Optimal perfusion during extra-corporeal circulation

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Optimal perfusion during extra-corporeal circulation ARTICLE in SCANDINAVIAN JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY · FEBRUARY 1987 DOI: 10.3109/14017438709106026 · Source: PubMed

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3 AUTHORS, INCLUDING: Henk M. Koning DC Klinieken 25 PUBLICATIONS 209 CITATIONS SEE PROFILE

Available from: Henk M. Koning Retrieved on: 05 February 2016

Scand J Thor Cardiovasc Surs 2l:207-213,1987

OPTIMAL PERFUSION DURING EXTRA-CORPOREAL CIRCULATION H. M. Koning,r A. J. Koning3 and J. J. A. M. Defauw2 From the Department of Anesthesiology , the 2Department of Thoracic Surgery, sDepartment of MedicaL St. Antonius Hospítal, NieuwegeinlUtrecht and the Informatics and Statistícs, Uníuersity of Limburg, 1

Maastricht, The NetherLands (Accepted for publicalon November 7, 1986)

Abstract. A multivariate analysis of 130 consecutive patients operated during one month in our hospital was carried out to determine the influence of age and blood flow during cardiopulmonary bypass on the renal response to cardiac surgery. The postoperative level of serum creatinine could be related to three variables: preoperative serum creatinine, age and lowest blood flow during cardiopulmonary bypass. A higher blood flow ts needed during cardiopulmonary bypass in older patients and in patients with a raised pre-operative serum creatinine to prevent deterioration in renal function postoperatively. A nomogram is given for the lowest blood flow during CPB, corrected for age and the pre-operative serum creatinine level, which will result in a desired postoperative serum creatinine of 110 u,mol/I.

Key words: extra-corporeal circulation, renal complications of cardiac surgery, cardiac surgery in older patients, blood flow during cardiopulmonary bypass.

The basic function of cardiopulmonary bypass (CPB) is to provide an adequate flow ofoxygenated blood to tissue in need (10) and to prevent damage to organs. One of the organs vulnerable to damage during perfusion is the kidney. The ideal blood flow

rate during CPB is still debated. Blood flow ts regarded as adequate if the rate is close to the patient's own prebypass cardiac output at normothermia. A normal cardiac output is 3.1 l/min/m2, yet a bypass blood flow of 2.2-2.4 l/min/m2 is generally considered to be an adequate and safe compromise (7, 10). Adjustment of the blood flow is advocated in relation to certain factors such as temperature and age.

The purpose of this study was to establish the renal response to cardiac surgery and to determine the influence of age and blood flow during CPB on changes in serum creatinine level during the first 24 hours after surgery.

METHODS

All patients undergoing cardiac surgery with CPB in our hospital during a one month period were included in the study. The operations performed are listed in Table I. Anesthesia was induced with diazepam (0.25-0.4 mg/kg i.v.), fentanyl (15-25 pg/kg i.v.) and pancuronium (0.1-{.15 mg/kg i.v.). Cefuroxim was administered as a routine prophylactic antibiotic- The electrocardiogram (lead II), a standard 16 lead electroencephalogram (EEG), arterial blood pressure and nasopharyngeal, rectal and blood temperatures were monitored continuously during the operation. For CPB a bubble oxygenator (Shiley Sl00A) primed with 1 I Haemaccel and 1 I Ringers acetate was used. The initial perfusion flow was ,2.4 llminlm2 body surface at normothermia and was adjusted to lower temperatures and at the request of the surgeon. The adjustment for hypothermia was minus 0.1 l/min/m'z for each degree decrease in nasopharyngeal temperature under 36"C. The blood flow pattern during CPB was non-pulsatile and the mean blood pressure was maintained at 4G-60 mmHg by means of nitroprusside. Cristalloid hypokalemic cardioplegia was used for cardioprotection. There was no routine administration of dopamine, diuretics or mannitol. Serum creatinine levels were determined the day before surgery and on the first postopertive day using a kinetic Jaffre reaction (I.L. 508).

Statístical methods Hemolysis was considered to be present if the free hemoglobin level in one of the samples taken during CPB exceed 20 prmol/I. The blood pressure recording was analysed for the length of time the systolic blood pressure was less than 100 mmHg before (RRt) or after (RR3) CPB and less than 50 mmHg during CPB (RRr). The lowest blood flow for a minimum of 5 min during CPB and the blood flow at the end of CPB were recorded. The Chi-square test was computed for dichotomous variables and the Wilcoxon rank sum test for continous variables. A p-value less than 0.05 was considered significant. For the multivariate analysis stepwise multiple linear regression was used (9). A description of the variables used for the analysis are given in Table II. Computations were made with the BMDP program. Scand

J Thor Cardiouasc 2l

208

H. M. Koning et al

Number oÍ

patients

30

20

10

-26.5

-52.5

-/ó.5

Changes

26

0

in serum ct eat

i

ni

.5

ne ( umol/

/ó. c

52.5 l

)

Fig. 1. Frequency distribution ofchanges in serum creatinine induced by open heart surgery.

RESULTS

In total,

130

patients were studied.

Uniuariate analysís The changes in serum creatinine are shown in Fig. 1. There was an approximately symmetric distribution around the zero value. Serum creatinine levels decreased in 59 patients (48%) and increased in 60

patients (49%).In 4 patients the serum creatinine level was unchanged. The patients with a decrease in serum creatinine level were compared with patients with an increase in serum creatinine level. The four patients with no change in serum creatinine level were excluded. Table III shows the results of the variables during CPB. None of these variables was statistically significant at the 0.05 level. Hemolysis during CPB was close to significance. Three patients had a free hemoglobin level exceeding 20 pmol/l and they all had a fall in serum creatinine postoperatively. Multiuariate analysís

By a stepwise regression technique a linear model

for postoperative serum creatinine with the variables pre-operative serum creatinine, age, lowest blood flow during CPB and blood flow at the end of CPB was selected. Table IV shows the result. An Scand

J Thor Cardiouasc 2l

iR' of 0.633 was found with the variables pre-opera-

tive serum creatinine, age and the lowest blood flow during CPB. However, when examining the residuals a linear model seemed inappropiate. Judged by a normal probability plot the distributron

of the residuals was skewed to the right, indicating that a multiplicative model could perform betterthan this additive model. We therefore applied a log transformation to the variable serum creatinine and the statistical analysis was repeated (Table V). Although a somewhat lower R2 of 0.57? was found, the normal probability plot of the residuals showed an almost straight line. Hence a linear model for the log transformed postoperative serum creatinine proved suitable. In neither model was the variable blood flow at

Table

I.

Operations performed

(CABG) lungsurgery surgery

Coronary artery bypass graft

combined with vascular- or combined with valve Valve surgery Single valve Double valve Tiiple valve Closure VSD

Total patients

99 3 6

t/ 2 2

I 130

Optimal perfusion during extra-corporeal Table

II. Description of the

circulatíon

209

uariables

Variable

Mean

S

Age (years) Pre-operative serum creatinine (trmol/l) Postoperative serum creatinine (pmol/l) Lowest blood flow during CPB (l/min/m'?) Blood flow at the end of CPB (l/min/m2)

58.6 107.8 t 10.2 .4 2.4

10.6 l. l 33.5 0.41 0.24

1

D

Range

3

25-17 50-3 16

62-256 0.0-2.3 1 .8-3.2

III. Statistical signíficance of the relationship between changes ín serum creatíníne und uariables during cardiopulmonary bypass Table

Changes in serum creatinine lncrease

Decrease

Variables

Duration of CPB (min) Duration of aorta clamping (min) Presence of hemolysis (%)

Hypotension

(min) (min) RRr (min) RR' RRz

Hypothermia Lowest blood temperature ("C) Lowest nasopharyngeal temperature ('C) Time nasopharyngeal temp.