APPROACH TO PATIENTS WITH INTRACRANIAL ANEURYSM PERIOPERATIVELY; A FEW ANESTHETIC AND SURGICAL PRINCIPLES

✔️Risk factors for an aneurysmal SAH (aSAH) include female sex, African American ethnicity, first-degree relative with SAH, low HDL cholesterol level, hypertension, obesity, alcohol abuse, and tobacco use.

✔️For diagnosis,CT has the highest sensitivity during the first 3 days after the onset of bleeding; MRI has better sensitivity than CT after 3 days . Lumbar puncture can also confirm clinical suspicions of SAH.

✔️Risk of rebleeding is highest within the first 12 hours of initial rupture.

✔️Cerebral ischemia caused by rebleeding and cerebral vasospasm is the major cause of morbidity and mortality after aSAH. ( Hypovolemia and increased ICP heighten the chance of cerebral vasospasm )

✔️Vasospasm and DCI (Delayed Cerebral Ischemia ) are common after SAH and occur most frequently 7-10 days after aneurysm rupture.

✔️Induced hypertension to treat DCI is recommended if cardiac status allows and baseline blood pressure is not elevated.

✔️Early rebleeding has worse outcomes than later rebleeding 

✔️General recommendations call for SBP <160 mmHg because of the risk of rebleeding; by administering nicardipine, labetalol, and esmolol to control hypertension when needed; and avoiding sodium nitroprusside.

✔️Although Nimodipine has not been shown to improve cerebral vasospasm by angiogram, it has decreased delayed ischemia and improved neurologic outcomes. Verapamil has been shown to improve neurologic outcomes without increasing ICP.

✔️Hemodynamic augmentation focus has shifted away from traditional triple H therapy toward maintenance of normovolemia and induced hypertension

✔️The Neurocritical Care Society recommends vasopressor therapy to augment blood pressure when necessary. Commonly used vasopressors include phenylephrine, norepinephrine, and dopamine. 

✔️For a symptomatic vasospasm unresponsive to hypertensive augmentation, the AHA has deemed cerebral angioplasty and/or selective intraarterial vasodilator therapy reasonable.

✔️In the presence of vasospasm, intraaortic balloon pump therapy has been shown to successfully improve cardiac function and cerebral blood flow for patients with SAH and to reverse vasospasm-induced DCI

✔️️Erythropoietin has shown some promise in lowering the incidence of vasospasm and delayed cerebral ischemia

✔️Albumin has been shown to improve cerebral perfusion, has neuroprotective properties and minimal effect on coagulation

✔️Administering normal saline intravenously can help attenuate hyponatremia while maintaining appropriate normovolemia. Vasopressin is not commonly used as a vasopressor for patients with SAH because hyponatremia is seen associated with SAH and vasopressin has ability to further deplete blood sodium levels

✔️In the immediate post hemorrhage period , clinicians should consider using a short course (3-7 days) of anticonvulsant therapy prophylactically, while weighing the risks, including possible worse cognitive outcomes ( e.g. Phenytoin may worsen outcomes Ref: J Neurosurg Anesthesiol. 2011 Jan;23(1):35-40. doi: Adenosine-induced transient asystole for intracranial aneurysm surgery: a retrospective review.Guinn NR1, McDonagh DL, Borel CO )

✔️Elevated troponin levels ( not ECG changes) have been associated with increased mortality and disability at discharge. Because of possible cardiac dysfunction and its negative effect on outcomes, treatment of cardiac insufficiency should be considered. If cardiac dysfunction and/or myocardial injury are present, therapies like triple H therapy for vasospasm, must be weighed for their benefit vs risk

✔️When aneurysm obliteration is delayed, antifibrinolytic drugs such as aminocaproic acid or tranexamic acid have been shown to reduce the incidence of rebleeding

✔️Papaverine has been shown to reverse arterial narrowing, but it has not been shown to improve outcomes and its use is not recommended.

✔️The latest guidelines from the AHA/American Stroke Association recommend endovascular coiling as the preferred method of treatment for ruptured aneurysms that are amenable to both clipping and coiling. However, middle cerebral artery aneurysms are sometimes difficult to treat with coiling, so clipping might be a better option.

✔️The Neurocritical Care Society recommends maintaining hemoglobin between 8-10 g/dL and maintaining higher levels (up to 12 g/dL) for patients at risk for DCI

✔️Monitoring of  cerebral function via cortical somatosensory evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAEPs) can guide surgical cessation or application of temporary vascular occlusion (clipping) and can guide adjustment of blood pressure management for perfusion augmentation if cerebral ischemia is detected.

✔️During temporary clipping, induced hypertension may be requested and considered to increase cerebral perfusion pressure for the duration of the clipping, especially if the temporary clipping is to be longer than 120 seconds. Brief periods of temporary clipping of aneurysms have been shown not to affect outcomes, but the duration should not be greater than 15-20 minutes.

✔️Mannitol, Frusemide and Cerebrospinal fluid volume management via ventricular drains can facilitate creation of slack brain. ( N.B: abrupt ICP decreases and brain sagging can lead to rebleeding, reflex hypertension, bradycardia, and possible asystole, as well as significant clinical deterioration postoperatively.Acute volume drainage should not exceed 20-30 mL)

✔️Mild hyperventilation (30-35 mmHg PaCO2 with intact dura and 20-30 mmHg with open dura) can be employed to facilitate a reduction in brain-blood volume via cerebral vasoconstriction in patients with intact CO2 cerebrovascular activity

✔️Induced hypotension is not recommended, and the degree and duration of hypotension should be minimized because of the increased risk of neurologic deficits

✔️The Neurocritical Care Society recommends blood glucose levels <200 mg/dL and >80 mg/dL, compared to the old recommendation of levels <129 mg/dL.

Reference:

Anesthetic Management of Patients with Intracranial Aneurysms

Alaa A. Abd-Elsayed, MD, MPH, Anthony S. Wehby, RN, MSN, and Ehab Farag, MD, FRCA

Connolly ES, Jr, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2012 Jun;43(6):1711–1737.

Rabinstein AA, Lanzino G, Wijdicks EF. Multidisciplinary management and emerging therapeutic strategies in aneurysmal subarachnoid haemorrhage. Lancet Neurol. 2010 May;9(5):504–519

Priebe HJ. Aneurysmal subarachnoid haemorrhage and the anaesthetist. Br J Anaesth. 2007 Jul;99(1):102–118.

MEASUREMENT OF CEREBRAL BLOOD FLOW

✔️Can be measured by Fick Principle

✔️This states that the uptake/ release of a substance e.g. O2 (Vo2) by an organ is the product of the blood flow (Q) through that organ and the arteriovenous difference in content (Cao2-Cvo2)

✔️This is applied using Kety-Schmidt technique where 10% Nitrous oxide is inhaled for 10-15 minutes, and the jugular venous concentration is measured and assumed to be the same as the brain concentration

✔️Once CBF is determined, additional values like CMRO2 and vascular resistance may be derived. 

✔️N2O offers significant advantages over other agents used for the measurement of CBF in that it is safe, stable, cheap, readily available and has a partition coefficient unaffected by varying levels of lipid and water and hence is unlikely to change with age or cerebral oedema.

✔️CBF calculated by this technique represents the mean blood flow from the area of the brain draining into the particular jugular venous bulb being sampled: i.e. the ipsilateral cerebral hemisphere. Therefore, the Kety–Schmidt method of CBF measurement is unable to discriminate between grey and white matter and is insensitive to regional changes in flow. 

Ref: Textbook of Neuroanaesthesia and Critical Care, Basil F Matta

INTRACRANIAL ANEURYSMS : GENETICS AND ASSOCIATED DISEASES

Of patients who have SAH from ruptured aneurysm, 5% to 10% will have one or more first-order relatives who have also had a ruptured aneurysm. 

The inheritance is probably dominant with variable penetrance. 

Conditions associated with intracranial aneurysms include 〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰

🏷polycystic kidney disease (5% of aneurysms series, 33% of polycystic kidney series)

🏷coarctation of the aorta (1% of aneurysm patients, 5% of coarctation patients, all of whom are hypertensive)

🏷sickle cell disease

🏷drug abuse (cocaine: generalized vasoconstriction and hypertension; intravenous use: mycotic aneurysms)

🏷hypertension (30% to 40% of patients with SAH). 

Rarer associations 

〰〰〰〰〰〰〰

🏷fibromuscular dysplasia

🏷Marfan's syndrome

🏷tuberous sclerosis

🏷Ehlers-Danlos syndrome

🏷hereditary hemorrhagic telangiectasia

🏷moyamoya disease

🏷pseudoxanthoma elasticum. 

🏷Choriocarcinoma 

🏷cardiac myxomas 

Ref: Handbook of Neuroanesthesia, 4th Edition, p:144

MAKE OURSELVES AWARE OF THE DISINFECTANTS USED IN OUR HOSPITALS: ETHYLENE OXIDE

💥Sterilant of choice for sterilizing heat labile medical equipment

💥e.g. plastic and rubber items, blankets,crude drugs and powders,glass ,metal, paper,fabrics 

💥Also used for sterilizing heart-lung machines, respirators, sutures

💥Extremely penetrant, non corrosive,effective 

💥Toxic, irritant, mutagenic and a suspected carcinogen 

💥Explosive, except when mixed with other gases like Carbon dioxide or Nitrogen in the ratio 1:10 (require expensive equipment)

💥Usually used at 55-60 degree at about 33% humidity

💥Items to be sterilized should be clean and packaged with polythene or polypropylene (don't use nylon)

💥The sterilizing process should be monitored by spore tests +/- indicator tests

💥As ETO and its residues are toxic and irritant, materials exposed should be thoroughly aerated before use. Aeration at 55 degree greatly enhances elution of ETO

💥Control limit of exposure of individuals at work is 1 ppm ETO over an 8 hour time weighted averaged period

💥Irradiated articles should not be subsequently treated with ETO, unless they are known to be safe after such treatment 

Reference :

Hospital Associated Infections; Epidemiology, Prevention and Control , Nita Patwardhan , p:71-72

Predictors of mortality after subarachnoid hemorrhage

<Ⓜ️nemo : "POOR PreDICTOR"

P͞͞O͞͞O͞͞R͞͞  neurologic condition at hospital admission, a function of rate and volume of bleed

P͞͞R͞͞E͞͞existing illness

D͞͞epressed level of consciousness after initial bleed

I͞͞ncreased blood pressure

C͞͞irculation affected: if Basilar 

T͞͞hick clot in the brain substance or ventricles on initial computed tomographic scan

O͞͞lder age

R͞͞epeat hemorrhage