Comparison of temperature measurements in bladder, rectum and pulmonary artery in patients after cardiac surgery

doi:10.4236/ojn.2012.223045

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Open Journal of Nursing, 2012, 2, 307-310 OJN

http://dx.doi.org/10.4236/ojn.2012.223045 Published Online November 2012 (http://www.SciRP.org/journal/ojn/)

Comparison of temperature measurements in bladder,

rectum and pulmonary artery in patients after cardiac

surgery

Hendrika Wollerich, Farouq Ismael, Maarten W. Nijsten, Willem Dieperink

Department of Critical Care, University of Groningen, University Medical Center Groningen, Groningen, Netherlands

Email: [email protected]

Received 10 September 2012; revised 12 October 2012; accepted 25 October 2012

ABSTRACT

In many patients in the intensive care unit (ICU) con-

tinuous temperature monitoring is performed with

rectal probes. Currently there are more options to

measure temperature in critically ill patients. Since

bladder catheters are routinely used in the majority

of ICU patients, using bladder temperature (Tb)

could do away with rectal probes. In this prospective

study, we compared Tb, rectal temperature (Tr) and

pulmonary artery catheter temperature (Tpa) in pa-

tients who underwent cardiac surgery. We also eva lu-

ated if urinary production affected Tb. Patients ad-

mitted af ter cardiac surg ery with sensors in place for

measurement of Tr, Tb and Tpa upon arrival at the

ICU were included. Diuresis was recorded every hour.

Data were collected until 24 h after admission or until

ICU discharge. Nineteen consecutive patients (9 males;

mean age 61 years) were evaluated. Over a median

observation period of 17 hours 382 Tb, 333 Tr and

371 Tpa measurements were recorded. Linear corre-

lations (R) between Tb and Tr, between Tb and Tpa

and between Tr and Tpa were 0.95, 0.95 and 0.91 re-

spectively (P < 0.001). Bland-Altman analysis demon-

strated no relation between temperature and the (Tb-

Tr) offset. No relation of diuresis with (Tb-Tr) or

(Tb-Tpa) was observed. After cardiac surgery, blad-

der temperature performed as well as conventional

rectal probes with no interference of diuresis on blad-

der temperature measurement. Thus, the use of blad-

der temperature probes may be preferable to rectal

probes in patients after cardiac surgery.

Keywords: Intensive Care; Cardiac Surgery; Body

Temperature

1. INTRODUCTION

Accurate and precise measurement of body temperature

is important for in the timely detection of fever or hypo-

thermia in patients in the intensive care unit (ICU). No

uniform practice regarding temperature measurement

exists. A variety of devices are used to measure body

temperature at diverse anatomical locations in two possi-

ble temperature scales. Traditionally the temperature meas-

ured within the pulmonary artery (Tpa) with a the Swan-

Ganz catheter (PAC), that is typically only used in pa-

tients with complex hemodynamic problems, is consid-

ered the “gold standard” for the measurement of body

temperature [1].

Nevertheless, for routine clinical use in ICU patients,

using a PAC is clearly inapplicable.

In many ICU’s continuous rectal temperature meas-

urement (Tr) is standard practice [2]. Placement of ther-

mometers in the rectum is more invasive than in the

axilla or groin. A rectal probe can be distressing as well

as embarrassing for patients. Moreover, for inserting the

probe, patients must be placed on their side, a maneuver

that often requires two nurses to safely turn the patient.

The rectal temperature probe can also result in mucosal

injury, or even perforation of the rectum [3]. Tr can also

be affected by the passage of stools and the probe can

dislocate easily. On the other hand Tr is more accurate

than less invasive measurement methods such as at the

axilla or inguinal [4].

Urinary bladder temperature (Tb), measurement of

temperature with a specially designed temperature probe

embedded in a Foley urinary catheter, could be a favor-

able alternative to Tr in the ICU because rectal probe

insertion is not required without the need for additional

procedures [5,6]. In several patient groups it has been

established that Tb generally corresponds well to the Tpa,

the “gold standard” [7,8]. It has been suggested, that the

accuracy and precision of Tb might be influenced by the

urinary flow rate [5,9]. In 22 ICU patients in which tem-

perature was simultaneously monitored with PAC it has

been demonstrated that the reliability of Tb is higher than

either Tr or inguinal or axillary temperature measure-

ments [6,10].

OPEN ACCESS

H. Wollerich et al. / Open Journal of Nursing 2 (2012) 307-310

308

It is not known if the same holds true for the reliability

of Tb during the direct post-operative phase in patients

admitted after cardiac surgery. Cardiac surgery involves

the opening of the chest and frequently the use of a

heart-lung machine. Thus during and after such surgery

important swings in hemodynamics and temperature can

occur. This may be particularly relevant given the large

thermal gradients from core to periphery that occur dur-

ing anesthesia and cardiac surgery [5].

Objective

In a prospective study we tested the hypothesis that after

cardiac surgery Tb adequately reflects Tpa, and at least

as good as Tr. We also examined the effect of varying

urinary flow rate on the Tb.

2. METHODS

During a 10-month study period (June 2009 to March

2010) consecutive patients aged >18 years, who were

undergoing cardiac surgery and admitted to the depart-

ment of critical care were evaluated for this study. Pa-

tients, with a ileal conduit urinary diversion also known

as Bricker ileal conduit, or patients with suprapubic

catheters, or other patients where urethral catheterization

was contraindicated as well as patients who were under-

going renal replacement therapy were excluded.

Only patients with both a PAC, a urinary bladder

catheter with temperature probe (Tb) and a rectal tem-

perature probe (Tr) were included.

Tb was measured by a probe incorporated in a Foley

urinary catheter (DeRoyal, Powell, USA). Tpa was meas-

ured by a pulmonary artery catheter (PAC) (Edwards,

Irvine California). Tr was measured by a digital ther-

mometer probe (Esophageal/Rectal temperature probe

25˚C - 45˚C, Philips Medical Systems, Andover, USA)

designed for axillar and rectal use. The temperature sen-

sors and the PAC were respectively connected to a tem-

perature and cardiac output module of the bedside moni-

tor (MP70, Philips Medical Systems, Eindhoven, the

Netherlands). Temperature values were recorded in de-

grees Celsius every 30 minutes by the ICU nurses. The

urinary production in ml was recorded every hour. All

data were collected until 24 h after admission or until

ICU discharge if this took place within 24 h.

Tpa was considered the reference value. Thus Tb was

compared with Tpa, and Tr was compared with Tpa us-

ing regression and Bland and Altman analysis.

Since no additional interventions were performed in-

formed consent was not required for this anonymized

analysis of data. The institutional review board of the

University Medical Center Groningen approved this ob-

servational study (METc 2008/279).

3. RESULTS

During the study period, 19 consecutive patients admit-

ted to the department of critical care after cardiac surgery

were included. For 9 men and 10 women with a mean

age of 61 ± 13 (SD) years, we recorded temperatures

over a median observation period of 17 hours. A total of

382 Tb, 333 Tr and 371 Tpa measurements were ana-

lyzed (Table 1). We also recorded 291 diuresis meas-

urements.

Correlation coefficients between Tb and Tr, between

Tb and Tpa (Figure 1) and between Tr and Tpa were

0.95, 0.95 and 0.91 respectively (P < 10−9). The mean

offsets for expressed as (Tb-Tr), (Tb-Tpa) and (Tr-Tpa)

were −0.05˚C, +0.05˚C and +0.10˚C respectively, indi-

cating that Tr was the least reliable of the three meas-

urements.

Bland-Altman analysis demonstrated no relation be-

tween temperature and the (Tb-Tr) offset (Figure 2). No

relation of diuresis with (Tb-Tr) or (Tb-Tpa) was ob-

served. The two outlying values visible in Figures 1 and

2 concerned immediate post-operative patients with very

cold peripheries and consequently high temperature gra-

dients. For both these outliers Tr deviated more from Tpa

than Tb.

4. DISCUSSION

Measuring body temperature in critically ill patients is a

part of routine nursing care. However, it is still unclear

which method and device is ideal for measuring accurate,

reliable affordable, comfortable and safe body tempera-

ture. Nurses therefore must have the knowledge and

skills related to the various temperature measuring

Table 1. Patient characteristics.

Number of patients 19

Age, mean, SD, (range) 61.1 ± 13.4 (32 - 83)

Gender, male/female 9/10

Admission diagnoses:

Valve replacement, n (%)

CABG, n (%)

Cardiovascular other, n (%)

9 (47.3)

5 (26.3)

5 (30.3)

Height (cm), mea n , SD, (rang e ) 171.1 ± 8.2 (156 - 189)

Weight (kg), mean, SD, (range) 79.0 ± 16.2 (51 - 105)

BSA (m2), mean, SD, (range) 1.9 ± 0.2 (1.53 - 2.37)

APACHE IV score, me an, ±SD, (range) 44.8 ± 15.7

SAPS II score, mean, ±SD 30.5 ± 8.1

Diuresis, ml/hr, mean, ±SD, (range) 88 ± 79 (5 - 400)

SD = Standard Deviation, CABG = Coronary Artery Bypass Graft Surgery,

BSA = Body Surface Area, APACHE II = Acute Physiologic and Chronic

Health Evaluation, SAPS II = Simplified Acute Physiology Score.

H. Wollerich et al. / Open Journal of Nursing 2 (2012) 307-310 309

393837363534

PA C temperature

Bl a dder te mperatur e

Co rre la tion of bl a dder t e mpe ra tur e versus P A C te mpe ra tur e

R=0.95 (P<10-9)

Figure 1. Correlation plot of Tb versus Tpa showing high cor-

relation between the two temperature measuring methods.

393837363534

-1

-2

-3

MEAN OF BOTH METHO DS, degrees Celsius

DIFFERENCES BETWEEN METHODS, degrees Celsius

Blad der temperature versus PAC t emperature

Figure 2. Bland and Altman Plot of the data obtained from

paired samples of bladder and PAC temperature. Correlation R

= 0.95 (P < 10−9).

methods and associated devices to make good clinical

decisions. In the ICU, Tb measurement has gained in-

creased acceptance and is simplified by the fact that most

patients have an indwelling Foley catheter.

In many clinical studies Tpa is considered as the most

optimal representation of internal body temperature [8,

11,12]. However, for temperature measurement only, Tpa

is obviously not a practical technique as the invasive

pulmonary artery catheter is only required in a minority

of ICU patients. Inserting rectal thermometers is usually

uncomplicated, although it can occasionally cause mu-

cosal injury. However, these probes can be easily dislo-

cated by stool movements or by the application of sup-

positories and they are definitely associated with addi-

tional patient discomfort. At our ICU most patients have

bladder catheters, making the use of a catheter with an

incorporated temperature probe therefore not additionally

invasive. Thus Tb could be the preferred temperature

device in ICU patients.

The data in our study agree with those found in other

patient groups where neither Tb nor Tr exactly correlate

with Tpa [13-17]. However, bladder temperature gener-

ally did as well or better compared to Tr.

In spite of the fact that devices for Tb measurement

are more expensive than Tr devices, the overall costs for

Tb are lower because Tr probes must be changed more

often than Tb probes. Thus, although overall costs may

vary according to local circumstances, in our setting the

use of Tb is associated with reduced yearly cost decrease

of more than €4000 for our unit.

There are some limitations of the present study. First,

none of the CE-certified thermometers were tested or

compared with certified laboratory thermometers. On the

other hand, all equipment and materials in our hospital

are routinely monitored and checked regularly, and Tpa

is regarded as the gold standard.

Second, rectal temperature measurement could be af-

fected by the depth of inserting the probe, conditions

affecting local blood flow and the presence of stools.

These factors were not assessed in the our study since we

assumed that interference of stools or probe dislocation

would be less important, so early after insertion and sur-

gery. But if these factors come into play later on, we ex-

pect them to work particularly to the disadvantage of the

rectal temperature measurement, not the bladder meas-

urement.

And finally, we had a small number of measurements

in patients who were severely hypothermic or hyper-

thermic. Hence, further studies with larger sample sizes

including hypo and hyperthermic patients might further

strengthen the results of this study.

5. CONCLUSIONS

In conclusion, this study demonstrates that for post-

operative cardiac surgery patients, bladder temperature

measurement performs equal or better than rectal tem-

perature measurement. Diuresis did not interfere with

bladder temperature measurement.

We believe that both from the patient’s perspective

and from the nursing perspective, bladder temperature

measurement has sufficient advantages in terms of ac-

curacy, patient comfort and cost to be used in place of

the cumbersome rectal temperature measurements in

these patients.

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ABBREVIATIONS

CABG: Coronary artery bypass grafting;

ICU: Intensive care unit;

Tb: Bladder temperature;

Tpa: Pulmonary artery temperature;

Tr: Rectal temperature;

PAC: Pulmonary artery catheter;

SD: Standard deviation.