The effects of intravenous almitrine on oxygenation and hemodynamics during one-lung ventilation

One-lung ventilation (OLV) induces an increase in pulmonary shunt sometimes associated with a decrease in PaO2 despite ventilation with 100% oxygen. PaO2 improvement has been reported in one-lung ventilated animals receiving IV almitrine, a pulmonary vasoconstrictor. We evaluated the ability of almitrine to prevent a decrease in PaO2 during OLV. Patients without pulmonary hypertension undergoing OLV for lung surgery were randomly assigned to receive either placebo (Group P, n = 8) or almitrine infusion at a rate of 8 microg x kg(-1) x min(-1) (Group A, n = 8) from the start of OLV. Gasometric and hemodynamic values were recorded with the patient in the lateral decubitus position during two-lung ventilation and at 10-min intervals during OLV over a 30-min period (OLV-10, OLV-20, OLV-30). Compared with the values found during two-lung ventilation (434 +/- 22 mm Hg in Group P and 426 +/- 23 mm Hg in Group A), PaO2 decreased at OLV-10 (305 +/- 46 mm Hg), OLV-20 (203 +/- 20 mm Hg), and OLV-30 (178 +/- 18 mm Hg) in Group P (P < 0.05) and at OLV-20 (354 +/- 25 mm Hg) and OLV-30 (325 +/- 17 mm Hg) in Group A (P < 0.05). PaO2 values differed between the groups at OLV-20 and OLV-30 (P < 0.05). Pulmonary artery pressure and cardiac output did not change. In conclusion, 8 microg x kg(-1) x min(-1) IV almitrine prevents and limits the OLV-induced decrease in PaO2 without causing any hemodynamic modification. IMPLICATIONS: Eight microg x kg(-1) x min(-1) IV almitrine limits one-lung ventilation-induced decrease in PaO2 without causing any hemodynamic modification in patients without pulmonary hypertension.     

Apnea-induced hemoglobin desaturation during one-lungvs two-lung ventilation

PURPOSE: To compare the rate of apnea-induced hemoglobin desaturation during one-lung ventilation (OLV) vs. two-lung ventilation (TLV) in patients undergoing thoracic surgery. METHODS: Six patients undergoing thoracotomy or thoracoscopy were included. Each patient served as his/her own control. The lungs were ventilated with oxygen 100% using TLV, followed after 20-30 min by OLV and the resultant PaO2 was measured. Apnea was then induced following the two techniques of ventilation, and the times for every 1% decrease in hemoglobin saturation from 100% to 95%, as monitored by pulse oximetry, were recorded. The times for every 1% decrease in the saturation were compared in the two groups. RESULTS: The mean PaO2 value following TLV (445+/-99 mm Hg) was higher than the mean PaO2 following OLV (156+/-18 mm Hg). Also, the mean time for subsequent apnea induced hemoglobin desaturation from SpO2 100% to 95% following TLV was twice the time of desaturation following OLV (6.3+/-1.2 min vs. 3.2+/-0.5 min, P<0.05). CONCLUSION: Hemoglobin desaturation occurs more rapidly during apnea following OLV than TLV. The rapid desaturation may be attributed to the decrease of FRC, associated with an increased transpulmonary shunting. The results suggest that two-lung ventilation with oxygen 100% provides a greater safety margin than one-lung ventilation with oxygen 100% whenever ventilation is interrupted.     

Halothane and isoflurane only slightly impair arterial oxygenation during one-lung ventilation in patients undergoing thoracotomy

Controversy exists as to whether the halogenated inhalation (IH) anesthetics impair arterial oxygenation during one-lung ventilation (1-LV). Accordingly, the authors have answered this question in 12 consenting patients who required 1-LV to facilitate the performance of thoracic surgery, by comparing arterial oxygenation during a prolonged period of IH anesthesia with arterial oxygenation during a prolonged period of intravenous (IV) anesthesia during stable 1-LV conditions. The patients were equally divided into halothane and isoflurane groups. Each patient in each IH anesthetic group underwent the following experimental sequence: step 1, two-lung ventilation (2-LV), 1 MAC IH anesthesia; step 2, 1-LV, 1 MAC IH anesthesia; step 3, 1-LV, iv anesthesia; step 4, 2-LV, iv anesthesia. Stable 1-LV conditions were proven by serial arterial blood gas measurement. Conversion from 2-LV to 1-LV during IH anesthesia (step 1 to step 2) caused a very large and significant decrease in PaO2 (from 484 +/- 49 to 116 +/- 61, and from 442 +/- 58 to 232 +/- 97 mmHg in the halothane and isoflurane groups, respectively) and increase in shunt (from 14 +/- 4 to 44 +/- 9, and from 19 +/- 5 to 31 +/- 8% in the halothane and isoflurane groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Lung recruitment improves the efficiency of ventilation and gas exchange during one-lung ventilation anesthesia

Atelectasis in the dependent lung during one-lung ventilation (OLV) impairs arterial oxygenation and increases dead space. We studied the effect of an alveolar recruitment strategy (ARS) on gas exchange and lung efficiency during OLV by using the single-breath test of CO(2) (SBT-CO(2)). Twelve patients undergoing thoracic surgery were studied at three points in time: (a) during two-lung ventilation and (b) during OLV before and (c) after an ARS. The ARS was applied selectively to the dependent lung and consisted of an increase in peak inspiratory pressure up to 40 cm H(2)O combined with a peak end-expiratory pressure level of 20 cm H(2)O for 10 consecutive breaths. The ARS took approximately 3 min. Arterial blood gases, SBT-CO(2), and metabolic and hemodynamic variables were recorded at the end of each study period. Arterial oxygenation and dead space were better during two-lung ventilation compared with OLV. PaO(2) increased during OLV after lung recruitment (244 +/- 89 mm Hg) when compared with OLV without recruitment (144 +/- 73 mm Hg; P < 0.001). The SBT-CO(2) analysis showed a significant decrease in dead-space variables and an increase in the variables related to the efficiency of ventilation during OLV after an ARS when compared with OLV alone. In conclusion, ARS improves gas exchange and ventilation efficiency during OLV. IMPLICATIONS: In this article, we showed how a pulmonary ventilatory maneuver performed in the dependent lung during one-lung ventilation anesthesia improved arterial oxygenation and dead space.     

Relation of the static compliance curve and positive end-expiratory pressure to oxygenation during one-lung ventilation.

BACKGROUND: Positive end-expiratory pressure (PEEP) is commonly applied to the ventilated lung to try to improve oxygenation during one-lung ventilation but is an unreliable therapy and occasionally causes arterial oxygen partial pressure (PaO(2)) to decrease further. The current study examined whether the effects of PEEP on oxygenation depend on the static compliance curve of the lung to which it is applied. METHODS: Forty-two adults undergoing thoracic surgery were studied during stable, open-chest, one-lung ventilation. Arterial blood gases were measured during two-lung ventilation and one-lung ventilation before, during, and after the application of 5 cm H(2)O PEEP to the ventilated lung. The plateau end-expiratory pressure and static compliance curve of the ventilated lung were measured with and without applied PEEP, and the lower inflection point was determined from the compliance curve. RESULTS: Mean (+/- SD) PaO(2) values, with a fraction of inspired oxygen of 1.0, were not different during one-lung ventilation before (192 +/- 91 mmHg), during (190 +/- 90), or after ( 205 +/- 79) the addition of 5 cm H(2)O PEEP. The mean plateau end-expiratory pressure increased from 4.2 to 6.8 cm H(2)O with the application of 5 cm H(2)O PEEP and decreased to 4.5 cm H(2)O when 5 cm H(2)O PEEP was removed. Six patients showed a clinically useful (> 20%) increase in PaO(2) with 5 cm H(2)O PEEP, and nine patients had a greater than 20% decrease in PaO(2). The change in PaO(2) with the application of 5 cm H(2)O PEEP correlated in an inverse fashion with the change in the gradient between the end-expiratory pressure and the pressure at the lower inflection point (r = 0.76). The subgroup of patients with a PaO(2) during two-lung ventilation that was less than the mean (365 mmHg) and an end-expiratory pressure during one-lung ventilation without applied PEEP less than the mean were more likely to have an increase in PaO(2) when 5 cm H(2)O PEEP was applied. CONCLUSIONS: The effects of the application of external 5 cm H(2)O PEEP on oxygenation during one-lung ventilation correspond to individual changes in the relation between the plateau end-expiratory pressure and the inflection point of the static compliance curve. When the application of PEEP causes the end-expiratory pressure to increase from a low level toward the inflection point, oxygenation is likely to improve. Conversely, if the addition of PEEP causes an increased inflation of the ventilated lung that raises the equilibrium end-expiratory pressure beyond the inflection point, oxygenation is likely to deteriorate.     

Perioperative transcutaneous oxygen monitoring in thoracic anaesthesia

Transcutaneous oxygen tension (PtcO2) was measured in 30 patients scheduled for elective pulmonary resection requiring one-lung ventilation during anaesthesia. Simultaneous PtcO2 and arterial oxygen tension (PaO2) measurements were taken preoperatively (preop), intraoperatively during two-lung endotracheal (ET) and one-lung endobronchial ventilation (EB), and postoperatively (postop). There was a significant correlation (r) between PtcO2 and PaO2 at all time periods: 0.97 (preop); 0.91 (ET); 0.83 (EB); 0.81 (postop). There were no significant differences among the transcutaneous oxygen indices (tcO2 index = PtcO2/PaO2) in the preop (0.69 +/- 0.09), ET (0.68 +/- 0.10) and postop (0.71 +/- 0.12) time period. The tcO2 index was significantly lower during one-lung anaesthesia (0.61 +/- 0.14). The PtcO2 was consistently lower than the corresponding PaO2 measurement, thus providing a continuous estimation of the "minimum" PaO2 level throughout anaesthesia and recovery. In four patients a marked drop in PtcO2 occurred just after the initiation of one-lung ventilation. In three, this was associated with arterial hypoxaemia and in one, haemodynamic compromise. In all four cases the PtcO2 was the first monitored parameter to change. As there is a substantial risk of developing hypoxaemia during thoracic anaesthesia, PtcO2 monitoring provides valuable early warning of impending hypoxaemia or haemodynamic compromise, thereby facilitating early therapeutic intervention.     

Arterial oxygenation during one-lung ventilation: combined versus general anesthesia

The optimal anesthetic management of patients undergoing thoracotomy for pulmonary resection has not been definitely determined. We evaluated whether general i.v. anesthesia (propofol-fentanyl) provides superior PaO2 during one-lung ventilation (OLV) compared with thoracic epidural anesthesia (TEA) with supplemental local and general anesthetics. We studied 60 patients who had prolonged periods of OLV for elective thoracic surgery for lung cancer and who were prospectively randomized into two groups. In 30 patients (GA group), fentanyl/propofol/rocuronium anesthesia was used. Another 30 patients (TEA group) were anesthetized with propofol/rocuronium/epidural thoracic bupivacaine 0.5%. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during the entire study. Arterial and venous blood gases were recorded before surgery in a lateral position with two-lung ventilation, 15 and 30 min after OLV (OLV + 15 and OLV + 30, respectively) in all patients. We measured PaO2, venous central oxygen tension, arterial and central venous oxygen saturation, venous admixture percentage (Qs/Qt%), and arterial and central venous oxygen content. The mean values for PaO2 during OLV in the GA group after 15 min (175 mm Hg) and 30 min (182 mm Hg) were significantly (P < 0.05) higher compared with the TEA group (120 and 118 mm Hg, respectively). Furthermore, Qs/Qt% was significantly (P < 0.05) increased in the TEA group during OLV. There were no other significant differences. We conclude that using the TEA regimen is associated with a lower PaO2 and a larger intrapulmonary shunt during OLV than with total i.v. anesthesia alone. IMPLICATIONS: Sixty patients undergoing elective lung surgery during a prolonged period of intraoperative one-lung ventilation were studied and randomized to receive general i.v. anesthesia or general i.v. anesthesia combined with thoracic epidural anesthesia. The arterial oxygenation in the first group was better than that in the second group during one-lung ventilation.     

A comparative evaluation of transcutaneous and end-tidal measurements of CO2 in thoracic anesthesia

We performed this study to assess the accuracy of transcutaneous CO(2) (PTCCO(2)) monitoring compared with end-tidal CO(2) (PETCO(2)) in thoracic anesthesia. Twenty-six patients undergoing pneumonectomy with thoracotomy for which a long period of one-lung ventilation (OLV) was required were studied. The lungs were mechanically ventilated in the lateral decubitus position. PTCCO(2), PETCO(2), and arterial CO(2) (PaCO(2)) were simultaneously measured during two-lung ventilation (TLV) and during OLV at intervals of 15 min. All patients completed the study protocol. Bland-Altman analysis revealed a bias of -0.4 mm Hg with a precision of +/-2.5 mm Hg during OLV and 1.4 mm Hg with +/-4.3 mm Hg during TLV when PTCCO(2) and PaCO(2) were compared and revealed a bias of -5.8 mm Hg with a precision of +/-4.1 mm Hg during OLV and -7.1 mm Hg with +/-4.6 mm Hg during TLV when PETCO(2) and PaCO(2) were compared. We conclude that PTCCO(2) monitoring is accurate for evaluating CO(2) levels during thoracic anesthesia.     

Two-lung and one-lung ventilation in patients with chronic obstructive pulmonary disease: the effects of position and F(IO)2

We compared the effects of position and fraction of inspired oxygen (F(IO)2) on oxygenation during thoracic surgery in 24 consenting patients randomly assigned to receive an F(IO)2 of 0.4 (eight patients, Group 0.4), 0.6 (eight patients, Group 0.6), or 1.0 (eight patients, Group 1.0) during the periods of two-lung (TLV) and one-lung ventilation (OLV) in the supine and lateral positions. TLV and OLV were maintained while the patients were first in the supine and then in the lateral position for 15 min each. Thereafter, respiratory mechanical data were obtained, and arterial blood gas samples were drawn. Pao2 decreased during OLV compared with TLV in both the supine and lateral positions. In all three groups, Pao2 was significantly higher during OLV in the lateral than in the supine position: 101 (72-201) vs 63 (57-144) mm Hg in Group 0.4; 268 (162-311) vs 155 (114-235) mm Hg in Group 0.6; and 486 (288-563) vs 301 (216-422) mm Hg in Group 1.0, respectively (P < 0.02, Wilcoxon's signed rank test). We conclude that, compared with the supine position, gravity augments the redistribution of perfusion as a result of hypoxic pulmonary vasoconstriction, when patients are in the lateral position, which explains the higher Pao2 during OLV. IMPLICATIONS: This study compares oxygenation during thoracic surgery during periods of two-lung and one-lung ventilation with patients in the supine and lateral positions when using three different fraction of inspired oxygen values. Arterial oxygen tension was decreased in all three groups during one-lung ventilation in comparison with the two-lung ventilation values, but the decrease was significantly less in the lateral, compared with the supine position.     

A comparison of enflurane and propofol in thoracic surgery

Comparisons between propofol and inhalational anesthetics for maintenance of anesthesia are limited. The purpose of our prospective study was to examine differences between enflurane and propofol during pulmonary resections with one-lung ventilation (1LV). METHOD. 28 patients, ASA risk group II-III, gave written informed consent for inclusion in this institutionally approved study. The patients were randomly allocated to one of the following groups: A: propofol 10 mg kg-1 h-1, B: 1 MAC enflurane, for maintenance of anesthesia. In both groups analgesia was achieved by fentanyl and muscle relaxation, by pancuronium. Ventilation via a double-lumen tube was controlled (FiO2 = 1.0, PaCO2 35-40 mmHg). Measurements, including hemodynamics and arterial and mixed venous blood gases, were obtained before induction (I), during two-lung ventilation (2LV) 15 min after induction in the supine position (II) and 20 min after surgical opening of the chest in the lateral decubitus position (III), 20 min after starting 1LV (IV), and after extubation (V). RESULTS. No significant differences between the two groups were found before induction (I), during 2LV (II, III), or after extubation (V). The only significant differences between the two groups were observed during 1LV (IV): the shunt fraction was 33.9 +/- 2.5% in A and 38.5 +/- 2.6% in B (P less than or equal to 0.05). Hypoxic pulmonary vasoconstriction was not inhibited in A, but was inhibited by 21.5% in group B during 1LV. Since no case of hypoxemia occurred in group A during 1LV (range of PaO2: 75.2-417.0 mmHg), but four patients developed hypoxemia in group B (Range of PaO2: 46.6-431.0 mmHg), regimen A might be of value in high-risk patients during thoracic surgery when 1LV is planned.     

A noninvasive partial carbon dioxide rebreathing technique for measurement of pulmonary capillary blood flow is also a useful oxygenation monitor during one-lung ventilation

STUDY OBJECTIVES: To test the hypothesis that effective pulmonary capillary blood flow can be a useful indicator for estimating appropriate oxygenation and ventilation during one-lung ventilation in lung surgery. DESIGN: Prospective data analysis. SETTING: A 770-bed general teaching hospital. PATIENTS: 15 ASA physical status II and III patients undergoing elective lung surgery. INTERVENTIONS: Patients received general and thoracic epidural anesthesia and underwent lung operation with one-lung ventilation. MEASUREMENTS: We measured effective pulmonary capillary blood flow by a partial CO2 rebreathing method and oxygenation parameters during two-lung ventilation before surgery, during one-lung ventilation, and during two-lung ventilation after lung surgery. MAIN RESULTS: The effective pulmonary capillary blood flow index significantly decreased by 31.6%, which was associated with a significant decrease in arterial oxygen tension (PaO2). The pulmonary shunt fraction increased to 46.3% during one-lung ventilation. During two-lung ventilation, after chest closure, effective pulmonary capillary blood flow index divided by heart rate (i.e., effective pulmonary blood stroke flow index) was still significantly lower than that seen during two-lung ventilation before thoracotomy. There were significant correlations between effective pulmonary capillary blood flow, pulmonary blood stroke flow index, and PaO2. CONCLUSIONS: Effective pulmonary capillary blood flow index and effective pulmonary blood stroke flow index are useful indicators for determining appropriate oxygenation therapy during one-lung ventilation.     

Predicting arterial oxygenation during one-lung anaesthesia

Eighty patients undergoing elective thoracotomy were studied to assess the possibility of predicting arterial oxygenation (PaO2) during one-lung anaesthesia (OLA). The first 50 patients were studied retrospectively. The method of multiple linear regression was used to construct a predictive equation for PaO2 during OLA. Potential predictors of PaO2 during OLA which were considered were: age, side of operation, preoperative pulmonary flow rates, preoperative and intraoperative PaO2 during two-lung ventilation. The three most significant predictors for PaO2 during OLA were: side right of operation (P < 0.05), preoperative FEV1% (P < 0.01) and intraoperative PaO2 during two-lung ventilation (P = 0.0001). The predictive equation for PaO2 after ten minutes of OLA was: PaO2 = 100 - 72 (side) - 1.86 (FEV1%) + 0.75 (two-lung) PaO2; (for side insert 0 for left-sided thoracotomy and 1 for right-sided thoracotomy). The remaining 30 patients were studied prospectively and the predicted PaO2 correlated with the observed PaO2 after ten minutes of OLA (r = 0.73, P < 0.01). Four of 30 patients had a predicted PaO2 at ten minutes of OLA < 150 mmHg. Of these, 2/4 subsequently required abandonment of OLA for pulse oximetric saturation < 85%. We conclude that although it is not possible to predict an individual patient's PaO2 during OLA with a high degree of accuracy, it is possible, before the initiation of OLA, to identify those patients whose arterial oxygenation is likely to decrease to low levels during OLA.     

Respiratory efficacy of subglottic low-frequency, subglottic combined-frequency, and supraglottic combined-frequency jet ventilation during microlaryngeal surgery

We tested the respiratory efficacy of different jet ventilation techniques (subglottic low-frequency versus subglottic combined-frequency and subglottic combined-frequency versus supraglottic combined frequency) in patients undergoing microlaryngeal surgery. The PaCO(2) and the quotient of arterial oxygen tension (PaO(2)) over FIO(2) were measured. After anesthetic induction (propofol, remifentanil, vecuronium), an endotracheal Mon-Jet catheter (Xomed, Jacksonville, FL) for subglottic jet ventilation and a laryngoscope for supraglottic jet ventilation (Carl Reiner G.m.b.H., Vienna, Austria) were inserted. In Group 1 (n = 18), subglottic low-frequency (15 breaths/min), combined-frequency (600 and 15 breaths/min), and low-frequency jet ventilation was subsequently performed (15 min each). In Group 2 (n = 19), the sequence was supraglottic, subglottic, and supraglottic combined-frequency jet ventilation. The driving pressures were initially adjusted to achieve normocapnia and were not changed during the entire study period. The FIO(2) was measured endotracheally. The Wilcoxon's signed rank test was applied. In Group 1, PaCO(2) and PaO(2)/FIO(2) improved significantly after switching from subglottic low-frequency to subglottic combined-frequency jet ventilation (PaCO(2), from 46.6 +/-8.3 to 42.1+/-8.1 mm Hg; PaO(2)/FIO(2), from 311+/-144 to 361+/-141 mm Hg; P<0.05). In Group 2, PaCO(2) increased and PaO(2)/FIO(2) decreased significantly after switching from supraglottic to subglottic combined-frequency jet ventilation (PaCO(2), from 39.4+/-7.1 to 45.9+/-7.5 mm Hg; PaO(2)/FIO(2), from 415+/-114 to 351+/-129 mm Hg; P<0.05). We conclude that subglottic combined-frequency jet ventilation is less effective than supraglottic combined-frequency ventilation, but more effective than subglottic low-frequency jet ventilation. Implications: The combination of high and low respiratory frequencies (600 and 15 breaths/min) improves pulmonary gas exchange during subglottic jet ventilation via an endotracheal catheter. However, subglottic combined-frequency jet ventilation is less effective than supraglottic combined-frequency jet ventilation via a jet ventilation laryngoscope.     

Small-dose nitric oxide improves oxygenation during one-lung ventilation: an experimental study

Inhaled nitric oxide (NO) at 20 or 40 ppm does not improve arterial oxygenation during one-lung ventilation (OLV). The authors hypothesized that NO at smaller concentrations might improve oxygenation. Twelve piglets weighing 26 to 32 kg were studied. When PaO(2) had reached a plateau during OLV, NO at doses of 4, 8, 16, and 32 ppm were randomly administered for 30 min. Hemodynamic data were determined by invasive monitoring. Blood gas analysis and, in six animals, ventilation-perfusion analysis by the multiple inert gas elimination technique were used to characterize pulmonary gas exchange. NO at 4, 8, 16, and 32 ppm improved PaO(2) during OLV. NO at 4 ppm had a more intense effect on arterial oxygenation than doses of 8, 16, and 32 ppm (DeltaPaO(2), 42 +/- 35 mm Hg versus 22 +/- 20 mm Hg, 13 +/- 18 mm Hg, and 15 +/- 16 mm Hg; P < 0.05). NO at 4 ppm reduced intrapulmonary shunt flow, whereas a larger concentration exhibited no statistically significant effect. The authors conclude that NO improves arterial oxygenation more effectively at smaller doses than at larger doses. This dose-dependent effect remains to be confirmed in acute hypoxemia during OLV. IMPLICATIONS: Inhaled nitric oxide at 4 ppm improves arterial oxygenation during one-lung ventilation to a greater extent than larger doses, and this effect is caused by a reduction in intrapulmonary shunt.     

"Best" PEEP during one-lung ventilation

Eight patients were studied under general anaesthesia for elective pulmonary lobectomy to see if intrinsic positive end-expired pressure (PEEPi) would appear or increase in the dependent lung during one-lung ventilation (OLV) or if application of external PEEP equal to individually measured PEEPi would produce better arterial oxygenation, haemodynamic state and oxygen delivery than either zero PEEP (ZEEP) or an external PEEP 5 cm H2O greater than PEEPi. Patients were non-obese, without obstructive airways disease, aged 53-76 yr and ASA < III. They received standardized anaesthesia with fentanyl, 50% nitrous oxide in oxygen and isoflurane; monitoring included radial and fibreoptic pulmonary arterial catheters and intermittent positive pressure ventilation with a tidal volume of 8 ml kg-1, 16 bpm, and an I:E ratio of 1:2. PEEPi was measured during two-lung ventilation (TLV) and OLV, using rapid airway occlusion at end-expiration. There was no PEEPi during TLV, but 2-6 mm Hg of PEEPi appeared during OLV. Applying external PEEP equal to individually measured PEEPi reduced venous admixture and increased PaO2 without a decrease in cardiac index (thus increasing oxygen delivery) compared with ZEEP, but the improvement in pulmonary gas exchange was lost and an additional penalty of reduced cardiac output was imposed when external PEEP was increased to 5 mm Hg above PEEPi.      

Experimental and clinical study of cardiopulmonary hemodynamics under one-lung ventilation during transthoracic esophagectomy]

Cardiopulmonary hemodynamics in pre- and postoperative period after transthoracic esophagectomy under one-lung ventilation (OLV) was investigated in experimental and clinical studies. In experimental study, 30 mongrel dogs were assigned to one of the groups: Group 1 (n = 10): 2 hour right thoracotomy alone under one (n = 5)- or two-lung ventilation (TLV) (n = 5), Group 2 (n = 10): thoracotomy + esophagectomy, Group 3 (n = 10): esophagectomy + right thoracic vagotomy. For further evaluation of the effect of vagotomy on increase of extravascular lung water (EVLW) on 3rd POD, the following 2 groups were designed as Group 4-1) (n = 5): thoracotomy + right thoracic vagotomy and Group 4-3) (n = 5): esophagectomy + left thoracic vagotomy. In clinical study, 30 patients underwent transthoracic esophagectomy were randomly divided into either OLV or TLV group. Cardiopulmonary hemodynamics and postoperative complications were investigated in pre- and up to 3 POD. 1. Cardiopulmonary parameters and EVLW except PaO2 and shunt ratio were not different between OLV and TLW groups in experimental study. PaO2 of OLV group dropped from the pre-thoracotomy value of 577 +/- 75 mmHg to 98 +/- 47 mmHg. This decrease was significant in comparison with TLV (582 +/- 85 mmHg to 215 +/- 132 mmHg) (p less than 0.05). Shunt ratio increased in the OLV group from 10 +/- 11% to 37 +/- 13%. This increase was also significant in comparison with TLV (24 +/- 10% from 9 +/- 9%) (p less than 0.05). However, both PaO2 and shunt ratio returned to the pre-thoracotomy value after stopping of OLV and showed no difference compared with TLV. 2. EVLW per kg was not different between 5 groups. Values of right to left lung ratio of EVLW in Group 3 and Group 4-3), 1.77 +/- 0.26 and 1.82 +/- 0.26, were greater than that in Group 1, 1.39 +/- 0.17 (p less than 0.05). This difference seems to be caused by increase of permeability of pulmonary capillaries. 3. Cardiopulmonary parameters and postoperative complications were not different between OLV and TLV groups in clinical study. In conclusion, OLV is a desirable procedure, not only for good exposure of the operative filed, but also for its safety regarding the cardiopulmonary hemodynamics. Transthoracic esophagectomy plus vagal branch denervation, which is necessary for aggressive lymphadenectomy around the trachea, increases EVLW and subsequent pulmonary edema compared with thoracotomy alone.     

Relation of the Static Compliance Curve and Positive End-expiratory Pressure to Oxygenation during One-lung Ventilation

Background : Positive end-expiratory pressure (PEEP) is commonly applied to the ventilated lung to try to improve oxygenation during one-lung ventilation but is an unreliable therapy and occasionally causes arterial oxygen partial pressure (Pao2) to decrease further. The current study examined whether the effects of PEEP on oxygenation depend on the static compliance curve of the lung to which it is applied.

Methods : Forty-two adults undergoing thoracic surgery were studied during stable, open-chest, one-lung ventilation. Arterial blood gasses were measured during two-lung ventilation and one-lung ventilation before, during, and after the application of 5 cm H2O PEEP to the ventilated lung. The plateau end-expiratory pressure and static compliance curve of the ventilated lung were measured with and without applied PEEP, and the lower inflection point was determined from the compliance curve.

Results : Mean (+/- SD) Pao2 values, with a fraction of inspired oxygen of 1.0, were not different during one-lung ventilation before (192 +/- 91 mmHg), during (190 +/- 90), or after ( 205 +/- 79) the addition of 5 cm H2O PEEP. The mean plateau end-expiratory pressure increased from 4.2 to 6.8 cm H2O with the application of 5 cm H2O PEEP and decreased to 4.5 cm H2O when 5 cm H2O PEEP was removed. Six patients showed a clinically useful (> 20%) increase in Pao2 with 5 cm H2O PEEP, and nine patients had a greater than 20% decrease in Pao2. The change in Pao2 with the application of 5 cm H2O PEEP correlated in an inverse fashion with the change in the gradient between the end-expiratory pressure and the pressure at the lower inflection point (r = 0.76). The subgroup of patients with a Pao2 during two-lung ventilation that was less than the mean (365 mmHg) and an end-expiratory pressure during one-lung ventilation without applied PEEP less than the mean were more likely to have an increase in Pao2 when 5 cm H2O PEEP was applied.     

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.     

Epidural block does not worsen oxygenation during one-lung ventilation for lung resections under isoflurane/nitrous oxide anaesthesia

BACKGROUND AND OBJECTIVES: The aim of this prospective, randomized, controlled clinical study was to evaluate the effects of thoracic epidural anaesthesia combined with isoflurane/nitrous oxide anaesthesia on intraoperative oxygenation during one-lung ventilation for lung resections. METHODS: Forty patients were randomly allocated to receive general anaesthesia maintained with isoflurane/nitrous oxide (group General, n = 20) or the same anaesthetic combined with thoracic epidural anaesthesia (group Integrated, n = 20). All patients were mechanically ventilated with the same settings (FiO2 = 0.5; VT = 9 mL kg(-1); inspiratory: expiratory time = 1:1; inspiratory pause = 10%). Effects on oxygenation were evaluated by determining the changes in PaO2/FiO2 ratio at 10, 30, 45 and 60 min of one-lung ventilation as compared to values obtained after induction of anaesthesia (supine, two-lung ventilation). RESULTS: The PaO2/FiO2 ratio was decreased in both groups during one-lung ventilation until the end of surgery. No differences were found at any observation time between the groups. Ventilation with 100% oxygen because of SpO2 decrease <92% was required in nine patients of group General (45%) and in eight patients of group Integrated (40%) (P = 0.64). Manual re-inflation of the operated lung was required in one patient of group General only (P = 0.99). Heart rate was lower in group Integrated than in group General throughout the study. No differences between the two groups in mean arterial pressure were observed. CONCLUSIONS: Adding a thoracic epidural block to isoflurane/nitrous oxide anaesthesia during one-lung ventilation for lung resections does not result in clinically relevant detrimental effects on intraoperative oxygenation.     

Supraglottic combined frequency jet ventilation versus subglottic monofrequent jet ventilation in patients undergoing microlaryngeal surgery

We compared the efficacy of gas exchange during supraglottic combined-frequency jet ventilation via a jet ventilation laryngoscope and during monofrequent jet ventilation via the Mon-Jet catheter (Xomed, Jacksonville, FL). Twenty-three anesthetized (propofol, fentanyl, vecuronium) patients undergoing microlaryngeal surgery were prospectively studied and randomly assigned to one of two groups. The patients' lungs were ventilated with combined-frequency jet ventilation (10 min, 15 and 600 breaths/min, inspiration/expiration time ratio = 1, driving pressure 750-1500 mm Hg), monofrequent (low-frequency group: 15 breaths/min; high-frequency group: 600 breaths/min) jet ventilation (20 min), and again combined-frequency jet ventilation (15 min). PaO(2), PaCO(2), and the inspiratory oxygen fraction (FIO(2)) were measured. Wilcoxon's signed rank test was applied. During monofrequent jet ventilation, PaCO(2) increased and the PaO(2)/FIO(2) decreased significantly (P < 0.05) as compared with combined-frequency jet ventilation (low-frequency group: PaCO(2) from 39.4 +/- 3.3 to 50. 8 +/- 8.0 mm Hg, PaO(2)/FIO(2) from 306 +/- 100 to 225 +/- 94 mm Hg; high-frequency group: PaCO(2) from 36.7 +/- 7.2 to 60.3 +/- 6.1 mm Hg, PaO(2)/FIO(2) from 429 +/- 87 to 190 +/- 51 mm Hg; mean +/- SD). After switching back to combined-frequency jet ventilation, PaCO(2) decreased and PaO(2)/FIO(2) increased to baseline levels. We conclude that gas exchange during microlaryngeal surgery can be more easily maintained with supraglottic combined-frequency jet ventilation than with subglottic monofrequent jet ventilation via the Mon-Jet catheter. IMPLICATIONS: This study demonstrates that the combination of high- and low-frequency supraglottic jet ventilation via a jet ventilation laryngoscope provides a better pulmonary gas exchange and allows more accurate airway pressure monitoring during microlaryngeal surgery than subglottic monofrequent jet ventilation via an endotracheal catheter.