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)

4 IMPORTANT FACTORS AND THE CORRESPONDING PROPERTIES OF THE LOCAL ANESTHETIC GETTING INFLUENCED:

Risk for Occupational Transmission of HCV

⚠️HCV is not transmitted efficiently through occupational exposures to blood. 

⚠️The average incidence of anti-HCV seroconversion after accidental percutaneous exposure from an HCV-positive source is 1.8% (range: 0%–7%) 

⚠️Transmission rarely occurs from mucous membrane exposures to blood, and no transmission in health care professionals, has been documented from intact or nonintact skin exposures to blood 

⚠️ Environmental contamination with blood containing HCV is not a significant risk for transmission in the health-care setting with the possible exception of the hemodialysis setting where HCV transmission related to environmental contamination and poor infection-control practices have been implicated 

⚠️The risk for transmission from exposure to fluids or tissues other than HCV-infected blood also has not been quantified but is expected to be low.

Reference: Centre for Disease Control June 29, 2001 / Vol. 50 / No. RR-11, Updated U.S. Public Health Service Guidelines for the Management of Occupational Exposuresto HBV, HCV, and HIV and Recommendations for Postexposure Prophylaxis

NEUROTOXICITY OF ANESTHETIC AGENTS IN LONG-TERM

🔹Halothane and Isoflurane: Amyloidogenic properties

🔹Isoflurane : Behavioural changes, apoptosis (Sevo lacks this)

🔹Nitrous oxide: Dose dependent and paradoxical protective and neurotoxic effects 

🔹Opioids @ moderate to high dose: Brain hyper metabolism and damage; Remifentanil doubtful role in genesis of Alzheimer's disease

(Acta Rad, CJA, Proct Natl Acad Sci, Anesth, Lancet)

C⃒L⃒A⃒S⃒S⃒I⃒F⃒I⃒C⃒A⃒T⃒I⃒O⃒N⃒ O⃒F⃒ N⃒E⃒R⃒V⃒E⃒ F⃒I⃒B⃒E⃒R⃒S⃒

BRIEF FUNCTIONAL ANATOMY OF THE BRAIN

✔️Precentral gyrus contains the primary motor cortex

✔️Premotor cortex lies immediately anterior to Primary motor cortex ( Brodmann’s area 6 on the lateral surface of the frontal lobe.)

✔️Premotor cortex is active in response to EXTERNAL visual or somatic sensory cues (e.g. reaching for an object in full view, or identifying an object by touch alone). Also has role in bilateral postural fixation (e.g. stabilization of the hips during walking).

✔️The supplementary motor area occupies a neighbouring part of Brodmann’s area 6 on the medial surface of the frontal lobe.

✔️The supplementary motor area seems to respond to INTERNAL cues, especially intentions to make voluntary movements (even if the movement is not carried out).

✔️Lesions of the supplementary motor cortex are associated with contralateral inability to initiate movements (akinesia).

✔️The inferior frontal gyrus of the dominant hemisphere (usually the left) contains the (Broca’s) motor speech area (Brodmann’s areas 44 and 45)

✔️The somatic sensory cortex, occupies the entire postcentral gyrus (Brodmann’s areas 3, 1 and 2, rostral to caudal).

✔️ Caudal to the somatosensory cortex is the sensory association cortex, which is divided into a superior and an inferior parietal lobule by an intraparietal sulcus.

✔️ The superior lobule is thought to be responsible for conscious awareness of the contralateral half of the body. Lesions of this part of the cortex may result in neglect of the contralateral side of the body.

✔️ The inferior lobule in the dominant (usually left) hemisphere is associated with language functions.

✔️ The cortex adjacent to the parieto-occipital sulcus and the calcarine sulcus, which lies on the medial surface of occipital lobe, constitutes the primary visual cortex (Brodmann’s area 17).

✔️ The superior surface of the temporal lobe contains the primary auditory cortex (Brodmann’s areas 41 and 42), responsible for the conscious perception of sound. Unilateral lesions of the primary auditory cortex will therefore cause partial deafness in both ears.

✔️ The auditory association cortex, known as Wernicke’s area corresponds to Brodmann’s area 22 in the dominant hemisphere. It allows for understanding of the spoken word, and connects with other language areas of the brain.

✔️ The temporal lobe curls inward to form the hippocampus which lies in the floor of the inferior horn of the lateral ventricle, and forms part of the limbic system. Its functions relate to short-term memory and the emotional aspects of behaviour.

✔️ Lying close to the anterior end of the hippocampus is the amygdala. Its a mass of subcortical grey matter that also forms part of the limbic system. It is associated with the conscious appreciation of smells.

✔️ The insula is one of the cortical centres for pain, and is also involved in involuntary activities such as the control of viscera by the autonomic nervous system.

✔️ The basal ganglia includes

• striatum (caudate nucleus, putamen of the lentiform nucleus and the nucleus accumbens) 

• pallidum (globus pallidus of the lentiform nucleus) 

• subthalamic nucleus 

• compact part of the substantia nigra 

✔️ Four basic circuits are known to occur from the cerebral cortex, through the basal ganglia and back to the cortex, by a direct or indirect route: 

-a motor loop is concerned with learned movements;

-a cognitive loop with motor intentions; 

-a limbic loop with emotional aspects of movement and 

-an oculomotor loop with voluntary saccades.

✔️ Limbic system is composed of the the parahippocampal and cingulate gyri, the septal area, the hippocampal formation and the amygdala. Declarative memory (i.e. of new facts and events) may occur as modifications of synapses within the hippocampus.

✔️ Diencephalon comprises, from superior to inferior, the epithalamus, thalamus, subthalamus and hypothalamus.

✔️ The thalamus is the largest component of the diencephalon and is composed of numerous nuclei.

✔️ The epithalamus consists principally of the pineal gland that secretes melatonin and is involved with circadian rhythm and regulation of the onset of puberty and the habenular nuclei.

✔️ The subthalamus contains the subthalamic nucleus which connects to the globus pallidus and substantia nigra and is involved with the control of movement.

✔️ The hypothalamus has important connections with the limbic system, a controlling influence on autonomic nervous system activity and a role in neuroendocrine function.

✔️ The cerebellum coordinates movement by maintenance of equilibrium, posture and muscle tone at an unconscious level. Also concerned with muscular coordination, including trajectory, speed and force of movements.

✔️ The tectum (roof) of the midbrain is formed by four colliculi –the paired superior colliculi are associated with the visual system, and the inferior colliculi with the auditory system.

Reference: The brain: functional divisions, Leo Donnelly, Neurosurgery, Neuroradiology & Neurocritical Care in Anaesthesia