Part 1
Literature review
Introduction
Despite tremendous development in the treatment of patients suffering from acute coronary syndromes, the incidence of cardiogenic shock has not declined significantly (Goldberg, Samad, and Yarzebski, 1999). Indeed, the rate of occurrence of cardiogenic shock has been stable in the last three decades. Cardiogenic shock is still one of the key causes of mortality among patients that suffer from all sorts of acute coronary syndromes (Hochman, Sleeper, and Godfrey, 1999).
As a result, there has been an increasing interest in the discovery of patients who have high risks for developing cardiogenic shock as well as in the search for diverse therapeutic strategies that can thwart its development or enhance its outcome. Bouki, Pavlakis, and Papasteriadis (2005) state that, “cardiogenic shock is a disorder caused by decreased systemic cardiac output in the presence of adequate intravascular volume, resulting in tissue hypoxia,” (p.124). The disorder can easily be diagnosed by measuring the systolic blood pressure (< 90 mm Hg if the disorder exists) where hypovolemia and other latent causes of hypotension are absent. In addition, patients with cardiogenic shock have a mental disability, cold damp skin, and oliguria.
Management of cardiogenic shock
Cardiogenic shock can be managed through different management therapies including supportive therapy, Mechanical Left Ventricular Assist Devices, Thrombolytic Therapy, Intraaortic Balloon Pump (IABP), Intraaortic Balloon Pump-Assisted Thrombolysis, and mechanical revascularization.
Supportive Therapy
Supportive therapy makes use of different elements and agents to manage the condition. Catecholamines are used to highly enhance cardiac output but no evidence suggests that they enhance the survival of the patient (Richard, Ricome, and Rimailho, 1983). Inotropes on the other hand help to stabilize patients when they are being assessed or transferred or where reversible etiology has been recognized. Nevertheless, inotropes can be used alone only to soothe or sedate the patients. Levosimendan is a calcium sensitizer that enhances the contractility of the heart muscles. Research studies show that levosimendan minimizes the rate of death of patients suffering from acute myocardial infarction caused by heart failure (Moiseyev, Poder, and Andrejevs, 2002). Diuretics or fluids can be administered according to the estimated pressures of the left ventricular filling.
Mechanical Left Ventricular Assist Devices
These devices are used to provide circulatory support to patients in cardiogenic shock, generally before cardiac transplantation is done. The success of the circulatory support devices has been contradictory with some studies showing positive effects on patients’ mortality rates (Hendry, Masters and Mussivand, 1999; Magovern, Sussman and Goldstein, 2001) while other studies showing negative effects (Gacioch, Ellis and Lee, 1992). This treatment alternative is however unavailable for the majority of patients due to a low ratio of the number of patients suffering from cardiogenic shock to the number of donor organs.
Thrombolytic Therapy
The result of cardiogenic shock is strongly associated with the potency of the coronary artery. Consequently, reperfusion therapy using thrombolytic agents has minimized the incidence of shock in acute myocardial infarction accompanied by unrelenting ST elevation. Goldberg, Samad, and Yarzebski (1999) illustrated that tissue-plasminogen activator has a higher efficacy rate than streptokinase in inhibiting shock.
Nevertheless, modern thrombolytic agents such as reteplase, which allegedly contain higher reperfusion rates, are linked to an occurrence of shock that is likened to the one seen with tissue-plasminogen-activator therapy. Once the cardiogenic shock has been identified, thrombolytic therapy is usually ineffective. It has been argued that acute hemodynamic abnormalities cause damaged fibrinolytic activity among these patients (Prewitt, Gu, and Garber, 1992).
Intra-aortic Balloon Pump (IABP)
Bouki, Pavlakis, and Papasteriadis (2005) state that, “the IABP is an intravascular, catheter-mounted counter-pulsation device with a balloon volume between 30 to 50 mL,” (p.126). The gadget is put in through the usual femoral artery and placed in the stooping thoracic aorta. The balloon is blown up during the cardiac diastole stage and punctured during the isovolumetric stage of left ventricular contraction. The diastolic inflation of the balloon increases the diastolic blood pressure and subsequently enhanced the perfusion of the coronary artery and the oxygen supply to the heart muscles.
On the other hand, the systolic deflation of the balloon reduces the systemic afterload and the oxygen consumption of the heart muscles. The total impact is a positive movement in the oxygen supply/demand ratio of the heart muscles, with a slight boost in systemic perfusion. Unfortunately, initial clinical practice illustrated that even though patients can be stabilized regularly, they cannot consequently be weaned and that the general effect stays unaltered (Nanas and Moulopoulos, 1994). Therefore, the main role played by IABP insertion in cardiogenic shock is to stabilize patients before investigation or to accompany other more effective therapies such as thrombolytic therapy.
Intraaortic Balloon Pump-Assisted Thrombolysis
The combination of IABP with thrombolytic therapy has been shown to improve the outcome of patients suffering from acute myocardial infarction complicated by cardiogenic shock. Barron, Every, and Parsons (2001) found that the combination of the two therapies significantly reduced the mortality rates of these patients by 18% (p.936). This positive outcome is explained by the fact that the increase of diastolic blood pressure by IABP enhances not only the rate but also the degree of coronary thrombolysis.
Mechanical Revascularization
The therapies discussed above have significant limitations that lower their success rates and the survival rates of the patients. As a result, much attention in the recent past has been focused on the management of cardiogenic shock using mechanical revascularization. Several studies have been carried out, all of which show positive outcomes in patients with cardiogenic shock. Between 1992 and 2003, a series of studies was conducted using 1,303 patients (Barron, Every, and Parsons, 2001). The mortality rate of these mechanical revascularized patients was found to be 50% or less as compared to the 90% mortality rate in the absence of mechanical revascularization. This positive result has been supported by other studies done using registry data (Edep and Brown, 2000; Hochman, Sleeper, and Webb, 1999).
These studies found that cardiogenic shock patients who were administered with early revascularization (within 30 days of the development of myocardial infarction) experienced a significant reduction in mortality rates. This benefit was still apparent a year after the therapy was administered. This group of research studies, therefore, favors the option of early revascularization. However, the same studies show that the success rate of the therapy depends on the age of the patients. For instance, Hochman, Sleeper, and Webb (1999) found that “for those less than 75 years of age, early revascularization saves 20 lives at 6 months per 100 patients treated,” (p.631). Despite this limitation and the high cost involved, mechanical revascularization remains the most effective management therapy for cardiogenic shock.
Management protocol
Competence of the physician and his team
The successful management of patients with cardiogenic shock requires a wide range of experience and skills on the part of the physician, junior attending physician, nurses, and other supporting staff. Experience in the cardiac catheterization laboratory, outpatient clinic, and non-invasive laboratory should be a prerequisite for managing cardiogenic shock. This team of healthcare providers should be adequately experienced and highly skilled in collecting data about the cardiovascular history of the patients; cardiovascular physical examination; life support techniques such as resuscitation; administration and assessment of invasive hemodynamic devices; management of temporary pacing, transvenous and transthoracic pacemakers in the intensive care units; troubleshooting and management of intra-aortic balloon counter-pulsation (IABP), mechanical ventilators and catheterization facilities.
Experience and skills in carrying out these responsibilities will enable the clinician and his team to quickly diagnose the condition of the patient and subsequently to administer the most appropriate prevention and treatment therapies (Menon and Hochman, 2002).
Procedures for the management of cardiogenic shock
The management of cardiogenic shock follows three steps once the condition has been identified. The first step is to immediately resuscitate the patient. Resuscitation protects the patient’s organs from injuries during the transportation of the patient to critical care units for treatment. This can be done by administering dopamine or noradrenaline (norepinephrine), according to the extent of hypotension, to increase the average arterial pressure.
Before the patient is transported for treatment, he/she should be administered with intra-aortic balloon counter-pulsation (Menon and Hochman, 2002). The arterial blood gas, as well as the oxygen concentration, should be continuously assessed. In addition, a fibrinolytic agent needs to be given to patients suffering from ST-elevation MI if the expected postponement to angiography is more than two hours.
The second step is to define the coronary anatomy. This is a crucial step in which the attending clinician should be in constant communication with the transport team to minimize delays in cardiac catheterization. The survival chances of the patients can be increased by timely reversal of hypotension using IABP support devices. However, some patients fail to respond well to IABP and therefore early revascularization should be performed immediately for such patients. In cases where a standard echocardiogram has already been carried out, the attending physician does not need to repeat the ventriculogram.
Shock is distinguished by a high occurrence of “triple vessel disease, left main disease, and impaired left ventricular function,” (Menon and Hochman, 2002, p.535). The degree of ventricular dysfunction and hemodynamic instability is positively related to coronary anatomy.
The last step involves carrying out the early revascularization. The most commonly preferred treatment is percutaneous coronary intervention (PCI). Other options include glycoprotein IIb/IIIa antagonists and stenting of the infarct-associated artery. Studies show that glycoprotein IIb/IIIa antagonists and stenting provide almost similar benefits to cardiogenic shock patients as the PCI. Nevertheless, if there is a lethargic flow despite the non-existence of post-coronary angioplasty stenosis, the attending physician and his team should wait until the flow has stabilized before performing the stenting. Whereas stenting can worsen distal embolization, glycoprotein IIb/IIIa antagonists can enhance reflow.
Part 2
Literature review
Several research studies have been carried out concern the pre-hospital management of cardiogenic shock patients. All of the studies agree that pre-hospital management should begin with a thorough examination of the patient. The initial examination is normally similar regardless of the location or level of care needed by the patient (European Resuscitation Council, 2005). If the assessment reveals that the patient is unresponsive and unable to breathe normally, the paramedic crew should perform cardiopulmonary resuscitation (CPR).
The major aim of the decision to resuscitate is to improve circulation and oxygenation of blood through chest compressions as well as ventilation through artificial ventilation. If the patient is found to exhibit a defibrillate pulseless arrhythmia, the crew should aim to restore the normal cardiac rhythm by rapid defibrillation (Gallagher, Lombardi, and Gennis, 1995).
The combination of good quality chest compressions and timely defibrillation is said to restore spontaneous circulation. This is important in the pre-hospital management of cardiogenic shock where the number of paramedic crew is normally two and hence the treatment options need to be limited to only the most basic (Brucke, Helm, Schwart and Lampl, 2007). Resuscitation of cardiogenic shock patients should be performed at the location of the attack and the patient should be transported to a hospital or critical care facility only after the resuscitation has been successful.
In the study by Jacobs, Nadkarni, and Bahr (2004), the authors argue that delay to treatment is an inevitable feature of pre-hospital management of cardiogenic shock unless the patient collapses whilst in the presence of the paramedic crew. Guidelines for the pre-hospital management of cardiogenic shock, therefore, recommend that the initial important time events should be recorded. These events include: “the time of onset of a witnessed shock, time of emergency call received, time of first CPR attempts, and the time of first defibrillation attempt,” (Jacobs, Nadkarni, and Bahr, 2004, p.239). The importance of the recording of time events lies in the immediate impact of delays on the survival rates of patients.
Larsen, Eisenberg, Cummins, and Hallstrom (1993) state that, “for every minute of delay to CPR and, if necessitated, defibrillation, survival models predict a 7-15% decrease in survival,” (p.1654). The provision of basic life support helps to increase the survival chances of the patient. Nolan and Soar (2008) argue that although basic life support is important, CPR only contributes about 40% of the normal cerebral perfusion. Cerebral perfusion is usually compromised when a cardiogenic shock occurs due to the fall of the mean arterial pressure to levels below 60 mmHg. Therefore, the 40 mmHg mean arterial pressure produced by CPR is way below the normal level. If the paramedic crew fails to achieve the normal mean arterial pressure, the hypoxic-ischemic cerebral injury will most definitely occur (ERC, 2005).
Hypoxic-ischemic cerebral injury and other complications that may occur during the pre-hospital management of cardiogenic shock patients can be mitigated through several pharmacological and neuroprotective agents. The major aims of post-resuscitation treatment are to ensure homeostasis and to prevent the occurrence of multiple organ dysfunctions that may occur after resuscitation following global ischemia (Nolan and Soar 2008).
Current evidence proposes that post-resuscitation syndrome is characterized by “sepsis-mimicking inflammatory changes such as elevated plasma cytokines, presence of circulating endotoxins, leukocyte dysregulation and adrenal dysfunction,” (Adrie, Adib-Conquy, Laurent, Monchi, Vinsonneau, et al., 2002, p. 564). At this point, the paramedic crew should aim at early coronary reperfusion and hemodynamic optimization as well as the control of ventilation and blood glucose level (Balan, Fiskum, Hazelton, Cotto-Cumba and Rosenthal, 2006). Coronary reperfusion can be achieved through thrombolytic therapy whereas hemodynamic optimization can be achieved through the Intra-aortic Balloon Pump (IABP).
The outcome of cardiogenic shock is strongly associated with the potency of the coronary artery. Consequently, reperfusion therapy using thrombolytic agents has minimized the incidence of shock in acute myocardial infarction accompanied by unrelenting ST elevation. Goldberg, Samad, and Yarzebski (1999) illustrated that tissue-plasminogen activator has a higher efficacy rate than streptokinase in inhibiting shock.
Nevertheless, modern thrombolytic agents such as reteplase, which allegedly contain higher reperfusion rates, are linked to an occurrence of shock that is likened to the one seen with tissue-plasminogen-activator therapy. Once the cardiogenic shock has been identified, thrombolytic therapy is usually ineffective. It has been argued that acute hemodynamic abnormalities cause damaged fibrinolytic activity among these patients (Prewitt, Gu, and Garber, 1992).
Hemodynamic optimization can be done using the Intra-aortic Balloon Pump (IABP). Bouki, Pavlakis, and Papasteriadis (2005) state that, “the IABP is an intravascular, catheter-mounted counter-pulsation device with a balloon volume between 30 to 50 mL,” (p.126). The gadget is put in through the usual femoral artery and placed in the stooping thoracic aorta. The balloon is blown up during the cardiac diastole stage and punctured during the isovolumetric stage of left ventricular contraction.
The diastolic inflation of the balloon increases the diastolic blood pressure and subsequently enhanced the perfusion of the coronary artery and the oxygen supply to the heart muscles. On the other hand, the systolic deflation of the balloon reduces the systemic afterload and the oxygen consumption of the heart muscles. The use of IABP by paramedics is becoming common in many countries and the transfer of IABP-dependent patients to critical care settings is considered to be a safe undertaking (MacDonald and Farquhar 2005, p.449).
The combination of IABP with thrombolytic therapy has been shown to have better results than when the therapies are used in isolation. Barron, Every, and Parsons (2001) found that the combination of the two therapies significantly reduced the mortality rates of these patients by 18% (p.936). This positive outcome is explained by the fact that the increase of diastolic blood pressure by IABP enhances not only the rate but also the degree of coronary thrombolysis.
Comparison between the literature and the New South Wales protocol for the management of cardiogenic shock
The Ambulance Service of the New South Wales established protocols that must be followed in the pre-hospital management of cardiogenic shock patients. These protocols include:
- Basic protocol 2;
- Cannulate;
- Treat the dysrhythmias if present;
- Adrenaline infusion;
- Pain management; and
- Urgent transport.
Basic protocol 2 outlines the most basic and crucial steps that need to be taken by the emergency medical services crew during the pre-hospital management of cardiogenic shock patients. These steps include: carrying the appropriate equipment to the patient; primary evaluation; preventing life-threatening hemorrhage; secondary evaluation; posture; oxygen; monitoring; treatment; and documentation. Majority of the studies reviewed above address and support Basic protocol 2 especially in the areas of initial assessment, oxygen, monitoring, treatment, and documentation of time events. Based on the literature review and the NSW Protocol, my newly devised protocol would be as follows:
- Primary assessment
- Cardiopulmonary resuscitation
- Documentation of vital time events
- Post resuscitation treatment
- Reperfusion therapy
- Haemodynamic optimization
- Transfer to hospital
Primary assessment
The primary assessment of the patient should be done immediately after the paramedic crew reaches the patient. Normally cardiogenic shock is easy to identify because it has distinct signs such as cold clammy skin (Hochman, Sleeper, and Godfrey, 1999). The paramedic crew should also check for the responsiveness and ability of the patient to breathe by himself. If this is not the case, the paramedic crew should immediately embark on a resuscitation attempt (ERC, 2005).
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is done to enhance the circulation and oxygen supply of blood using chest compressions as well as through artificial ventilation. This stage should also involve the restoration of the normal cardiac rhythm by rapid defibrillation (Gallagher et al., 1995).
Documentation of vital time events
Time is a very crucial element in the pre-hospital management of cardiogenic shock patients because it is a great determining factor of the patient’s survival rate. It is therefore important for the paramedic crew to record the events and the time at which such events unfold from the time the emergency call was made to the time of transfer to a critical care unit.
Post resuscitation treatment
Once resuscitation has been done, the paramedic crew should closely monitor the progress of the patients to check whether post-resuscitation complications such as multiple organ dysfunctions occur. The occurrence of such complications can be prevented through several therapies including reperfusion therapy and hemodynamic optimization.
Reperfusion therapy
Reperfusion therapy using thrombolytic agents such as reteplase has been shown to reduce the incidence of shock in acute myocardial infarction accompanied by unrelenting ST elevation.
Hemodynamic optimization
Hemodynamic optimization can be done using the Intra-aortic Balloon Pump (IABP). The net effect of IABP is a positive movement in the oxygen supply/demand ratio of the heart muscles, with a slight boost in systemic perfusion. Once on IABP, the patient can be transported to a critical care unit for further treatment.
Transport to the critical care unit
The transfer of IABP-dependent patients is an increasingly common incident in the pre-hospital management of cardiogenic shock. The transfer should however be done by a highly trained team of healthcare personnel that includes the paramedic crew, the attending physician, nurse, a perfusionist, and other practitioners who are experienced in the operation of IABP and management of a highly unstable patient.
The communication between the transporting paramedic crew and the attending physician and his team should be consistent to ensure that the physician is notified of any actual complications that may arise in the process and that the complications are well controlled. The use of a specially trained paramedic crew eliminates the need for critical care facilities to send their staff to accompany the paramedics. This helps in the optimal utilization of both human and physical resources and subsequently in the provision of adequate care to all patients (MacDonald and Farquhar, 2005).
Expanded scope of practice
The prevalence of cardiogenic shock can be minimized by early identification, transfer, and application of percutaneous coronary intervention to patients who are at high risk of developing the condition. It is also important for attending physicians to establish the etiology of cardiogenic shock and to timely define the coronary anatomy of patients. These measures will enable the clinicians to apply the most appropriate treatment therapies to the patient. Although mechanical revascularization has been proven to be more effective than other management therapies, its application to the elderly (those aged above 75 years) is still wanting.
This finding is worrisome because a significant number (more than 40%) of patients suffering from cardiogenic shock consists of people aged above 75 (Hochman and Skolnick, 2009). These patients usually have poor organ reserve and therefore cannot endure hemodynamic pressure of cardiogenic shock, thus contributing to high mortality rates of more than 70% if the traditional methods of therapy are used. It is therefore important for intensive and critical care units to identify which, if any, of the older patients with cardiogenic shock can be treated through early revascularization.
The most effective therapy for cardiogenic shock is its prevention. It is therefore important for at-risk patients to go for regular check-ups which can facilitate early reperfusion and hence the avoidance of the need to go through the more complicated and more expensive procedures. Most of these procedures have no or negative effects not only on the quality of life of the patients but also on their survival rates. In many cases, patients can survive the ordeal but are left in such a debilitating state that they cannot be able to perform the most basic chores on their own. Elderly patients especially are subjected to unnecessary, expensive, and painful procedures yet numerous opportunities abound to enhance their quality of life or to allow them to have a dignified death, when appropriate (Hochman and Skolnick, 2009).
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