The inspired and expired air may be sometimes very useful, by condensing and cooling the blood that passes through the lungs; that depuration of the blood in that passage is not only one of the ordinary, but one of the principal uses of respiration.
Postoperative respiratory complications (PRCs) substantially contribute to the risks of surgery and anesthesia and occur with a higher incidence in the elderly (Canet and Mazo 2010).
An official definition has not yet been provided; in the complex galaxy of perioperative respiratory events, some can remain sub-clinical, some may require oxygen delivery or non-invasive respiratory support, whereas others even require ICU admission and conventional mechanical ventilation. A heterogeneous group of conditions occurring after surgery can be grouped under this label, including a variety of symptoms, such as a PaO2 <60 mmHg on room air, a ratio of PaO2/FiO2 <300, or a SpO2 <90% and the dependency of oxygen insufflation (Mazo et al. 2016). Suspected or patent pulmonary infection, requiring antibiotic treatment, is another feature of PRC. Further, unplanned reintubation, weaning failure, pleural effusion, atelectasis, pneumothorax, bronchospasm, aspiration pneumonitis and adult respiratory distress syndrome (ARDS) are also features of PRC (Mazo et al. 2014, 2016). Consequences include increased mortality, increased length of hospital stay and increased treatment costs. Associated mortality ranges between 8 and 24% (Mazo et al. 2014, Canet et al. 2015). A duration of 5–7 postoperative days coincides with an adequate timeframe to diagnose PRC.
In the last 15 years, several factors have been identified for the risk stratification of PRCs (see Table 39.1). Based on the ARISCAT score, three levels of severity for predicting postoperative respiratory failure with a 82% accuracy were identified in 2015 (Canet et al. 2015).
|Risk index||Authors||Risk factors|
Postoperative Failure Risk Index
|Arozullah et al. (2001)|
Postoperative Pneumonia Risk Index
|Arozullah et al. (2001)|
Assess Respiratory Risk in Surgical Patients in Catalonia
|Canet et al. (2010)|
The Guideline Optimal preoperative assessment of the elderly surgical patients (ACS NSQIP/AGS 2012) suggests considering the following as risk factors for PRCs:
age >60, COPD, ASA class II or greater, functional dependence, congestive heart failure, OSA, pulmonary hypertension, cigarette smoking, impaired sensorium, weight loss >10% in 6 months, preoperative sepsis, serum albumin <3.5 mg/dl, blood urea nitrogen >21 mg/dl, serum creatinin >1.5 mg/dl
Advanced age has been consistently identified as a risk factor for PRC (Hua et al. 2012, Alvarez et al. 2015, Yang et al. 2015). Aging is in fact associated with decline in pulmonary reserve, increased V/Q mismatch, diminished hypoxic and hypercapnic ventilator drive, impaired anesthetic metabolism leading to residual effects, and diminished glottic reflexes predisposing to aspiration (see Chapter 1). Moreover, comorbidities predisposing to pulmonary complications have higher prevalence in elderly patients, and include respiratory (asthma, COPD, emphysema, smoking-induced conditions), cardiac (congestive heart failure, arrhythmias) and cognitive conditions (may hamper effective medication intake and inhaler or nebulizer use, see Chapter 3).
In a recent study, PRC in elderly patients accounted for 11% of readmissions to higher-level postoperative care within five days after non-ambulatory orthopedic surgery, resulting in an increased length of hospital stay and treatment costs (Urban et al. 2016). In a prospective multicenter cohort study (Canet et al. 2015) involving 63 hospitals across Europe among 5384 patients scheduled for surgery under both general and regional anesthesia, 4.2% developed PRC. In-hospital mortality was significantly higher in patients with PRC (10.3% vs. 0.4%). Seven independent risk factors were identified by regression analysis: low preoperative oxygen saturation (SpO2), one preoperative respiratory symptom (see above), preoperative chronic liver disease, a history of congestive heart failure, open intrathoracic or upper abdominal surgery, surgical procedure lasting longer than two hours and emergency surgery. Further risk factors identified in retrospective analyses of large datasets are history of smoking, COPD, length of surgery, dependent functional status, preoperative sepsis, preoperative shock, ascites and emergent surgery (Hua et al. 2012, Alvarez et al. 2015, Yang et al. 2015). Obesity, of note, was not a risk factor consistently reported by all researchers (Yang et al. 2015).
The main pillar of preventive strategies is the proactive management of associated respiratory conditions. Other measures are smoking cessation and preoperative intensive inspiratory muscle training (ACS NSQIP/AGS 2012).
Respiratory comorbidites are frequent in the elderly. Preventing PRC in this population is often difficult, particularly in emergency cases, because pulmonary comorbidities may not have been diagnosed before surgery. Moreover, there is often some overlap of symptoms, making diagnosis and treatment difficult without further investigation. Preoperative optimization is effective in reducing the rate of consequent PRC and should be part of routine preoperative preparation for surgery (Sabaté et al. 2014).
Chronic obstructive pulmonary disease (COPD) is a slowly progressive condition, characterized by incomplete reversible airflow obstruction. In patients over 60 years, its prevalence is two to three times higher than in younger adults. Patients with a known history of COPD have a two- to fourfold higher risk of PRC (Arozullah et al. 2001). COPD is associated with an inflammatory response due to inhalation of noxious gases, such as tobacco smoking, fumes or dusts.
COPD has severe consequences, such as pulmonary hypertension, chronic right heart strain and renal insufficiency, that expose patients to a high risk of concomitant postoperative cardiovascular complications (Antonelli-Incalzi et al. 2009, Agusta et al. 2016). Preoperative optimization of COPD is crucial in elective surgery, and involves smoking cessation, physiotherapy, drug therapy optimization and elimination of drug interactions, and training in the use of inhalers and nebulizers. Pharmacological options include inhaled β2-agonists and corticosteroids. As with asthma treatment, a risk of pharyngeal and pulmonary infection, cataract and aggravated osteoporosis have been reported with corticosteroids, especially in elderly patients.
Asthma is often thought of as a disease of childhood and younger adults and is therefore underdiagnosed and undertreated in the elderly. Asthma is an inflammatory disorder and is associated with bronchial hyper-responsiveness and obstruction. In a study involving 199 elderly patients, more than half had a peak expiratory flow rate of less than 70% of predicted; however, only 6% received respiratory-related medication (Banerjee et al. 1987). Its prevalence in this population has been reported to range from 2.8 to 7.1% (Burrows et al. 1991). It is likely, though, that this was underestimated, because elderly people with asthma have often alleviated reactions to stimuli provoking bronchial constriction and such a condition does not always present with the full picture of classical symptoms. A history of recurrent wheezing, tightness felt in the chest, and recurrent episodes of breathlessness, a tendency to atopic symptoms, airway hyper-responsiveness, smoking and living in polluted areas should raise the suspicion of asthma. Once detected, asthma should be verified by pulmonary function tests. Reversibility in response to bronchodilators is often demonstrated.
In the elderly, early-onset and late-onset asthma have been described. Early onset asthma produces fewer clinical symptoms, but responds poorly to bronchodilators and has a more pronounced decrease in lung function (Bellia et al. 1998). Treatment is predominantly based on inhaled β2-agonists. Inhaled corticoids help in limiting the dose of β2-agonists, as they may increase the density of β2-receptors. Corticoids, however, are associated with osteoporosis, dysphagia, and pharyngeal and esophageal mycotic infections. Theophylline should be avoided in the elderly due to the higher risk of fatal arrhythmias, and altered pharmacokinetics in the elderly (Ohnishi et al. 2003).
Obstructive sleep apnea (OSA) belongs to the complex of “sleep-disordered breathing,” which also includes primary snoring, upper airway resistance syndrome, central sleep apnea syndrome, complex sleep-disordered syndrome and sleep-related hypoventilation syndrome, all of which may not be diagnosed at the time of presentation to the anesthetist. The knowledge of these conditions of “central respiratory depression” is crucial for the prevention of postoperative complications, as they are associated with increased pharyngeal collapsibility during sleep and a higher incidence of obstructive events (Young et al. 2002, Kaplan et al. 2002, Eikermann et al. 2007). Even in the healthy elderly, however, respiratory responses to hypercapnia and hypoxia are alleviated due to aging-related central processes (Peterson et al. 1981). It is noteworthy that in a recent study by Chung et al. (2015), at least 18.3% of non-OSA patients developed sleep-disordered breathing (SDB) after surgery. If not diagnosed before hospital admission, symptoms such as daytime sleepiness, loud snoring, choking and poor concentration are indicative of OSA. Accidental falls and car accidents, glaucoma or non-arteritic anterior ischemic optic neuropathy may also give rise to the suspicion of OSA.
The risk of concomitant arterial hypertension, stroke and ischemic heart disease is increased in patients with asthma (Shamsuzzaman et al. 2003). The reported prevalence, generally increasing with higher age, ranges widely from 30 to 80% (Young et al. 2002). A significant association with other cardiovascular comorbidities has been reported (Shamsuzzaman et al. 2003). Treatment uses nocturnal intermittent ventilation with continuous positive airway pressure (CPAP) and weight control.
Preoperative smoking cessation is accompanied by many positive effects, such as improved circulatory function, cough and wheezing reduction, and many others. However, whether it is effective in reducing PRC remains controversial. Early studies reported that patients who quit shortly after surgery had higher complication rates, probably due to increased coughing and sputum production for the first six to eight weeks. A longer preoperative smoking abstinence is probably associated with more benefits, however this result is difficult to obtain. Smoking cessation, nevertheless, is effective, even 12 hours before surgery, since it helps to reduce carbon monoxide levels and improves broncho-tracheal ciliary function (Gracey et al. 1979).
A number of studies, some of which were RCTs, showed that preoperative intensive inspiratory muscle training (IMT) is feasible and contributes in reducing pre- and postoperative atelectasis, inspiratory muscle strength and vital capacity before different abdominal and thoracic surgical procedures. The PRC rate is also reduced. These findings were recently confirmed by a large review on the Cochrane Database (Katsura et al. 2015). IMT is part of preoperative respiratory prehabilitation (see Chapter 12).
General anesthesia leads to alveolar collapse and possible atelectasis due to a number of mechanisms (gas reabsorption, surfactant dysfunction and lung compression), especially during long-lasting or laparoscopic procedures. In recent years, the concept of protective ventilation (lower tidal volume, higher PEEP levels and routine use of recruitment maneuvres) has been defined with the aim of translating improvements in ventilation strategies that were achieved in the ICU into the operating room (Ball et al. 2016). A recent review extended over a wide time interval concluded that low tidal volumes defined as <10 ml/kg should be used preferentially, as they decrease the need for postoperative (invasive and non-invasive) ventilator support. No recommendations were made concerning an appropriate maximum peak pressure of ventilation during surgery (Guay and Ochron 2015). However, the trials reviewed were not conducted exclusively in a geriatric population.
Although protective against peripheral oxygen desaturation, the use of high FiO2 at induction has been found to be associated with contradictory results. In one study it was found to be associated with increased risk of intraoperative atelectasis (Hedenstierna and Edmark 2015), whereas another study found the opposite (Edmark et al. 2014). The clinical relevance of this finding in the elderly population remains to be clarified.
Several anesthetic drugs with potentially respiratory depressant effects have a prolonged effect in elderly patients (see Chapter 19). Lipophilic drugs, including volatile anesthetics, long-acting opioids, barbiturates and propofol, all aggregate in the third compartment and have a longer half-life due to prolonged redistribution. Hypoalbuminemia is common in the elderly, whereas α1-acid glycoprotein plasma concentration is almost unaffected with higher age (Veering et al. 1990). Acidic substances tend to bind to albumin, basic substances prefer to bind to α1-acid glycoprotein. Plasma cholinesterase is decreased in the elderly, and even more decreased in frail than in healthy subjects (Hubbard et al. 2008). Opioid dosage has to be adapted, since they show higher potency in the elderly, possibly due to enhanced µ-opoid receptor sensitivity (Coldrey et al. 2011). The action of volatiles is prolonged due to higher distribution volume (Strum et al. 1991) and their minimum alveolar concentration (MAC) is reduced in elderly patients. Mainly due to altered pharmacokinetics, elderly patients are highly sensitive to muscle relaxants. The incidence of postoperative residual curarization (PORC, see Chapter 19) was higher in a prospective study of 150 elderly patients (58% compared with 30% in the younger group), and associated with more frequent hypoxemia, overall postoperative pulmonary complications and longer hospital length of stay.
Unintended overdosing, aggravating the risk of persistent pharmacological effects, should be prevented with processed electroencephalographic and neuromuscular blockade monitoring.
Several factors impact on lung function postoperatively: reduced chest and abdominal mobility (mostly after abdominal and thoracic surgery), decreased secretion clearance due to less effective cough, pain and bed-rest. Atelectasis, respiratory failure and pneumonia are the most common PRCs. The care team should implement routine strategies for their prevention in the older patient.
Postoperative pain treatment is of paramount importance in reducing pain-related hypoventilation, although opioids have respiratory depressant action and should be carefully administered. When applicable, epidural analgesia offers advantages both as an alternative to or integrated with general anesthesia, and can also be exploited as a postoperative analgetic treatment.
Measures to prevent aspiration are indicated in all older patients and are mandatory in those with signs, symptoms or history of dysphagia; the head of bed should be elevated at all times, patients should be solicited to take meals out of bed when possible, or to sit upright while eating. A sitting position should be maintained for one hour after every meal.
In accordance with the ERAS principles (see Chapter 34), early mobilization should be promoted as much as possible. The use of an incentive spirometer, deep breathing exercises and chest physical therapy are effective in preventing atelectasis. Physiotherapy should be preoperatively planned and patients should be instructed on it, with the aim of obtaining maximum cooperation. Patients should be encouraged to cough and breathe deeply. Nebulized bronchodilators and humidity may help in making secretions more fluid and easier to remove. N-acetylcysteine aerosol (used as fluidizer) may cause acute bronchoconstriction.
Postoperative atelectasis requires adequate oxygenation (ideally titrated to achieve an SpO2 >90%, more realistically an SpO2 value near to that observed preoperatively) and re-expansion of the collapsed segment. Chest X-ray may help in determining whether the obstruction is proximal or distal. In cases of lobar atelectasis, vigorous chest FKT (postural drainage, chest wall percussion and vibration and forced expiration) may help in re-expanding collapsed areas. If these measures are not effective within 24 hours, fiberoptic bronchoscopy should be performed to remove the mucous plugging. Promoting increased drainage in the affected area by patient positioning (postural drainage), vigorous chest FKT and encouraging the patient to cough helps in preventing further atelectasis. In those who are not able to cough vigorously, naso-tracheal suctioning may be required.
Continuous positive airway pressure (CPAP) delivered via nasal cannula or facemask and non-invasive ventilation (NIV) via facemask or helmet improve oxygenation and help in re-expanding the collapsed lung. These methods have been shown to reduce the rate of postoperative pulmonary infection and the need for tracheal intubation and ICU admission.
Sputum examination allows a targeted antibiotic treatment in cases of specific pathogen isolation. Fever, night sweats and leukocytosis suggest that atelectasis has become infected; however, infections in the elderly often occur in atypical forms and pathognomonic signs can be absent.