Cardiopulmonary resuscitation: a review (Proceedings)
-To discuss current thoughts and techniques in cardiopulmonary resuscitation.
Cardiopulmonary Arrest (CPA)Cardiopulmonary arrest and resuscitation are not practice-builders! The success rate of cardiopulmonary cerebral resuscitation (CPCR) for animals or humans is disappointingly low. For example, one retrospective investigation of intensive care patients at Colorado State University found that only 4.1% of the dogs and 9.6% of the cats which suffered cardiopulmonary arrest survived to discharge (Wingfield et al.1992). However, animals which experienced respiratory arrest alone were much more likely to be successfully resuscitated. Studies in human hospital patients indicate that ~21-29% will survive to discharge.
Anesthetic-related cardiopulmonary arrest and mortality is a concern for owners and veterinarians alike. In 2006, Broadbelt and co-workers reported that the risk of anesthesia and sedation-related death to be 0.17% and 0.24% in dogs and cats, respectively. Interestingly, the postoperative time period was the most common time period for perianesthetic death (within 3 hours of termination of the procedure) in this study. A variety of investigations have identified factors that increase or decrease anesthetic risk for mortality. Poor health status (increasing ASA classification), breed (brachycephalic), old age, small size, xylazine, trauma, urgency of procedure, and length of procedure have all been associated with increased risk of death associated with anesthesia in recent studies. Premedication with acepromazine was identified as a factor that decreased the risk associated with general anesthesia in one study (Brodbelt et al. 2007), and the presence of technician monitoring reduced risk in another (Dyson et al. 1998). Pulse oximetry was identified as a monitoring tool associated with decreased mortality in cats (Brodbelt et al. 2007).
Anesthetized patients suffering CPA may have improved outcome as compared to the general population. Presumably this is because those patients are intubated, breathing 100% O2, and have a peripheral catheter in place. Moreover, recognition of CPA will most likely occur more rapidly in the anesthetized patient. Indeed, one investigation (Kass, J Vet Emerg Crit Care, 1992) observed that all survivors of CPA were those animals whose arrest was associated with anesthetic drug administration Similarly, Hofmeister and co-workers (2009) evaluated cardiopulmonary arrest in a teaching hospital and showed that CPCR was more likely to be successful in dogs that had cardiopulmonary arrest while anesthetized.
Anesthesia-related CPA may be due to equipment failure, respiratory or cardiovascular problems, or human error. Cooper and co-workers (2002) reported that 82% of preventable anesthetic mishaps were associated with human error. Although the majority of mishaps in this study did not result in patient mortality, the findings highlight the importance of training, checklists, communication, and preparation in preventing anesthetic-related mortality. Indeed, due to the low rate of successful resuscitation and significant morbidity in survivors, prevention of CPA should be one of the most important goals of any anesthesia management plan.
Four factors are generally believed to be related to poor outcome of CPA: 1) Long arrest time prior to initiation of CPR. 2) Prolonged ventricular fibrillation. 3) Inadequate coronary or cerebral perfusion during CPR. 4) Pre-existing disease. Early recognition and appropriate intervention are the keys to successful resuscitation.
The following is a summary of the latest recommendations in CPCR:
Airway and Breathing:
Airway and breathing: Rapid placement of a cuffed endotracheal tube is an important first step in CPCR. It is important to confirm correct placement of the tube within the trachea as capnography will not necessarily indicate proper tube placement when cardiac output is low or nonexistent (That is, ventilation through a properly-placed endotracheal tube may not necessarily result in a detectable exhaled CO2). Manual ventilation should be initiated as soon as possible and at a rate of 10-12/min, inspiratory pressure less than 20 cm H2O and with an inspiratory time of ~ 1 second. The inspired gas mixture should include supplemental oxygen whenever possible.