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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094

Rev. Bras. Anestesiol. vol.54 no.5 Campinas Sept./Oct. 2004

http://dx.doi.org/10.1590/S0034-70942004000500014 

MISCELLANEOUS

 

Peculiarities of post-cardiac surgery care in elderly patients*

 

Peculiaridades en el post operatorio de cirugía cardíaca en el paciente de edad avanzada

 

 

Paulo de Oliveira Vasconcelos Filho, TSA, M.D.I; Maria José Carvalho Carmona, TSA, M.D.II; José Otávio Costa Auler Júnior, TSA, M.D.III

IFellow do CTI do Hospital Israelita Albert Einstein. Especialização em Pós-Operatório de Cirurgia Cardiovascular e Torácica pelo InCor - HC - FMUSP
IIProfessora Doutora da Disciplina de Anestesiologia da FMUSP. Médica Supervisora do Serviço de Anestesiologia e Terapia Intensiva Cirúrgica do InCor - HC - FMUSP
IIIProfessor Titular da Disciplina de Anestesiologia da FMUSP. Diretor do Serviço de Anestesiologia e Terapia Intensiva Cirúrgica do InCor - HC - FMUSP

Correspondence

 

 


SUMMARY

BACKGROUND AND OBJECTIVES: Elderly patients have their own physiologic characteristics, and sometimes may have organic deficits or severe diseases, which by themselves may complicate the postoperative period. This article is aimed at reviewing post-cardiac surgery procedures in the elderly, describing their most frequent problems.
CONTENTS: Elderly patients intraoperative approaches should be decided taking into account lower postoperative morbidity. At ICU arrival, the same criteria for other adult patients of cardiac surgeries should be adopted to maintain service standardization and routine, thus preventing mistakes. Establishing an intensive care plan for the post-cardiac surgery period may result in optimal use of resources, effective attention and decreased time of care. Subsidiary exams should also follow the standards of the service, unless any problem be identified. Neurological, pulmonary and circulatory complications, renal failure, infections and hypothyroidism outlined in this article are frequent and unique in the elderly, and should be fully understood by the ICU physician.
CONCLUSIONS: Complications outlined in this article are those of greatest concern for the ICU physician when there are elderly patients in the post-cardiac surgery period. These patients need special care, even when surgery is perfectly normal, because there is major surgical stress and the elderly have decreased functional reserves.

Key Words: COMPLICATIONS, postoperative; POSTOPERATIVE EVALUATION; SURGERY, Cardiac: elderly


RESUMEN

JUSTIFICATIVA Y OBJETIVOS: El paciente de edad avanzada tiene características fisiológicas propias y, muchas veces, puede presentar deficiencias orgánicas o afecciones graves, que por si, ya tornan el post operatorio complicado. El objetivo de este artículo es presentar una revisión de las conductas post operatorias de cirugía cardíaca en el paciente de edad avanzada, presentando las alteraciones más frecuentes en ese tipo de paciente.
CONTENIDO: Las conductas en el período intra-operatorio del paciente de edad avanzada deben ser tomadas teniendo en vista la diminución de la morbidez post operatoria. En la llegada del paciente de edad avanzada a la UTI, deben ser cumplidos los mismos criterios utilizados en la internación de otros pacientes adultos de cirugía cardíaca, para que el servicio tenga siempre un patrón, que no lleve a una alteración en la rutina y que no provoque equívocos. Establecer un plano de cuidados intensivos para el post operatorio de cirugía cardíaca irá resultar en una óptima utilización de recursos de la unidad, en efectividad de atención y en diminución del tiempo en los cuidados en relación al paciente de edad avanzada. Los exámenes auxiliares solicitados también deben seguir un patrón, establecido por el servicio, a menos que cualquier problema se identifique. Complicaciones neurológicas, pulmonares, circulatorias, insuficiencia renal, infección e hipotiroidismo son frecuentes, con particularidades en el paciente de edad avanzada, están delineadas en este articulo y deben ser bien comprendidas por el intensivista que cuida de ese tipo de paciente.
CONCLUSIONES: Las complicaciones presentadas en este artículo son las que traen mayor preocupación al intensivista, cuando hay un paciente de edad avanzada en el post operatorio de cirugía cardíaca en la UTI. Este paciente necesita de cuidados especiales, aún cuando la cirugía transcurre en perfecta normalidad, pues el estrés quirúrgico es muy grande y el paciente de edad avanzada tiene reserva funcional diminuida.


 

 

INTRODUCTION

Increased life expectation has generated an increased number of surgical procedures in elderly patients (above 64 years of age) 1. So, there is an increasing need for preparing health professionals involved with this situation. Elderly patients have their own physiological characteristics and may present organic deficits or severe diseases, which may complicate the postoperative period 2,3.

Cardiac surgery is a complex procedure implying changes in several physiological mechanisms, contact with drugs and materials, which may be noxious to the body or even major organic stress 4,5. Intensive postoperative care is needed to assure patients’ successful recovery. Regardless of all care, difficult to control diseases may appear in the postoperative period which may cause severe sequelae or even patients’ death 2. Because elderly patients have limited organic reserves, the postoperative period should be a stage of assisted recovery to prevent most possible organic injuries.

This article aimed at reviewing post-cardiac surgery approaches for the elderly outlining their most common complications.

 

GENERAL CONSIDERATIONS

Systemic diseases are common in the elderly and may lead to function loss in more than one organ or to generalized body dysfunction 2,6,7. Preoperative functional evaluation of those organs is critical and will be the basis for postoperative follow up 2,6.

Several studies suggest that elderly patients have significant increase in the incidence of perioperative death and complications, such as renal failure, prolonged ventilation, stroke and postoperative cardiac arrest 1,2,4,6,8,9, Older patients have increased incidence of vascular diseases, such as diabetic vasculopathy, peripheral vascular disease, brain vascular disease and hypertension 1,3,4,6,10-12. These are important factors for postoperative evolution.

Even with the risk of age or of advanced disease, today patients have good results as compared to patients submitted to surgeries 10 years ago 4,13. There have been major cardiac surgery advances and currently a wide range of cardiac disorders has alternatives to surgery 4,13,15. Advances in minimally invasive cardiac surgery have made it an interesting option because recovery tends to be shorter; however, the patients have to be carefully evaluated 13.

 

PHYSIOLOGICAL CONSIDERATIONS

Aging is a global and progressive physiological process with measurable structural changes and decreased tissue and organic function (Chart I), but that is enough to maintain patient alive 15. Changes, which are not universal and do not increase according to chronological age are probably not aging manifestations, but rather signs and symptoms of diseases in general related to aging. Although its cellular and biochemical mechanisms are not fully understood, decreased cell energy production due to mitochondrial genome deterioration, especially on cardiac and nervous tissues, may play a fundamental role in aging-related organic systems deterioration 16.

Another important aging data is that general decrease in arteries elasticity promotes increased impedance to ventricular ejection changing cardiac output distribution to other organs 4,6,10.

With decreased splanchnic artery flow, there is hepatic flow decrease which may be very significant, changing perfusion of different tissues 10. In the kidney, for example, this perfusion decrease, associated to decreased glomerular function, also due to age, may lead to increased plasma creatinine levels. The presence of diabetes mellitus, congestive heart failure, hypertension, neurotoxic drugs and cardiopulmonary bypass may worsen this renal dysfunction 17,18.

There is a higher prevalence of coronary failure, but diagnosis is more difficult due to physical activity limitations and decreased probability for angina 6. In addition to increased systemic vascular impedance, age effects, such as compliance and muscle relaxation disorders, decreased response to b-adrenergic stimulation and myocardial metabolism changes, lead to a condition favoring congestive heart failure. The level of heart involvement should always be evaluated before surgery 20.

Brain blood flow auto-regulation may also be impaired by aging 12,21,22. In younger people, normal brain vascular bed responds to blood pressure, O2 tension, CO2 tension and brain metabolism. In the elderly, these responses are decreased. In addition, there are other adverse effects along time acting on auto-regulation, such as uncontrolled hypertension, cardiac dysfunction and smoking. These conditions associated to aging have a major impact on brain vascular system 21.

Pulmonary function deteriorates with age and this deterioration may be further exacerbated in patients with history of smoking, chronic bronchitis and emphysema. Age-induced primary lung deficits in healthy people is gradual elastic retraction loss, which decreases expiratory flow and increases inefficiency of ventilation and perfusion areas 2,23.

 

PREOPERATIVE CONSIDERATIONS

The role of preoperative status and patients’ selection on postoperative (immediate and late) results should not be underestimated 2. Careful patients selection may help explaining different morbidity and mortality rates of cardiac surgeries in elderly patients among different centers 3,4. Preoperative factors influencing results may be of cardiac or non-cardiac source. Among non-cardiac causes, one may mention, especially in elderly females, the high incidence of chronic renal, pulmonary neurological and GI tract diseases 2.

Among cardiac causes, there are anatomic localization of cardiac disease (coronary artery, valvar, myocardial artery); the level of myocardial dysfunction (that is, ejection fraction); previous cardiac surgery and severity of clinical presentation. All have major impact both in elderly and in younger patients. Elderly, however, are more affected by left ventricular hypertrophy, decreased ejection fraction, critical aortic stenosis, previous acute myocardial infarction, more severe aortic regurgitation or mitral failure, and have a more acute clinical presentation (instability, bed rest or angina post acute myocardial infarction).

Concerning the coronary artery disease, elderly patients are more often admitted with acute symptoms and present a higher incidence of triple vascular disease, co-morbidities and a poorer condition to receive internal mammary artery anastomosis. The presence of valvar changes with concomitant coronary disease (mainly mitral valve disease) increases surgical time, morbidity and mortality 2,14,24.

Knowing that peripheral and brain vascular diseases are increased with age, some authors have advocated (even in the absence of signs and symptoms) that elderly patients should be routinely submitted to carotid Doppler 2.

Although most ICU severity scores have had an improvement of 2 to 3 generation (e.g.: Apache II, Apache III; MPM I, MPM II, etc.), they are still inadequate for cardiac surgery prognosis. All cardiac surgery patients were excluded from MPM I and II and from SAPS II. Patients submitted to myocardial revascularization were excluded from Apache III. A score that may be used with elderly patients is the score developed by the Northern New England Cardiovascular Disease Study Group (Table I and Table II), which preoperatively estimates the risk for mortality, stroke and mediastinitis in patients submitted to myocardial revascularization. Data from table I have generated risk percentages of table II 25.

If there is a history of recent upper airway infection, cardiac surgery should be postponed, whenever it is possible. Preoperative pulmonary function tests should be performed and efforts should be directed to optimize patients’ pulmonary profile (that is, pulmonary physical therapy, antibiotics and bronchodilators). In patients with impaired pulmonary function, cardiopulmonary bypass during revascularizations should be carefully evaluated and, if possible, techniques without bypass should be used 2.

Elderly cardiac surgery time should always be discussed with careful considerations, taking into account co-morbidities and physiological stability impairment. Postponing for some days or even some weeks to obtain maximum allowed improvement in organic functions and symptoms might result in better prognosis. For many patients, postponements are impossible due to urgency or emergency of the situation. But even for those cases, preoperative investigation should be as thorough as possible, with evaluation by the team members 2.

 

INTRAOPERATIVE CONSIDERATIONS

Intraoperative approaches for elderly patients should consider peculiarities of this age bracket and should be adopted aiming at decreasing postoperative morbidity. Surgery should be well planned for patients to arrive relaxed in the operating room and for the surgery to be performed in optimal time not to prolong anesthesia. Cardiopulmonary bypass duration is also critical because it is known that the higher the perfusion times, the higher the postoperative organic repercussion 4.

Anesthetic induction should respect patients’ previous condition, without sudden blood pressure decrease (leading to poor organic perfusion) or hypertensive peaks allowing for strokes in noble organs. Monitoring should be as thorough as possible with oximetry; cardioscopy with ST segment monitoring (for early intraoperative ischemia detection); invasive blood pressure after Allen’s test because there is the possibility of peripheral artery involvement in the elderly; temperature; diuresis; and Swan-Ganz catheter, which contributes for a more accurate hemodynamic control, critical for elderly patients. The use of Swan-Ganz catheter should always be considered. Transesophageal echocardiography, increasingly adopted, may be useful in different situations, such as valve replacements and low output syndromes 4,26.

Volume control is critical for elderly patients because hypovolemia may promote hypotension with low cardiac output. Excess of volume changes heart filling pressures and may lead to fluid leakage to cavities. In addition, the interstitial oxygen diffusion is difficult in hyper-hydrated patients. Diuresis monitoring is extremely important since the elderly have decreased renal clearance and volume changes could impair renal function even further 26,27.

High plasma creatinine levels are an independent risk factor for increased morbidity and mortality of cardiac surgery patients. Several recommendations have been made to decrease this complication, including pulsatile flow during CPB in patients with known renal dysfunction, free radical blockers to decrease some effects of systemic inflammatory response to CPB, routine use of mannitol in the CPB pump prime (initial perfusion solution) and postoperative dopamine 28,29.

When CPB is used, it is necessary to pay attention to coagulation problems, because changes in platelet number and function and coagulation factor deficiencies lead to major coagulopathies which increase perioperative morbidity and mortality. Currently, with the use of anti-fibrinolytic substances, such as amino-caproic acid and aprotinin, bleeding is diminished until coagulation normalization. Attention should also be paid to anemia at the end of CPB. If necessary, proceed to blood transfusions as early as possible, as soon as the problem is diagnosed 4,26.

Temperature control is also critical for elderly patients care. Hyperthermia and hypothermia periods should be avoided during surgery, allowing just controlled hypothermia during CPB. During post-anesthetic recovery and transportation to the ICU, elderly patients will have difficulties in maintaining and recovering temperature. There are changes in primary temperature regulation mechanisms, such as decreased subcutaneous tissue and loss of peripheral vasoconstriction mechanism. In response to cold, the hypothalamus stimulates sympathetic nervous system for catecholamine release, increasing heart rate, cardiac output and blood pressure. Extrapyramidal tract stimulation increases muscle tone promoting rhythmic muscle contraction (shivering), with increased oxygen consumption, that is dangerous for the elderly 26,30.

Finally, in spite of modern intraoperative myocardial protection and surgical techniques improvement, some amount of uniform ischemia may be present during surgery. The incidence of acute myocardial infarction varies 5% to 15% in patients submitted to revascularization. Even with perfect protection, surgical intercurrences (such as anastomotic fistulas) or non-surgical intercurrences (such as aneurysms and plaques in cardiac arteries) may promote it 4.

 

POSTOPERATIVE MANAGEMENT

Arrival to the Intensive Care Unit

At ICU arrival, the same criteria adopted for other adult patients should be followed for the elderly to maintain routine unchanged and prevent mistakes. Establishing an intensive care plan for the post-cardiac surgery period will result in optimal use of resources, effective attention and decreased time for elderly patients care. The intention is to improve cost-benefit ratio and maximize ICU care quality 2,29.

The exams requested should also follow the standard established by the service, unless patients present with a disease which should be further investigated. Pre and intraoperative data should be discussed with the ICU physician for him/her to be prepared to face risk situations. Previous lab test results are very useful to show how patient has evolved in the intraoperative period and help ICU management. Drugs routinely used by the patient before surgery should be evaluated, to be or not reintroduced already in the immediate postoperative period 29,31.

A major initial concern is elderly patients’ volume status, which should be closely monitored. Patients are mostly hypervolemic. This hypervolemia may be real or relative (by decreased cardiac compliance with increased heart filling pressures). In the elderly, vascular compliance systems do not tolerate excessive volume loads, or there is chronic renal function decrease, leading to vascular volume overload. Organic fluids may leak promoting effusions.

There is also the risk for elderly patients to develop hydroelectrolytic disorders more frequently than younger patients, both by the presence of co-morbidities and by the use drugs. Diuretics and increased intra and postoperative volume supply favor ionic unbalances in the elderly if there is no close monitoring. Renal function worsening with decreased urine concentration capacity may lead to vasopressin and neurotransmitters regulation dysfunction, and endogen opioids changes which may play an important role in volume regulation 2,4,18,26,32.

Slow surgery recovery should be respected and caused by decreased anesthetic drugs excretion. Extubation should be very cautious, after checking consciousness, ventilation and hemodynamic stability and if complementary exams do not change the approach 3,4.

Complementary Exams

Complementary exams should follow the service request routine, observing some persisting changes in the elderly. Changes in normal care routine may lead to failure in requesting fundamental exams. However, depending on patient’s previous history, specific exams may be requested as needed 29.

Routine bedside exams are in general chest X-rays, postoperative electrocardiogram and echocardiography. These are very useful for the elderly because they bring important information such as heart and lung involvement, drains and Swan-Ganz catheter position, in addition to patient’s evolution since ICU arrival 26,31

Blood count red series in general presents hematocrit decrease, which may be minor or significant. In case of minor changes (hemoglobin up to 10 mg/dL), normalization may be expected within few weeks. Red cells recovery is slow in the elderly due to hematopoietic system involvement in response to stress and to decreased erythropoietin. Major hematocrit decrease will probably need external correction with red cells concentrate. Leucogram may also present normal leucopenia (by dilution) or leucocytosis due to immune CPB changes.

There is delayed return to normal immune system functions making patients prone to infections. Platelets level should be normal or decreased, but platelet function may be impaired. This analysis should be made associated with coagulogram, and coagulopathy, if present, should be corrected 3,29,33.

Minor variations as compared to normal hydroelectrolytic balance represent significant changes in normal homeostasis. So, electrolytes may be strictly maintained within normal ranges 32.

Blood gases analysis may show pH below normal with minor acidosis. In general, elderly patients have lung exchange disorders, as slightly lower PaO2 levels and mild PaCO2 increase, which should not impair tracheal extubation planning. Conversely, major changes should be controlled maintaining assisted ventilation and with more frequent blood gases analyses 23,26 

Cardiac injury enzymes markers are also important for the evaluation of postoperative evolution and acute myocardial infarction diagnosis in elderly patients. There is creatino-phosphokinase MB fraction release (CKMB) due to ischemia during CPB, as well as during aortic and myocardial incisions (e.g.: cava catheterization by right atrium). AMI diagnosis should not be done until CKMB levels are significantly increased (that is, higher than 30 units/liter). Troponin dosing is a recent test leading to early detection of acute myocardial infarction 35.

 

NEUROLOGICAL COMPLICATIONS

Neurological complications after cardiac surgery are more common in the elderly as compared to general population. Both cognitive (loss of recent memory, loss of concentration) and psychological (depression, increased dependency) changes are early detected after surgery. A positive supportive attitude from the medical team and family guidance help minimize these problems. In general, such disorders are resolved within 4 to 6 weeks, but unfortunately, there are cases of neuropsychological function deterioration within the following 6 months 3,12,21.

More severe neurological complications, such as stroke, are seen in approximately 10% of patients above 65 years of age and their risk factors include carotid atherosclerotic plaques, previous stroke or transient ischemic accident, prolonged CPB (more than 2 hours), and left ventricular mural thrombi previous to surgery. These severe acute or sub-acute presentations should be promptly controlled under neurological guidance and, in general, invasive monitoring such as intracranial pressure and jugular bulb should be installed to better control brain status evolution. Whenever possible, ICU physician should request routine brain CT scans to control and monitor evolution and possible intercurrences. If needed, follow up by MRI may bring additional information to CT scans 12.

In addition to vascular auto-regulation changes, there are also blood-brain barrier changes with age. Selective membrane quality is changed with major consequences for not blocking substances that may promote brain damage. Brain intoxication by noxious substances is a difficult diagnosis and may simulate clinical diseases, providing longer hospitalization time and inadequate treatment.

There might also occur postoperative upper limbs neuropathies. Since they are predominantly present in regions innervated by the ulnar nerve and medial cutaneous nerve of forearm, they suggest that injuries are caused by brachial plexus compression or traction. Mean symptoms duration is 2 months, but some patients have a slower recovery period which may last 6 to 12 months. Physical therapy is of great help to resolve such cases or, at least, to control the situation in patients with minor involvement 2,5.

Visual symptoms may be present due to retina embolism, occipital lobe infarction or optic ischemic neuropathy. Since ophthalmologic complications are also very common in the elderly, eye diseases should be ruled out 2,5.

 

PULMONARY COMPLICATIONS

It is difficult to establish the reason for postoperative respiratory function loss in the elderly. In addition to functional loss due to age, other preoperative factors may contribute for pulmonary function impairment, such as smoking, obstructive pulmonary diseases and environmental exposure to pollutants. Respiratory drive and respiratory muscles function are depressed in the postoperative period by the combination of drugs effects and chest wall derangement’s. Patients with preexisting pulmonary diseases may present major respiratory function depression needing thorough pulmonary toilet 4,23.

Major anatomic change in the elderly is decreased diameter of small airways, resulting in increased final airways resistance, regardless of any previous change, be it emphysema or bronchiolar injury. In addition, there are changes in alveolar sacs morphology which make them not so deep. These changes are result of decreased elastic fibers and increased collagen tissue, leading to the following physiological changes: decreased elastic retraction; increased pulmonary compliance; decreased oxygen diffusion capacity; early occlusion of small airways; increased oxygen alveolar-arterial gradient; and decreased expiratory flow 23.

There are also chest wall changes with decreased compliance due to kyphoscoliosis, intercostal cartilages calcification and costo-vertebral junction arthritis. This chest wall stiffening determines higher diaphragm and abdominal muscles effort during breathing. So, for successful extubation it is necessary to confirm diaphragm strength 23.

Almost all patients have a certain degree of alveolar dysfunction after open heart surgeries. This is due to left-right intrapulmonary shunt caused by several intrinsic alveolar abnormalities (atelectasis, edema, infection), and to vascular events in the lung (transudate, hypoxic vasoconstriction inhibition). High alveolo-arterial gradient is a severe problem needing thorough evaluation. The respirator should be checked and programmed to improve gases exchanges. Other intercurrences, such as pneumothorax, selective tracheal tube position, atelectasis, pneumonia and major pleural effusions should be ruled out 4,23.

A major concern of longer ICU stay is pulmonary thromboembolism, since elderly are a risk group. Diagnostic is difficult due to patients’ cardiopulmonary conditions. Low molecular weight heparin should be started early after surgery. When there is suspicion of thromboembolism, more effective diagnostic methods, such as helicoidal CT, D dimer, echocardiography and scintigraphy may help the diagnosis. Anticoagulation and thrombolysis should be considered 36.

 

CIRCULATORY COMPLICATIONS

Arrhythmias

Arrhythmias are very frequent in the elderly population. If present in the preoperative period, there are high chances of persisting in the postoperative period, but they may also start as from some event during surgery, such as metabolic disorders, intraoperative ischemia or conducting system injury 20.

In general, cardiac surgery postoperative period is followed by a hyperdynamic state, both by surgical stress and the use of b-adrenergic drugs at the end of CPB. This is also true for the elderly, with progressive heart rate decrease in response to stress, especially by decreased receptors response to adrenergic stimulation. Since there are structural heart changes, elderly patients are subject to supraventricular or ventricular tachycardia 20,37.

Management of supraventricular arrhythmias in the elderly is similar to young patients. When asymptomatic, management is expectant. If there is atrial fibrillation or flutter, situation should be reversed or tachycardia should be controlled 20.

As opposed to supraventricular tachycardias, ventricular tachycardias are associated to major increase in mortality, including sudden death. Therapeutic measures should be promptly established because periods of low cardiac output are not well tolerated by elderly patients and may promote neurological damage 37.

Acute Myocardial Infarction

Acute myocardial infarction (AMI) in the elderly after cardiac surgery is an event of high morbidity and mortality. Even in the postoperative period of myocardial revascularization to treat coronary failure, risk factors such as diabetes mellitus and hypertension may trigger ischemic events. Elderly patients, for having a higher degree of collateral circulation, would be less prone to develop ischemia. However, they are more frequently affected by triple arterial disease and surgical technique and individual evolution are major causes for postoperative ischemic events 3,24,35.

AMI diagnosis after cardiac surgery is more difficult than in other situations. Ischemic events may be present without precordial pain. This fact, common in the elderly, may be due to autonomic nervous system dysfunction, increased pain tolerance by sensitive neuropathy, increased amount of opioid receptors or increased sensitivity to endogenous or exogenous opioids. Other factors include decreased serotonin release, memory problems or senile dementia 13. ECG is the most immediate method for postoperative AMI diagnosis. ST/T segment / wave abnormalities and enzymatic increase are in general present in the postoperative period of any cardiac surgery.

Diagnosis should be carefully interpreted and then treated. ECG should be at least daily. New and persistent Q waves followed by new and persistent ST segment abnormalities are the most helpful criteria. Pathologic Q waves may appear earlier (that is, immediately after ICU arrival) in revascularized patients as compared to non-revascularized ones. CKMB should be measured in 8-hour intervals 35.

Troponin is a marker of cardiac injury. Both troponin I and troponin T are in general increased in all patients submitted to myocardial revascularization. Patients with postoperative AMI release large amounts of troponin and blood tests are 10 to 20 times higher than normal limits for a period of at least 4 to 5 postoperative days. It is also known that troponin I increase is higher that CKMB increase, even in patients in whom AMI diagnosis has not been confirmed by traditional criteria. This suggests that troponin may detect minor myocardial tissue injuries, which are not detected by CKMB 38.

Myocardial dysfunction complications, such as congestive heart failure and cardiogenic shock have severe repercussions in the elderly patient because adrenergic response may not correspond to organic needs. There is a high incidence of post-AMI death by heart rupture in elderly patients. So, some type of treatment should be instituted according to postoperative conditions. Such measures should be carefully installed, always aiming at therapeutic benefits for this type of patient 35.

Congestive Heart Failure

Age-induced physiological changes in the circulatory system may lead to congestive heart failure after cardiac surgery in the elderly. Increased connective tissue in medium and adventitia layers of large and medium arteries decreases vascular elasticity and increases impedance to left ventricular ejection. This change is responsible for systolic hypertension, which contributes for left ventricular hypertrophy and diastolic filling changes. Increased collagen in cardiac interstitium, compensatory myocitic hypertrophy in response to apoptosis, and calcium flow impairment during diastole may lead to age-related left diastolic failure. These changes increase left ventricle end diastolic pressure and left atrium size predisposing to atrial fibrillation in the elderly 3,19,39.

Other mechanism cooperating for congestive heart failure and not totally explained is decreased responsiveness of b-adrenergic receptors resulting in decreased heart rate and contractility (b1 effect) and peripheral vasodilation impairment (b2 effect); aging is also related to decreased mitochondrial ability to increase adenosine triphosphate (ATP) production when energy demand is increased 19.

An important data for therapeutic sequence is to determine whether congestive heart failure is systolic or diastolic, the latter very common in the elderly. Systolic heart failure is the difficulty of the heart to overcome aortic impedance, while diastolic heart failure is due to loss of elasticity and decreased cardiac relaxation during diastole. This diagnosis is critical for the treatment, for the use of drugs with inotropic function and systemic vasodilation or drugs improving diastolic function, respectively 19.

Management of heart failure in the elderly is complex if renal functional reserve is decreased. Volume control is critical to prevent major cardiac problems. However, important fluid restrictions may lead to decreased renal flow in a kidney not tolerating major organic changes 6,19.

Systemic vasodilation may be obtained with current drugs, but the return of the heart pump function will be fundamental for elderly patients’ diagnosis. Very often there will be the need for reoperation or even immediate heart transplant planning in more severe cases. Some centers have intra-aortic balloon (IAB). IAB is a device installed in the aorta and which mimics heart beats, increasing coronary flow and heart contraction strength. Depending on the degree of preoperative failure, some authors advocate the use of intraoperative IAB 19,39.

 

STATES OF LOW CARDIAC OUTPUT AND SHOCK

Postoperative complications in the ICU, such as organic dysfunction, sepsis, muscle catabolism and high mortality rates are common. In general, patients have in common major surgeries or peri or immediate postoperative hemodynamic instability.

Perioperative release of inflammatory response mediators and decreased oxygen metabolism lead to capillary fragility, to multiple organ failure and death. Since elderly patients metabolic demand is lower as compared to young adults, low cardiac output state may be prolonged, making difficult diagnosis and worsening prognosis. For this reason, hypovolemic or cardiogenic shocks tend to have a better resolution (if promptly diagnosed) as compared to sepsis, where decreased immune response may lead to the worsening of the situation 2,3.

Low cardiac output syndromes and shock states diagnosis (cardiogenic or septic pattern) are confirmed with Swan-Ganz catheter pressure measures, which should be integrated to echocardiogram results at bedside. In the elderly, hemodynamic results may be related to the coexistence of more than one disease (e.g.: bradycardia and hypovolemia), and correct data interpretation is useful for patients’ evaluation. Since blood constituents’ replacement by the body in the elderly is slow, it is critical to check hemoglobin levels for immediate replacement when needed. It is also important to check coagulation to prevent hemorrhages 2,26.

Shoemaker et al. 40 have studied hemodynamic and oxygen transportation data in acute circulatory failure and were able to show strong correlation between oxygen output magnitude and duration (in the intraoperative and immediate postoperative period), evolving to multiple organ failure and death. Survival of high-risk patients was associated to supranormal cardiac indices, oxygen demand and consumption. Mortality could be decreased in those patients if indices observed in survivors were used as therapeutic goal in the intraoperative and immediate postoperative period.

This concept, with some variations, has been used in other protocols applied to patients above 60 years of age. With such, it has been shown that the search for a therapy assuring maximum oxygen transportation may decrease mortality and the prevalence of complications. Lobo et al. 40 have shown in a study that high risk patients submitted to major surgeries and treated with oxygen transportation optimization during 24 postoperative hours had 68% decrease in mortality and prevalence of complications in 60 days. A lower trend to develop organic dysfunction has also been observed when therapeutic goals were met.

 

RENAL FAILURE

Glomerular function declines with age. Following is a formula developed by Cockcroft and Gault 18, to estimate creatinine clearance through serum creatinine concentration:

     (140-age) x weight (kg)
      72 x serum creatinine

For females, this value should be multiplied by 0.85. However, this formula has not been valid for very old patients.

Renal characteristic is modified with aging and there is the beginning of focal or segmental glomerulosclerosis diffusely increased in the mesangial matrix, in addition to basal glomerular and tubular membranes weakening. Proteinuria is unknown as cause or consequence of such structural injuries. There is renal mass decrease above 30% after the 8th decade. There is also 30% to 50% decrease in the number of glomeruli and the presence of sclerosis. Filtrating surface is decreased and replaced by mesangial cells which increase 12% in total glomerular volume 18.

There is cortical afferent arteriole obliteration with total atrophy of glomerulus. There is blood shunt between afferent and efferent arteries with blood redistribution favoring renal medulla. These anatomic changes bring the following functional changes: 50% renal blood flow and glomerular filtration rate decrease from 30 to 90 years of age; urinary concentration and sodium retention capacity decrease favoring dehydration; poor acids excretion with loss of ions exchange efficacy and decreased aldosterone secretion 18. However, data with healthy males of different ages have shown that mean serum creatinine concentration is relatively constant along the years because it reflects a balance between daily creatinine load to be excreted and glomerular filtration impairment related to age and estimated by creatinine clearance 23.

All patients undergoing cardiac surgery have renal blood flow and glomerular filtration rate (GFR) decreased both by anesthesia and the surgery itself (aortic clamping, CPB). Structural and functional changes predispose to acute renal failure (ARF) in elderly patients. In addition to advanced age, risk factors for persistent postoperative ARF include: history of renal dysfunction or left ventricular dysfunction; prolonged CPB (above 180 minutes); prolonged total aortic clamping; perioperative hypotension and other complications leading to renal perfusion decrease 8,27.

Urinary output is variable in patients with postoperative ARF. Anuria is uncommon and, if present, there should be suspicion of urinary tract obstruction (Foley’s catheter obstruction). Oliguric ARF (below 30 mL.h-1) is less frequent than non-oliguric, but reflects a more severe renal injury, being associated to high probability of dialysis in the acute phase. Renal blood flow decrease if severe and prolonged, may induce acute tubular necrosis. Hypotension during and after surgery, loss of postoperative fluids and arrhythmias are common in the elderly and induce ARF by hemodynamic disorders.

Possible additional factors contributing for this situation include: sepsis; nephrotoxic drugs; venous contrast administration; thrombotic or fatty emboli; increased free circulating hemoglobin levels by hemolysis during CPB and effects of angiotensin converting enzyme (ACE) inhibitors in capillary glomerular pressure (Chart II). The possibility of renal changes with acute interstitial nephritis, acute glomerulonephritis or renal vascular disease should be taken into consideration if there has been no severe hemodynamic disorder. Surgeries are responsible for one third of acute tubular necrosis in elderly patients. Acute tubular necrosis after cardiac surgery is associated to a poor prognosis 3,41.

Essential management of nitrogen increase of pre-renal cause and of acute tubular necrosis is to adjust cardiac output. Vigorous hydration before and during surgery guided by volume monitoring (to prevent pulmonary edema), may prevent ARF by dehydration. In addition to optimizing intravascular volume, inotropic drugs adjustment, when needed, is critical. Medical prescription should also be reviewed with withdrawal of diuretics and nephrotoxic agents (when possible) to change final therapeutic results. If there is oliguria for more than 12 hours, some support measures should be started, such as: hydroelectrolytic balance attention, preventing hyperkalemia and free water administration which may cause hyponatremia, and correction of acidosis. Attention to the presence of pericarditis, refractory hyperkalemia, uremic encephalopathy or colitis. Continuous hemofiltration is recommended to remove excesses. Other important factor is the nutritional status of the elderly patient and the treatment of postoperative infections. Sepsis and ARF are the worst challenges for intensive care patients 8.41.

 

INFECTION

Although unspecific, fever is an early clinical sign of postoperative infection. However, elderly patients do not develop fever as adult or young patients. In the elderly, complementary exams are needed to diagnose fever-free infections or to confirm that fever is due to infection. Other causes for fever are: reaction to CPB, atelectasis, phlebitis in catheter sites, reaction to drugs, pulmonary embolism and post-pericardiotomy syndrome 2,4 

The risk for severe infection in the elderly population increases due to several changes related to advanced age. There is a higher incidence of microaspirations making those patients more subject to pneumonia. Decreased natural barriers efficacy, such as skin, membranes and mucosa, allow for the spread of traumatic injuries or pressure ulcers. The presence of co-morbidities, such as diabetes, COPD and malnutrition, also predisposes to infection. Viral and fungal infections should always be investigated because the may be associated to poor prognosis. Infections, including bacteremia and sepsis, are major causes for increased postoperative morbidity and mortality in the elderly. This population presents the highest number of bacteremia, especially by gram-negative organisms 2,4.

 

HYPOTHYROIDISM

Hypothyroidism is relatively common in the elderly population but is poorly treated due to clinical diagnosis delay or difficulty, especially during ICU stay. Hypothyroidism (or hypoparathyroidism) may go unnoticed or even be masked by the simultaneous presence of heart, lung or nervous system changes not fully diagnosed.

These complex clinical symptoms may induce the ICU physician to disregard the presence of endocrine disease. The impact of non-endocrine diseases on endocrine physiology, at any age, may also mask the presence of endocrinopathy. Examples of non-endocrine diseases effects are: 3,5,3’-L-triiodoothyronine (T3) and thyrotrophic hormone (TSH) serum concentration decrease in both genders and testosterone serum levels decrease in males with some severe systemic disease, such as neoplasias or heart failure.

Thyroid dysfunction should be considered with the negative evolution of the case. Fatigue and tiredness are the most frequent symptoms but clinical characteristics of hypothyroidism may be sub-clinical, imperceptible or non-diagnosed, leading to severe sequelae 42.

In the elderly and in patients with multi-systemic diseases, care must be taken in interpreting endocrine function lab tests. Some unspecific lab tests for thyroid may reflect changes related to hypothyroidism. Blood count may show macrocytic anemia due both to pernicious anemia and slow erythrocyte maturation. Other tests show hyponatremia, hyperuricemia and increased CPK activity.

In general originated from skeletal muscles (isoenzyme), CPK when increased maintains high levels until beginning of thyroid hormone replacement therapy. MB fraction (CKMB) may be occasionally increased only by hypothyroidism, not meaning heart injury. So, it is desirable to always evaluate patient’s risk for developing ischemic injury. Hyponatremia is often the result of decreased renal free water clearance, resulting from excessive antidiuretic hormone release (ADH and vasopressin) of central origin. Thyroid hormone replacement normalizes sodium serum levels. Patients with more severe hypothyroidism may hypoventilate and present increased CO2 retention 42.

Metabolic balance may take up to two months to normalize with therapeutic thyroid hormone doses. So, a gradual regimen of doses is in general recommended. Even reaching decreased TSH serum levels, it may be necessary to adjust thyroid hormone replacement, as when there are symptoms suggesting hyperthyroidism which may develop months after seemingly stabilization of T4 dose. There is no rule for the use of T3 or the mixture T4/T3 to manage hypothyroidism in the elderly.

Some few patients have primary hypothyroidism and primary adrenocortical failure (Schmidt’s syndrome) and need chronic hormone replacement for both diseases. It is very uncommon for the elderly patient with hypothyroidism being treated with oral T4 to develop relative adrenocortical failure with hypotension and mild hyponatremia needing steroid replacement 42.

 

RESUSCITATION

This is a critical point in the discussion of the postoperative period of elderly patients since this adverse effect may be present and pose questions as to the amount of effort to be used to resuscitate such patients. Most studies show that elderly survivors do not show significant neurological damage or functional impairment and return to the state before cardio-respiratory arrest (CRA).

Tresch et al. 43 have shown that from the moment that the pre-CRA state is reestablished until hospital discharge, there are no differences between elderly and young patients as to the ability to perform activities. However, there are also studies showing exactly opposite results. For these studies, elderly patients would have major difficulty to return to the pre-CRA state, with major organic deterioration as compared to young patients 43.

So, it seems that age alone does not determine survival of patients receiving cardiopulmonary resuscitation (CPR) after CRA. CPR in elderly patients also seems not to be an unnecessary exercise for the medical team. Studies agree that the number of co-morbidities is the major determining factor for development and success of resuscitation maneuvers.

However, since most centers use a standardized care for resuscitation, very often the clinical situation before CRA is not taken into account, even due to the emergency of the situation. In the impossibility of individualizing the elderly patient, care may not be optimal and may prevent maximum efforts for those with higher survival possibilities 43.

 

CONCLUSIONS

Complications described are those of most concern for the ICU physician when there is an elderly patient in post-cardiac surgery period. This patient will need special care, even if the surgery is totally normal, because there is major surgical stress.

As to physiology, aging is followed by decline in all organic systems, which implies decreased organic response to aggression. There is also physical recovery delay and the elderly are submitted to a longer instability period as compared to young patients.

As to diseases, elderly patients suffer of chronic diseases impairing postoperative recovery if not well controlled. Uncontrolled diseases such as hypertension, diabetes mellitus, hypothyroidism and chronic pulmonary diseases (COPD), common in this population, prolong the postoperative period leading to global worsening of the individual. A frequent complaint of elderly patients in the ICU after cardiac surgery is weakness.

Poor nutrition plays an important role in the sensation of strength and fitness of the patient for surgery. Decreased food intake and chronic diseases may lead to weakness due to muscle mass decrease, leading to this sensation. In addition, poor nutrition also impairs immunocompetence increasing the possibility of chronic disease complications, predisposing the patient to indirect weakness causes such as sepsis and AMI. Difficulties to diagnose hypothyroidism, immobility, senile muscle loss and poor nutrition also lead to the sensation of weakness. Prolonged stay in bed increases the possibility for nosocomial infections and promotes delayed return to normal activities.

These aspects should be preoperatively investigated and treated to optimize postoperative evolution 6,7,15.

Cardiac surgery is a procedure with major organic repercussions promoting a critical postoperative status requiring intensive care to assure patient’s recovery 4.

There is agreement that strict preoperative control and efforts to assure intraoperative stability assure good postoperative evolution, even in slightly weaker patients. However, poor preoperative preparation and periods of intraoperative hemodynamic instability worsen the diagnosis, especially for the elderly, leading to severe postoperative complications. Elderly cardiac surgery results will be better if there are less co-morbidities. In the presence of postoperative changes, these should be identified and corrected as soon as possible to assure the success of the surgery. Efforts should be continuous to assure good cardiac surgery results.

Considerations should always be made to assure surgery improvements, aiming at decreasing CPB time and, as a consequence, associated multi-systemic organic injury with less embolization of the ascending aorta 29. Complications are frequent in elderly patients, but the medical team should be prepared to face this type of situation, individualizing the treatment and being more active in cases needing further attention.

 

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Correspondence to
Dr. Paulo de Oliveira Vasconcelos Filho
Rua Frei Caneca nº 485/152A
01307-001 São Paulo, Brazil
E-mail: paulovasco@litoral.com.br

Submitted for publication September 11, 2003
Accepted for publication January 8, 2004

 

 

* Received from Hospital Israelita Albert Einstein, São Paulo, SP