Inhaled nitric oxide potentiates actions of adenosine but not of sodium nitroprusside in experimental pulmonary hypertension.

Inhaled nitric oxide (NO), a selective pulmonary vasodilator, increases intracellular cyclic guanosine monophosphate. In contrast, adenosine, another selective pulmonary vasodilator, increases intracellular cyclic adenosine monophosphate. There has been only limited study on effects of inhaled NO combined with other pulmonary vasodilators. The current study examined the hypothesis that inhaled NO would potentiate in vivo pulmonary vasodilator effects of adenosine, but not those of sodium nitroprusside (SNP). Like inhaled NO, SNP acts via cyclic guanosine monophosphate. Rabbits were anesthetized and mechanically ventilated. The NO synthesis inhibitor NG-nitro-L-arginine methyl ester was administered. U46619, a thromboxane A2 mimetic, was infused to produce pulmonary hypertension. Rabbits then received either SNP at doses of 0.5, 1, 2, 4, 8, 16, and 32 microg/kg/min or adenosine at doses of 12.5, 25, 50, 100, 150, and 300 microg/kg/min. Hemodynamic measurements were obtained with or without inhaled NO (40 ppm) at each dose of SNP or adenosine. During U46619-induced pulmonary hypertension, inhaled NO decreased pulmonary artery pressure and pulmonary vascular resistance. Adenosine and SNP produced dose-related decreases in pulmonary artery pressure and pulmonary vascular resistance and increases in cardiac output. Inhaled NO decreased pulmonary artery pressure and pulmonary vascular resistance at all doses of adenosine, but had no significant pulmonary vasodilator effects at doses of SNP >0.5 microg/kg/min. We conclude that inhaled NO does not produce additional pulmonary vasodilation over that achieved at higher doses of SNP, but does produce additional vasodilation when combined with a vasodilator having different mechanisms of action. Since both inhaled NO and adenosine produce selective pulmonary vasodilation, such combination therapy may be effective in patients with pulmonary hypertension.

Inhibition of endogenous nitric oxide synthesis potentiates the effects of sodium nitroprusside but not of adenosine in experimental pulmonary hypertension.

This study examined the systemic and pulmonary vasodilator effects of sodium nitroprusside (SNP) and adenosine during experimental pulmonary hypertension with and without inhibition of endogenous NO synthesis. Male New Zealand White rabbits were anesthetized and mechanically ventilated. The NO synthesis inhibitor NG-nitro-L-arginine methyl ester (L-NAME) was administered to 15 of the 28 rabbits. Pulmonary hypertension was then produced in all rabbits by U46619, a thromboxane A2 mimetic. SNP was infused in 14 rabbits (7 L-NAME, 7 control) at doses of 0.5-20 microg/kg/min; adenosine was infused in the other 14 rabbits (8 L- NAME, 6 control) at doses of 12.5-300 microg/kg/min. The U46619 dose required to produce pulmonary hypertension was significantly lower in the L-NAME group. SNP dose-dependently decreased pulmonary (Ppa) and systemic (Psa) artery pressures and systemic vascular resistance (SVR). Both Ppa and Psa were decreased more with SNP in the L-NAME than in the no L-NAME group. The SNP ED50 for the decrease in PVR was almost threefold lower in the L-NAME group. Adenosine dose-dependently decreased Ppa, Psa, PVR and SVR. The adenosine ED50 for the decreases in PVR and SVR were similar in the L-NAME group and the control group. We conclude that inhibition of endogenous NO synthesis shifts the dose-response curves for both the pulmonary and systemic vasodilator effects to the left for the nitrovasodilator SNP but not for the non-nitrovasodilator adenosine.

Hypoxemia during outpatient gastrointestinal endoscopy: the effects of sedation and supplemental oxygen.

STUDY OBJECTIVES: To compare the effects on oxygen saturation as measured by pulse oximetry (SpO2) and ECG changes of endoscopy alone, sedation followed by endoscopy, and sedation followed by endoscopy with supplemental oxygen (O2) during upper gastrointestinal (GI) endoscopy. STUDY DESIGN: Randomized trial. SETTING: Outpatient gastroenterology clinic at a university medical center. PATIENTS: 58 healthy patients scheduled for outpatient upper GI endoscopy, with no clinical evidence of respiratory disease. INTERVENTIONS: Patients were randomly allocated to three groups: Group 1 received no benzodiazepines before endoscopy and breathed room air throughout (n = 18), Group 2 received midazolam intravenously (i.v.) before endoscopy and breathed room air throughout (n = 20), and Group 3 received i.v. midazolam and 2 L/min O2 through nasal cannulae during endoscopy (Group 3; n = 20). MEASUREMENTS AND MAIN RESULTS: Data collection, which included heart rate, cardiac rhythm, and SpO2 were recorded at seven intervals: baseline, topical anesthesia of the oropharynx, mouth gag insertion, endoscope insertion, biopsy, endoscope removal, and five minutes postendoscopy. In Group 2, mean SpO2 decreased after midazolam was administered and remained depressed during endoscopy (p < 0.05). After midazolam was given, Group 2 patients differed significantly from patients in Groups 1 and 3 (p < 0.05). CONCLUSIONS: The use of hypnotic doses of benzodiazepines is the primary factor responsible for the reduced oxygenation seen during endoscopy. Neither the presence of the endoscope alone nor the use of midazolam with supplemental O2 caused a decreased oxygenation. This study also suggests that the routine use of benzodiazepines is unnecessary when the endoscopy is of short duration, and the endoscopist employs good topicalization of the oropharynx. In patients who require sedation for endoscopy, O2 administration prevents hypoxemia.

Buccal prochlorperazine as an antiemetic for day care surgery.

This study compares the antiemetic effect of prochlorperazine in a buccal preparation with a control group as a preoperatively administered antiemetic. Fifty-two female day care patients undergoing gynaecological surgery or breast biopsy were studied. Patients were randomly allocated to two groups. Patients in group one received no antiemetic, while those in group two received 6mg buccal prochlorperazine one hour before surgery. Nausea was assessed with a visual nausea scoring system and interview similar to those used in previous series. Assessment times were before surgery and at one, four and 24 hours after surgery. Patient demographics and type of surgery were similar for the groups. The incidence of postoperative nausea and vomiting for the groups one and two was 57.7% and 15.4% respectively, p < 0.05. Most of the patients who experienced nausea in group one and two (86.7% and 50%) gave it a score less than five, indicating mild nausea. The majority of patients did not require treatment for postoperative nausea. The postoperative antiemetic and narcotic requirements were similar in the two groups. This study demonstrates that prochlorperazine at the dose used is effective in preventing postoperative nausea in the patient population studied.

Propofol sedation for outpatient upper gastrointestinal endoscopy: comparison with midazolam.

The objectives of this study were to assess midazolam and propofol as sedative agents for outpatient gastrointestinal endoscopy, with particular reference to recovery profile, amnesic effects, and haemodynamic state and oxygenation during the procedure. Forty consecutive patients were allocated randomly to two groups. Patients in group I (n = 19) received midazolam 81 (SEM 32) micrograms kg-1; those in group II (n = 21) received propofol 950 (400) micrograms kg-1. Both agents were administered as single injections to similar end-points of sedation. Psychomotor function was assessed using the digit symbol substitution test (DSST). Amnesia was measured with a visual memory test and subjective questionnaire. Patients in group I had a lower DSST score than those in group II (P less than 0.01), indicating a hangover effect from midazolam. Amnesia was similar in the two groups up to the time of removal of the endoscope. More patients in group II remembered removal of the endoscope (P less than 0.001). Oxygen desaturation from baseline was similar in both groups (P less than 0.01). An increase in heart rate and decrease in mean arterial pressure were noted in both groups. Propofol provided more rapid recovery compared with midazolam, but was associated with pain on injection, a short amnesia span, and reduced patient acceptance.

HELLP syndrome: a case report with guidelines for diagnosis and management.

A 25-yr-old patient with a twin pregnancy of 34 weeks gestation developed HELLP syndrome and required urgent delivery by Caesarean section. Before operation, a central venous catheter and urinary catheter were inserted, and fresh frozen plasma and platelets were administered to correct hypovolaemia and severe thrombocytopenia. This case demonstrates the critical condition of these patients before operation and that extensive preoperative preparation and invasive monitoring are necessary for successful management. The choice of anaesthetic is governed by the presence of liver and renal dysfunction and severe thrombocytopenia.

Reflex spinal cord activity as a cause of a delay in the diagnosis of brain death.

A 56 year old woman was admitted to our hospital following a fall in which she sustained an acute subdural haematoma. She failed to respond to treatment despite surgical intervention and active brain protection measures. During brain stem function testing on two occasions she demonstrated movement in the distribution of the accessory (XI) cranial nerve despite angiographically confirmed absence of a cerebral circulation. This delayed decision making and organ donation. We report this case in order to highlight this problem which may be encountered during brain stem function testing.

An unusual complication of brachial plexus sheath cannulation.

A 20-gauge cannula placed via an interscalene approach in the left brachial plexus sheath of a healthy 18-yr-old male was used inadvertently for injection of 20 ml of antibiotic solution, despite clear labelling of the cannula and painful protest from the patient. The patient suffered no neurological sequelae. The treatment, possible causes and steps to avoid similar incidents are described.