Combining physostigmine with meperidine for sedation and analgesia during colonoscopy

BACKGROUND AND STUDY AIM

Opiate or benzodiazepine drugs are often used during colonoscopy, but they are associated with respiratory depression and prolonged recovery. Physostigmine, a tertiary anticholinesterase agent, is known to enhance analgesia and to reverse the central nervous system depressant effects of these drugs. This study compared the effect of giving meperidine alone with the effect of giving meperidine in combination with physostigmine in patients who were undergoing complete colonoscopy.

PATIENTS AND METHODS

A total of 44 outpatients undergoing elective colonoscopy were randomly assigned to receive analgesia with either meperidine 0.5 mg/kg intravenously (group 1, n=24) or physostigmine 10 micrograms/kg intravenously, followed 5 minutes later by meperidine 0.5 mg/kg intravenously (group 2; n=20). The patients were assessed with regard to oxygen saturation, hemodynamic changes, pain perception and sedation scores, readiness to go home, and adverse effects.

RESULTS

The group 1 patients' oxygen saturations consistently fell, both during the procedure and in the recovery period; in group 2, oxygen saturations remained stable throughout the procedure and recovery period (95.88%+/-0.99 vs. 98.15+/-0.99, P<0.001). Patients in group 2 reported lower pain perception scores during the procedure (measured using a visual analog scale) than patients in group 1 (1.46+/-0.31 vs. 1.75+/-0.41; F1,42=6.484, P<0.015) and were less sedated during recovery (F1,41=6.56, P<0.015). No significant differences were found between the two groups with regard to heart rate or arterial blood pressure. All patients in group 2 were ready to go home after 25 minutes in the recovery area; three patients in group 1 were not ready to leave at 25 minutes and left the facility after 60 minutes. Four patients suffered from minor side effects of physostigmine (sweating and nausea).

CONCLUSIONS

Combining physostigmine with meperidine as preparatory treatment for patients undergoing colonoscopy prevents respiratory depression, improves analgesia, and shortens recovery time, with only mild side effects.

Comparison of the Flexiblade levering laryngoscope with the English Macintosh laryngoscope in patients with a poor laryngoscopic view

The effectiveness of two laryngoscopes, the English Macintosh and the Flexiblade (a levering laryngoscope), were compared in a clinical setting. An investigation was carried out in 100 patients admitted for surgery under general anaesthesia, to compare intubation with the Flexiblade or the Macintosh laryngoscope. The patients had two anatomical characteristics that may predict difficult intubation - Mallampati score II and III, and a thyromental distance </= 6.5 cm. Patients were randomly allocated to receive intubation with one of the laryngoscopes. The laryngeal view obtained during laryngoscopy, the intubation time, and the need for optimization manoeuvres and assistance required were compared in the two groups. The correlation between intubation time and anatomical characteristics was determined. Only 49 patients had a poor laryngeal view during initial laryngoscopy and required additional facilitating manoeuvres. In these patients, successful intubation time (in seconds) using the Flexiblade was significantly shorter than using the Macintosh laryngoscope (median 14.3 s, IQR 12.0-18.4 s [corrected] vs. median 20.8 s, IQR 14.9-25.5 s (U = 165, [corrected] p , 0.01). Assistance and additional manoeuvres were required significantly less frequently in the Flexiblade group (21%) compared to Macintosh group (67%) (p < 0.01). No correlation was found between intubation time, Mallampati scores, thyromental distance, or body weight. We concluded that in patients with an initial poor laryngoscopic view, the Flexiblade may enable faster and easier tracheal intubation.

Design evaluation of commonly used rigid and levering laryngoscope blades

BACKGROUND

The shape of a laryngoscope blade affects the exposition of the larynx. This study evaluates and compares some rigid and levering blade designs based on previous investigative X-ray laryngoscopic studies.

METHODS

Five rigid laryngoscope blades (Miller #3, Standard Macintosh #3, Classical Macintosh #4 and English-Macintosh #3 and #4) and two levering laryngoscope blades (McCoy in neutral and maximally elevated positions and Flexiblade in three basic positions: straight, neutral, and maximally curved) were evaluated. This study assesses two parameters derived from the depth of insertion: the eye line deviation from the ideal straight view line to the vocal cords, and the space occupied by the blade behind the mandible, which affects the contact of the blade tip with the base of the tongue.

RESULTS

The best results on larynx exposition were produced by the English-Macintosh #4 at all insertion depths between 5 and 14 cm. It surpassed the Classical Macintosh #4 and both the English and Standard Macintosh #3. Although the Miller and the Flexiblade in a straight position afford a nearly ideal view line, both blades reduce the space reserved for the tongue behind the mandible. The McCoy with its tip maximally elevated provides limited view, while activation of the Flexiblade provides various ranges of larynx exposition.

CONCLUSION

The difference in shape and design of Macintosh blades affects their performance. The distal portion of a large-sized curved blade is more effective than the full length of a shorter blade. The #4 English Macintosh is a better choice for routine clinical use. The Flexiblade performs as a multiblade device and can therefore be used for both routine and difficult intubations.

Immune response in asymptomatic smokers

BACKGROUND

It has been demonstrated that cigarette smoking affects the immune system. Impairment of alveolar mononuclear cell function, described previously, may contribute to the higher rate of postoperative respiratory infections. However, increased susceptibility of smokers to infections of other origin (e.g. wound-related) implies that tobacco effect is not restricted to the respiratory immune competent cells. The present study was designed to investigate the systemic effect of tobacco smoking as it exerted on blood-derived immune cells. We measured systemic cytotoxic activity of natural killer cells, production of pro- and anti-inflammatory cytokines by blood mononuclear cells and their proliferation in response to mitogens. To minimize the immunosuppressive effect of other smoke-related factors, the smokers with chronic obstructive pulmonary disease (COPD) were excluded from this study.

METHODS

Peripheral blood mononuclear cells (PBMC) from 24 chronic asymptomatic smokers, and 28 controls, age and gender matched, were isolated and incubated in vitro with lipopolysaccharide (LPS) or phytohemagglutinin (PHA) to induce secretion of IL-1beta, IL-1ra, IL-6, IL-10, TNFalpha and IL-2, respectively, from mononuclear cells. The level of the cytokines in the supernatants was measured using ELISA kits. The proliferative response to the mitogens PHA and concanavalin A (ConA) was evaluated by 3H-thymidine incorporation and NK cell cytotoxicity by 51Cr release assay.

RESULTS

Mononuclear cells from smokers showed increased production of the pro-inflammatory cytokines IL-1beta, IL-6 and TNFalpha and enhanced proliferative response to mitogens as compared to non-smoking population. The secretion of IL-2 and the anti-inflammatory cytokines IL-1ra and IL-10 was similar in both groups. NK cell cytotoxic activity was suppressed in the smokers.

CONCLUSION

Cigarette smokers without chronic obstructive pulmonary disease (COPD) exhibit impaired NK cytotoxic activity in peripheral blood and unbalanced systemic production of pro- and anti-inflammatory cytokines. These changes may serve as predisposing factors for respiratory and systemic infections in the postoperative period and should alert an anesthetist during perioperative management.

Effects of mild perioperative hypothermia on cellular immune responses

BACKGROUND

Unintentional perioperative hypothermia is a common complication of anesthesia and surgery associated with adverse effects on several systems, including impaired wound healing and more frequent wound infections. Mild hypothermia affects various immune functions. In the current study, the authors sought to determine whether immune alterations in the perioperative period might be induced, at least in part, by impaired thermoregulation during this period.

METHODS

Sixty patients undergoing abdominal surgery were randomly assigned to two thermal care groups: routine care or forced-air warming. The patients' anesthetic care was standardized. Venous blood samples were collected 90 min before induction of anesthesia and immediately, 24 h, and 48 h after surgery. White cells were separated and frozen. Peripheral blood mononuclear cells were used to test cytokine production (interleukins [IL] -1beta, -2, and -6; tumor necrosis factor-alpha [TNF-alpha]), mitogens-induced proliferation, and natural killer NK cell cytotoxicity. Plasma cortisol levels were also determined.

RESULTS

Patients in the normothermia group maintained normal body core temperature, whereas temperature decreased by approximately 1 degree C in the hypothermia group. Mitogenic responses were suppressed in cells from patients in the hypothermia but not in the normothermia group 24 and 48 h after surgery. Proinflammatory cytokine (IL-1beta, IL-6, TNF-alpha) production increased in both groups, although the production of IL-1beta was significantly higher in the normothermia group 24 h after surgery. Production of IL-2 was suppressed in the hypothermia but not in the normothermia group at 24 h.

CONCLUSIONS

Mild perioperative hypothermia suppressed mitogen-induced activation of lymphocytes and reduced the production of certain cytokines, IL-1beta and IL-2, and in this way may contribute to the immune alterations observed in the perioperative period.

Bedside test for diagnosis of oedema fluid after extradural anaesthesia

PURPOSE

To consider and differentiate oedema fluid from other fluids in the performance of epidural block.

CLINICAL FEATURES

A patient underwent placement of an epidural catheter for vaginal delivery of twins. Following a loss of resistance technique using air a small amount of fluid was aspirated through the needle and subsequently through the epidural catheter. The epidural block and delivery followed uneventfully. After delivery oedema fluid oozed from the puncture site for a number of days. Laboratory investigation revealed that this fluid was of oedematous origin. Bedside determination of alkaline pH by Combur 10 Test M urine stick appeared to be a simple and useful test for distinguishing the oedema fluid from fluids of other possible sources.

CONCLUSION

When performing an epidural blockade the return of fluid may be due to oedematous fluid. Differentiation of the pH by a simple bedside test can aid in the differential diagnosis and prevent unnecessary additional attempts at needle repositioning.

Systemic physostigmine increases the antinociceptive effect of spinal morphine

In this study we evaluated the antinociceptive effect of concurrent intrathecal (i.t.) and subcutaneous (s.c.) administration of morphine and physostigmine, respectively. The experiments were performed on male Wistar rats. Intrathecal administration of morphine was performed through a catheter implanted in the subarachnoid space. The 'tail-immersion' test was used to measure animals' responses to evoked nociceptive stimuli. Interaction of drugs was analyzed using a dose addition model. Both i.t. (1-5 microg) administration of morphine and s.c. (50-250 microg/kg) administration of physostigmine increased the latencies of nociceptive responses in a dose-dependent manner. Two micrograms of i.t. morphine and 100 microg/kg of s.c. physostigmine demonstrated 31.6 +/- 10.6 and 34.2 +/- 11.4 percentage of maximal possible effect (%MPE), respectively. Simultaneous administration of 1 microg of i.t. morphine and 50 microg/kg of s.c. physostigmine produced a %MPE equal to 84.8 +/- 16.9. Thus, combined administration of 1 microg i.t. morphine and 50 microg/kg s.c. physostigmine resulted in a strong, highly significant antinociceptive effect. This effect was much higher than the effect expected if both drugs acted in an additive manner. Supra-additive interaction observed in this study might be a result of simultaneous activation of different neurotransmitter systems involved in nociceptive processing at the spinal as well as at the supraspinal level of the CNS.