Artículo de Reflexión

José Ricardo Navarro V.*

* Profesor Asociado Departamento de Cirugía Universidad Nacional de Colombia. Correspondencia: Carrera 30 No. 45-03, Facultad de Medicina. Of. 205. Bogotá, Colombia. Correo electrónico: jrnavarrov@unal.edu.co

Recibido: febrero 14 de 2011. Enviado para modificaciones: mayo 11 de 2011. Aceptado: agosto 7 de 2011.

Introduction. Managing critical events in the OR is not always consistent with the usual resuscitation management and can be considered an anesthesia therapeutic approach.

Mathodologhy. On the basis of an Australian study that monitored 4,000 anesthesia incidents, an algorithm of simplified acronyms has been implemented. The American Heart Association (AHA) uses the cardiovascular quadrant to localize the main cause of hemodynamic instability, in accordance with 4 components: Cardiac pump, heart rate, resistance and volume.

Results. This review combines both systems to successfully manage any critical events during anesthesia.

At the 16th French Anesthesiology Congress (1964) the Dean of the School of Medicine and Pharmacy in Marseille (1) stated:

In order to put the modern therapies under way, a larger number of experts and qualified resuscitation anesthesiologists are needed with training in three disciplines:

• Clinical - because they treat sick patients.

• Technical - because they use complicated instruments and must be constantly up-to-date.

• Biological - because they are required to have a background knowledge of physiology, pharmacology and biochemistry for an appropriate selection of the anesthetic agents and methods and to be able to monitor the consequences of their actions… Is anes thesia thera peutic ?

Already in 1963 Germán Muñoz and Jaime Casasbuenas strongly argued that: ”The anesthesiologist is, above all, a medical doctor, and hence has the ability to follow a therapeutic approach towards the patient; most likely, such therapeutic approach is based on previous fundamental lessons” (2).

During the past Anesthesiology Course of the Sánitas University Foundation - Horizons in Anesthesiology - (3) Pedro Ibarra emphasized this point referring to the type of patients that could get better with anesthetic treatment; he mentioned an editorial from the Journal of Anesthesia & Analgesia written by Rosenbaum and Barash in 1989 (4) that referred to the “other role” of anesthesia, in addition to facilitating the surgical procedure: to administer treatment. In that respect, Ibarra mentioned five aspects in which the administration of treatment by the anesthesiologist could be crucial:

• Using beta-blockers during the preoperative period in patients with moderate / high risk (> 5 %) of developing cardiovascular events, as long as the probability for post-op hypotension is minimal (5).

• Fluid restriction to normovolemic levels in major abdominal surgery to reduce the number of cardiovascular events and shorten the hospital stay (6).

• Multimodal pain management for positive physiological outcomes during the post-operative period (7,8).

• Use of appropriate anesthetic techniques such as regional anesthesia, to reduce the incidence of relapses in cancer surgery. Since general anesthesia does not suppress the activation of the sympathetic system, it may facilitate immunosuppression (9).

• Providing an additional alternative to opiates in the management of post-operative pain (POP). Administering opiates for pain control may result in immunosuppression because of their effects on cytokines (reduced IFN and FNT) and on natural killer cells (10,11).

In addition to this broad range of applications, there is one more therapeutic action of anesthesia: resuscitation and management of critical events. The definition of a critical event in anesthesia is complex because it is not only limited to cardio-respiratory events that necessarily lead to heart arrest; it is rather related to incidents of varying etiologies that result in an adverse event (12). However, when appropriate algorithms are used, these may make a difference between life and death for the patient.

In its 50 years of activities the American Heart Association (AHA) with its motto “Learn and Live”, has made encouraging progress towards recovering life for those hearts that should not die yet. It emphasizes planning by actions and this is the aim of the chain of survival since Cummins introduced the concept in 1991 (13).

61.9 % of intra-hospital heart attacks are considered to be potentially avoidable (14); thus, on the basis of semiology, an early diagnostic may be made through inspection (evaluation of dyspnea, disorientation, diaphoresis, chest pain), palpation and auscultation, percussion and the analysis of the electrocardiographic records as well as the implementation of the sequence described in Figure 1: oxygen, monitor, venous access.

Hemodynamic instability must be clinically identified in accordance with the four components of the cardiovascular quadrant (15,16), a strategy aimed at specific pathophysiological targets or events (cardiac pump problems, resistance, heart rate or volume) (17).

The recommendation for a patient who undergoes anesthesia is to use the basic vital support algorithms and the chain of survival (18), since usually the patient requires other elements for judgment depending on his / her status of awareness (figures 2 & 3).

In the OR, whenever the patient receives mechanical ventilation and presents a sudden critical event, the recommendation is to follow the DONE rule: Displacement of the tube; Occlusion (obstruction) thereof; tension Pneumothorax; Equipment failure (19). However, as we shall see later on, a large study on critical events in the OR has made available new algorithms for the management of crisis during anesthesia.

Adult Chain of Survival

1. Secure the scene and determine the level of awareness

2. Activate the emergency system

3. Early CPR, emphasizing chest compressions

4. Rapid defibrilation

5. Effective advanced vital support

6. Comprehensive Post-cardiac arrest care

How to approach any critical events in the OR

Knowledge about mirror neurons (20) has established that the brain neo-cortex must be sensitized to known coping strategies; this knowledge has been reproduced through optimal simulation in aviation training scenarios, rescue and military operations, etc. (21). In the case of critical events, resuscitation workshops have proven their efficacy in eliciting a timely response to a crisis. This would not be achieved expeditiously, despite the experience and common sense of the practitioner (22).

Efforts to reduce morbimortality from critical anesthetic events - that some people consider a critical public health issue - (23), have led to the development to reports such as the Australian Incident Monitoring Study - AIMS - (24 types of events), that began in 1988 (24). The basis feature of the study was to obtain voluntary and anonymous reports about any event that represents a risk to the health and safety of the patient. The study has provided abundant data about crises in anesthesia and adverse events (anaphylaxis, difficult intubation, cardiac arrest, wrongful administration of drugs, etc.), in addition to the problems with monitoring (appropriate or inappropriate), as well as factors related to the generation and resolution of such issues. Since this is an on going study readers are suggested to visit the link of the AIMS Study Web page for additional information (http://www.apsf.com.au/crisis_management/Crisis_Management_start.htm).

According to the referred Study, seven of eight infants were satisfactorily managed; however, following an expert panel revision of the cases the conclusion was that upon the implementa

tion of a simple system of acronyms, routinely used at the time of the crisis, and similar to a check-list, the critical event could be solved in 1/8 of the remaining cases (25).

The algorithm developed after a revision of the Australian study was COVER, which provides guidelines about the functional diagnosis and appropriate incident response. COVER is the acronym for Circulation, Oxygenation, Ventilation and Vaporizers, Endotracheal tube, Revising monitors and equipment. The ABCD-A SWIFT CHECK is a diagnostics check-list (25); 24 additional sub-algorithms were developed for managing such list.

When the patient is being spontaneously ventilated with whichever device (including a laryngeal mask) and presents a critical event, the COVER ABCD-A SWIFT CHECK algorithm becomes AB COVER CD-A SWIFT CHECK, since first and foremost a respiratory cause has to be ruled out.

Another useful acronym to determine the level of urgency perceived by the anesthesiologist is a revision of each component in COVER called SCARE:

Scan: a rapid visual inspection is performed

Check: manual exploration

Alert / Ready: ask for a crash cart and help

Emergency: the emergency is declared with no hesitation and specific tasks are assigned

Description of acronyms

COV ER (26)

Circulation: feel the pulse. Correlate the frequency, rate and intensity to the pulse oximeter wave and any electrocardiographic changes. Examine the capillary filling and expired CO₂.

Color: If you suspect any flaw in the pulse oximeter, then you should put it in your own finger and check the condition of the monitor; take the patient’s blood pressure or saturation using blood gasses.

Oxygen: The oxygen flow should be increases and the new FiO₂ calculation in the respiratory cycle. Assess any changes in FiO₂ with regards to the respiratory cycle.

Ventilation: You must switch to manual ventilation. Evaluate the complete distribution system of the anesthesia machine.

Vaporizers: Make sure that the vaporizer is working properly.

Endotracheal Tube or Laryngeal Mask: Make sure that the device is properly positioned inside the airway; the tracheal tube should not be selective.

Al alternate oxygen supply system should be available (AMBU®).

Check the monitors: Evaluate every monitor (pulse oximeter, capnography monitor, blood pressure monitor and cardio vision instrument); check for appropriate calibration, alarms and appropriate functioning.

Revision of Equipment: You should make sure that any equipment in contact with the patient is working properly and safely.

ABCD

A. Airway: Observation, palpation and auscultation of the neck. In case of doubt, do a laryngoscopy.

B. Ventilation: Palpation and auscultation of any respiratory bruits inside the chest. Revise the expired CO₂.

C. Circulation: Check the blood pressure trends and try to explain any abnormal measurements.

D. Drugs: Examine the vials, syringes, brands, infusion pumps, venoclisis and extensions of anesthesia and make sure that everything is administered at the right doses and times.

The term A SWIFT CHECK is intended do rule out any Air and Allergy issues and to quickly explore both, the patient and the human team: condition and status of the patient, the surgeon, the process and the responses (Table 1).

60 % of the cases are solved in the first minute with the use of COVER ABCD; the remaining 40 % requires the use of the list in the acronym A SWIFT CHECK (Table 2) (26).

Resuscitation of a patient who is under the effects of the anesthetic agent in the operating room or in the post-anesthesia recovery room differs from the general resuscitation procedure; Ronald Miller says that despite all the technological breakthroughs and advances in monitoring of anesthesia, adverse events still happen in post-anesthesia care units (27).

With regards to approach to the management of critical patients, the AHA systematically uses simple and practical methodologies, targeted to the most usual events. The use of the four components of the cardiovascular quadrant (Pump, Heart rate, Resistance and Volume) for the physiological diagnosis of hemodynamic instability (17) may be correlated with the sub-algorhythms of COVER ABCD-A SWIFT CHECK in the AIMS Australian Study, in addition to a respiratory component fundamental to the practice of anesthesia.

When the patient exhibits a respiratory difficulty, the recommendation is to use the respiratory quadrant, in accordance with the data of the Australian Study (26).

Respiratory Quadrant

1. Airway obstruction (62 cases involved/4,000 incidents) (28)

2. Laryngospasm 189/4,000 (29)

3. Regurgitation, vomiting and bronchoaspiration 183/4,000 (30)

4. Difficult intubation 147/4,000 (31)

5. Desaturation 584/4,000 (32)

6. Bronchospasm 103/4,000 (33)

7. Pulmonary edema 35/4,000 (34)

8. Pulmonary embolism 38/4,000 (35)

9. Pneumothorax 65/4,000 (36)

Cardiovascular Quadrant

Cardiac Pump

The patient that exhibits systolic hypotension (<90 mm Hg) accompanied by diaphoresis (sympathetic discharge), dyspnea (the first organ involved in shock is the lung), mental disorientation (insufficient oxygen flow into the brain) and chest pain (imbalance between the oxygen supply and demand in the myocardium) suggests that the problem lies in the cardiac pump.

The algorrhythm should follow the sequence of the patient aware: secure adequate oxygenation; monitoring according to COVER ABCD, and use of the venous line to take samples for laboratory tests (glycemia, electrolytes, enzymes) and resuscitation with parenteral drugs, including fluids, depending on the particular case (Figure 1).

If the patient is unconscious the surgeon should be informed and postpone or rapidly conclude the surgery, in addition to correcting any hemodynamic disorders. Close follow-up of the echocardiogram and of the cardiac enzymes, in addition to securing a hemodynamics above 10g/dl and starting beta-blockers in the absence of contraindications. The incidents related to this quadrant include:

10. Ischemia and myocardial infarction 125/4,000 (37)

11. Cardiac Arrest 129/4,000 (38)

Heart Rate

It is important to consider the possible causes; vagal maneuvers, oxygenation or ventilation disorders, anesthesia block, non-apparent blood loss, cardiac event, opiates effect, etc. Chronotropic drugs should be available: atropine, epinephrine or dopamine; furthermore, the use of a transcutaneous or a transvenous pacemaker should be considered and consult the cardiologist if the response is inappropriate. Incidents identified in the Australian study:

12. Bradycardia 265/4.000 (39)

13. Tachycardia 145/4.000 (40)

Resistance

If the patient is not under general anesthesia, he/she should be asked about his/her condition; the surgeon should be informed about the hemodynamic involvement and corrective measures implemented. You must keep in mind the risk of developing a Bezold Jarisch reflex (41) - a high anesthetic block with sudden vasodilation. This event may be triggered by a wrongful administration of drugs.

14. Anaphylaxis and Allergy 148/4,000 (42)

15. Regional Anesthesia 252/4,000 (43)

16. Sepsis 13/4.000 (44)

17. Hypertension 70/4,000 (45)

Volume

It is important to keep in mind that one of the key premises of resuscitation is: “First the patient, then the monitor” (46); therefore, the patient must be re-evaluated first and then the monitors checked.

If hypotension is associated with tachycardia, rule out hypovolemia, check the patient’s position, administer a bolus of crystalloids, use vasoconstrictors, and rule out any surgical causes. If hypotension is associated to bradychardia, consider an upper sympathetic block or the administration of opiates (38). The following events were identified in this quadrant:

18. Hypotension 438/4,000 (47)

19. Trauma 38/4,000 (48)

20. Water intoxication 10/4,000 (49)

Miscellaneous

In this segment you can identify any events different from the above quadrants:

21. Problems related to the administration of drugs during anesthesia, 1,119/4,000 (50)

22. Problems associated with vascular access, 128/4,000 (51)

23. Awakening during anesthesia, 21/4,000 (52)

24. Post-Anesthesia crisis status (53)

The application of the algorhythms of the Australian study has shown successful results in real life situations (54); however, they should not be considered as a straight jacket and the difficulty in learning each one of these algorhythms in each specific case can be lessened by involving the components of the cardiovascular quadrant suggested by the AHA and adding the respiratory quadrant. The simulation of these case scenarios in resuscitation seminars may positively strengthen the development of psychomotor skills and sensitize the mirror neurons to follow the resuscitation aphorism: “if you think, you lose”.

The role of the anesthetist in the OR goes beyond his trade as a specialist in managing the patient’s homeostasis. Neither is his/her only role to administer drugs to produce a condition of sedation, analgesia, hypnosis or loss of awareness and facilitate the surgical procedure. The anesthetist has an additional and probably more engaging responsibility: be the leader in the effective management of any hemodynamic or respiratory crisis affecting the patient that would otherwise inexorably result in the patient’s death.

Through the application of structured algorhithms, i.e. a check-list, the anesthetist may almost always diagnose the cause of the critical event in a timely manner and in most of the cases correct the problem.

Naturally, prevention must always precede cure, and therefore, in every procedure, the anesthetist must necessarily do a pre-anesthesia evaluation and follow the minimum safety rules on a routine basis.

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