Friday, March 19, 2021

Chronic Obstructive Pulmonary Disease Case File

Posted By: Medical Group - 3/19/2021 Post Author : Medical Group Post Date : Friday, March 19, 2021 Post Time : 3/19/2021
Chronic Obstructive Pulmonary Disease Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 25
A 53-year-old woman with long-standing chronic obstructive pulmonary disease (COPD) presents for a laparoscopic cholecystectomy. Her past medical history includes hypertension well-controlled with lisinopril, a 40-pack-year history of smoking, and resultant COPD. 

The patient states that she can do her own grocery shopping, but that she often has to stop and rest when she gets short of breath. She states that she had the flu 6 to 7 months ago, which aggravated her COPD resulting in hospitalization. She currently uses an Advair inhaler (a long-acting beta agonist) and Spiriva (a long-acting anticholinergic agent). Approximately once a week she also uses a Ventolin inhaler for breakthrough therapy. The patient was recently referred to a pulmonologist, who added oral steroids to her regimen. Since the adjustment of her medical regimen, she has had more energy to devote to activities. 

Her vital signs are BP of 140/80 mm Hg, a heart rate of 85 bpm, and her respiratory rate is of 24 breaths per minute. She does not use accessory muscles of respiration, and can speak in complete sentences. Her laboratory blood tests are normal.

➤ What are your concerns during preoperative evaluation for this patient?

➤ What are the ventilator strategies for this patient?

➤ What are the likely postoperative concerns for this patient?


ANSWERS TO CASE 25:
Chronic Obstructive Pulmonary Disease

Summary: This 53-year-old woman is a controlled COPD patient presenting for a laparoscopic cholecystectomy under general anesthesia.

Preoperative evaluation: In patients with COPD should include the history regarding the adequacy of long-acting inhaler therapy, the frequency of pneumonia and bronchitis, and duration of oral steroid therapy including when it was last administered. Several bouts of pneumonia per year as well as frequent requirements for short-acting agents signify inadequate outpatient therapy, and significantly increase the patient’s risk of surgery.

Ventilator strategies: COPD results in loss of elastic recoil of the alveoli in the lungs. As a result, the alveoli need a longer time to exhale. Thus the inspiratory/expiratory ratio needs to be adjusted on the ventilator. Since the patient has been on an indefinite number of days of steroid therapy, adrenal insufficiency needs to be considered in the differential diagnosis of refractory hypotension should it occur.

Likely postoperative concerns: In the post-anesthetic period this patient is at the highest risk for pulmonary complications including but not limited to hypoxia, bronchospasm, and pneumonia.


ANALYSIS

Objectives
1. Understand the issues involved in the preoperative evaluation and assessment of suitability for surgery in a patient with COPD undergoing elective surgery.
2. Understand the intraoperative management of ventilation under general anesthesia in a patient with COPD.
3. Understand postoperative complications in a patient with severe COPD.


Considerations
This is a 53-year-old obese woman who presents for a laparoscopic cholecystectomy under general anesthesia. She has moderately severe COPD, which seems to be under reasonable control. However, she is currently treated with long-acting beta-2 agonists, which have been shown to actually increase the mortality in patients with asthma. She has required steroids in the past 6 months, which suggests that her COPD is moderately severe. In addition, the exposure to steroids also predisposes the patient to the possibility of adrenal insufficiency.

The standard monitors recommended by the American Society of Anesthesiologists (ASA) are sufficient, and there is no real indication for invasive monitoring in this case. During induction and maintenance, agents such as thiopental and desflurane should be avoided since the former can cause bronchoconstriction, and the later is the most irritating general anesthetic to the airway. Following the induction of general anesthesia, the ventilator’s inspiratory/expiratory ratio is adjusted to accommodate the patient’s prolonged expiratory phase, and a small amount of PEEP is added to decrease work of breathing. Both of these maneuvers result in optimal peak and plateau pressures.

The patient’s pulmonary function tests indicate that she has small airways and an element of broncho-reactivity. This renders her susceptible to bronchospasm, and also responsive to bronchodilator agents. The patient should be asked to use her inhalers prior to surgery.

Laparoscopic cholecystectomy is typically associated with little blood loss, so the fluid management should be judicious given the higher likelihood for pulmonary edema in this patient. Indeed, a common saying is “keep the lungs dry,” and it applies to many if not most pulmonary surgical procedures. The presence of COPD exacerbates the possibility of atelectasis, pneumonia, and hypoxemia in the postoperative period. Pain control is an important consideration in the postoperative period. The use of narcotics may potentiate respiratory depression and failure in the setting of atelectasis, while inadequate pain control may result in splinting and inadequate respiratory effort, which will exacerbate atelectasis as well.


APPROACH TO
Chronic Obstructive Pulmonary Disease

DEFINITIONS
COPD: Chronic obstructive pulmonary disease (COPD) is a slowly progressive lung disease that results in progressive shortness of breath and a declining activity level. It includes a spectrum of illnesses such as emphysema and chronic bronchitis.

LAPAROSCOPIC CHOLECYSTECTOMY: Surgical procedure of removal of the gall bladder via small incisions on the abdomen. The entire abdominal cavity is visualized by means of a laparoscope inserted after creation of a pneumoperitoneum.

CLINICAL APPROACH

Preoperative Evaluation
The preoperative evaluation for any patient prior to surgery includes assessment of exercise tolerance. In the setting of COPD, focused questioning may reveal a subtle decline in exercise over a period of years (eg, using a push lawn mower to a power lawn mower to paying someone to mow the lawn). Primary care physicians often have a low threshold for cardiac stress testing, to ferret out presence of concomitant cardiac disease.

In a patient with proven COPD, the next assessment should be the adequacy of therapy. A stable inhaler regimen with minimal use of breakthrough inhalers, no requirement for oral steroids, and an absence of frequent bronchitis/pneumonia represent “stable” COPD. A subset of patients with COPD has alveolar thickening and loss of lung area, resulting in a decrement in diffusion capacity for carbon monoxide (DLCO). A low DLCO implies an impaired oxygen uptake by the alveolus, and may necessitate implementation of home oxygen therapy. Other causes of low DLCO are cardiac insufficiency, anemia, and pulmonary hypertension.

Pulmonary function tests may identify a response to bronchodilator therapy, if it is present. Oddly, broncho-reactivity is most common in the moderate stage of COPD. Resting arterial blood gas testing helps identify the level of baseline ventilation as evidenced by degree of arterial carbon dioxide (CO2) retention, as does the bicarbonate (HCO3) level. In the presence of an elevated PaCO2, there is typically a conservation of HCO3 by the kidney. Thus, elevated CO2 in patients with COPD is often accompanied by a concomitant increase in HCO3. It is important to have baseline CO2 and HCO3 levels, as they determine the intraoperative ventilation strategies. Hyperventilation in these patients, in attempt to normalize CO2, leads to renal bicarbonate wasting and metabolic acidosis.


Intraoperative Management
In patients with a significant bronchospastic component to their COPD, patients should be asked to use their inhalers prior to the induction of general anesthesia. Routine monitoring is appropriate. Thiopental and histaminereleasing drugs such as morphine and succinylcholine should be avoided if possible. Laryngoscopy and intubation should only be attempted after ensuring an adequate depth of anesthesia, or bronchospasm may result. One option involves spraying the trachea with 4% lidocaine prior to intubation. While the lidocaine does anesthetize the trachea and reduce the foreign body response to intubation, the spray occasionally also provokes a foreign body response. Use of this maneuver varies widely by practitioner.

The anesthetic maintenance regimen typically includes a combination of inhaled agents and narcotics. Respiratory management should take into account the pathophysiology of COPD, which involves the loss of alveolar elasticity and impaired ventilation/perfusion mismatch (V/Q). The extent of V/Q mismatch in COPD reflects the extent of lung tissue destroyed. During exacerbations of COPD, V/Q mismatch worsens. Ventilator management includes a long exhalation time to counter the loss of alveolar elasticity. The judicious use of PEEP can improve oxygenation in the setting of hyperinflation. PEEP also increases the intrathoracic pressure somewhat, and if excessive, can impair venous return. The optimal level of PEEP does not decrease cardiac output (blood pressure can be used as a surrogate for cardiac output).

The emergence from general anesthesia is a critical time for patients with COPD. Rapid shallow breaths of low tidal volume are consistent with respiratory failure. This breathing pattern can be followed by progressive hypercapnia, respiratory muscle fatigue, and respiratory failure. Noninvasive positive pressure ventilation (NPPV) increases patient comfort while decreasing the work of breathing, and over the long term decreases mortality. NPPV is commonly administered in the form of bi-level positive airway pressure (BiPAP) by means of a specialized BiPAP mask. This form of ventilation decreases atelectasis, improves oxygenation, and also decreases work of breathing. However, it does require concerted patient cooperation.

Fluid management in patients with COPD is targeted toward euvolemia. In the presence of significant lung dysfunction, even a minor fluid overload can precipitate pulmonary edema and delay tracheal extubation. Neuraxial blockade is the preferred anesthetic in a patient with severe COPD if the procedure is amenable, as there is a decreased incidence of respiratory depression and failure.

In addition to bronchospasm, other complications should be considered when caring for a patient with COPD. Sudden cardiovascular collapse could represent a ruptured emphysematous bleb, particularly if mechanical (positive pressure) ventilation is used. And if the patient is on steroids, the presence of sustained hypotension after anesthetic causes have been eliminated, the possibility of adrenal insufficiency secondary to prolonged steroid use should be considered. It is common practice to administer supplemental “stress-dose” of steroids; typically, hydrocortisone is administered every 6 hours for the first 24-hour period. However, this practice and steroid regimen are entirely empirical, and has not been shown to influence outcomes.


Postoperative Management
Postoperative pain relief is vital in the presence of COPD. Pain increases patient splinting and predisposes them to atelectasis and pneumonia. However, narcotics are also associated with respiratory depression and the requirement for re-intubation. BiPAP is an option as a treatment for hypoxemia. Weaning from BiPAP is dictated by patient comfort (no use of accessory muscles, adequate oxygenation, and ventilation) as well as pulse oximetry.


Comprehension Questions

25.1. A 50-year-old man with stable severe COPD has just undergone a radical prostatectomy. His intraoperative course was uncomplicated. Currently he is in the post-anesthesia care unit (PACU) with a respiratory rate of 28, SpO2 94% on 6 L oxygen by a simple facemask. When breathing, he uses his alae nasi and intercostal muscles. Pain is controlled with a patient controlled analgesic regimen. The nurse calls you to assess this patient, as he doesn’t “look right.” What is your first step?
A. Intubate the trachea
B. Institute BiPAP after getting an arterial blood gas
C. Administer naloxone
D. Administer diuretic

25.2. What is the role of PEEP?
A. Improves oxygenation
B. Decreases atelectasis
C. Decreases cardiac output
D. Decreases the risk of pneumothorax

25. 3. In the preoperative clinic, a 50-year-old woman presents for a laparoscopic adrenalectomy for a benign adenoma. She has a history of progressive shortness of breath over the past couple of years, and a slight but steady decrease in her functional capacity. She needs oxygen at night to help her breathe. Her past medical history includes well-controlled hypertension (with one drug, onset of disease 3 years ago). She is not obese but does appear to use accessory muscles of respiration. What would your differential diagnosis include?
A. Cardiac failure
B. COPD exacerbation
C. Asthma
D. Being in poor physical shape


ANSWERS
25.1. B. General anesthesia with intubation and positive pressure ventilation most often causes a small degree of atelectasis, which is usually clinically insignificant. In patients with COPD, any loss of lung function can precipitate respiratory distress and failure. This patient demonstrates increased work of breathing by use of accessory muscles and is mildly hypoxemic. Both of these symptoms can be alleviated by use of BiPAP, which will both open up atelectatic alveoli as well as decrease work of breathing. If NPPV fails as evidenced by rising CO2 and no change in work of breathing, it is appropriate to intubate the trachea and institute controlled ventilation. There is no evidence of pulmonary edema to warrant use of a diuretic prior to NPPV. Overuse of narcotics commonly results in a low respiratory rate with large tidal volumes progressing to apnea. Serial arterial blood gas analysis will assess adequacy of both oxygenation and ventilation and thereby guide success of therapy.

25.2. D. PEEP prevents total collapse of alveoli at end exhalation. The stinting open of the alveoli prior to the next breath helps increase the amount of lung mass participating in gas exchange. PEEP decreases V/Q mismatch by decreasing atelectasis and thereby improves both oxygenation and ventilation. PEEP increases intrathoracic pressure, which can be impedance to venous return and cardiac output. PEEP increases, not decreases, the risk of pneumothorax.

25.3. B. COPD presents as slowly progressive shortness of breath and fatigue. Exacerbations are marked by hypoxemia, and an increase in respiratory work secondary to bronchitis or inadequate control. Her hypertension is not long standing and has been controlled with a single agent. While cardiac or coronary artery disease is in the differential diagnosis, the likelihood of this being a primary event is unlikely. A stress test should be performed if inhalers do not alleviate her symptoms. New-onset asthma presents with a more acute picture and is lower on list of probable diagnosis. In this patient, being physically out of shape is an unlikely explanation for shortness of breath requiring oxygen at night.


Clinical Pearls
➤ Frequency of COPD exacerbations indicates medical control of this disease process.
➤ Loss of alveolar elasticity favors auto-PEEP development in the presence of incorrect ventilator management.
➤ Fluid management needs to be precise to avoid alveolar flooding and hypoxia while maintaining euvolemia.
➤ Postoperative respiratory complications tend to increase length of stay and worsen patient satisfaction. They can range from hypoxia and bronchospasm to ventilator dependence and respiratory failure.

References

Licker M, Schweizer A et al. Perioperative medical management of patients with COPD. Int Chron Obstruct Pulmon Dis. 2007;2:493-515. 

Miller RD. Anesthetic management of concomitant diseases: Chronic obstructive pulmonary disease. In: Miller’s Anesthesia. 6th ed. Philadelphia, PA: Elsevier; 2005: Chapter 27.

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