Anaesthetic dose

Anticonvulsant action In anaesthetic dose all barbiturates e.g. phenobarbitone, mephobarbitone possess anticonvulsant action. Phenobarbitone is drug of choice for the treatment of grandmal epilepsy (details are given in chapter Antiepileptic drugs ). 

The clinical usefulness of MAC is questionable since, by definition, 50% of those receiving that concentration move in response to noxious stimulation. The median anaesthetic doses (ADs) required to prevent movement in 50% (AD50) and 95% (AD95) of patients are a later development and range from 5% to 40% greater than the MAC value. Again, these values are of only limited practical value. 

Harborne GC, Watson FL, Healy DT, Groves L. 1996. The effects of sub-anaesthetic doses of ketamine on memory, cognitive performance and subjective experience in healthy volunteers. J Psychopharmacol 10 134-140. 

Oranje B, van Berckel BN, Kemner C, van Ree JM, Kahn RS, et al. 2000. The effects of a sub-anaesthetic dose of ketamine on human selective attention. Neuropsychopharma-... 

Opioids Promethazine reduces the required analgesic and anaesthetic doses of several opioids. Sedation is also increased. 

Ketamine is a phencyclidine (hallucinogen) derivative and an antagonist of the NMDA-receptor. In anaesthetic doses it produces a trance-like state known as dissociative anaesthesia (sedation, amnesia, dissociation, analgesia). 

Compared to thiopental, etomidate has a greater margin of safety between anaesthetic dose and the dose that produces cardiorespiratory depression. 

B. Several studies suggest that beta blockers, such as atenolol and esmolol, given before induction reduce the anaesthetic dose requirement and may potentiate hypnosis. However, there are concerns that reducing the dose of anaesthetic may increase the risk of intra-operative awareness and it has been suggested that the use of BIS to predict the depth of anaesthesia in the presence ofbeta blockers may not be valid.There is a possibility that acute as well as chronic administration ofbeta blockers may prevent perioperative cardiac complications, but more study is needed on this. ... 

A placebo-controlled study in healthy subjects found that pre-treatment with topiramate 50 mg did not affect the reaction time after sub-anaesthetic doses of ketamine (slow intravenous injection of 120 micrograms/kg followed by 500 micrograms/kg over one hour)9... 

Table 10.11 The connexion between ionization and the narcosis of Arenicola (Minimal anaesthetic doses, in g per 100 ml of sea-water, rendering this worm immobile after 5 min)...

Contrary to what had earlier been supposed, there is no parallel between the anaesthetic doses of a series of depressants and their inhibition of the various enzymes isolated from the respiratory chain (see review by Butler, 1950). The concentrations of depressants required to inhibit respiration in tissues, in vitro, has always proved to be much higher than those used to produce surgical anaesthesia in humans. Thus the observed drop in cellular respiration caused by depressants is more likely to be a result of reduced nervous activity rather than a cause of it (Mcllwain, 1962). 

A further case series has described the use of sub-anaesthetic doses of ketamine (emergency department for indications such as procedural sedation, patient with chronic pain on opioids requiring breakthrough pain and pain causing emotional distress [42 ]. The author describes three cases ... 

Cocaine. This lias a bitter taste, is mydriatic, produces local anaesthesia and is toxic. After absorption, or when taken internally, it acts chiefly by stimulation of the central nervous system, succeeded by depression. Since the two phases may be present in different areas simultaneously, a mixed result may ensue. With large doses the chief symptoms are those of medullary depression. Death is due to paralysis of the respiratory centre. The main use of cocaine in medicine is as a local anaesthetic. 

Like RS-87337, Win 54177-4 (72) is reported to be a combined Class I/III antiarrhythmic agent. At a dose of 3 mg/kg, the compound increased effective refractory period by 2f% in anaesthetized guinea-pigs [204]. The com-... 

A dose of 7.0 /ig/kg of indolidan (i.v. administration) resulted in a 50% increase in contractility in anaesthetized dogs. A selective inotropic response has been observed with conscious dogs upon oral administration of 25 ngj kg of (23). The haemodynamic profile of (23) has been evaluated in anaesthetized dogs [78]. The acute and subchronic toxicology of indolidan has been studied (rats, dogs) [79]. 

From this series, compound MCI-154 (CAS 98326-33-1) (30) has been investigated in detail [95,96]. In vivo studies (anaesthetized dogs) revealed that doses of 0.3-100 tg/kg (i.v. administration) of MCI-154 produce dose-dependent increases in dF/dtmax and cardiac output, and decreases in arterial blood pressure and total peripheral resistance. The positive inotropic effect of (30) has been found to be superior to that exhibited by amrinone and milrinone [97,98]. It has been stated that MCI-154 exerts its activity probably by increasing the calcium-ion sensitivity of the contractile protein system of the cardiac skinned fibres [99,100]. A recent investigation suggests that inhibition of phosphodiesterase III is an important component of its cardiotonic activity [101]. 

From a variety of basic substituted pyridazinones investigated in Germany [176], ridazolol (59) (CAS 83395-21-5) has been selected for further evaluation as a cardioselective y9-blocker, since in vivo studies (anaesthetized dogs) had revealed that (59) is characterized by a high degree of cardioselectivity. The haemodynamic effects of ridazolol have been studied [177,178], Doses of 20-80 mg of ridazolol have been reported to cause dose-related decrease in exercise-induced tachycardia (for 8 h) and in systolic blood pressure (for 4h)[179],... 

Prilocaine is a local anaesthetic of low toxicity, which should be avoided in severe or untreated hypertension, severe heart disease and in patients using drugs that may cause methaemoglobinaemia. Prilocaine may cause ocular toxicity, which has been reported with the use of the product in excessively high doses during ophthalmic procedures. 

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