The neurohospitalist has the responsibility of caring for the hospitalized medically fragile neurological patient but also understanding the risk stratification for surgery and the potential anesthetic and medical complications that are unique to neurological patients who are having emergent or elective procedures. The neurohospitalist should be able to describe the relative surgical risk to the patient. Protocols for stratifying surgical risk have been developed, some of which are available as apps on digital devices. Where possible we have mentioned whether an app is currently available.

Important aspects of perioperative management of the neurologic patients include management of chronic neurologic disorders (seizures, neuromuscular disorders, multiple sclerosis [MS], neurodegenerative diseases), appropriate risk stratification for surgical procedures, minimizing cerebrovascular risk during any hospitalization or procedure, minimizing sedation by choosing appropriate agents, and prevention of delirium.

This chapter will review the following topics:

1. 
   

   Preoperative risk assessment

   
   
2. 
   

   Timing of surgical procedures with comorbid cerebrovascular disease

   
   
3. 
   

   Seizure disorder management perioperatively

   
   
4. 
   

   Neuromuscular disorder management perioperatively

   
   
5. 
   

   Neurodegenerative disorders, including Parkinson disease, management perioperatively

   
   
6. 
   

   MS management perioperatively

   
   
7. 
   

   Perioperative delirium prevention and treatment

How do you perform preoperative risk assessment?

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  The medical or surgical team may perform this clinical assessment.

  
  
• 
  

  The patient’s demographics, past medical history, functional status, current active medical illnesses, and the procedure planned all contribute to this assessment.

How is the urgency and risk of the procedure assigned?

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  The American Heart Association (AHA) has defined the urgency and risk for procedures.

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  Urgency is defined as follows:

  
  
  
  
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    Emergency is used to describe a threat to life or limb with no or minimal time for clinical evaluation, usually within 6 hours.

    
    
  • 
    

    Urgency describes a threat to life or limb with time for a limited clinical evaluation prior to the surgical procedure, usually 6–24 hours.

    
    
  • 
    

    Time-sensitive references a negative outcome if there is a delay of more than 1–6 weeks for an evaluation and significant management changes to be made.

    
    
  • 
    

    Elective is used when a procedure may be delayed for up to 1 year to perform clinical evaluation and institute appropriate management changes.

  
  
  
  
• 
  

  Specific categories have been assigned by the AHA based on predicted risk of a major adverse cardiac event (MACE) of death or myocardial infarction (MI) as well.

  
  
  
  
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    Low-risk procedures have a predicted risk of <1%.

    
    
  • 
    

    Elevated risk procedures have a >1% chance of MACE. They have combined intermediate and high risk into this category due to the recommendations being the same for both previous categorizations.

  
  

What tools are commonly used for risk assessment?

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  There are different risk calculators available.

  
  
• 
  

  The ACS NSQIP surgical risk calculator was developed in 2013 and calculates a risk for the specific surgery planned using the CPT codes for the procedure.²

  
  
  
  
  • 
    

    The website for this risk calculator is http://www.riskcalculator.facs.org.

    
    
  • 
    

    It was developed based on prospective data incorporating more than 1.4 million operations in 525 hospitals.

    
    
  • 
    

    Twenty-two different variables are included.

    
    
  • 
    

    A few major drawbacks of this risk assessment tool are as follows: the fact that it has never been externally validated outside of the database population and the definition of MI is limited in scope (only STEMI or troponin increase greater than 3 times normal are included). Also, this incorporates the ASA (American Society of Anesthesiology) physical class, which has poor inter-rate reliability.

  
  
  
  
• 
  

  ACS NSQIP MICA risk (Gupta risk model)³

  
  
  
  
  • 
    

    The website for this risk calculator is http://www.qxmd.com/calculate-online/cardiology/gupta-perioperative-cardiac-risk.

    
    
  • 
    

    The score was developed in 2011 and also used the ACS NSQIP database. At the time of its development there were more than 400,000 patients and 250 hospitals in the database.

    
    
  • 
    

    Age, functional status, creatinine level of greater than 1.5 mg/dL, and type of surgery are the variables used in this risk model.

    
    
  • 
    

    This score did outperform the RCRI in discriminative power, especially vascular surgery procedure risk.

    
    
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    Known or remote CAD, except for PCI or prior cardiac surgery, was not controlled for in a multivariate analysis.

    
    
  • 
    

    It also has no external validation outside of the database population and includes the ASA physical class.

  
  
  
  
• 
  

  Revised Cardiac Risk Index (RCRI, Revised Goldman Score)⁴

  
  
  
  
  • 
    

    The website for this calculator is http://www.mdcalc.com/revised-cardiac-risk-index-for-pre-operative-risk.

    
    
  • 
    

    Originally developed by Goldman et al in 1977, this scoring system underwent a revision in 1999.

    
    
  • 
    

    Major cardiac complications were defined as cardiac arrest or ventricular fibrillation, MI, pulmonary edema, or complete heart block.

    
    
  • 
    

    This scoring system is relatively simple to use: one point is assigned for each risk category (history of cardiac ischemia, CHF, or cerebrovascular disease; preoperative insulin treatment, creatinine elevation >2 mg/dL, and if the surgery is considered high risk). If the patient scores more than or equal to 2 points, the risk of major adverse cardiac events is elevated.

    
    
  • 
    

    External validation has been performed on this risk assessment tool unlike the other two discussed.

    
    
  • 
    

    The data set to derive this risk index was significantly smaller (around 4000 patients) (Table 35-1).

  
  

How would you characterize this patient’s perioperative cardiac risk?

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  Using the risk models described previously:

  
  
  
  
  • 
    

    ACS NSQIP surgical risk calculated is 3.3% cardiac death or MI within 30 days of surgery (above average)

    
    
  • 
    

    ACS NSQIP MICA (Gupta) risk calculated is 0.55%, which puts him close to 75th percentile.

    
    
  • 
    

    RCRI (Revised Goldman) risk calculated is Class IV (11% risk of major cardiac event)

  
  

Should any preoperative testing to be done?¹

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  According to the 2014 AHA guideline on perioperative cardiovascular evaluation and management, a patient with stable atrial fibrillation does not require any special preoperative testing.

  
  
• 
  

  For a patient with known CAD, the AHA has developed an algorithm for decision making regarding preoperative testing (see Figure 35-1).

  
  
  
  
  • 
    

    Step 1 is to decide if the surgery is emergent; if the answer is yes, clinical risk stratification is the only procedure necessary.

    
    
  • 
    

    If the surgery is nonemergent and the patient is not currently having acute coronary syndrome, clinical risk stratification is done first followed by functional capacity assessment.

    
    
  • 
    

    Patients with a function capacity of 4 metabolic equivalents (METs) or higher do not need further preoperative testing.

    
    
  • 
    

    If the functional capacity is less than 4 METs or unknown and the clinician feels further testing will impact medical decision making, a pharmacologic stress test is a Class IIa recommendation.

    
    
  • 
    

    A patient who does undergo pharmacologic stress testing and has an abnormal result should undergo coronary revascularization (Class I) according to current clinical practice guidelines.

    
    
  • 
    

    In addition, it is reasonable to perform a 12-lead electrocardiogram on any patient with a history of coronary or structural heart disease for whom an elevated risk procedure is planned. Reassessment of left ventricular (LV) function if the patient is known to have stable LV dysfunction is also appropriate to consider.

  
  

What are some general medication recommendations?

• 
  

  Patients who have high or intermediate risk preoperative test results, ≥3 RCRI risk factors, or chronically use beta blockers should receive perioperative beta blockade. Sudden cessation of a beta-blocker in a patient with (CAD) is not advisable.

  
  
• 
  

  Statin medications should also be continued if they are outpatient medications, or newly initiated if undergoing vascular surgery.

  
  
• 
  

  It is reasonable to continue angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARB).

  
  
• 
  

  It is reasonable to hold oral antihypertensive medication perioperative in lieu of intravenous titratable therapy.

What are the recommendations for patients on antiplatelet agents?

• 
  

  If the noncardiac surgery is urgent or emergent:

  
  
  
  
  • 
    

    Patients with stent in place ≤4–6 weeks: The clinician must weigh the risks and benefits of ischemia and bleeding. Patients should continue dual antiplatelet, aspirin and an ADP inhibitor, therapy (DAPT) at least 4–6 weeks after bare metal stent (BMS) or DES unless the risk of bleeding outweighs the risk of stent thrombosis.

    
    
  • 
    

    Patients with DES ≥30 days but ≤365 days: If the risk of surgical delay is greater than the risk of stent thrombosis, the surgery should proceed after 180 days if possible.

    
    
  • 
    

    Patients with DES > 365 days: If the surgical procedure planned requires discontinuation of the ADP P2Y12 inhibitors (eg, clopidogrel), the patient should continue on aspirin therapy perioperatively with the plan to restart P2Y12 inhibitor as soon as safely possible post-operatively.

  
  
  
  
• 
  

  If the noncardiac surgery is elective:

  
  
  
  
  • 
    

    DES patients should have procedure delayed until after 365 days from stent placement.

    
    
  • 
    

    There are some data to suggest that in the new-generation DESs the risk of stent thrombosis is lessened after 6 months, and after this time, noncardiac surgery may be performed without increased risk.

    
    
  • 
    

    BMS patients should have procedures delayed until after 30 days from stent placement.

  
  
  
  
• 
  

  In general, cessation of antiplatelet agents, if required, should occur 3 days prior to a procedure for aspirin and 5 days prior for ADP P2Y12 inhibitors.

What are the recommendations for management of patients on anticoagulants?

• 
  

  The CHA2DS2-VASc score gives us the risk of a cerebrovascular event in patients with atrial fibrillation (see Table 35-2). This patient has a score of 6 points, which infers a 9.8% per year or 0.027% per day risk of stroke while off anticoagulation.⁵ The patient can be switched to heparin preoperatively with a discontinuation the day of surgery. His warfarin should be held at least and possibly reversed if there is an acute need to lower his international normalized ratio (INR).

  
  
• 
  

  Anticoagulation in elective procedures with minimal to no risk of bleeding (cataract or minor dermatologic surgery) may be continued.

  
  
• 
  

  Anticoagulation in atrial fibrillation (Afib)^6,7

  
  
  
  
  • 
    

    Warfarin

    
    
    
    
    • 
      

      Patients with Afib who are at low risk of thromboembolism and currently in sinus rhythm, if surgical hemostatic control is vital, may stop the warfarin 1 week prior to the procedure and restart immediately postoperatively.

      
      
    • 
      

      In patients at high risk for thromboembolism (CHADs-VASC ≥2, prior stroke, or mechanical valves), bridging therapy with heparin is a common approach during perioperative period.

      
      
    • 
      

      The recently completed BRIDGE study showed that patients with Afib undergoing an elective procedure not performing bridging therapy with low molecular weight heparin was non-inferior and associated with lower risk of major bleeding. This study excluded patients with mechanical heart valaves or stroke.⁸

    
    
    
    
  • 
    

    Oral factor Xa and direct thrombin inhibitors⁹

    
    
    
    
    • 
      

      The evidence is extremely limited. The appropriate time to discontinue oral anticoagulants is based on the pharmacokinetics and risk of surgical bleeding (see Tables 35-2 and 35-3).¹⁰

      
      
    • 
      

      For emergent surgery, clinicians also have to consider that there is no good reversal agent for these medications.

      
      
    • 
      

      In ROCKET AF and RE-LY, oral anticoagulants were held for 48 hours prior to elective surgery and 24 hours before urgent surgery. RE-LY had a recommended schedule for stopping dabigatran based on creatinine clearance.¹¹

      
      
    • 
      

      Rivaroxaban has been chemically reversed with 4-component prothrombin complex concentrates in normal volunteers.¹²

    
    

  
  
  
  
• 
  

  Anticoagulation for prosthetic valves

  
  
  
  
  • 
    

    The AHA/ACC 2014 valvular heart disease guidelines address this issue.

    
    
  • 
    

    For minor surgical procedures, patients with a mechanical heart valve may continue their vitamin K agonist (VKA, usually warfarin).

    
    
  • 
    

    Patients with a bileaflet mechanical aortic valve and no other risk for thrombosis may have VKA held 2–4 days preoperatively (goal INR <1.5) without bridging therapy for invasive surgical procedures. The VKA should be restarted as soon as possible taking into consideration the postoperative bleeding risk, usually 12–24 hours after the surgical procedure.

    
    
  • 
    

    Patients with a bileaflet mechanical aortic valve and other thrombotic risk factors, or a mechanical mitral valve should receive bridging therapy during the time that INR is subtheraputic perioperatively.

  
  
  
  
• 
  

  Anticoagulant reversal for emergency procedures¹³

  
  
  
  
  • 
    

    Fresh-frozen plasma (FFP) or PCCs can be administered for emergency surgical procedures in patients with prosthetic valves and Afib who are taking VKA and non-valvular Afib patients on oral factor Xa inhibitors.

    
    
  • 
    

    The PCC has the advantage of faster reversal and less volume prior to surgery.

    
    
  • 
    

    Hemodialysis will remove 40–60% (unbound portion) of dabigatran. In a recently published study, REVERSE_AD, idarucizumab, completely reversed the anticoagulant effect of dabigatran within 10 minutes. This medication received expedited approval from the FDA in October 2015.¹⁴

    
    
  • 
    

    The recently published ANNEXA-A and ANNEXA-R studies showed that andexanet, a modified factor Xa molecule, was associated with prompt and potent reversal of factor Xa inhibitors apixaban and rivaroxaban.¹⁵