The Feasibility of Routine Early Extubation after Cardiac Surgery Protocol Generalized to a Nascent, Resource-limited Setup

Conduct of anesthesia

In the pre-operative period, the patients were counseled regarding weight optimization, smoking cessation, glycemic control, pulmonary exercises, and the post-operative severity of pain. On the night of the surgery, they would receive ringer lactate infusion at 1 mL/kg/h and were prescribed 0.25 mg alprazolam at night and on the morning of surgery.

The standardized intravenous induction of general anesthesia was provided with injection propofol 1–2 mg/kg, ketamine 0.5–1 mg/kg or etomidate 0.2–0.4 mg/kg, fentanyl 2 mcg/kg, vecuronium 0.1 mg/kg, and lidocaine 1mg/kg. An adult transesophageal echocardiography (TEE) probe (X7-2t, 3–8 MHz TEE probe, Phillips CX50^®, Koninklijke Phillips, N.V., USA) was inserted after intubation with an appropriately sized endotracheal tube, for pre-repair and post-CPB evaluation of cardiac functions. The neuromuscular monitor (MechanoSensor^®; Datex-Ohmeda, GE Healthcare, Helsinki, Finland) was used to monitor the neuromuscular blockade. The cerebral perfusion was monitored using near-infrared spectroscopy (INVOS™ 5100C, Medtronic, 710 Medtronic Parkway, Minneapolis, USA). A supplementation of 1 mcg/kg of fentanyl was allowed if the heart rate and mean arterial pressure were >20% for more than 60 s. The patients were heparinized using 3–5 mg/kg of intravenous heparin and CPB was instituted after attaining an activated clotting time (ACT) of >450 s. All patients received normothermic or mild hypothermic bypass and ultrafiltration was used during rewarming. Termination of CPB was achieved using a combination of vasopressor and inotropes as indicated by TEE. The heparin was neutralized using injection of protamine 0.8 mg/1 mg of heparin used. The ACT, clotting rate, and platelet functions were checked using Sonoclot© (Sienco, Inc.) at the end of the surgery.

In patients who received neuraxial morphine, the procedure was performed before general anesthesia, in the sitting position, 5 mcg/kg of morphine with 4 mL of normal saline was given at 4^th lumbar interspace with 26 gauge Quincke needle. In the patients receiving the chest wall blocks, the procedure was performed after sternum closure and protamine neutralization of heparin with ACT of <120 s. The techniques used were either a combined serratus anterior plane (SAP) block and/or transverse thoracic muscle plane block (TTMPB) (depending upon the incision site), under ultrasound guidance. In patients undergoing sternotomy, a bilateral TTMPB was given with 20 mL of 0.25% bupivacaine. Those with thoracotomy were given a combination of SAP and TTMPB block, with 0.25% bupivacaine 20 mL given at each site.

After the completion of the surgery, the feasibility of on-table extubation was assessed based on hemodynamic stability, respiratory sufficiency, use of minimum inotropic support, normothermia, adequate hemostasis, an arterial blood gas analysis, and extubated after giving neostigmine and glycopyrrolate based on residual neuromuscular block. Those patients who did not satisfy on-table extubation criteria were transferred to ICU and extubated by the intensivist based on extubation criteria - patient conscious and obeying commands, hemodynamic stability, heart rate and blood pressure within 20% of baseline, minimum inotropic and vasopressor support, chest drain output <4 mL/kg/h, partial pressure of oxygen > 80 mmHg on fraction of inspired oxygen < 0.5, tidal volume 6–8 mL/kg, respiratory rate 12–15/min.

The patients who were extubated in the operating room (OR) were categorized under “ultra-fast track” category. The “early extubation” patients were categorized as those extubated within 6 h of ICU admission and those extubated beyond 6 h were categorized under “delayed extubation” category.

The following complications were recorded in the ICU: Pulmonary complications: Bronchospasm - new wheezing; hypoxemia: Alveolar arterial oxygen gradient >29 mmHg; atelectasis: Abnormal radiological lung findings; pleural effusion; pneumonia - proved: Radiological evidence and pathological documentation; pneumothorax; reintubation within 48 h of extubation. Cardiac complications: Hypotension – fall in blood pressure >20% of baseline or increase in vasopressors; cardiac tamponade; new onset left or right ventricle dysfunction resulting in initiating/increase in inotropes; new onset myocardial infarction - new electrocardiogram changes and/or cardiac enzyme documentation; new-onset atrial or ventricular arrhythmias.

The following data variables were recorded:

• Patient demographics – Age, sex, comorbidities, ASA status, European System for Cardiac Operative Risk Evaluation (EuroSCORE) vr 2 risk, Risk adjustment for congenital heart surgery score versus 2.

• Anesthesia details – Anesthesia agents used, regional anesthesia, fentanyl dose, magnesium sulfate, lidocaine dose, intra-operative echocardiography, inotropic and vasopressor used, lactate, anesthesia-related complications

• Surgical details – Type of cardiac surgery, duration of surgery, CPB time, aortic cross-clamp (AXC) time, type of cardioplegia, minimum CPB temperature, CPB balance, surgery-related complications

• Post-operative outcomes – Extubation timings, postoperative pulmonary and cardiac complications, type and dose of ICU analgesia, length of ICU and hospital stay, mortality, if any.

Statistical analysis

The normality of quantitative data was checked by Kolmogorov–Smirnov tests. Our variables were non-normally distributed so were represented as median and interquartile range. The comparisons for two groups (gender, duration) were made by Mann–Whitney U test. When we had more than categorical variables, these were reported as counts and percentages. When all expected cell frequencies were more than five, the group comparisons were made with the Chi-square test. The Fisher’s Exact test was used when the expected cell frequencies were less than five. The receiver operating characteristic (ROC) curves were calculated to find maximal cut-off values of age, weight, and CPB time for extubation duration ≤6 h or more than 6 h. The ROC curve is a plot of sensitivity versus 1-specificity for the maximal cutoff values. A P < 0.05 was considered statistically significant. The analysis was conducted using the Statistical Packages for the Social Sciences (SPSS)^®, version 22.0 (SPSS Chicago, IL).

Demographic status

In our study group, there were ten patients with acyanotic congenital heart disease, three with coronary artery disease, and 17 with valvular heart disease. There were 12% patients in pediatric age (<12 years), while 88% of the patients were adults. The neuraxial morphine and the chest wall blocks were given in 15 of them. Nine patients were operated on by right anterior-lateral thoracotomy technique and a combination of right transversus thoracic muscle plane block (TTMPB) and serratus anterior muscle block was given to them. The patients with neuraxial block had lower intra-operative fentanyl consumption than the patients who were given chest wall blocks (3.59 ± 1.39 mcg/kg vs. 5.10 ± 1.69 mcg/kg; P = 0.011). The median extubation duration was 13 h (0.25 h–16 h) with ICU stay 3 days (2 days–4 days) and hospital stay of 10 days (7 days– 12 days). There was no difference in the extubation duration of the pediatrics and adult patients (P = 0.172). The pulmonary complications were reported in six, arrhythmias in three, and two patients expired in the immediate post-operative period – one because of severe left ventricle dysfunction and second because of sepsis-related multi-organ dysfunction [Table 1].

Ultra-fast track extubation group

The intra-operative post-CPB lactate was lower in patients extubated on table (2.00 mmoL/dL [1.20–2.40] vs. 2.80 [1.98–4.52]; P = 0.028). There was no re-intubation in these patients. The use of either neuraxial morphine or chest wall block neither had any effect on the duration of extubation (10.17 ± 7.57 h vs. 7.63 ± 9.15; P = 0.290) nor on the incidence of on-table extubation (14.3% vs. 33.3%; P = 0.231). The incidence of post-operative pulmonary complications (P = 1.00) and arrhythmias (P = 0.557) was not significantly different between the patients who were extubated on table and those who had delayed extubation. The median ICU stay (3 days [2–3] vs. 3 days [2–5]; P = 0.684) and hospital stay (7 days [6–9] vs. 10 days [7–13]; P = 0.074) was equal between the two sets of patients [Table 2].

Patients extubated in ICU

The pre-operative parameters of age (26.00 years [5.00– 41.50] vs. 48.00 years [40.50–61.50], P = 0.009) and weight (50.00 kg [13.80–52.00] vs. 61.00 kg [55.50–76.10], P = 0.003) were lower in patients extubated in ≤6 h [Table 3].

The intra-operative parameters of CPB time (82.00 min [62.00– 110.50] vs. 173.00 min [129.00–234.00], P = 0.007), AXC time (51.00 min [33.00–70.00] vs. 122.00 min [95.50–165.50], P = 0.005), and VIS score (4.00 [1.50–6.50] vs. 8.00 [5.00–11.50], P = 0.021) were significantly lower in patients extubated ≤6 h.

The post-operative fentanyl consumption was lesser in patients extubated ≤6 h 180.00 μg (50.00–200.00) versus 400.00 μg (180.00–480.00), P = 0.040. There was no significant difference in the incidence of post-operative pulmonary complications (P = 0.354) and arrhythmias (P = 1.000) among the patients.

The median ICU stay of patients extubated ≤6 h was 1 day (1–2) versus 3.50 days (2.25–6.00), P = 0.002 and the median hospital stay was 7 days (5.50–7.50) versus 11.50 days (10–14.75), P = 0.002, compared to patients extubated >6 h of surgery.

Sensitivity analysis

The patient age of >46.50 years (sensitivity 64.7%, specificity 83.3%, P = 0.01), weight >57.50 kg (sensitivity 70.6%, specificity 75%, P = 0.007), CPB time >147.50 min (sensitivity 70.6%, specificity 75%, P = 0.010), AXC time >108 min (sensitivity 64.7%, specificity 75%, P = 0.021), and VIS >6 (sensitivity 58%, specificity 66.7%, P = 0.054) could predict a post-operative mechanical ventilation duration of more than 6 h [Figure 2].

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Figure 2:

The ROC showing age, weight, vasoactive inotropic score (VIS), CBP, and AXC time as significant predictors of postoperative mechanical ventilation duration of more than 6 h. AXC: Aortic cross-clamp time, CPB: Cardiopulmonary bypass time, ROC: Receiver operating characteristic curve.

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Limitations

The post-operative perception of pain is a major determinant of the success of ultra-fast track extubation^[3] and both neuraxial morphine and anterior chest wall blocks are helpful analgesia adjuvants along with general anesthesia.^[10,22] Our study data collected retrospectively was done in a short period of 19 months and in a small group of patients. Although the inclusion criteria were strictly followed, we cannot completely rule out selection bias and non-random sampling.^[23,24] Future longitudinal studies are required to validate the causality of association between post-CPB lactate levels, age, weight, CPB and AXC times, and VIS scores to the duration of extubation.