Experimental animal studies of clip-induced microvascular trauma

Role of temporary arterial occlusion in subarachnoid hemorrhage outcomes: a prospective cohort study

PURPOSE

Temporary arterial occlusion (TAO) is a widespread practice in the surgical treatment of intracranial aneurysms. This study aimed to investigate TAO's role during ruptured aneurysm clipping as an independent prognostic factor on short- and long-term outcomes.

METHODS

This prospective cohort included 180 patients with ruptured intracranial aneurysms and an indication of microsurgical treatment. Patients who died in the first 12 hours after admission were excluded.

RESULTS

TAO was associated with intraoperative rupture (IOR) (odds ratio - OR = 10.54; 95% confidence interval - 95%CI 4.72-23.55; p < 0.001) and surgical complications (OR = 2.14; 95%CI 1.11-4.07; p = 0.01). The group with TAO and IOR had no significant difference in clinical (p = 0.06) and surgical (p = 0.94) complications compared to the group that had TAO, but no IOR. Among the 111 patients followed six months after treatment, IOR, number of occlusions, and total time of occlusion were not associated with Glasgow Outcome Scale (GOS) in the follow-up (respectively, p = 0.18, p = 0.30, and p = 0.73). Among patients who underwent TAO, IOR was also not associated with GOS in the follow-up (p = 0.29).

CONCLUSIONS

TAO was associated with IOR and surgical complications, being the latter independent of IOR occurrence. In long-term analysis, neither TAO nor IOR were associated with poor clinical outcomes.

The Importance of the Temporary Clip Removal Phase on Exposure to Hypoxia: On-Line Measurement of Temporal Lobe Oxygen Levels During Surgery for Middle Cerebral Artery Aneurysms

BACKGROUND

Most studies concerning intraoperative temporary arterial occlusion overlook the period between and after clip placement.

OBJECTIVE

To analyze the brain tissue oxygen tension through the process by which anterograde arterial blood flow is re-established after temporary clipping (TR).

METHODS

In this prospective observational study, patients who presented to surgery for middle cerebral artery aneurysms were continuously monitored with ICM+, to obtain temporal (downstream) PbtO2 levels while M1 segment temporary clips were applied and removed. PbtO2 changes were analyzed and compared with the clipping phase, and measures of exposure to hypoxia were defined and assessed during both phases and used in a model to test the impact of extending them.

RESULTS

Eighty-six TRs (20 patients) were recorded. The mean acquired amount of time per clip release (CR) event was 336.7 seconds. Temporary clip removal produced specifically shaped, highly individual PbtO2 curves that correlated with their corresponding clipping phase events but developing slower and less consistently. The CR phase was responsible for greater cumulative exposure to hypoxia than the clip application phase through the first and second minutes of each. In our model, the duration of the TR phase was mostly responsible for the total exposure to hypoxia, and longer CR phases reduced the mean exposure to hypoxia.

CONCLUSION

During the clip removal phase, the brain tissue is still exposed to oxygen levels that are significantly below the baseline, reverting through a singular, dynamic process. Therefore, it must be regarded by surgeons with the same degree of attention as its counterpart.

The impact of temporary clipping during aneurysm surgery on the incidence of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

OBJECTIVE Clipping of a ruptured intracranial aneurysm requires some degree of vessel manipulation, which in turn is believed to contribute to vasoconstriction. One of the techniques used during surgery is temporary clipping of the parent vessel. Temporary clipping may either be mandatory in cases of premature rupture (rescue) or represent a precautionary or facilitating surgical step (elective). The aim of this study was to study the association between temporary clipping during aneurysm surgery and the incidence of vasospasm and delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage (aSAH) in a large clinical series. METHODS Seven hundred seventy-eight patients who underwent surgical aneurysm treatment after aSAH were retrospectively included in the study. In addition to surgical parameters, the authors recorded transcranial Doppler (TCD) sonography-documented vasospasm (TCD-vasospasm, blood flow acceleration > 120 cm/sec), delayed ischemic neurological deficits (DINDs), and delayed cerebral infarction (DCI). Multivariate binary logistic regression analysis was applied to assess the association between temporary clipping, vasospasm, DIND, and DCI. RESULTS Temporary clipping was performed in 338 (43.4%) of 778 patients during aneurysm surgery. TCD sonographic flow acceleration developed in 370 (47.6%), DINDs in 123 (15.8%), and DCI in 97 (12.5%). Patients with temporary clipping showed no significant increase in the incidence of TCD-vasospasm compared with patients without temporary clipping (49% vs 48%, respectively; p = 0.60). DINDs developed in 12% of patients with temporary clipping and 18% of those without temporary clipping (p = 0.01). DCI occurred in 9% of patients with temporary clipping and 15% of those without temporary clipping (p = 0.02). The need for rescue temporary clipping was a predictor for DCI; 19.5% of patients in the rescue temporary clipping group but only 11.3% in the elective temporary clipping group had infarcts (p = 0.02). Elective temporary clipping was not associated with TCD-vasospasm (p = 0.31), DIND (p = 0.18), or DCI (p = 0.06). CONCLUSIONS Temporary clipping did not contribute to a higher rate of TCD-vasospasm, DIND, or DCI in comparison with rates in patients without temporary clipping. In contrast, there was an association between temporary clipping and a lower incidence of DINDs and DCI. There is no reason to be hesitant in using elective temporary clipping if deemed appropriate.

Nasal septum configuration as a basis for novel septal splints

The objective is to use anatomical determinations of nasal septum shape and surface area in adults as a design basis for silastic septal splints of universal size and fit and offering maximum possible surface coverage. The objective is also to devise a method of securing the septal splints, so that surface pressure on septal mucosa is distributed as evenly as possible while not interfering with capillary perfusion. Nasal septum area was determined in 21 Caucasian body donors, and nasal septum thickness was measured in 20 CT scans. Septal splints of universal size and shape were prepared from silastic sheeting. The holding force of various neodymium-iron-boron (NdFeB) magnets, and the surface pressure exerted by magnet-containing septal splints was calculated. These septal splints of novel design offer a satisfactory fit in routine clinical practice. The splints can be securely attached with built-in NdFeB magnets, and surface pressure can be distributed evenly across the nasal septum while not interfering with mucosal tissue perfusion. With their simple intranasal insertion, these magnet-containing septal splints of universal size and optimised shape offer maximum possible septum coverage following septoplasty/septorhinoplasty. The absence of interference with septal tissue perfusion means that they are likely to be associated with fewer postoperative complications and better outcomes.

Reversal of intraoperative arterial thrombosis with a fibrinolytic agent when treating large and giant partially thrombosed aneurysms of the middle cerebral artery

OBJECT

Thrombosis of the cerebral arteries is one of the complications of microsurgical operations for partially thrombosed intracranial aneurysms. The object of this study was to assess the frequency of intraoperative arterial thrombosis (IAT) during microsurgical treatment of large and giant partially thrombosed aneurysms of the middle cerebral artery (MCA) and also to assess the efficacy of the treatment of this complication.

MATERIALS

The authors analyzed a consecutive series of 53 patients who underwent surgery for partially thrombosed aneurysms of the MCA at the Burdenko Neurosurgical Institute between January 2005 and September 2014. Thirty-two patients had large aneurysms (15–25 mm) and 21 had giant aneurysms (> 25 mm). Clipping of aneurysms was performed in 47 patients, trapping was performed in 3, and wrapping was performed in 3.

RESULTS

IAT was diagnosed in 10 patients (18.9%). The authors describe a technique for IAT reversal involving the injection of modified human recombinant prourokinase (mr-proUK). Of the 7 patients who underwent injection of mr-proUK in the thrombosed artery, 5 (71.4%) were discharged without any change in neurological status, 1 (14.3%) experienced moderate deterioration (modified Rankin Scale [mRS] score of 2), and 1 (14.3%) experienced severe deterioration (mRS score of 4). Among the 3 patients who had complications and did not receive an injection of mr-proUK, 2 experienced severe deterioration (mRS score of 3 and 4) and 1 had moderate deterioration (mRS score of 2).

CONCLUSIONS

The primary risk factor of thrombectomy with temporary trapping is thrombosis in the MCA branches. The injection of a fibrinolytic agent into thrombosed MCA branches is an effective method for the treatment of IAT.

A half century (1961-2011) of applying microsurgery to experimental liver research

The development of microsurgery has been dependent on experimental animals. Microsurgery could be a very valuable technique to improve experimental models of liver diseases. Microdissection and microsutures are the two main microsurgical techniques that can be considered for classifying the experimental models developed for liver research in the rat. Partial portal vein ligation, extrahepatic cholestasis and hepatectomies are all models based on microdissection. On the other hand, in portacaval shunts, orthotopic liver transplantation and partial heterotopic liver transplantation, the microsuture techniques stand out. By reducing surgical complications, these microsurgical techniques allow for improving the resulting experimental models. If good experimental models for liver research are successfully developed, the results obtained from their study might be particularly useful in patients with liver disease. Therefore experimental liver microsurgery could be an invaluable way to translate laboratory data on liver research into new clinical diagnostic and therapeutic strategies.

Effects of temporary clipping during aneurysm surgery

OBJECTIVE

Intraoperative aneurysm rupture is associated with a high morbidity and mortality. Temporary vessel occlusion is an integral part of aneurysm clipping to avoid intraoperative hemorrhage. The information concerning the role of temporary occlusion regarding the development of cerebral vasospasm is sparse. The aim of this study was to provide more information in this field.

METHODS

We operated on 292 patients suffering from cerebral aneurysms. The data were reviewed from a prospectively collected databank, which includes information about the severity of subarachnoid hemorrhage, as well as transcranial Doppler data and surgical data such as temporary occlusion.

RESULTS

In 50% of our patients, temporary occlusion was performed during surgery. Twenty-nine percent showed an ischemic lesion in the CCT post-operatively, and in 58% of these patients, temporary occlusion was performed (versus 47% without temporary occlusion, p = 0.09). The mean occlusion time was longer in patients with radiologic signs of infarction. Furthermore, patients having unfavorable outcome showed a longer temporary occlusion time. Thirty-four percent of patients who underwent temporary vessel occlusion developed vasospasm postoperatively (versus 20% without temporary occlusion, p < 0.006). Temporary occlusion time correlated to the development of vasospasm as defined by transcranial Doppler flow velocity. Forty-eight percent of the patients treated using temporary occlusion suffered from middle cerebral artery aneurysm (versus 22% without temporary occlusion, p < 0.0001). An increased blood flow velocity was mostly seen in this region (p < 0.003).

CONCLUSION

According to our results, it seems to be the possible that temporary vessel occlusion is an additional factor in aggravating vasospasm after aneurysmatic subarachnoid hemorrhage.