(BQ) Part 2 book Mechanical ventilation in critically ill cancer patients has contents: Postoperative mechanical ventilation, withdrawal from mechanical ventilation support, palliative ventilatory support in cancer critical care,... and other cotents.
Part III Postoperative Mechanical Ventilation General Postoperative Complications 21 Gulsah Karaoren Abbreviations ADH ASA COPD DTR OSAS PONV TUR Antidiuretic hormone American Society of Anesthesiologists Chronic obstructive pulmonary disease Deep tendon reflexes Obstructive sleep apnea Postoperative nausea and vomiting Transuretheral resection 21.1 Introduction In patients undergoing anesthesia, it has been suggested that postoperative complications develop in approximately 25% of cases, although the actual rates cannot be verified as no consensus on definitions has been reached The complication rate varies according to the surgery applied, the anesthesia technique, and preexisting comorbidities Further treatment may be required for postoperative complications and hospital discharge may be delayed With correct perioperative evaluation, risks can be minimized and medical treatment can be optimized, with early identification saving lives, time, and money Patients with suspected complications must be questioned as to what type of surgery has been applied and for what purpose, if they have any comorbidities and what medication is being used, and what applications have been made since the onset of the suspected complication [1] G Karaoren, M.D Anesthesiology and Reanimation, Istanbul Umraniye Research Hospital, Istanbul, Turkey e-mail: drgyilmaz@yahoo.com © Springer International Publishing AG 2018 A.M Esquinas et al (eds.), Mechanical Ventilation in Critically Ill Cancer Patients, https://doi.org/10.1007/978-3-319-49256-8_21 213 214 G Karaoren A total incidence of 23% postoperative complications was determined in a retrospective review of 18,473 patients Postoperative nausea and vomiting (PONV) at reported rates of 10–30% was determined to be the most common postoperative complication, followed by upper airway problems (6.9%), hypotension (2.7%), dysrhythmias (1.4%), hypertension (1.1%), altered mental status (0.6%), and suspected or major cardiac events (0.6%) [2] The ability to preoperatively predict complications which may develop is important in respect of preventative measures However, even if it is known that a complication may develop, some patient-related risk factors, such as age, cannot be eliminated In a previous study it was shown that the 37 risk factors determined in the preoperative period that were related to postoperative mortality were effective in only 12% of deaths and thus it was reported that the effect of postoperative care was just as important as the preoperative factors [3] There are various ways to approach the management of postoperative complications, the most practical of which is to consider the frequency of different complications (Table 21.1) Table 21.1 General postoperative complications Postoperative cardiovascular complications Postoperative pulmonary complications Renal complications Postoperative hypotension Hypovolemia Ventricular dysfunction Postoperative hypertension Myocardial ischemia Cardiac dysrhythmias Bradycardia Tachycardia Premature contractions Hypoxemia Hypoventilation Increased airway resistance Laryingospasm Bronchospasm Reduced compliance Neuromuscular and skeletal problems Impaired oxygen exchange Intrapulmonary shunting Pulmonary embolism Pulmoner edema Pneumonia Atelectasis Aspiration Anemia Urinary retention Oliguria Polyuria 21 General Postoperative Complications 215 Table 21.1 (continued) Fluid electrolyte disorders: Pain Postoperative nausea/vomiting Hypothermia/shivering Fever Neuropsychiatric complications Hyponatremia, Hyperkalemia, Hypokalemia, Hypocalcemia, Hypermagnesemia Delirium Prolonged sedation Visual disturbance Reduced bowel function Pressure sores and peripheral nerve damage 21.2 General Postoperative Complications 21.2.1 Postoperative Cardiovascular Complications The cardiovascular complications which may develop postoperatively include hypotension, hypertension, cardiac dysrhythmias, cardiac ischemia, and infarct A 2012 study of vascular complications in non-cardiac surgery patients (VISION) demonstrated that patients with cTp-I levels ≥0.02 ng mL had an increased risk of postoperative death [4] Therefore, there should be immediate investigation of any new cardiovascular change, including angina or dysrhythmias 21.2.1.1 Postoperative Hypotension Hypoperfusion of vital organs and systems can be caused by the common postoperative complication of systemic hypotension This generally occurs because of hypovolemia, arterial hypoxemia, reduced myocardial contractility, reduced systemic vascular resistance (neuraxial anesthesia, sepsis), cardiac arrhythmia, pulmonary emboli, pneumothorax or cardiac tamponade Inefficient anabolic metabolism is promoted by tissue hypoxia and lactic acid accumulation may result in unexplained metabolic acidemia A decrease in the venous flow rate increases the risk of deep vein thrombosis and pulmonary embolism The risk of systemic hypotension has been determined to be high in patients with atherosclerotic heart disease and those with chronic hypertension and elevated intracranial pressure with stenotic vascular diseases (a) Hypovolemia: Hypotension is the most common cause Ventricular filling and cardiac output are decreased by a reduction of >15–20% of circulating intravascular volume Unnoticed haemorrhage and third space losses can exacerbate hypovolemia Postoperative severe pain or vasovagal responses may cause an increase in venous capacity with the activation of the sympathetic system In patients applied with mechanical ventilation, compression of thoracic veins and reduced venous return associated with positive intrathoracic pressure is another effect 216 G Karaoren (b) Ventricular dysfunction: This is generally seen in patients with known cardiac disorders These patients often have increased left ventricle end diastolic pressure and increased sympathetic activity with sufficient cardiac output However, fluid accumulation in these patients may cause ventricular dilatation, reduced cardiac output, hypotension, and frequently hydrostatic pulmonary edema Deep acidosis and reduced blood ionized Ca can reduce ventricular contractility Right ventricle dysfunction, which may be seen associated with pulmonary thromboembolism, often presents with systemic hypotension 21.2.1.2 Postoperative Hypertension A slight increase in blood pressure is expected in the postoperative period, but when there is an increase of 20–30% compared to the baseline value of systolic or diastolic pressure, this may cause headache, bleeding, third space losses, cardiac ischemia or dysrhythmias Generally, when there is known hypertensive disease, anxiety, pain, stomach, and bladder distension, hypervolemia, hypoxemia, and increased intracranial pressure are observed 21.2.1.3 Myocardial Ischemia Postoperative myocardial ischemia is often determined in patients with coronary disease and congestive heart failure, a history of smoking and hypertension and in those who have undergone emergency surgery Tachycardia associated with postoperative pain, hypotension, acidemia, anxiety, and some medications may lead to ischemia by shortening the diastolic filling time Insufficient diastolic blood pressure is a cause of ischemia Anginal chest pain, which is the most important symptom, may be suppressed by incision pain, gastric distension, or the residual effect of anesthetics or narcotic analgesics and the risk of morbidity in the early period for these patients is extremely high 21.2.1.4 Cardiac Dysrythmias Arterial hypoxemia, hypercarbia, hypovolemia, hypothermia, pain, electrolyte and acid base imbalance, myocardial ischemia, elevated intracranial pressure, drug toxicity (digoxin), and anticholinesterase medication seen in the postoperative period may cause the formation of cardiac dysrhythmia However, axis, intraventricular conduction, p-t wave morphology, and ST segment alterations seen on ECG in the early period associated with the application of general anesthesia are not accepted as cardiac dysrhythmia These changes which cause an imbalance in hypotherthermia, inhalation agents, and the autonomous nerve system and a mild electrolyte imbalance are electrophysiological effects which spontaneously correct within 3–6 h If these changes persist, cardiac ischemia must be considered and by providing oxygen support together with monitorization of the patient, serial ECG and enzyme monitorization must be applied The most commonly encountered dysrhythmias are bradycardia, tachycardia, and premature contractions (a) Bradycardia: In the postoperative period, increased parasympathetic nervous system activity and the reduced sympathetic nervous system effect promote sinus bradycardia Sick sinus syndrome, ischemia, and hypoxemia reduce the 21 General Postoperative Complications 217 sinus rate in sinoatrial node Bradycardia is generally harmless but when heart rate falls below 40–45 bpm, this may cause hypotension (b) Tachycardia: Postoperative sinus tachycardia is generally harmless, but in cases of coronary artery disease may cause myocardial ischemia Tachycardia may exacerbate hypertension and acidosis and hypoxemia may be markers It is generally corrected with treatment of the underlying cause such as pain management, hydration, and voiding of a full bladder Following thoracic surgical procedures, if ventricle rate exceeds 150 in patients with mitral valve disease or pulmonary embolism, rapid ventricular response atrial fibrillation may develop Ventricular filling and cardiac output reduce at a high rate and may be a cause of hypotension Atrial flutter, paroxysmal atrial tachycardia, and re-entry rhythms are rarely seen postoperatively in patients Postoperative ventricular tachycardia or fibrillation is encountered in severe myocardial ischemia, systemic acidemia or hypoxemia (c) Premature contractions: Atrial premature contractions seen in the postoperative patient are generally caused by sympathetic system activation Premature ventricular contractions usually have a benign course However, when there is high amplitude, wide or bizarre QRS complexes, damage is seen in ventricular communication 21.2.2 Postoperative Pulmonary Complications The vast majority of complications which occur after surgery comprise pulmonary complications formed as a result of respiratory muscle dysfunction and impaired chest wall mechanics These complications are a significant cause of postoperative morbidity and )mortality, prolong hospital stay, and increase costs In a study of patients in which postoperative pulmonary complications developed, the likelihood of mortality was shown to be increased 14.9-fold compared to patients who did not develop those complications [1, 5] The most important risk factors are smoking, obesity, obstructive sleep apnea syndrome (OSAS), severe asthma and chronic obstructive pulmonary disease (COPD), steroid use and thoracic-upper abdominal surgery In clinical practice, microatelectasis-related fever, cough, dyspnea, bronchospasm, hypoxemia, hypercapnia, aspiration, atelectasis, pneumonia, pulmonary edema, acute respiratory distress syndrome, pulmonary embolism, and pleural effusion are the most commonly encountered complications and may cause acute respiratory failure in patients [5] 21.2.2.1 Hypoxemia Intrapulmonary shunts which form secondary to reduced functional residual capacity are the basis of postoperative hypoxemia Other causes are ventilation perfusion imbalance, reduced cardiac flow, alveolar hypoventilation, obstruction of the upper airway, bronchospasm, gastric aspiration, pulmonary edema, pulmonary embolism, pneumothorax, obesity, and senility Pain, abdominal distension, diaphragm dysfunction, and a supine position worsen this condition Hypoxemia in the 218 G Karaoren postoperative period can be easily and quickly diagnosed with pulse oxymetry Hypoxemia findings are nonspecific and may be confused with hypercapnea In the early stage, tachycardia, tachypnea, hypertension, hypotension, agitation, and changes in mental status may be observed In the late stage, there may be hypotension, bradycardia, and cardiac arrest 21.2.2.2 Hypoventilation The most common causes are the residual depressant effects on hypoxic drive of anesthetic agents and insufficient neuromuscular blockage antagonism Insufficient analgesia and bronchospasm are other causes Increased PaCO2 alone in the postoperative period is not an indicator of hypoventilation To be able to be defined as hypoventilation, there must be tachypnea, anxiety, dyspnea, and increased sympathetic system activation together with respiratory acidosis (pH 0.4–1.0 mL/ kg and