Analgesic Drugs [Abridged]

Abstract

20pressures unless halothane was administered: 0 5% halothane could cause a rapid rise of central venous pressure by 8 cmH2O and fall of arterial pressure by 10-15 mmHg.Eighty patients undergoing major intracranial and spinal operations were studied. In 50 patients, intra-arterial and central venous pressures, electrocardiograms and pulse rate were recorded. Intermittent positive pressure ventilation was used throughout, maintaining the Paco2 between 33 and 36 mmHg.Each received 2-5 mg haloperidol an hour before induction of anesthesia. Anmsthesia was maintained using 2:1 nitrous oxide and oxygen. DiscussionPentazocine is almost as effective an analgesic as phenoperidine. It causes little respiratory depression even in the presence of medullary failure from neurological damage. It occasionally causes transient respiratory depression reversed by methylphenidate. It causes little additional effect on respiration or circulation when combined with general anesthesia unless halothane is used, when the latter's respiratory depression and circulatory effects are severely aggravated. Minor degrees of depressed respiration (end-tidal CO2 below 42 mmHg) and bradypncea occur consistently. The dose end-tidal CO2 response is not statistically significant but suggests that the response reported in rabbits (Hunter 1968) might also occur in man.Hypertension occasionally develops after large doses (15 mg/kg). This is not due to surgical stimulation or to the effects of CO2 retention or hypoxia. The patient did not show a prior undue sensitivity to the injection of dilute adrenaline solutions.Minor signs of nalorphine-like psychoses can develop (Beaver et al. 1966). This was not seen in the present series. A satisfactory response to respiratory depression occurs with methylphenidate.Pentazocine did not facilitate intermittent positive pressure ventilation of patients in respiratory failure. It has been used to suppress pain and allow the use of hyperventilation for patients with chest and spinal injuries. ConclusionsPentazocine is a potent analgesic suitable for the control of post-operative pain, for analgesic supplement in light general anesthesia, and, combined with haloperidol or droperidol, for neuroleptanalgesia.Respiratory rate seldom falls below 14 and end-tidal CO2 seldom rises above 42 mmHg. Respiratory depression is countered by methylphenidate. Pentazocine occasionally causes hypertension.There is no apparent increase in wound bleeding or tissue engorgement. The ECG is unaltered.It enhances both the respiratory depressant and hypotensive effects of halothane. It does not appear to aggravate respiratory depression due to neurological injury.