Surgical anaesthesia

Is placebo surgery ethical Should doctors be allowed to administer anaesthesia and make surgical incisions, but then not do any therapeutic intervention Isn t the first rule of medicine to do no harm It is true that informed consent is now required in clin-... 

It may be noted that the oculomotor centre in the brain is also controlled by impulses passing from the higher centres. If these are inhibited, constriction of the pupil occurs, e.g. during sleep and surgical anaesthesia. The higher centres can be directly stimulated by morphine, thus causing pin-point pupil. 

Poelma and Tukker [130] developed the chronically isolated intestinal loop method which allows absorption to be studied in the absence of surgical trauma and anaesthesia. The model also facilitates cross-over experimental schemes. A major segment of the intestine is identified and surgically isolated under initial anaesthesia. The loop remains in the peritoneal cavity, with intact blood supply... 

The use of local anaesthetics outside specialized surgical or anaesthetical practice is usually limited to infiltration anaesthesia, different surface anaesthetic methods, and (nerve) block of fingers and toes. Lo-... 

Halothane causes relatively greater depression of respiration. It inhibits intestinal and uterine contractions. Cardiac output is also reduced by 20 to 50 percent when anaesthesia is induced by inspiration of halothane at 0.8 to 1.2 percent concentration, which is necessary for surgical anaesthesia. Heart rate is slowed during anaesthesia, tachyarrhythmias may also occur in the presence of halothane. 

No unusual effect on the gastrointestinal tract has been reported with enflurane anaesthesia, however, certain evidence of hepatic impairment has been obtained during and after surgical anaesthesia. Hepatic necrosis probably occurs with enflurane in rare instances. 

As a adjuvant to general anaesthesia (specially in major surgical procedures e.g. abdominal and thoracic surgery, orthopaedic procedures, intubation etc). 

Morphine Morphine (C17H19NO3), a habit forming Class A analgesic drug, is the major bioactive constituent of opium poppy seeds. Like other opium constituents (opiates), e.g. heroin, morphine acts directly on the CNS to relieve pain. Morphine is used for the treatment of post-surgical pain and chronic pain (e.g. cancer pain), and as an adjunct to general anaesthesia, and... 

The pharmacodynamic effects of all volatile agents on body systems may be modified by surgical stimulation depending on the depth of anaesthesia. The pharmacological properties of the drugs described below are those of the agents in the absence of surgical stimulation unless otherwise stated. 

Intraocular pressure is reduced by 40%. The pupil first dilates and then constricts, although the light reflex is maintained until surgical anaesthesia is achieved. The corneal, conjunctival, eyelash and eyelid reflexes are abolished. 

In 1952 a French surgeon, Henri Laborit, used chlorpromazine to aid anaesthesia in surgical operations. His description of its effects led French psychiatrists Jean Delay and Pierre Deniker to wonder about its... 

A mean chloroform concentration in arterial blood of 173 ig/ml was reported in spontaneously breathing subjects during surgical anaesthesia (N. Poobalasingham and J. P. Payne, Br. J. Anaesth., 1978,50, 325-329). 

Therapeutic Concentration. During surgical anaesthesia, concentrations in blood are usually in the range 22 to 84 pg/ml. Venous blood concentrations lag behind arterial concentrations during induction and decline less rapidly during recovery. 

Peak plasma-bromide concentrations occurred in surgical patients 2 to 3 days after anaesthesia and ranged from 52 to 180 pg/ml (J. H. Tinker et al., Anesthesiology, 1976, 44, 194-196). 

Animal size Rabbits are more docile and amenable to handling and experimentation than mice and rats. The rabbit size (2-3 kg) lets an easy manipulation of both the whole animal and the eye to be easily extruded fi-om its location and to be surgically manipulated. General anaesthesia is required only for surgery while daily examinations occasionally need local anaesthesia. Conversely, the small size of rats and mice allows the use of small amounts of drugs given systematically. 

The details surrounding the first use of surgical anaesthesia were submerged in bitter disputes on priority following an attempt to take out a patent for ether. The key events around this time were ... 

On December 21 Robert Liston performed the first surgical operation in England under ether anaesthesia. ... 

Balanced surgical anaesthesia (hypnosis with analgesia and muscular relaxation) with a single drug requires high doses that will cause adverse effects such as slow and unpleasant recovery, and depression of cardiovascular and respiratory function. In modem practice, different drugs are used to attain each objective so that adverse effects are minirnised. 

Disadvantages. Nitrous oxide is expensive to buy and to transport. It must be used in conjuction with more potent anaesthetics to produce full surgical anaesthesia. 

Uses. Nitrous oxide is used to maintain surgical anaesthesia in combination with other anaesthetic agents, e.g., isoflurane or propofol, and, if required, muscle relaxants. Entonox provides analgesia for obstetric practice, for emergency management of injuries, and during postoperative physiotherapy. 

Induction. Intravenous route 1-2 mg/kg by slow intravenous injection over a period of 60 seconds. A dose of 2 mg/kg produces surgical anaesthesia within 1-2 min, which will last 5-10 min. Intramuscular route 5-10 mg/kg by deep intramuscular injection. This dose produces surgical anaesthesia within 3-5 min and may be expected to last up to 25 min. 

Anaesthesia in MH-susceptible patients is achieved safely with total intravenous anaesthesia using propofol and opioids. Dantrolene for intravenous use must be available in every surgical theatre. The relation of malignant hyperthermia syndrome with neuroleptic malignant syndrome (for which dantrolene may be used as adjunctive treatment, see p. 388) is uncertain. 

Surgical anaesthesia may lead to a brisk fall in blood pressure in patients taking antihypertensives. Antih5q3ertensive therapy should not be routinely altered before surgery, although it obviously can complicate care both during and after the operation. Anaesthetists must be informed. 

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