CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 2, March/April 2010
100
AFRICA
Discussion
The sample size of vascular surgical patients who were with-
drawn from chronic beta-blockade in this study was nearly 1.5
times greater than the total number of cases previously reported
in the published literature. This study therefore adds substantially
to the data on this important peri-operative problem. It confirms
that withdrawal of chronic beta-blockade is potentially lethal.
It is, however, the first study to demonstrate that withdrawal
of a single dose of beta-blocker within the first 72 hours postop-
eratively is significantly associated with in-hospital mortality. It
is also the first study to specifically address predictors of mortal-
ity in patients who are withdrawn peri-operatively from chronic
beta-blockade, and to confirm that the response of the heart rate
between the day of surgery and the third postoperative day is
independently associated with mortality.
This study therefore suggests that rate-mediated ischaemia is
TABLE 4. DEMOGRAPHIC DATA, CARDIACAND SURGICAL RISK FACTORSAND POSTOPERATIVE PHYSIOLOGICAL DATA
FOR CASEAND MATCHED CONTROL COHORTS. VALUESARE MEAN (SD), MEDIAN (IQR) OR NUMBER (PROPORTION)
Characteristic
Cases
(
n
=
14)
Controls
(withdrawn
survivors)
(
n
=
28)
Controls
(continued
survivors)
(
n
=
28)
Matched case–control for beta-
blocker-withdrawn survivors
Matched case control for beta-
blocker-continued survivors
p
-value* OR* 95% CI*
p
-value* OR* 95% CI*
Pre-operative risk factors
Age
63.5 (
±
7.5) 63.4 (
±
7.0) 63.1 (
±
7.7)
Gender (male)
11 (78.6%) 15 (53.6%) 18 (64.3%)
0.11 5.72 0.66–49.4 0.33 2.30 0.43–12.24
Diabetic
3 (21.4%)
16 (57.1%) 11 (39.3%)
0.07 0.29 0.78–1.11 0.62 0.68 0.15–3.10
Hypertensive
9 (64.3%)
27 (96.4%) 24 (85.7%)
0.04 0.10 0.01–0.86 0.13 0.27 0.05–1.47
Smoker
9 (64.3%)
16 (57.1%) 13 (46.4%)
0.66 1.34 0.36–5.17 0.31 1.92 0.54–6.80
Ischaemic heart disease
10 (71.4%) 24 (85.7%)
21 (75%)
0.33 0.50 0.13–2.0 0.77 0.78 0.15–4.20
Congestive cardiac failure
0 (0%)
1 (3.6%)
1 (3.6%)
0.68 0.03 0–939855 0.68 0.26 0–939855
Stroke
2 (14.3%)
3 (10.7%)
4 (14.3%)
0.73 1.44 0.19–11.12 †
Creatinine
>
180
µ
mol.l
-1
3 (21.4%)
5 (17.9%)
5 (17.9%)
Pre-operative haemoglobin (g.dl
-1
) 8.8 (
±
2.5) 12.3 (
±
1.9) 13.1 (
±
2.1)
0.41 0.31 0.02–5.22 0.40 0.27 0.01–5.72
Pre-operative glucose (mmol.l
-1
)
8.5 (
±
3.7)
6.9 (
±
2.9)
8.9 (
±
4.2)
0.35 1.16 0.85–1.58 0.37 1.27 0.76–2.13
Pre-operative chronic medical therapy
No statin therapy
12 (85.7%) 19 (67.9%) 16 (57.1%)
0.18 4.59 0.50–42.40 0.92 4.00 0.80–20.01
Surgical risk factors
Supra-inguinal surgery
7 (50%)
17 (60.7%) 17 (60.7%)
0.51 0.63 0.17–2.42 0.51 0.63 0.17–2.42
Duration of surgery (minutes)
105 (65–190) 103 (76–149) 108 (58–164) 0.75 1.002 0.99–1.01 0.50 1.003 0.99–1.01
Surgery out of hours
1 (7.1%)
2 (7.1%)
2 (7.1%)
Postoperative physiological data and risk factors
SBP
<
100 or
>
179 mmHg
2 (14.3%)
4 (14.3%)
4 (14.3%)
Postoperative haemoglobin (g.dl
-1
) 10.7 (
±
3.3) 9.7 (
±
2.4) 10.5 (
±
2.1)
0.92 0.97 0.55–1.72 0.78 1.05 0.76–1.44
Postoperative glucose (mmol.l
-1
)
10.1 (
±
3.9) 9.3 (
±
4.3)
8.2 (
±
3.8)
0.63 0.92 0.65–1.30 0.75 1.04 0.80–1.36
*Not reported for variables used for matching †: no model fitted; SBP: systolic blood pressure; SD: standard deviation; IQR: interquartile range.
TABLE 5. CONDITIONAL LOGISTIC REGRESSION OF THE THREE PREDETERMINED RISK
FACTORS FOR MORTALITY FOLLOWINGWITHDRAWAL FROM CHRONIC BETA-BLOCKADE
Characteristic
Matched beta-blocker-
withdrawn survivors cohort
Matched beta-blocker-
continued survivors cohort
Odds ratio 95% CI
p
-value Odds ratio 95% CI
p
-value
Heart rate characteristics
Heart rate difference: day of surgery to last HR
1.10 1.01–1.18 0.03
1.09 1.004–1.18 0.04
Mean HR increase of
≥
six beats per minute from day of surgery*
13.66 1.70–110.09 0.014 6.06 1.27–28.93 0.024
Beta-blocker administration
No beta-blocker administration in first three days versus any administation
4.92 1.01–23.97 0.05 169.5 0.9–32943 0.06
Inotrope administration
Institution of peri-operative inotropic support
4.00 0.73–21.84 0.11
8.00 0.89–71.6 0.06
CI: confidence interval; HR: heart rate. *Optimal cut-off point from receiver operating characteristic curve from the withdrawn survival cohort.
TABLE 6. HEART RATE CHARACTERISTICS OF
MATCHED CASE–CONTROL STUDY OF PATIENTS
WITHDRAWN FROM CHRONIC BETA-BLOCKADE
Mean HR (SD)
t-test
Day of surgery Last HR Day of surgery Last HR
Died
72 (18)
92 (21)
0.66
0.047
Survived 75 (14)
80 (18)
HR: heart rate; SD: standard deviation; last HR: mean heart rate on
third postoperative day or last day in hospital if earlier than the third
postoperative day.