Under physiological conditions, peripheral blood flow – peripheral perfusion, is mainly regulated by the autonomic nervous system. The lack of or compromised regulation results in vasodilation and increased flow through the tissues and organs, which is most commonly present  during subarachnoid and epidural anaesthesia. Moreover, it occurs during general anaesthesia when direct effects of anaesthetics on peripheral vessels are observed [1, 2, 3, 4].

Peripheral perfusion can be objectively assessed using new-generation pulse oximeters, based on spectrophotometry and the phenomenon of different absorption of light waves of various lengths by haemoglobin and tissues. The number of wave lengths generated by them is much higher compared to older devices, thus more accurate measurements and more information are provided, e.g. concerning the presence of the forms of haemoglobin other than oxy- and desoxyhaemoglobin. Light waves sent by the device permeate the distal body parts and are differently absorbed in a pulsatile manner by the flowing blood (AC – alternating compartment) or in a non-pulsatile manner by various tissues (DC – direct compartment). Based on this phenomenon, values of peripheral tissue perfusion may be accurately determined and expressed as the perfusion index (PI) calculated according to the formula: PI = AC/DC x 100% and displayed on the pulse oximeter screen in digital forms.

The objective of the present study was to determine the range of changes in peripheral blood flow during general anaesthesia with desflurane for gynaecological laparoscopic procedures and to define the relation between the perfusion index and the depth of hypnosis during anaesthesia.

METHODS

The study, approved by the Bioethics Committee of the Medical University of Lublin, encompassed female patients meeting ASA I and II criteria scheduled for elective gynaecological laparoscopic procedures.

All patients were premedicated with oral diazepam 10 mg two hours before the procedure; 5 min before the induction of anaesthesia they received iv fentanyl 5 µg kg-1 and atropine 0.5 mg. Anaesthesia was induced with thiopentone 5 mg kg-1 and suxametonium 1 mg kg-1. Patients were intubated and artificial lung ventilation was initiated with the respiratory parameters suitable to obtain normal ETCO2 values. Anaesthesia was maintained with the mixture of N2O and O2 (FIO2=0.33), 3-6% desflurane and fractionated doses of fentanyl 1.5 µg kg-1.
Muscle relaxation was provided using cisatracurium 0.05 mg kg-1. After surgery the neuromuscular block was reversed with neostigmine 2.5 mg preceded by atropine 0.5 mg. Before the completion of anaesthesia patients received ketonal 100 mg. During the entire procedure 500-1000 mL of electrolyte fluids was infused to maintain the peripheral intravenous access patent.

Standard monitoring during anaesthesia included: HR, SAP/DAP, SpO2, ETCO2 and ETdesflurane. Additionally, the peripheral index (PI) was recorded using the Radical 7 pulse oximeter (Masimo Corp., USA) and the depth of hypnosis was assessed using the A-line autoregressive index (AAI) by the AEP Monitor/2 (Danmeter, Denmark).

Measurements were recorded at the following procedure points: 1 – before anaesthesia (baseline values), 2 – after fentanyl injection, 3 – after intubation, 4 – at the beginning of procedure, 5-10 – every 10 min during the procedure, 11 – at the end of procedure, 12 – after eye opening, 13 – after extubation, 14 – on discharge to the ward.

Results were presented as means and SD. Differences in means were tested using the Student’s t-test for normal distribution; in the remaining cases, the Wilcoxon signed-rank test was applied. Correlations were analysed using the Spearman correlation coefficient. In all the tests, p<0.05 was considered significant.

RESULTS

The study involved 45 patients aged 37.0±13.8 years weighing 67.7±13.84 kg. The duration of surgery was 56.6±36.9 min and of anaesthesia 75.0±33.7 min. The most common procedures were salpingoplasty and ovarian surgery.

The induction of anaesthesia resulted in increased PI. Increased PI values were also observed during the maintenance of anaesthesia. There was a strong negative correlation between PI and AAI (r=-0.908; p=0.00000). Moreover, a strong positive correlation between PI and end-tidal desflurane concentration (r=+0.757; p=0.002) as well as a negative correlation between AAI and end-tidal desflurane concentration (r=-0.788; p=0.0008) were demonstrated (Fig. 1).

SAP was found to be significantly decreased compared to baseline values at the beginning of surgery and during the procedure. Significant differences in DAP were observed during intubation, at the beginning of surgery and during awakening (Fig. 2).

During the induction of anaesthesia and awakening of patients a significant increase in HR was observed, which was associated with the use of atropine. Differences in SpO2 during anaesthesia were not significant (Fig. 3).

DISCUSSION

One of the key goals of haemodynamic monitoring should be early detection of improper tissue flow. Thanks to new-generation pulse oximeters, this can be achieved using non-invasive measurements of peripheral perfusion index.

The maintenance of proper blood flow through the tissues is essential for homeostasis during surgery and anaesthesia as well as in ITU patients. The blood flow through the tissues depends on the vascular wall tone [5] yet is also modified by many other factors, including pain stimuli [6, 7]. Pain, which accompanies any tissue damage, including surgical injury, induces the appropriate response of the organism, e.g. increased concentration of circulating catecholamines, which leads to contraction of blood vessels. This unfavourable response should be neutralized during surgery by suitable anaesthesia. Too light anaesthesia in cases of nociceptive stimulation does not show protective effects and under such circumstances, the peripheral blood flow significantly changes [7]. Our study demonstrates a negative correlation between the degree of CNS depression (depth of hypnosis) of anaesthetised patients and PI, which supports the thesis about the necessity to maintain proper depth of anaesthesia.

Due to varied pharmacokinetic properties of individual general anaesthetics, the regional blood flow is differently affected by them both in experimental animals [3] and humans [4, 8]. It has been demonstrated that sevoflurane improves the blood flow in microcirculation [9] while propofol does not show such effects [10, 11]. Moreover, rapid changes in isoflurane or sevoflurane levels in the respiratory mixture result in various changes in the concentration of blood circulating catecholamines  [12, 13]. Both agents administered in the dose of 1 MAC do not completely block the vasomotor response to adrenergic stimuli [14]. Furthermore, our findings show that desflurane used suitably to patient’s needs has beneficial effects on tissue perfusion and that such effects correlate with the dose used. The relation between PI and anaesthetic dose has also been documented in other studies [9, 15].

Intraoperative monitoring of the highest possible number of physiological parameters determines the quality and safety of anaesthesia. The recent advances in this field resulted in wide introduction of devices for monitoring CNS functions. The devices for assessment of the depth of anaesthesia are being continuously studied and discussed [16]. Suitable depression of brain functions during general anaesthesia does not mean that all physiological parameters remain in the normal range, including the blood flow through tissues and their proper oxygenation. For these reasons, continuous intraoperative analysis of PI complements the methods for objective assessment of the quality of anaesthesia presently applied. The documented correlation between PI and oxygen supply to the tissues [17] also encourages us to use this method for monitoring the condition and treatment of ITU patients [18]. Furthermore, the method in question was demonstrated to be useful for verification of the efficacy of thoracic sympathectomy in
surgical treatment of hyperhidrosis [19].

CONCLUSIONS

1. General anaesthesia with desflurane increases peripheral blood perfusion.

2. Peripheral blood perfusion correlates with the depth of general anaesthesia maintained with desflurane. 

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REFERENCES

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16.    Rudner R, Jałowiecki P, Kawecki P: Anestezjjologia a nowoczesne techniki elektroencefalograficzne. Anaesthesiology Intensive Therapy 2001; 33: 253-260.

17.    Zaramella P, Freato F, Quaresima V, Ferrari M, Vianello A, Giongo D, Conte L, Chiandetti L: Foot pulse oximeter perfusion index correlates with calf muscle perfusion measured by near – infrared spectroscopy in healthy neanates. J Perinatology 2005; 25: 417-422.

18.    Lima AP, Beelen P, Bakker J: Use of a peripheral perfusion index derived from the pulse oximetry signal as a noninvasive indicator of perfusion. Crit Care med 2002; 30: 1210-1213.

19.    Klodell CT, Lobato EB, Willert JL, Gravenstein N: Oximetry – derived perfusion index for intraoperative identification of successful thoracic sympathectomy. Ann Thorac Surg 2005; 80: 467-470.

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Address:

*Anna Fijałkowska
Klinika Anestezjologii
i Intensywnej Terapii
UM w Lublinie
ul. Jaczewskiego 8, 20-950 Lublin
tel.: 0-81 724 43 32
e-mail: afijal@poczta.onet.pl

Received: 20.11. 2009
Accepted: 02.02.2010