FOETAL AND MATERNAL PLASMA LEVELS OF MEPIVACAINE AND FOETAL ACID-BASE BALANCE AND HEART RATE AFTER PARACERVICAL BLOCK DURING LABOUR

Mepivacaine concentrations were estimated simultaneously inmaternal venous plasma and foetal capillary plasma in elevenobstetrical cases after paracervical blockade (PCB) with 200–400mg of mepivacaine without adrenaline. 400 mg of mepivacainefor PCB produced a clearly higher maternal mepivacaine levelthan 200 mg of mepivacaine. Foetal mepivacaine levels paralleledor were lower than the corresponding maternal levels in allexcept one case immediately after PCB. The possible causes ofa higher foetal than maternal mepivacaine level after PCB arediscussed. A significantly greater mean pH decrease (–0.115pH units) was found in the group with foetal bradycardia observedimmediately after PCB than in the group with no bradycardia(–0.040 pH units). A relationship between the fall infoetal pH and the foetal plasma concentration of mepivacaineafter PCB was suggested by the relatively high correlation coefficient(r= –0.65) between the mavimai values of these two parameters.     

THE MATERNAL PLASMA LEVELS AND PLACENTAL TRANSFER OF BUPIVACAINE FOLLOWING EPIDURAL ANALGESIA

The maternal plasma levels of bupivacaine following epiduraladministration of 0.5 per cent solution with 1/200,000 adrenalinewere determined in twelve patients in labour. After 10 ml (50mg) peak concentrations occurred 15–30 min later and rangedfrom 0.22 µg/ml to 0.60 µg/ml. Plasma levels fellgradually with time after the peak until by 3 hours after injectionthey were all well below 0.2 µg/ml. Maternal and umbilicalplasma levels of bupivacaine were determined at delivery. Theratio of the foetal to maternal levels varied from 0.14 to 0.86.The highest foetal plasma level obtained in the series was 0.25µg/ml and the highest maternal level was 0.68 µg/ml.This value was reached after three 10-ml injections of 0.5 percent bupivacaine with 1/200,000 adrenaline. The 1-min Apgarscores ranged from 7 to 10.     

RESPIRATORY AND METABOLIC ACID-BASE CHANGES DURING CARDIOPULMONARY BYPASS IN MAN

Twenty-two patients undergoing open-heart surgery with cardiopulmonarybypass have been studied to define acid-base changes associatedwith anaesthesia, bypass, hypothermia and recovery. The maintenanceof normal pH during the operation, or the inclusion of a periodof normothermia before cooling, had no measurable effect onthe postoperative acid-base state or clinical course as comparedwith the usual routine of bypass in respiratory alkalosis andwith immediate cooling. Lactate and pyruvate increased slowlythroughout anaesthesia and bypass to combined levels not exceeding5 m.equiv/1. Rapid metabolic acid-base shifts of at least equalmagnitude, not due to lactic or pyruvic acids, were apparentlyassociated mainly with temperature changes. Acidosis has notbeen found severe enough to need routine administration of bicarbonateat any stage.     

THE EFFECT OF LOW MOLECULAR WEIGHT DEXTRAN AND HAEMODILUTION ON ACID-BASE BALANCE AND ACTATE AND PYRUVATE LEVELS DURING CARDIOPULMONARY BYPASS

Acid-base changes and lactate and pyruvate concentrations weremeasured in patients undergoing open-heart surgery under totalcardiopulmonary bypass with a Melrose-NEP heart-lung machine.Moderate hypothermia was used. There were no significant differencesin base loss or lactate and pyruvate concentrations betweenperfusions conducted with a whole blood prime and those in whichthe blood was diluted with a low molecular weight dextran withor without the addition of dextrose-saline. The difficultiesin interpretation of measurements of excess lactate are discussed. ^* Present address: University of Alexandria, Egypt.     

ACID-BASE BALANCE AND NEOSTIGMINE ANTAGONISM OF PANCURONIUM NEUROMUSCULAR BLOCKADE

In 40 cats anaesthetized with chloralose and urethane, pancuroniumwas infused i.v. at a constant rate to produce and maintain90% depression of twitch tension of the anterior tibialis musclefollowing supramaximal stimulation of the peroneal nerve. Neitherrespiratory alkalosis nor metabolic acidosis influenced theinfusion rate required to produce 90% depression of twitch tensionor antagonism of this depression by neostigmine. Respiratoryacidosis (pH 7.15; Pa_CO2, 10 kPa) did not alter the requiredinfusion rate but did prevent complete antagonism by neostigmine.Metabolic alkalosis (pH 7.65; Pa^CO2, 4.8 kPa) reduced both therequired infusion rate and prevented complete restoration oftwitch tension by neostigmine. The duration of neostigmine antagonismwas shortened by metabolic alkalosis. We conclude that respiratoryacidosis and metabolic alkalosis prevent antagonism of pancuroniumby neostigmine.     

CORRELATION BETWEEN MATERNAL AND FOETAL Po2 AND Pco2 DURING CAESAREAN SECTION

Fifteen cases of elective Caesarean section at term were studiedunder general anaesthesia. Maternal carbon dioxide tensionswere controlled by adjusting the minute ventilation volume;Pa_co2 ranged from 13 to 80 mm Hg. Maternal oxygen tensions werecontrolled by changing the inspired oxygen concentrations (20,33.3, 50, or 100 per cent); Pa_o2 ranged from 78 to 500 mm Hg.Umbilical vein Po₂ and Pco₂ of the newborn varied accordingto the maternal level. Foetal Pco₂ was always higher than maternalPa_oo2; the mean maternal-foetal gradient was 11.3 mm Hg (SD4.7). Foetal Po₂ was positively correlated with maternal Pa_o2within the range 78 to 200–300 mm Hg, but was not correlatedwith further elevation of maternal Pa_o2 from 200 to 500 mm Hg.This might be attributed to the shape of Hb_o2 dissociation curve.     

ACID-BASE AND URINE pH CHANGES FOLLOWING MITRAL VALVOTOMY

In twelve patients undergoing routine transventricular mitralvalvotomy, mean base excess on the 1st and 3rd postoperativedays was significantly higher than the mean pre-operative level.The mean urine pH 1 hour after operation and on the 1st post-operativeday was significantly lower than the mean pre-operative level.     

ACID-BASE CHANGES IN ARTERIAL BLOOD ASSOCIATED WITH SPONTANEOUS AND CONTROLLED VENTILATION DURING ANAESTHESIA

Arterial pH, Pco₂ and whole blood standard bicarbonate weremeasured in surgical patients before, during, and after spontaneousor controlled pulmonary ventilation with nitrous oxide, oxygenand halothane. Relative increases in arterial Pco were accompaniedby significant reductions in standard bicarbonate, indicativeof a non-respiratory acid aemia. This effect may be attributablein part to differences between the log Pco₂ equilibration linesfor blood and for the whole organism. Small reductions in standardbicarbonate occurred over several hours of pulmonary overventilationin neurosurgical patients during induced hypothermia, and inthe early postoperative period.     

CHANGES IN FIBRINOGEN LEVELS IN PATIENTS UNDERGOING OPEN AND LAPAROSCOPIC NISSEN FUNDOPLICATION

Background: Venous thromboembolic complications may be more common after laparoscopic surgical techniques, possibly due to changes in venous flow and blood coagulability. Methods: This study assessed fibrinogen, cross-linked fibrin degradation products (D-dimer), prothrombin international normalized ratio (INR), activated partial thromboplastin time (APTT) and platelets, during and after both open and laparoscopic Nissen fundoplication to determine whether coagulability is increased by the laparoscopic approach. Results: Seven patients underwent open and thirteen underwent laparoscopic Nissen fundoplication. Fibrinogen levels following open fundoplication fell from 2.8 ± 0.3 g/L pre-operatively to 2.0 ± 0.3 g/L following skin incision, and then increased to 4.1 ± 0.4 g/L on the first postoperative day. Similar changes in fibrinogen occurred following laparoscopic fundoplication (2.7 ± 0.2, 2.5 ± 0.2 and 3.8 ± 0.4 g/L, respectively). No significant changes in the other coagulation indices were observed. Conclusions: These results demonstrate hypercoagulability on the first postoperative day, irrespective of the operative technique. No differences between the results following laparoscopic and open fundoplication were demonstrated.     

THE EFFECT OF TRICHLOROETHYLENE-NITROUS OXIDE ANAESTHESIA ON ACID-BASE BALANCE IN MAN

Thirty-five patients undergoing major operations under trichloroethyleneand nitrous oxide anaesthesia with muscle relaxants and withaugumented respiration in a Magill System (Mapleson A) or non-rebreathingsystem were monitored with regard to acid-base balance and ventilation.A trend to acidosis occurred with the Mapleson A system, particularlyin those in the prone position. A mild respiratory alkalosisoccurred when the non-rebreathing system was used. Acid-basebalance reverted to the pre-operative state early in the recoveryperiod and blood pressure, pulse and cardiac rhythm remainedrelatively stable throughout. This study indicates that trichloroethylenecan be a suitable anaesthetic for major surgery provided thatthe criteria enumerated in this report are fulfilled.     

ARTERIAL OXYGEN TENSIONS AND ACID-BASE CHANGES DURING ETHER-AIR ANAESTHESIA

PaO₂ and changes in acid-base parameters were measured in a series of patients anaesthetized with an ether-air mixture. Patients were divided into three groups: (1) spontaneous respiration, (2) manual ventilation and (3) mechanical ventilation. PaO₂ in all patients except one were maintained close to pre-operative values during and after operation. Changes in pH and arterial carbon dioxide tension were due to changes in ventilation, not to alterations of acid-base balance. The present study confirms previous observations, viz. that in the absence of severe respiratory or circulatory disturbance, air as a carrier gas for ether results in adequate arterial oxygenation.

ZUSAMMENFASSUNG

Bei einer Reihe von Patienten, die mit einem Äther-Luft-Gemisch narkotisiert worden waren, wurden PaO₂ und Veränderungen des Säure-Basen-Status gemessen. Die Patienten wurden in drei Gruppen unterteilt: 1. Spontanatmung, 2. manuelle Beatmung, 3. mechanische Beatmung. Mit Ausnahme eines Patienten konnte bei alien das PaO₂ wahrend und nach der Operation auf an-nähernd praeoperativen Werten gehalten werden. Die Veränderungen des pH und der arteriellen C O₂ -Spannung waren ventilationsbedingt und nicht die Folge von Saure-Basen-Verschiebungen. Diese Untersuchung bestätigt frühere Beobachtungen, dass nämlich beim Fehlen schwerer Storungen der Atmung und des Kreislaufes Luft als Trägergas für Äther ausreichende arterielle Sauer-stoffwerte ergibt.     

EFFECTS OF ENFLURANE AND ISOFLURANE IN AIR-OXYGEN ON CHANGES IN THERMAL BALANCE DURING AND AFTER SURGERY

The temperatures in the aural canal (core), skeletal muscleand skin surface were measured during anaesthesia and surgeryin 32 healthy females undergoing total abdominal hysterectomyand for 4 h after operation. The patients were allocated randomlyto one of four groups according to the end-tidal concentrationof volatile anaesthetic: 1 MAC isoflurane, 1 MAC enflurane,1.8 MAC isoflurane and 1.8 MAC enflurane. The lungs were ventilatedwith an air-oxygen mixture. Neuromuscular block was producedwith pancuronium. Room temperature and i.v. fluid administrationwere standardized. Aural canal, muscle and mean skin temperaturesdecreased significantly in all groups during surgery (P <0.001). The decrease in core and muscle temperatures, and meanbody heat was significantly greater in the 1.8 MAC groups thanin the 1 MAC groups for both volatile agents (P < 0.001).However, there was a significantly greater decrease in coretemperature and mean body heat in the isoflurane compared withthe enflurane group (P < 0.026). Body temperature returnedto preoperative values during the recovery period. There wasa significantly greater rate of rewarming during the first 1h of recovery in the 1.8 MAC groups compared with the 1 MACequivalent (P < 0.001), and this was independent of the volatileagent used. The present results are compared with those reportedpreviously in which nitrous oxide was added to the volatileagents. The decrease in body temperature depends upon the concentrationof vapour used. However, it appears that isoflurane, withoutnitrous oxide, caused greater loss of body heat than enflurane.     

EFFECT OF FLUROXENE (FLUOROMAR®) ON ACID-BASE BALANCE IN MAN

Es wurden Serienblutabnahmen ohne Luftzutritt bei 30 Patienten vorgenommen, bei denen grössere abdominelle Operationen in genau präzisierter Flurexene-Stickoxydul-Narkose durchgeführt wurden. Das pH, PCO₂ und PO₂ wurden in jeder Blutprobe mit Hilfe des ←Epsco-Medical-Blood-Parameter-Analyser→ gemessen, einer kompakten Einheit mit konstantem Temperaturbad, pH-Messer, Sauerstoffspannungselektrode und Kohlesäurespannungselektrode, und somit anwendbar für rasche Serienblutanalysen. Die Ergebnisse dieser Messungen zeigen, dass Flurexene-Anaesthesie keine Störungen im Säure-Basen-Gleichgewicht während grosser chirurgischer Operationen verursacht.
Flurexene besitzt obendrein die für den klinischen Gebrauch wesentlichen Merkmale eines zufriedenstellenden Narkotikums. Der einzige Nachteil, der es nicht für jede Art der Anaesthesie verwendbar macht, ist die Tatsache, dass es in der Nähe der für mittlere Narkosetiefe erforderlichen Konzentrationsbereiche entflammbar ist. Doch davon abgesehen scheint es für den Allgemeingebrauch wertvoll zu sein.