Postoperative delirium in the elderly

Abstracts

JUSTIFICATIVA E OBJETIVOS: O delirium pós-operatório é complicação comum na faixa etária avançada, tem fisiopatologia pobremente esclarecida e tem como um dos sintomas o delírio. O delírio parece estar relacionado com a atividade colinérgica central. O objetivo deste artigo foi descrever a etiologia, o diagnóstico, as estratégias de prevenção e o tratamento do delirium pós-operatório por meio da revisão de literatura. CONTEÚDO: Foram descritos as prováveis etiologias, o diagnóstico, a prevenção e o tratamento do delirium pós-operatório em idosos. CONCLUSÕES: A incidência de delirium pós-operatório é maior nos pacientes idosos e as estratégias de prevenção devem ser utilizadas para redução da mortalidade associada a essa complicação anestésico-cirúrgica.

CIRURGIA; COMPLICAÇÕES; COMPLICAÇÕES

MISCELLANEOUS

Postoperative delirium in the elderly^*

Delirium postoperatorio en ancianos

Fabiano Timbó Barbosa, TSA, M.D.^I; Rafael Martins da Cunha, M.D.^II; André Luiz Carvalho Leme Teixeira Pinto, TSA, M.D.^III

^IAnestesiologista da Unidade de Emergência Armando Lages e do Hospital Escola Doutor José Carneiro; Médico Intensivista da Clínica Santa Juliana; Especialista em Docência para o Ensino Superior; Tutor da Liga de Anestesia, Dor e Terapia Intensiva de Alagoas

^IIProfessor de Farmacologia do Centro de Ensino Superior de Maceió; Professor Convidado de Farmacologia da Faculdade de Medicina da Universidade de Ciências da Saúde de Alagoas; Anestesiologista do Hospital Unimed, Maceió; Tutor da Liga de Anestesia, Dor e Terapia Intensiva de Alagoas

^IIIProfessor Honorário da Liga de Anestesia, Dor e Terapia Intensiva da Universidade Estadual de Ciências da Saúde de Alagoas; Título de Médico Associado da Faculdade de Medicina da Universidade Louis Pasteur, Estrasburgo

Correspondence to

SUMMARY

BACKGROUND AND OBJECTIVES: Postoperative delirium is a common complication in the elderly whose pathophysiology is not well known. It seems to be related to central cholinergic activity. A literature review was undertaken to describe the etiology, diagnosis, prophylactic strategies, and treatment of postoperative delirium.

CONTENTS: Probable etiologies, diagnosis, prophylaxis, and treatment of postoperative delirium in the elderly were described.

CONCLUSIONS: The incidence of postoperative delirium is higher in the elderly, and prophylactic measures should be taken to reduce the mortality associated with this complication.

Key Words: COMPLICATIONS: delirium; SURGERY: elderly.

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: El delirium postoperatorio es una complicación común en la franja etaria avanzada, tiene una fisiopatología muy mal aclarada y posee como uno de los síntomas, el delirio. El delirio parece estar relacionado con la actividad colinérgica central. El objetivo de este artículo fue describir la etiología, el diagnóstico, y las estrategias de prevención y tratamiento del delirium postoperatorio a través de la revisión de la literatura.

CONTENIDO: Se describieron las probables etiologías, diagnóstico, prevención y tratamiento del delirium postoperatorio en ancianos.

CONCLUSIONES: La incidencia de delirium postoperatorio es mayor en los pacientes ancianos y las estrategias de prevención deben ser utilizadas para la reducción de la mortalidad asociada a esa complicación anestésico-quirúrgica.

INTRODUCTION

Advances in surgical techniques and anesthetic care resulted in a substantial reduction in perioperative mortality and morbidity in the elderly ¹. Patients with multiple associated diseases are now treated surgically in later stages of life ¹. Some degree of cognitive dysfunction after general anesthesia in some patients has been recognized since 1950, and advanced age is the main risk factor associated with this transitory event ^2-4.

Postoperative cognitive deterioration can be classified in two main categories: delirium and moderate neurocognitive dysfunction, known in the literature as postoperative cognitive dysfunction (POCD) ⁵. Delirium is a transitory clinical entity that has been associated with an increase in mortality ⁶, and POCD is a condition characterized by impaired memory, concentration, language comprehension, and social integration ^2,7.

A review of the literature was undertaken to describe the etiology, diagnosis, prophylactic strategies, and treatment of postoperative delirium.

POSTOPERATIVE DELIRIUM

The elderly usually awake slowly from anesthesia, demonstrating coherence in post-anesthetic recovery, and are discharged without intercurrences; however, some of them develop a state of confusion after this period of normalcy, known as post-operative delirium (POD), which might present hours to days after the procedure ⁸. Therefore, postoperative delirium can be defined as a transient and fluctuating disturbance of consciousness, attention, cognition, and perception that complicates the evolution of up to 36.8% of surgical patients ⁹.

The incidence of this disorder varies with the type of surgery ^6,8,10. It has a 47% incidence after large size cardiac surgeries ⁶, 10% after general surgeries ⁶, 50% after orthopedic surgeries ⁶, and up to 62% after surgery for hip fractures ^8,10. Extracorporeal circulation seems to be another risk factor strongly associated to the postoperative disruption of cognitive function ^9,11-14, and high doses of fentanyl seem to protect against this deterioration in large size cardiac surgeries ¹¹.

Postoperative dementia has a 13% mortality rate ⁶. Approximately 72% of elderly patients with POD die within five years after the surgery, compared to 34.7% of those who remain lucid during the postoperative period ⁶. Postoperative dementia is also associated with an increase in the length of hospitalization, complications, and hospital costs ^6,15, besides representing a negative impact in the quality of life of the elderly ¹⁵.

ETIOLOGY AND RISK FACTORS

The true etiology of POD is not clearly determined, but some factors have been listed as probable causes (Table I) ^1,6.

The pathophysiology of delirium remains unknown, but some hypotheses have been suggested, such as: disruption of glutaminergic activity ¹⁵, decreased muscarinic activity ^1,6,8,9,15, increased dopaminergic activity ⁹, and the combination of the last two factors ⁹.

There are five types of muscarinic receptors involved in the regulation of the nervous system and circulatory homeostasis ⁶. They are responsible for the regulation of consciousness, cognitive function, and pain perception and contribute to the regulation of circulatory function ⁶. Suppression of cholinergic cells is one of the mechanisms partly responsible for anesthesia ⁶ and for this reason general anesthesia has been implicated as a risk factor for POD ^4,6,15. Propofol and volatile agents inhibit cholinergic receptors, while atracurium and its metabolite laudanosine activate them⁴. Morphine in clinical doses is an antagonist of M1, M2, and M3 muscarinic receptors, fentanyl is a strong competitive antagonist of M3 receptors, and remifentanil does not affect significantly the release of acetylcholine ⁶.

The use of drugs with cholinergic activity also corroborates the cholinergic etiology hypothesis of delirium ^1,16, and physostigmine, which has central cholinergic activity, has been successfully used in the treatment of patients with delirium ¹⁶. The cholinergic model has also been supported by the observation that hospitalized elderly patients developed delirium after the administration of diphenidramine ⁹.

Surgical trauma causes a well-known neuroendocrine disruption, with release of cortisol and cytokines, and reduction in the activity of thyroid hormones ¹. Changes in hormonal levels promote changes in the concentration of neurotransmitter amino acids and can also cause delirium ¹⁷. The association between cognitive function and high levels of cortisol has been reported in the literature ^18,19.

Other risk factors besides advanced age, extracorporeal circulation, and general anesthesia include: alcohol abuse ⁶, poor cognitive and functional state ^1,6, type of surgery⁶, use of drugs with anti-cholinergic activity ¹, dementia ¹, depression ¹, psychosis ¹, nutritional deficiency ^1,6, low educational level ⁴, reoperation ⁴, surgical infection ⁴, and respiratory complications ⁴.

Hypotension ¹⁹, hypothermia ¹⁹, and mild hypoxemia ¹ are not considered risk factors due to the lack of a consensus among the different authors ¹.

DIAGNOSIS

The clinical manifestations of POD include ¹: delirium, disorientation, language difficulties, and impaired learning and memory. Emotional changes may be prominent, such as ¹: anxiety, fear, irritability, anger, and depression. Illusion and hallucinations can also be present ⁸. Patients may complain of failure to perform simple mental tasks that they used to do before the surgery, such as ¹⁹: crossword puzzles and moving from one room to the other and forgetting what motivated this dislocation. The severity of the symptoms may vary during the day ⁹ and they can persist for days or weeks ¹.

Patient history should be complemented with the physical exam, other tests to rule out associated diseases and drug intoxication, and scales that assess the cognitive function ¹. The scales used more often include the Confusion Assessment Method - CAM, whose Portuguese version has been validated (Table II) ^1,16, and the Mini Mental State Examination ^10,20.

The presence of items 1 and 2 along with item 3 or 4 is diagnostic of delirium ¹⁶. After the syndromic diagnosis, emphasis should be on the etiological diagnosis ¹⁶.

The Mini Mental State Examination assesses orientation, registration, memory, degree of attention, and calculus and language ²⁰. A score of 20 or less out of the maximum total of 30 indicates dementia ²⁰. The test has a sensitivity of 80% and specificity of 98% ¹⁰.

PREVENTION STRATEGIES

The prophylaxis of delirium is probably the most effective strategy to reduce its incidence ¹. The principles of prophylaxis include ¹: assessment and treatment of associated diseases, detailed history of current medications, history of alcohol or illicit drug use, avoid the pre- and intraoperative use of anti-cholinergic drugs, avoid dehydration, maintain electrolyte balance, avoid pain, and give support to withdrawal syndrome. Several studies have demonstrated that combinations of several strategies reduce the incidence of postoperative delirium in the elderly ²¹.

Patients with physical status higher than ASA II have a higher incidence of POD ¹. Optimization of preoperative clinical status reduces the incidence of POD ¹. Antidepressants used chronically should not be discontinued ²².

Although hypoxemia and hypotension are not universally accepted as risk factors, it seems reasonable to avoid their development during anesthesia ¹.

TREATMENT

Treatment of POD is based primarily on recognition and adequate management of probable causes ¹. Initially, the following tests can be requested ¹: blood glucose levels, blood electrolytes, arterial blood gases, chest X-ray, complete blood count, and blood cultures ¹. Pain should be treated¹, haloperidol ^1,8 or chlorpromazine ¹ should be used in case of agitation, and benzodiazepines should be used in alcohol withdrawal ⁸.

Haloperidol can be administered intravenously, 0.5 to 1.0 mg every 15 minutes until agitation is controlled ⁸. If one chooses the intramuscular route, doses may vary from 2 to 10 mg, with a 90-minute interval between doses. The elimination half-life of haloperidol in the elderly can reach 72 hours ⁸.

Supportive treatment, with adequate ventilation, oxygenation, and stabilization of hemodynamic parameters seem prudent and should also be done¹.

Physostigmine has been successfully used to reverse the effects of central anti-cholinergic and can also be used in the treatment ¹.

FINAL CONSIDERATIONS

Delirium is a syndrome that develops in the postoperative period, which is more common in the elderly, and can last days or weeks ¹. Preoperative medical condition, cognitive state, psychological factors, and age can predispose the patient to delirium¹. Prevention is the most effective conduct, since treatment after the development of this condition is not highly successful.

The incidence of postoperative delirium is higher in the elderly, and prophylactic strategies should be used to reduce the mortality associated with this anesthetic-surgical complication.

REFERENCES

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Publication Dates

• Publication in this collection
  14 Nov 2008
• Date of issue
  Dec 2008

History

• Accepted
  18 Aug 2008
• Received
  05 Sept 2007