- Email: [email protected]
Reply to the Letter to the Editor
Resuscitation 49 (2001) 321 www.elsevier.com/locate/resuscitation
Reply to the Letter to the Editor Thank you for the opportunity to reply to Dr Jon Mackay’s carefully constructed and informative commentary on our recent article (Dane et al., Resuscitation 2000;47:83 –87). We very much appreciate Dr Mackay’s interest in our work. As Dr Mackay correctly notes, our design did not allow us to identify the mechanism whereby 38% of patients discovered by ACLS-trained nurses survived, compared to 10% of patients discovered by nurses not trained in ALCS. Dr Mackay proposes that there were major differences between the patient groups or the types of arrest. Specifically, Dr Mackay proposes that trained nurses may have a higher proportion of patients (1) with more favorable arrest rhythm; (2) on monitors; (3) in ICU beds; and/or (4) with witnessed arrests. (All of these conditions have been adequately demonstrated to be associated with higher survival rates). We noted (p. 85) there was no statistical interaction between nurse training and arrest rhythms in our logistical regression for survival. Thus, there is no statistical evidence that differential proportion of rhythms between the two types of nurses was related to the outcome. Although it was not reported in the article, a chi-square test ( 2-test) of association between initial rhythm and ACLS training level also was not significant, 2(3)=5.43, P \14; the two groups of nurses did not encounter differential proportions of initial rhythms. We measured (p. 84) whether or not the patient was on a monitor at the time the code was called and reported that monitor status was not associated with survival (p. 85). Whether or not the patient was on a monitor was associated with training status, 75% of the patients were on monitors for ALCS-trained nurses, 50% were on monitors for nurses not trained in ALCS, but this difference in monitor status was not related to survival in our sample. Similarly, we measured (p. 84) whether the patient was on ICU or floor and reported (p. 85) that this variable was not related to survival. Thus, while Dr Mackay correctly notes ALCS-trained nurses were
more likely to call codes in ICU, that difference was not related to survival. Although not reported in the article, we also assessed the relationship between location (ICU vs. floor) and whether or not the code was initiated ‘early’ (see p. 86); the association was not significant, 2(1)= 0.40. We did not report analyses involving whether or not the arrest was witnessed, primarily because this was highly correlated with whether or not the patient was on a monitor (= 0.41). In our sample, witnessed arrests were no more likely to be survived that those not witnessed, 2(1)= 0.36, but this may result from the fact that the majority of the arrests (81.5%) were witnessed. It is the case that ALCS-trained nurses had a higher percentage of witnessed arrests (86%) than nurses not trained in ACLS-trained (69%), but we were unable to connect this difference to survival. We are pleased to have revisited the data through the lens provided by Dr Mackay’s suggestion, but our conclusion must remain ‘mechanism unknown’. A larger data set would have enabled us to assess more complicated mechanisms fruitfully, but the data reported in the article simply did not contain sufficient degrees of freedom to consider combinations such as witnessed-plus-ACLS-plus-rhythm. We share Dr Mackay’s skepticism regarding a ‘conclusively demonstrated’ link between advanced cardiac life support and improved survival to discharge. We conclude only that we demonstrated a link with a small data set. Others, with alternate (and larger) data sets, must determine whether that link can be considered conclusive.
.
0300-9572/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 0 0 - 9 5 7 2 ( 0 1 ) 0 0 3 6 6 - 5
F.C. Dane Department of Psychology, Mercer Uni6ersity, 1400 Coleman A6enue, Macon, GA 31207 -0001, USA E-mail: dane – [email protected]
Reply to the Letter to the Editor Thank you for the opportunity to reply to Dr Jon Mackay’s carefully constructed and informative commentary on our recent article (Dane et al., Resuscitation 2000;47:83 –87). We very much appreciate Dr Mackay’s interest in our work. As Dr Mackay correctly notes, our design did not allow us to identify the mechanism whereby 38% of patients discovered by ACLS-trained nurses survived, compared to 10% of patients discovered by nurses not trained in ALCS. Dr Mackay proposes that there were major differences between the patient groups or the types of arrest. Specifically, Dr Mackay proposes that trained nurses may have a higher proportion of patients (1) with more favorable arrest rhythm; (2) on monitors; (3) in ICU beds; and/or (4) with witnessed arrests. (All of these conditions have been adequately demonstrated to be associated with higher survival rates). We noted (p. 85) there was no statistical interaction between nurse training and arrest rhythms in our logistical regression for survival. Thus, there is no statistical evidence that differential proportion of rhythms between the two types of nurses was related to the outcome. Although it was not reported in the article, a chi-square test ( 2-test) of association between initial rhythm and ACLS training level also was not significant, 2(3)=5.43, P \14; the two groups of nurses did not encounter differential proportions of initial rhythms. We measured (p. 84) whether or not the patient was on a monitor at the time the code was called and reported that monitor status was not associated with survival (p. 85). Whether or not the patient was on a monitor was associated with training status, 75% of the patients were on monitors for ALCS-trained nurses, 50% were on monitors for nurses not trained in ALCS, but this difference in monitor status was not related to survival in our sample. Similarly, we measured (p. 84) whether the patient was on ICU or floor and reported (p. 85) that this variable was not related to survival. Thus, while Dr Mackay correctly notes ALCS-trained nurses were
more likely to call codes in ICU, that difference was not related to survival. Although not reported in the article, we also assessed the relationship between location (ICU vs. floor) and whether or not the code was initiated ‘early’ (see p. 86); the association was not significant, 2(1)= 0.40. We did not report analyses involving whether or not the arrest was witnessed, primarily because this was highly correlated with whether or not the patient was on a monitor (= 0.41). In our sample, witnessed arrests were no more likely to be survived that those not witnessed, 2(1)= 0.36, but this may result from the fact that the majority of the arrests (81.5%) were witnessed. It is the case that ALCS-trained nurses had a higher percentage of witnessed arrests (86%) than nurses not trained in ACLS-trained (69%), but we were unable to connect this difference to survival. We are pleased to have revisited the data through the lens provided by Dr Mackay’s suggestion, but our conclusion must remain ‘mechanism unknown’. A larger data set would have enabled us to assess more complicated mechanisms fruitfully, but the data reported in the article simply did not contain sufficient degrees of freedom to consider combinations such as witnessed-plus-ACLS-plus-rhythm. We share Dr Mackay’s skepticism regarding a ‘conclusively demonstrated’ link between advanced cardiac life support and improved survival to discharge. We conclude only that we demonstrated a link with a small data set. Others, with alternate (and larger) data sets, must determine whether that link can be considered conclusive.
.
0300-9572/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 0 0 - 9 5 7 2 ( 0 1 ) 0 0 3 6 6 - 5
F.C. Dane Department of Psychology, Mercer Uni6ersity, 1400 Coleman A6enue, Macon, GA 31207 -0001, USA E-mail: dane – [email protected]