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Wednesday, July 13, 2016

Jugular venous oxygen saturation (SjO2)

🔹 Assess  the balance between global cerebral oxygen delivery and utilization.

🔹 Normal SjO2 is 55–75%

🔹 Low SjO2 (<50%)  /↓CBF or ↑CMRO 2/
CAUSES

➖↓BP
➖↓PaCO2 
➖Seizures 
➖Fever 
➖↑ICP or ↓CPP
➖Vasospasm 
➖Arterial hypoxia 

🔹 High SjO2 (>80%) /↑CBF or ↓CMRO2/
CAUSES

➖Hyperemia 
➖Failure of oxygen utilization (mitochondrial failure) Hypothermia 
➖Sedation
➖Arteriovenous shunting 
➖Brainstem death

🔹 When the catheter tip lies level with the mastoid process above the lower border of the first cervical vertebra on a lateral cervical spine radiograph contamination from the extracranial circulation, will be minimal. 

🔹 Accuracy is ensured, only if the dominant jugular bulb is cannulated, but in practice the right side is usually selected

🔹 A stat sample provides a stat measure of the brain’s oxygenation and metabolic status

🔹 SjO2 can be used to guide intraoperative blood pressure and ventilatory management. SjO2 monitoring is also widely used after TBI

🔹 Relatively insensitive to regional ischemia

🔹 The complications and contraindications of SjO 2 monitoring are same as for the insertion of an internal jugular central venous line

Reference: Key Monitoring in Neuroanesthesia: Principles, Techniques, and Indications by Martin Smith, Essentials of Neurosurgical Anesthesia & Critical Care 2012 Strategies for Prevention, Early Detection, and Successful Management of Perioperative Complications

Sunday, July 3, 2016

ANTI EPILEPTIC DRUG (AED) THERAPY IN NEURO INTENSIVE CARE

▪️Mechanisms, that can contribute to the development of seizures after craniotomy: (1) Free radical generation, due to iron and thrombin from blood components that have leaked in the tissue during surgery. (2) Disturbance of ion balance across the cell membranes due to local ischemia or hypoxia.

▪️Investigations which should be considered, in the event of an episode of postoperative seizures : Serum electrolytes, glucose, AED concentrations, ammonia and liver enzymes, toxicology screen, ABG, CT Brain & EEG (to exclude ongoing nonconvulsive seizures or SE). Derangements such as hypoglycemia, hyponatremia, hypocalcemia, hypomagnesemia, hypoxia or hyper-or hypocarbia should be corrected.

▪️ 5-20 Minutes Initial Therapy Phase^
A benzodiazepine is the initial therapy of choice (Level A): Can use either among the three

▶️Intramuscular midazolam (10 mg for > 40 kg, 5 mg for 13-40 kg, single dose, Level A) OR ▶️Intravenous lorazepam (0.1 mg/kg/dose, max: 4 mg/dose, may repeat dose once, Level A) OR ▶️Intravenous diazepam (0.15-0.2 mg/kg/dose, max: 10 mg/dose, may repeat dose once, Level A) 

🔻If none of the 3 options above are available, choose one of the following: 

▶️Intravenous phenobarbital (15 mg/kg/dose, single dose, Level A) OR 
▶️Rectal diazepam (0.2-0.5 mg/kg, max: 20 mg/dose, single dose, Level B) OR 
▶️Intranasal midazolam (Level B), buccal midazolam (Level B)

 🔻If seizures continue:

▪️ 20-40 Minutes Second Therapy Phase^: 
Choose one of the following second line options and give as a single dose 

▶️Intravenous fosphenytoin (20 mg PE/kg, max: 1500 mg PE/dose, single dose, Level U; PE is Phenytoin Equivalent ) OR 
▶️Intravenous valproic acid (40 mg/kg, max: 3000 mg/dose, single dose, Level B) OR 
▶️Intravenous levetiracetam (60 mg/kg, max: 4500 mg/dose, single dose, Level U) 

🔻If none of the options above are available, choose one of the following (if not given already) 

▶️Intravenous phenobarbital (15 mg/kg, single dose, Level B)

🔻If seizures continue^:

▪️40-60 Minutes Third Therapy Phase:
Choices include: 

▶️repeat second line therapy or 
▶️anesthetic doses of either thiopental, midazolam, pentobarbital, or propofol (all with continuous EEG monitoring)

➖Ketamine is also described 

🏮SPECIFIC POINTS:

▪️Phenytoin :  The dose of phenytoin is 18-20 mg/kg, at a rate not to exceed 50 mg/min; slower rates when under general anesthesia). Never mix phenytoin with a 5% dextrose solution; put it in a normal saline solution to minimize the risk of crystal precipitation. Therapeutic range is 10-20 µg/mL

▪️ Fosphenytoin is preferable, as it provides the advantage of a potentially rapid rate of administration with less risk of venous irritation (eg, to avoid the risk of purple-glove syndrome with phenytoin). Fosphenytoin is given at a rate not to exceed 150 mg PE/min). 

▪️ Sometimes, supplementation of the patient's routine medication (guided by stat AED levels) may help suppress their seizures.

▪️Phenobarbital’s sedative effect is minimized after a few weeks and, therefore, in chronic users may not be a problem in the postoperative period.

▪️Valproic acid generally described IV loading dose: 15–20 mg/kg, maintenance 400–600 mg q6h. Take caution while using it in patients with hepatic failure, thrombocytopenia and pancreatitis. The drug should never be given intramuscularly.

▪️ Absent seizures -Drugs used :  Ethosuximide also can be useful, but is not available in parenteral form.

▪️Levetiracetam and lacosamide are available in an IV formulation. These agents are renally eliminated, have minimal interactions with other common medications, and offer advantages in the ease of their use. However, patients with renal impairment will require dosage adjustment. Both agents have complete bioequivalence to the oral dose. Lacosamide is a novel antiepileptic drug, but its effectiveness in treatment of refractory SE is unknown.

▪️ Benzodiazepines are the preferred first-line agents. Lorazepam is preferable to diazepam, because of lack of active metabolites and redistribution to extracerebral tissues. 

▪️ Pentobarbital is preferable to phenobarbital because of shorter elimination ( T 1/2 around 24 h vs. 96 h) and in a meta-analysis was more efficacious than midazolam or propofol

▪️ Some clinicians even consider rapid oral loading of one of the newer AEDs like topiramate, depending on the ongoing clinical urgency. 

▪️ Correct any metabolic imbalances. Control hyperthermia.



Reference: ^Treatment of Convulsive Status Epilepticus in Children and Adults,Epilepsy Currents 16.1 - Jan/Feb 2016 , 2016 American Epilepsy Society Guidelines , 

Status Epilepticus Treatment & Management, 

Julie L Roth, Stephen A Berman, Medscape , Antiepileptic Drug Therapy in Neurosurgical Critical Care, Panayiotis N. Varelas and Denise H. Rhoney, Essentials of Neurosurgical Anesthesia & Critical Care 2012 Strategies for Prevention, Early Detection, and Successful Management of Perioperative Complications



Friday, July 1, 2016

SPINA BIFIDA : #Anesthesia IMPLICATIONS

💥Incidence of Spina bifida occulta is 10%–25% of the population. 

💥Associated with cord abnormalities (spinal dysraphism)

💥70% of those with cord abnormalities have dimpling or a hairy naevus at the base of the spine. 

💥30% of patients with spinal dysraphism have neurological signs. 

💥If such a patient comes for surgery, an MRI scan should be done to rule out a tethered cord. 

💥Once this is excluded, it may be appropriate to proceed with regional analgesia at a site above the lesion. 

💥The patient should be explained about the higher incidence of dural puncture because of abnormal ligamental structure. 

💥Another point is, there may be incomplete spread of anaesthetic to sites below the lesion and consequently a suboptimal block may occur. 

💥The epidural space volume is usually reduced and so, the epidural should be established with small aliquots of local anaesthetic to prevent a high block. 

💥Spina bifida is also associated with a difficult intubation.

💥Spina bifida is a risk factor for latex allergy

Ref: Ali L, Stocks GM. Spina bifida, tethered cord and regional anaesthesia. Anaesthesia. 2005; 60(11): 1149–1150. Griffiths S, Durbridge JA. Anaesthetic implications of neurological disease in pregnancy. Contin Educ Anaesth Crit Care Pain. 2011; 11(5): 157–161. D’Astous J,Drouin MA, Rhine E 1992 Intraoperative anaphylaxis secondary to allergy to latex in children who have spina bifida. Report of two cases. Journal of Bone & Joint Surgery 74: 1084–6.

Monday, June 27, 2016

CLINICAL GUIDELINES FOR #Opioid ROUTE CONVERSION AND ROTATION

Reference: Opioid Equianalgesic Tables: Are They All Equally Dangerous? Philip E. Shaheen, Declan Walsh, Wael Lasheen, Mellar P. Davis and Ruth L. Lagman (Journal of Pain and Symptom Management, Vol. 38 No. 3 September 2009)

👄Rotation of an opioid, secondary to uncontrolled pain requires equianalgesic doses.

👄If you are rotating an opioid secondary to toxicity, it  requires a dose 30% 50% lower than the equivalent dose of the second opioid. This is because of incomplete analgesic cross-tolerance.

👄Thirty percent of patients who are on opioids need an alternative route, as in severe nausea or mucositis. 

👄Once toxicity occurs, before doing rotation, consider treating side effects, lowering the dose of the current opioid(if pain is controlled), and use of adjuvant analgesics. 

👄Whenever we start or titrate opioid dose, always  consider the pharmacokinetic alterations due to age, comorbid conditions, gender, other simultaneously administered medications, and organ failure etc

👄Opioids that are partial agonists have less analgesia per dose increment at higher doses than full agonists or opioids with high intrinsic efficacy (e.g., methadone); therefore, equianalgesic ratios will change with dose. 

👄Rotating to a new opioid before reaching steady-state of the first opioid is pharmacologically meaningless.

👄Rotation in the setting of organ dysfunction is dangerous even if we use  the recommended doses from equianalgesic tables. 

👄Note that, opioids may worsen intestinal colic. Dexamethasone, glycopyrrolate, or octreotide are better options for such pains. 

👄Opioid-induced toxicity takes some time to resolve. If symptoms related to toxicity are persisting after rotation, it can be because of slow clearance of the first opioid and not the new opioid. 

👄Be cautious while rotating between short and long-acting opioids and do it in a careful way, so as to avoid withdrawal or overdosing.

#pharmacology , #anesthesia , #PainAndPalliativeCare , #OpioidRotation , #CriticalCare , #pharmacy , #PainPhysician , #anaesthesia

Sunday, June 26, 2016

GESTATIONAL DIABETES : INFO WE GET FROM THE #ACOG 2013 GUIDELINES


✔️Increased blood sugars 4-6 h prior to delivery leads to increased rates of hypoglycemia in the neonate. A maternal blood glucose value of more than 180 mg/dl has been conclusively proven to be associated with high risk of neonatal hypoglycemia.

✔️The American College of Obstetrics and Gynecology and the American College of Endocrinology recommends maintenance of blood glucose between 70 and 110 mg/dl during labor (3.9-6.1 mmol/L) this goal is the same irrespective of whether the women has type 1 diabetes, type 2 diabetes or GDM. 

✔️The hepatic glucose supply is sufficient during the latent phase of labor, but during the active phase of labor the hepatic glucose supply is depleted so calorie supplementation is required. 

✔️During labor in a case with GDM controlled only on life-style modification it is not compulsory to monitor blood sugars periodically and monitoring once in every 4-6 h is sufficient during labor 

✔️In patients on insulin it is mandatory to monitor the blood sugar every 2-4 h during the latent phase, every 1-2 h during the active phase 

✔️In patients for whom cesarean is planned, it always preferred to do the procedure early morning. 

✔️Patient needs to take her usual night dose of intermediate-acting insulin and the morning dose of insulin has to be withheld and patient needs to be kept nil by mouth. 

✔️If surgery is delayed it is needed to start basal and corrective regimen (DNS with short acting insulin) with one-third of the morning intermediate insulin dose with a 5% dextrose infusion to avoid ketosis. Blood glucose has to be monitored second hourly and if required subcutaneous dose of corrective dose of short acting insulin to be given. 

✔️After delivery, the requirement of insulin shows a sharp decline and in GDM it is advisable to continue the monitoring to see if the sugars have become normal in the postpartum period 

✔️In cases with type 1 and type 2 DM it is prudent to decrease the dose of insulin by 20-40% of the pregnancy dose as the requirement of insulin during lactation is less. During the breast-feeding, sometimes the requirement of insulin can fall drastically and these women may develop hypoglycemia, so the dose of insulin needs to be adjusted accordingly

Reference: ACOG Practice Bulletin, 137, 2013

Indian Journal of Endocrinology and Metabolism: Peripartum management of diabetes, Pramila Kalra and Manjunath Anakal

#anesthesia , #diabetes , #gdm , #insulin , #acog ,#labor ,

Friday, June 17, 2016

<Ⓜ️NEMO WFNS GRADING SCALE FOR SAH

▪️I   : GCS 15

▪️II  : FULL GCS-2 ( 15-2=13 )

▪️III : 3D ( DEFICIT (+) for WFNS III )

▪️IV : "ForSee a dozen problems" ( i.e. WFNS 'Four'->GCS is 'Seven' {~ForSee}.. to 12 {a dozen})

▪️ V : "5-6"( WFNS 5 means GCS <6 )


ANEURYSM CLIP VIVA VOCE ; SURGICAL PEARLS FOR THE ANESTHESIOLOGIST / 'SAFE Anesthesiologist' Series [Surgical Aspects For Empowering the Anesthesiologist]

❓CAN YOU TELL A FEW SITUATIONS WHERE ENDOVASCULAR THERAPY MAY BE A BETTER OPTION THAN SURGERY?

🅰 Aneurysms in elderly patients, in patients with poor neurological condition, in patients presenting with cerebral vasospasm, 
aneurysms that are difficult to surgically access and multiple aneurysms requiring multiple craniotomies for treatment

❓ CAN YOU TELL A FEW SITUATIONS WHERE SURGERY MAY BE A BETTER OPTION THAN ENDOVASCULAR THERAPY?

🅰  fusiform, blister-like, very small, very large, thrombotic, and wide-necked aneurysms, in patients presenting with a clinically significant intracerebral hemorrhage

❓CAN YOU TELL A FEW ADJUNCTS WHICH THE SURGEON MAY USE OR MAY ASK FROM THE ANESTHESIOLOGIST TO MINIMIZE THE RISK OF DIRECT BRAIN INJURY

🅰 Good bony removal to minimize or eliminate brain retraction, meticulous microsurgical dissection to preserve veins, pharmacologic brain protection or bypass procedures to reduce the risk of ischemic injury, use of temporary clips to reduce the risk of intraoperative rupture, and intraoperative imaging with digital subtraction angiography or indocyanine green videoangiography to verify surgical results

❓WHAT IS THE PROBLEM IF THE BONE DRILLING / EXPOSURE IS LESS THAN ADEQUATE 

🅰 Surgeon will be forced to use more brain retraction throughout the surgery , which may result in direct brain injury and thus  increase the chances of postoperative complications 

❓WHAT IS THE PROBLEM IF THE SURGEON OVERLOOK THE IMPORTANCE OF PRESERVING THE VEINS WHILE FOCUSING ON THE ARTERIAL ANATOMY 

🅰This can hamper venous drainage and can result in devastating venous congestion and infarction, postoperatively

❓WHAT ARE THE METHODS AVAILABLE TO PROLONG ISCHEMIC TOLERANCE TIMES DURING TEMPORARY CLIPPING

🅰 Burst suppression using Propofol or Barbiturates, induced hypertension, Hypothermia

❓ WHAT IS THE MAJOR ADVANTAGE OF SURGICAL CLIP LIGATION OF ANEURYSM OVER ENDOVASCULAR OPTIONS

🅰 Low risk of recurrence, if the clipping has been appropriate

❓WHAT ALL METHODS ARE AVAILABLE FOR THE SURGEON  IN DETERMINING WHETHER THE ANEURYSM IS COMPLETELY OBLITERATED AFTER CLIPPING

🅰 Puncturing the dome of the aneurysm after clipping and observe for refilling, Intraoperative angiography, indocyanine green videoangiography ( Indocyanine green dose : 0.2-0.5mg/kg bolus, max daily dose= 5mg/kg  )

❓ WHAT ALL METHODS ARE AVAILABLE FOR THE SURGEON  IN DETERMINING WHETHER THERE IS ANY COMPROMISE OF PARENT VESSEL AFTER CLIPPING

🅰intraoperative angiography,  Indocyanine green videoangiography and Microvascular doppler

❓ WHAT ARE THE METHODS AVAILABLE FOR THE SURGEON TO AVOID INTRAOPERATIVE RUPTURE OF THE ANEURYSM

🅰 Adequate exposure, sharp dissection, proximal control, and use of temporary clips. For proximal carotid aneurysms, control may require exposure of the cervical carotid, which also allows the surgeon to trap the aneurysm and to use suction decompression

❓IN THE EVENT OF AN UNTIMELY INTRAOPERATIVE RUPTURE OF AN ANEURYSM, WHAT ARE THE METHODS AVAILABLE FOR CONTROLLING THE BLEEDING

🅰 In this situation the tasks for the surgeon are: (1) Control bleeding (2) Repair the aneurysm & (3) Repair the arterial defect. For controlling the bleeding many techniques have been described, including use of a large-bore suction over the bleeding site , tamponade with a cottonoid, proximal temporary occlusion or trapping, carotid compression, coagulation of the aneurysmal rent, clip application to the distal sac, and induced hypotension. Sometimes the surgeon may ask for an Adenosine induced flow arrest, for placing the clip.

Reference: Chaper 13, Intraoperative Misadventures: Complication Avoidance and Management in Aneurysm Surgery
Daniel L. Barrow, Clinical Neurosurgery, Volume 58, 2011, The Congress of Neurological Surgeons



Wednesday, June 15, 2016

TARGET CONTROLLED INFUSIONS DURING ANESTHESIA; PHARMACOLOGICAL PRINCIPLES


⏩TCIs are used for sedation and as an alternative to inhalational anaesthesia. 

⏩Here an infusion, controlled by a microprocessor-driven pump that alters the infusion rate to maintain a user-defined target plasma concentration ( as guided by certain pharmacokinetic models e.g. modified Marsh model and Schnider models for propofol and the Minto model for remifentanil.) delivers the drug.

⏩ Previous models used the plasma concentration (Cp) to target. Recent models target an effect site concentration (Ce). The 'effect site compartment' reflects the hysteresis between plasma concentration and the clinical effect observed.

⏩They basically work based on the principle of the bolus, elimination and transfer regime:

1️⃣An initial bolus dose to fill the central compartment with the drug (B)

2️⃣An infusion of constant rate, equal to the elimination rate (E)

3️⃣An infusion that compensates for transfer of drug to the peripheral tissues (T)
.......forming the 'BET' regimen

⏩ The Marsh model assumes that the central compartment volume is directly proportional to the weight of the patient only. It does not use age as part of its calculation, but will not function if an age less than 16 is entered. 

⏩ The more recent Schnider model calculates lean body mass using age, height and weight and calculates doses and infusion rates accordingly. 

⏩ Consequently , there is difference, in the size of the central compartment when calculated using different models

REMEMBER👇🏾

⏩The plasma and effect-site concentrations are calculated ; not measured (as compared with end tidal agent monitoring). 

⏩The hemodynamic impact of the drug will depend upon the maximum plasma concentration achieved and so in elderly patients, a large overshoot in the plasma concentration and haemodynamic compromise can happen, when a bolus is given: be cautious

⏩In morbidly obese patients with a BMI > 42, with increasing body weight the calculation of Lean Body Weight used in the Schnider model paradoxically decreases. This decrease leads to a higher estimated clearance and thus a larger initial bolus dose and higher infusion rate will be administered by the pump.

#TargetControlledInfusions , #anesthesia ,#anaesthesia , #tci , #infusion , #pharmacology , #propofol , #pharma , #biomedical ,#CriticalCare

Reference: Hill SA. Pharmacokinetics of drug infusions. Contin Educ Anaesth Crit Care Pain. 2004; 4(3): 76–80.