The outcome of thoracic epidural anesthesia in elderly patients undergoing coronary artery bypass graft surgery.

BACKGROUND: Thoracic epidural anesthesia (TEA) improves analgesia and outcomes after a cardiac surgery. As aging is a risk factor for postoperative pulmonary complications, TEA is of particular importance in elderly patients undergoing coronary artery bypass graft (CABG).
METHODS: Fifty patients aged 65-75 years; ASA II and III scheduled for elective CABG were included in the study. Patients were randomized to receive either general anesthesia (GA) group alone or GA combined with TEA group. Heart rate (HR), mean arterial pressure (MAP), and central venous pressure were recorded. Total dose of fentanyl μg/kg, aortic cross clamping, cardiopulmonary bypass (CPB) time, time to first awaking and extubation, arterial blood gases, visual analog scale (VAS) score in intensive care unit were reported. Postoperative pulmonary function tests were done.
RESULTS: TEA showed a significant HR and lower MAP compared with the GA group. The total dose of intraoperative fentanyl and nitroglycerine were significantly lower in the TEA. Patients in TEA group have statistically significantly higher PaO(2), lower PaCO(2), increase in Forced Vital Capacity (FVC) and Forced Expiratory Volume in one second (FEV(1))
CONCLUSIONS: TEA reduced severity of postoperative pulmonary function and restoration was faster in TEA group in elderly patients undergoing CABG. Also, it resulted in earlier extubation and awakening, better analgesia, lower VAS.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Aging is a risk factor for postoperative atelectasis, which accounted for the highest incidence of postoperative pulmonary complications in coronary artery bypass graft (CABG) surgery patients.[1]

The potential benefit of high thoracic epidural anesthesia (TEA) in patients undergoing CABG surgery are well documented[2] because of its beneficial effects on the perioperative stress response, analgesia, and postoperative pulmonary function.[3]

Significant impairment of pulmonary function is common after cardiac surgery and is multifactorial in origin. Median sternotomy leads to uncoordinated rib cage expansion and respiratory muscle weakness.[4] Basal atelectasis, which occurs after induction of general anesthesia, may persist into the postoperative period and is characterized by increased ventilation perfusion (V/Q) mismatch.[5]

TEA for these patients may offer a distinct effect on hemodynamics, such as pain control without sedation, reduction in stress response, faster extubation and mobilization, decreased of deep vein thrombosis, and good patient acceptance.[2] TEA attenuates postoperative pulmonary complications that follow thoracic surgeries.[4] TEA improves the FVC and FEV1 following thoracotomy.[6] To the best of our knowledge, there are no reports on elderly patients undergoing CABG. This study was done to determine the beneficial effects of TEA on pulmonary function in elderly patients undergoing CABG surgery.

METHODS

Approval of the institutional ethics committee and written informed consent were obtained from all patients. Fifty patients between 65 and 75 years with physical status of ASA II and III scheduled for elective CABG were included in the study. Patients were randomly enrolled (sealed envelope) to receive either general anesthesia (GA group) alone or GA combined with TEA (TEA group).

Preoperative documentation of a normal prothrombin time (PT) and a partial thromboplastin time (PTT) were required. Antiplatelet therapy was withdrawn 1 week before surgery. Exclusion criteria were local infection at the site of puncture or septicemia, pre-existing coagulopathy, redo open heart surgery, endocarditis, neurologic disorder, hepatic disease, pulmonary disease, heart failure. Upon arrival in the operating room, all the patients had an intravenous catheter (18G) inserted in a large antecubital vein and they received ringers’ solution (4–6 ml/kg/h), ECG, peripheral oxygen saturation SPO2 and noninvasive blood pressure were monitored (Kontron Kolorman, Model Number 7550, Italy). Supplemental oxygen was provided via a face mask. Patients were then premedicated with midazolam 0.05 mg/kg and tramadol 1–2 mg/kg IV under local anesthesia with 2% lidocaine arterial line was inserted in radial artery under complete aseptic technique, also right internal jugular vein or subclavian vein was canulated under local anesthesia with 2% lidocaine and complete aseptic technique. In the TEA group, epidural catheter was inserted through an 18G needle into the epidural space at least 2 h before heparinization at a thoracic interspace between T4 and T5, using loss of resistance technique. If blood was returned during epidural catheter placement, the epidural needle and catheter were removed and placed at T3–T4 or T5–T6 interspace. After a negative epidural test dose of 3 mL 1.5% lidocaine the epidural catheter was injected with 0.125% bupivacaine with 1 μg/mL fentanyl at a rate of 5 m/h and was continued till 24 h postoperative. Epidural block was tested by loss of sensation to cold and pinprick. Epidural catheter was removed on the postoperative day where there is no clinical evidence of bleeding. In both groups, general anesthesia was induced in all patients with fentanyl 10 μg/kg, thiopental 2–3 mg/kg and pancronium 0.1 mg/kg for muscle relaxation and tracheal intubation. Patients were mechanically ventilated with 100% O2 and the endtidal CO2 was monitored by main stream capnography and maintained between 30 and 35 mmHg. Anesthesia was maintained with sevoflurane, incremental doses of fentanyl (1 μg/kg) to maintain heart rate (HR) and blood pressure within 20% of the basal value with a maximum dose 20 μg/kg and incremental doses of pancronium to maintain muscle relaxation. Normothermic cardiopulmonary bypass graft (CPBG) with a membrane oxygenator was used in all the patients. Anticoagulation with heparin 300–400 IU/kg to maintain an activated coagulation time >480 s. After aortic cross clamping, all the patients received cold blood cardioplegia. Cardioplegia was delivered 20 mL/kg for the first dose and 10 mL/kg for the subsequent doses in antegrade manner in aortic root. Surface cooling using packed iced saline was used. Cardioplegia was repeated every 30 min. Anesthesia was maintained on CPB by propofol infusion 200 mg in 100 mL dextrose 5% in a dose of 50–200 μg/kg/min after adding 2 mg/kg to the CPB prime. Heparin anticoagulation was reversed with protamine at the end of CPB. In the intensive care unit (ICU), the patients were ventilated with a servo-ventilated. They received as needed, tramadol 1–2 mg/kg IV; they were warmed with a warming blanket until central temperature was 37°C.

Extubation criteria included an adequate level of consciousness and muscle strength, stable cardiovascular status, normothermia, adequate pulmonary function (PaO2>80 mmHg with fraction of inspired oxygen ≤0.4) and minimal thoracotomy tube output.

Both groups received tramadol IV on demand for pain relief during the first 24 h after surgery and recorded.

Data recorded

Hemodynamic: HR, mean arterial pressure (MAP), and central venous pressure (CVP), were recorded at the following time intervals: Before induction of anesthesia (basal), after skin incision, poststernotomy, 5 min before CBP, 5 min after CBP, after closure of sternum, postoperative: Each 3 h after admission to ICU for 24 h.

Operative parameters: Total dose of fentanyl μg/kg, aortic cross clamping (min), CPB time (min), duration of surgery, warming off CBP parameters (spontaneous recovery of the heart, need for DC shocks, and the inotropic (dopamine) and/or vasodilator (nitroglycerine) requirements (μg/kg/min) to wean the heart from CPB.

ICU parameters: Time to first awaking and extubation, arterial blood gases, visual analog scale (VAS) score on the postextubation, 12, 24 h postoperative, tramadol consumption in the first 24 h in ICU, and ICU length of stay.

Postoperative: Nausea and vomiting, pruritus respiratory depression, and neurologic deficit were recorded.

Pulmonary function tests were done using PC card spirometer, manufactured by Medical Graphico Corporation(St. Paul, MN 55127 U.S.A.), according to American Thoracic Society recommendation, during preoperative assessment, at 6 and 24 h postextubation and on the postextubation days 2, 3 along with arterial blood gas analysis.

The statistical analysis of data was done using excel program and SPSS program statistical package for social science version 17 (SPSS Inc., San Francisco, CA, USA). To test the normality of data distribution Kolmogorov–Smirnov test was done. Normally distributed data were subjected to parametric tests. A paired t test was used to compare within group, while an independent t test was used for comparison between groups. P value <0.05 was considered as significant.

RESULTS

Patients in both the groups were comparable with regard to demographic data, number of grafts, and time of surgery [Table 1]. The MAP was significantly lower in the TEA group than in the GA group 5 min before CPB, 5 min after CBP, after closure of sternum. Also, HR was significantly lower (P<0.05) in the TEA 5 min after CPB and after closure of sternum in comparison with the GA group. Postoperative HR and MAP were significantly lower (P<0.05) in the TEA when compared with the GA group throughout the postoperative period [Figures 1 and 2]. Perioperative CVP showed no significant differences between both the groups [Figure 3].

Table 1

Demographic data of patients and duration of surgery

Figure 1

Perioperative heart rate changes (beat/min)

Figure 2

Perioperative mean blood pressure changes

Figure 3

Perioperative central venous pressure changes

The total dose of intraoperative fentanyl and nitroglycerine were significantly lower in the TEA than in the GA group. However, the total dose on intraoperative dopamine was significantly higher in the TEA than in the GA group [Table 2]. The operative parameters (bypass time aortic cross clamping time and need for DC shock showed insignificant differences between the studied groups [Table 2]. VAS was statistically significantly lower in the TEA than in the GA group at postextubation, 6, 12, and 24 h postoperative [Table 3]. Rescue analgesia used in the ICU was significantly lower in the TEA than in the GA group [Table 4].

Table 2

Intraoperative variables

Table 3

Visual analog score

Table 4

Intensive care unit parameters

Basal ABG values were similar in both groups but after extubation, patients in the TEA group have statistically significantly higher PaO2 and lower PaCO2 than in the GA group [Table 5].

Table 5

Perioperative arterial blood gases

In both the groups, there was a significant decrease in forced vital capacity (FVC) Volume in one second, forced expiratory flow (FEF), and peak expiratory flow rate (PEFR) at 6, 12, and 24 h postoperatively when compared with the basal value in each group [Table 6]. However, there was a significant decrease in FVC and FEV1 in GA group at 6 h, 12 h and 24 postoperatively when compared with TEA group. Also, the percentage change from base line vales of FVC and FEV1, FEF, PEFR at 6, 12, and 24 h postoperatively showed a significant decrease in GA group when compared with TEA group. There were no significant differences in FEV/FVC in both groups [Table 6]. With regard to ICU parameters, time to first awakening and to extubation was significantly lower in TEA group than the GA group. Total doses of tramadol given in the ICU were significantly lower in the TGA group than in the CA group. But nausea and vomiting and pruritus were significantly higher in the TGA group than in the GA group. There were no significant differences with regard to ICU and hospital length of stay between the TEA group and the GA group [Table 4].

Table 6

Pulmonary functions tests

DISCUSSION

TEA improves the pulmonary dynamics after thoracotomy, thoracic trauma, and upper abdominal trauma.

Possible mechanisms include direct action on vital capacity, which permits better spontaneous ventilation. Analgesia without sedation helps in rapid mobilization and active pulmonary rehabilitation.[2] The present study showed that HR and mean arterial blood pressure, both intra-and postoperative, were significantly lower in TEA group than the control group. This is in accordance with previous studies.[7] Stenseth et al. found that the HR and arterial pressure were significantly lower following epidural analgesia than intravenous opioid with fentanyl in patients submitted for CABG surgery.[8] In contrast to our results, Fillinger et al.,[9] found no significant difference in HR and mean blood pressure between combined GA and TEA groups and GA group alone. This may be explained by the aggressive use of a wide variety of effective interventions to treat unfavorable measured changes in cardiovascular function. Also, Mehta et al.[2] and Salvi et al.,[10] reported that TEA had no significant changes in MAP, HR, CI, or systemic vascular resistance (SVR).

The total dose of intraoperative fentanyl was significantly lower in the TEA than in the GA group. This was consistent with Kessler et al.[11] and Mehta et al.,[2] who found that fentanyl requirement in patients undergoing off-pump CABG surgery was lower in patients receiving general anesthesia with thoracic epidural analgesia than those receiving general anesthesia alone.

In the present study, a higher dose of nitroglycerine was required to prevent hypertension in the GA group compared with the TEA group. However, higher doses of vasoactive drugs (dopamine) were required in TEA group than in the GA group, which could be explained by the effect of neuroaxial blockade in the TEA group. This was in accordance with Stensth et al.'s[8] and Fillinger et al.'s study.[9]

In the present study, the time of first awakening and extubation were shorter in the TEA group than in the GA group. These results are in accordance with previous studies.[1213] Early extubation is considered by many to reduce cardiovascular morbidity.[1415]

The present study showed that no significant difference as regard to ICU and hospital stay between the two groups. This is consistent with Fillinger et al.'s[9] and Kessler et al.'s observations[11] who found that there were no differences in ICU and hospital stay between the two groups.

Similar to our findings, Royse et al.[13] showed lower pain scores, earlier extubation, impaired cooperation with chest physiotherapy, improved postoperative O2 tension, and PEFR with TEA.

Also, Priestley et al.[16] found lower VAS score and less number of patients who received rescue analgesia in TEA group suggesting significantly better analgesia in the TEA group.

In the current study, the TEA group provided lower pain scores throughout the postoperative period with subsequent lower dosage of tramadol consumption when compared with the GA group. Shoyevitz et al.,[17] Stenseth et al.,[8] and Priestley et al.[16] found a lower VAS and earlier extubation but similar hospital stay with TEA. Sympathetic blockade in patients with coronary artery disease as it leads to optimization of oxygen demand/supply in the already impaired myocardium with resultant enhanced coronary perfusion and enhanced coronary perfusion and enhanced ventricular functions.[18]

Patients in the TEA group had statistically significant improvement in pulmonary function tests compared with GA group, probably due to better analgesia, as evidenced by lower VAS values, and use of 0.0125% bupivacaine, which is unlikely to produce motor block.

These findings are consistent with Gruber et al.,[19] and Steneth et al.,[8] who found better pulmonary function test values after thoracic epidural analgesia in patients undergoing CABG surgery.

As regard postoperative complications, nausea and vomiting were more frequent in the TEA than in the GA group. This in accordance with Goodarzi[20] who found that nausea and vomiting were more frequent in the epidural morphine than the other group; this may be due to the rostral spread of epidural morphine to the chemoreceptor trigger zone. Three patients in the TEA group developed pruritus, which may be due to histamine release, activation of peripheral opioid receptor, or production of excitatory morphine metabolites.[21] Although these side effects occurred more likely with morphine, they might be due to fentanyl[22] or tramadol.[2324]

We conclude that old age is an important risk factor for impairment of pulmonary function in patients undergoing CABG surgery. TEA reduced severity of postoperative pulmonary function and restoration was faster in TEA group. Also, earlier extubation and awakening, better analgesia, lower VAS, better recovery of pulmonary function tests with no significant adverse effects. We recommend the use of TEA in elderly patients undergoing CABG due to its advantages, absence of potential risk associated with this technique, and high incidence of postoperative atelectasis in elderly patients. Moreover, absence of proven difference in morbidity might be explained by limited number of patients in this study.