Can We Prevent a Postoperative Spinal Epidural Hematoma by Using Larger Diameter Suction Drains?

Abstract

Background: Epidural hematoma is a rare but serious complication. According to previous studies, it is not prevented by suction drains. This study evaluated the following alternative hypothesis: the larger the diameter of a suction drain, the less the remaining epidural hematoma after spinal surgery.

Methods: This was a randomized prospective study. Patients who underwent posterior lumbar decompression and instrumented fusion were divided into two groups: the large drain (LD, 2.8-mm-diameter tube) and small drain (SD, 1.6-mm-diameter tube) groups according to the diameter of the suction drains. All patients were consecutive and allocated alternately according to the date of operations. Suction drains were removed on day 3 and magnetic resonance imaging was performed on day 7 postoperatively. The size of remaining hematomas was measured by the degree of thecal sac compression in cross section using the following 4-point numeric scale: G1, less than one quarter; G2, between one quarter and half; G3, more than half; and G4, more than subtotal obstruction.

Results: There were 39 patients with LDs and 38 with SDs. They did not differ significantly in terms of sex, number of fusion segments, revision or not, antiplatelet medication, intraoperative injection of tranexamic acid. However, patient age differed significantly between the two groups (LD, 63.3 years and < SD, 68.6 years; p = 0.007). The two groups did not differ significantly in terms of prothrombin time, activated partial thromboplastin time, platelet number, blood loss, or operation duration. However, platelet function analysis exhibited a significant difference (LD, 164.7 seconds and < SD, 222.3 seconds; p = 0.002). The two blinded readers showed high consistency (Kappa value = 0.740; p = 0.000). The results of reader 1 were as follows: LD and SD had 21 and 21 cases of G1, 9 and 11 cases of G2, 6 and 6 cases of G3, and 3 and 0 cases of G4, respectively. The results of reader 2 were as follows: LD and SD had 22 and 23 cases of G1, 7 and 9 cases of G2, 7 and 6 cases of G3, and 3 and 0 cases of G4, respectively. There was no difference between the two groups (reader 1, p = 0.636; reader 2, p = 0.466).

Conclusions: The alternative hypothesis was rejected. Therefore, postoperative spinal epidural hematoma would not be prevented by LD.

Keywords: Epidural; Hematoma; Larger suction drain; Postoperative; Spinal.

Fig. 1. (A) The large drain: a 2.8-mm-diameter tube with 22 holes of 2.2 mm diameter per 10 cm length. The total area of holes per 10 cm was 89.7 mm². (B) The small drain: a 1.6-mm-diameter tube with 32 holes of 1.1 mm diameter per 10 cm length. The total area of holes per 10 cm was 32.4 mm². The large drain has 2.8-fold greater hole area and 1.75-fold greater tube diameter than the small drain. Therefore, the drainage capacity of the large drain is 1.75⁴ : 9.38-fold greater than that of a small drain according to the Hagen-Poiseuille law.

Fig. 2. Grading system of epidural hematoma as determined by thecal sac compression on T2-weighted axial images. (A) G1: less than one quarter. (B) G2: between one quarter and half. (C) G3: more than half. (D) G4: more than subtotal obstruction.