In Reply:

Dr. Alexander Avidan asserts that hypotension is only associated with adverse outcomes. In fact, a randomized trial identified a 27% reduction in the relative risk of a composite of serious complications in patients assigned to tight individualized versus routine blood pressure management.1  Available evidence thus suggests a causal relationship.

Dr. Avidan asks whether various monitoring methods might explain differences between ambulatory and perioperative pressures in our recent report.2  We recorded ambulatory pressures with upper-arm cuff oscillometry, a well-validated technique.3  Oscillometric ambulatory pressures better estimate individual blood pressure than single office measurements4  and are considered the reference method for assessing out-of-office pressures.5  For example, an international consensus group recently defined automated ambulatory blood pressure monitoring as “the optimal method to establish baseline values” before surgery.6 

We similarly used upper-arm oscillometry to measure blood pressure before induction of general anesthesia and in 98% of patients during surgery. The relationship between oscillometrically and directly measured pressures is thus irrelevant to our assertion that preinduction pressure poorly represents normal ambulatory pressure. Upper-arm cuff oscillometry is by far the most common intraoperative blood pressure monitoring approach and is routinely used by clinicians to guide care. As with any monitor, oscillometric pressures are imprecise, but systematic bias is small.7 

Dr. Avidan notes that arm-to-arm blood pressure differences may have contributed to the poor relationship we observed between preinduction and ambulatory pressures. Population average systolic and diastolic pressures are similar in the right and left arms.8  There can be inter-arm differences in individual patients,8  but substantive differences are relatively rare. In patients like ours, for example, only about 5% of patients have a systolic inter-arm difference of 10 mmHg or more.9  Presumably, inter-arm differences in mean arterial pressure would be even less.

Only 2% of our patients had an arterial catheter. Our clinical routine is to correctly level and zero pressure transducers, and repeatedly evaluate signals for incorrect damping. Importantly, we report mean arterial pressures, which are hardly influenced by damping. And again, errors would presumably be random and unlikely to influence our conclusions.

Dr. Avidan notes that we recorded ambulatory pressures at 30-min intervals and, of course, monitored pressures far more often intraoperatively. The issue, though, is not the frequency per se, but whether the frequency was sufficient to identify clinically important variation under each condition. Ambulatory pressures presumably change slowly compared to intraoperative pressures—which is exactly why intraoperative pressures are recorded frequently. Our monitoring intervals were therefore appropriate for each period.

Our definitions of daytime and nighttime pressure and our approach to identification and exclusion of artefactual blood pressure readings followed international guidelines.10,11  The number of excluded artifacts during ambulatory blood pressure monitoring was well below accepted standards used to define “complete recording.”12 

In summary, our study methodology was sound and fully justifies our conclusion that preinduction mean arterial pressure cannot be used as a surrogate for the normal daytime mean arterial pressure, and that intraoperative mean arterial pressures are lower than the lowest nighttime mean arterial pressure in most patients.

Competing Interests

The authors declare no competing interests.

References

References
1.
Futier
E
,
Lefrant
JY
,
Guinot
PG
,
Godet
T
,
Lorne
E
,
Cuvillon
P
,
Bertran
S
,
Leone
M
,
Pastene
B
,
Piriou
V
,
Molliex
S
,
Albanese
J
,
Julia
JM
,
Tavernier
B
,
Imhoff
E
,
Bazin
JE
,
Constantin
JM
,
Pereira
B
,
Jaber
S
;
INPRESS Study Group
:
Effect of individualized vs standard blood pressure management strategies on postoperative organ dysfunction among high-risk patients undergoing major surgery: A randomized clinical trial.
JAMA
2017
;
318
:
1346
57
2.
Saugel
B
,
Reese
PC
,
Sessler
DI
,
Burfeindt
C
,
Nicklas
JY
,
Pinnschmidt
HO
,
Reuter
DA
,
Südfeld
S
:
Automated ambulatory blood pressure measurements and intraoperative hypotension in patients having noncardiac surgery with general anesthesia: A prospective observational study.
Anesthesiology
2019
;
131
:
74
83
3.
Palatini
P
,
Frigo
G
,
Bertolo
O
,
Roman
E
,
Da Cortà R
,
Winnicki
M
:
Validation of the A&D TM-2430 device for ambulatory blood pressure monitoring and evaluation of performance according to subjects’ characteristics.
Blood Press Monit
1998
;
3
:
255
60
4.
Banegas
JR
,
Ruilope
LM
,
de la Sierra
A
,
Vinyoles
E
,
Gorostidi
M
,
de la Cruz
JJ
,
Ruiz-Hurtado
G
,
Segura
J
,
Rodríguez-Artalejo
F
,
Williams
B
:
Relationship between clinic and ambulatory blood-pressure measurements and mortality.
N Engl J Med
2018
;
378
:
1509
20
5.
Whelton
PK
,
Carey
RM
,
Aronow
WS
,
Casey
DE
Jr
,
Collins
KJ
,
Dennison Himmelfarb
C
,
DePalma
SM
,
Gidding
S
,
Jamerson
KA
,
Jones
DW
,
MacLaughlin
EJ
,
Muntner
P
,
Ovbiagele
B
,
Smith
SC
Jr
,
Spencer
CC
,
Stafford
RS
,
Taler
SJ
,
Thomas
RJ
,
Williams
KA
Sr
,
Williamson
JD
,
Wright
JT
Jr
:
2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
J Am Coll Cardiol
2018
;
71
:
e127
248
6.
Ackland
GL
,
Brudney
CS
,
Cecconi
M
,
Ince
C
,
Irwin
MG
,
Lacey
J
,
Pinsky
MR
,
Grocott
MP
,
Mythen
MG
,
Edwards
MR
,
Miller
TE
;
Perioperative Quality Initiative-3 Workgroup; POQI Chairs; Physiology Group; Preoperative Blood Pressure Group; Intraoperative Blood Pressure Group; Postoperative Blood Pressure Group
:
Perioperative Quality Initiative consensus statement on the physiology of arterial blood pressure control in perioperative medicine.
Br J Anaesth
2019
;
122
:
542
51
7.
Bartels
K
,
Esper
SA
,
Thiele
RH
:
Blood pressure monitoring for the anesthesiologist: A practical review.
Anesth Analg
2016
;
122
:
1866
79
8.
Fonseca-Reyes
S
,
Forsyth-MacQuarrie
AM
,
García de Alba-García
JE
:
Simultaneous blood pressure measurement in both arms in hypertensive and nonhypertensive adult patients.
Blood Press Monit
2012
;
17
:
149
54
9.
Clark
CE
:
Difference in blood pressure measurements between arms: Methodological and clinical implications.
Curr Pharm Des
2015
;
21
:
737
43
10.
O’Brien
E
,
Parati
G
,
Stergiou
G
,
Asmar
R
,
Beilin
L
,
Bilo
G
,
Clement
D
,
de la Sierra
A
,
de Leeuw
P
,
Dolan
E
,
Fagard
R
,
Graves
J
,
Head
GA
,
Imai
Y
,
Kario
K
,
Lurbe
E
,
Mallion
JM
,
Mancia
G
,
Mengden
T
,
Myers
M
,
Ogedegbe
G
,
Ohkubo
T
,
Omboni
S
,
Palatini
P
,
Redon
J
,
Ruilope
LM
,
Shennan
A
,
Staessen
JA
,
vanMontfrans
G
,
Verdecchia
P
,
Waeber
B
,
Wang
J
,
Zanchetti
A
,
Zhang
Y
;
European Society of Hypertension Working Group on Blood Pressure Monitoring
:
European Society of Hypertension position paper on ambulatory blood pressure monitoring.
J Hypertens
2013
;
31
:
1731
68
11.
Parati
G
,
Stergiou
G
,
O’Brien
E
,
Asmar
R
,
Beilin
L
,
Bilo
G
,
Clement
D
,
de la Sierra
A
,
de Leeuw
P
,
Dolan
E
,
Fagard
R
,
Graves
J
,
Head
GA
,
Imai
Y
,
Kario
K
,
Lurbe
E
,
Mallion
JM
,
Mancia
G
,
Mengden
T
,
Myers
M
,
Ogedegbe
G
,
Ohkubo
T
,
Omboni
S
,
Palatini
P
,
Redon
J
,
Ruilope
LM
,
Shennan
A
,
Staessen
JA
,
vanMontfrans
G
,
Verdecchia
P
,
Waeber
B
,
Wang
J
,
Zanchetti
A
,
Zhang
Y
;
European Society of Hypertension Working Group on Blood Pressure Monitoring and Cardiovascular Variability
:
European Society of Hypertension practice guidelines for ambulatory blood pressure monitoring.
J Hypertens
2014
;
32
:
1359
66
12.
Muntner
P
,
Shimbo
D
,
Carey
RM
,
Charleston
JB
,
Gaillard
T
,
Misra
S
,
Myers
MG
,
Ogedegbe
G
,
Schwartz
JE
,
Townsend
RR
,
Urbina
EM
,
Viera
AJ
,
White
WB
,
Wright
JT
Jr
:
Measurement of blood pressure in humans: A scientific statement from the American Heart Association.
Hypertension
2019
;
73
:
e35
66