Introduction

Patients, who are undergoing neurosurgical procedures, may be at risk of developing cardiac problems, intraoperatively as well as during the recovery period. Many of the intracranial lesions due to their related pathophysiological changes can lead to significant perturbations of the cardiovascular status in patients with associated cardiac disease. These problems can occur due to central neurogenic effects on the myocardium and autonomic nervous system or associated cardiac disease preoperatively. Neurosurgical patients with cardiac diseases like coronary artery disease (CAD), valvular heart disease, or congenital heart disease (CHD) may pose additional concerns in the operation theater as well as the intensive care unit (ICU), and thus a good knowledge of the pathophysiological changes associated with these cardiac lesions is required. Perioperative myocardial infarction (MI), arrhythmias, and pulmonary edema are commonly seen complications in patients with associated cardiac disease. Following noncardiac surgery, cardiac complications account for 25–50% of deaths.

Preoperative Evaluation

There is a general agreement that the neurosurgical patients with preoperative cardiac disease have a high risk of morbidity and mortality in the postoperative period also, therefore preoperative cardiac disease should be identified weather it is symptomatic or nonsymptomatic. A patient who comes for intracranial or spine surgery requires the same thorough preoperative cardiac evaluation as any person who will receive an anesthetic. A relevant history may be difficult to get from patients whose neurological status has declined, therefore prior medical records and family members can be helpful in this regard. This evaluation gives an idea about the patient’s current medical status and recommendation regarding management and what is the risk of cardiac problems during the perioperative period. These patients commonly present with blood pressure (BP) fluctuations, electrocardiographic abnormalities, and myocardial ischemia and failure.

Risk Stratification

The American College of Cardiology (ACC) and American Heart Association (AHA) in 1996 published guidelines on preoperative assessment of cardiac patients undergoing noncardiac surgery; these guidelines were latter updated in 2002 and then revised extensively in 2007.

The current review proceeds through the following sequence of five steps.

Step 1 of the assessment is to see if there is a clinical need for emergency noncardiac surgery. If it is urgent then the patient will go directly for the surgery, for example, an acute subdural hematoma with papilledema.

Step 2 is to look for any active cardiac conditions. The ACC/AHA 2007 guidelines have recommended (class I, Level B) certain active cardiac conditions for which patients require evaluation and treatment before undergoing noncardiac surgery. These are as follows:

• 1.
  

  Unstable coronary syndromes, which include unstable or severe angina pectoris or recent MI (within previous 30 days). Rate of mortality or perioperative MI is as high as 28% in patients with unstable angina. In this group of patients, delaying surgery is appropriate if the risk of surgery is greater than the potential benefits.

  
  
• 2.
  

  Acute or decompensated heart failure, which is defined as New York Heart Association functional grade IV disease, or worsening or new-onset heart failure.

  
  
• 3.
  

  Significant arrhythmias, which includes Mobitz II atrioventricular block, third-degree atrioventricular block, symptomatic ventricular arrhythmias, and supraventricular arrhythmias with uncontrolled ventricular rate symptomatic bradycardia.

  
  
• 4.
  

  Severe valvular disease including severe aortic stenosis (AS) and mitral stenosis (MS).

These active cardiac conditions prevent proceeding with noncardiac surgery unless it is an emergency surgery. These conditions are usually apparent from the history, physical examination, electrocardiography, and X-ray of the chest, and in a few patients echocardiography may be required to confirm the presence of severe valvular disease and type of heart failure.

Step 3 is to estimate the inherent risk of the surgical procedure. Procedures can be classified to be associated with a low risk (<1%) including endoscopic procedures, superficial procedures, and ambulatory surgery. Procedures with intermediate risk (1–5%) include carotid endarterectomy and head and neck surgery. High-risk (>5%) procedures include vascular surgery, for the development of perioperative adverse cardiac events (cardiac death and nonfatal MI) within 30 days after surgery.

Step 4: The new guideline recommends the assessment of functional capacity as an essential step in the preoperative estimation of cardiac risk. Functional capacity is measured in metabolic equivalents (METs). Poor functional capacity, i.e., a MET < 4, is equivalent to the inability to climb two flights of stairs or run a short distance. Patients with good functional capacity (MET > 4) might be listed for surgery without further perioperative assessment or specific drug therapy. Patients with a moderate or low functional capacity are at an increased risk of postoperative events, and the number of cardiac risk factors in combination with risk of the surgical procedure should be taken into consideration for further risk stratification. Patients in the intermediate group might be taken after appropriate investigations and medical therapy.

Step 5: During the preoperative evaluation after functional capacity assessment one should look for clinical risk factors. According to the ACC/AHA guidelines clinical risk factors are conditions that have been found to be associated in many studies with an increased risk of cardiac events at the time of noncardiac surgery. These risk factors are history of ischemic heart disease (IHD), history of compensated previous congestive heart failure (CHF), history of cerebrovascular disease, diabetes mellitus with or without preoperative insulin therapy, and renal insufficiency with creatinine level >2 mg/dL.

Patients who do not have these risk factors should proceed with noncardiac surgery without further preoperative cardiac assessment. In such cases, the incidence of major cardiac events would be around 0.5%. The ACC/AHA 2007 guidelines recommend that even a patient with poor functional capacity but without clinical risk factor should proceed directly to vascular surgery without testing.

For patients who have these risk factors decision making is more difficult; either they can proceed with the emergency surgery, low-risk surgery, or surgery in cases of good functional capacity or the surgery can be delayed for further evaluation and management of the active cardiac condition. Patients who are undergoing intermediate-risk surgery and have at least one or two clinical risk factors are either recommended to proceed with the planned surgery and management with drug therapy or could undergo further noninvasive cardiac testing.

Evaluation of the patient presenting for cranial or spine surgery involves the same assessment procedure that is applicable to any person who is exposed to anesthetic. The anesthesiologist should have mandatory knowledge of cardiac disease to approach the anesthetic management of such patients with neurosurgical problems.

Perioperative Monitoring

Although it is important to detect perioperative cardiac complications in patients undergoing neurosurgical procedures, proper monitoring should be performed in selected patients in whom cardiac problems are likely to occur for appropriate period of time. Unnecessary use of invasive monitoring should be avoided.

ECG monitoring is best performed for patients who come with arrhythmias or CAD. ST segment monitoring is of diagnostic and therapeutic value. ECG abnormalities occur in 50–72% of patients with intracranial pathology, some of which may not appear for 2 weeks after the first insult. These abnormalities are not for all time associated with cardiac problems. ECG changes are seen in patients with traumatic brain injury, status epilepticus, subarachnoid hemorrhage (SAH), and cerebral infarction. Possible causes of ECG abnormalities in a patient with intracranial pathology are acute MI simultaneous with SAH, acute MI caused by SAH, and ECG changes without acute MI. It is preferable to continue the ECG monitoring till the preoperative drug therapy for cardiac complications has been resumed.

BP: Patients at risk of abrupt hemodynamic changes during neurosurgery should be continuously monitored for BP with an arterial line.

Central venous line, pulmonary artery (PA) catheter: a central venous pressure (CVP) line should be placed in patients where significant hemodynamic changes are expected during the perioperative period. It is needed for inotropic support and fast fluid administration. However, CVP line gives limited information about hemodynamic condition; monitoring using PA catheter may facilitate detailed information of hemodynamics in high risk neurosurgical cases.

Transesophageal echocardiography (TEE): There is insufficient evidence to determine the cost-effectiveness of TEE for its use as a diagnostic monitor or to guide therapy during noncardiac surgery; therefore routine use of TEE in noncardiac surgery does not appear warranted. In contrast, emergent use of intraoperative or perioperative TEE to determine the cause of an acute, persistent, and life-threatening hemodynamic abnormality is indicated (Level of evidence: B). During neurosurgery TEE can diagnose venous air embolism, where it is not advocated purely.

Ischemic Heart Disease