cc652 CCJ Meeting abstract <p>Jugular bulb desaturation during rewarming from cardiopulmonary bypass is influenced by isoflurane</p> Robson MJA Alston RP Andrews PYD Souter MJ

Department of Anaesthetics, Royal Infirmary of Edinburgh, Edinburgh, Scotland

 Critical Care <p>Autumn Scientific Meeting of the Association of Cardiothoracic Anaesthetists</p> Supported by an unrestricted educational grant from Bayer plc Meeting abstracts <p>Autumn Scientific Meeting of the Association of Cardiothoracic Anaesthetists</p> Glasgow, UK 19 November 1999 1364-8535 1999 4 Suppl A 1 17005034 10.1186/cc652 26 11 1999 23 12 1999 1999 Current Science Ltd cc-4-1-061-01

Introduction

Jugular bulb oxyhaemoglobin desaturation (SjO2≤ 50%) during the rewarming phase of cardiopulmonary bypass (CPB) is associated with postoperative cognitive deficits [1]. Isoflurane effects cerebral blood flow and cerebral metabolic rate, both of which affect SjO2 [2]. We report the effect of isoflurane on the incidence of desaturation during rewarming from CPB for coronary artery surgery.

Materials and methods

One hundred and nine men and 16 women of mean age 60 years (standard deviation 9 years) were studied. Isoflurane 1% was used on CPB for hypnosis in 61 patients and 64 received either propofol or a combination of morphine and midazolam. A catheter was positioned in the right jugular bulb. At 36°C, during rewarming, paired jugular bulb and arterial samples were taken for blood gas and SjO2 measurements. Nasopharyngeal temperature was measured throughout. SjO2 values were analyzed as measured and also after correction to an arterial carbon dioxide tension of 5.3 kPa. The number of patients who desaturated in each group was analyzed by χ2test and the mean differences in the variables by Student's t-test.

Results

Blood gas and blood pressure results are summarised in Table 1. Correcting for carbon dioxide significantly reduced the number of patients who desaturated in the morphine and midazolam group (25–4.7%, χ2 = 10.4; P < 0.01) but not the isoflurane group (4.9–1.6%; P > 0.2).

<p>Table 1</p>

Blood gas and blood pressure results

I group (n = 61)

NI group (n = 64)

P

SjO2 (%)

64.6 (9.5)

58.3 (11.6)

0.001

SjO2 carbon dioxide corrected (%)

70.6 (8.4)

63.5 (10.7)

0.001

SjO2≤ 50% (n)

3 (4.9%)

16 (25%)

<0.01

SjO2 ≤ 50% carbon dioxide corrected (n)

1 (1.6%)

3 (4.7%)

>0.2

PaCO2 (kPa)

4.49 (0.55)

4.59 (0.54)

0.286

MAP (mmHg)

58.8 (15.2)

64.5 (15.6)

0.065

Haemoglobin (g/dl)

8.3 (0.98)

8.6 (1.2)

0.258

SaO2 (%)

98.0 (0.6)

98.0 (0.5)

0.948

CPB (min)

88 (24)

86 (34)

0.661

Min temp CPB (°C)

31.0 (2.0)

30.9 (1.8)

0.797

Rewarm rate (°C/min)

0.21 (0.08)

0.26 (0.09)

0.001

Values are expressed as mean (standard deviation), unless otherwise indicated. CPB, cardiopulmonary bypass; I, isoflurane; MAP, mean arterial pressure; NI, morphine and midazolam; PaCO2, arterial carbon dioxide tension; SaO2, arterial oxygen saturation; SjO2, oxyhaemoglobin desaturation.

Conclusion

The incidence of desaturation during rewarming was significantly reduced by isoflurane. This suggests the balance between cerebral blood flow and cerebral metabolic rate during the rewarming phase of CPB is better preserved in the presence of isoflurane. Different arterial carbon dioxide tension levels cannot explain this effect, but the rate of rewarming may be one factor. Whether prevention of desaturation by isoflurane improves cognitive outcome is yet to be determined.

Acknowledgement

Funded by Wellcome Trust grant 050190.

 <p>Jugular bulb desaturation and cognitive dysfunction after cardiopulmonary bypass. </p> Croughwell ND Newman MF Blumenthal JA Ann Thorac Surg 1994 58 1702 1708 7979740 <p>Cerebral blood flow autoregulation is preserved during cardiopulmonary bypass in isoflurane-anesthetized patients.</p> Aladj LJ Croughwell ND Smith LR Anesth Analg 1991 72 48 52 10.1213/00000539-199101000-00008 1984375