FUROSEMIDE , THIAZIDES & NSAIDs : A FEW FACTS❗️

⚜Furosemide is a loop diuretic

⚜It interferes with the concentrating capacity of the loop of Henle.

⚜It is effective in patients with renal dysfunction, whereas the thiazides are NOT.

⚜It potentiates the nephrotoxic effects of cephalosporins and the ototoxic effects of aminoglycosides.

⚜NSAIDs inhibit renal prostaglandin, causing sodium to be retained, which reduces the diuresis caused by furosemide.

⚜ Furosemide is a venous and arteriolar dilator and thus reduces both preload and afterload in a time frame just before the period of onset of a significant diuresis.

PERIOPERATIVE CONCERNS IN THE SURGICAL MANAGEMENT OF PATIENTS WITH MOYAMOYA SYNDROME

PERIOPERATIVE ANESTHESIA CONCERNS IN THE SURGICAL MANAGEMENT OF PATIENTS WITH MOYAMOYA DISEASE

⌛️Moyamoya disease is characterized by progressive occlusion of the distal portion of the Internal Carotid Artery and the proximal Anterior and Middle Cerebral Arteries. 

⌛There is production of lots of factors promoting angiogenesis. This will cause 

(1) intimal proliferation of smooth muscle and eventual occlusion of vessels.

(2)Profuse lenticulostriate collateral formation at the base of the brain (These collaterals are known as Moyamoya vessels) 

(3)Vasodilatation of collaterals

⌛️Patients are at risk for both hemorrhagic ( due to rupture of the abnormal vessels) and ischemic stroke ( due to ischemia because of vasoocclusion) .

⌛️Presentation:

🔹Ischemic (80%): stroke , TIA etc

🔹Others: epilepsy (5%), ICH (2.5%)

⌛️On cerebral angiography, in more advanced stages of the disease, the hemispheric perfusion appears as a ‘puff of smoke’, from which the disease derives its name (Moyamoya= Puff of smoke in Japanese).

⌛️Associations: Optic/ hypothalamic glioma , Craniopharyngoma , NF-1 , Renal Artery Stenosis , Hypertension

⌛️Usual neurosurgical treatment involves Superficial Temporal Artery to Middle Cerebral Artery (MCA) Anastamosis through a small craniotomy, if there is a suitable MCA target. If not, an encephalo-duro-arterio-synangiosis (EDAS) can be performed by opposing a Superficial Temporal Artery pedicle to the cortical surface. This helps collateral formation from extra to intra cranial circulation over time (months to years).

⌛Intraoperative Concerns: ️Excessive hypertension may cause hemorrhage from friable vessels and hypotension may cause ischemic stroke from hypoperfusion

⌛️Blood pressure, blood volume, and PaCO2 require careful monitoring because moyamoya patients have a diminished cerebral perfusion reserve and deviation from normal levels can result in stroke.

⌛️So we have to take special care to avoid hypotension , hypovolemia ( give optimal preoperative, intraoperative and postoperative hydration) hyperthermia, and hypocarbia ( to avoid hypocarbia induced cerebral vasoconstriction)

#neurology , #anesthesia , #moyamoya , #stroke , #neurosurgery , 

Reference 

Surgical Management of Moyamoya Syndrome Edward R. Smith, R. Michael Scott , Skull Base. 2005;15(1):15-26.

Parray T, Martin TW, Siddiqui S. Moyamoya disease: a review of the disease and anesthetic management. J Neurosurg Anesthesiol. 2011 Apr;23(2):100-9.

DEXAMETHASONE AS AN ANTIEMETIC; THINGS TO BE KEPT IN MIND

▫️Dexamethasone is an extremely effective antiemetic for children.

▫️Usually a one-off dose of 4 mg is given. 

▫️This single dose has not been shown to produce significant adverse effects such as immunosuppression and poor wound healing.

▫️Has rescue antiemetic properties

▫️Most effective if given early on in the operation.

▫️An awake patient may complain of an uncomfortable sensation of perineal warmth, when dexamethasone is given

#ponv , #antiemetics , #dexamethasone , #anesthesia , #pharmacology , #CriticalCare

SUB DURAL HEMATOMA (SDH) FACTS FOR THE ANESTHESIOLOGIST

✔️10–20% of all patients with craniocerebral trauma. 

✔️Blood between the dura mater and arachnoid 

✔️Usually venous bleeding 

✔️A blow to the head puts tension on the cerebral veins, and they typically tear at their attachment to the dural sinuses.

✔️Acute subdural hematomas are an absolute emergency indication 

✔️In 95 % of all cases, the lesion is supratentorial (especially frontoparietal) 

 ✔️Bilateral hematoma is present in 15% of all cases.

 ✔️Imaging Modality of choice: CT

✔️CT findings (Acute subdural hematoma): 

〰Hyperdense crescent-shaped hemorrhage(early acute components can appear hypodense) 

〰Not bounded by sutures 

〰subdural hematoma is concave

〰Significant mass effect: midline displacement 

〰Obstructed flow of CSF, blockage of the interventricular foramen of Monro

〰Reduced demarcation between gray and white matter 

〰Cisterna ambiens obliterated 

〰Usually there is no visible fracture 

✔️Postoperative contralateral rebleeding may occur in response to removal of the tamponade. 

✔️Chronic subdural hematoma: Isodense or hypodense collection of blood in a crescent along the brain 

✔️With isointense hematomas, the midline displacement is often the only detectable sign of a hematoma

✔️The contrast enhancement of the cerebral vessels after IV administration of contrast agent aids in differentiating the hematoma from brain tissue 

✔️Significant mass effect 

✔️MRI is not indicated in an acute subdural hematoma 

✔️In a chronic subdural hematoma, MRI can be used to estimate the age of the lesion 

✔️Anisocoria or suddenly fixed pupils are an alarm signal but a late sign . Patients are often intubated.

✔️Prognosis is usually poor if concomitant administration of drugs such as acetylsalicylic acid and clopidogrel has been there

✔️In the CT, clinician should look for :

Extent • Midline displacement • Size of basal cisterns • Obstructed flow of CSF.

✔️Be careful to avoid missing of bilateral isodense chronic subdural hematomas.

#sdh ,#neurosurgery ,#anesthesiology , #BrainImaging , #CTbrain

EPIDURAL HEMATOMA (EDH) FACTS FOR THE ANESTHESIOLOGIST

✔️ 1–5% of all patients with craniocerebral trauma 

✔️ In 5% bilateral

✔️ usually traumatic bleeding between the inner table and dura mater • 

✔️ Usually the result of arterial injury (middle meningeal artery in 85% of all cases) • 

✔️ Venous bleeding occurs in 15% of all cases (diploic veins, dural venous sinus, especially in infratentorial hematomas) 

✔️ May occur in combination with other forms of hematoma (subdural, subarachnoid, intracerebral) in up to 20% of all cases • 

✔️ Localization: usually temporoparietal. 

✔️ Imaging Modality of choice CT. 

✔️ CT findings:

〰Semiconvex shape 

〰Hyperdense 

〰Acute, uncoagulated blood components can also be hypodense 

〰The hematoma cannot cross suture lines as the dura mater is firmly attached to the bone along the boundaries of the calvaria 

〰Significant mass effect: midline displacement 

〰Reduced demarcation between gray and white matter 

〰Obstructed flow of CSF (blockage of the interventricular foramen of Monro) 

〰Cisterna ambiens narrowed 

✔️ The hematoma can rapidly expand 

✔️ Usually there is a displaced calvarial fracture 

✔️ Postoperative contralateral rebleeding (epidural or intracerebral) may occur in response to removal of the tamponade. 

✔️ MRI not indicated because of the long time required to organize and perform the examination. 

✔️ Absolute emergency that can rapidly become life threatening 

 ✔️ The patient’s condition can dramatically worsen very rapidly 

✔️ Anisocoria or suddenly fixed pupils are an alarm signal but a late sign . Patients are often intubated. 

✔️ Unconscious patients with an epidural hematoma not requiring surgery should have a follow-up CT within six hours 

✔️ With early craniotomy, the prognosis is good; otherwise mortality is high.

✔️ The clinician should look for : Extent • Midline displacement • Obstructed flow of CSF.

#edh , #tbi , #craniotomy , #neurosurgery , #anesthesiology ,#NeuroAnesthesia ,#CTbrain

CELLULAR METABOLISM : A FEW NUMBERS

🔹Each molecule of ATP can produce 7.6 kcal of energy

🔹Aerobic metabolism of 1 mol of glucose generates 38 mol of ATP.

🔹A total of 288 kcal is produced per 1 mol of glucose. Ideally it can liberate 686 kcal; so this process is only 42% efficient.

🔹 Under aerobic conditions, during glycolysis,  2 ATPs are used but 4 ATPs and 2 NADH are generated. Under anaerobic conditions, NADH is not produced. 

🔹 A total of 325 g of glycogen is stored within skeletal muscle (75%) and the liver (25%).  Only 3% of the total energy available from glucose is utilised in the process of glycogenolysis; So storage of glucose as glycogen is highly efficient 

🔹 The HMP shunt produces Carbon dioxide, ribose-5-phosphate and NADPH but '0' ATP.

#biochemistry , #glycolysis , #physiology , #anesthesia

IMPORTANT FACTORS THAT AFFECT DRUG METABOLISM IN THE ELDERLY DURING ANESTHESIA

🚨Hepato-portal blood flow and hepatic enzymatic activity decrease 

🚨Plasma albumin level is reduced as you age, and for plasma protein-bound drugs this will lead to an increased proportion of unbound, active drug.

🚨Glomerular filtration rate falls by approximately 1% per year beyond the age of 30

🚨Opioid receptors decrease in number and increase in affinity ( The importance of this factor is less than the above mentioned ones, in case of opioid toxicity in elderly)

🚨IMPORTANT: lean body mass, body fat and total body water all fall. The volume of distribution of most drugs is therefore reduced. B͎u͎t͎ t͎h͎e͎ T͎O͎T͎A͎L͎ B͎O͎D͎Y͎ W͎A͎T͎E͎R͎ ( and muscle mass) d͎e͎c͎r͎e͎a͎s͎e͎s t͎o͎ a͎ g͎r͎e͎a͎t͎e͎r͎ e͎x͎t͎e͎n͎t͎ t͎h͎a͎n͎ t͎h͎e͎ T͎O͎T͎A͎L͎ B͎O͎D͎Y͎ F͎A͎T͎. 

⚙So drugs that are water-soluble, are affected more

🚨Elderly patients may be particularly sensitive to remifentanil, as a large proportion of its metabolism is catalysed by muscle-based esterases.

#DrugToxicity , #geriatrics , #anesthesia , #pharmacology

FACTS ABOUT DIATHERMY......FOR THE ANAESTHESIOLOGIST🔥

🔰Alternating current with a frequency between 0.5 and 1 MHz is used. 

🔰The cutting function requires a sine wave pattern and the coagulation function requires a damped or pulsed sine wave pattern. 

🔰Unipolar (monopolar) diathermy 

🔹consists of a small tip where the current density and heating effect is high. 

🔹The current flows through the patient to a neutral or patient plate, which is earthed. 

🔹The patient plate is large so the current density and heating effect is negligible.

🔰Bipolar diathermy equipment 

🔹consists of two tips on a pair of forceps. 

🔹The current passes across the field between the two tips to bring about heating. 

🔹 No patient or neutral electrode is required. 

🔹 is preferable to unipolar if the patient has a cardiac pacemaker or CNS stimulator (spinal cord or deep brain), as the current is kept at the forceps tip and will not be passing through the body. 

🔹 This reduces the likelihood of current passing down the pacemaker or stimulator wire and exciting or damaging electrically conductive tissues. 

🔹 is used for delicate surgery such as ophthalmic surgery and neurosurgery.

ETOMIDATE BASED ANESTHESIA- FACTS🎙

⌛️Etomidate is an imidazole derivative

⌛️It has higher incidence of PONV than other induction agents

⌛️It causes pain on injection 

⌛️It can trigger porphyric crisis, in susceptible individuals

⌛️The REVERSIBLE BLOCKADE of the adrenocortical enzymes 11β -hydroxylase and 17α-hydroxylase, reduces BOTH corticosteroid and mineralocorticoid synthesis and the effect LASTS FOR 3–6 hours after a bolus dose.

⌛️The effect of a bolus of etomidate is terminated by redistribution of drug to peripheral tissues

⌛️The standard dose for induction of anaesthesia is 0.3 mg/ kg

#etomidate ,#AdrenalSuppression , #porphyria , #anesthesia , #anaesthesia , #IntensiveCare

pH and [H+] : QUANTIFICATION & COMPARISON

✅For each one point increase in the pH scale, the concentration of hydrogen ions, and the acidity, changes by a factor of 10. 

✅Therefore, a solution with a pH of 4 is 10 times as acidic as a solution with a pH of 5, and 100 times more acidic than a solution with a pH of 6. 

✅The scale is relative in terms of [H +], so although a pH of 8 implies an alkaline solution, the number of H + ions still differs 100-fold from a solution with a pH of 10. 

✅HOW TO FIND pH WHEN WE KNOW THE STRENGTH OF THE SOLUTION 

🔹pH = –log10[ H +]

🔹If solution is 0.01 M solution ,[H+] = 10^2= –log (10^2) = pH 2 

🔹More simply put, the pH is the number of times you need to move the decimal point to get the first non zero value (here it's 1)