- The commonest structure that can be injured by the laparoscope is the distended stomach. So pass a nasogastric tube and aspirate the stomach contents especially if the induction has involved prolonged bag and mask ventilation.
- Regurgitation of gastric contents can happen
- Pulmonary oedema from fluid infusions and the head-down position
- Insufflation is the most hazardous phase; A demonstrable gas embolism can occur in 1 out of 2000 patients; so watch for high insufflating pressures and low flow. Signs of gas embolism include arrhythmia, hypotension, cyanosis and cardiac arrest. The safest technique is to use CO2 for the pneumoperitoneum rather than N2O, because CO2 is more soluble and if an embolism occurs, it will resolve faster. Watch the indicators on the insufflating machine continuously during inflation. Pressure over 3 kPa or total volume insufflated exceeding 5 litres are hazardous. Caval compression and reduced venous return, with lowered cardiac output, may be a consequence of intra-abdominal pressure exceeding 4 kPa.
- The pressure effect of the insufflating gas will also splint the diaphragm and impede the mechanism of breathing.
- Avoid excessive head down tilt, and always be prepared for laparotomy.
- The end-tidal CO2 will rise during the course of a prolonged procedure and minute volume should be adjusted to compensate.
- Pneumothorax and surgical emphysema have been described, associated with prolonged surgery.
- Shoulder-tip pain, from diaphragmatic irritation, is a common postoperative problem.
Monthly Archives: September 2021
DIFFERENCES BETWEEN THE TYPES OF HYPOXIA
HYPOXIC HYPOXIA (e.g. High Altitude)
- PaO2 is reduced ( as FiO2 is low)
- So more extraction of O2: So PvO2 is reduced
- Based on the above formula, both arterial and venous oxygen content also will be reduced
ANAEMIC HYPOXIA (e.g. haemorhhage)
- PaO2 will be normal
- But arterial oxygen content will be reduced due to lower values of Hb, as per the above formula reducing the oxygen delivery to tissues and increasing the cardiac work
- So there will be more oxygen extraction leading to a low PvO2 and venous oxygen content.
STAGNANT HYPOXIA (e.g. Cardiogenic shock)
- PaO2 is normal
- PvO2 is also normal
- There is no reduction in the arterial and venous oxygen content too.
- However, circulatory dysfunction results in inadequate oxygen delivery to organs
HISTOTOXIC HYPOXIA (e.g. Cyanide poisoning)
- PaO2 is normal. Arterial oxygen content also will be normal.
- But cells are unable to utilise oxygen resulting in high venous saturations
Volume of Distribution
- Is the theoretical volume into which a drug must distributes to produce the measured plasma concentration
- Unit is mL
- It is measured as Vd= Dose / Co, where Co is the initial plasma concentration from a concentration-time graph
- Lipid solubility, plasma protein binding, tissue protein binding, regional blood flow etc determine the Vd
The Lay Medical Man 