Effect Of Sevoflurane Versus Propofol During Cardiac Surgery Biology Essay

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Background: Sevoflurane has showed protective effect on the myocardium after ischemic injury. The current study tested the effect of sevoflurane versus Propofol during cardiac surgery on 48 hours troponin level.

Methods: fifty patients who will undergo elective coronary artery bypass surgery were randomized to receive either general anesthesia with sevoflurane or propofol with the same anesthetic and surgical techniques in both groups. For assessing myocardial injury, troponin I was measured during the first 48 postoperative hours.

Results: Troponin I concentrations increased significantly in propofol-anesthetized patients than in patients anesthetized with sevoflurane. In the sevoflurane group, the duration of ICU stay was significantly less than the propofol group (45.0  4.5 h. in the propofol group versus 23.0  4.6 h. in the sevoflurane group) (p<0.05), with no statistical significance difference in hospital stay length between groups (7.2  1.3days in the propofol group versus 7.1  0.8 days in the sevoflurane group).

Conclusion: Patients receiving sevoflurane during coronary artery surgery had less myocardial injury during the first 48 postoperative hours than patients receiving propofol.

Introduction:

Ischemia-reperfusion injury, which occurs during coronary artery bypass grafting (CABG) surgery, may lead to marked myocardial dysfunction. Freedman and colleagues reported that enflurane could protect the isolated rat heart from post myocardial ischemic damage. (1)

Volatile anesthetic agents may protect the myocardium by minimizing ischemic-reperfusion injury , by its preconditioning effect on the myocardium, mediating nitric oxide release thus protecting endothelial coronary cells (2) and suppressing neutrophil activation (3,4). Laboratory investigations show that volatile anesthetics, preconditioning might be beneficial to variety of tissues as the brain, kidneys, and spinal cord. (5)

The preconditioning effect of volatile anesthetics on human myocardium was investigated in some clinical studies, but on small number of patients. (6-9) this study was done to assess the effect of sevoflurane in cardiac surgery on 48 hours troponin level.

Patients & Methods:

After written informed patient consent and ethics committee approval, 50 patients who were admitted to Ain Shams specialized hospital for elective single-vessel (left anterior descending artery) bypass surgery were enrolled in the study. Patients with unstable angina, preoperative ejection fraction less than 40%, history of myocardial infarction <4 wks, valvular heart disease, intracardiac shunts, liver dysfunction, renal insufficiency (creatinine concentration >1.5 mg/L), and, or emergency cases were excluded. All preoperative cardiac medications were continued until the morning of surgery except for aspirin and clopidogrel, which were stopped a week before the operation. No patient was excluded.

Patients were randomly assigned by using sealed envelopes before induction of anesthesia into two equal groups to receive either sevoflurane (group S, n = 25) or propofol (group P, n = 25).

Midazolam 0.1-0.2 mg/kg was given 30 min before induction of anesthesia. Anesthesia was induced with propofol 1 mg/kg, fentanyl 5 g/kg and atracruim 0.6 mg/kg in both groups. Trachea was intubated and ventilation was adjusted to keep Paco2 at 35 mmHg. Standard monitoring included 5-lead electrocardiogram (ECG), continuous arterial blood pressure, central venous pressure, nasopharyngeal temperature, and peripheral oxygen saturation were applied.

In group S, anesthesia was maintained with fentanyl 0.2-0.4 g/kg/min and sevoflurane 0.5%-1% end-tidal. In group P; anesthesia was maintained with fentanyl 0.2-0.4 g/kg/min and propofol infusion of 2-4 mg/kg/hr. Heparin, 300 IU/kg was administered to keep activated coagulation time above 450s.The same cardioplegic solution was used in both groups.

During CPB, anesthesia was maintained in group S with fentanyl 0.4 g/kg/min and sevoflurane 0.5%-1% and in group P, with fentanyl 0.4 g/kg/min and infusion of propofol 2-4 mg/kg/hr. Post bypass, anesthesia was maintained with fentanyl 0.4 g/kg/min combined with sevoflurane 0.5%-1% end-tidal in group S and propofol 1-2 mg/kg/hr in group P. After aortic cannula removal, protamine at a ratio of 1 mg for each 100 units of heparin was given. After surgery, Patients were sedated at the intensive care unit (ICU) with fentanyl 0.3 g/kg /min and propofol 2-4 mg/kg/hr. Time to weaning the patients from the ventilator was recorded.

A Blood sample was obtained in all patients for determination of cardiac troponin I, before the start of surgery (base), at arrival in the ICU (T0) , at 6, 12, 24 and 48 h (T6, T12, T24, and T48) postoperatively. An immunoassay method was used to measure Troponin I. The limit of cardiac troponin I quantification was 0.04 ng/mL.

Statistical methods:

Data was collected, tabulated, coded then analyzed by using SPSS® version 12.0 computer software. Parametric data are presented as mean (standard deviation).Mauchly's test of sphericity was used to examine normality and sphericity; data was analyzed by repeated-measures. General linear model ANOVA. Error bars represent 95% confidence interval. A difference with p-value <0.05 was considered statistically significant.

Results:

Patients' characteristics are expressed in table 1, with no significant difference in both groups as regarding, age, sex, height, body mass index, ejection fraction and preoperative medications.

Hemodynamic changes are shown in table 2; there were no significant changes between the two groups as regarding heart rate, mean arterial blood pressure before, during(HR only) and after CPB. The duration of aortic cross clamping and cardiopulmonary bypass time were statistically the same between the two groups. (p>0.05)

Table 1: Patients characteristics.

Data are expressed as mean ± SD or %

Preoperative data:

Propofol group

Group P(n=25)

Sevoflurane group Group S (n=25)

Age (years)

655

674

Male/female

15/10

14/11

Height (cm)

1635

1626

BMI (kg/m2)

222

232

Ejection Fraction (%)

502

564

Preoperative medications:

Beta-adrenergic blockers

(no. of patients)

12

13

Calcium channel blocker

(no. of patients)

5

4

Nitrates

(no. of patients)

3

3

Diuretics

(no. of patients)

6

6

LMWH

(no. of patients)

3

3

Acetyl salicylic acid

(no. of patients)

12

13

BMI = body mass index; LMWH = low molecular weight heparin; No statistically significant difference between both groups, P>0.05.

Table 2; Intraoperative data:

Data are expressed as mean ± SD

Hemodynamic data:

Propofol group

Group P(n=25)

Sevoflurane group Group S (n=25)

- Before CPB

- HR

-MAP

60±3

76±6

62±3

78±4

-During CPB

-MAP

42±9

40±7

-After CPB

- HR

-MAP

86±4

70±4

88±4

72±5

-Aortic Cross-clamp time

(min)

5711

5910

-CPB time (min)

779

8010

HR= Heart Rate, MAP=Mean arterial pressure, CPB= cardiopulmonary bypass

No statistically significant difference between both groups, P>0.05.

Weaning from the ventilator was done in the first 8 h after arrival in the ICU in both groups. In the sevoflurane group, ICU stay length was significantly less than the propofol group (p<0.05), but the difference in hospital length stay was not statistically significant. (Table 3)

Postoperatively, none of the patients developed myocardial infarction. Twenty four hours postoperatively, Five patients in the propofol group had atrial fibrillation compared with two patients in the sevoflurane group (p>0.05).

Table 3; postoperative data:

Propofol group

Group P(n=25)

Sevoflurane group Group S (n=25)

-Duration of ventilation(h)

6.5±0.5

6±1♦

-ICU stay(h)

45.0±4.5

23.0±4.6*

-hospital stay( days)

7.2±1.3

7.1±0.8♦

♦ P value>0.05 is considered statistically non significant.

* P value < 0.01 is considered statistically highly significant.

Troponin I level increased in both groups in all readings. Six hours postoperatively (T6), troponin I level became significantly higher in the propofol group compared to the sevoflurane group and the rate of decline during the first 48 h postoperatively was faster in the sevoflurane group than the propofol group. (Fig.1)

3

Figure 1: Evolution of cardiac troponin I in both groups before surgery (base), at arrival in the intensive care unit (T0), and at 6 (T6), 12 (T12), 24 (T24), and 48 (T48) hours postoperatively.

Discussion

The results of this study showed that in coronary artery bypass surgery, patients anesthetized with sevoflurane had better preservation of cardiac function after surgery indicated by the low level of cardiac troponin I 48 h compared to the patients anesthetized with propofol. No significant differences in hemodynamic parameters intraoperativly, aortic cross clamping time and cardiopulmonary bypass time, duration of ventilation and hospital stay between the two groups. However ICU stay time was shorter in the sevoflurane group compared to the propofol group.

Experimental studies have shown that administration of volatile anesthetics before and after ischemia improve cardiac function and this was attributed to anesthetic preconditioning effect (10-13), they may have this protective action when administrated during the reperfusion period (14-16). Variable results on postoperative cardiac function and myocardial damage were shown in preconditioning protocols. (17-22) De Hert et al assessed cardiac function after CPB using different times in administration of volatile anesthetics and demonstrated that the best protective effect was achieved when the volatile anesthetic was administered during the whole procedure. (23-24) This protective effect was either by direct preconditioning or indirect by enhancing ischemic preconditioning. (25-30)

In agreement with this study, Vander Linden et al. suggested the beneficial effects of a volatile regimen in valve surgery, where they found a decrease in postoperative troponin T in patients anesthetized with inhaled sevoflurane compared to those anesthetized with an IV drug. (31)

A sensitive marker to assess myocardial damage is cardiac troponin I (32, 33). In this study, Troponin I level was increased in propofol group by 2 ng/mL which is comparable to the value(5.2g/L) reported by Sadony (34) in his study on patients classified as having minor myocardial damage.

Symons and Myles performed a search on 27relevant randomized control trials (including 2979 patients) as regarding the myocardial protection of inhalational anesthetics. They showed no difference in the incidence of myocardial infarction, length of stay in intensive care unit or mortality between the groups. Post-bypass, compared intravenous anesthetics regimen, patients who received volatile anesthetics had lower troponin I serum levels, lesser requirement for inotropic support and 20% higher cardiac indices. Their duration of mechanical ventilation was reduced by 2.7 h, and hospital stay length was decreased by one day. (35)

However, there are certain limitations in this study, postoperative troponin I levels were used as the only detector of myocardial damage, other variables such as rhythm disturbances, post-operative morbidity and mortality should be also assessed.

In Conclusion, Patients receiving sevoflurane for coronary artery surgery had less myocardial injury during the first 48 postoperative hours; less stay in the ICU these supports the cardioprotective effects of sevoflurane.

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