INVESTIGATION OF DEATHS RELATED TO ANAESTHETIC PROCEDURES

 

INTRODUCTION

The deaths that occur inside the operation theatre often evoke considerable distress to the relatives of the patient and the subsequent misgivings on the team of doctors that performed the surgery. As a rule, surgery and most of the medical procedures are teamwork comprising of surgeons, anesthesiologists, other specialists and nursing staff. Further, anaesthetizing a patient and maintaining his vital parameters is still laden with too many imponderables.

However,it cannot be overlooked that the surgical team is in a better position to explain the events that occurred inside an operation theatre when the patient is unconscious or under anesthesia and the entry in to the operation theatre is barred to the relatives of the patient. In particular, it should be realized that the doctors and the theatre staff alone know what has happened to the patient inside the operation theatre when he is under anesthesia, which amounts to the superior knowledge of the medical team. The above rationale often puts the burden of explaining all the events that led to the death of the patient to the relatives of the patient and to the court of law when litigation arises on the anesthesiologists and the surgeons.

Anesthetic Risks and its ClassificationThe type of anesthesia, the nature of operation and the clinical condition of the patient determine the anesthetic risks. Lunn and Mushin estimated the mortality directly related to anesthesia to be 1 in 166 (0.6%). Following a ten year study from 1967-1976, Harrison found that anesthesia contributed in some degree to mortality in 2.2 per 10,000 anesthetics and that this represented 2.2 per cent of the total mortality from surgery, which was 10.15 per 1000.

When an elective surgery [non-emergency] is performed, the anesthetist engaged by the surgeon should be a qualified man, and he should always administer a generally accepted type of anesthesia. The patient should be examined preoperatively for anesthetic fitness to prove that the anesthetist used reasonable care and skill in preparing the patient for anesthesia before administering it.

The American Society of Anesthesiologists (ASA) has classified patients into a number of grades according to their clinical condition for assessing their physical fitness to undergo anesthesia. The ASA classification is as follows:

ASA I – A normally healthy individual.

ASA II – A patient with mild systemic disease.

ASA III – A patient with severe systemic disease that is not incapacitating.

ASA IV – A patient with incapacitating systemic disease that is a constant threat to life.

ASA V – A moribund patient who is not expected to survive 24 hours with or without operation.

If the operation is an emergency, the letter ‘E’ is placed beside the numerical classification and the patient is considered to be in poorer physical condition.

The following is the mortality rates after anaesthesia and surgery for each ASA physical status – emergency and elective cases:

ASA Rating	Mortality Rate [%]
I	0.1
II	0.2
III	1.8
IV	7.8
V	9.4

The ASA scheme is the most comprehensive system, but it does not embrace all aspects of anesthetic risk, as there is no allowance for inclusion of many  criteria such as age or smoking history or obesity or pregnancy or difficulty in intubation or the risk of the a symptomatic patient who may have severe coronary artery disease. it also disregards the inherent risks of a particular operation.

TYPE OF ANAESTHESIA

General, spinal, epidural and regional [local] are the modes of anesthesia. The basis of modern mode of anesthesia is to achieve an adequate level of anesthesia with short acting drugs like propofol, midazolam, fentanyl, sufentanul, atracurium and vencuronium. These drugs are potent and cause less side effects. Commonly used inhalational anaesthetic agents are nitrous oxide, halothane, isofluorane, sevofluorane and desfluorane.

The necessary muscular relaxation for intubation is achieved either by long acting or short acting muscle relaxants. Long acting muscular relaxants such as pancuronium, vencuronium and atracunium cause relaxation by competing with acetyl choline at motor end plate. Succinyl choline is another muscular relaxant, which causes persistent depolarization of motor end plate and rendering it in excitable to acetylcholine. When short acting muscle relaxant such as succinyl choline is used, relaxation lasts only 5-10 minutes and it is mostly used for endotracheal intubation.

Antagonists of muscle relaxants are ganglion blocking agents and they act by competing with acetylcholine. The muscle relaxant effect can be reversed with neostigmine, provided the patient shows signs of recovery from the muscle relaxant effects, which is ascertained by the patient’s attempts of respiration and movements of small muscles – eyebrows, eyeball muscles and tongue muscles.

The action of succinyl choline is self-limiting as it gets metabolized by enzyme [pseudo-cholinesterase] degradation. If pseudo-cholinesterase is low or absent, it results in prolonged apnoea, which is otherwise known as scoline apnoea and it is a treatable condition.

Causes of Anesthesia – related Deaths

Any of the following factors maybe responsible for death during anesthesia:

1. Vagal stimulation while intubating an endotracheal tube;
2. As a result of faulty use of relaxants and hypotensive drugs;
3. Accidents, which may cause obstruction of airway or spasm resulting in asphyxia;
4. The amount and type of drug used for anesthesia and duration of anesthesia may have a fatal effect;
5. Hypotension, as a result of spinal anesthesia;
6. Anaphylactic reaction due to the drugs used in local or spinal anesthesia; and
7. Inadvertently giving a hypoxic mixture of gases [the oxygen content is less than the required amount] during anesthesia;

Gordon and Shapiro classify the causes of anesthetic deaths into two groups:

i) Deaths which occur during the administration of anesthesia, but which are not due to the anesthesia; and

ii) Deaths which are the direct result of the administration of an anesthetic drug.

Deaths which Occur during the administration of Anesthesia, but which are not Due to the Anesthesia

There are various sub-categories under this group;

1. Deaths due to the Injury or Disease which Necessitated the Operation and Administration of Anesthesia

When the injury [or disease], which necessitated the operation, is of a sufficiently serious nature to account for death, the injury [or disease] may be regarded as the principal factor which caused the death, even though the operation and the anesthesia may have precipitated the death. Several anesthesia-related deaths are classifiable under this sub- group.

(ii) Deaths due to a Disease other than that for which the Operation was Undertaken, but which was Diagnosed before the Operation was Commenced

When a patient who suffers from a serious ailment like valvular disease of heart has to undergo an operation for another disease or injury, the risk to his life may be greatly increased. However, the surgery performed under anesthesia may be beneficial to the patient. In such circumstances, if the patient dies during surgery, it may be essentially considered to be due to natural causes even though the operation and the anesthesia may have precipitated the death. However, a competent anesthetist would be expected to make due allowance for such pre-existing disease.

(iii) Deaths due to Disease other than that for which the Operation was undertaken, but which was not Diagnosed before the Operation was Commenced.

An autopsy of the patient died in the preoperative [around the time of operation] period may reveal a serious lesion that could have been an important contributory factor in causing the death of the patient, but which was not diagnosed before the surgery was commenced. There are several diseases like coronary artery arteriosclerosis, which may be clinically latent and which may not be detectable even after the most careful routine clinical examination and appropriate investigations. The failure to make a preoperative diagnosis of such a condition does not necessarily imply that the anesthetist was negligent. In such situations, it has to be established whether the medical practitioner in attendance could reasonably have diagnosed the condition by a proper preoperative clinical examinations and other laboratory investigations.

(iv) Surgical Deaths

A surgical mishap during the administration of the anesthesia may be responsible for the death of a patient. For instance, the accidental incision of a large blood vessel or aneurysm is the direct responsibility of the surgeon. Shock due to operation itself, myocardial or coronary disease of the heart, fat or air embolism, hypothermia or incompatible blood transfusion may be other causes. Similarly massive blood loss and the subsequent hypovolemia can also cause death.

Deaths which are the Direct Result of the Administration of Anesthesia: The state of general anesthesia of necessity deprives the patient of the majority of his protective reflexes. Consequently, homeostatic mechanisms are disturbed, particularly those pertaining to the respiratory and cardiovascular systems.

Death due to Respiratory Failure: Problems pertaining to the respiratory system are the single largest cause of death. respiratory failure in the anaesthetized patient may develop insidiously, as respiratory distress may not be obvious and cyanosis is a late sign. A serious degree of hypoxia may develop unless the anesthetist maintains a high level of vigilance.

Airway Obstruction Loss of protective reflexes as a result of anesthesia frequently leads to obstruction of the upper airway by the soft tissues of the mouth and pharynx. Irritation of the larynx during a light plane of anesthesia may provoke laryngeal spasm and consequent hypoxia; it is seldom fatal since the spasm usually fades away before the hypoxia becomes lethal. The larynx and trachea may become obstructed as a result of secretions or foreign bodies like dentures or vomiting that may happen when the patient is in full stomach and a surgery is performed in emergency. Similarly, inadvertent misplacement of the endotracheal tube may occur. Bronchiolar spasm may contribute to airway obstruction and may be due to many factors including pre-existing asthma, hypersensitivity to drugs, aspiration of gastric contents and fluid overload.

Pneumothorax: Rupture of the lungs may result from the application of excessive pressure to the airway, but may also occur at normal ventilatory pressure if there is a pre-existing weakness in the lung. Positive pressure ventilation will rapidly convert a simple pneumothorax into a tension pneumothorax with life-threatening consequences. Similarly, the use of nitrous oxide will cause a pneumothorax to expand rapidly and may contribute to a fatal outcome.

Aspiration of Gastric Contents:

Respiratory Depression:

Equipment Failure:.

Deaths due to Cardiovascular Failure during anesthesia: All forms of anesthesia alter cardiovascular homeostatic mechanisms to a greater or lesser extent. Disorders of circulatory homeostasis from the second largest group of anesthesia-related deaths. General anesthetic agents lower peripheral vascular resistance by depressing sympathetic outflow from medullary centres. In addition, they all display some calcium antagonism, and thus have direct vasodilator properties, as well as exerting a depressant action on the myocardium. These principal actions may be masked with some agents by a concomitant release of catecholamine.

When a patient is under anesthesia, cardiac arrest occurs in the following ways:

1. By pure asphyxial action on the heart muscle, which having to beat under hypoxic conditions, progressively builds up a larger and larger debt and ultimately stops;
2. Reflexly as a result of vagal stimulation.
3. Hypovolaemia: Unrecognised or inadequately managed hypovolaemia is the commonest cause of anaesthesia-related death attributable to the cardiovascular system.
4. Cardiac Arrhythmias:
5. Diminished Myocardial Contractility:

Complications of Regional Anaesthesia

Systemic toxicity, most commonly manifested in the central nervous system, producing convulsions. It may be due to accidental or inadvertent intravascular injection of drugs.

Regional anesthetic procedures around the spinal column such as epidural, spinal and paravertebral blocks may cause death through cardiovascular collapse from autonomic blockade, or by respiratory paralysis or both. Procedures involving the chest wall such as potentially fatal pneumothorax, and procedures in the neck may block the phrenic nerve, which may lead to respiratory failure in a patient with pulmonary disease.

Adverse drug reactions

Adverse reactions to anaesthetic drugs are not uncommon, but infrequently lead to death. Patients may develop anaphylactic reactions to drugs like xylocaine and die. In such situations, full resuscitative facilities and expertise should be immediately made available in the operation theatre. The frequency of these reactions has recently been estimated at about 0.2 % of all am aesthetics and although some are of the minor histaminoid type, most presented with life-threatening bronchospasm and acute hypotension. Anaphylaxis does not occur in response to inhalational agents.

It should be noted that there is no reliable screening test for allergy to particular drugs, and therefore no method of predicting anaphylaxis in any particular patient. The occurrence of anaphylaxis is about three times more common in women than in men. Reactions normally occur within minutes of exposure to the drug, and the dose given may be very small. This suggests that the common practice of giving a small ‘test dose’ before the main dose of a drug such as xylocaine or penicillin has no validity.

Other factors

Malignant hyperpyrexia is a rare inherited condition triggered by various anesthetic agents. Careful family history and muscle biopsy help to diagnose the condition. It is characterized by a rapid rise of body temperature with muscle rigidity followed by severe metabolic disturbances and death. Administration of dantroline sodium will abort the attack.

Air embolism most commonly occurs during neurosurgical procedures undertaken in sitting position, with the air entering the venous system through vessels in the skull bones. Similarly, fat embolism may occur due to obesity or in surgeries involving long bones.

Electrocution due to defective equipment has caused deaths in the operation theater. Even very small currents may lead to ventricular fibrillation in the presence of intracardiac leads and catheters.

Post-Mortem

The findings at autopsy will vary according to the cause of death. there are no diagnostic findings at autopsy in most instances of anesthesia-related deaths because there are no pathognomic pathological changes found in deaths caused neither by anoxia nor in acute cardiovascular collapse unless there is some underlying cause, such as a myocardial infarction. While doing a post-mortem, it is difficult to evaluate the cause of death, as usually there is no evidence of sudden fall of blood pressure, cardiac irregularities or epiglottic spasm, which may have been responsible for causing sudden death.

Exterior of the body should be carefully examined looking for external , evidence of therapy, including wounds, scars, repairs, and other procedures. Occasionally, the odour of anesthetic agent may be smelt. The changes in the organs are of hypoxia. Alveolar air should be collected with a syringe by pulmonary puncture. Before chest is opened, blood should be collected under oil and both lung and brain saved and quick-frozen. In cases of spinal anesthesia, cerebro-spinal fluid (CSF) should be collected for chemical analysis. The sample of gases used for anesthesia should also be sent for chemical analysis to know whether they were proportionately mixed before use. Gas chromatography study is done to evaluate the concentration of gases present in the viscera.

When air embolism is suspected to be the cause of death, abdominal cavity should be opened first and inferior vena cava should be inspected for air bubbles. To exclude the possibility of post-mortem putrefaction gas, samples withdrawn in a syringe should be sent for chemical analysis. Similarly, culture of blood and exudates and histopahtological examination of tissue samples from heart, liver, kidney and brain should be done. Serological examination to rule out the possibility of serologic reactions due to the transfusion of wrong blood group should also be done.

When death occurs from hypovolaemia, autopsy is frequently negative in establishing the cause.

When death occurs subsequent to the administration of local anesthesia, the autopsy findings are those of hypoxia. The injection site, blood, and liver should be sent for toxicological identification of local anesthetic and its metabolic breakdown products.

The explosive nature of anesthetic gases is well known. With muscle relaxants and assisted respiration, it is not uncommon for the stomach to be filled with anesthetic agent. This is an unusual type of hazard which the autopsy surgeon should consider in post-anesthetic combustion of any type.

While interpreting the toxicological report, it should be remembered that some drugs may either potentiate or alter the function of anesthetic agents.

The cause of death will usually be a complicating circumstance rather than specific over dosage with an anesthetic agent. Assignment of the exact cause of death in the operative or immediate post-operative period is one of the most difficult tasks which fall to the forensic expert. A full clinical history is necessary, together with consultation with the surgeon or other medical staff, in order to arrive at the best possible opinion as to the reason for the death. where pre-existing natural disease, especially heart disease is present, the contribution of this to the cause of death must be estimated. Similarly, respiratory insufficiency due to lung disease may be a potent factor in causing death. in aged  or debilitated persons, who may be a poor risk for operation, account must be taken of the condition of their myocardiurn and lungs. In operations on persons already shocked from trauma, and evaluated.

Liability of an Anaesthetist:

1. Was informed consent obtained for the operation and the administration of anesthesia?
2. Were an operation and/or the administration of anesthesia necessary in the circumstances?
3. Was the patient properly examined before the operation and was his fitness to undergo the operation assessed preoperatively with reasonable skill and care?
4. Was the patient suitably prepared for the operation and the administration of the anesthesia?
5. Was the patient given test dose to rule out sensitivity before the drugs used in spinal or local anesthesia was administered?
6. Was suitable type of anesthesia administered?
7. Was the anesthesia administered and the operation performed with reasonable skill and care?
8. Were suitable and adequate arrangements made before the operation to deal with any emergency which might arise during the administration of the anesthesia?
9. When the emergency arose, were suitable steps taken immediately to resuscitate the patient?
10. Were suitable and adequate arrangements made to ensure the safe recovery of the patient?

Note: The above criteria are applicable only when a patient underwent an elective surgery.