- Email: [email protected]
Rescue Therapies in the Surgical Patient
Rescue Therapies in the Surgical Patient Samuel A. Tisherman,
MD
a,b,
*
KEYWORDS Acute respiratory failure Extracorporeal life support Cardiac arrest Therapeutic hypothermia Stroke
Because of the significant physiologic changes that occur as a result of major operations, general anesthesia, and comorbid conditions, surgical patients are at high risk of developing acute complications. Patients can suddenly experience hypoxemia, shortness of breath, dysrhythmia, or hypotension. They may suddenly develop neurologic changes, including seizures. Clinicians need to be aware of the potential critical events that can occur in the perioperative period and be prepared to intervene in an expeditious and a potentially lifesaving manner. MEDICAL EMERGENCY TEAMS
To rapidly respond to critical events in the hospital, medical emergency teams (METs) or rapid response teams (RRTs) have been developed.1 The terminology is sometimes interchangeable, although some recommend using the latter term for teams that do not provide complete intensive care unit (ICU) level of care. Although the initial evaluation of a serious adverse event may suggest that it was acute in nature, frequently there are warning signs to suggest pending physiologic instability. Patient safety initiatives have focused on establishing a hospital culture in which all health care providers feel empowered to call for an MET or RRT any time they suspect significant changes in patient physiology. It has been difficult to consistently demonstrate improved outcomes from the use of METs, but there seems to be some benefit in preventing more serious events such as death after myocardial infarction.2 When organizing a rapid response system, a medical emergency needs to be defined first. One definition is when a patient’s needs cannot be met by the resources available in the patient’s current location. The specific needs vary but may include
Disclosure: Dr Tisherman is the coauthor of a patent entitled, “Emergency Preservation and Resuscitation Methods.” a Department of Critical Care Medicine, University of Pittsburgh, 638 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA b Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA * Department of Critical Care Medicine, University of Pittsburgh, 638 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261. E-mail address: [email protected] Surg Clin N Am 92 (2012) 433–439 doi:10.1016/j.suc.2012.01.007 surgical.theclinics.com 0039-6109/12/$ – see front matter Ó 2012 Elsevier Inc. All rights reserved.
434
Tisherman
specific personnel or equipment as well as a specific frequency of observation. It is critical to define criteria that would trigger initiation of the rapid response. These criteria need to be well publicized within the system. The use of additional technological monitoring with appropriate alarms can certainly help in reducing the time lag between warning signs of an event and activation of the rescue team. In a surgical patient, the most common changes that should trigger a response include respiratory distress, hypoxemia, and hypotension. The exact conduct and personnel involved in METs vary between institutions. The team should include the personnel and resources to provide airway management, vascular access, medication administration, and cardiac arrest resuscitation. Ideally, METs should be led by physicians with critical care training, although this optimum membership may be difficult to meet in all settings. The team should be able to provide a level of care similar to that in the ICU in any location within the hospital, at least for a brief period. Rapid triage of the patient to an appropriate location within the hospital should allow ongoing, optimal, and timely care. It is not infrequent, however, that METs require the expertise of specific physicians or services not part of the original response team. In some institutions, this need has been met by developing additional subspecialty teams that can be rapidly deployed to provide a specific service. One such example is a difficult or threatened airway team. A difficult airway team might include an anesthesiologist, as presumably, the most able airway manager in the hospital; a surgeon skilled in emergency surgical airway techniques (eg, cricothyrotomy); and advanced airway management devices (eg, video laryngoscopy). A chest pain team might include high-level cardiology personnel who could rapidly assess the need for, and then facilitate, percutaneous coronary intervention. Similarly, a stroke team might include high-level neurology personnel who could rapidly evaluate an individual with a presumed stroke for potential lytic therapy or intravascular therapies, within the recommended time windows. These are all examples of serious adverse events that can occur in the perioperative period for which timely intervention by skilled specialists is critical. RESPIRATORY EVENTS
Respiratory complications are common in surgical patients. Examples include pneumonia, aspiration pneumonia or pneumonitis, atelectasis from mucous plugging, and pulmonary embolism. Patients who underwent major surgical procedures and have significant comorbid conditions may have little physiologic reserve, allowing minor physiologic perturbations to cause life-threatening events very quickly. Because hypoxemia or inadequate ventilation (hypercarbia) can rapidly lead to metabolic acidosis and deterioration in the patient’s physiology and, possibly, cardiac arrest, these are frequent indications for an MET response. Airway management is the first priority. Most of the time, rapid institution of standard ICU management strategies suffice if tracheal intubation is needed. Relatively simple changes in technique, such as optimizing patient positioning, bimanual manipulation of the larynx with pressure on the tracheal cartilage (backward, upward, right, and posterior pressure), and choice of laryngoscope blade or appropriately sized endotracheal tube, can make a significant difference in successfully intubating the airway. Sometimes, specific rescue therapies are indicated. For patients with a difficult airway,3 the ability to apply rescue therapies within minutes is essential, which is why difficult airway teams are sometimes deployed. Recognition of the potential for, or existence of, a difficult airway is critical. Once recognized, the first step in management is to have the most experienced airway
Rescue Therapies in the Surgical Patient
manager available, typically an anesthesiologist or a senior nurse anesthesiologist. The second step is to provide the airway manager with all the tools that might be necessary to secure the airway. A variety of laryngoscope blades and endotracheal tube sizes can be very helpful. For a patient who needs ventilatory assistance but for whom bag-valve-mask ventilation is ineffective, rescue devices might include the laryngeal mask airway or esophageal-tracheal devices such as the Combitube (Covidien, Boulder, CO, USA) or King Airway (King Systems, Noblesville, IN, USA). Rescue devices that assist in placing an endotracheal tube include a gum elastic bougie and video laryngoscope or bronchoscope. The third step is to have an expert available during placement of a surgical airway, typically a cricothyrotomy. The expert may be a senior surgical resident or an attending surgeon. The availability of such a person is critical for the management of a dislodged tracheostomy tube in a patient with a difficult airway. Deployment of a difficult airway team can decrease the need for an emergency surgical airway.4 Once the airway has been secured, patients may still have difficulty with oxygenation or ventilation despite administration of high levels of oxygen and increasing levels of airway pressure. Of utmost concern in this situation is the development of acute respiratory distress syndrome or preceding acute lung injury. Although there are no rescue therapies that have been proved to improve outcomes in these circumstances, several approaches have been used.5 Ventilation with pressure-controlled modes can sometimes improve pulmonary recruitment, while deleteriously limiting high peak, mean, and plateau airway pressures. Increasing the inspiratory to expiratory (I:E) ratio can further recruit alveoli. This approach has been taken to the extreme with airway pressure release ventilation, a modified form of continuous positive airway pressure that does not use traditional cyclic ventilation and, therefore, does not have a typical I:E ratio. More extraordinary is the use of high-frequency ventilation, which has taken many forms, including highfrequency positive pressure ventilation, high-frequency jet ventilation, and highfrequency oscillatory ventilation. These modes provide relatively constant mean airway pressure with very rapid shallow breaths, which may minimize ventilatorinduced lung injury. This mode may be most useful during operative interventions on the airway or in patients with bronchopulmonary fistulas because it is generally accompanied by carbon dioxide (CO2) retention, respiratory acidosis, and deep sedation of neuromuscular blockade to enable patient tolerance of the mode. A separate approach to improving oxygenation is using inhaled nitric oxide (iNO). The desired physiologic effect of iNO is to cause local vasodilatation in lung zones that have the best ventilation, thus improving ventilation/perfusion matching, particularly in patients with pulmonary hypertension. Because of the extremely short half-life of iNO once in contact with hemoglobin, there are minimal systemic effects. To date, although improvements in oxygenation may be realized, no durable improvements in patient survival, ventilator-free days, or ICU length of stay have been achieved. Ventilation/perfusion matching can also be improved with prone positioning, taking advantage of gravitational forces. When the patient is initially placed prone, blood flow increases to the well-recruited lung segments while the previously atelectatic/dependent lung segments are recruited. Routine shifting from supine to prone and back is then instituted. Care must be taken when placing a patient in this position to avoid the development of pressure injuries and tube dislodgement. Not all patients respond to prone positioning, and there is no consensus regarding the duration of prone positioning, the number of times per day a patient should be in the prone position, or the number of days for which prone positioning should be continued. Moreover, no
435
436
Tisherman
improvement in outcome has been ascribed to prone positioning, relegating it to an adjunctive role in rescuing a patient from hypoxemic respiratory failure. For patients with severe pulmonary disease localized to one lung, such as pneumonia, pulmonary contusion, or single-lung transplant, body positioning, with the good lung dependent, may improve blood flow to a well-ventilated lung while increasing recruitment of the diseased lung. Care should be taken to avoid soiling the good lung when the infected lung is placed in the nondependent position. In this circumstance, placement of a double-lumen endotracheal tube may allow differential ventilation of the lungs (ie, simultaneous independent lung ventilation) to optimize recruitment of the diseased lung while protecting the healthy lung. Extracorporeal membrane oxygenation (ECMO) is perhaps the most risky and laborintensive technique for improving oxygenation in a patient with refractory hypoxemia. ECMO involves venovenous or venoarterial cannulation, a pump, and an oxygenator to allow oxygenation of the blood and CO2 removal. This technique has become the standard in the neonatal population. In adults, using ECMO has become more common with improved systems and experience, most recently with outbreaks of H1N1 influenza. Given the complexity of managing patients on ECMO, this intervention is best reserved for institutions with sufficient experience. Although these rescue therapies may improve oxygenation in many patients with refractory hypoxemia, no mortality benefit has been demonstrated. Still, these therapies may be appropriate in selected patients. CARDIAC EVENTS
Hypotension is a common perioperative complication. Multiple causes of shock need to be considered, including hypovolemia, sepsis, pulmonary embolism, and an acute coronary syndrome.6 While completing diagnostic studies to determine the cause, the initial management includes ensuring adequate plasma volume resuscitation, supporting cardiac function with inotropes as needed, and judicious use of vasopressors. Specific causes of hypotension may require specific rescue therapies when the initial management is insufficient. If the patient is hypovolemic, the first concern is bleeding. In addition to fluid and blood resuscitation, this condition may necessitate surgical intervention or perhaps embolization by interventional radiology. Coagulopathy (warfarin anticoagulation) including therapeutically induced platelet dysfunction (aspirin, clopidrogel) should be concomitantly addressed. A massive transfusion protocol that is jointly developed with transfusion medicine may be lifesaving in those with massive gastrointestinal tract hemorrhage, postoperative hemorrhage, or iatrogenically induced blood loss (eg, torn iliac vein during sheath introducer insertion). Septic patients often require initial plasma volume resuscitation. Vasopressors should be added only when the patient remains hypotensive despite fluid resuscitation. Adequate cardiac performance should be ensured. Controlling the source of sepsis is critical. Although there is plenty of controversy, there may be a role for steroids in patients with absolute or relative adrenal insufficiency.7 Activated protein C has been recently withdrawn from the market because of lack of efficacy. Surgical patients are at high risk of pulmonary embolism because of hypercoagulable states, immobility, and vessel trauma. Diagnosis of pulmonary embolism in an unstable patient may be difficult. Bedside echocardiography can be helpful in these circumstances if it demonstrates right ventricular hypokinesia, asymmetric dilatation of the right ventricle versus the left ventricle, or strain. In addition to standard anticoagulation, rescue therapies for patients who remain hypotensive due to massive
Rescue Therapies in the Surgical Patient
pulmonary embolism include intravenous thrombolytic therapy (there is no evidence that catheter-directed therapy is more effective or safer), catheter embolectomy, or operative embolectomy.8 These therapies carry significant risks but may be lifesaving. Acute coronary syndrome occurs in the perioperative period because of stress and, possibly, hypercoagulable states. Often, the issue is demand ischemia (eg, from hypoxemia or hypotension) in a patient with fixed coronary atherosclerotic disease. Rapid correction of the underlying process, plus beta-blockade if possible, is the main strategy for management in such circumstances. Occasionally, however, acute coronary occlusion occurs in the perioperative period. Standard management for an acute myocardial infarction, including the administration of oxygen, aspirin, betablockade, and anticoagulation, is indicated unless there is a significant contraindication. Therapies aimed at rapid revascularization should also be used if possible. However, based on the perceived risk of hemorrhage in the perioperative period, the use of lytic therapy is too risky in the immediate perioperative period. Cardiac catheterization, although the patient may still require antiplatelet therapy after stent placement, may be indicated. In many hospitals, a system is in place for rapid mobilization of the cardiology team to minimize the event-to-balloon time.9 If patients develop profound cardiac dysfunction despite maximum medical therapy, mechanical circulatory support with an intra-aortic balloon pump in the short term, or a ventricular assist device for long-term support, may be necessary. Patients may also suffer a cardiac arrest in the perioperative period. Traditionally, code teams respond to these events. Although, intuitively, use of METs decreases the incidence of cardiac arrests and/or improves outcomes, this has been difficult to prove.10 Sudden events leading to cardiac arrest include pulmonary embolism and myocardial infarction. In addition, cardiac arrest may be the end result of deterioration because of multiple organ dysfunction, sepsis, or hemorrhage and may not be reversible. When sudden cardiac arrest occurs, standard advanced cardiac life support therapies should be initiated. Frequently, spontaneous circulation cannot be restored. Those who regain a pulse, however, may not rapidly recover neurologic function.11 Randomized clinical trials in comatose survivors of out-of-hospital cardiac arrest with initial rhythms of ventricular fibrillation (VF)/ventricular tachycardia (VT) demonstrated improved neurologic outcomes and survival with therapeutic hypothermia. The American Heart Association now recommends that comatose survivors of out-of-hospital VF/VT be cooled to 32 C to 34 C for 12 to 24 hours. Therapeutic hypothermia should be considered for patients who suffer a cardiac arrest in hospital and for patients with other initial rhythms. Unless there is a clear contraindication, surgical patients should be treated similarly. Postcardiac arrest care has, until recently, received little direct attention. It seems clear, however, that optimizing management could readily affect outcomes. To this end, the primary cause of cardiac arrest should be addressed rapidly with, for example, cardiac catheterization for coronary occlusion or thrombolytic therapy for acute pulmonary embolism. In addition, appropriate blood pressure and glucose control are recommended. Neurologic evaluation and prognostication, as well as referral for rehabilitation, are needed. Some institutions have organized teams to assist in the management of patients after cardiac arrest. NEUROLOGIC EVENTS
Critically ill surgical patients frequently develop delirium in the perioperative period. This may be associated with medications (new agents or failure to continue existing agents), alcohol withdrawal, sepsis, and exacerbation of underlying comorbidities.
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Optimal therapy for the delirious patient remains unclear. Therefore, strategies to prevent delirium, such as judicious use of sedatives and analgesics in patients at risk, optimizing environmental factors, and rapidly treating perioperative complications, should have a greater impact. Without focal findings on examination, computed tomography (CT) or magnetic resonance imaging of the head is rarely helpful. More severe neurologic events, particularly stroke, can occur in the perioperative period.12 Any patient who has a new focal neurologic deficit should undergo a stat CT of the head. If an ischemic stroke is suspected, administration of tissue plasminogen activator (tPA) should be considered if standard criteria are met and tPA use is not contraindicated. Some institutions have a designated stroke service that is prepared to quickly evaluate such patients. Urgent angiographic evaluation with possible stent placement is a new therapy that is used in some situations, particularly in patients for whom thrombolytic therapy is contraindicated, although these therapies are not mutually exclusive in select patients. It is clear that the more rapidly tissue oxygen delivery is re-established, the better is the postevent neurologic outcome. SUMMARY
Critical events are common in the perioperative period. Rapid identification of patient deterioration and rapid deployment of a team prepared to manage the patient’s condition may affect morbidity and mortality. When necessary, rescue therapies should be used for airway management, ventilatory and cardiovascular support, and severe neurologic deficits. Use of these rescue therapies may improve patient outcomes. REFERENCES
1. DeVita MA, Bellomo R, Hillman K, et al. Findings of the first consensus conference on medical emergency teams. Crit Care Med 2006;34:2463–78. 2. Chen J, Bellomo R, Flabouris A, et al. The relationship between early emergency team calls and serious adverse events. Crit Care Med 2009;37:148–53. 3. Lavery GG, McCloskey BV. The difficult airway in adult critical care. Crit Care Med 2008;36:2163–73. 4. Berkow LC, Greenberg RS, Kan KH, et al. Need for emergency surgical airway reduced by a comprehensive difficult airway program. Anesth Analg 2009; 109(6):1860–9. 5. Pipeling MR, Fan E. Therapies for refractory hypoxemia in acute respiratory distress syndrome. JAMA 2010;304(22):2521–7. 6. Cheatham ML, Block EF, Promes JT, et al. Shock: an overview. In: Irwin R, Rippe J, editors. Irwin and Rippe’s intensive care medicine. 6th edition. Philadelphia: Lippincott Williams & Wilkins; 2008. p. 1831–42. 7. Bernard GR, Vincent JL, Laterre PF, et al. Recombinant Human Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) Study Group. Efficacy and safety of recombinant human activated protein C for severe sepsis. N Engl J Med 2001; 344(10):699–709. 8. Jaff MR, McMurtry MS, Archer SL, et al. Management of massive and submassive pulmonary embolism, iliofemoral deep vein thrombosis, and chronic thromboembolic pulmonary hypertension: a scientific statement from the American Heart Association. Circulation 2011;123:1788–830. 9. Nallamothu BK, Bradley EH, Krumholz HM. Time to treatment in primary percutaneous coronary intervention. N Engl J Med 2007;357:1631–8. 10. Hillman K, Chen J, Cretikos M, et al. Introduction of the medical emergency team (MET) system: a cluster-randomised controlled trial. Lancet 2005;365:2091–7.
Rescue Therapies in the Surgical Patient
11. Peberdy MA, Callaway CW, Neumar RW, et al. Part 9: post-cardiac arrest care: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122:S768–86. 12. Lukovits TG, Goddeau RP. Critical care of patients with acute ischemic and hemorrhagic stroke: update on recent evidence and international guidelines. Chest 2011;139(3):694–700.
439
MD
a,b,
*
KEYWORDS Acute respiratory failure Extracorporeal life support Cardiac arrest Therapeutic hypothermia Stroke
Because of the significant physiologic changes that occur as a result of major operations, general anesthesia, and comorbid conditions, surgical patients are at high risk of developing acute complications. Patients can suddenly experience hypoxemia, shortness of breath, dysrhythmia, or hypotension. They may suddenly develop neurologic changes, including seizures. Clinicians need to be aware of the potential critical events that can occur in the perioperative period and be prepared to intervene in an expeditious and a potentially lifesaving manner. MEDICAL EMERGENCY TEAMS
To rapidly respond to critical events in the hospital, medical emergency teams (METs) or rapid response teams (RRTs) have been developed.1 The terminology is sometimes interchangeable, although some recommend using the latter term for teams that do not provide complete intensive care unit (ICU) level of care. Although the initial evaluation of a serious adverse event may suggest that it was acute in nature, frequently there are warning signs to suggest pending physiologic instability. Patient safety initiatives have focused on establishing a hospital culture in which all health care providers feel empowered to call for an MET or RRT any time they suspect significant changes in patient physiology. It has been difficult to consistently demonstrate improved outcomes from the use of METs, but there seems to be some benefit in preventing more serious events such as death after myocardial infarction.2 When organizing a rapid response system, a medical emergency needs to be defined first. One definition is when a patient’s needs cannot be met by the resources available in the patient’s current location. The specific needs vary but may include
Disclosure: Dr Tisherman is the coauthor of a patent entitled, “Emergency Preservation and Resuscitation Methods.” a Department of Critical Care Medicine, University of Pittsburgh, 638 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA b Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA * Department of Critical Care Medicine, University of Pittsburgh, 638 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261. E-mail address: [email protected] Surg Clin N Am 92 (2012) 433–439 doi:10.1016/j.suc.2012.01.007 surgical.theclinics.com 0039-6109/12/$ – see front matter Ó 2012 Elsevier Inc. All rights reserved.
434
Tisherman
specific personnel or equipment as well as a specific frequency of observation. It is critical to define criteria that would trigger initiation of the rapid response. These criteria need to be well publicized within the system. The use of additional technological monitoring with appropriate alarms can certainly help in reducing the time lag between warning signs of an event and activation of the rescue team. In a surgical patient, the most common changes that should trigger a response include respiratory distress, hypoxemia, and hypotension. The exact conduct and personnel involved in METs vary between institutions. The team should include the personnel and resources to provide airway management, vascular access, medication administration, and cardiac arrest resuscitation. Ideally, METs should be led by physicians with critical care training, although this optimum membership may be difficult to meet in all settings. The team should be able to provide a level of care similar to that in the ICU in any location within the hospital, at least for a brief period. Rapid triage of the patient to an appropriate location within the hospital should allow ongoing, optimal, and timely care. It is not infrequent, however, that METs require the expertise of specific physicians or services not part of the original response team. In some institutions, this need has been met by developing additional subspecialty teams that can be rapidly deployed to provide a specific service. One such example is a difficult or threatened airway team. A difficult airway team might include an anesthesiologist, as presumably, the most able airway manager in the hospital; a surgeon skilled in emergency surgical airway techniques (eg, cricothyrotomy); and advanced airway management devices (eg, video laryngoscopy). A chest pain team might include high-level cardiology personnel who could rapidly assess the need for, and then facilitate, percutaneous coronary intervention. Similarly, a stroke team might include high-level neurology personnel who could rapidly evaluate an individual with a presumed stroke for potential lytic therapy or intravascular therapies, within the recommended time windows. These are all examples of serious adverse events that can occur in the perioperative period for which timely intervention by skilled specialists is critical. RESPIRATORY EVENTS
Respiratory complications are common in surgical patients. Examples include pneumonia, aspiration pneumonia or pneumonitis, atelectasis from mucous plugging, and pulmonary embolism. Patients who underwent major surgical procedures and have significant comorbid conditions may have little physiologic reserve, allowing minor physiologic perturbations to cause life-threatening events very quickly. Because hypoxemia or inadequate ventilation (hypercarbia) can rapidly lead to metabolic acidosis and deterioration in the patient’s physiology and, possibly, cardiac arrest, these are frequent indications for an MET response. Airway management is the first priority. Most of the time, rapid institution of standard ICU management strategies suffice if tracheal intubation is needed. Relatively simple changes in technique, such as optimizing patient positioning, bimanual manipulation of the larynx with pressure on the tracheal cartilage (backward, upward, right, and posterior pressure), and choice of laryngoscope blade or appropriately sized endotracheal tube, can make a significant difference in successfully intubating the airway. Sometimes, specific rescue therapies are indicated. For patients with a difficult airway,3 the ability to apply rescue therapies within minutes is essential, which is why difficult airway teams are sometimes deployed. Recognition of the potential for, or existence of, a difficult airway is critical. Once recognized, the first step in management is to have the most experienced airway
Rescue Therapies in the Surgical Patient
manager available, typically an anesthesiologist or a senior nurse anesthesiologist. The second step is to provide the airway manager with all the tools that might be necessary to secure the airway. A variety of laryngoscope blades and endotracheal tube sizes can be very helpful. For a patient who needs ventilatory assistance but for whom bag-valve-mask ventilation is ineffective, rescue devices might include the laryngeal mask airway or esophageal-tracheal devices such as the Combitube (Covidien, Boulder, CO, USA) or King Airway (King Systems, Noblesville, IN, USA). Rescue devices that assist in placing an endotracheal tube include a gum elastic bougie and video laryngoscope or bronchoscope. The third step is to have an expert available during placement of a surgical airway, typically a cricothyrotomy. The expert may be a senior surgical resident or an attending surgeon. The availability of such a person is critical for the management of a dislodged tracheostomy tube in a patient with a difficult airway. Deployment of a difficult airway team can decrease the need for an emergency surgical airway.4 Once the airway has been secured, patients may still have difficulty with oxygenation or ventilation despite administration of high levels of oxygen and increasing levels of airway pressure. Of utmost concern in this situation is the development of acute respiratory distress syndrome or preceding acute lung injury. Although there are no rescue therapies that have been proved to improve outcomes in these circumstances, several approaches have been used.5 Ventilation with pressure-controlled modes can sometimes improve pulmonary recruitment, while deleteriously limiting high peak, mean, and plateau airway pressures. Increasing the inspiratory to expiratory (I:E) ratio can further recruit alveoli. This approach has been taken to the extreme with airway pressure release ventilation, a modified form of continuous positive airway pressure that does not use traditional cyclic ventilation and, therefore, does not have a typical I:E ratio. More extraordinary is the use of high-frequency ventilation, which has taken many forms, including highfrequency positive pressure ventilation, high-frequency jet ventilation, and highfrequency oscillatory ventilation. These modes provide relatively constant mean airway pressure with very rapid shallow breaths, which may minimize ventilatorinduced lung injury. This mode may be most useful during operative interventions on the airway or in patients with bronchopulmonary fistulas because it is generally accompanied by carbon dioxide (CO2) retention, respiratory acidosis, and deep sedation of neuromuscular blockade to enable patient tolerance of the mode. A separate approach to improving oxygenation is using inhaled nitric oxide (iNO). The desired physiologic effect of iNO is to cause local vasodilatation in lung zones that have the best ventilation, thus improving ventilation/perfusion matching, particularly in patients with pulmonary hypertension. Because of the extremely short half-life of iNO once in contact with hemoglobin, there are minimal systemic effects. To date, although improvements in oxygenation may be realized, no durable improvements in patient survival, ventilator-free days, or ICU length of stay have been achieved. Ventilation/perfusion matching can also be improved with prone positioning, taking advantage of gravitational forces. When the patient is initially placed prone, blood flow increases to the well-recruited lung segments while the previously atelectatic/dependent lung segments are recruited. Routine shifting from supine to prone and back is then instituted. Care must be taken when placing a patient in this position to avoid the development of pressure injuries and tube dislodgement. Not all patients respond to prone positioning, and there is no consensus regarding the duration of prone positioning, the number of times per day a patient should be in the prone position, or the number of days for which prone positioning should be continued. Moreover, no
435
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Tisherman
improvement in outcome has been ascribed to prone positioning, relegating it to an adjunctive role in rescuing a patient from hypoxemic respiratory failure. For patients with severe pulmonary disease localized to one lung, such as pneumonia, pulmonary contusion, or single-lung transplant, body positioning, with the good lung dependent, may improve blood flow to a well-ventilated lung while increasing recruitment of the diseased lung. Care should be taken to avoid soiling the good lung when the infected lung is placed in the nondependent position. In this circumstance, placement of a double-lumen endotracheal tube may allow differential ventilation of the lungs (ie, simultaneous independent lung ventilation) to optimize recruitment of the diseased lung while protecting the healthy lung. Extracorporeal membrane oxygenation (ECMO) is perhaps the most risky and laborintensive technique for improving oxygenation in a patient with refractory hypoxemia. ECMO involves venovenous or venoarterial cannulation, a pump, and an oxygenator to allow oxygenation of the blood and CO2 removal. This technique has become the standard in the neonatal population. In adults, using ECMO has become more common with improved systems and experience, most recently with outbreaks of H1N1 influenza. Given the complexity of managing patients on ECMO, this intervention is best reserved for institutions with sufficient experience. Although these rescue therapies may improve oxygenation in many patients with refractory hypoxemia, no mortality benefit has been demonstrated. Still, these therapies may be appropriate in selected patients. CARDIAC EVENTS
Hypotension is a common perioperative complication. Multiple causes of shock need to be considered, including hypovolemia, sepsis, pulmonary embolism, and an acute coronary syndrome.6 While completing diagnostic studies to determine the cause, the initial management includes ensuring adequate plasma volume resuscitation, supporting cardiac function with inotropes as needed, and judicious use of vasopressors. Specific causes of hypotension may require specific rescue therapies when the initial management is insufficient. If the patient is hypovolemic, the first concern is bleeding. In addition to fluid and blood resuscitation, this condition may necessitate surgical intervention or perhaps embolization by interventional radiology. Coagulopathy (warfarin anticoagulation) including therapeutically induced platelet dysfunction (aspirin, clopidrogel) should be concomitantly addressed. A massive transfusion protocol that is jointly developed with transfusion medicine may be lifesaving in those with massive gastrointestinal tract hemorrhage, postoperative hemorrhage, or iatrogenically induced blood loss (eg, torn iliac vein during sheath introducer insertion). Septic patients often require initial plasma volume resuscitation. Vasopressors should be added only when the patient remains hypotensive despite fluid resuscitation. Adequate cardiac performance should be ensured. Controlling the source of sepsis is critical. Although there is plenty of controversy, there may be a role for steroids in patients with absolute or relative adrenal insufficiency.7 Activated protein C has been recently withdrawn from the market because of lack of efficacy. Surgical patients are at high risk of pulmonary embolism because of hypercoagulable states, immobility, and vessel trauma. Diagnosis of pulmonary embolism in an unstable patient may be difficult. Bedside echocardiography can be helpful in these circumstances if it demonstrates right ventricular hypokinesia, asymmetric dilatation of the right ventricle versus the left ventricle, or strain. In addition to standard anticoagulation, rescue therapies for patients who remain hypotensive due to massive
Rescue Therapies in the Surgical Patient
pulmonary embolism include intravenous thrombolytic therapy (there is no evidence that catheter-directed therapy is more effective or safer), catheter embolectomy, or operative embolectomy.8 These therapies carry significant risks but may be lifesaving. Acute coronary syndrome occurs in the perioperative period because of stress and, possibly, hypercoagulable states. Often, the issue is demand ischemia (eg, from hypoxemia or hypotension) in a patient with fixed coronary atherosclerotic disease. Rapid correction of the underlying process, plus beta-blockade if possible, is the main strategy for management in such circumstances. Occasionally, however, acute coronary occlusion occurs in the perioperative period. Standard management for an acute myocardial infarction, including the administration of oxygen, aspirin, betablockade, and anticoagulation, is indicated unless there is a significant contraindication. Therapies aimed at rapid revascularization should also be used if possible. However, based on the perceived risk of hemorrhage in the perioperative period, the use of lytic therapy is too risky in the immediate perioperative period. Cardiac catheterization, although the patient may still require antiplatelet therapy after stent placement, may be indicated. In many hospitals, a system is in place for rapid mobilization of the cardiology team to minimize the event-to-balloon time.9 If patients develop profound cardiac dysfunction despite maximum medical therapy, mechanical circulatory support with an intra-aortic balloon pump in the short term, or a ventricular assist device for long-term support, may be necessary. Patients may also suffer a cardiac arrest in the perioperative period. Traditionally, code teams respond to these events. Although, intuitively, use of METs decreases the incidence of cardiac arrests and/or improves outcomes, this has been difficult to prove.10 Sudden events leading to cardiac arrest include pulmonary embolism and myocardial infarction. In addition, cardiac arrest may be the end result of deterioration because of multiple organ dysfunction, sepsis, or hemorrhage and may not be reversible. When sudden cardiac arrest occurs, standard advanced cardiac life support therapies should be initiated. Frequently, spontaneous circulation cannot be restored. Those who regain a pulse, however, may not rapidly recover neurologic function.11 Randomized clinical trials in comatose survivors of out-of-hospital cardiac arrest with initial rhythms of ventricular fibrillation (VF)/ventricular tachycardia (VT) demonstrated improved neurologic outcomes and survival with therapeutic hypothermia. The American Heart Association now recommends that comatose survivors of out-of-hospital VF/VT be cooled to 32 C to 34 C for 12 to 24 hours. Therapeutic hypothermia should be considered for patients who suffer a cardiac arrest in hospital and for patients with other initial rhythms. Unless there is a clear contraindication, surgical patients should be treated similarly. Postcardiac arrest care has, until recently, received little direct attention. It seems clear, however, that optimizing management could readily affect outcomes. To this end, the primary cause of cardiac arrest should be addressed rapidly with, for example, cardiac catheterization for coronary occlusion or thrombolytic therapy for acute pulmonary embolism. In addition, appropriate blood pressure and glucose control are recommended. Neurologic evaluation and prognostication, as well as referral for rehabilitation, are needed. Some institutions have organized teams to assist in the management of patients after cardiac arrest. NEUROLOGIC EVENTS
Critically ill surgical patients frequently develop delirium in the perioperative period. This may be associated with medications (new agents or failure to continue existing agents), alcohol withdrawal, sepsis, and exacerbation of underlying comorbidities.
437
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Optimal therapy for the delirious patient remains unclear. Therefore, strategies to prevent delirium, such as judicious use of sedatives and analgesics in patients at risk, optimizing environmental factors, and rapidly treating perioperative complications, should have a greater impact. Without focal findings on examination, computed tomography (CT) or magnetic resonance imaging of the head is rarely helpful. More severe neurologic events, particularly stroke, can occur in the perioperative period.12 Any patient who has a new focal neurologic deficit should undergo a stat CT of the head. If an ischemic stroke is suspected, administration of tissue plasminogen activator (tPA) should be considered if standard criteria are met and tPA use is not contraindicated. Some institutions have a designated stroke service that is prepared to quickly evaluate such patients. Urgent angiographic evaluation with possible stent placement is a new therapy that is used in some situations, particularly in patients for whom thrombolytic therapy is contraindicated, although these therapies are not mutually exclusive in select patients. It is clear that the more rapidly tissue oxygen delivery is re-established, the better is the postevent neurologic outcome. SUMMARY
Critical events are common in the perioperative period. Rapid identification of patient deterioration and rapid deployment of a team prepared to manage the patient’s condition may affect morbidity and mortality. When necessary, rescue therapies should be used for airway management, ventilatory and cardiovascular support, and severe neurologic deficits. Use of these rescue therapies may improve patient outcomes. REFERENCES
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Rescue Therapies in the Surgical Patient
11. Peberdy MA, Callaway CW, Neumar RW, et al. Part 9: post-cardiac arrest care: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122:S768–86. 12. Lukovits TG, Goddeau RP. Critical care of patients with acute ischemic and hemorrhagic stroke: update on recent evidence and international guidelines. Chest 2011;139(3):694–700.
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