Evaluation of arterial oxygenation during anaesthesia

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - The clinical or physiological signs of hypoxaemia have limited value during anaesthesia. In the absence of surgical bleeding,...     

Alveolar recruitment strategy increases arterial oxygenation during one-lung ventilation

BACKGROUND: Deterioration of gas exchange during one lung ventilation (OLV) is caused by both total collapse of the nondependent lung and partial collapse of the dependent lung. A previous report demonstrated that an alveolar recruitment strategy (ARS) improves lung function during general anesthesia in supine patients. The objective of this article was to study the impact of this ARS on arterial oxygenation in patients undergoing OLV for lobectomies. METHODS: Ten patients undergoing open lobectomies were studied at three time points: (1) during two-lung ventilation (TLV), (2) during OLV before, and (3) after ARS. The ARS maneuver was done by increasing peak inspiratory pressure to 40 cm H2O, together with a positive end-expiratory pressure (PEEP) of 20 cm H2O for 10 respiratory cycles. After the maneuver, ventilation parameters were returned to the settings before intervention. RESULTS: During OLV, PaO2 was statistically lower before the recruitment (data as median, first, and third quartile, 217 [range 134 to 325] mm Hg) compared with OLV afterwards (470 [range 396 to 525] mm Hg) and with TLV (515 [range 442 to 532] mm Hg). After ARS, PaO2 values during OLV were similar to those during TLV. During OLV, the degree of pulmonary collapse in the nondependent lung, the hemodynamic status, and the ventilation parameters were similar before and after ARS. CONCLUSIONS: Alveolar recruitment of the dependent lung augments PaO2 values during one-lung ventilation.     

Effects of propofol vs sevoflurane on arterial oxygenation during one-lung ventilation

Background: The inhibitory effect of anaesthetic agents on hypoxic pulmonaryvasoconstriction may depend upon their dose, especially whenusing a volatile agent. The aim of this randomized open studywas to compare the effects of sevoflurane and propofol, as primaryanaesthetic agents, on oxygenation during one-lung ventilation(OLV), with their administration being adjusted to maintainbispectral index (BIS) values between 40 and 60. Methods: Eighty patients scheduled for a lobectomy, receiving an epiduralmixture of ropivacaine and sufentanil, were randomly assignedto Group S (maintenance with sevoflurane) or Group P (maintenancewith propofol). After placement of a double-lumen tube, thelungs were ventilated at an inspiratory fraction of oxygen of1.0, a tidal volume of 6 ml kg^–1, and 12 bpm. Arterialblood gas samples were taken as follows: during two-lung ventilationbefore OLV, and during the first 40 min of OLV. Results: Fifteen patients were excluded (incorrect placement of the tubeor BIS outside the desired range). The two groups were comparablein terms of demographic variables, haemodynamic, and BIS levelsduring the operation. Four patients in each group had a Sp_O2<90%.Mean of the lowest Pa_O2 was 16.3 (7.5) kPa in Group S and 17.7(9.3) kPa in Group P (ns). Conclusions: Sevoflurane and propofol had similar effect on Pa_O2 during OLVwhen their administration is titrated to maintain BIS between40 and 60.     

Progressive changes in arterial oxygenation during one-lung anaesthesia are related to the response to compression of the non-dependent lung

Background. Arterial oxygenation can change during one-lungventilation for reasons that are not fully understood. Methods. We studied patients during anaesthesia and one-lungventilation, with an inspiratory oxygen fraction of 0.8. Arterialblood gas values were recorded every 10 s with a continuousintra-arterial sensor. The non-dependent lung was compressedseveral times during the surgical procedure, using a retractor.The change in Pa_O2 during and after compression of the non-dependentlung was measured. Results. Pa_O2 increased significantly when the non-dependentlung was compressed, and decreased when the compression wasreleased. The first compression of the non-dependent lung transientlyincreased Pa_O2, but the effect of the second compression onoxygenation was more marked and persistent. Pa_O2 increased bymore than 13 kPa at 10 min after the second compression in fourpatients (responder group). Arterial oxygenation improved markedlyin patients in this group during the surgical procedure. Conclusion. Oxygenation can improve during one-lung ventilationin some patients. This improvement is partly related to a markedincrease in Pa_O2 during compression of the non-dependent lung. Br J Anaesth 2003; 90: 21–6     

'Alveolar recruitment strategy' improves arterial oxygenation during general anaesthesia

Abnormalities in gas exchange during general anaesthesia are caused partly by atelectasis. Inspiratory pressures of approximately 40 cm H2O are required to fully re-expand healthy but collapsed alveoli. However, without PEEP these re-expanded alveoli tend to collapse again. We hypothesized that an initial increase in pressure would open collapsed alveoli; if this inspiratory recruitment is combined with sufficient end-expiratory pressure, alveoli will remain open during general anaesthesia. We tested the effect of an 'alveolar recruitment strategy' on arterial oxygenation and lung mechanics in a prospective, controlled study of 30 ASA II or III patients aged more than 60 yr allocated to one of three groups. Group ZEEP received no PEEP. The second group received an initial control period without PEEP, and then PEEP 5 cm H2O was applied. The third group received an increase in PEEP and tidal volumes until a PEEP of 15 cm H2O and a tidal volume of 18 ml kg-1 or a peak inspiratory pressure of 40 cm H2O was reached. PEEP 5 cm H2O was then maintained. There was a significant increase in median PaO2 values obtained at baseline (20.4 kPa) and those obtained after the recruitment manoeuvre (24.4 kPa) at 40 min. This latter value was also significantly higher than PaO2 measured in the PEEP (16.2 kPa) and ZEEP (18.7 kPa) groups. Application of PEEP also had a significant effect on oxygenation; no such intra-group difference was observed in the ZEEP group. No complications occurred. We conclude that during general anaesthesia, the alveolar recruitment strategy was an efficient way to improve arterial oxygenation.      

Effects of thoracic epidural anaesthesia on pulmonary venous admixture and oxygenation during one-lung ventilation

BACKGROUND: In this clinical randomized study, the effects of four anaesthesia techniques during one-lung ventilation [total intravenous anesthesia (TIVA) with or without thoracic epidural anaesthesia (TEA) (G-TIVA-TEA and G-TIVA), isoflurane anaesthesia with or without TEA (G-ISO-TEA and G-ISO)] on pulmonary venous admixture (Qs/Qt) and oxygenation (OLV) were investigated. METHODS: In 100 patients (four groups, 25 patients in each) undergoing thoracotomy, a thoracic epidural catheter was inserted pre-operatively. In G-TIVA-TEA and G-ISO-TEA, bupivacaine 0.1% + 0.1 mg/ml morphine was administered intra-operatively (10 ml of first bolus + 7 ml/h infusion). Propofol infusion or isoflurane concentration was adjusted to keep a bispectral index (BIS) of between 40 and 50 in all groups. FiO(2) was 0.8 during OLV and 0.5 before and after OLV. Partial arterial and central venous oxygen pressures (PaO(2) and PvO(2)), arterial and venous oxygen saturations and Qs/Qt values were recorded before, during and after OLV. RESULTS: During OLV, PaO(2) was significantly higher and Qs/QT significantly lower in G-TIVA-TEA and G-TIVA compared with G-ISO-TEA and G-ISO (PaO2: 188 +/- 36; 201 +/- 39; 159 +/- 33; 173 +/- 42 mmHg, respectively; Qs/Qt: 31.2 +/- 7.4; 28.2 +/- 7; 36.7 +/- 7.1; 33.7 +/- 7.7%, respectively). No statistical changes were observed in patients with TEA compared with without TEA in any measurement. CONCLUSION: During OLV, TEA does not significantly affect the oxygenation and Qs/Qt and can be used safely regardless of whether TIVA or inhalation techniques are used.     

The improvement of arterial oxygenation during one-lung ventilation--effect of different CPAP levels.

Authors studied different continuous positive airway pressure (CPAP) levels and their effect on arterial oxygenation during thoracic surgery. Surgical interference of CPAP was studied as well. No significant difference has been found at 4 cm, 7 cm and 10 cm H2O in the improvement of oxygen content during one-lung ventilation. In contract to the lowest CPAP level, 7 cm and 10 cm H2O made the surgical conditions significantly worse.     

Variation in the arterial to end-tidal Pco2 difference during one-lung thoracic anaesthesia

We have measured the arterial to end-tidal PCO₂ difference (Pa_CO2– PE'_CO2) in 22 patients undergoing pulmonary resectionin the lateral thor-acotomy position during two-lung ventilation(TLV) and after transition to one-lung ventilation (OLV). WithOLV for each patient, the practice of correcting the estimateby an initial measurement of (Pa_CO2 – PE'_CO2) was evaluatedby subtracting the initial (Pa_CO2 – PE'_CO2) from subsequentvalues measured at 10-min intervals. Net (uncorrected) and correcteddifferences during OLV were analysed using ANOVA. (Pa_CO2 –PE'_CO2) values during TLV and OLV were similar: mean (SD) 1.3(0.6) kPa and 1.2 (0.7) kPa, respectively (ns). Mean (Pa_CO2– PE'_CO2) varied in the range 0.2–2.5 kPa, whilemaximum (Pa_CO2 – PE'_CO2) was 0.3–2.8kPa. The mean(SD) of 133 pairs of measurements with OLV was 1.1 (0.7) kPa.Even after correction, mean (Pa_CO2 – PE'_CO2) varied inthe range -0.7 to 0.8 kPa; individual extreme values were from-1.3 to 1.7 kPa. Variation between patients was found to begreater than variation within patients for both net and correcteddifferences (F ratio = 37.0 and 10.9, respectively), althoughcalculating a corrected difference did reduce variation betweenpatients from a mean square value of 2.44 to 0.61. The widevariation in (Pa_CO2 – PE'_CO2) suggests that the accuracyof estimation of Pa_CO2 by monitoring PE'_CO2 although improvedby the use of a corrected difference, remains questionable duringOLV. (Br. J. Anaesth. 1994; 72: 21–24)      

Effects of desflurane and propofol on arterial oxygenation during one-lung ventilation in the pig

Background: Desflurane depresses hypoxic pulmonary vasoconstriction (HPV) in vitro. During one-lung ventilation (OLV), HPV may reduce venous admixture and ameliorate the decrease in arterial O₂ tension by diverting blood from the non-ventilated to the ventilated lung. Accordingly, this study compares the effects of desflurane with those of propofol on oxygenation during two-lung (TLV) and OLV in vivo. Methods: Ten pigs (25–30 kg) were premedicated (flunitrazepam 0.4 mg/kg im), anaesthetized (induction: propofol 2 mg/kg iv; maintenance: N₂O/O₂ 50%/50%, desflurane 3%, propofol 50 μg kg^?1 min^?1, and vecuronium 0.2 mg kg^?1 h^?1 iv), orally intubated and mechanically ventilated. Femoral arterial and thermodilution pulmonary artery catheters were placed, and the orotracheal tube was replaced by a left-sided 28-Ch double-lumen tube (DLT) via tracheotomy. After DLT placement, N₂O and propofol were discontinued, FiO₂ was increased to 0.85, and anaesthesia continued randomly with either desflurane (1 MAC) or propofol 200 μg kg^?1 min^?1. Using a cross-over design, in each animal the effects of a), changing from TLV to OLV (left lung) during both desflurane and propofol and b), the effects of changing between the two anaesthetics during OLV were studied. Results: When changing from TLV to OLV, PaO₂ decreased more (P<0.05) during desflurane (mean 75%) than during propofol (mean 60%). Changing between desflurane and propofol during OLV resulted in small but consistent (P<0.05) increases in PaO₂ (mean 15%) during propofol. Conclusion: Consistent with in vitro results on HPV, 1 MAC desflurane impaired in vivo oxygenation during OLV more than did propofol.     

Effects of thoracic epidural meperidine on arterial oxygenation during one-lung ventilation in thoracic surgery

OBJECTIVE: To compare the effects that the use of general intravenous anesthesia (propofol-fentanyl) (GA) or general anesthesia combined with thoracic epidural anesthesia with meperidine (TEA-M) may have on arterial oxygenation during one-lung ventilation (OLV). DESIGN: Prospective. SETTING: Tertiary care hospital. PARTICIPANTS: Seventy-two patients undergoing OLV for thoracic surgery. INTERVENTIONS: Patients were prospectively randomized into two groups: GA (n = 37) fentanyl, propofol, rocuronium anesthesia was used; and group TEA-M (n = 35) were anesthetized with propofol, rocuronium and thoracic epidural meperidine (2 mg/kg in 10-12 mL) administered before anesthetic induction. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during study. Mean arterial pressure, heart rate and arterial and venous blood gases were recorded with the patients in the lateral decubitus position in three phases: during two-lung ventilation (TLV), 15 and 30 minutes after beginning OLV (OLV + 15 and OLV + 30 respectively). The authors measured arterial and venous central oxygen tension, arterial and venous central oxygen saturation, arterial and venous central oxygen content and venous admixture percentage (Qs/Qt%). MEASUREMENTS AND MAIN RESULTS: There were no statistical differences between the two groups for PaO(2) during OLV + 15 (GA = 165 mmHg, TEA-M = 153 mmHg) and OLV + 30 (GA = 176 mmHg, TEA-M = 158 mmHg); and with values for Qs/Qt%. CONCLUSIONS: It is concluded that GA combined with TEA-M (2 mg/kg) do not affect arterial oxygenation during OLV in thoracic surgery.