if hypoxia, respiratory failure or other deterioration occurs.
Rib fractures may cause the lungs to be punctured on sharp ends inside the chest and result in pneumothorax. With further gas being forced into the lungs during ventilation, the pneumothorax may become a tension pneumothorax. A chest drain should be in place.

Lung contusion (consolidation from damage and bleeding) often gets worse in succeeding days so a patient who is comfortably breathing and sitting up with an oxygen mask on the first day post-trauma may later deteriorate and have to be ventilated.

Patients with head injuries can benefit from IPPV in the early stages of admission; it will help to avoid the lethal combination of hypoxia, airway obstruction and hypercarbia, a significant cause of mortality in the immediate period after injury.
However, controlled ventilation itself has not been shown to improve outcome for the head injured patient. There is no point in ventilating a brain dead patient with no prospect of recovery.

Tracheal tube versus laryngeal mask airway
The laryngeal mask airway (LMA) is now commonplace in most countries. It has proved very popular and is far less stimulating to the patient than the tracheal tube. It should not be used to replace intubation for:

Insertion can be under deep halothane anaesthesia or, in a paralysed patient or after intravenous induction, with propofol. Do not try LMA insertion after thiopentone as the patient will gag.

Method of insertion

The LMA has been used with success to maintain the airway after failed intubation. This important role of the LMA as an emergency tool in airway management makes it an essential piece of equipment in the operating room in any country in the world.

Mixing drugs

In emergency induction of anaesthesia, it may be convenient to use drugs mixed together in the same syringe for speed and simplicity of administration and increased patient safety. Ketamine and suxamethonium mix well without interaction and give a convenient, reliable one-shot sleep and relaxation effect, of rapid onset, so that you can concentrate on the airway. This is especially valuable if your syringes and needles are of poor quality, are made of glass or have been resterilized. However, many drugs do not mix, notably thiopentone and suxamethonium. Diazepam does not mix well with other drugs.

Pre-oxygenation should be done with one hand holding the mask and the other giving the drugs. If two hands are needed for the drugs, the mask can be held by the patient or an assistant.

Suction

Good suction is of paramount importance in anaesthesia and resuscitation and for all forms of surgery and intensive care. As a resuscitation tool, suction comes second only to a self-inflating bag and mask.

When you need suction, it must be instantly available, right by your hand at all times:

The power of suction is important. Never believe that a sucker is working until you have raised the tip to your ear and heard its power. Then tuck it under the pillow or mattress ready for use. Make sure the suction tubing will not kink when angled and that the suction motor is protected by a reservoir bottle and a filter.

A foot-operated sucker can be a life saving piece of equipment at a health centre without electricity.
Sucking stimulates the gag reflex and may induce vomiting. Excessive sucking damages the mucosa and causes bleeding. The general rules of suction are:

Use a rigid sucker for emergencies.

Suction in the trachea

A small-bore soft sucker is used for tracheal or bronchial suction. Special precautions are needed if sucking in the trachea: the sucker should be sterile, not the same one as used for the pharynx.

In children, the sucker should not be a tight fit in the small tracheal tube, otherwise the negative pressure may cause lung collapse.

Repeated tracheal suction in the intensive care unit may cause bradycardia and even cardiac arrest, so the ECG monitor must be watched.

Removal of foreign bodies

Removal of foreign bodies is a common job for anaesthetists in developing countries. In a district hospital, it is important that the anaesthetist is able to remove objects in the mouth, airway or pharynx, with or without anaesthesia, using Magill’s forceps. Children often hide small coins in their mouths which may slip down into the pharynx.

Have a recent X-ray, if available. After inhalation induction with halothane, a long straight blade laryngoscope is best to go behind the larynx. The child will be apnoeic during pharyngoscopy, so a pulse oximeter should be connected. An object further down in the oesophagus may be out of reach and may require intubation and oesophagoscopy.

An assortment of other items may have been inhaled or become lodged in the upper airway: seeds, fish bones, chicken bones, peanuts, bits of plastic, bottle tops and even leeches. For the airway, there are three general situations:

The first is obviously very rarely seen in a hospital. If you witness the event, there are two courses of action.

The object partly blocking the larynx is often a piece of bone or something flat, irregular and sharp that can be easily removed with Magill’s forceps after inhalation induction with halothane and oxygen. There is intense irritation for the patient and stridor may be caused by laryngospasm as well as by the object itself. Inhalation induction may be slow and, if assisted ventilation is easy, it may be permissible to give suxamethonium and IPPV. Though theoretically this may push the object further down, in practice that rarely happens. Do not declare the job complete until you are sure everything has been removed and breathing is comfortable and silent.

Unfortunately, the commonest situation is for a seed or peanut to be inhaled by a child past the cords and into a bronchus. Referral to a centre with a ventilating bronchoscope is mandatory and urgent.