Cases from the Medical College of Wisconsin

A group of cases focused on preoperative evaluation.


Case 1: Obstructive sleep apnea screening

By Brian Quinn, MD, ACP Member, and Chad Wenzel, MD, ACP Member

The patient

A 57-year-old man presented to the preoperative clinic for evaluation prior to an elective rotator cuff repair. His medical history included hypertension and hyperlipidemia, treated with a calcium-channel blocker and a statin, respectively. His surgical history was notable for an uneventful laparoscopic cholecystectomy under general anesthesia five years ago. On review of systems, he reported daytime sleepiness and indicated that his roommate noted his loud snoring. He did not report any chest pain or shortness of breath and had no exertional limitations with his physically demanding occupation as a warehouse manager.

On physical exam, pertinent findings included a blood pressure of 158/94 mm Hg, a heart rate of 88 beats/min, and normal respiratory rate and oxygen saturation. He was morbidly obese with a body mass index of 45 kg/m2 and a neck circumference of 47 cm. His cardiopulmonary exam was unremarkable. A recent complete blood count and basic chemistry panel were normal, with the exception of an elevated bicarbonate level (32 mEq/L). This patient's STOP-BANG score was calculated to be 7 points, qualifying as high risk for obstructive sleep apnea (OSA). Preoperative formal polysomnography demonstrated moderate-severity OSA. The patient was started on continuous positive airway pressure (CPAP) and underwent the orthopedic procedure without complication.

The diagnosis

Patients with OSA have increased risk of postoperative respiratory complications, including hypoxic respiratory failure, reintubation, encephalopathy, transfer to ICU, atrial fibrillation, and increased length of stay. Preoperative screening has found OSA in 24% to 41% of patients, and up to 80% are unaware that they have it. A validated screening tool for OSA, such as the STOP-BANG, can risk-stratify patients based on their likelihood of undiagnosed sleep apnea. The STOP-BANG is a questionnaire that screens for symptoms (including daytime drowsiness, snoring, and observed periods of apnea), in addition to objective physical characteristics associated with OSA. This tool can be used to trigger formal polysomnography evaluation, which is recommended if the patient's score is 3 or above in the presence of hypercapnia/hypercarbia or 5 or above in the presence of uncontrolled systemic disease/hypoxia.

An elevated serum bicarbonate level increases suspicion for apnea/hypopnea resulting from intermittent hypercapnia. Patients already diagnosed with OSA and using positive airway pressure therapy should bring their own equipment for use during a hospital stay. High-risk patients should use auto-CPAP postoperatively. Careful attention should be paid to the use of anesthetic (consider regional or local anesthesia), analgesic (minimize opioids), and sedating medications to reduce risk of postoperative complications. A more conservative postoperative setting and continuous pulse oximetry monitoring may be considered for patients with OSA, as can follow-up at a sleep center after discharge.

Pearls

  • Screening for OSA can potentially mitigate postoperative pulmonary complications.
  • STOP-BANG is a validated risk assessment tool that can be used to trigger formal polysomnography evaluation for OSA in undiagnosed patients.

Case 2: Preoperative anticoagulation in nonvalvular atrial fibrillation

By Sara Dunbar, DO, ACP Member, and Chad Wenzel, MD, ACP Member

The patient

An 82-year-old man presented to preoperative clinic for evaluation prior to receiving a cochlear implant for right sensorineural hearing loss. His medical history was significant for paroxysmal atrial fibrillation on warfarin, hypertension, heart failure with reduced ejection fraction of 25% and implantation of an automatic implantable cardioverter-defibrillator one year prior, transient ischemic attack (TIA) seven years prior, and hyperlipidemia.

On physical examination, his blood pressure was 136/77 mm Hg and his heart rate was 73 beats/min, with an irregularly irregular rhythm without murmurs. No jugular venous distention was identified, and clear lung fields were present with trace leg edema. His electrocardiogram confirmed atrial fibrillation. Laboratory evaluation showed an international normalized ratio (INR) of 2.7 with a creatinine level of 0.98 g/dL. Warfarin was held five days prior to surgery, and due to the patient's history of TIA and CHA2DS2-VASc score of 5, he and his clinician chose to bridge with low-molecular-weight heparin (LMWH) perioperatively.

The diagnosis

Whether to interrupt anticoagulation perioperatively, with or without bridging, depends on many factors and is ultimately a decision to be made among the patient, preoperative clinician, and surgeon. For surgeries with low bleeding risk (e.g., cataract surgery), anticoagulation discontinuation may not be required. Procedures with moderate to high bleeding risk will often require interruption of oral anticoagulants. The time frame for withholding anticoagulation depends on the medication being used. Vitamin K antagonists (VKAs) should be held for five days (if a patient's INR is 2 to 3) or greater than five days (if the INR is >3) preoperatively. Whether to withhold direct oral anticoagulants (DOACs) depends on the procedural bleeding risk and the patient's creatinine clearance, as these drugs are renally cleared. In addition, DOACs, due to their shorter half-life, do not requiring bridging.

The decision to bridge a patient on a VKA with nonvalvular atrial fibrillation depends on thromboembolic risk, patient characteristics, clinical judgment, and patient preference. Those with a CHA2DS2-VASc score of less than 5 without previous stroke or TIA do not typically require bridging because they have low risk of thromboembolism. However, bridging should be initiated for patients at high risk of thromboembolic disease, such as those with a CHA2DS2-VASc score of greater than 6 (as long as there is no increased bleeding risk), atrial fibrillation and rheumatic valve disease, or a history of venous thromboembolism (VTE) within the past three months. Patients with a CHA2DS2-VASc score of 5 or 6 are at moderate risk for thromboembolic events and may be considered for bridging. Other patient characteristics must also be considered, including bleeding risk factors and history of intracranial hemorrhage or recurrent VTE.

Pearls

  • Perioperative bridging of anticoagulation for nonvalvular atrial fibrillation should mainly be considered in patients on VKAs; patients on DOACs typically do not require bridging per current guidelines.
  • Management of anticoagulants in the perioperative setting depends on many factors, including the bleeding risk of the procedure, patient characteristics, thromboembolic risk, and clinical judgment.

Case 3: Perioperative valvular heart disease

By Chad Wenzel, MD, ACP Member; Sara Dunbar, DO, ACP Member; and Shpresa Shyti, ANP

The patient

A 63-year-old man with a history of psoriatic arthritis presented with a right intertrochanteric femur fracture sustained in a traumatic injury at work. During the preoperative evaluation, the patient noted a decreased exercise tolerance over the prior four months, with associated shortness of breath. He reported no chest pain, nausea, vomiting, or arm pain in the last year and was still able to complete more than 4 metabolic equivalents (METS) on presentation.

Vital signs were most notable for mild hypoxia requiring 2 L of supplemental oxygen. Cardiopulmonary exam was significant for an S3 gallop, inspiratory crackles, jugular venous distention, and two systolic murmurs. The first murmur was harsh, at the aortic site, and radiated to the carotid arteries; the other was holosystolic, located at the apex, and radiated to the axilla. Electrocardiogram noted sinus tachycardia with borderline left ventricular hypertrophy.

Transthoracic echo (TTE) showed severe mitral regurgitation, moderate to severe aortic stenosis, reduced ejection fraction of 36%, and pulmonary hypertension (pulmonary artery systolic pressure of 53 mm Hg). After discussion with cardiology and high-risk anesthesia consultants, the patient was given loop diuretics and was deemed healthy enough for surgical femur repair. Later in the admission, he underwent double valve replacement with cardiothoracic surgery.

The diagnosis

Assessment and treatment of valvular cardiac disease are crucial components of perioperative patient management and frequently require a multidisciplinary approach. Patients may present with previously undiagnosed murmurs and no recent cardiac assessment. Guidelines from the American College of Cardiology and American Heart Association recommend imaging prior to nonemergent surgery for newly diagnosed murmurs (including those that are harsh, loud, or potentially symptomatic) and murmurs previously known to be moderate to severe in nature without a TTE within the last year. In addition, prior to any surgical intervention, patients found to have severe disease warrant cardiac and anesthesia specialist input, including assessment for potential heart valve repair or replacement.

Postoperatively, these patients present significant challenges, as they are particularly susceptible to cardiac preload and afterload changes caused by surgery. These can include changes in blood pressure from pain, withheld or missed antihypertension medications, or blood loss anemia, as well as significant fluid shifts during volume resuscitation. Essential tenets of evaluation include a detailed daily physical exam, strict intake/output monitoring, daily weight measurement, and laboratory assessment of renal function. Judicious control of blood pressure and volume status with diuretics, antihypertensives, and pain medications form the backbone of the treatment regimen.

Pearls

  • Patients presenting for preoperative evaluation with new or concerning murmur or a history of significant murmur should be evaluated with TTE and subspecialty consultation as appropriate.
  • Ongoing examination and corresponding management of preload and afterload states during the perioperative period are critical in those with significant valvular disease.

Other cases in this issue