Preoperative Risk Assessment and Intraoperative Monitoring

, W. John Russell3 and Brendon J. Coventry 



(1)
Department of Anaesthesia, University of Adelaide, Adelaide, SA, Australia

(2)
Queen Elizabeth Hospital and Royal Adelaide Hospital, Adelaide, SA, Australia

(3)
Royal Adelaide Hospital, University of Adelaide, Adelaide, SA, Australia

(4)
Discipline of Surgery, Royal Adelaide Hospital, University of Adelaide, Adelaide, Australia

 



 

Brendon J. Coventry




Abstract

In emergency surgical settings, opportunities for optimization of the patient are usually limited due to the lack of time and often the hours during which surgery is required. However, in elective surgical settings, especially with higher-risk patients who have multiple comorbidities, preoperative evaluation and optimization are important considerations to reduce the risk of adverse events and to improve clinical outcomes. This chapter aims to provide information on perioperative assessment and intraoperative monitoring in an effort to reduce the rates of complications, risks, and consequences associated with surgery. For other associated procedures, refer to the relevant chapter or volume.



General Perspective and Overview


The optimization of the patient prior to surgery, where possible, provides the best opportunity for reduction of risks associated with anesthesia and surgery. Fit and young patients may have minimal need for preoperative intervention, but given that the median age of our populations in the western world are steadily increasing, the need for adequate assessment, preoperative medical optimization, and intraoperative monitoring will likely increase over coming years.

This chapter addresses preoperative medical assessment, anesthesia-specific concerns and intraoperative anesthetic monitoring systems, and the role of these aspects in optimization of the perioperative condition of the patient in the process of surgical risk reduction. It is intended as a guide and cannot embrace all of the aspects of this field.


Preoperative Assessment



Objectives


This chapter aims to give the reader understanding and some guidelines for appropriate preoperative assessment. This should lead to:



  • Early identification of patients at increased risk of perioperative complications


  • Optimization of medical problems prior to surgery


  • An ability to appropriately understand some main risks and benefits of undertaking a particular surgical procedure

It is important to recognize these are only a guide. Many preoperative assessment questions raised can be difficult to answer, and sometimes there may be no good answer, just a decision as to which outcome carries the least risk and the best likely outcome for the patient in question. If there is any doubt, help should be sought from a colleague from within the same or other appropriate specialist field.


Introduction


The main principle of preoperative assessment is to detect likely difficulties and problems with the patient’s condition that might be correctable, which could improve the type or safety of the anesthetic procedure and surgery selected and used.

The main imperatives are to:



  • Establish whether the condition of the patient is subject to time constraints or not – is the operation urgent?


  • Detect any likely difficulties or problems with anesthesia


  • Determine the reversibility of any condition detected

For example, in situations like bowel obstruction from carcinoma, or in advanced cardiac compromise, one may be required to accept some compromises in the optimization of the patient for urgent surgery; otherwise there is usually time to prepare and correct medical problems before surgery. This would depend also on the reversibility of the condition(s).

“Is there something that we could improve in order to prepare the patient for anesthesia and surgery?”




  • Preoperative consultation


  • Time constraint vs. non-time constraint


  • Correctable vs. non-correctable


  • How appropriate is the proposed anesthetic for the patient?

The timing of anesthesia may be modified to allow correction of medical or other problems, and this alone may improve the overall safety of the procedure and reduce or limit some of the intraoperative or postoperative complications that may be experienced.

Fixed problems may not be influenced by the timing of anesthesia, for example, mandibular restriction or a difficult airway. However, being aware of a potential problem may permit better planning to improve safety. Alternative anesthesia techniques might avoid a particular problem; for example, in obstetrics, regional (spinal or epidural) anesthesia might offer a safer alternative and reduce the risk of aspiration pneumonitis associated with general anesthesia (GA).


The Who, When, and How of Preoperative Assessment


The who, when, and how of preoperative assessment are somewhat dictated by the resources, anesthetic type, patient type and load, logistics, and needs of the institution.


Who


Ideally, preoperative assessment should be performed in every individual having an anesthetic procedure of any type. Clearly, in the young, superbly fit individual and perhaps for very minor procedures, the process is simple and straightforward. However, even in these situations, some unexpected surprises may be encountered. Examples are as follows: the young person previously well, with development of a drug allergy, family history unknown to them (parents may recall information of use), or for the elderly person who is undergoing a minor cutaneous excision who refluxes and subsequently aspirates.

Practicality often dictates that many patients are selected to be seen, if they are scheduled to have a GA, have a regional anesthetic, have a known problem, or are over 40 years of age. Many institutions have a “blanket rule” that every patient is seen for preanesthetic assessment if they are scheduled for surgery of any type, and this is clearly a safe policy but considerably time and cost intensive.


When


In the elective setting, the timing of the initial preanesthetic visit is highly dependent on the condition of the patient and on the type of surgery that is being planned. Patients who are elderly and/or have significant cardiorespiratory or other serious medical problems should ideally be assessed about 3 months prior to planned surgery to enable proper assessment and possible correction/optimization of any identifiable correctable problems. An example is surgery for elective hip replacement, which might also permit iron supplementation prior to surgery to reduce transfusion risk. A good indication of the needs of a patient for preoperative management can be gained through a telephone interview with the patient, as soon as the patient is placed on an operating list.

For semi-elective or semi-urgent settings, the time line is compressed to dictate preoperative assessment at 1–3 weeks prior to surgery but usually enables reasonable investigation and optimization of the patient’s condition and planning for any potential difficulties that might be encountered with the anesthetic.

In the urgent setting, time is of the essence and this dictates a rapid assessment of the patient’s condition. A number of compromises may be made in optimizing the patient’s condition while enabling the procedure to go ahead. Even in this setting, it is often possible to quietly, systematically assess the patient’s condition and even delay surgery slightly to correct problems, for example, to rehydrate the patient properly, stabilize their condition, organize adequate staffing, and plan monitoring that may be useful during surgery.


How


Most institutions and anesthetic practices have a preoperative assessment process which is used to evaluate patients. This may be in the form of a specific “preanesthetic clinic” designed for review of the patient prior to anesthesia and surgery. The timing of the clinic appointment is usually 1–4 weeks prior to the booked date of surgery, but this will depend on patient and institutional factors. For fit, young patients undergoing minor surgery, the process is relatively routine and uncomplicated and only one appointment is usually required. For elderly or complex patients, the earlier the initial appointment prior to surgery, the better the chance of optimization of the patient’s condition, and more clinic reviews may be needed to ensure this. Recent review by the patient’s usual physician can usually be expected to improve the patient’s clinical state, especially for familiar chronic medical problems. Ideally, the anesthetist that will be performing the patient’s anesthetic should do the preoperative assessment; in reality however, frequently logistical considerations often make this difficult to achieve. Good communication and a standard system of evaluation can usually overcome most problems that might otherwise be encountered when different anesthetists perform the preoperative assessment and anesthetic.

In some cases, it may be appropriate to obtain specialized advice from a perioperative physician, a cardiologist, a respiratory physician, or other subspecialist to help optimize patient’s care prior to a planned procedure. It is better to ask for help early than to be criticized after for not seeking it.


Definition of Risk


Risk is determined by four factors:

1.

Patient-related risk

 

2.

Surgical-related risk

 

3.

Anesthetic-related risk

 

4.

Institutional risk

 

Any surgery, even in a healthy individual, carries a risk of an adverse outcome, including death. The risk associated with a surgical procedure is the relative chance of an adverse outcome as a result of that surgery in a particular patient.

Adverse outcomes are difficult to define exhaustively. An adverse outcome may be as extreme as death from pulmonary embolism or the need for a previously fit and healthy individual to require full-time nursing care for irreversible hypoxic brain damage from a respiratory arrest. A lesser adverse outcome may be an extra day in hospital after a slight chest or urinary infection.

Good preoperative assessment also involves good communication regarding adverse outcomes with the patient. It is also important to identify any issues that the patient may see as an unacceptable adverse outcome and address these.

Accurate preoperative assessment can help determine the individual risk of adverse perioperative outcomes and should identify those patients in whom appropriate intervention may reduce the risk of such outcomes. It is important to assess the potential benefit of the contemplated surgery and weigh this against the potential associated surgical risk. The final decision to proceed to operation in patients with high risk of perioperative morbidity and mortality should be multidisciplinary. The patient, the surgeon, the anesthetist, and other members of the healthcare team may have to reach consensus that the potential benefits of surgery outweigh the potential associated risks.

Examples include the decision to proceed with non-lifesaving joint replacement in an elderly man with multiple medical comorbidities who has such severe, constant pain that his quality of life is so diminished that he is happy to accept a risk of death and disability to have a surgical cure for his pain. An opposite example would be not to proceed with nephrectomy in an asymptomatic woman with renal malignancy who is at high risk of perioperative morbidity and mortality because of medical comorbidities that are associated with a worse prognosis than the underlying malignancy.

These decisions can be very difficult. Where possible, it is important to seek expert help if there are questions of importance that involve individual organ systems to help decide on the timing of surgery and the appropriate preoperative optimization.

The risk of surgery encompasses many organ systems which may develop dysfunction, either individually or as part of multisystem organ failure.

“The final decision to proceed to operation in patients with high-risk of perioperative morbidity and mortality should be multidisciplinary. The patient, the surgeon, the anesthetist, and other members of the healthcare team may have to reach consensus that the potential benefits of surgery outweigh the potential associated risks.”


Communication


A vital element in any encounter between a health professional and a patient or their relatives is the ability to communicate. It is also true for communication between professionals.

An effective preoperative assessment involves many levels of communication. At the least, information that determines perioperative risk needs to be gathered, leading to decision-making. That decision then needs to be clear to the patient, healthcare team members, and any other relevant parties. Without effective communication the information gathered may be insufficient to accurately determine risk, or the decision may be poorly communicated to other members of the healthcare team. Either mistake may lead to an increased risk of an adverse outcome, rather than the desired decrease.

Without good communication, any effort put into appropriate preoperative assessment is likely to be wasted or less effective. The ability to communicate effectively is something that many people have learned over a lifetime. There are basic principles, however, that can be learned. A short summary on communication here should help emphasize the importance placed on this skill. It is beyond the scope of this chapter, however, to exhaustively outline the many communication skills that need to be mastered.

Preoperative assessment can involve clear lines of communication between many parties. The assessor may need to communicate with:



  • The patient


  • The patient’s family and/or carers


  • The surgeon(s)


  • The anesthetist(s) (and perhaps ICU staff)


  • Other appropriate health professionals, e.g., dietician, GP, physiotherapy, nurses

Communication objectives may range from ensuring patients are aware of the risk implicit with minor surgery, but understanding that there are no major problems likely to be encountered, to discussing the risk-benefit ratio of surgery in a terminally ill patient facing a palliative, but life-threatening, procedure.

Important facets of communication include:



  • Transfer of appropriate information


  • Transfer of information in a timely fashion


  • Transfer of information in an appropriate way

Good communication, like good preoperative optimization, involves good preparation.

The first step is to define what needs to be communicated (the objective). This is the most important step and, if not defined prior to the communication, may make the conversation less effective. The manner of communication is next, as it is difficult in many settings to avoid being too technical, complex, detailed, simplistic, judgmental, patriarchal, matriarchal, patronizing, or any of the many other errors that may be made or may be perceived to be made. It is important to make the effort, however.

The correct environment, such as seeking a quiet place without interruption, e.g., from mobile phones, people, clatter, or nursing staff, is often important.

It is appropriate to also have an understanding of educational background of the person you are communicating with. For example, in discussion of the Delorme’s procedure with a surgeon, a nonmedical person, or someone who is unfamiliar with the procedure, each will need a different approach.

“Good communication, like good preoperative optimization, involves good preparation.”

It is important that communication occurs in a language and cultural context that is appropriate. This may involve the use of an interpreter. Although the family may offer to interpret, it is preferable to have a trained interpreter who should be trusted to transfer information without editing the information being relayed.

Cultural sensitivity is important. It may not be appropriate to discuss gynecological procedures with a Cambodian or Middle Eastern lady with a male interpreter or doctor. There are many other examples of where cultural misunderstanding can interfere with the ability to provide good quality healthcare. If communication is written rather than spoken, it is important to ensure information is sent within a time frame, to permit adequate reading time and comprehension.

The third step is to allow time for interactive questions and clarification. Communication should be a two-way process, to facilitate questions and understanding and detect any uncertainty or unwillingness of consent.

The final step is to ensure that all parties have understood the objective you wished to achieve. Briefly summarizing the outcomes and asking the patient to describe what they understand is a useful way to confirm this before the encounter finishes.


Assessing Risk of Different Types of Surgery


The first part of risk assessment is identifying high-risk surgery. It seems self-evident that an individual undergoing a major vascular procedure with a prolonged anesthetic time, major blood loss and fluid shifts, and increased cardiopulmonary stresses will have a greater risk of adverse events than the same individual undergoing cataract surgery.

The first question to answer then is what level of risk does the proposed surgical procedure carry?


Assessing Urgency of Surgery


In the emergency situation, there may be little opportunity to assess the patient preoperatively to improve postoperative outcomes. Once the type of surgery has been specified, the time line in which it is to be performed must be determined.

A critically ill patient needing immediate lifesaving surgery should not have their procedure delayed for tests which are unlikely to change the management. Appropriate preoperative assessment in this instance, however, includes recognition of the severity of existing illnesses, urgent preanesthetic optimization of the patient’s condition, and commencement of some postoperative planning such as the need for ICU admission. Sometimes, a short period of resuscitation is wise.

A patient awaiting surgery that is not life-threatening, such as elective joint replacement surgery, should have their surgery delayed when an increased risk of an adverse perioperative outcome is recognized, so that they may be improved by preoperative optimization.

The second question that needs to be asked is how urgent is the planned procedure?



  • Emergency (e.g., ruptured viscus)


  • Semi-elective surgery (e.g., non-obstructed bowel carcinoma)


  • Elective surgery (e.g., hip replacement)


Assessing Cardiac Risk






  • History


  • Examination


  • Investigation

The commonest severe adverse events after surgery are cardiac and include cardiac death, cardiac ischemia, and cardiac failure. These account for a significant burden of serious nonfatal adverse outcomes with surgery in the short term but are also markers for increased long-term mortality and morbidity.

There are many scales for assessing adverse cardiac outcomes following surgery. The simplest but highly reliable scale is the Revised Cardiac Risk Index proposed by Lee.

This involves assessing six individual risk factors. The risk of an adverse perioperative cardiac event is directly related to the number of risk factors present, regardless of when they occurred prior to the contemplated intervention:



  • High-risk surgery


  • Previous myocardial infarction


  • Previous cardiac failure


  • Previous cerebrovascular accident


  • Diabetes on insulin


  • Renal failure (creatinine >170)

The Gupta cardiac risk assessment tool is also validated and reliable. It is available online, which improves its utility (Arora et al. 2009a, b; Gupta et al. 2011) (​www.​qxmd.​com/​calculate-online/​cardiology/​gupta-perioperative-cardiac-risk).

The Detsky Revised Cardiac Risk Index is older and more complex but also a useful tool in preoperative cardiac risk assessment. There are also international guidelines to help determine the degree of risk involved in an individual having a surgical procedure, which also outline suggested preoperative cardiac investigations. (Detsky et al. (1986); Lee et al. (1999); Fleisher et al. (2007)).

Important questions to ask in association with identifying the above risk factors are:



  • Presence or absence of potentially cardiac ischemic chest pain


  • Exercise tolerance (no angina in a wheelchair-bound person is not reassuring)


  • Symptoms of left ventricular failure (orthopnea, paroxysmal nocturnal dyspnea)


  • Symptoms of right heart failure (ankle edema)

The role of examination in cardiac preoperative assessment is important in excluding severe valvular lesions. The most important of these is aortic stenosis, which, if severe, is associated with a greatly increased risk of adverse cardiac events. It is the most common valvular lesion in the elderly, and the incidence of severe aortic stenosis is estimated to be around 4 % in those over 85.

Aortic sclerosis and stenosis are common in the elderly and are associated with an increase of approximately 50 % in the risk of death from cardiovascular causes and the risk of myocardial infarction, even in the absence of hemodynamically significant obstruction of the left ventricular outflow (Otto et al. 1999).


Cardiac Investigation (ACC Guidelines 2007)


Electrocardiography is appropriate to perform in:



  • All patients with a history of cardiac disease


  • All patients with a suspected arrhythmia (history or examination)


  • All patients over 50 having intermediate- or high-risk surgery

Echocardiography is appropriate to perform in patients with a history suggestive of left ventricular dysfunction (orthopnea, nocturnal dyspnea, dyspnea on exertion; see NYHA score later in this chapter). Echocardiography is also important in patients with a murmur felt to be of hemodynamic importance, especially in the case where significant aortic stenosis is suspected. Echocardiography should not be used routinely as it has low predictive value for perioperative outcomes.


Functional Testing for Ischemia


Functional testing for ischemia involves stress ECG, stress echocardiography, and stress nuclear isotope scanning. The stress may either be physical, such as treadmill exertion, or pharmacological, such as dobutamine or dipyridamole.

Stress ECG is not recommended in perioperative work-up as routine, although there may be reason to perform this if the patient is complaining of ischemic-sounding chest pain. Stress echo and stress nuclear scanning have a similarly strong negative predictive value and a weak positive predictive value, and most validation has occurred only in vascular surgery in patients with multiple cardiac risk factors. In the perioperative period these should be reserved for appropriate investigation of cardiac symptoms, irrespective of the need for surgery. They should be used routinely only in patients having major vascular surgery with significant risk factors (see ACC Guidelines 2007 for further information).


Assessing Pulmonary Risk






  • History


  • Examination


  • Investigation

There are less reliable scales for assessing adverse pulmonary outcome with surgery than there are for assessing cardiac risk.

One of the more accurate despite its simplicity is the ASA (see later in the chapter).

Other important pulmonary risk factors to take into consideration include:



  • Smoking history


  • Known respiratory failure


  • Obstructive sleep apnea


  • Abdominal surgery (the closer to the diaphragm, the greater the risk)


  • Length of surgery (the longer the operation, the greater the risk)


  • Morbid obesity

A functional assessment of exercise tolerance is important in assessing respiratory reserve. If exercise tolerance is limited to being unable to walk two blocks or climb two flights of stairs, the risk of perioperative pulmonary complications is significantly increased.

The Epworth scale is an assessment of daytime sleepiness and is an easy assessment tool for the likelihood of obstructive sleep apnea being present. It scores sleepiness in eight settings. The scores are:


















No chance of dozing

0

Slight chance of dozing

1

Moderate chance of dozing

2

High chance of dozing

3

The settings asked about include:



  • Sitting and reading


  • Watching TV


  • Sitting inactive in a public place


  • As a passenger in a car for an hour without a break


  • Lying down to rest in the afternoon when circumstances permit


  • Sitting and talking to someone


  • Sitting quietly after a lunch without alcohol


  • In a car, while stopped for a few minutes in traffic

The total is added up. A score greater than 8 may indicate need for further assessment for obstructive sleep apnea.

Examination is important to detect potentially reversible problems prior to surgery. Some important features to examine for include:



  • Nicotine staining of the fingernails suggesting active smoking


  • Bronchospasm


  • Pleural effusions (may relate to underlying cardiac dysfunction as well as pulmonary disease)


  • Previous pulmonary surgery, e.g., lobectomy for TB in 1953

There is little evidence to support the routine use of pulmonary function testing, although it may be useful in particular individuals, e.g., severe asthma to guide adequacy of bronchodilator therapy. Patients with respiratory difficulty at rest or with minimal exercise are however of obvious concern, and the difficulty should be investigated, where possible, using spirometry to assess any reversible airway obstruction. Pulmonary function testing may also be useful in people with known lung disease to determine their ability to survive general anesthesia. If the FEV1 is less than 1 L, then the probability of prolonged postoperative ventilation is increased, thus increasing the probability of perioperative morbidity and mortality.

Arterial blood gases may be useful in some circumstances, where shortness of breath at rest or with minimal exercise, known lung disease, or cyanosis is present.

Patients with a PaO2 in air of <70 mmHg must be considered for ventilatory support on high inspired oxygen concentrations. However, if their PaCO2 is >45 mmHg, the patient should be considered for operation very carefully because when further respiratory depression from narcotic analgesics occurs, the PaCO2 with likely rise to above 50 mmHg, and these patients may experience considerable hypercapnia.

CXR A history of a recent respiratory illness, a recent fall or rib fracture, fever, or known pneumonia will need to be investigated further with a CXR in addition to the clinical examination.


Assessing Exercise Tolerance






  • History


  • Examination


  • Investigation

It seems self-evident that significant medical disease will limit exercise tolerance. Many measurements of function, such as New York Heart Association classification of heart failure, depend on assessment of limitation of functional tolerance.

Exercise capacity also correlates well with VO2 max.

Exercise capacity has been shown to be predictive of outcome in thoracic surgery. Poor performance on assessment of self-reported exercise tolerance has also been shown to be associated with increased risk of surgical complications.

A useful self-reported measure is the ability to climb stairs. People able to climb less than two flights of stairs without stopping are at increased risk of perioperative cardiopulmonary morbidity and mortality. People able to climb five flights of stairs without stopping are at a very low risk indeed of perioperative morbidity and mortality (Reilly et al. 1999).

Examination and investigation may include a 6-min walk test or a trial of symptom-limited stair climbing. Stress testing with a well-defined protocol (e.g., Bruce protocol) on a treadmill is a more formal objective measurement of exercise capacity.


Venous Thromboembolism






  • History


  • Examination


  • Investigation

The development of deep venous thrombosis (DVT) and its more severe sequelae of pulmonary embolism (PE) is well recognized to be a complication occurring in the postoperative setting.

Risk for DVT/PE should be recognized in the preoperative setting, and a plan should be made for intraoperative and postoperative thromboprophylaxis.

Risk factors for DVT/PE include



  • The type of surgery (e.g., hip and knee surgery, pelvic surgery)


  • Past history of DVT/PE or known thrombophilia


  • Obesity


  • Malignancy, especially pelvic malignancy


  • Prolonged hospitalization and immobility

Examination has a limited role in predicting thromboembolism risk. Investigation has a limited role in the preoperative setting, unless there is clinical evidence of DVT/PE acutely or in the recent past. If there has been an event in the recent past, baseline investigation may prove worthwhile, e.g., venous leg ultrasound to see extent of preexisting clot. Many hospitals have well-developed protocols for perioperative thromboprophylaxis, and there are well-established international guidelines for most types of surgery (Hirsh 2004; NHMRC Guidelines 2009). In some settings (e.g., hip and pelvic malignancy surgery), the indication for thromboprophylaxis extends beyond the hospital period for up to 35 days after surgery.


Delirium






  • History


  • Examination


  • Investigation

Postoperative delirium is an increasing problem in an ageing society. Delirium is associated with increased length of hospital stay and increased risk of cardiac and pulmonary morbidity and mortality.

Risk factors for delirium include:



  • A history of cognitive deficit


  • Previous delirium


  • Major surgery (especially aortic aneurysm repair)


  • Polypharmacy


  • Increasing age

Examination and investigation should include an assessment of a person’s cognitive ability. This may be as brief as orientation to time, place, and person and ability to answer questions in an appropriate chronological fashion. It may be more formalized and, for instance, include a “mini-mental” examination if there is significant concern regarding cognitive function.


Rehabilitation






  • History


  • Examination


  • Investigation

One of the saddest outcomes, especially after elective surgery, is for a previously independent (elderly) person to be so deconditioned by a complicated hospital stay that they are unable to return to independent living and need to seek higher-level nursing home care. Especially in the elderly, fitness and muscle strength deteriorate quickly. Every day in the hospital reduces the ability to mobilize and perform activities of daily living without help. Perioperative complications increase hospital stay and are thus associated with increased risk of needing higher-level care. This risk is especially high in people who already have poor exercise capacity from their underlying problems. The problems may be the reason they have sought a surgical cure, e.g., limited mobility related to severe hip arthritis, or may relate to poor cardiopulmonary fitness. It is important to document a person’s exercise capacity prior to surgery and, if poor, recognize the need for increased rehabilitation or support early in the hospital stay to allow appropriate, timely, discharge planning.

Examination and investigation may include a formal assessment of exercise tolerance such as a 6-min exercise test of symptom-limited stair climbing. The Duke’s activity scale may also be useful as a measure of metabolic capability. The ASA also takes into account functional capacity and although simple is reliable in predicting poor outcome.


Renal Disease






  • History


  • Examination


  • Investigation

It is well recognized that the greater the reduction of renal function, the higher the risk of perioperative adverse outcomes. These adverse outcomes include renal dysfunction or progression to end-stage renal failure but also severe cardiac complications and death. It is therefore important to bear in mind that abnormal renal function is a strong clinical marker of increased perioperative risks. A history of renal dysfunction is important. Equally important is a history of vascular risk factors (hypertension, diabetes, smoking, hyperlipidemia, previous vascular disease) which may predispose to renal dysfunction and an increased risk of vascular disease. Many people, especially the elderly, may have unrecognized significantly reduced renal function detected in the preoperative assessment. A history excluding renal disease is therefore often inadequate without reassuring biochemical proof. Examination should include looking for A-V fistulae as dialysis access points.

Investigation should include the serum creatinine, which directly correlates with muscle mass. It is important to remember a normal serum creatinine may be associated with significant renal dysfunction in the frail elderly patient. A better marker of renal dysfunction is the glomerular filtration rate, which is calculated knowing the serum creatinine. There are many simple calculators for this, available online through www.​kidney.​org.​au.


Surgery in the Elderly


The risk of surgery in elderly patients varies from mildly to greatly increased, determined largely by the underlying fitness of the individual patient, principally related to the existing comorbidities, in addition to the severity of the surgical problem for which surgery is being contemplated. Many elderly patients tolerate anesthesia and surgery well, with little difference from younger patients. Low body-weight and frail people, with cardiac, pulmonary, renal, hepatic, or hematological illness(es), are subjected to increased risk of surgical and other complications. Tissue strength and repair is frequently reduced with advancing age, as is agility and readiness to mobilize after surgery and bed rest. Hepatic and renal impairment is common, which may alter drug metabolism and the required doses for anesthetic and other agents. Confusion and delirium are relatively more common also with advancing age. The need for postoperative prolonged rehabilitation or need for higher-level care may also be important to recognize. The main impact of surgery and postoperative complications is on existing multiorgan dysfunction, which may be appreciable, but sometimes previously unrecognized before the preoperative assessment for surgery. Tolerances to therapeutic manipulations are also frequently reduced in elderly patients with reduced capacity to respond to fluid loads, iatrogenic, or otherwise due to cardiac, renal, and pulmonary disease.


Interventions to Reduce Postsurgical Risk



Cardiac


Optimization of ischemia in an elective setting.


Beta-Blockade


Beta-blockers are not the panacea for all perioperative cardiac events; it was hoped they would be in recent times. Beta-blockers should be used in certain settings such as post-myocardial infarction and heart failure. They have a role in the treatment of angina and hypertension. They should certainly not be stopped in the perioperative period, as there is a risk of rebound cardiac ischemia and a worsening of perioperative outcomes. They should be introduced in patients having major vascular surgery (aortic or infra-inguinal repair), but only if they have evidence of ischemia on functional testing prior to surgery and do not meet ACC guidelines for cardiac intervention or need surgery before these guidelines can be met.


Statin Therapy


Statins have a major role in maintenance of vascular health and prevention of cardiovascular and cerebrovascular disease. There is some evidence that preoperative therapy with statins may reduce cardiovascular adverse outcomes in vascular surgical patients. It seems appropriate to consider the use of statins for secondary prevention prior to surgery if they are not already being used. It is appropriate to uptitrate the dose to meet recommended guidelines prior to surgery. It may be appropriate to initiate statin therapy in patients having arterial vascular surgery.


Other Medical Therapies for Cardiac Ischemia


Other therapies for ischemia such as nitrates and calcium channel blockers should not be stopped prior to surgery. Medical treatment of angina should be optimized prior to surgery to eliminate clinical evidence of ischemia (chest pain or dyspnea).


Coronary Revascularization


If there is ongoing clinical evidence of ischemia, it may be appropriate to consider coronary revascularization before surgery, but the ability to delay surgery to allow for coronary revascularization must be taken into account.

It is inappropriate to routinely revascularize all patients prior to surgery, but it is appropriate to consider them for revascularization if they meet recommendations for revascularization irrespective of their underlying surgical needs.

It is important to communicate the need for surgery to the cardiologist performing any coronary intervention. For example, it would obviously be undesirable to insert a drug-eluting cardiac stent in a patient with a potentially curable malignancy, as this may involve delaying surgery for up to 12 months.

There are four potential forms of revascularization, and they will be addressed in terms of planning for elective surgery and need for antiplatelet therapy.

Single antiplatelet therapy usually involves aspirin alone but may be clopidogrel alone. Dual antiplatelet therapy may be a combination of aspirin and Asasantin (in secondary prevention of cerebrovascular disease) or aspirin and clopidogrel (in secondary prevention of cardiovascular disease).


Coronary Artery Vein Graft


Patients can proceed to their elective surgery, when fit after CAVG. This usually is 6–12 weeks after cardiac surgery. Aspirin should be continued throughout the perioperative period where possible.


Balloon Angioplasty Without Stenting


This may be an appropriate intervention in a patient requiring urgent noncardiac surgery with significant active cardiac ischemia. It must be used in conjunction with maximal medical therapy. It has poorer long-term cardiac outcome than stenting, and it is important to recognize the possible need for further cardiac assessment postoperatively. Surgery can proceed on aspirin, although a 4-week delay would be preferable to allow healing of the cardiac endothelium. If surgery can be delayed for that period of time, bare-metal stenting may be appropriate.


Bare-Metal Stenting


Dual antiplatelet therapy with aspirin and (usually) clopidogrel is required for 4–6 weeks after bare-metal stenting to allow time for the bare-metal components of the stent to be covered in the endothelium. Before this, if the dual antiplatelet therapy is interrupted, the risk of intra-stent thrombosis and myocardial infarction is high. After this, it is appropriate to proceed with surgery but aspirin should be continued, if possible.


Drug-Eluting Cardiac Stents


Drug-eluting stents can be thought of as producing an endothelial toxin that prevents neointimal hyperplasia, which is a cause of failure of bare-metal stents. Because of the endothelial toxin, they also cause ongoing exposure of the metal component of the stent to blood elements. This increases the risk of late in-stent thrombosis with an associated mortality. The risk of this is much greater if the dual antiplatelet therapy is interrupted and possibly continues for many months after stent implantation. It is important NOT to interrupt dual therapy for at least 6 months after stent insertion. During this time, it is suggested only urgent surgery be performed, as the risk of bleeding on dual antiplatelet therapy can be substantial. After this, it seems prudent that surgery should proceed without interruption of single antiplatelet therapy (usually aspirin alone).


Optimization of Heart Failure


If time allows, it is appropriate to try and follow important principles prior to surgery.

These include the following:

1.

Ensuring patient is euvolemic, with diuresis as tolerated.

 

2.

Ensuring appropriate medical therapy for cardiac failure.

ACE inhibition and beta-blockade as tolerated should be considered in all, being aware of drug contraindications, side effects, and interactions. Introduction or dose titration should occur as soon as possible prior to the contemplated surgery.

Digoxin, nitrates, spironolactone, or other vasodilators may be considered if there is significant functional limitation.

 

3.

Ensuring appropriate postoperative surveillance such as an intensive care bed for fluid monitoring postoperatively.

 

4.

Appropriate monitoring is needed throughout the perioperative period, e.g., checking potassium levels when spironolactone is used, or checking digoxin levels, especially if there is any degree of renal impairment.

 

5.

There is some evidence that BNP or NTproBNP (basic natriuretic peptide or the N-terminal fragment of BNP) testing before surgery may help predict postoperative cardiac complications.

 

In the setting of emergency surgery, the most important principles are to obtain accurate historical and examination findings, communicate these to the anesthetic and surgical teams, obtain medical input as soon as possible, and ensure adequate, appropriate postoperative monitoring.


Treatment of Severe Aortic Stenosis


The key factor in reducing perioperative death or disaster with aortic stenosis lies in preoperative recognition of its existence. Adverse outcomes are much more common when severe aortic stenosis presents with fulminant cardiac failure postoperatively.

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Apr 9, 2017 | Posted by in GENERAL SURGERY | Comments Off on Preoperative Risk Assessment and Intraoperative Monitoring
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